Practice EssentialsPneumothorax is defined as the presence of air or gas in the pleural cavity (ie, the potential space between the visceral and parietal pleura of the lung), which can impair oxygenation and/or ventilation. The clinical results are dependent on the degree of collapse of the lung on the affected side. If the pneumothorax is significant, it can cause a shift of the mediastinum and compromise hemodynamic stability. Air can enter the intrapleural space through a communication from the chest wall (ie, trauma) or through the lung parenchyma across the visceral pleura. See the image below.Radiograph of a patient with a complete right-sided pneumothorax due to a stab wound. Signs and symptomsThe presentation of patients with pneumothorax varies depending on the following types of pneumothorax and ranges from completely asymptomatic to life-threatening respiratory distress: Spontaneous pneumothorax: No clinical signs or symptoms in primary spontaneous pneumothorax until a bleb ruptures and causes pneumothorax; typically, the result is acute onset of chest pain and shortness of breath, particularly with secondary spontaneous pneumothoraces Iatrogenic pneumothorax: Symptoms similar to those of spontaneous pneumothorax, depending on patients age, presence of underlying lung disease, and extent of pneumothorax Tension pneumothorax: Hypotension, hypoxia, chest pain, dyspnea Catamenial pneumothorax: Women aged 30-40 years with onset of symptoms within 48 hours of menstruation, right-sided pneumothorax, and recurrence Pneumomediastinum: Must be differentiated from spontaneous pneumothorax; patients may or may not have symptoms of chest pain, persistent cough, sore throat, dysphagia, shortness of breath, or nausea/vomiting See Clinical Presentation for more detail.DiagnosisHistory and physical examination remain the keys to making the diagnosis of pneumothorax. Examination of patients with this condition may reveal diaphoresis and cyanosis (in the case of tension pneumothorax). Affected patients may also reveal altered mental status changes, including decreased alertness and/or consciousness (a rare finding). Findings on lung auscultation vary depending on the extent of the pneumothorax. Respiratory findings may include the following: Respiratory distress (considered a universal finding) or respiratory arrest Tachypnea (or bradypnea as a preterminal event) Asymmetric lung expansion: Mediastinal and tracheal shift to contralateral side (large tension pneumothorax) Distant or absent breath sounds: Unilaterally decreased/absent lung sounds common, but decreased air entry may be absent even in advanced state of pneumothorax Minimal lung sounds transmitted from unaffected hemithorax with auscultation at midaxillary line Hyperresonance on percussion: Rare finding; may be absent even in an advanced state Decreased tactile fremitus Adventitious lung sounds: Ipsilateral crackles, wheezes Cardiovascular findings may include the following: Tachycardia: Most common finding; if heart rate is faster than 135 beats/min, tension pneumothorax likely Pulsus paradoxus Hypotension: Inconsistently present finding; although typically considered a key sign of tension pneumothorax, hypotension can be delayed until its appearance immediately precedes cardiovascular collapse Jugular venous distention: Generally seen in tension pneumothorax; may be absent if hypotension is severe Cardiac apical displacement: Rare finding Common findings among the types of pneumothoraces include the following: Spontaneous and iatrogenic pneumothorax: Tachycardia most common finding; tachypnea and hypoxia may be present Tension pneumothorax: Variable findings; respiratory distress and chest pain; tachycardia; ipsilateral air entry on auscultation; breath sounds absent on affected hemithorax; trachea may deviate from affected side; thorax may be hyperresonant; jugular venous distention and/or abdominal distention may be present Pneumomediastinum: Variable or absent findings; subcutaneous emphysema is the most consistent sign; Hamman signa precordial crunching noise synchronous with the heartbeat and often accentuated during expirationhas a variable rate of occurrence, with one series reporting 10% Lab and imaging studiesAlthough laboratory and imaging studies help determine a diagnosis, tension pneumothorax primarily is a clinical diagnosis based on patient presentation. Suspicion of tension pneumothorax, especially in late stages, mandates immediate treatment and does not require potentially prolonged diagnostic studies. Arterial blood gas (ABG) studies measure the degrees of acidemia, hypercarbia, and hypoxemia, the occurrence of which depends on the extent of cardiopulmonary compromise at the time of collection. ABG analysis does not replace physical diagnosis, nor should treatment be delayed while awaiting results if symptomatic pneumothorax is suspected. However, ABG analysis may be useful in evaluating hypoxia and hypercarbia and respiratory acidosis. When pneumothorax is suspected, confirmation by chest radiography affords additional information beyond confirmation, such as the extent of pneumothorax, potential causes, a baseline study from which to go forward, and assistance with the therapeutic plan. The following radiologic studies may be used to evaluate suspected pneumothorax: Chest radiography: Anteroposterior and/or lateral decubitus films Contrast-enhanced esophagography: If emesis/retching is the precipitating event Chest computed tomography scanning: Most reliable imaging study for diagnosis of pneumothorax but not recommended for routine use in pneumothorax Chest ultrasonography See Workup for more detail.ManagementAlthough there is general agreement on the management of pneumothorax, a full consensus about management of initial or recurrent pneumothorax does not exist. Rather, many clinicians use a risk stratification framework as well as other approaches for choosing among options to restore lung volume and an air-free pleural space and to prevent recurrences.[1] The range of medical therapeutic options for pneumothorax includes the following: Watchful waiting, with or without supplemental oxygen Simple aspiration Tube drainage, with or without medical pleurodesis SurgeryIf the patient has had repeated episodes of pneumothorax or if the lung remains unexpanded after 5 days with a chest tube in place, operative therapy such as the following may be necessary: Thoracoscopy: Video-assisted thoracoscopic surgery (VATS) Electrocautery: Pleurodesis or sclerotherapy Laser treatment Resection of blebs or pleura Open thoracotomy PharmacotherapyThe following medications may be used to aid in the management of patients with pneumothorax: Local anesthetics (eg, lidocaine hydrochloride) Opioid anesthetics (eg, fentanyl citrate, morphine) Benzodiazepines (eg, midazolam, lorazepam) Antibiotics (eg, doxycycline, cefazolin) Background Pneumothorax is defined as the presence of air or gas in the pleural cavity (ie, the potential space between the visceral and parietal pleura of the lung). The clinical results are dependent on the degree of collapse of the lung on the affected side. Pneumothorax can impair oxygenation and/or ventilation. If the pneumothorax is significant, it can cause a shift of the mediastinum and compromise hemodynamic stability. Air can enter the intrapleural space through a communication from the chest wall (ie, trauma) or through the lung parenchyma across the visceral pleura. Among the topics this article will discuss are several areas of new information in the medical literature: (1) studies comparing aspiration and tube drainage for treatment of primary spontaneous pneumothorax, (2) long-term follow-up of surgical treatment of pneumothorax, (3) assessment of the impact of pleurodesis on transplantation outcomes in patients with lymphangiomyomatosis, (4) demonstrated utility of ultrasonography in the bedside diagnosis of iatrogenic pneumothorax, and (5) inability of ultrasonography to distinguish between intrapulmonary bullae and pneumothorax. See also Restoring an Air-Free Pleural Space in Pneumothorax. Primary and secondary spontaneous pneumothorax Spontaneous pneumothorax is a commonly encountered problem with approaches to treatment that vary from observation to aggressive intervention. Primary spontaneous pneumothorax (PSP) occurs in people without underlying lung disease and in the absence of an inciting event (see the images below).[2] In other words, air enters into the intrapleural space without preceding trauma and without an underlying history of clinical lung disease. However, many patients whose condition is labeled as primary spontaneous pneumothorax have subclinical lung disease, such as pleural blebs, that can be detected by CT scanning. Patients are typically aged 18-40 years, tall, thin, and, often, are smokers. Radiograph of a patient with a small spontaneous primary pneumothorax Close radiographic view of patient with a small spontaneous primary pneumothorax (same patient as from the previous image). Expiratory radiograph of a patient with a small spontaneous primary pneumothorax (same patient as in the previous images). Secondary spontaneous pneumothorax (SSP) occurs in people with a wide variety of parenchymal lung diseases.[2] These individuals have underlying pulmonary pathology that alters normal lung structure (see the image below). Air enters the pleural space via distended, damaged, or compromised alveoli. The presentation of these patients may include more serious clinical symptoms and sequelae due to comorbid conditions. Computed tomography scan demonstrating secondary spontaneous pneumothorax (SSP) from radiation/chemotherapy for lymphoma. Iatrogenic and traumatic pneumothorax Iatrogenic pneumothorax is a traumatic pneumothorax that results from injury to the pleura, with air introduced into the pleural space secondary to diagnostic or therapeutic medical intervention (see the following image). Half a century ago, iatrogenic pneumothorax was predominantly the result of deliberate injection of air into the pleural space for the treatment of tuberculosis (TB). The terminology evolved to the preference for "induced" or "artificial" pneumothorax to indicate pulmonary TB treatment, before arriving at the current classification. Pulmonary TB remains a significant cause of secondary pneumothorax. Radiograph of an older man who was admitted to the intensive care unit (ICU) postoperatively. Note the right-sided pneumothorax induced by the incorrectly positioned small-bowel feeding tube in the right-sided bronchial tree. Marked depression of the right hemidiaphragm is noted, and mediastinal shift is to the left side, suggestive of tension pneumothorax. The endotracheal tube is in a good position. Traumatic pneumothorax results from blunt trauma or penetrating trauma that disrupts the parietal or visceral pleura (see the images below). Management steps for traumatic pneumothoraces are similar to those for other, nontraumatic causes. If hemodynamic or respiratory status is compromised or an open (communicating to the atmosphere) and/or hemothorax are also present, tube thoracostomy is performed to evacuate air and allow re-expansion of the lung. There is a subset of traumatic pneumothoraces classified as occult; that is, they cannot be seen on chest radiographs but can be seen on CT scans. In general, these can be observed and treated if they become symptomatic. Illustration depicting multiple fractures of the left upper chest wall. The first rib is often fractured posteriorly (black arrows). If multiple rib fractures occur along the midlateral (red arrows) or anterior chest wall (blue arrows), a flail chest (dotted black lines) may result, which may result in pneumothorax. Radiograph of a patient with a complete right-sided pneumothorax due to a stab wound. Tension pneumothorax A tension pneumothorax is a life-threatening condition that develops when air is trapped in the pleural cavity under positive pressure, displacing mediastinal structures and compromising cardiopulmonary function. Prompt recognition of this condition is life saving, both outside the hospital and in a modern ICU. Because tension pneumothorax occurs infrequently and has a potentially devastating outcome, a high index of suspicion and knowledge of basic emergency thoracic decompression procedures are important for all healthcare personnel. Immediate decompression of the thorax is mandatory when tension pneumothorax is suspected. This should not be delayed for radiographic confirmation. Note the image below. This chest radiograph has 2 abnormalities: (1) tension pneumothorax and (2) potentially life-saving intervention delayed while waiting for x-ray results. Tension pneumothorax is a clinical diagnosis requiring emergent needle decompression, and therapy should never be delayed for x-ray confirmation. Pneumomediastinum Pneumomediastinum is the presence of gas in the mediastinal tissues occurring spontaneously or following procedures or trauma (see the following images). A pneumothorax may occur secondary to pneumomediastinum. Pneumomediastinum from barotrauma may result in tension pneumothorax and obstructive shock. This chest radiograph shows pneumomediastinum (radiolucency noted around the left heart border) in this patient who had a respiratory and circulatory arrest in the emergency department after experiencing multiple episodes of vomiting and a rigid abdomen. The patient was taken immediately to the operating room, where a large rupture of the esophagus was repaired. AnatomyThe inner surface of the thoracic cage (parietal pleura) is contiguous with the outer surface of the lung (visceral pleura); this space contains a small amount of lubricating fluid and is normally under negative pressure compared to the alveoli. Determinants of pleural pressure are the opposing recoil forces of the lung and chest wall.PathophysiologyThe underlying pathophysiology of pneumothorax is reviewed in this section.Spontaneous pneumothoraxSpontaneous pneumothorax in most patients occurs from the rupture of blebs and bullae. Although primary spontaneous pneumothorax (PSP) is defined as occurring in patients without underlying pulmonary disease, these patients have asymptomatic blebs and bullae detected on computed tomography scans or during thoracotomy. PSP is typically observed in tall, young people without parenchymal lung disease and is thought to be related to increased shear forces in the apex. Although PSP is associated with the presence of apical pleural blebs, the exact anatomic site of air leakage is often uncertain. Fluorescein-enhanced autofluorescence thoracoscopy (FEAT) is a novel method to examine the site of air leak in PSP. FEAT-positive lesions can be detected that appear normal when viewed under normal white-light thoracoscopy.[3] In normal respiration, the pleural space has a negative pressure. As the chest wall expands outward, the surface tension between the parietal and visceral pleura expands the lung outward. The lung tissue intrinsically has an elastic recoil, tending to collapse inwards. If the pleural space is invaded by gas from a ruptured bleb, the lung collapses until equilibrium is achieved or the rupture is sealed. As the pneumothorax enlarges, the lung becomes smaller. The main physiologic consequence of this process is a decrease in vital capacity and partial pressure of oxygen. Lung inflammation and oxidative stress are hypothesized to be important to the pathogenesis of PSP.[4] Current smokers, at increased risk for PSP, have increased numbers of inflammatory cells in the small airways. Bronchoalveolar lavage (BAL) studies in patients with PSP reveal that the degree of inflammation correlates with the extent of emphysematouslike changes (ELCs). One hypothesis is that ELCs result from degradation of lung tissue due to imbalances of enzymes and antioxidants released by innate immune cells.[5] In one study, erythrocyte superoxide dismutase activity was significantly lower and plasma malondialdehyde levels higher in patients with PSP than in normal control subjects.[4] A growing body of evidence suggests that genetic factors may be important in the pathogenesis of many cases of PSP. Familial clustering of this condition has been reported. Genetic disorders that have been linked to PSP include Marfan syndrome, homocystinuria, and Birt-Hogg-Dube (BHD) syndrome. Birt-Hogg-Dube syndrome is an autosomal dominant disorder that is characterized by benign skin tumors (hair follicle hamartomas), renal and colon cancer, and spontaneous pneumothorax. Spontaneous pneumothorax occurs in about 22% of patients with this syndrome. The gene responsible for this syndrome is a tumor suppressor gene located on band 17p11.2. The gene encoding folliculin (FLCN) is thought to be the etiology of Birt-Hogg-Dube syndrome. Multiple mutations have been found, and phenotypic variation is recognized. In one study, 8 patients without skin or renal involvement had lung cysts and spontaneous pneumothorax.[6] A germ-line mutation to this gene has been found in 5 patients, and genetic testing is now available. Tension pneumothoraxTension pneumothorax occurs anytime a disruption involves the visceral pleura, parietal pleura, or the tracheobronchial tree. This condition develops when injured tissue forms a 1-way valve, allowing air inflow with inhalation into the pleural space and prohibiting air outflow. The volume of this nonabsorbable intrapleural air increases with each inspiration because of the 1-way valve effect. As a result, pressure rises within the affected hemithorax. In addition to this mechanism, the positive pressure used with mechanical ventilation therapy can cause air trapping. As the pressure increases, the ipsilateral lung collapses and causes hypoxia. Further pressure increases cause the mediastinum to shift toward the contralateral side and impinge on and compress both the contralateral lung and impair the venous return to the right atrium. Hypoxia results as the collapsed lung on the affected side and the compressed lung on the contralateral side compromise effective gas exchange. This hypoxia and decreased venous return caused by compression of the relatively thin walls of the atria impair cardiac function. Kinking of the inferior vena cava is thought to be the initial event restricting blood to the heart. It is most evident in trauma patients who are hypovolemic with reduced venous blood return to the heart. Arising from numerous causes, this condition rapidly progresses to respiratory insufficiency, cardiovascular collapse, and, ultimately, death if unrecognized and untreated. PneumomediastinumWith pneumomediastinum, excessive intra-alveolar pressures lead to rupture of alveoli bordering the mediastinum. Air escapes into the surrounding connective tissue and dissects further into the mediastinum. Esophageal trauma or elevated airway pressures may also allow air to dissect into the mediastinum. Air may then travel superiorly into the visceral, retropharyngeal, and subcutaneous spaces of the neck. From the neck, the subcutaneous compartment is continuous throughout the body; thus, air can diffuse widely. Mediastinal air can also pass inferiorly into the retroperitoneum and other extraperitoneal compartments. If the mediastinal pressure rises abruptly or if decompression is not sufficient, the mediastinal parietal pleura may rupture and cause a pneumothorax (in 10-18% of patients).A wide variety of disease states and circumstances may result in a pneumothorax.Primary and secondary spontaneous pneumothoraxRisks factors for primary spontaneous pneumothorax (PSP) include the following: Smoking Tall, thin stature in a healthy person Marfan syndrome Pregnancy Familial pneumothorax Blebs and bullae (sometimes called emphysematouslike changes or ELCs) are related to the occurrence of primary spontaneous pneumothorax. Thoracic computerized tomography (CT) scans of patients with PSP shows ipsilateral ELC in 89% and contralateral changes in 80% compared with a rate of 20% among control subjects matched for age and smoking.[2] Nonsmokers with PSP had CT scan ELC abnormalities of 80% compared with a rate of 0% among nonsmoker controls without PSP.[2] Although patients with PSP do not have overt parenchymal disease, this condition is heavily associated with smoking80-90% of primary spontaneous pneumothorax (PSP) cases occur in smokers or former smokers, and the relative risk of PSP increases as the number of cigarettes smoked per day increases; that is, the risk of PSP is related to the intensity of smoking, with 102-times higher incidence rates in males who smoke heavily (ie, >22 cigarettes/d), compared with a 7-fold increase in males who smoke lightly (1-12 cigarettes/d). This incremental risk with increasing number of cigarettes smoked per day is much more pronounced in female smokers. Typical PSP patients also tend to have a tall and thin body habitus. Whether height affects development of subpleural blebs or whether more negative apical pleural pressures cause preexisting blebs to rupture is unclear. Pregnancy is an unrecognized risk factor, as suggested by a 10-year retrospective series in which 5 of 250 spontaneous pneumothorax cases were in pregnant women.[7] The cases were all managed successfully with simple aspiration or vacuum-assisted thoracostomy (VATS), and no harm occurred to mother or fetus.[7] Other associations with pneumothorax include increased intrathoracic pressure with Valsalva, although results contrary to popular belief, most spontaneous pneumothoraces occur while the patient is at rest. Changes in atmospheric pressure, proximity to loud music, and low frequency noises are other reported factors. Familial associations have been noted in more than 10% of patients. Some are due to rare connective tissue diseases, but mutations in the gene encoding folliculin (FLCN) have been described. These patients may represent an incomplete penetrance of an autosomal dominant genetic disorder. Birt-Hogg-Dube syndrome is characterized by benign skin growths, pulmonary cysts, and renal cancers and is caused by mutations in the FLCN gene. In one family study, 9 ascertained cases of spontaneous pneumothorax were reported among 54 members. A review of the literature summarized 61 reports of familial spontaneous pneumothorax among 22 families. Up to 10% patients with spontaneous pneumothorax report a positive family history.[8] Although rare, spontaneous pneumothorax occurring bilaterally and progressing to tension pneumothorax has been documented.Diseases and conditions associated with secondary spontaneous pneumothorax include the following: Chronic obstructive lung disease (COPD) or emphysema: Increased pulmonary pressure due to coughing with a bronchial plug of mucus or phlegm bronchial plug may play a role. Asthma Human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) with PCP infection Necrotizing pneumonia Tuberculosis Sarcoidosis Cystic fibrosis Bronchogenic carcinoma or metastatic malignancy Idiopathic pulmonary fibrosis Inhalational and intravenous drug use (eg, marijuana, cocaine) [9] Interstitial lung diseases associated with connective tissue diseases Lymphangioleiomyomatosis Langerhans cell histiocytosis Severe acute respiratory syndrome (SARS): A reported 1.7% of SARS patients developed spontaneous pneumothorax. [10] Thoracic endometriosis and catamenial pneumothorax Collagen vascular disease, including Marfan syndrome Secondary spontaneous pneumothoraces (SSP) occur in the presence of lung disease, primarily in the presence of COPD. Other diseases that may be present when SSPs occur include tuberculosis, sarcoidosis, cystic fibrosis, malignancy, and idiopathic pulmonary fibrosis. Pneumocystis jiroveci pneumonia (previously known as Pneumocystis carinii pneumonia [PCP]) was a common cause of SSP in patients with AIDS during the last decade. In fact, 77% of AIDS patients with spontaneous pneumothorax had thin-walled cavities, cysts, and pneumothorax from PCP infection.[11] With the advent of highly active antiretroviral therapy (HAART) and widespread use of trimethoprim-sulfamethoxazole (TMP-SMZ) prophylaxis, the incidence of PCP and associated SSP has significantly declined. PCP in other immunocompromised patients is seen only when TMP-SMZ prophylaxis is withdrawn prematurely. For practical purposes, if the immunocompromised patient has been taking TMP-SMZ prophylaxis reliably, PCP is reasonably excluded from the differential diagnosis and should not be a causative factor for SSP. In cystic fibrosis, up to 18.9% of patients have been reported to develop spontaneous pneumothoraces, and they have a high incidence of recurrence on the same side after conservative management (50%) or intercostal drainage (55.2%). The risk of SSP in these patients increases with Burkholderia cepacia or Pseudomonas infections and allergic bronchopulmonary aspergillosis (ABPA).[12] Pleurodesis increases the risk of bleeding associated with lung transplantation but is not an absolute contraindication. Many different types of malignancies are known to present with a pneumothorax, especially sarcomas, but also genitourinary cancers and primary lung cancer; thus, pneumothorax in a patient with malignancy should prompt a look for metastatic disease. Chemotherapeutic agents, at times, can also induce SSP.[13] Interstitial lung diseases are associated with connective-tissue diseases. Ankylosing spondylitis may be noted when apical fibrosis is present; in fact, the typically low incidence of spontaneous pneumothorax in patients with ankylosing spondylitis (0.29%) increases 45-fold (to 13%) when apical fibrotic disease exists.[14] Lymphangioleiomyomatosis (LAM) may present with spontaneous pneumothorax. This disease is characterized by thin-walled cysts in women of childbearing age. Respiratory failure may lead to a need for lung transplantation, and previous pleurodesis is no longer an absolute contraindication for lung transplantation. Thoracic endometriosis is a rare cause of recurrent pneumothorax (catamenial pneumothorax) in women that is thought to arise from endometriosis reaching the chest wall across the diaphragm (ie, its etiology may be primarily related to associated diaphragmatic defects). In a case series of 229 patients, catamenial pneumothorax caused by thoracic endometriosis was localized to the visceral pleura in 52% of patients and to the diaphragm in 39% of patients.[15] Before recurrence, this condition may be initially diagnosed as primary spontaneous pneumothorax. Iatrogenic and traumatic pneumothoraxCauses of iatrogenic pneumothorax include the following: Transthoracic needle aspiration biopsy of pulmonary nodules (most common cause, accounting for 32-37% of cases) Transbronchial or pleural biopsy Thoracentesis Central venous catheter insertion, usually subclavian or internal jugular [16] Intercostal nerve block Tracheostomy Cardiopulmonary resuscitation (CPR): Consider the possibility of a pneumothorax if ventilation becomes progressively more difficult. Acute respiratory distress syndrome ( ARDS) and positive pressure ventilation in the ICU: High peak airway pressures can translate into barotrauma in up to 3% of patients on a ventilator and up to 5% of patients with ARDS. [17] Nasogastric feeding tube placement Iatrogenic pneumothorax is a complication of medical or surgical procedures. It most commonly results from transthoracic needle aspiration. Other procedures commonly causing iatrogenic pneumothorax are therapeutic thoracentesis, pleural biopsy, central venous catheter insertion, transbronchial biopsy, positive pressure mechanical ventilation, and inadvertent intubation of the right mainstem bronchus. Therapeutic thoracentesis is complicated by pneumothorax 30% of the time when performed by inexperienced operators in contrast to only 4% of the time when performed by experienced clinicians. The routine use of ultrasonography during diagnostic thoracentesis is associated with lower rates of pneumothorax (4.9% vs 10.3%) and need for tube thoracostomy (0.7% vs 4.1%). Similarly, in patients who are mechanically ventilated, thoracentesis guided by bedside ultrasonography without radiology support results in a relatively lower rate of pneumothorax. Causes of traumatic pneumothorax include the following: Trauma: Penetrating and nonpenetrating injury Rib fracture High-risk occupation (eg, diving, flying) Traumatic pneumothoraces can result from both penetrating and nonpenetrating lung injuries. Complications include hemopneumothorax and bronchopleural fistula. Traumatic pneumothoraces often can create a 1-way valve in the pleural space (only letting in air without escape) and can lead to a tension pneumothorax. Tension pneumothoraxThe most common etiologies of tension pneumothorax are either iatrogenic or related to trauma, such as the following: Blunt or penetrating trauma: Disruption of either the visceral or parietal pleura occurs and is often associated with rib fractures, although rib fractures are not necessary for tension pneumothorax to occur. Barotrauma secondary to positive-pressure ventilation, especially when using high amounts of positive end-expiratory pressure (PEEP) Pneumoperitoneum [18, 19] Fiberoptic bronchoscopy with closed-lung biopsy [20] Markedly displaced thoracic spine fractures Acupuncture [21, 22, 23] Preexisting Bochdalek hernia with trauma [24] Colonoscopy [25] and gastroscopy have been implicated in case reports. Percutaneous tracheostomy [26] Conversion of idiopathic, spontaneous, simple pneumothorax to tension pneumothorax Unsuccessful attempts to convert an open pneumothorax to a simple pneumothorax in which the occlusive dressing functions as a 1-way valve Tension pneumothorax occurs commonly in the ICU setting in patients who are ventilated with positive pressure, and practitioners must always consider this when changes in respiratory or hemodynamic status occur. Infants requiring ventilatory assistance and those with meconium aspiration have a particularly high risk for tension pneumothorax. Aspirated meconium may serve as a 1-way valve and produce a tension pneumothorax. Any penetrating wound that produces an abnormal passageway for gas exchange into the pleural spaces and that results in air trapping may produce a tension pneumothorax. Blunt trauma, with or without associated rib fractures, and incidents such as unrestrained head-on motor vehicle accidents, falls, and altercations involving laterally directed blows may also cause tension pneumothoraces. Significant chest injuries carry an estimated 10-50% risk of associated pneumothorax; in about 50% of these cases, the pneumothorax may not be seen on standard radiographs and are therefore deemed occult. In one study, 12% of patients with asymptomatic chest stab wounds had a delayed pneumothorax or hemothorax. McPherson et al analyzed data from the Vietnam Wound Data and Munitions Effectiveness Team study and determined that tension pneumothorax was the cause of death in 3-4% of fatally wounded combat casualties.[27] Acupuncture is a traditional Chinese medicine technique used worldwide by alternative medical practitioners. Acupuncture's most frequently reported serious complication is pneumothorax; in one Japanese report of 55,291 acupuncture treatments, an approximate incidence of 1 pneumothorax in 5000 cases was documented.[28] PneumomediastinumThe following factors may result in pneumomediastinum: Acute generation of high intrathoracic pressures (often as a result of inhalational drug use, such smoking marijuana or inhalation of cocaine) Asthma Respiratory tract infection Parturition Emesis Severe cough Mechanical ventilation Trauma or surgical disruption of the oropharyngeal, esophageal, or respiratory mucosa Athletic competition EpidemiologyThe epidemiologic data vary among the pneumothorax classifications. Primary, secondary, and recurring spontaneous pneumothoraxIt is likely that the incidence for spontaneous pneumothorax is underestimated. Up to 10% of patients may be asymptomatic, and others with mild symptoms may not present to a medical provider. Primary spontaneous pneumothoraces (PSPs) occur in people aged 20-30 years, with a peak incidence is in the early twenties.PSP is rarely observed in people older than 40 years. The age-adjusted incidence of PSP is 7.4-18 cases per 100,000 persons per year for men and 1.2-6 cases per 100,000 persons per year for women.[29] The male-to-female ratio of age-adjusted rates is 6.2:1. Secondary spontaneous pneumothoraces (SSPs) occur more frequently in patients aged 60-65 years. The age-adjusted incidence of SSP is 6.3 cases per 100,000 persons per year for men and 2.0 cases per 100,000 persons per year for women. The male-to-female ratio of age-adjusted rates is 3.2:1. Chronic obstructive pulmonary disease (COPD) is a common cause of secondary spontaneous pneumothorax that carries an incidence of 26 cases per 100,000 persons.[30] Smoking increases the risk of a first spontaneous pneumothorax by more than 20-fold in men and by nearly 10-fold in women compared with risks in nonsmokers.[31] Increased risk of pneumothorax and recurrence appears to rise proportionally with number of cigarettes smoked. In men, the risk of spontaneous pneumothorax is 102 times higher in heavy smokers than in nonsmokers. Spontaneous pneumothorax most frequently occurs in tall, thin men aged 20-40 years. Iatrogenic and traumatic pneumothoraxTraumatic and tension pneumothoraces occur more frequently than spontaneous pneumothoraces, and the rate is undoubtedly increasing in US hospitals as intensive care treatment modalities have become increasingly dependent on positive-pressure ventilation, central venous catheter placement, and other causes that potentially induce iatrogenic pneumothorax. Iatrogenic pneumothorax may cause substantial morbidity and, rarely, death. The incidence of iatrogenic pneumothorax is 5-7 per 10,000 hospital admissions, with thoracic surgery patients excluded because pneumothorax may be a typical outcome following these surgeries. Pneumothorax occurs in 1-2% of all neonates, with a higher incidence in infants with neonatal respiratory distress syndrome. In one study, 19% of such patients developed a pneumothorax. Tension pneumothoraxTension pneumothorax is a complication in approximately 1-2% of the cases of idiopathic spontaneous pneumothorax. Until the late 1800s, tuberculosis was a primary cause of pneumothorax development. A 1962 study showed a frequency of pneumothorax of 1.4% in patients with tuberculosis. The actual incidence of tension pneumothorax outside of a hospital setting is impossible to determine. Approximately 10-30% of patients transported to level-1 trauma centers in the United States receive prehospital decompressive needle thoracostomies; however, not all of these patients actually have a true tension pneumothorax. Although this occurrence rate may seem high, disregarding the diagnosis would probably result in unnecessary deaths. A review of military deaths from thoracic trauma suggests that up to 5% of combat casualties with thoracic trauma have tension pneumothorax at the time of death.[27] The overall incidence of tension pneumothorax in the intensive care unit (ICU) is unknown. The medical literature provides only glimpses of the frequency. In one report, of 2000 incidents reported to the Australian Incident Monitoring Study (AIMS), 17 involved actual or suspected pneumothoraces, and 4 of those were diagnosed as tension pneumothorax. Catamenial pneumothoraxCatamenial pneumothorax is a rare phenomenon that generally occurs in women aged 30-50 years. It frequently begins 1-3 days after menses onset. The risk of thoracic endometriosis cannot be predicted from the site of peritoneal lesions.[15] PneumomediastinumSpontaneous pneumomediastinum generally occurs in young, healthy patients without serious underlying pulmonary disease, mostly in the second to fourth decades of life. A slight predominance of pneumomediastinum exists for males. This condition occurs in approximately 1 case per 10,000 hospital admissions. PrognosisThe prognosis varies among the pneumothorax classifications.Primary, secondary, and recurring spontaneous pneumothoraxComplete resolution of an uncomplicated pneumothorax takes approximately 10 days. PSP is typically benign and often resolves without medical attention. Many affected individuals do not seek medical attention for days after symptoms develop. This trend is important, because the incidence of reexpansion pulmonary edema increases in patients whose chest tubes have been placed 3 or more days after the pneumothorax occurred. Recurrences usually strike within the first 6 months to 3 years. The 5-year recurrence rate is 28-32% for primary spontaneous pneumothorax (PSP) and 43% for secondary spontaneous pneumothorax (SSP). Recurrences are more common among patients who smoke, patients with chronic obstructive pulmonary disease (COPD), and patients with acquired immunodeficiency syndrome (AIDS). Predictors of recurrence include pulmonary fibrosis, younger age, and increased height-to-weight ratio. In a retrospective study of 182 consecutive patients with a newly diagnosed first episode of pneumothorax, a higher rate of recurrence was noted in taller patients, thin patients, and patients with SSP. Patients who underwent bedside chest tube pleurodesis had cumulative rates of recurrence of 13% at 6 months, 16% at 1 year, and 27% at 3 years compared with 26%, 33%, and 50%, respectively. The agent used (tetracycline or gentamicin) did not have any significant impact on the recurrence rate. Bullous lesions found on computed tomography (CT) scan or at thoracoscopy and the presence of emphysematouslike changes in PSP are also not predictive of recurrence. However, contralateral blebs were seen by CT scanning in higher frequency in the patients with contralateral recurrence (33 patients; 14%) than those without a contralateral recurrence in a retrospective study of 231 patients with PSP. Primary bilateral spontaneous pneumothorax (PBSP) was significantly more common in patients with lower body mass index (BMI) and among smokers.[32] In this series, all patients with contralateral recurrence were treated surgically. Although some authors view PSP as more of a nuisance than a major health threat, deaths have been reported. SSPs are more often life threatening, depending on the severity of the underlying disease and the size of the pneumothorax (1-17% mortality rate). In particular, compared with similar patients without pneumothorax, age-matched patients with COPD have a 3.5-fold increase in relative mortality when a spontaneous pneumothorax occurs, and their risk of recurrence rises with each occurrence. One study indicated that 5% of patients with COPD died before a chest tube was placed. Patients with AIDS also have a high inpatient mortality rate of 25% and a median survival of 3 months after the pneumothorax. These data derive from an era before highly active antiretroviral therapy (HAART) was available. Tension pneumothoraxTension pneumothorax arises from numerous causes and rapidly progresses to respiratory insufficiency, cardiovascular collapse, and, ultimately, death if not recognized and treated. Therefore, if the clinical picture fits a tension pneumothorax, it must be emergently treated before it results in hemodynamic instability and death. PneumomediastinumPneumomediastinum is generally a benign, self-limited condition. Malignant pneumomediastinum, or tension pneumomediastinum (unvented mediastinal or pulmonary adventitial air causing pressure so high that circulatory or ventilatory failure occurs), was first described in 1944; however, all patients described in this report had serious comorbid conditions, often related to trauma or in association with Boerhaave syndrome. No reports of fatal outcomes in patients with spontaneous pneumomediastinum in the absence of underlying disease exist in the more recent literature. The mortality rate is as high as 70% in patients with pneumomediastinum secondary to Boerhaave syndrome, even with surgical intervention. Traumatic mediastinum, although present in up to 6% of patients does not portend serious injury.[33] Patient EducationTwo important concerns that clinicians should educate patients with pneumothorax/resolving pneumothorax about are avoidance of air travel/travel to remote regions and prohibition of smoking. Patients should also be advised to wear safety belts and passive restraint devices while driving. Avoid traveling by air or to remote areasPatients should not travel by air or travel to remote sites until radiography shows complete resolution. Although commercial air travel achieves minimal change in gas volumes due to pressurization of the cabin, spontaneous pneumothorax has been described during commercial travel. Patients with previous spontaneous pneumothoraces are at risk for recurrence and are advised not to dive unless thoracotomy or pleurodesis has been performed.[34] Ascent from deep-sea diving causes gases to expand and can lead to pneumothorax in patients with bullae and blebs. Stop smokingSmoking cessation is strongly advised for all patients. They should be assessed as to readiness to quit, to be educated about smoking cessation, and be provided with pharmacotherapy if ready to quit. Direct patients indicating a readiness to quit smoking to their primary care physician or offer referral for cessation management. This may include nicotine replacement and non-nicotine pharmacotherapy such as bupropion or varenicline. Whether primary or secondary pneumothorax, smoking increases the likelihood of bleb rupture and recurrence, and it does so in a predictable, dose-related manner. Relative risk of bleb rupture and recurrence rises by up to a factor of 20. For patient education information, see the Lung and Airway Center and Breathing Difficulties Center, as well as Collapsed Lung (Pneumothorax) and Chest Pain.Diagnostic ConsiderationsThis section reviews some important points to consider in the diagnosis of pneumothoraces. Spontaneous pneumothorax Because patients with primary spontaneous pneumothorax (PSP) will have apical emphysematous pulmonary disease on computed tomography (CT) scanning or thoracoscopy, they can be thought to have a congenital syndrome of mild acinar emphysema, whose expression is enhanced by environmental factors (eg, smoking) just as it is in patients with alpha-1-antitrypsin deficiency and "typical" emphysema. Folliculin gene disorders have been described in familial spontaneous pneumothorax.[4] These patients may have pneumothorax as the presenting symptom of Birt-Hogg-Dube disease.[5] Some authors recommend screening patients with a family history of pneumothorax for the benign skin tumors and renal cancers that arise from the disease. Catamenial pneumothorax is a rare cause of recurrent pneumothorax in women. Prior to recurrence, this condition may initially be diagnosed as PSP. Pneumonia is a possible cause of pneumothorax; in the patient with human immunodeficiency virus infection (HIV), Pneumocystis jiroveci pneumonia (PCP) , toxoplasmosis, and Kaposi sarcoma need to be considered . A patient with HIV can have spontaneous pneumothorax as the presenting symptom of their illness: HIV carries a lifetime risk of 6% for pneumothorax, and about 85% of that number is related to PCP pneumonia. The rare event of spontaneous pneumothorax leading to tension pneumothorax may be misdiagnosed as an asthma crisis or exacerbation of chronic obstructive pulmonary disease (COPD) in the patient presenting with tachycardia, subcutaneous emphysema, dyspnea, and shock. Traumatic pneumothorax Always consider pneumothorax in the differential diagnosis of major trauma. In the patient with blunt trauma and mental status changes, hypoxia, and acidosis, symptoms of a tension pneumothorax may be masked by associated and similarly potentially lethal injuries. When assessing the trauma patient, be aware that clinical presentations of tension pneumothorax and cardiac tamponade may be similar. Tension pneumothorax The diagnosis of a tension pneumothorax should largely be made based on the history and physical examination findings. Ultrasonography in the emergency setting is being increasingly used as an adjunct to the physical examination when there is doubt regarding the diagnosis. Chest radiography or CT scanning should be used only in those instances when the clinician is in doubt regarding the diagnosis and when the patient's clinical condition is hemodynamically stable. Obtaining such imaging studies when the diagnosis of tension pneumothorax is not in question causes an unnecessary and potentially lethal delay in treatment. A tension pneumothorax is a life-threatening condition and requires immediate action (eg, needle thoracostomy or chest tube insertion). However, the clinician should be wary of prematurely diagnosing a tension pneumothorax in a patient without respiratory distress, hypoxia, hypotension, or cardiopulmonary compromise. If the patient's clinical presentation is questionable and if the patient appears stable, the clinician should reexamine the patient and use bedside ultrasonography or request immediate portable chest radiography (or reexamine the chest radiographs if they have already been obtained) to confirm the diagnosis. A high index of suspicion for tension pneumothorax is recommended in patients on mechanical ventilation with acute onset of hemodynamic instability, difficult ventilation with high inspiratory pressures, and worsening hypoxemia and/or hypercapnia, even with a functioning chest tube in place. Patients at greatest risk of a pneumothorax and/or tension pneumothorax include those with COPD who are using ventilators; those with acute respiratory distress syndrome (ARDS); and those receiving a tidal volume greater than 12 mL/kg, a peak airway pressure greater than 60 cm H2 O, or a positive end-expiratory pressure greater than 15 cm H2 O. Portable chest radiograph may fail to show the pneumothorax; CT scanning may be required for diagnosis. Avoid assuming that a patient with a chest tube does not have a tension pneumothorax if he or she has respiratory or hemodynamic instability. Chest tubes can become plugged or malpositioned and cease to function. In addition, improper attachment of a 1-way valve to the chest tube may produce tension pneumothorax. Other conditions to consider include the following: Aspiration, Bacterial, Mycoplasmal, and Viral Pneumonia Asthma Costochondritis Diaphragmatic Injuries Esophageal Spasm Foreign Bodies, Trachea Mediastinitis Myocardial Ischemia Myocarditis Pericarditis Pleurodynia Pulmonary Empyema and Abscess Tuberculosis Differential Diagnoses Acute Aortic Dissection Acute Coronary Syndrome Acute Pericarditis Esophageal Rupture and Tears in Emergency Medicine Heart Failure Myocardial Infarction Pediatric Acute Respiratory Distress Syndrome Pulmonary Embolism Rib FractureApproach ConsiderationsDespite general agreement on the management of pneumothorax, a full consensus about management of initial or recurrent pneumothorax does not exist. Professional societies differ in their approach to management and hospitalization.[39, 54] This section presents a risk stratification framework as well as other approaches for choosing among options to restore lung volume and an air-free pleural space and to prevent recurrences.[1] These goals are applicable across diverse clinical presentations. The range of therapeutic options includes watchful waiting with or without supplemental oxygen, simple aspiration, tube drainage with or without medical pleurodesis, vacuum-assisted thoracostomy (VATS) with pleurodesis and/or closure of leaks and bullectomy, and open surgical procedures such as thoracotomy for pleurectomy or pleurodesis. Selection between the various management options requires an understanding of the natural history of pneumothorax, the risk of recurrent pneumothorax, and the benefits and limitations of each treatment option and discussion with the patient. See also Restoring an Air-Free Pleural Space in Pneumothorax.PharmacotherapyMedication may be necessary to treat a pulmonary disorder that causes the pneumothorax. For example, intravenous antibiotics are included in the treatment of a pneumothorax that developed as a sequela of staphylococcal pneumonia. In addition, studies suggest that the administration of prophylactic antibiotics during chest tube insertion may reduce the incidence of complications such as emphysema. Clearly, the use of analgesics can provide patient comfort until the thoracostomy tube is removed. Some authors advocate the use of intercostal nerve blocks to increase patient comfort and decrease the need for narcotic analgesics. In patients with repeated pneumothoraces who are not good candidates for surgery, sclerotherapy with talc or doxycycline may be necessary. Treatment Based on Risk StratificationThe decision to observe or to treat with an immediate intervention should be guided by a risk stratification that considers the patient's presentation and the likelihood of spontaneous resolution and recurrence. Patient presentationThe following are possible presentations of patients with pneumothorax: Asymptomatic (incidental finding): Treatment decisions are guided by estimate of long-term recurrence risk. Symptomatic but clinically stable: Treatment is guided by local resources and conventions for the site of care. The British Thoracic Society (BTS) advocates for simple aspiration and deferring hospitalization in primary spontaneous pneumothorax (PSP) as initial management if the patient is stable. [54] A small bore catheter or chest tube placement is recommended by the American College of Chest Physicians (ACCP) Delphi consensus statement. [39] Clinically fragile: Treatment is guided by local practice patterns for air evacuation and observation. Comorbid conditions may preclude observation because of decreased cardiopulmonary reserve. Life threatening: Pneumothorax that causes hemodynamic instability is life-threatening and must be treated immediately with tube thoracostomy. All documents and recommendations call for intervention if a patient is unstable. Likelihood of resolutionThe likelihood of a pneumothorax resolving is classified as follows: Very likely to resolve: Small pneumothorax in a hemodynamically stable patient without significant parenchymal lung disease; small iatrogenic pneumothorax May resolve: Large pneumothorax in a normal lung (eg, PSP or iatrogenic pneumothorax) Unlikely to resolve: Secondary pneumothorax, enlarging pneumothorax (suggests a continuing air leak) Will not resolve, could be fatal: Tension pneumothorax; unrecognized air leak Likelihood of recurrenceThe following categories of pneumothorax recurrence likelihood should be assessed: Unlikely to recur: Iatrogenic pneumothorax in normal lung May recur, but patient will likely be clinically stable May recur and the patient may be clinically unstable, but emergency care is readily accessible Very likely to recur: Diffuse and progressive pulmonary pathology (eg, lymphangioleiomyomatosis [LAM]) Recurrence could be life-threatening: Poor cardiopulmonary reserve, limited access to emergency medical care Selection of site of patient careThe following is a suggested guideline on determining where to administer care in a patient with a pneumothorax: Outpatient care: This can occur in asymptomatic patients or those with a small pneumothorax and reliable follow-up. Emergency department (ED) care: Prolonged periods of observation are inefficient and clinically suboptimal; efficacy studies of manual aspiration and placement of 1-way valves performed in EDs are an attempt to address these practical issues. Inpatient care: This site of care is generally selected when high-flow oxygen is needed, the pneumothorax is larger but the patient is stable, or comorbidities increase concern about risk or follow-up. The average hospital stay is 2.8 days. Intensive care unit (ICU): ICU treatment and observation is appropriate for patients who are unstable or intubated. Interval of observationNo protocols regarding serial radiography or imaging exist; the clinician typically reviews serial vital signs and clinical assessments, using the direction and rate of change in the patients clinical status to select imaging frequency. Monitoring pneumothorax size during this time is important, as follows: At 0-6 hours: The ACCP Delphi consensus statement recommends observation in an ED for 6 hours, and discharge to home if a follow-up chest radiograph shows no enlargement of the lesion, in reliable patients. [39] Emergency room observation with a repeat radiograph 6 hours later used to be common but may be used less often now. At 24-96 hours: Additional follow up in 2 days is recommended, with preference given to a 24-48 hour follow-up radiograph in the outpatient setting. Outpatient follow-up during the 96-hour (4-d) window is essential to distinguish between a resolved pneumothorax and one that needs evacuation. A computed tomography (CT) scan at this time distinguishes between PSP and secondary spontaneous pneumothorax (SSP). At 1 month: Full lung reexpansion can occur, on average, 3 weeks after the initial event. Restoring an Air-Free Pleural Space Several options are available to restore an air-free pleural space, including observation without oxygen, administering supplemental oxygen, simple aspiration, chest tube placement, 1-way valve insertion, and thoracostomy with continuous suction. (See the video of chest tube insertion, below.) Insertion of chest tube. Video courtesy of Therese Canares, MD, and Jonathan Valente, MD, Rhode Island Hospital, Brown University. Contou et al recommend that clinicians consider drainage via a small-bore catheter as a first-line treatment for pneumothorax of any cause. The authors found that drainage via catheter or via chest tube is similarly effective for the management for the management of pneumothoraces, including primary spontaneous pneumothorax, secondary spontaneous pneumothorax, and traumatic and iatrogenic pneumothoraces.[55] See also Restoring an Air-Free Pleural Space in Pneumothorax. Observation without oxygen Simple observation is appropriate for asymptomatic patients with a minimal pneumothorax (< 15-20% by Light criteria; 2-3 cm from apex to cupola by alternate criteria) with close follow-up, ensuring no enlargement (see Estimating the size of the pneumothorax under Chest Radiography). Air is reabsorbed spontaneously by 1.25% of size pneumothorax per day.[56] An interesting multicenter, prospective, observational study reported on more than 500 trauma patients with occult pneumothorax identified on CT scan, with an initially normal chest radiograph. Controversy exists in the literature on the treatment of all patients with occult pneumothorax, whether to closely observe patients with occult pneumothorax or whether to place a chest tube. It is even more controversial in patients on positive pressure ventilation. It is generally accepted after trauma to treat pneumothorax seen on chest radiographs with chest tube thoracostomy. Conversion to tension pneumothorax is the worst feared complication if left untreated. The study arms included observation versus chest tube thoracostomy. Only 6% of patients failed observation and developed pneumothorax, including only 15% failed observation on positive pressure ventilation. In multivariate regression analysis, failure of observation was seen in patients with chest radiographic evidence of pneumothorax progression and symptoms of respiratory distress. According to this study, it is safe to closely observe trauma patients with occult pneumothorax on chest radiographs, even if receiving mechanical ventilation.[57] Supplemental oxygen Oxygen administration at 3 L/min nasal canula or higher flow treats possible hypoxemia and is associated with a 4-fold increase in the rate of pleural air absorption compared with room air alone. Simple aspiration Simple aspiration in 131 cases of small spontaneous pneumothorax yielded successful results up to 87%.[58] Other studies have described more limited success in up to 70% cases.[59] A more recent emergency department (ED) study supports needle aspiration as safe and effective as chest tube placement for primary spontaneous pneumothorax (PSP), conferring the additional benefits of shorter length of stay and fewer hospital admissions.[60] Chest tube placement A tube inserted into the pleural space is connected to a device with 1-way flow for air removal. Examples of such devices are Heimlich valves or water seal canisters, and tubes connected to wall suction devices. One-way valve insertion (portable system) The typical goal of inserting 1-way valve systems is to avoid hospital admission and still treat the spontaneous pneumothorax. One-way valves may also expedite hospital discharge and be used during transport of an injured patient. A Heimlich valve is a 1-way, rubber flutter valve that allows for complete evacuation of air that is not under tension. The proximal end attaches to the chest tube or catheter, and the distal end connects to a suction device or is left open to the atmosphere. Heimlich valves do not require suction and thus eliminate the chance of a tension pneumothorax; they also allow greater mobility and less discomfort for the patient. By decreasing the length of the hospital stay and allowing for outpatient care, medical costs are reduced as well. In a pilot study, Marquette et al determined that using a serial-steps approach with a single system (small-caliber catheter/Heimlich valve) in patients with a first episode of PSP was as effective as simple manual needle aspiration or a conventional chest tube thoracotomy.[61] In 41 thin, young, smoking males, a 1-way Heimlich valve was connected to the catheter, allowing the air to flow spontaneously outward for 24-48 hours; thereafter, if the lung failed to re-expand, wall suction was applied. Patients with an air leak persisting for more than 4 days were referred for surgery. At 24 hours, the success rate was 61%, and at 1 week, it had risen to 85%; the actuarial 1-year recurrence rate was 24%.[61] When 24-hour and 1-week success rates and recurrence at 12 months were taken as end points, the method described above was effective as simple manual needle aspiration or a conventional chest tube thoracotomy.[61] Heimlich valves are widely used in the care of patients with acquired immunodeficiency syndrome (AIDS) who have a median length of 20 days of chest tube placement to facilitate care and mobility. Thoracostomy with continuous wall suction First-time secondary spontaneous pneumothorax (SPS) (including chronic obstructive pulmonary disease [COPD]) and traumatic pneumothorax typically require this approach. A small-bore catheter (eg, 7-14F) is safe to use in most patients, whereas a larger chest tube (24F) is also appropriate initially, and increasing suction pressure can be used if the lung fails to inflate. A larger tube (eg, 28F) can reduce resistance in patients who are ventilated and at greater risk for air leaks. Air leaks resolve within 7 days of treatment 80% of the time, with an average hospital stay of 5 days. Keep the tube in place for 24 hours after the air leak ceases. Prehospital CareAssess the ABCs (airway, breathing, circulation), and evaluate the possibility of a tension pneumothorax. Assess the vital signs, and perform pulse oximetry. A tension pneumothorax is almost always associated with hypotension. Administer oxygen to the patient, ventilate the patient, and establish an intravenous (IV) line.Tension pneumothoraxFailure of the emergency medical service personnel (EMS) and medical control physician to make a correct diagnosis of tension pneumothorax and to promptly perform needle decompression in the prehospital setting can result in rapid clinical deterioration and cardiac arrest. Most paramedics are trained and protocolized to perform needle decompression for immediate relief of a tension pneumothorax. However, if an incorrect diagnosis of tension pneumothorax is made in the prehospital setting, the patient's life may be endangered by unnecessary invasive procedures. Close cooperation and accurate communication between the emergency department (ED) and the EMS personnel is of paramount importance. To prevent reentry of air into the pleural cavity after needle thoracostomy and decompression in the prehospital setting, a 1-way valve should be attached to the distal end of the Angiocath. If available, a Heimlich valve may be used. If a commercially prepared valve is not available, attach a finger condom or the finger of a rubber glove with its tip removed to serve as a makeshift 1-way valve device. Clothing covering a wound that communicates with the chest cavity can play a role in producing a 1-way valve effect, allowing air to enter the pleural cavity but hindering its exit. Removing such clothing items from the wound may facilitate decompression of a tension pneumothorax. A tension pneumothorax is a contraindication to the use of military antishock trousers.Prehospital ultrasonographyIn a preliminary 2006 study from Norway, Busch evaluated the feasibility of using portable ultrasound in an air rescue setting, concluding that prehospital ultrasonography could provide diagnostic and therapeutic benefit when conducted by a proficient examiner who used goal-directed and time-sensitive protocols.[43] Further study in this area may help to determine the indications and role of prehospital ultrasonography. Hospital ManagementImmediate attention to the ABCs (airway, breathing, circulation) while assessing vital signs and oxygen saturation is paramount, particularly in patients with thoracic trauma. Evaluate the patency of the airway and the adequacy of the ventilatory effort. Assess the circulatory status and the integrity of the chest wall. Carefully evaluate the cardiovascular system, because a tension pneumothorax and pericardial tamponade can cause similar findings. Emergency department (ED) care depends on the hemodynamic stability of the patient. All patients should receive supplemental oxygen to increase oxygen saturation and to enhance the reabsorption of free air. Note that ultrasonography is the only radiographic modality that allows patients with nonarrhythmogenic cardiac arrest to continue undergoing resuscitation while clinicians search for easily reversible causes of asystole or pulseless electrical activity (PEA).[62] A protocol (using the acronym CAUSE for cardiac arrest ultrasound exam) in which cardiac arrest patients, concurrent with resuscitation, receive bedside ultrasonography to look for cardiac tamponade, massive pulmonary embolus, severe hypovolemia, and tension pneumothorax has been proposed for further investigation. It is possible that the eventual adoption of ultrasonography in this setting may allow increased "real-time" diagnostic acumen, decreasing the time required to receive appropriate condition-related therapy. Primary and secondary spontaneous pneumothoraxIf the primary spontaneous pneumothorax (PSP) is smaller than 15% (or estimated as small) (see Estimating the size of the pneumothorax under Chest Radiography), and the patient is symptomatic but hemodynamically stable, needle aspiration is the treatment of choice.If the PSP is smaller than 15% and if the patient is asymptomatic, many consider observation to be the treatment of choice. (If the patient is admitted, administer oxygen, as this has been shown to speed resolution of the pneumothorax.) If the PSP is greater than 15% (or estimated as large) aspiration using a pigtail catheter left to low suction or water seal is recommended. Strong suction should not be used with a spontaneous pneumothorax because of an often-delayed presentation and, thus, an increased risk of reexpansion pulmonary edema (see Complications). Spontaneous pneumothorax is a life-threatening condition in patients with severe underlying lung disease; thus, tube thoracostomy is the procedure of choice in secondary spontaneous pneumothorax (SSP). Pleurodesis decreases the risk of recurrence, as does thoracotomy or video-assisted thoracoscopy (VAT) to excise the bullae.Iatrogenic and traumatic pneumothoraxAspiration is the technique of choice for iatrogenic pneumothoraces, because recurrence is usually not a factor. Tube thoracostomy is reserved for very symptomatic patients. In general, traumatic pneumothoraces should be treated with insertion of a chest tube, particularly if the patient cannot be closely observed. Chest tubes are attached to a one-way valve apparatus that uses a water chamber to avoid a direct connection to atmospheric pressure (so that during inspiration, when negative pressure is generated, air does not rush into the pleural space) and allows for the continuous removal air from the pleural cavity during respiration. Changing the pressure above the water seal allows for below atmospheric suction to further remove air from the pleural space. The collapsed lung reexpands and heals, thereby preventing continued air leakage. After air leaks have ceased for 24 hours, the vacuum may be decreased and the chest tube removed. The process of lung reexpansion and healing is not immediate and may be complicated by pulmonary edema; therefore, a chest tube is usually left in place until the clinical conditions are met; any complications warrant longer placement. A subset of patients who have a small (< 15-20%), minimally symptomatic pneumothorax may be admitted, observed closely, and monitored by using serial chest radiographs. In these patients, administration of 100% oxygen promotes resolution by speeding the absorption of gas from the pleural cavity into the pulmonary vasculature.Although commonly used, few data exist in the medical literature showing the efficacy of the procedure or reviewing the field-use and incidence of the needle decompression. Tension pneumothorax Tension pneumothorax remains a life-threatening condition diagnosed under difficult conditions, with a simple emergency procedure as treatment (ie, needle decompression). Make sure no contraindications exist for the placement of an emergency decompression catheter into the thorax. Previous thoracotomy, previous pneumonectomy, and presence of a coagulation disorder, for example, are relative contraindications, because failure to treat tension pneumothorax expectantly can result in patient death. Under emergent circumstances, place decompression catheters in the second rib interspace in the midclavicular line. This site was confirmed by Wax and Leibowitz, who reviewed 100 thoracic computed tomography (CT) scans by measuring the distance from the midline to the internal mammary artery and the average thickness of the tissues.[63] This procedure punctures through the skin and, possibly, through the pectoralis major muscle, external intercostals, internal intercostals, and parietal pleura. Placement in the middle third of the clavicle minimizes the risk of injury to the internal mammary artery during the emergency procedure.[63] Place the catheter just above the cephalad border of the rib, because the intercostal vessels are largest on the lower edge of the rib. Harcke et al had similar results when they used CT scan analysis of deployed male military personnel to determine that, at the second right intercostal space in the midclavicular line, the mean horizontal thickness was 5.36 cm, and that an 8-cm angiocatheter would reach the pleural space in 99% of the male soldiers in this series.[64] Unfortunately, in a 2005 study of emergency physicians, 21 of whom had completed advanced trauma and life support (ATLS) training, only 60% were able to correctly identify the second intercostal space when attempting to locate the needle thoracostomy site on a human volunteer, and all placed the thoracentesis needle medial to the midclavicular line.[62] In the same study, 8% of participants inappropriately identified the site used for needle pericardiocentesis and 4% inappropriately identified the fifth intercostal space in the anterior axillary line.[62] A 2011 study by Sanchez et all suggests the anterior approach is typically more successful than the lateral approach when it comes to angiocatheters, although the anterior approach is not failsafe. Further, longer angiocatheters may increase the chances of decompression, but the risk of damage to surrounding vital structures is higher.[65] Related to the development of apparent life-threatening hemorrhage after decompression in the second intercostal space at the anterior, midclavicular line in patients with no initial evidence of hemothorax on presentation, it has been suggested that a potentially safer option is to decompress a pneumothorax in the fifth intercostal space at the anterior axillary line, similar to recommendations for chest drain insertion. If a hemothorax is associated with the pneumothorax, additional chest tubes may be needed to assist drainage of blood and clots. If the hemopneumothorax requires insertion of a second chest tube, the second tube should be directed inferiorly and should be posterior to the apex of the diaphragm. Another point to take note of is that a significant number of patients have a larger chest wall than can be penetrated by a catheter length of 5 cm. In particular, men undergoing treatment for tension pneumothorax are more likely to have a larger body habitus with wider chest wall, such that performing needle thoracostomy may need a catheter longer than 5 cm to reliably penetrate into the pleural space. In one study, a catheter length of patients at an American level 1 trauma center showed that a catheter length of 5 cm would reliably penetrate the pleural space in only 75% of patients.[66] A 2008 study analyzing average chest wall thickness at the second intercostal space in the midclavicular line concluded that a 4.5-cm catheter length may not penetrate the chest wall in approximately 10-35% of trauma patients, depending on age and sex.[67] Catamenial pneumothoraxOral contraceptives carry a high success rate in the treatment of catamenial pneumothorax, although this condition may also (rarely) be treated surgically. Most cases present during or shortly after menses, and the spontaneous pneumothorax is usually right-sided. PneumomediastinumMost patients with pneumomediastinum should be observed for signs of serious complications (eg, pneumothorax, tension pneumothorax, mediastinitis). If the pneumomediastinum occurred from the inhalation of cocaine or smoking of marijuana, observation in the ED for progression may be indicated. A follow-up chest radiograph should be obtained in 12-24 hours to detect any progression or complication, such as pneumothorax. If no progression occurs at 24 hours and if no evidence of mediastinitis exists, the patient may be discharged. ndications for Surgical AssistanceIf the patient has had repeated episodes of pneumothorax or if the lung remains unexpanded after 5 days with a chest tube in place, operative therapy may be necessary. The surgeon may use treatment options such as thoracoscopy, electrocautery, laser treatment, resection of blebs or pleura, or open thoracotomy. Other surgical indications are as follows: Persistent air leak for longer than 7 days Recurrent, ipsilateral pneumothorax Contralateral pneumothorax Bilateral pneumothorax First-time presentation in a patient with a high-risk occupation (eg, diver, pilot) Patients with acquired immunodeficiency syndrome (AIDS) (often because of extensive underlying necrosis) Unacceptable risk of recurrent pneumothorax for patients with plans for extended stays at remote sites Lymphangiomyomatosis, a condition causing a high risk of pneumothorax [68] ThoracotomyWhile thoracotomy is the criterion standard, video-assisted thoracoscopic surgery (VATS) has been replacing thoracotomy in the treatment of chronic or persisting pneumothoraces due to the aforementioned reasons. Recurrence rates with thoracotomy are as low as 4%.[70] Talc is the preferred agent for pleurodesis. It can be administered by insufflation or as a slurry. Insufflation of talc and thoracotomy has a recurrence rate of 0-7%. ComplicationsMisdiagnosis is the most common complication of needle decompression. If a pneumothorax but not a tension pneumothorax is present, needle decompression creates an open pneumothorax. Alternatively, if no pneumothorax exists, the patient may develop a pneumothorax after the needle decompression is performed. Additionally, the needle may lacerate a lung, which, although rare, can cause significant pulmonary injury or hemothorax. If the needle is initially placed too medially to the sternum, needle decompression may cause a hemothorax by lacerating the inferior set of intercostal vessels or the internal mammary artery. Damage to the intercostal neurovascular bundle and lung parenchymal injury can occur following thoracostomy tube placement, especially if trocars are used for placement, and there is an increased risk of postoperative bleeding after lung transplantation for medical pleurodesis and surgery (length of hospital stay not affected).[68] Accidental disconnection and malpositioning of Heimlich valves can complicate an attempted outpatient treatment of pneumothorax via pigtail catheter. Pneumothorax complications include the following: Hypoxemic respiratory failure Respiratory or cardiac arrest Hemopneumothorax Bronchopulmonary fistula Pulmonary edema (following lung reexpansion) Empyema Pneumomediastinum Pneumopericardium Pneumoperitoneum Pyopneumothorax Complications of surgical procedures include the following: Failure to cure the problem Acute respiratory distress or failure Infection of the pleural space Cutaneous or systemic infection Persistent air leak Reexpansion pulmonary edema Pain at the site of chest tube insertion Prolonged tube drainage and hospital stay Reexpansion pulmonary edemaReexpansion pulmonary edema is a unilateral pulmonary edema that is seen after reinflation of a collapsed lung. It can also occur in the opposite lung. The incidence, etiology, risks, and mortality rates of this condition are controversial. Findings from animal studies and several case reports in humans indicate that reexpansion pulmonary edema may occur more often if a pneumothorax is present for longer than 3 days, if the evacuation volume is greater than 2000 mL, and if suction is applied. This information is important because in one study, 46% of patients waited more than 2 days after their symptoms started to seek medical attention, and, in another study, 18% waited more than 7 days. Tension pneumothoraxA worsening pneumothorax, usually with a 1-way valve phenomenon, can allow air into the intrapleural space and prevent its escape, causing mediastinal shift, pulmonary shunting, and circulatory collapse. Treatment of tension pneumothorax is emergent and should be performed before confirmatory radiologic studies. Needle decompression is performed before definitive treatment with tube thoracostomy (see Tension pneumothorax under Hospital Management). In mechanically ventilated patients, high pressures and air trapping place patients at risk for tension pneumothorax if the thoracostomy is not functioning. Patients with smaller pneumothoraces that would otherwise be managed with aspiration or observation sometimes undergo thoracostomy because of the need for mechanical ventilation.