Respiratory Symptom Perception Differs in Obese Women With Strong or Mild Breathlessness During Constant-Load Exercise

Abstract

responses. 1,2 Dyspnea on exertion (DOE) is a very common symptom in obesity. 3 In one large epidemiologic survey, 80% of obese adults reported breathlessness after climbing two fl ights of stairs compared with 16% of nonobese control subjects. 4 Another survey (N 5 16,692) found that 36% of obese adults experienced dyspnea when walking up a hill. 5 Our laboratory D yspnea is defi ned as a subjective experience of breathing discomfort that consists of qualitatively distinct sensations that vary in intensity; these sensations originate from interactions among multiple physiologic, psychologic, social, and environmental factors and may induce secondary physiologic and behavioral Background: During constant-load exercise, some otherwise healthy obese women report substantially more dyspnea on exertion (DOE) than do others. The objective of this study was to investigate whether qualitative differences exist between the sensations of dyspnea felt by these women. Methods: Seventy-eight women were categorized based on their ratings of perceived breathlessness (RPBs) (Borg 0-10 scale) after 6 min of 60-W cycling. Thirty-four women rated RPB Ն 4 ( 1 DOE) (34 Ϯ 7 years, 36 Ϯ 5 kg/m 2 BMI), and 22 women rated RPB Յ 2 ( 2 DOE) (32 Ϯ 7 years, 37 Ϯ 4 kg/m 2 BMI). Twenty-two women rated RPB as 3 (RPB 5 3) (34 Ϯ 7 years, 34 Ϯ 4 kg/m 2 BMI) and were grouped separately to allow for a better delineation of the 1 DOE and the 2 DOE groups. After the exercise test, subjects were asked to pick three of 15 statements that best described their respiratory sensations. Results: The 1 DOE and the 2 DOE groups were characterized differentially ( P , .05) by the respiratory clusters "Breathing more" (82% of 2 DOE vs 41% of 1 DOE), "Shallow" (36% vs 6%), and "Heavy" (14% vs 53%). All four descriptors in the cluster "Work/Effort" were chosen more frequently by women in the 1 DOE group than by women in the 2 DOE group. Although relative exercise intensity was higher in the 1 DOE women (75% Ϯ 13% vs 67% Ϯ 10% of oxygen uptake at peak exercise, 41 Ϯ 10 L/min vs 31 Ϯ 8 L/min as % maximal voluntary ventilation, 83% Ϯ 7% vs 76% Ϯ 7% of peak heart rate), none of these variables was signifi cantly associated with RPB. Conclusions: Not only is the intensity of dyspnea signifi cantly different between the 1 DOE and the 2 DOE groups, but so are the self-reported qualitative aspects of their dyspnea. Women in the 1 DOE group reported an increased sensation of the work of breathing relative to women in the 2 DOE group, which may be associated with the elevated RPB.CHEST 2014; 145(2):361-369Abbreviations: DOE 5 dyspnea on exertion; HR 5 heart rate; MVV 5 maximal voluntary ventilation; RPB 5 rating of perceived breathlessness; co 2 5 CO 2 output; e 5 minute ventilation; o 2 5 oxygen uptake; o 2 peak 5 oxygen uptake at peak exercise; V t 5 tidal volume

Exertional dyspnoea in obesity

“…However, our studies in otherwise healthy obese adults show that the majority do not show cardiorespiratory deconditioning [7,18,40,[56][57][58]. This discrepancy may be due to two factors.…”

“…These results would suggest that breathlessness is dependent only on minute ventilation (and V′O 2 ). However, as we have shown in several studies, not all obese adults experience dyspnoea on exertion [7,24,43,44,58]. In our studies, the prevalence of DOE in otherwise healthy obese adults is ∼37-44%, as defined by a rating of perceived breathlessness (RPB) ⩾4 (i.e.…”

“…A familiarisation test would be best for this but time constraints for a busy clinical laboratory does not allow for this type of testing. [7,8] and unpublished data.…”

“…This practice should be avoided especially in women, as data from hydrodensitometry and dual-energy X-ray absorptiometry show that body fat percentage values are much higher than BMI in women [7,8,17]. Although obese adults exhibit much greater fat mass than non-obese adults (both in absolute values and relative to total body weight) the relative distribution of fat can be remarkably similar [18,19].…”

“…Except for the perceptual measurement, none of the other above mentioned comprehensive assessments showed any marked significant differences between the groups of obese women with and without DOE [7,8]. The groups differed in their responses to the qualitative aspect of their dyspnoea; namely an increased sensation of the work of breathing [7]. Interestingly, however, the oxygen cost of breathing is similar between the groups [69] and retrospective analysis ( figure 5).…”