Dyspnea on Exertion in Nonobese and Obese Patients

Abstract

PURPOSE: Dyspnea on exertion (DOE) is a common symptom in otherwise healthy obese individuals and in patients with serious illness. Whether obese patients have an exaggerated rating of breathlessness (RPB) as compared with nonobese patients is unknown. In a retrospective analysis, we investigated RPB in nonobese and obese patients who were referred for clinical cardiopulmonary exercise testing (CPET) due to unexplained DOE. METHODS: Data from 112 patients were separated into nonobese (BMI < 30; n = 28; 20 F) and obese (BMI ≥ 30; n = 47; 24 F) groups. All patients cycled at two individualized constant load work rates (one easy & one harder) for 4-6 mins, followed by a peak exercise test. Constant load work rates were set based on the patient’s symptoms and physical activity habits. During the last minute of each constant load exercise bout, patients’ RPBs were obtained (Borg scale 0-10). Groups were compared by independent t test and relationships between variables were examined by regression analysis. RESULTS: BMI was 22 ± 2 kg/m2 in the nonobese (62 ± 9 kg) and 36 ± 4 kg/m2 in the obese (103 ± 16 kg) patients (mean ± SD; p < 0.001). Age was not different between groups (50 ± 20 yr vs 57 ± 12 yr). Work rates were not significantly different between the nonobese and obese patients at the lower (29 ± 19 W vs 24 ± 14 W) or higher constant load work rates (59 ± 35 W vs 49 ± 27 W). Exercise intensity was also not different between groups at the lower (53 ± 11 vs 56 ± 13% of peak O2 uptake) or higher work rates (74 ± 11 vs 72 ± 11%). RPB was significantly (p = 0.05) greater in the obese patients (2.3 ± 1.4 vs 3.3 ± 2.2) at the lower work rate, but not at the higher work rate (4.4 ± 1.8 vs 4.9 ± 2.2). Maximal exercise capacity was higher in the nonobese patients (77 ± 24 vs 58 ± 21% predicted). There was no significant relationship between RPB and BMI within either group. However, there was a significant (p < 0.001) association between RPB and ratings of perceived exertion (RPE) in the nonobese (r = 0.68 & 0.82 for lower & higher constant work rates) and the obese (r = 0.87 & 0.81) patients. CONCLUSIONS: Obesity appears to have a significant effect on breathlessness at lower work rates in this mixed patient population, and should be considered when assessing breathlessness in patients. Supported by NIH R01 HL096782, King Charitable Foundation Trust, and Texas Health Presbyterian Hospital Dallas