Pulmonary Function Tests (PFT) 2024
Causes for INCREASED diffusion capacity - ANSWER-1. Polycythemia
2. Pulmonary hemorrhage
3. Mild-moderate exercise
4. Asthmatic during airflow limitation (increase capillary blood volume)
Causes for REDUCTION of diffusion capacity - ANSWER-1. Emphysema
2. Pulmonary fibrosis
3. Loss of parenchyma, space occupying lesions (tumor), pulmonary edema.
4. Obesity
5. Extreme exercise: decreased capillary transit time.
Causes of abnormal values: Obstruction - ANSWER-1. Narrowing: bronchospasms,
inflammation
2. Material inside airways: mucous, foreign bodies, tumor
3. Destruction of lung tissue: loss of elasticity or external support of airways.
4. Atrophy or airway wall: increased collapsibility
5. External compression of airway: tumor, edema
Causes of abnormal values: Restriction - ANSWER-1. Intrinsic lung disorders: interstitial
lung disease, sarcoid
2. Extrinsic disorders: obesity, spinal deformity, pregnancy
3. Neuromuscular disease: generalized weakness, diaphragm paralysis, etc.
4. Poor effort
Common PFTs - ANSWER-1. Spirometry
2. Diffusing capacity
3. Body plethysmography
4. Bronchial provocation
5. Maximal inspiratory/expiratory pressure
6. Exercise testing
7. Arterial blood gasses
Diffusing Capacity (aka Transfer Test) - ANSWER-The measurement of the transfer of a
gas (CO) across the alveolar-capillary membrane.
In a normal functioning lung, the primary limiting factor of carbon monoxide is the status
of the alveolar-capillary membrane.
Factors that affect diffusing capacity results - ANSWER-1. Ventilation: affects amount of
CO.
2. Perfusion: amount of blood in the lungs.
3. How well ventilation and perfusion match.
4. Integrity of the alveolar-capillary interface.
