Dyspnea on Exertion in Obese Women: Association with an Increased Oxygen Cost of Breathing

Institute for Exercise and Environmental Medicine, 7232 Greenville Avenue, Dallas, TX 75231, USA.
American Journal of Respiratory and Critical Care Medicine (Impact Factor: 13). 07/2008; 178(2):116-23. DOI: 10.1164/rccm.200706-875OC
Source: PubMed


Although exertional dyspnea in obesity is an important and prolific clinical concern, the underlying mechanism remains unclear.
To investigate whether dyspnea on exertion in otherwise healthy obese women was associated with an increase in the oxygen cost of breathing or cardiovascular deconditioning.
Obese women with and without dyspnea on exertion participated in two independent experiments (n = 16 and n = 14). All participants underwent pulmonary function testing, hydrostatic weighing, ratings of perceived breathlessness during cycling at 60 W, and determination of the oxygen cost of breathing during eucapnic voluntary hyperpnea at 40 and 60 L/min. Cardiovascular exercise capacity, fat distribution, and respiratory mechanics were determined in 14 women in experiment 2. Data were analyzed between groups by independent t test, and the relationship between the variables was determined by regression analysis.
In both experiments, breathlessness during 60 W cycling was markedly increased in over 37% of the obese women (P < 0.01). Age, height, weight, lung function, and %body fat were not different between the groups in either experiment. In contrast, the oxygen cost of breathing was significantly (P < 0.01) and markedly (38-70%) greater in the obese women with dyspnea on exertion. The oxygen cost of breathing was significantly (P < 0.001) correlated with the rating of perceived breathlessness obtained during the 60 W exercise in experiment 1 (r(2) = 0.57) and experiment 2 (r(2) = 0.72). Peak cardiovascular exercise capacity, fat distribution, and respiratory mechanics were not different between groups in experiment 2.
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.

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    • "Less information is available on the mechanical efficiency and endurance of the respiratory muscles in moderate obesity. The finding of an increased O2 cost of breathing, relative to the mechanical work of breathing, in obesity suggests significant mechanical inefficiency as a result of excessive adipose tissue on the chest wall and abdomen [15, 66]. Respiratory muscle function may be compromised in morbid obesity and, in some studies, improves after bariatric surgery [67]. "
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    ABSTRACT: In many parts of the world, the prevalence of obesity is increasing at an alarming rate. The association between obesity, multiple comorbidities, and increased mortality is now firmly established in many epidemiological studies. However, the link between obesity and exercise intolerance is less well studied and is the focus of this paper. Although exercise limitation is likely to be multifactorial in obesity, it is widely believed that the respiratory mechanical constraints and the attendant dyspnea are important contributors. In this paper, we examined the evidence that critical ventilatory constraint is a proximate source of exercise limitation in individuals with mild-to-moderate obesity. We first reviewed existing information on exercise performance, including ventilatory and perceptual response patterns, in obese individuals who are otherwise healthy. We then considered the impact of obesity in patients with preexisting respiratory mechanical abnormalities due to chronic obstructive pulmonary disease (COPD), with particular reference to the effect on dyspnea and exercise performance. Our main conclusion, based on the existing and rather sparse literature on the subject, is that abnormalities of dynamic respiratory mechanics are not likely to be the dominant source of dyspnea and exercise intolerance in otherwise healthy individuals or in patients with COPD with mild-to-moderate obesity.
    Full-text · Article · Oct 2012 · Pulmonary Medicine
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    • "Thirty-seven percent of non-asthmatic obese women reported a higher degree of dyspnea during moderate exercise. This exercise-induced breathlessness seemed to be consequence of an elevated oxygen cost of breathing and may explain the overdiagnosis of asthma in obese patients [24]. Obesity is also associated with mechanical respiratory disorders regarding functional residual capacity and tidal volume that could cause respiratory symptoms [25,26]. "
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    ABSTRACT: Background Epidemiological studies suggest an association between obesity and asthma in adults and children. Asthma diagnosis criteria are different among studies. The aim of this study was to test the influence of asthma definition on the asthma-obesity relationship. Methods In a cross-sectional analysis of 1922 men and women, subjects completed a translated questionnaire from the European Community Respiratory Health Survey and underwent spirometry and a bronchial challenge test. Weight, height and waist circumference were measured. Multiple logistic regression analysis was carried out to assess the association of variables related to obesity and asthma. Asthma was defined either by the presence of symptoms with bronchial hyperresponsiveness (BHR) or by a self-report of a physician-made diagnosis. The following variables were separately tested for associations with asthma: socioeconomic characteristics, schooling, physical activity, smoking status, anthropometry and spirometry. Results No association was detected between asthma confirmed by BHR and obesity indicators, odds ratio (OR) = 1.08 (95% confidence interval: 0.69 - 1.68) for obesity assessed by body mass index ≥ 30 kg/m2; OR = 1.02 (0.74 - 1.40) for obesity assessed by abnormal waist-to-height ratio; and, OR = 0.96 (0.69 - 1.33) for abnormal waist circumference. On the contrary, a previous diagnosis of asthma was associated with obesity, OR = 1.48 (1.01 - 2.16) for body mass index ≥ 30 kg/m2; OR = 1.48 (1.13 - 1.93) for abnormal waist-to-height ratio; and, OR = 1.32 (1.00 – 1.75) for abnormal waist circumference. Female gender, schooling ≥ 12 years and smoking were associated with BHR-confirmed asthma. Physically inactive subjects were associated with a previous diagnosis of asthma. Conclusions Our findings indicate that the relationship between asthma and obesity in epidemiological studies depends on the definition adopted. Certain components of asthma, for instance, symptoms may be more prone to the obesity influence than other ones, like bronchial hyperresponsiveness.
    Full-text · Article · Oct 2012 · BMC Public Health
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    • "In another study, 36.5% of obese adults with a body mass index (BMI) greater than 31 and 28% of "overweight" adults (BMI 27-31) reported dyspnea when walking up hill [39]. In formal cardiopulmonary exercise testing, 37% of healthy obese women had an elevated perception of breathlessness during exercise [40]. "
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    ABSTRACT: Exercise-induced bronchoconstriction (EIB) is described by transient narrowing of the airways after exercise. It occurs in approximately 10% of the general population, while athletes may show a higher prevalence, especially in cold weather and ice rink athletes. Diagnosis of EIB is often made on the basis of self-reported symptoms without objective lung function tests, however, the presence of EIB can not be accurately determined on the basis of symptoms and may be under-, over-, or misdiagnosed. The goal of this review is to describe other clinical entities that mimic asthma or EIB symptoms and can be confused with EIB.
    Full-text · Article · Nov 2009 · Allergy Asthma and Clinical Immunology
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