The effects of body weight on airway calibre

King, Gregory G.; Brown, Nathan J.; Diba, Chantale; Thorpe, C. William; Munoz, P.; Marks, Guy B.; Toelle, Brett G.; Ng, Kitty; Berend, Norbert; Salome, Cheryl M.

doi:10.1183/09031936.05.00104504

Cited by 171 publications

(130 citation statements)

References 29 publications

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“…The difference in reactance between obese and non-obese subjects is in keeping with other evidence that suggests that there are differences in respiratory system mechanics that are not reflected in FEV 1 . 12 Obesity and asthma Our findings suggest a mechanism whereby asthma might be induced in obese subjects, in the absence of any direct effects of obesity on AHR. It has been suggested that the excess wheezing illness in the obese is not due to 'real' asthma, but is simply a misdiagnosis of excessive breathlessness.…”

Section: Perception Of Dyspneamentioning

confidence: 74%

“…10,11 Previous studies of the association between obesity and AHR have measured effects on sensitivity. [3][4][5][6][7] However, obesity is more likely to affect the maximal response, because obesity reduces operating lung volume 12 and breathing at low operating lung volumes is known to induce increased maximal airway narrowing in non-asthmatic subjects. 13,14 The effect of low lung volume on maximal airway narrowing in obese, non-asthmatic subjects has not been reported.…”

Section: Introductionmentioning

confidence: 99%

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Effect of obesity on breathlessness and airway responsiveness to methacholine in non-asthmatic subjects

et al. 2007

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Background: Obesity is associated with increased prevalence and incidence of asthma, but the mechanism is unknown. Obesity reduces lung volumes, which can increase airway responsiveness, and increases resistive and elastic work of breathing, which can increase dyspnea. Objective: To determine if the intensity of dyspnea due to airway narrowing or if airway responsiveness is increased in obese, non-asthmatic subjects. Subjects: Twenty-three obese (BMI (body mass index) X30 kg m À2 ) and 26 non-obese (BMI o30 kg m À2 ) non-asthmatic subjects, aged between 18 and 70 years. Methods: High-dose methacholine challenge was used to determine the sensitivity and the maximal response to methacholine. Respiratory system resistance (Rrs) and reactance were measured, using the forced oscillation technique, as indicators of resistive and elastic loads during challenge. Perception of dyspnea was measured by the Borg score during challenge. Static lung volumes were measured by body plethysmography. Results: Static lung volumes were reduced in the obese subjects. There were no significant differences in the sensitivity or maximal response to methacholine between obese and non-obese subjects. The magnitude of change in Rrs was similar in both groups, but obese subjects had more negative reactance after challenge (P ¼ 0.002) indicating a greater elastic load. The intensity of dyspnea was greater in obese subjects (P ¼ 0.03). Conclusions: Obesity reduces lung volumes, but does not alter the sensitivity or maximal response to methacholine. However, obese subjects have enhanced perception of dyspnea, associated with greater apparent stiffness of the respiratory system, and may therefore be at greater risk of symptoms.

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Section: Perception Of Dyspneamentioning

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Effect of obesity on breathlessness and airway responsiveness to methacholine in non-asthmatic subjects

et al. 2007

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“…Other mechanisms have been suggested, including the possibility that abdominal fat deposition leads to a redistribution of blood to the thoracic compartment that reduces vital capacity (Harik-Khan et al, 2001). In addition, high amounts of FM may be related to a greater degree of airway narrowing than would be expected on the basis of reduced lung volume alone, although the mechanisms remain uncertain (King et al, 2005). However, obesity is a complex disorder and the effects of excess adipose tissue on pulmonary function may be influenced by the location of excess fat deposits as well as by their extent.…”

Section: Discussionmentioning

confidence: 99%

Changes in thoracic gas volume with air-displacement plethysmography after a weight loss program in overweight and obese women

et al. 2007

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Objective: This study was designed to compare measured and predicted thoracic gas volume (V TG ) after weight loss and to analyze the effect of body composition confounders such as waist circumference (WC) on measured V TG changes. Design: Prospective intervention study. Setting: Outpatient University Laboratory, Lisbon, Portugal. Subjects: Eighty-five overweight and obese women (body mass index ¼ 30.073.5 kg/m 2 ; age ¼ 39.075.7 years) participating in a 16-month university-based weight control program designed to increase physical activity and improve diet. Methods: Body weight (Wb), body volume (Vb), body density (Db), fat mass (FM), percent fat mass (%FM) and fat-free mass (FFM) were assessed by air-displacement plethysmography (ADP) at baseline and at post-intervention (16 months). The ADP assessment included a protocol to measure V TG and a software-based predicted V TG . Dual-energy X-ray absorptiometry (DXA) (Hologic QDR 1500) was also used to estimate FM, %FM and FFM. Maximal oxygen uptake (VO 2 max) was assessed with a modified Balke cardiopulmonary exercise testing protocol with a breath-by-breath gas analysis. Results: Significant differences between the baseline and post-weight loss intervention were observed for body weight and composition (Vb, Db, %FM, FM and FFM), and measures of V TG (measured: D ¼ 0.2 l, Po0.001; predicted: D ¼ 0.01 l, Po0.010) variables. Measured V TG change was negatively associated with the change in the WC (P ¼ 0.008), controlling for VO 2 max and age (P ¼ 0.007, P ¼ 0.511 and P ¼ 0.331). Linear regression analysis results indicated that %FM and FM using the measured and predicted V TG explained 72 and 76%, and 86 and 90% respectively, of the variance in %FM and FM changes using dual-energy x-ray absorptiometry. Conclusions: After weight loss, measured V TG increased significantly, which was partially attributed to changes is an indicator of body fat distribution such as WC. Consequently, measured and predicted V TG should not be used interchangeably when tracking changes in body composition. The mechanisms relating the reduction of an upper body fat distribution with an increase measured V TG are worthy of future investigation.

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“…In obese males, airway narrowing seems to be greater than what would be expected to result from reduced lung volume alone. (20) In populationbased studies, asthma has been associated with obesity, especially in females. (21) In individuals with asthma, the increase in RV is greater than the decrease in FVC, due to a simultaneous increase in TLC.…”

Section: Discussionmentioning

confidence: 99%

Predizendo redução da CPT em pacientes com CVF reduzida e relação VEF1/CVF normal ou elevada

et al. 2010

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Objective: To use clinical and spirometry findings in order to distinguish between the restrictive and nonspecific patterns of pulmonary function test results in patients with low FVC and a normal or elevated FEV 1 /FVC ratio. Methods: We analyzed the pulmonary function test results of 211 adult patients submitted to spirometry and lung volume measurements. We used the clinical diagnosis at the time spirometry was ordered, together with various functional data, in order to distinguish between patients presenting with a "true" restrictive pattern (reduced TLC) and those presenting with a nonspecific pattern (normal TLC). Results: In the study sample, TLC was reduced in 144 cases and was within the normal range in 67. The most common causes of a nonspecific pattern were obstructive disorders, congestive heart failure, obesity, bronchiolitis, interstitial diseases, and neuromuscular disorders. In patients given a working diagnosis of pulmonary fibrosis, pleural disease, or chest wall disease, the positive predictive value (PPV) for restriction was ≥ 90%. In males, an FVC ≤ 60% of predicted had a PPV for restriction of 98.8%. In females, the restrictive pattern was found in 84.4% of those with an FVC ≤ 50% of predicted. A difference of ≥ 0% between the FEV 1 % and the FVC% had a PPV for restriction of 89.5%. After performing logistic regression, we developed a point scale for predicting the restrictive pattern. Conclusions: In many patients with reduced FEV 1 , reduced FVC, and a normal FEV 1 /FVC ratio, the restrictive pattern can be identified with confidence through the use of an algorithm that takes the clinical diagnosis and certain spirometry measurements into account.Keywords: Spirometry; Airway resistance; Respiratory function tests; Vital capacity. ResumoObjetivo: Utilizar os dados clínicos e espirométricos para distinguir entre os padrões restritivo e inespecífico dos resultados dos testes de função pulmonar em pacientes com CVF reduzida e relação VEF 1 /CVF normal ou elevada. Métodos: Foram avaliados resultados de testes de função pulmonar de 211 pacientes adultos submetidos à espirometria e a medidas de volumes pulmonares. O diagnóstico clínico na solicitação do exame e diversos dados funcionais foram utilizados para diferenciar pacientes com o padrão restritivo "verdadeiro" (CPT reduzida) daqueles com o padrão inespecífico (CPT normal). Resultados: Na amostra estudada, a CPT estava reduzida em 144 casos e estava dentro da faixa normal em 67. As causas mais comuns do padrão inespecífico foram doenças pulmonares obstrutivas, insuficiência cardíaca congestiva, obesidade, bronquiolite, doenças intersticiais e doenças neuromusculares. Em pacientes com hipótese diagnóstica de fibrose pulmonar, doenças pleurais ou doenças da parede torácica, o valor preditivo positivo (VPP) para restrição foi ≥ 90%. Em homens, a CVF ≤ 60% do previsto teve um VPP para restrição de 98,8%. Em mulheres, o padrão restritivo foi encontrado em 84,4% daquelas com CVF ≤ 50% do previsto. Uma diferença entre VEF 1 % e CVF% ≥ 0% t...

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The effects of body weight on airway calibre

Cited by 171 publications

References 29 publications

Effect of obesity on breathlessness and airway responsiveness to methacholine in non-asthmatic subjects

Effect of obesity on breathlessness and airway responsiveness to methacholine in non-asthmatic subjects

Changes in thoracic gas volume with air-displacement plethysmography after a weight loss program in overweight and obese women

Predizendo redução da CPT em pacientes com CVF reduzida e relação VEF1/CVF normal ou elevada

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