PURPOSE: Exertional dyspnea is a common complaint in obese patients. Dyspnea may be mistakenly attributed to asthma in non-smokers and COPD in smokers. Spirometry is useful in excluding obstructive ventilatory defect i.e. asthma, COPD. The static lung volumes are helpful in confirming obesity induced lung restriction. It is critical for Pulmonologist to recognize and report obesity related restrictive PFT patterns to avoid missed diagnosis and misguided therapy. The purpose of the study was to characterize the PFT restrictive patterns in obesity and the utility of spirometry in excluding obstructive airways disease as a cause of dyspnea in obese
METHODS: We reviewed PFTs of all obese patients (BMI>30) during the period from 1/09 to 12/10. Patients with underlying comorbid lung diseases with FEV1/FVC < 70% and DLCO <70% were excluded
RESULTS: Of 281 patients, 70(25%) were males 211(75%) females. Age, Median 55 yrs (range, 14-90) Smokers, 73(26%); Non-smokers, 208(74%). Ethnicities: African American-171(61%), Hispanic-84(30%), Caucasian-23(8%), Asian-3. The pre-PFT clinical diagnoses were: Asthma-100, COPD-50, unexplained dyspnea-47, Pre-Surgery-34, Sleep apnea-7. Patients were stratified based as BMI: There were 113 (40%) patients were obese (BMI of 30-35); 76(27%) with moderate obesity (BMI >35-40) and 92(33%) with morbid obesity, BMI >40. The reduction in lung volumes was most severe with ERV followed by FRC, VC and TLC. ERV was reduced in 90% (severely reduced in 61%), FRC in 55%, TLC in 31% and VC in 44% of patients. The reduction in lung volumes, especially ERV correlated with BMI
CONCLUSIONS: Obesity produces a characteristic pattern of Restrictive ventilatory defect dependent on BMI. Static lung volumes help explain obesity as the cause of clinically unexplained dyspnea in many. spirometry is helpful in excluding clinically suspected asthma and COPD.
CLINICAL IMPLICATIONS: PFT is indicated in all obese patients with dyspnea even in the absence of clinical lung disease. It is critical for the Pulmonologist to recognize the typical restrictive ventilatory defect pattern and report to the primary care physicians. This will help avoid missed diagnosis and misguided therapy.
DISCLOSURE: The following authors have nothing to disclose: Qammar Abbas, Shravan Kooragayalu, Viswanath Vasudevan, Vilas Vasudevan, Saleem Shahzad, Farhad Arjomand, Scott Reminick
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