Effects of Obesity on Dyspnea Perception in Fictitious Patients With Asthma

Abstract

PURPOSE: to compare the perception of dyspnea (POD) during cycle exercise testing and airway challenge to adenosine in non-asmathic (group 1) fictitious asthmatic (group 2), and asthmatic (group 3) obese subjects. METHODS: fictitious asthma was considered when patients have used bronchodilator or corticoid inhaler medication during the last year despite not having a positive bronchial responsiveness testing or elevation of exhaled nitric oxide (NO). Anxiety and depression questionnaires (State-Trait Anxiety Inventory for Adults [STAI] and Beck Depression Inventory [Beck], respectively), body impedance assessment, exhaled NO, spirometry and body plethysmography measurements were performed in all patients. POD was measured in both, adenosine challenge and cycle ergometer testing, using the modified 10-point Borg scale. Finally, incremental exercise testing was conducted on an electronically cycle ergometer (Oxycon Alpha, Viasys). RESULTS: we included 73 patients (group 1=27, group 2=22, group 3=24). Groups were not different by demographic (age, sex, smoking habit) and anthropometric variables. Group 2 had higher Trait anxiety scoring than group 1 (30.9±13.8 vs.19.1±13.4, p<0.05). Pulmonary function testing were similar between groups 1 and 2. During adenosine challenge, POD assessed by the rate of change in Borg score was greater in group 2 than in group 1 (1.95±1.66 vs. 0.57±1.12, p<0.05). Also, relationship between adenosine concentration and changes of the Borg score was greater in group 2 than in group 1 (p=0,051). Likewise, in the exercise testing, the intercept (but not the slope) for work intensity-Borg ratings was significantly lower in group 2 and 3 than in group 1 (13.7±11.6; 12.5±6.7; 30.6±10.8, p<0.001, respectively). Finally, fictitious asthmatic patients had lower intercept and higher slope for oxygen uptake-Borg rating than non-asthmatic patients (p<0.001). CONCLUSIONS: in obese patients, POD during exercise testing is greater in fictitious asthmatic than in non-asthmatic subjects but similar to asthmatic patients. Also, perceptual response to bronchoconstriction is higher in fictitious asthma than in non-asthma patients.