Dyspnea on exertion is prevalent in otherwise healthy obese women, which seems to be strongly associated with an increased oxygen cost of breathing. Exercise capacity is not reduced in obese women with dyspnea on exertion.

We tested the hypothesis that the exercise ventilatory response (EVR) differed between otherwise healthy obese women with and without dyspnea on exertion (DOE). In fourteen obese women we determined EVR (defined as slope of VE vs. VCO2) during cycling at 30W and 60W, O2 cost of breathing (from measurements of VO2 and VE at rest and during eucapnic voluntary hyperpnea at 40 and 60 L/min; slope was calculated in ml/L) and O2 uptake of the respiratory muscles (VO2RESP) at 30W and 60W (calculated from O2 cost multiplied by VE at each exercise level). Subjects were grouped according to RPB (Borg 0–10) during cycling at 60W (Control, n = 7, RPB ≤ 2; DOE, n = 7, RPB ≥ 4). Age, ht, wt and % body fat were similar between groups. RPB and O2 cost of breathing were significantly higher in DOE than Control (p<0.05). The EVR at 30W and 60W was similar between groups. VO2RESP was significantly higher in DOE than Control at 30W and 60W (30W 66±19 and 37±6, 60W 115±44 and 63±12 ml/min, respectively; p<0.02). There were significant correlations between RPB at 60W and VO2RESP at 30W and 60W (30W r = 0.91, 60W r = 0.88; p<0.01). The EVR did not differ between groups, and hence did not appear to account for the DOE. However, VO2RESP during exercise was significantly higher in obese women with DOE, suggesting that VO2RESP may play an important role in DOE. Support: American Heart Association, The King Foundation, The Cain Foundation, Presbyterian Hospital of Dallas

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