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pulmonary physiologic test of the month: Shawn D. Aaron, Robert E. Dales, and Pierre Cardinal How Accurate Is Spirometry at Predicting Restrictive Pulmonary Impairment? Chest 1999; 115: 869-873 [Abstract] [Full text] [PDF]

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Airway obstruct

Mehmet POLATLI   (14 February 2000)

Airway obstruct 14 February 2000
Mehmet POLATLI, MD Assistant Professor Send letter to journal: Re: Airway obstruct mpolatli{at}adu.edu.tr Mehmet POLATLI	I read with great interest the article by Aaron et al titled as "How accurate is spirometry at predicting restrictive pulmonary impairment?". The addition of lung volume measurements to spirometry adds additional costs and time for both physicians and patients. Thus, spirometry must be carefully interpreted and must include both forced and slow maneuvers. In this paper, the study design include only forced expiratory maneuvers so as low as 41 % “positive predictive value” for restrictive disease with classic spirometric restrictive pattern is not surprising. The probability of restrictive defect has been reported to be inversely correlated with FVC. Slow vital capacity and forced vital capacity are usually similar except in obstructive airway diseases. In these disorders forced expiration often causes dynamic collapse of the airways which causes air trapped behind the obstruction, elevated RV and decreased FVC. So I suppose that the result of such a low positive predictive value may be influenced by the method of spirometric measurement in this study which does not include slow vital capacity. On this account, measurement of slow vital capacity can further reduce the number of patients having low VC and must be paid attention to it.