Pulmonary Function Tests (PFT) Complete Answers

Pulmonary Function Tests (PFT) Complete Answers Primary Function of the Lungs 1. Oxygenation of mixed venous blood. 2. Removal of carbon dioxide from mixed venous blood. Integrity Factors for Lung Function The primary function of the lungs depends on the integrity of: 1. Airway 2. Pulmonary vasculature 3. Respiratory muscles 4. Respiratory control mechanism Purpose of PFTs PFTs help determine: 1. Presence of disease or abnormal lung function. 2. Extent of dysfunction. 3. Extent of impairment/disability. 4. Progression of disease. 5. Nature of physiological disturbance. 6. Effect or course of therapy. 7. Aid in clinical prognosis. Common PFTs Typical pulmonary function tests include: 1. Spirometry: Measures airflow and volumes. 2. Diffusing capacity: Assesses gas exchange capabilities. 3. Body plethysmography: Measures lung volumes and capacity. 4. Bronchial provocation: Test for airway hyperreactivity. 5. Maximal inspiratory/expiratory pressure: Evaluates respiratory muscle strength. 6. Exercise testing: Assesses functional capacity and oxygen uptake. 7. Arterial blood gases: Measures blood oxygen and carbon dioxide levels. Key Concepts in Lung Function - Flow/Volume Relationship: - Peak flow reaches its maximum near total lung capacity. - As lung volume decreases, resistance increases due to intrathoracic airway narrowing. - Airflow Dynamics: - Air flows from higher to lower pressure. - There is a balance between forces that collapse the airways and those that keep them open. Key Parameters - FVC (Forced Vital Capacity): The total amount of air that can be forcibly exhaled after taking a deep breath. - FEV1 (Forced Expiratory Volume in one second): The volume of air expelled in the first second of a forced exhalation. - FEV1:FVC Ratio: The ratio of FEV1 to FVC; used to assess lung function. - PEFR (Peak Expiratory Flow Rate): The maximum speed of expiration. Normal Values - Normal PFT values are based on height, age, and gender. Causes of Abnormal PFT Values # Obstructive Causes: 1. Narrowing: Bronchospasms, inflammation. 2. Material inside airways: Mucous, foreign bodies, tumors. 3. Destruction of lung tissue: Loss of elasticity or external airway support. 4. Atrophy of airway walls: Increased collapsibility. 5. External compression of airways: Tumor or edema. # Restrictive Causes: 1. Intrinsic lung disorders: Interstitial lung disease, sarcoidosis. 2. Extrinsic disorders: Obesity, spinal deformity, pregnancy. 3. Neuromuscular diseases: Generalized weakness, diaphragm paralysis. 4. Poor effort: Inadequate effort during tests resulting in substandard measurements. Reasons for Decreased FVC Potential reasons for decreased FVC include: - Surgical procedures on the lung. - Areas of lung collapse. - Conditions reducing lung expandability (e.g., fibrosis, congestive heart failure). - Obstructive lung diseases. - Issues within the pleural cavity (e.g., enlarged heart, fluid in the pleura, tumors). - Restriction of the chest wall. - Limitations on respiratory muscle effectiveness during inflation/deflation. Reasons for decreased FEV1 ️Obstructive defects; emphysema, chronic bronchitis, asthma. What does it mean if the FVC or FEV1 are reduced in the flow-volume loop? ️There is either obstruction or restriction affecting the breathing. Diffusing Capacity (aka Transfer Test) ️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. What does diffusing capacity determine? ️1. The lungs' ability to transfer gas (oxygen and carbon dioxide). 2. The degree of abnormal alveolar-capillary involvement (emphysema vs asthma or chronic bronchitis). Factors that affect diffusing capacity results ️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. 5. Hemoglobin Causes for REDUCTION of diffusion capacity ️1. Emphysema 2. Pulmonary fibrosis 3. Loss of parenchyma, space occupying lesions (tumor), pulmonary edema.