Publications by authors named "Amany F Elbehairy"

32 Publications

Impaired Ventilatory Efficiency, Dyspnea and Exercise Intolerance in Chronic Obstructive Pulmonary Disease: Results from the CanCOLD Study.

Am J Respir Crit Care Med 2022 Mar 25. Epub 2022 Mar 25.

Queen's University, Division of Respiratory and Critical Care Medicine, Department of Medicine, Kingston, Ontario, Canada;

Rationale: Impaired exercise ventilatory efficiency (high ventilatory requirements for CO2 [V̇E/V̇CO2]) provides an indication of pulmonary gas exchange abnormalities in chronic obstructive pulmonary disease (COPD).

Objectives: To determine: 1) the association between high V̇E/V̇CO2 and clinical outcomes (dyspnea and exercise capacity) and its relationship to lung function and structural radiographic abnormalities; and 2) its prevalence in a large population-based cohort.

Methods: Participants were recruited randomly from the population and underwent clinical evaluation, pulmonary function, cardiopulmonary exercise testing and chest computed tomography (CT). Impaired exercise ventilatory efficiency was defined by a nadir V̇E/V̇CO2 above the upper limit of normal (V̇E/V̇CO2>ULN), using population-based normative values.

Measurements And Main Results: Participants included 445 never-smokers, 381 ever-smokers without airflow obstruction, 224 with GOLD 1 COPD, and 200 with GOLD 2-4 COPD. Participants with V̇E/V̇CO2>ULN were more likely to have activity-related dyspnea (Medical Research Council dyspnea scale≥2, odds ratio=1.77[1.31-2.39]) and abnormally low peak oxygen uptake (V̇O2peakULN was 24% in COPD (similar in GOLD 1 and 2-4), which was greater than in never-smokers (13%) and ever-smokers (12%).

Conclusions: V̇E/V̇CO2>ULN was associated with greater dyspnea and low VO2peak and was present in 24% of all participants with COPD, regardless of GOLD stage. The results show the importance of recognizing impaired exercise ventilatory efficiency as a potential contributor to dyspnea and exercise limitation, even in mild COPD.
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http://dx.doi.org/10.1164/rccm.202109-2171OCDOI Listing
March 2022

Compensatory responses to increased mechanical abnormalities in COPD during sleep.

Eur J Appl Physiol 2022 Mar 16;122(3):663-676. Epub 2022 Jan 16.

Department of Medicine, Queen's University, Kingston, Canada.

Purpose: To assess whether night-time increases in mechanical loading negatively impact respiratory muscle function in COPD and whether compensatory increases in inspiratory neural drive (IND) are adequate to stabilize ventilatory output and arterial oxygen saturation, especially during sleep when wakefulness drive is withdrawn.

Methods: 21 patients with moderate-to-severe COPD and 20 age-/sex-matched healthy controls (CTRL) participated in a prospective, cross-sectional, one-night study to assess the impact of COPD on serial awake, supine inspiratory capacity (IC) measurements and continuous dynamic respiratory muscle function (esophageal manometry) and IND (diaphragm electromyography, EMGdi) in supine sleep.

Results: Supine inspiratory effort and EMGdi were consistently twice as high in COPD versus CTRL (p < 0.05). Despite overnight increases in awake total airways resistance and dynamic lung hyperinflation in COPD (p < 0.05; not in CTRL), elevated awake EMGdi and respiratory effort were unaltered in COPD overnight. At sleep onset (non-rapid eye movement sleep, N2), EMGdi was decreased versus wakefulness in COPD (- 43 ± 36%; p < 0.05) while unaffected in CTRL (p = 0.11); however, respiratory effort and arterial oxygen saturation (SpO) were unchanged. Similarly, in rapid eye movement (stage R), sleep EMGdi was decreased (- 38 ± 32%, p < 0.05) versus wakefulness in COPD, with preserved respiratory effort and minor (2%) reduction in SpO.

Conclusions: Despite progressive mechanical loading overnight and marked decreases in wakefulness drive, inspiratory effort and SpO were well maintained during sleep in COPD. Preserved high inspiratory effort during sleep, despite reduced EMGdi, suggests continued (or increased) efferent activation of extra-diaphragmatic muscles, even in stage R sleep.

Clinical Trial Information: The COPD data reported herein were secondary data (Placebo arm only) obtained through the following Clinical Trial: "Effect of Aclidinium/Formoterol on Nighttime Lung Function and Morning Symptoms in Chronic Obstructive Pulmonary Disease" ( https://clinicaltrials.gov/ct2/show/NCT02429765 ; NCT02429765).
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http://dx.doi.org/10.1007/s00421-021-04869-0DOI Listing
March 2022

Qualitative Components of Dyspnea during Incremental Exercise across the COPD Continuum.

Med Sci Sports Exerc 2021 12;53(12):2467-2476

Respiratory Investigation Unit, Department of Medicine, Queen's University and Kingston Health Sciences Centre, Kingston General Hospital Campus, Kingston, Ontario, CANADA.

Introduction: Evaluation of the intensity and quality of activity-related dyspnea is potentially useful in people with chronic obstructive pulmonary disease (COPD). The present study sought to examine associations between qualitative dyspnea descriptors, dyspnea intensity ratings, dynamic respiratory mechanics, and exercise capacity during cardiopulmonary exercise testing (CPET) in COPD and healthy controls.

Methods: In this cross-sectional study, 261 patients with mild-to-very severe COPD (forced expiratory volume in 1 s, 62 ± 25%pred) and 94 age-matched controls (forced expiratory volume in 1 s, 114 ± 14%pred) completed an incremental cycle CPET to determine peak oxygen uptake (V˙O2peak). Throughout exercise, expired gases, operating lung volumes, and dyspnea intensity were assessed. At peak exercise, dyspnea quality was assessed using a modified 15-item questionnaire.

Results: Logistic regression analysis revealed that among 15 dyspnea descriptors, only those alluding to the cluster "unsatisfied inspiration" were consistently associated with an increased likelihood for both critical inspiratory mechanical constraint (end-inspiratory lung volume/total lung capacity ratio ≥0.9) during exercise and reduced exercise capacity (V˙O2peak < lower limit of normal) in COPD (odds ratio (95% confidence interval), 3.26 (1.40-7.60) and 3.04 (1.24-7.45), respectively; both, P < 0.05). Thus, patients reporting "unsatisfied inspiration" (n = 177 (68%)) had an increased relative frequency of critical inspiratory mechanical constraint and low exercise capacity compared with those who did not select this descriptor, regardless of COPD severity or peak dyspnea intensity scores.

Conclusions: In patients with COPD, regardless of disease severity, reporting descriptors in the unsatisfied inspiration cluster complemented traditional assessments of dyspnea during CPET and helped identify patients with critical mechanical abnormalities germane to exercise intolerance.
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http://dx.doi.org/10.1249/MSS.0000000000002741DOI Listing
December 2021

Mechanisms of Exertional Dyspnea in Patients with Mild COPD and a Low Resting DL.

COPD 2021 10 8;18(5):501-510. Epub 2021 Sep 8.

Respiratory Investigation Unit, Department of Medicine, Queen's University, and Kingston Health Sciences Centre, Kingston, Ontario, Canada.

Patients with mild chronic obstructive pulmonary disease (COPD) and lower resting diffusing capacity for carbon monoxide (DL) often report troublesome dyspnea during exercise although the mechanisms are not clear. We postulated that in such individuals, exertional dyspnea is linked to relatively high inspiratory neural drive (IND) due, in part, to the effects of reduced ventilatory efficiency. This cross-sectional study included 28 patients with GOLD I COPD stratified into two groups with ( = 15) and without ( = 13) DL less than the lower limit of normal (
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http://dx.doi.org/10.1080/15412555.2021.1932782DOI Listing
October 2021

Sleep quality and architecture in COPD: the relationship with lung function abnormalities.

J Bras Pneumol 2021 19;47(3):e20200612. Epub 2021 Jul 19.

. Division of Respiratory & Sleep Medicine, Department of Medicine, Queen's University, Kingston (ON) Canada.

Objective: Impaired respiratory mechanics and gas exchange may contribute to sleep disturbance in patients with COPD. We aimed to assess putative associations of different domains of lung function (airflow limitation, lung volumes, and gas exchange efficiency) with polysomnography (PSG)-derived parameters of sleep quality and architecture in COPD.

Methods: We retrospectively assessed data from COPD 181 patients ≥ 40 years of age who underwent spirometry, plethysmography, and overnight PSG. Univariate and multivariate linear regression models predicted sleep efficiency (total sleep time/total recording time) and other PSG-derived parameters that reflect sleep quality.

Results: The severity of COPD was widely distributed in the sample (post-bronchodilator FEV1 ranging from 25% to 128% of predicted): mild COPD (40.3%), moderate COPD (43.1%), and severe-very severe COPD (16.6%). PSG unveiled a high proportion of obstructive sleep apnea (64.1%) and significant nocturnal desaturation (mean pulse oximetry nadir = 82.2% ± 6.9%). After controlling for age, sex, BMI, apnea-hypopnea index, nocturnal desaturation, comorbidities, and psychotropic drug prescription, FEV1/FVC was associated with sleep efficiency (β = 25.366; R2 = 14%; p < 0.001), whereas DLCO predicted sleep onset latency (β = -0.314; R2 = 13%; p < 0.001) and rapid eye movement sleep time/total sleep time in % (β = 0.085; R2 = 15%; p = 0.001).

Conclusions: Pulmonary function variables reflecting severity of airflow and gas exchange impairment, adjusted for some potential confounders, were weakly related to PSG outcomes in COPD patients. The direct contribution of the pathophysiological hallmarks of COPD to objectively measured parameters of sleep quality seems to be less important than it was previously assumed.
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http://dx.doi.org/10.36416/1806-3756/e20200612DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8332731PMC
August 2021

Reduced exercise tolerance in mild chronic obstructive pulmonary disease: The contribution of combined abnormalities of diffusing capacity for carbon monoxide and ventilatory efficiency.

Respirology 2021 08 7;26(8):786-795. Epub 2021 Apr 7.

Respiratory Investigation Unit, Department of Medicine, Queen's University and Kingston Health Sciences Centre, Kingston General Hospital Campus, Kingston, Ontario, Canada.

Background And Objective: The combination of both reduced resting diffusing capacity of the lung for carbon monoxide (DL ) and ventilatory efficiency (increased ventilatory requirement for CO clearance [V˙ /V˙CO ]) has been linked to exertional dyspnoea and exercise intolerance in chronic obstructive pulmonary disease (COPD) but the underlying mechanisms are poorly understood. The current study examined if low resting DL and higher exercise ventilatory requirements were associated with earlier critical dynamic mechanical constraints, dyspnoea and exercise limitation in patients with mild COPD.

Methods: In this retrospective analysis, we compared V˙ /V˙CO , dynamic inspiratory reserve volume (IRV), dyspnoea and exercise capacity in groups of patients with Global Initiative for Chronic Obstructive Lung Disease stage 1 COPD with (1) a resting DL at or greater than the lower limit of normal (≥LLN; Global Lung Function Initiative reference equations [n = 44]) or (2) below the
Results: Spirometry and resting lung volumes were similar in the two COPD groups. During exercise, V˙ /V˙CO (nadir and slope) was consistently higher in the DL  < LLN compared with the other groups (all p < 0.05). The DL  < LLN group had lower IRV and greater dyspnoea intensity at standardized submaximal work rates and lower peak work rate and oxygen uptake than the other two groups (all p < 0.05).

Conclusion: Reduced exercise capacity in patients with DL  < LLN was related to higher ventilatory requirements, a faster rate of decline in dynamic IRV and greater dyspnoea during exercise. These simple measurements should be considered for the clinical evaluation of unexplained exercise intolerance in individuals with ostensibly mild COPD.
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http://dx.doi.org/10.1111/resp.14045DOI Listing
August 2021

European Respiratory Society International Congress 2020: highlights from best-abstract awardees.

Breathe (Sheff) 2020 Dec;16(4):200270

REVAL - Rehabilitation Research Centre, BIOMED - Biomedical Research Institute, Faculty of Rehabilitation Sciences, Hasselt University, Diepenbeek, Belgium.

https://bit.ly/3kJ9JrJ.
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http://dx.doi.org/10.1183/20734735.0270-2020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7910029PMC
December 2020

Elevated exercise ventilation in mild COPD is not linked to enhanced central chemosensitivity.

Respir Physiol Neurobiol 2021 02 5;284:103571. Epub 2020 Nov 5.

Respiratory Investigation Unit, Department of Medicine, Queen's University and Kingston Health Sciences Centre Kingston General Hospital Campus, Kingston, Ontario, Canada. Electronic address:

Background: The purpose of this study was to determine if altered central chemoreceptor characteristics contributed to the elevated ventilation relative to carbon dioxide production (V̇/V̇CO) response during exercise in mild chronic obstructive pulmonary disease (COPD).

Methods: Twenty-nine mild COPD and 19 healthy age-matched control participants undertook lung function testing followed by symptom-limited incremental cardiopulmonary exercise testing . On a separate day, basal (non-chemoreflex) ventilation (V̇), the central chemoreflex ventilatory recruitment threshold for CO (VRTCO), and central chemoreflex sensitivity (V̇) were assessed using the modified Duffin's CO rebreathing method. Resting arterialized blood gas data were also obtained.

Results: At standardized exercise intensities, absolute V̇ and V̇/V̇CO were consistently elevated and the end-tidal partial pressure of CO was relatively decreased in mild COPD versus controls (all p < 0.05). There were no between-group differences in resting arterialized blood gas parameters, basal V̇, VRTCO, or V̇ (all p > 0.05).

Conclusion: These data have established that excessive exercise ventilation in mild COPD is not explained by altered central chemosensitivity.
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http://dx.doi.org/10.1016/j.resp.2020.103571DOI Listing
February 2021

Mechanisms of orthopnoea in patients with advanced COPD.

Eur Respir J 2021 03 11;57(3). Epub 2021 Mar 11.

Division of Respiratory Medicine, Dept of Medicine, Queen's University and Kingston Health Sciences Centre, Kingston, ON, Canada

Many patients with severe chronic obstructive pulmonary disease (COPD) report an unpleasant respiratory sensation at rest, which is further amplified by adoption of a supine position (orthopnoea). The mechanisms of this acute symptomatic deterioration are poorly understood.Sixteen patients with advanced COPD and a history of orthopnoea and 16 age- and sex-matched healthy controls underwent pulmonary function tests (PFTs) and detailed sensory-mechanical measurements including inspiratory neural drive (IND) assessed by diaphragm electromyography (EMG), oesophageal pressure ( ) and gastric pressure ( ), in both sitting and supine positions.Patients had severe airflow obstruction (forced expiratory volume in 1 s (FEV): 40±18% pred) and lung hyperinflation. Regardless of the position, patients had lower inspiratory capacity (IC) and higher IND for a given tidal volume ( ) ( greater neuromechanical dissociation (NMD)), higher intensity of breathing discomfort, higher minute ventilation (') and higher breathing frequency ( ) compared with controls (all p<0.05). For controls in a supine position, IC increased by 0.48 L sitting erect, with a small drop in ', mainly due to reduced (all p<0.05). By contrast, IC remained unaltered in patients with COPD, but dynamic lung compliance ( ) decreased (p<0.05) in the supine position. Breathing discomfort, inspiratory work of breathing (WOB), inspiratory effort, IND, NMD and neuroventilatory uncoupling all increased in COPD patients in the supine position (p<0.05), but not in the healthy controls. Orthopnoea was associated with acute changes in IND (r=0.65, p=0.01), neuroventilatory uncoupling (r=0.76, p=0.001) and NMD (r=0.73, p=0.002).In COPD, onset of orthopnoea coincided with an abrupt increase in elastic loading of the inspiratory muscles in recumbency, in association with increased IND and greater NMD of the respiratory system.
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http://dx.doi.org/10.1183/13993003.00754-2020DOI Listing
March 2021

Deterioration of Nighttime Respiratory Mechanics in COPD: Impact of Bronchodilator Therapy.

Chest 2021 01 27;159(1):116-127. Epub 2020 Jun 27.

Department of Medicine, Queen's University, Kingston, Canada; Division of Respiratory Medicine, Queen's University, Kingston, Canada. Electronic address:

Background: COPD is associated with nighttime respiratory symptoms, poor sleep quality, and increased risk of nocturnal death. Overnight deterioration of inspiratory capacity (IC) and FEV have been documented previously. However, the precise nature of this deterioration and mechanisms by which evening bronchodilation may mitigate this occurrence have not been studied.

Research Question: What is the effect of evening dosing of dual, long-acting bronchodilation on detailed nocturnal respiratory mechanics and inspiratory neural drive (IND)?

Study Design And Methods: A double-blind, randomized, placebo-controlled crossover study assessed the effects of evening long-acting bronchodilation (aclidinium bromide/formoterol fumarate dihydrate: 400/12 μg) or placebo on morning trough IC (12 h after the dose; primary outcome) and serial overnight measurements of spirometry, dynamic respiratory mechanics, and IND (secondary outcomes). Twenty participants with COPD (moderate/severe airway obstruction and lung hyperinflation) underwent serial measurements of IC, spirometry, breathing pattern, esophageal and transdiaphragmatic pressures, and diaphragm electromyography (diaphragmatic electromyography as a percentage of maximum; IND) at 6 time points from 0 to 12 h after the dose and compared with sleeping IND.

Results: Compared with placebo, evening bronchodilation was not associated with increased morning trough IC 12 h after the dose (P = .48); however, nadir IC (lowest IC, independent of time), peak IC, area under the curve for 12 h after the dose, and IC for 10 h after the dose were improved (P < .05). During placebo, total airways resistance, lung hyperinflation, IND, and tidal esophageal and transdiaphragmatic pressure swings all increased significantly overnight compared with baseline evening values; however, each of these parameters improved with bronchodilator treatment (P < .05) with no change in ventilation or breathing pattern.

Interpretation: Respiratory mechanics significantly deteriorated at night during placebo. Although the morning trough IC was unchanged, evening bronchodilator treatment was associated consistently with sustained overnight improvements in dynamic respiratory mechanics and inspiratory neural drive compared with placebo CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov identifier NCT02429765.
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http://dx.doi.org/10.1016/j.chest.2020.06.033DOI Listing
January 2021

Impact of a Specialized Ambulatory Clinic on Refractory Breathlessness in Subjects With Advanced COPD.

Respir Care 2020 Apr 12;65(4):444-454. Epub 2019 Nov 12.

Palliative Care and Respirology Divisions, Department of Medicine, Queen's University and Kingston Health Sciences Centre, Kingston, Ontario, Canada.

Background: Severe exertional dyspnea is a commonly reported symptom in patients with COPD, especially in the advanced stages. Our objective was to assess the preliminary impact of comprehensive, individualized management provided by a specialized tertiary center clinic on exertional dyspnea and patient-centered outcomes in patients with advanced COPD.

Methods: This retrospective analysis included 45 subjects with COPD who were evaluated in a newly established dyspnea clinic over 3 years. Those with severe exertional dyspnea (Medical Research Council dyspnea score of ≥4/5), despite optimal disease-targeted therapy were eligible for referral. We used the revised Edmonton Symptom Assessment System (ESAS-r) to assess symptoms. Responders were defined as those whose change from baseline to 2-months met the minimum clinically important difference of ≤-1 in ESAS-r score for shortness of breath.

Results: Subjects (mean ± SD age 70 ± 7 years) had an average FEV of 36 ± 18% predicted and a Medical Research Council dyspnea score of 4.7 ± 0.4. Responses to the intervention were variable and mean change in the ESAS-r score for shortness of breath in the total group was -0.32 ± 3.39, = .53. Forty-seven percent of the subjects were identified as responders, and 42, 40, 40, and 33% met the minimum clinically important difference for improvement in ESAS-r scores for tiredness, anxiety, well-being, and depression, respectively. Responders had fewer emergency department annual visits in the 2 years after their first clinic visit compared with nonresponders (mean ± SD, 1.38 ± 1.63 vs 4.45 ± 5.52, = .034).

Conclusions: Although the impact of our specialized advanced dyspnea clinic was variable, as evaluated by the ESAS-r, it provided measurable additional clinically important benefit to almost half of the subjects with advanced COPD and severe refractory dyspnea.
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http://dx.doi.org/10.4187/respcare.06950DOI Listing
April 2020

Eligibility for Lung Volume Reduction Surgery in Patients With COPD Identified in a UK Primary Care Setting.

Chest 2020 02 2;157(2):276-285. Epub 2019 Aug 2.

National Heart and Lung Institute, Imperial College London, London, England.

Background: Although lung volume reduction surgery (LVRS) improves survival in appropriately selected patients with COPD, few procedures are performed. The National Institute for Health and Care Excellence has recommended a more systematic approach to identifying potential candidates. We investigated LVRS referrals from a UK primary care population and aimed to establish an accurate estimate of eligible patients and determine a strategy for identifying potential candidates systematically.

Methods: Clinical Practice Research Datalink GOLD (a primary care database) and the linked Hospital Episode Statistics inpatient and Diagnostic Imaging Dataset were used. Patients with COPD who had undergone LVRS, patients who met basic eligibility criteria for further screening for LVRS, and patients meeting a more stringent eligibility criteria were identified from April 2012 to September 2015. Thoracic CT scan, pulmonary rehabilitation status, referral to respiratory outpatient clinics, and acute exacerbation of COPD requiring hospitalization were compared between actual LVRS recipients and potentially eligible patients.

Results: Among the 73,697 patients with COPD included, 36 (0.05%) received LVRS, 5,984 (8.1%) met basic eligibility criteria, and 159 (0.2%) met more stringent eligibility criteria. LVRS recipients were younger (mean age ± SD, 64 ± 9.2 years) than the stringently eligible patients (mean age ± SD, 69 ± 8.9 years; P = .01). Few patients meeting stringent eligibility criteria (6.9%) had a CT scan of the thorax in the preceding 3 years or had been referred for assessment in secondary care.

Conclusions: A substantial unmet need exists among patients with COPD who could potentially benefit from a lung volume reduction procedure but who are not being investigated or referred to consider this possibility.
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http://dx.doi.org/10.1016/j.chest.2019.07.016DOI Listing
February 2020

Low resting diffusion capacity, dyspnea, and exercise intolerance in chronic obstructive pulmonary disease.

J Appl Physiol (1985) 2019 10 1;127(4):1107-1116. Epub 2019 Aug 1.

Department of Medicine and Queen's University and Kingston Health Sciences Centre, Kingston, Ontario, Canada.

The mechanisms linking reduced diffusing capacity of the lung for carbon monoxide (Dl) to dyspnea and exercise intolerance across the chronic obstructive pulmonary disease (COPD) continuum are poorly understood. COPD progression generally involves both Dl decline and worsening respiratory mechanics, and their relative contribution to dyspnea has not been determined. In a retrospective analysis of 300 COPD patients who completed symptom-limited incremental cardiopulmonary exercise tests, we tested the association between peak oxygen-uptake (V̇o), Dl, and other resting physiological measures. Then, we stratified the sample into tertiles of forced expiratory volume in 1 s (FEV) and inspiratory capacity (IC) and compared dyspnea ratings, pulmonary gas exchange, and respiratory mechanics during exercise in groups with normal and low Dl [i.e.,
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http://dx.doi.org/10.1152/japplphysiol.00341.2019DOI Listing
October 2019

Patterns of breathlessness and associated consulting behaviour: results of an online survey.

Thorax 2019 08 8;74(8):814-817. Epub 2019 Apr 8.

National Heart and Lung Institute, Imperial College, London, UK

The online British Lung Foundation Breath Test provides an opportunity to study the relationship between breathlessness, common sociobehavioural risk factors and interaction with healthcare. We analysed data from 356 799 responders: 71% were ≥50 years old and 18% were smokers. 20% reported limiting breathlessness (Medical Research Council breathlessness score ≥3), and the majority of these (85%) worried about their breathing; of these, 29% had not sought medical advice. Of those who had, 58% reported that the advice received had not helped their breathlessness. Limiting breathlessness was associated with being older, physically inactive, smoking and a higher body mass index. These data suggest a considerable unmet need associated with breathlessness as well as possibilities for intervention.
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http://dx.doi.org/10.1136/thoraxjnl-2018-212950DOI Listing
August 2019

Acute bronchodilator therapy does not reduce wasted ventilation during exercise in COPD.

Respir Physiol Neurobiol 2018 06 22;252-253:64-71. Epub 2018 Mar 22.

Department of Medicine, Queen's University and Kingston Health Sciences Centre, Kingston, ON, Canada. Electronic address:

This randomized, double-blind, crossover study aimed to determine if acute treatment with inhaled bronchodilators, by improving regional lung hyperinflation and ventilation distribution, would reduce dead space-to-tidal volume ratio (V/V); thus contributing to improved exertional dyspnea in COPD. Twenty COPD patients (FEV = 50 ± 15% predicted; mean ± SD) performed pulmonary function tests and symptom-limited constant-work rate exercise at 75% peak-work rate (with arterialized capillary blood gases) after nebulized bronchodilator (BD; ipratropium 0.5mg + salbutamol 2.5 mg) or placebo (PL; normal saline). After BD versus PL: Functional residual capacity decreased by 0.4L (p = .0001). Isotime during exercise after BD versus PL (p < .05): dyspnea decreased: 1.2 ± 1.9 Borg-units; minute ventilation increased: 3.8 ± 5.5 L/min; IC increased: 0.24 ± 0.28 L and V increased 0.19 ± 0.16 L. There was no significant difference in arterial CO tension or V/V, but alveolar ventilation increased by 3.8 ± 5.5 L/min (p = .02). Post-BD improvements in respiratory mechanics explained 51% of dyspnea reduction at a standardized exercise time. Bronchodilator-induced improvements in respiratory mechanics were not associated with reduced wasted ventilation - a residual contributory factor to exertional dyspnea during exercise in COPD.
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http://dx.doi.org/10.1016/j.resp.2018.03.012DOI Listing
June 2018

Unraveling the Cause of Severe Exertional Dyspnea in a Heavy Smoker.

Ann Am Thorac Soc 2017 12;14(12):1849-1855

1 Department of Medicine, Queen's University and Kingston General Hospital, Kingston, Ontario, Canada.

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http://dx.doi.org/10.1513/AnnalsATS.201705-382CCDOI Listing
December 2017

Sensory-mechanical effects of a dual bronchodilator and its anticholinergic component in COPD.

Respir Physiol Neurobiol 2018 01 7;247:116-125. Epub 2017 Oct 7.

Respiratory Investigation Unit, Department of Medicine, Queen's University & Kingston General Hospital, Kingston, Ontario, Canada.

This randomized, double-blind, crossover study examined the physiological rationale for using a dual long-acting bronchodilator (umeclidinium/vilanterol (UME/VIL)) versus its muscarinic-antagonist component (UME) as treatment for dyspnea and exercise intolerance in moderate COPD. After each 4-week treatment period, subjects performed pulmonary function and symptom-limited constant-work rate cycling tests with diaphragm electromyogram (EMGdi), esophageal (Pes), gastric (Pga) and transdiaphragmatic (Pdi) pressure measurements. Fourteen subjects completed the study. Both treatments improved spirometry and airway resistance. UME/VIL had larger increases in FEV (+0.14±0.23L, p<0.05) but no added reduction in lung hyperinflation compared with UME. Isotime during exercise after UME/VIL versus UME (p<0.05): "unpleasantness of breathing" fell 0.8±1.3 Borg units; mean expiratory flow and ventilation increased; Pdi and Pga decreased. There were no treatment differences in endurance time, breathing pattern, operating lung volumes, inspiratory neural drive (EMGdi) or respiratory muscle effort (Pes swings) during exercise. UME/VIL compared with UME was associated with reduced breathing unpleasantness reflecting improved airway and respiratory muscle function during exercise.
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http://dx.doi.org/10.1016/j.resp.2017.10.001DOI Listing
January 2018

Mild chronic obstructive pulmonary disease: why spirometry is not sufficient!

Expert Rev Respir Med 2017 07 5;11(7):549-563. Epub 2017 Jun 5.

a Department of Medicine , Queen's University and Kingston General Hospital , Kingston , ON , Canada.

Introduction: Chronic obstructive pulmonary disease (COPD) - an inflammatory disease of the airways, alveoli and lung microvasculature - is a leading cause of death worldwide. Smokers with milder airway obstruction constitute the majority of patients with this disease. Many studies have shown increased morbidity, activity-related dyspnea, exercise intolerance and mortality in such patients, compared with age-matched healthy populations. Clinical evaluation of symptomatic smokers with ostensibly mild airway obstruction poses a challenge in clinical practice as spirometry can obscure extensive heterogeneous pathophysiological impairment. Areas covered: A detailed review of the evidence for complex biological, physiological and radiological abnormalities in smokers who barely fit arbitrary spirometric criteria for COPD diagnosis. A brief discussion of the debate about current diagnostic spirometric criteria for COPD that can lead to diagnostic confusion and, in-some-instances, to inappropriate management. Finally, we provide a review of the clinical implications of these structural and functional abnormalities and try to build a solid rationale for earlier detection and effective, timely management. Expert commentary: The prevalence of mild COPD among smokers is high, yet under-diagnosis remains a major problem and there is lack of evidence-based management recommendations for this sub-population. Further tests beyond spirometry are useful in uncovering patho-physiological derangements that are clinically relevant.
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http://dx.doi.org/10.1080/17476348.2017.1334553DOI Listing
July 2017

The Link between Reduced Inspiratory Capacity and Exercise Intolerance in Chronic Obstructive Pulmonary Disease.

Ann Am Thorac Soc 2017 Jul;14(Supplement_1):S30-S39

1 Respiratory Investigation Unit and Laboratory of Clinical Exercise Physiology, Queen's University and Kingston General Hospital, Kingston, Ontario, Canada; and.

Low inspiratory capacity (IC), chronic dyspnea, and reduced exercise capacity are inextricably linked and are independent predictors of increased mortality in chronic obstructive pulmonary disease. It is no surprise, therefore, that a major goal of management is to improve IC by reducing lung hyperinflation to improve respiratory symptoms and health-related quality of life. The negative effects of lung hyperinflation on respiratory muscle and cardiocirculatory function during exercise are now well established. Moreover, there is growing appreciation that a key mechanism of exertional dyspnea in chronic obstructive pulmonary disease is critical mechanical constraints on tidal volume expansion during exercise when resting IC is reduced. Further evidence for the importance of lung hyperinflation comes from multiple studies, which have reported the clinical benefits of therapeutic interventions that reduce lung hyperinflation and increase IC. A reduced IC in obstructive pulmonary disease is further eroded by exercise and contributes to ventilatory limitation and dyspnea. It is an important outcome for both clinical and research studies.
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http://dx.doi.org/10.1513/AnnalsATS.201610-834FRDOI Listing
July 2017

Resting Physiological Correlates of Reduced Exercise Capacity in Smokers with Mild Airway Obstruction.

COPD 2017 Jun 3;14(3):267-275. Epub 2017 Apr 3.

a Department of Medicine , Respiratory Investigation Unit, Queen's University and Kingston General Hospital , Kingston , ON , Canada.

Smokers with minor spirometric abnormalities can experience persistent activity-related dyspnea and exercise intolerance. Additional resting tests can expose heterogeneous physiological abnormalities, but their relevance and association with clinical outcomes remain uncertain. Subjects included sixty-two smokers (≥20 pack-years), with cough and/or dyspnea and minor airway obstruction [forced expiratory volume in one-second (FEV) ≥80% predicted and >5th percentile lower limit of normal (LLN) (i.e., z-score >-1.64) using the 2012-Global Lung Function Initiative equations]. They underwent spirometry, plethysmography, oscillometry, single-breath nitrogen washout, and symptom-limited incremental cycle exercise tests. Thirty-two age-matched nonsmoking controls were also studied. Thirty-three (53%) of smokers had chronic obstructive pulmonary disease by LLN criteria. In smokers [n = 62; age 65 ± 11 years; smoking history 43 ± 19 pack-years; post-bronchodilator FEV z-score -0.60 ± 0.72 and FEV/FVC z-score -1.56 ± 0.87 (mean ± SD)] versus controls, peak oxygen uptake (̇VO) was 21 ± 7 vs. 32 ± 9 ml/kg/min, and dyspnea/̇VO slopes were elevated (both p < 0.0001). Smokers had evidence of peripheral airway dysfunction and maldistribution of ventilation when compared to controls. In smokers versus controls: lung diffusing capacity for carbon monoxide (DCO) was 85 ± 22 vs. 105 ± 17% predicted, and residual volume (RV)/total lung capacity (TLC) was 36 ± 8 vs. 31 ± 6% (both p < 0.01). The strongest correlates of peak ̇VO were DCO% predicted (r = 0.487, p < 0.0005) and RV/TLC% (r = -0.389, p = 0.002). DCO% predicted was also the strongest correlate of dyspnea/̇VO slope (r = -0.352, p = 0.005). In smokers with mild airway obstruction, associations between resting tests of mechanics and pulmonary gas exchange and exercise performance parameters were weak, albeit consistent. Among these, DLCO showed the strongest association with important outcomes such as dyspnea and exercise intolerance measured during standardized incremental exercise tests.
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http://dx.doi.org/10.1080/15412555.2017.1281901DOI Listing
June 2017

Ventilatory Inefficiency and Exertional Dyspnea in Early Chronic Obstructive Pulmonary Disease.

Ann Am Thorac Soc 2017 Jul;14(Supplement_1):S22-S29

1 Respiratory Investigation Unit and Laboratory of Clinical Exercise Physiology, Queen's University and Kingston General Hospital, Kingston, Ontario, Canada.

Exertional dyspnea is present across the spectrum of chronic obstructive pulmonary disease (COPD) severity. However, without realizing it themselves, patients may decrease daily physical activity to avoid distressing respiratory sensations. Dyspnea also may be associated with deconditioning. Cardiopulmonary exercise testing can uncover exertional dyspnea and its physiological determinants in patients with preserved or only mildly reduced FEV. Dyspnea in mild COPD can largely be explained by increased "wasted" ventilation in the physiological dead space, which heightens the drive to breathe and worsens the inspiratory mechanical constraints. During incremental exercise testing, this is readily identified as an excessive ventilation-to-metabolic demand, that is, a high ventilation ([Formula: see text]e) to carbon dioxide output ([Formula: see text]co) relationship. Linking increases in [Formula: see text]e/[Formula: see text]co to exertional dyspnea may provide objective evidence that a patient's poor exercise tolerance is not just a consequence of deconditioning. This information should prompt a proactive therapeutic approach to increase the available ventilatory reserve by, for example, giving inhaled bronchodilators. Considering that the structural determinants of ventilatory inefficiency (early emphysema, ventilation-perfusion mismatching, and microvascular disease) may progress despite only modest changes in FEV, serial [Formula: see text]e/[Formula: see text]co measurements might also prove valuable to track disease progression in these symptomatic patients.
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http://dx.doi.org/10.1513/AnnalsATS.201612-1033FRDOI Listing
July 2017

Advances in the Evaluation of Respiratory Pathophysiology during Exercise in Chronic Lung Diseases.

Front Physiol 2017 22;8:82. Epub 2017 Feb 22.

Division of Respiratory Medicine, Department of Medicine, Queen's University and Kingston General Hospital Kingston, ON, Canada.

Dyspnea and exercise limitation are among the most common symptoms experienced by patients with various chronic lung diseases and are linked to poor quality of life. Our understanding of the source and nature of perceived respiratory discomfort and exercise intolerance in chronic lung diseases has increased substantially in recent years. These new mechanistic insights are the primary focus of the current review. Cardiopulmonary exercise testing (CPET) provides a unique opportunity to objectively evaluate the ability of the respiratory system to respond to imposed incremental physiological stress. In addition to measuring aerobic capacity and quantifying an individual's cardiac and ventilatory reserves, we have expanded the role of CPET to include evaluation of symptom intensity, together with a simple "non-invasive" assessment of relevant ventilatory control parameters and dynamic respiratory mechanics during standardized incremental tests to tolerance. This review explores the application of the new advances in the clinical evaluation of the pathophysiology of exercise intolerance in chronic obstructive pulmonary disease (COPD), chronic asthma, interstitial lung disease (ILD) and pulmonary arterial hypertension (PAH). We hope to demonstrate how this novel approach to CPET interpretation, which includes a quantification of activity-related dyspnea and evaluation of its underlying mechanisms, enhances our ability to meaningfully intervene to improve quality of life in these pathologically-distinct conditions.
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http://dx.doi.org/10.3389/fphys.2017.00082DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5319975PMC
February 2017

Exertional dyspnoea in COPD: the clinical utility of cardiopulmonary exercise testing.

Eur Respir Rev 2016 Sep;25(141):333-47

Geisel School of Medicine at Dartmouth, Hanover, NH, USA.

Activity-related dyspnoea is often the most distressing symptom experienced by patients with chronic obstructive pulmonary disease (COPD) and can persist despite comprehensive medical management. It is now clear that dyspnoea during physical activity occurs across the spectrum of disease severity, even in those with mild airway obstruction. Our understanding of the nature and source of dyspnoea is incomplete, but current aetiological concepts emphasise the importance of increased central neural drive to breathe in the setting of a reduced ability of the respiratory system to appropriately respond. Since dyspnoea is provoked or aggravated by physical activity, its concurrent measurement during standardised laboratory exercise testing is clearly important. Combining measurement of perceptual and physiological responses during exercise can provide valuable insights into symptom severity and its pathophysiological underpinnings. This review summarises the abnormal physiological responses to exercise in COPD, as these form the basis for modern constructs of the neurobiology of exertional dyspnoea. The main objectives are: 1) to examine the role of cardiopulmonary exercise testing (CPET) in uncovering the physiological mechanisms of exertional dyspnoea in patients with mild-to-moderate COPD; 2) to examine the escalating negative sensory consequences of progressive respiratory impairment with disease advancement; and 3) to build a physiological rationale for individualised treatment optimisation based on CPET.
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http://dx.doi.org/10.1183/16000617.0054-2016DOI Listing
September 2016

Mechanisms of exertional dyspnoea in symptomatic smokers without COPD.

Eur Respir J 2016 09 4;48(3):694-705. Epub 2016 Aug 4.

Respiratory Investigation Unit, Department of Medicine, Queen's University and Kingston General Hospital, Kingston, ON, Canada

Dyspnoea and activity limitation can occur in smokers who do not meet spirometric criteria for chronic obstructive pulmonary disease (COPD) but the underlying mechanisms are unknown.Detailed pulmonary function tests and sensory-mechanical relationships during incremental exercise with respiratory pressure measurements and diaphragmatic electromyography (EMGdi) were compared in 20 smokers without spirometric COPD and 20 age-matched healthy controls.Smokers (mean±sd post-bronchodilator forced expiratory volume in 1 s (FEV1)/forced vital capacity 75±4%, mean±sd FEV1 104±14% predicted) had greater activity-related dyspnoea, poorer health status and lower physical activity than controls. Smokers had peripheral airway dysfunction: higher phase-III nitrogen slopes (3.8±1.8 versus 2.6±1.1%·L(-1)) and airway resistance (difference between airway resistance measured at 5 Hz and 20 Hz 19±11 versus 12±7% at 5 Hz) than controls (p<0.05). Smokers had significantly (p<0.05) lower peak oxygen uptake (78±40 versus 107±45% predicted) and ventilation (61±26 versus 97±29 L·min(-1)). Exercise ventilatory requirements, operating lung volumes and cardio-circulatory responses were similar. However, submaximal dyspnoea ratings, resistive and total work of breathing were increased in smokers compared with controls (p<0.05); diaphragmatic effort (transdiaphragmatic pressure/maximumal transdiaphragmatic pressure) and fractional inspiratory neural drive to the diaphragm (EMGdi/maximal EMGdi) were also increased (p<0.05) mainly reflecting the reduced denominator.Symptomatic smokers at risk for COPD had greater exertional dyspnoea and lower exercise tolerance compared with healthy controls in association with greater airways resistance, contractile diaphragmatic effort and fractional inspiratory neural drive to the diaphragm.
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http://dx.doi.org/10.1183/13993003.00077-2016DOI Listing
September 2016

Respiratory Factors Contributing to Exercise Intolerance in Breast Cancer Survivors: A Case-Control Study.

J Pain Symptom Manage 2016 07 11;52(1):54-63. Epub 2016 Mar 11.

Palliative Care Medicine, Department of Medicine, Queen's University & Kingston General Hospital, Kingston, Ontario, Canada.

Context: Breast cancer survivors often experience activity-related dyspnea and exercise intolerance, but the underlying mechanisms remain unknown.

Objectives: We evaluated physiological contributors to reduced peak oxygen uptake (VO2), with particular attention to the role of respiratory impairment.

Methods: We compared symptom assessments, respiratory and peripheral muscle strength, pulmonary function, and ventilatory responses to symptom-limited incremental treadmill exercise in 29 women who had survived breast cancer and 29 age-matched healthy controls.

Results: Peak VO2 was reduced more than 20%, on average, in the cancer group compared with controls (P < 0.001). Slopes of dyspnea intensity ratings over ventilation or VO2 were >50% greater in the cancer group compared to controls (P < 0.05). Women with breast cancer had lower lung diffusing capacity for carbon monoxide (DLCO), respiratory and limb muscle strength, and ventilatory thresholds during exercise compared with controls (all P < 0.05). During exercise, indices of ventilatory efficiency were similar to controls, but inspiratory capacity (IC) was lower and breathing pattern was more rapid and shallow in the cancer group (P < 0.05). The lower peak VO2 in the cancer group was associated with greater dyspnea intensity, and lower DLCO, IC and ventilatory threshold (all P < 0.05).

Conclusion: Breast cancer survivors had greater peripheral and respiratory muscle weakness, greater reduction of IC, impaired lung diffusion, and evidence of deconditioning compared with controls. Exercise intolerance was multifactorial and correlated well with the combination of these factors as well as with exertional dyspnea. Individualized physiological testing in breast cancer survivors can identify important contributors to exercise intolerance which can be targeted for treatment.
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http://dx.doi.org/10.1016/j.jpainsymman.2016.01.004DOI Listing
July 2016

Reply: Effects of Mild Chronic Obstructive Pulmonary Disease on Gas Exchange during Cycling and Walking.

Am J Respir Crit Care Med 2015 Nov;192(9):1138-9

1 Queen's University Kingston, Ontario, Canada.

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http://dx.doi.org/10.1164/rccm.201507-1480LEDOI Listing
November 2015

Common Mechanisms of Dyspnea in Chronic Interstitial and Obstructive Lung Disorders.

Am J Respir Crit Care Med 2016 Feb;193(3):299-309

1 Respiratory Investigation Unit, Department of Medicine, Queen's University and Kingston General Hospital, Kingston, Ontario, Canada.

Rationale: The mechanisms underlying dyspnea in interstitial lung disease (ILD) and chronic obstructive pulmonary disease (COPD) are unknown.

Objectives: To examine whether the relationship between inspiratory neural drive to the diaphragm and exertional dyspnea intensity is different in ILD and COPD, given the marked differences in static respiratory mechanics between these conditions.

Methods: We compared sensory-mechanical relationships in patients with ILD, patients with COPD, and healthy control subjects (n = 16 each) during incremental cycle exercise with diaphragmatic electromyography (EMGdi) and respiratory pressure measurements.

Measurements And Main Results: In patients with mild to moderate ILD or COPD with similarly reduced inspiratory capacity, the peak oxygen uptake, work rate, and ventilation were lower (P < 0.05) than in healthy control subjects. EMGdi expressed as a percentage of the maximum (EMGdi/EMGdi,max), respiratory effort (esophageal pressure expressed as percentage of the maximum), and ventilation were higher (P < 0.05) at rest and during exercise in both patients with ILD and patients with COPD than in control subjects. Each of these measurements was similar in the ILD and COPD groups. A Vt inflection and critically reduced inspiratory reserve volume occurred at a lower (P < 0.05) ventilation in the ILD and COPD groups than in control subjects. Patients with ILD had greater diaphragmatic activity, whereas patients with COPD had greater expiratory muscle activity. The relationship between dyspnea intensity and EMGdi/EMGdi,max during exercise was similar in all three groups. In ILD and COPD, descriptors alluding to inspiratory difficulty were selected more frequently, with a greater disparity between EMGdi/EMGdi,max and Vt.

Conclusions: Disease-specific differences in mechanics and respiratory muscle activity did not influence the key association between dyspnea intensity and inspiratory neural drive to the diaphragm.
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http://dx.doi.org/10.1164/rccm.201504-0841OCDOI Listing
February 2016

Physiological impairment in mild COPD.

Respirology 2016 Feb 2;21(2):211-23. Epub 2015 Sep 2.

Department of Medicine, Division of Respiratory and Critical Care Medicine, Queen's University and Kingston General Hospital, Kingston, Ontario, Canada.

Chronic obstructive pulmonary disease (COPD) is a common and often progressive inflammatory disease of the airways, alveoli and microvasculature that is both preventable and treatable. It is well established that smokers with mild airway obstruction, as spirometrically defined, represent the vast majority of patients with COPD, yet this population has not been extensively studied. An insidious preclinical course means that mild COPD is both underdiagnosed and undertreated. In this context, recent studies have confirmed that even patients with mild COPD can have extensive physiological impairment, which contributes to poor perceived health status compared with non-smoking healthy controls. This review describes the heterogeneous pathophysiology that can exist in COPD patients with only mild airway obstruction on spirometry. It exposes the compensatory adaptations that develop in such patients to ensure that the respiratory system fulfils its primary task of maintaining adequate pulmonary gas exchange for the prevailing metabolic demand. It demonstrates that adaptations such as increased inspiratory neural drive to the diaphragm due to combined effects of increased mechanical loading and chemostimulation underscore the increased dyspnoea and exercise intolerance in this population. Finally, based on available evidence, we present what we believe is a sound physiological rationale for earlier diagnosis in this population.
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http://dx.doi.org/10.1111/resp.12619DOI Listing
February 2016

Pulmonary Gas Exchange Abnormalities in Mild Chronic Obstructive Pulmonary Disease. Implications for Dyspnea and Exercise Intolerance.

Am J Respir Crit Care Med 2015 Jun;191(12):1384-94

1 Respiratory Investigation Unit, Department of Medicine, Queen's University and Kingston General Hospital, Kingston, Ontario, Canada.

Rationale: Several studies in mild chronic obstructive pulmonary disease (COPD) have shown a higher than normal ventilatory equivalent for carbon dioxide ([Formula: see text]e/[Formula: see text]co2) during exercise. Our objective was to examine pulmonary gas exchange abnormalities and the mechanisms of high [Formula: see text]e/[Formula: see text]co2 in mild COPD and its impact on dyspnea and exercise intolerance.

Methods: Twenty-two subjects (11 patients with GOLD [Global Initiative for Chronic Obstructive Lung Disease] grade 1B COPD, 11 age-matched healthy control subjects) undertook physiological testing and a symptom-limited incremental cycle exercise test with arterial blood gas collection.

Measurements And Main Results: Patients (post-bronchodilator FEV1: 94 ± 10% predicted; mean ± SD) had evidence of peripheral airway dysfunction and reduced peak oxygen uptake compared with control subjects (80 ± 18 vs. 113 ± 24% predicted; P<0.05). Arterial blood gases were within the normal range and effective alveolar ventilation was not significantly different from control subjects throughout exercise. The alveolar-arterial O2 tension gradient was elevated at rest and throughout exercise in COPD (P<0.05). [Formula: see text]e/[Formula: see text]co2, dead space to tidal volume ratio (Vd/Vt), and arterial to end-tidal CO2 difference were all higher (P<0.05) in patients with COPD than in control subjects during exercise. In patients with COPD versus control subjects, there was significant dynamic hyperinflation and greater tidal volume constraints (P<0.05). Standardized dyspnea intensity ratings were also higher (P<0.05) in patients with COPD versus control subjects in association with higher ventilatory requirements. Within all subjects, Vd/Vt correlated with the [Formula: see text]e/[Formula: see text]co2 ratio during submaximal exercise (r=0.780, P<0.001).

Conclusions: High Vd/Vt was the most consistent gas exchange abnormality in smokers with only mild spirometric abnormalities. Compensatory increases in minute ventilation during exercise maintained alveolar ventilation and arterial blood gas homeostasis but at the expense of earlier dynamic mechanical constraints, greater dyspnea, and exercise intolerance in mild COPD.
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http://dx.doi.org/10.1164/rccm.201501-0157OCDOI Listing
June 2015
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