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HYPOXIA, HYPOXIA, ASPHYXIAASPHYXIAand other and other conditionsconditions

Lecture 8Lecture 8

Important TerminologyImportant Terminology• • Hypoventilation: Ventilation inappropriately low for the metabolic Hypoventilation: Ventilation inappropriately low for the metabolic

demands. Alveolar/arterial PCO2 is elevated, alveolar/arterial PO2 is demands. Alveolar/arterial PCO2 is elevated, alveolar/arterial PO2 is

low.Antonym: hyperventilationlow.Antonym: hyperventilation

• • Eupnea: Normal spontaneous breathing. Ventilation is matched to Eupnea: Normal spontaneous breathing. Ventilation is matched to

metabolic demands.metabolic demands.

• • Tachypnea: Increased frequency of breathing. Ventilation may or may Tachypnea: Increased frequency of breathing. Ventilation may or may

not be changed depending on tidal volume. Antonym: bradypneanot be changed depending on tidal volume. Antonym: bradypnea

• • Dyspnea: Subjective sensation of difficult or labored breathing. Dyspnea: Subjective sensation of difficult or labored breathing.

Orthopnea is dyspnea associated with lying down.Orthopnea is dyspnea associated with lying down.

• • Apnea: temporary absence or cessation of breathing (airflow)- normally Apnea: temporary absence or cessation of breathing (airflow)- normally

occurs after hyperventilating or swallowing.occurs after hyperventilating or swallowing.

APNEA is a APNEA is a nonspecific indicator of nonspecific indicator of

distressdistress Failure of a systemFailure of a system Early indicator of Early indicator of

deteriorationdeterioration

Many known cause of apnea can be diagnosed and treated.

PERIODIC BREATHINGPERIODIC BREATHING

Thought to be benign

PB Apnea SIDS???

Definition of Periodic Breathing: is the abnormal or uneven respiratory rhythm

APNEAAPNEA Cessation of respiratory airflowCessation of respiratory airflow

CENTRALCENTRALNo respiratory effort, no nasal airflowNo respiratory effort, no nasal airflowDevelopmental phenomenonDevelopmental phenomenon

OBSTRUCTIVE respiratory effort, no nasal airflow,

HR. Caused by aspiration, laryngospasm

or poor airway controlMIXED Both obstructive and central

Sleep Disordered BreathingSleep Disordered Breathing

•Can’t Breath = Obstructive Sleep Apnea (OSA)•Won’t Breath = Central Sleep Apnea -Cheyne Stokes Respiration (CSR)

Cheyne-Stokes Breathing

•Periodic waxing and waning of ventilation without pharyngeal obstruction•Common in heart failure and cerebral vascular disease

Biot’s breathingBiot’s breathing

HYPOXIAHYPOXIA A condition where there is A condition where there is

decreased Oxygen supply decreased Oxygen supply to the tissues to the tissues

HYPOXIA: CLASSIFICATION HYPOXIA: CLASSIFICATION

1.1. Hypoxic Hypoxia Hypoxic Hypoxia:: Arterial P OArterial P O22 is less. is less.

2. 2. Anemic HypoxiaAnemic Hypoxia:: Decreased Hemoglobin causing Decreased Hemoglobin causing OO22

carriagecarriage

3. 3. Stagnant HypoxiaStagnant Hypoxia:: Due to slow & low blood flow.Due to slow & low blood flow.

4. 4. Histotoxic HypoxiaHistotoxic Hypoxia:: Tissue toxins deny OTissue toxins deny O2 2 to the cells.to the cells.

HYPOXIC HYPOXIAHYPOXIC HYPOXIA The arterial POThe arterial PO22

is decreased.is decreased. This may be This may be

due to:due to:1. Decreased 1. Decreased

Atmospheric Atmospheric POPO22::

High AltitudeHigh Altitude

Arterial POArterial PO2 2 decreased due to:decreased due to:

2. Decreased Ventilation:2. Decreased Ventilation: Respiratory Paralysis.Respiratory Paralysis. Bronchial AsthmaBronchial Asthma EmphysemaEmphysema

3. Defective Gas exchange:3. Defective Gas exchange: Pulmonary EdemaPulmonary Edema PneumoconiosisPneumoconiosis

All these cause a All these cause a decreased partial decreased partial pressure of Oxygen pressure of Oxygen and so and so Hypoxic Hypoxic Hypoxia.Hypoxia.

ANEMIC HYPOXIAANEMIC HYPOXIA A decrease in hemoglobin or RBC A decrease in hemoglobin or RBC

count causes decreased Oxygen count causes decreased Oxygen carriage and so hypoxia.carriage and so hypoxia.

Can also be due to Can also be due to CO PoisoningCO Poisoning..• CO combines irreversibly with Hb.CO combines irreversibly with Hb.

Abnormal Hemoglobins such as Abnormal Hemoglobins such as Sickle HbSickle Hb can also cause Anemic can also cause Anemic Hypoxia.Hypoxia.

STAGNANT HYPOXIASTAGNANT HYPOXIA Also called “Ischemic” or “Hypo-perfusion Also called “Ischemic” or “Hypo-perfusion

Hypoxia”.Hypoxia”. Blood flow to tissues is slow or low.Blood flow to tissues is slow or low. The Oxygen reaching the tissues per unit The Oxygen reaching the tissues per unit

time is less.time is less. This situation is seen in:This situation is seen in:

• Heart failureHeart failure• Venous obstructionVenous obstruction

May lead to Adult Respiratory Distress May lead to Adult Respiratory Distress Syndrome if it occurs in the lungs.Syndrome if it occurs in the lungs.

HISTOTOXIC HYPOXIAHISTOTOXIC HYPOXIA Oxygen is available at tissue Oxygen is available at tissue

levelslevels But the cells cannot use it due to But the cells cannot use it due to

a toxic agent.a toxic agent. Seen inSeen in Cyanide poisoning.Cyanide poisoning.

Cyanide inhibits the intracellular Cyanide inhibits the intracellular enzyme, “Cytochrome oxidase”enzyme, “Cytochrome oxidase”

This problem can be treated with This problem can be treated with Methylene Blue.Methylene Blue.• Methylene blue converts Cyan Hb into Methylene blue converts Cyan Hb into

CyanmetHb which is nontoxic.CyanmetHb which is nontoxic.

HISTOTOXIC HYPOXIAHISTOTOXIC HYPOXIA

EFFECTS OF HYPOXIAEFFECTS OF HYPOXIA Severe Hypoxia < 20mm HgSevere Hypoxia < 20mm Hg

• In 10 – 20 seconds: Loss of In 10 – 20 seconds: Loss of consciousness.consciousness.

• In 4 – 5 minutes: DEATHIn 4 – 5 minutes: DEATH Mild Hypoxia:Mild Hypoxia:

• Symptoms are similar to alcoholismSymptoms are similar to alcoholism• Impaired Judgment.Impaired Judgment.• Drowsiness.Drowsiness.• Dulled sensitivity to pain.Dulled sensitivity to pain.

EFFECTS OF HYPOXIAEFFECTS OF HYPOXIA

CYANOSISCYANOSIS

Bluish discoloration of the skin & Bluish discoloration of the skin & mucous membranes.mucous membranes.

Cause: the presence ofCause: the presence of Reduced Reduced Hemoglobin Hemoglobin in the blood.in the blood.

Seen only when the Seen only when the absoluteabsolute amount amount of Reduced Hb is of Reduced Hb is > 5 Grams/dLt> 5 Grams/dLt..

OXYGEN THERAPYOXYGEN THERAPY Given to patients of Hypoxic hypoxia Can be given through:

• A Nasal catheter.• Venturi mask.

Pure Oxygen is not given A mixture of Air & Oxygen is given. Useful in all cases of Hypoxic

Hypoxia.

ASPHYXIAASPHYXIA ““Improper aeration of blood Improper aeration of blood

continued for sometime produces continued for sometime produces two pathological changes:two pathological changes:• Hypoxia : Hypoxia : O O22

• Hypercapnia : Hypercapnia : CO CO22

TYPES OF ASPHYXIATYPES OF ASPHYXIA LOCAL: Due to obstruction of blood LOCAL: Due to obstruction of blood

supply:supply:• Too tight tourniquet, for too long.Too tight tourniquet, for too long.• Blue painful, swollen congested limb.Blue painful, swollen congested limb.

GENERAL:GENERAL:• ACUTE:ACUTE:

Strangulation: Occlusion of tracheaStrangulation: Occlusion of trachea Airtight room: suffocation.Airtight room: suffocation.

GENERAL ASPYXIA: CHRONICGENERAL ASPYXIA: CHRONIC

Chronic Lung Disease.Chronic Lung Disease. Chronic Bronchiectasis.Chronic Bronchiectasis. EmphysemaEmphysema

ASPHYXIA: STAGESASPHYXIA: STAGES I STAGE:I STAGE:

• Violent Respiratory EffortsViolent Respiratory Efforts• Tachypnea & Hyperpnea.Tachypnea & Hyperpnea.• HypoxiaHypoxia• Loss of consciousnesss.Loss of consciousnesss.

II STAGE:II STAGE: Sympathetic dischargeSympathetic discharge• Hypertension & TachycardiaHypertension & Tachycardia• Ventricular fibrillationsVentricular fibrillations• ConvulsionsConvulsions

ASPHYXIA : STAGE IIIASPHYXIA : STAGE III Gasping :Gasping :

• Slow deep inspirationSlow deep inspiration HyporeflexiaHyporeflexia Pupillary DilatationPupillary Dilatation HypotensionHypotension BradycardiaBradycardia Cardiac ArrestCardiac Arrest Death.Death.

What is Hyperbaric What is Hyperbaric Oxygen Therapy?Oxygen Therapy?

entirely enclosed entirely enclosed

chamber chamber breathing oxygen, breathing oxygen,

greater than one greater than one atmosphereatmosphere

Hyperbaric Oxygen TherapyHyperbaric Oxygen Therapy(HBO)(HBO)

Primary therapy for:Primary therapy for:• Decompression sicknessDecompression sickness• Air embolismAir embolism• Carbon monoxide poisoningCarbon monoxide poisoning

Adjunct therapy for:Adjunct therapy for:• Surgical interventionSurgical intervention• AntibioticsAntibiotics

Basic MechanismsBasic Mechanisms Boyle’s LawBoyle’s Law – pressure and volume inversely – pressure and volume inversely

proportional under constant temperatureproportional under constant temperature• By increasing ambient pressure to 2 atm, decreases By increasing ambient pressure to 2 atm, decreases

the volume by ½ the volume by ½ • Therapeutic for bubble forming diseases such as Therapeutic for bubble forming diseases such as

decompression sickness or arterial gas embolismdecompression sickness or arterial gas embolism Henry’s LawHenry’s Law – at a given temperature, the – at a given temperature, the

amount of gas dissolved in solute is directly amount of gas dissolved in solute is directly proportional to the partial pressure of the gas.proportional to the partial pressure of the gas.• By increasing ambient pressure, more oxygen can be By increasing ambient pressure, more oxygen can be

dissolved in the plasmadissolved in the plasma