Dysanapsis ratio as a predictor for expiratory flow limitation

Smith, Joshua R.; Rosenkranz, Sara K.; Harms, Craig A.

doi:10.1016/j.resp.2014.04.001

Cited by 41 publications

(52 citation statements)

References 20 publications

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“…Others have shown that aerobic fitness does not predict who does and does not develop EFL (Smith et al . ), and we have argued that women develop EFL more often than men (Guenette et al . ).…”

Section: Discussionmentioning

confidence: 95%

Oxygen cost of exercise hyperpnoea is greater in women compared with men

Dominelli

Render

Molgat‐Seon

et al. 2015

The Journal of Physiology

110

130

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Key pointsr The oxygen cost of breathing represents a significant fraction of total oxygen uptake during intense exercise.r At a given ventilation, women have a greater work of breathing compared with men, and because work is linearly related to oxygen uptake we hypothesized that their oxygen cost of breathing would also be greater.r For a given ventilation, women had a greater absolute oxygen cost of breathing, and this represented a greater fraction of total oxygen uptake.r Regardless of sex, those who developed expiratory flow limitation had a greater oxygen cost of breathing at maximal exercise.r The greater oxygen cost of breathing in women indicates that a greater fraction of total oxygen uptake (and possibly cardiac output) is directed to the respiratory muscles, which may influence blood flow distribution during exercise.Abstract We compared the oxygen cost of breathing (V O 2 RM ) in healthy men and women over a wide range of exercise ventilations (V E ). Eighteen subjects (nine women) completed 4 days of testing. First, a step-wise maximal cycle exercise test was completed for the assessment of spontaneous breathing patterns. Next, subjects were familiarized with the voluntary hyperpnoea protocol used to estimateV O 2 RM . During the final two visits, subjects mimicked multiple times (four to six) the breathing patterns associated with five or six different exercise stages. Each trial lasted 5 min, and on-line pressure-volume and flow-volume loops were superimposed on target loops obtained during exercise to replicate the work of breathing accurately. At ß55 l min −1 V E ,V O 2 RM was significantly greater in women. At maximal ventilation, the absoluteV O 2 RM was not different (P > 0.05) between the sexes, but represented a significantly greater fraction of whole-bodyV O 2 in women (13.8 ± 1.5 vs. 9.4 ± 1.1%V O 2 ). During heavy exercise at 92 and 100% V O 2 max , the unit cost ofV E was +0.7 and +1.1 ml O 2 l −1 greater in women (P < 0.05). AtV O 2 max , men and women who developed expiratory flow limitation had a significantly greaterV O 2 RM than those who did not (435 ± 44 vs. 331 ± 30 ml O 2 min −1 ). In conclusion, women have a greateṙ V O 2 RM for a givenV E , and this represents a greater fraction of whole-bodyV O 2 . The greaterV O 2 RM in women may have implications for the integrated physiological response to exercise. Abbreviations EFL, expiratory flow limitation; MEFV, maximal expiratory flow-volume;V E , expired minute ventilation;V Emax , maximal expired minute ventilation;V O2 , oxygen uptake;V O2 max , maximal oxygen uptake;V O2RM , oxygen uptake of the respiratory muscles; WOB, work of breathing.

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Section: Discussionmentioning

confidence: 95%

Oxygen cost of exercise hyperpnoea is greater in women compared with men

Dominelli

Render

Molgat‐Seon

et al. 2015

The Journal of Physiology

110

130

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“…For example, dynamic variables such as maximal oxygen uptake (McClaran et al, 1998) and operational lung volumes (Guenette et al, 2007), as well as static anatomical factors such as lung and airway size (Dominelli et al, 2011; Smith et al, 2014) have been shown to predict EFL. The current study suggests that the curvature of the MEFV curve also plays a role in predicting those who may develop EFL during exercise.…”

Section: Discussionmentioning

confidence: 99%

Quantifying the shape of maximal expiratory flow-volume curves in healthy humans and asthmatic patients

Dominelli

Molgat‐Seon

Foster

et al. 2016

Respiratory Physiology & Neurobiology

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Differences in the absolute flow and volume of maximal expiratory flow-volume (MEFV) curves have been studied extensively in health and disease. However, the shapes of MEFV curves have received less attention. We questioned if the MEFV curve shape was associated with (i) expiratory flow limitation (EFL) in health and (ii) changes in bronchial caliber in asthmatics. Using the slope-ratio (SR) index, we quantified MEFV curve shape in 84 healthy subjects and 8 matched asthmatics. Healthy subjects performed a maximal exercise test to assess EFL. Those with EFL during had a greater SR (1.15 ± 0.20 vs. 0.85 ± 0.20, p < 0.05) yet, there was no association between maximal oxygen consumption and SR (r = 0.14, p > 0.05). Asthmatics average SR was greater than the healthy subjects (1.35 ± 0.03 vs. 0.90 ± 0.11, p < 0.05), but there were no differences when bronchial caliber was manipulated. In conclusion, a greater SR is related to EFL and this metric could aid in discriminating between groups known to differ in the absolute size of MEFV curves.

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“…Mead proposed that airway length depends on lung volume but airway caliber growth does not (10). Dysanapsis may occur in otherwise healthy subjects with expiratory flow limitation (11) and may be more pronounced in women than in men (12,13).…”

Section: At a Glance Commentarymentioning

confidence: 99%

Obesity and Airway Dysanapsis in Children with and without Asthma

Forno

Weiner

Mullen

et al. 2017

Am J Respir Crit Care Med

191

137

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Rationale: For unclear reasons, obese children with asthma have higher morbidity and reduced response to inhaled corticosteroids.Objectives: To assess whether childhood obesity is associated with airway dysanapsis (an incongruence between the growth of the lungs and the airways) and whether dysanapsis is associated with asthma morbidity.Methods: We examined the relationship between obesity and dysanapsis in six cohorts of children with and without asthma, as well as the relationship between dysanapsis and clinical outcomes in children with asthma. Adjusted odds ratios (ORs) were calculated for each cohort and in a combined analysis of all cohorts; longitudinal analyses were also performed for cohorts with available data. Hazard ratios (HRs) for clinical outcomes were calculated for children with asthma in the Childhood Asthma Management Program.Measurements and Main Results: Being overweight or obese was associated with dysanapsis in both the cross-sectional (OR, 1.95; 95% confidence interval [CI], 1.62-2.35 [for overweight/obese compared with normal weight children]) and the longitudinal (OR, 4.31; 95% CI, 2.99-6.22 [for children who were overweight/obese at all visits compared with normal weight children]) analyses. Dysanapsis was associated with greater lung volumes (FVC, vital capacity, and total lung capacity) and lesser flows (FEV 1 and forced expiratory flow, midexpiratory phase), and with indicators of ventilation inhomogeneity and anisotropic lung and airway growth. Among overweight/obese children with asthma, dysanapsis was associated with severe disease exacerbations (HR, 1.95; 95% CI, 1.38-2.75) and use of systemic steroids (HR, 3.22; 95% CI, 2.02-5.14).Conclusions: Obesity is associated with airway dysanapsis in children. Dysanapsis is associated with increased morbidity among obese children with asthma and may partly explain their reduced response to inhaled corticosteroids.

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Dysanapsis ratio as a predictor for expiratory flow limitation

Cited by 41 publications

References 20 publications

Oxygen cost of exercise hyperpnoea is greater in women compared with men

Oxygen cost of exercise hyperpnoea is greater in women compared with men

Quantifying the shape of maximal expiratory flow-volume curves in healthy humans and asthmatic patients

Obesity and Airway Dysanapsis in Children with and without Asthma

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