Pulmonary function testing in obesity, pregnancy, and extremes of body habitus.

Knowing the effect body habitus can have on pulmonary function is important when there is a concern of an underlying respiratory impairment. The pattern of PFT abnormaLities can help distinguish an underlying ventilatory defect as deriving from the body habitus or from a second process. There are limitations, however. Individuals who are obese and have the same weight will likely have different degrees of impairment, for instance. It then becomes difficult to predict the effect body habitus will have in each patient. It therefore is vitally important to evaluate these patients using other clinical data to decide whether the ventilatory defect can be explained by body habitus alone. It also should be noted that some of the more subtle physiologic changes that occur in these conditions are still not fully understood. Hopefully, further insight into these changes can be obtained with further investigation. Certainly, better predictors of the impact of the patient's weight, abdominal girth, and other anthropomorphic data on PFT results would be extremely helpful in the evaluation of these individuals.