Interpretation of Pulmonary Function Tests Flashcards
What is tidal volume?
- Volume of air inspired and expired with each normal breath
What is forced vital capacity (FVC)?
- Amount of air that can be forcefully expelled beginning with the lungs completely full and blowing maximally until the lungs are as empty as possible
What is forced expiratory volume in first second (FEV1)?
- Amount of air expelled during the first second of the FVC maneuver
What is the residual volume?
- Volume of air remaining in lungs after most forceful expiration
What is the total lung capacity?
- Maximum volume to which the lungs can be expanded with inspiration
What does the spirometry with flow volume curves or loops measure?
- FVC
- FEV1
- FEV1/FVC ratio
What does the FEV1/FVC ratio tell?
- Restrictive vs obstructive lung disease
What measures lung volumes and capacities?
- Most commonly plethysmography
- Looks at TLC and RV
What is the DLCO?
- Test to measure the gas exchange through alveolar wall
How is a DLCO test done?
- Patient inhales a small amount of CO for 10 seconds then exhales quickly
- The concentration of CO is measured and the DLCO is calculated
What is bronchodilator therapy?
- Used only in obstructive lung disease to determine if airway obstruction is reversible
What is a positive bronchodilator therapy?
- If there is a >12% increase in FEV1 or FVC and an absolute volume increase of >200ml
- Positive means asthma
What happens if the bronchodilator test is negative but asthma is still suspeced?
- Use a bronchoprovocation, specifically, give methacholine to close up airways
What is a positive methacholine challenge?
- If there is a >20% reduction in FEV1 at or before administration of inhaled methacholine
What does obstruction lung disease look like on flow volume curves?
- Concave or scooping pattern
What does restrictive lung disease look like on flow volume curves?
- Peaked, steeple, or witch’s hat pattern
What are some causes of obstructive lung disease?
- COPD
- Asthma
- Bronchiectasis
- Bronchiolitis
What are some causes of restrictive lung disease?
- Abnormalities of chest wall or pleura
- Drugs
- Interstitial lung disease
- Neuromuscular disease
What are the spirometry results of obstructive lund disease?
- FEV1 <80% predicted
- FVC can be normal or reduced
- FEV1/FVC is <0.70
- Flow volume curve with scooped or concave pattern
What are the lung volumes and capacities of obstructive lund disease?
- Increased total lung capacity due to air trapping
- Increased residual volume from air trapping
What are the DLCO results of obstructive lung disease?
- Could be normal or low
- In emphysema, DLCO will be low
- In asthma or bronchitis, DLCO will be normal
What are the spirometry results for restrictive lung disease?
- FEV1 is normal or mildly reduced
- FVC <80% predicted
- FEV1/FVC ratio is >0.70
- Flow volume curve is peaked, steeple, or witch’s hat pattern
What are the lung volumes and capacities of restrictive lund disease?
- Decreased total lung capacity
- Decreased residual volume
What are the DLCO results in restrictive lungdisease?
- Could be low or normal
- In ILD, tends to be low
- In neuromuscular or chest wall abnormalities, tends to be normal
What shows a mixed PFT?
- If the FEV1/FVC ratio is low and the TLC is low <5 percentile of predicted
