Spirometric Terms
Accounting for approximately 75% of vital capacity, this subdivision represents the largest volume of gas that can be inspired from resting expiratory level
What is Inspiratory Capacity
Although a low FEV1/FVC ratio is the key to defining obstruction, ATS-ERS guidelines also define obstruction in the subset of pt.'s exhibiting these three characteristics.
What are normal FEV1/FVC, low VC, normal TLC
Poor patient effort may result in inspiratory flow patterns similar to this type of obstruction
What is variable extrathoracic obstruction
This procedure requires the patient to inspire as forcefully as possible from the point of maximal expiration
What is Forced Inspiratory Vital Capacity
Diagnosis of an obstructive pattern based on spirometry should focus on these three variables
What are vital capacity, FEV1, and FEV1/FVC
This type of disease process may show normal or greater than normal peak flows with linear decreases in flow vs. volume
What is restrictive
The volume of gas expired over a given time interval from the beginning of the FVC maneuver
What is FEVT (where the time interval, T, is stated as a subscript of FEV)
This value may be a useful surrogate measurement in obstructed patients who have difficulty with prolonged exhalation
What is FEV6
Airway obstruction associated with abnormality of the muscular control of the posterior pharynx and larynx sometimes produces this type of pattern on the flow volume curve
What is sawtooth
Very steep flows produce flow-volume loops analogous to an "ant hill" or "witch's hat" in this disease pattern
What is restrictive