Pulmonary Function Pulmonary Function TestsTests

Classification

Obstructive lung disease(pattern):

COPD,Asthma,Bronchiolitis ,Bronchiectasis Restrictive lung disease(pattern)

ILD,NMD,…

Pulmonary Function Tests Spirometry Body Plethysmography (Body Box) Body Box + Dlco Metacholine Challenge text(MCT) Cardiopulmonary Exercise Test

(Ergospirometry)

SpirometrySpirometry

Spirometry Flow Loop- Normal

Flow Volume Loop

What information does a spirometer yield?

A spirometer can be used to measure the following: FVC and its derivatives (such as FEV1, FEF 25-75%) Peak expiratory flow rate Maximum voluntary ventilation (MVV) Slow VC IC, IRV, and ERV Pre and post bronchodilator studies

Information Provided by the Spirometer

The ratio of FEV1/FVC is normally between 0.7 and 0.8. Values below 0.7 are a marker of airway obstruction, except in older adults where values 0.65–0.7 may be normal.

In people over 70 years old, the FEV1/FVC ratio may need to be lowered to 0.65 as a lower limit of normal. conversely, in people under 45, using a ratio of 0.7 may result in under-diagnosis of airway obstruction.

INTERPRETATIONINTERPRETATION

Interpretation of spirometry involves looking at the absolute values of FEV1, FVC, and FEV1/FVC,

comparing them with predicted values, and examining the shape of the spirograms.

Patients should complete three blows that are consistent and within 5% of each other—many electronic spirometers automatically provide this information.

Spirometry Quality

Upper Airway Obstruction

Bronchodilator Reversibility Testing Bronchodilator reversibility testing is best done as a

planned procedure, as it is time consuming. If the patient is undiagnosed and on no therapy, acute reversibility can be assessed on the first visit.

Short-acting bronchodilators need to be withheld for at least 4 hours prior to testing, and long-acting bronchodilators for 12 hours. Recent treatment with inhaled glucocorticosteroids can also reduce bronchodilator reversibility because the pre-bronchodilator FEV1 may improve significantly with

Inhaled glucocorticoid therapy.

Reversibility testing

Spirometry should be undertaken when the patient is clinically stable and free from a respiratory tract infection.

Short-acting bronchodilators should be withheld for the previous 6 hours, long-acting bronchodilators for 12 hours, and sustained release theophylline for 24 hours.

FEV1/FVC should be measured before and 15-20 minutes after bronchodilator is given.

The bronchodilator should be given by metered dose inhaler, ideally through a spacer. A nebulizer may be used but generally larger doses are delivered by this route.

The dose administered should be high on the dose-response curve.

Possible dose protocols include 400 μg salbutamol, up to 160 μg ipratropium, or the two combined.

Pre-Post Bronchodilator

ATS recommends a positive response is > 12% improvementin FEV1

Patterns of Spirometric Curves

NORMAL: FEV1 and FVC above 80% predictedFEV1/FVC ratio above 0.7OBSTRUCTIVE: FEV1 below 80% predictedFVC can be normal or reduced – usually to a lesser

degree than FEV1FEV1/FVC ratio below 0.7RESTRICTIVE: FEV1 below 80% predictedFVC below 80% predictedFEV1/FVC ratio normal - above 0.7.

Spirometry (Indication)

1- Evaluate dyspnea

2- Detect Pulmonary Diseases

3- Monitoring of Treatment

4- Evaluate Preoperative Risk

5- Evaluate respiratory impairment

6- Surveillance for occupational lung diseases

Spirometry (Contraindaction)1- Hemoptysis

2- Pneumothorax

3- Recent MI (UA)

4- Aortic Aneurysm

5- Cerebral Aneurysm

6- Recent eye surgery

7- Recent thoracic & abdominal

surgery

Body plethysmographyBody plethysmography

Body plethysmography

The most accurate way The patient sits inside a fully

enclosed rigid box and breath through mouthpiece connected through a shutter to the internal volume of the box

while breathing in and out again into a mouthpiece. The volume of all gas within the thorax can be measured by Changes in pressure inside the box and allow determination of the lung volume( Boyles Law)

These parameters will be evaluated by Body Box:These parameters will be evaluated by Body Box:

Residual volume (RV) Tidal volume (TV) Total Lung Capacity (TLC) Expiratory reserve volume (ERV) Inspiratory Reserve Volume (IRV) Inspiratory capacity (IC) Functional residual capacity (FRC) Vital Capacity (VC)

Diffusing Capacity(Dlco)

Diffusing capacity of lungs for CO

Measures ability of lungs to transport inhaled gas from alveoli to pulmonary capillaries

Depends on:

- alveolar—capillary membrane

- hemoglobin concentration

- cardiac output

Diffusing Capacity

Decreased DLCO (<80% predicted)

Obstructive lung disease

Parenchymal disease

Pulmonary vascular disease

Anemia

Increased DLCO (>120-140% predicted)

Asthma (or normal)

Pulmonary hemorrhage

Polycythemia

Left to right shunt

DLCO — Indications

Emphysema

Evaluation and severity of restrictive lung disease

Early stages of pulmonary hypertension

Methacholine Challenge Test

Bronchoprovocation testing

INDICATIONS: accurate diagnosis of bronchial asthma assessment of the response to asthma

therapy identification of triggers for environmental

or occupational asthma.

Methacholine challenge

A series of methacholine chloride solutions are prepared, ranging from approximately 0.05 mg/mL to 25 mg/mL being administered by nebulizer.

After inhalation of the aerosol, the FEV1 is measured at 1, 3, 5, and 10 minutes, and the concentration is increased one step until a 20 percent decrease in FEV1 or a 35 or 40 percent decrease in specific airways conductance (SGaw) is observed

The dose that provokes a 20 percent drop in FEV1 is referred to as the PC20. Generally, a PC20 of 8 mg/ml methacholine or less is considered a positive test

CPET(Ergospirometry)CPET(Ergospirometry)

Indications for Exercise Testing

Diseases that affect the heart, lungs, circulation, or blood

shortness of breath that otherwise cannot be determined at

rest or through conventional lung function testing

abnormal blood pressure response to exercise

poor circulation

exercise capacity and anaerobic threshold of the individual

Follow responses to therapy in patients with cardiopulmonary disease

COPD ILD PVD Obesity Deconditioned

Heart failure

V’O2,peak Reduced Reduced Reduced Reduced

Normal

Reduced Reduced

LT Indeter.

Nor. Low

Normal Low

Low Low Normal Low

Low

VE,reserve Reduced or none

Reduced or Normal

Normal Normal Normal Normal

HRR normal increased

normal increased

normal normal normal Reduced or Normal

O2 pul .pa Reduced Reduced Reduced normal Reduced Reduced

Fall in SaO2

Present Absent

Present Present Absent Absent Absent