Obstructive Lung Diseases: Airways 3 |

Alveolar-Capillary Reserve During Exercise in Patients With COPD FREE TO VIEW

Mehrdad Behnia, MD; Alberto Avolio, PhD; Bruce Johnson, PhD
Author and Funding Information

Macquarie University, Sydney, NSW, Australia

Copyright 2016, American College of Chest Physicians. All Rights Reserved.

Chest. 2016;150(4_S):851A. doi:10.1016/j.chest.2016.08.951
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Published online


SESSION TYPE: Original Investigation Poster

PRESENTED ON: Wednesday, October 26, 2016 at 01:30 PM - 02:30 PM

PURPOSE: Factors limiting exercise capacity in patients with COPD are complex. With evidence for accelerated pulmonary vascular aging, destruction of the alveolar-capillary bed, heterogeneous hypoxic pulmonary vasoconstriction, the ability to functionally expand the alveolar-capillary bed during exercise may become limiting. The purpose of this study was to quantify alveolar-capillary recruitment during exercise and the relationship to exercise capacity in a cohort of COPD patients.

METHODS: 32 subjects gave informed consent for participation in the study (53% male, age 66±9 yrs, smoking hx 35±29 pkyr, 2.3±0.8 on the 0-4 GOLD scale), filled out a QOL questionnaire (St George), had a CBC drawn, performed spirometry, and had exhaled nitric oxide (exNO) measured. They also performed the intra-breath (IB) technique for lung diffusing capacity for carbon monoxide (IBDLCO) as well as pulmonary blood flow (IBQc). Subsequently they completed a progressive cycle ergometry test to exhaustion with measures of oxygen saturation (SaO2) and expired gases. The IBDLCO and IBQc were measured during the first exercise workload and also at rest in all subjects.

RESULTS: Most subjects were on multiple inhaled medications with 20% oral steroids. Baseline averages were: 44±21 for QOL (range 8-84), 21±17ppb for exNO (range 5-89), and 58±10 for FEV1/FVC %Pred (range 33-78%). Peak VO2 averaged 11.4±3.1 ml/kg/min. The mean resting IBDLCO was 9.7±5.4 ml/min/mmHg and IBQc 4.7±0.9 L/min. At the first workload, HR increased to 92±11bpm, VO2 averaged 8.3±1.4 ml/kg/min and the IBDLCO and IBQc increased by 46 and 43% respectively (p<0.01 relative to rest). The IBDLCO/Q ratio at rest averaged 2.0±1.1 and remained essentially constant during exercise with significant variation across individuals (range 0.8-4.8). The exercise IBDLCO/Qc ratio was significantly related to O2 pulse (VO2/HR, r=0.58, p<0.01) and subjects with the highest exercise IBDLCO/Q ratio or the greatest rise in this ratio from rest had the highest VO2 peak values (r=0.65 and 0.51 respectively).

CONCLUSIONS: COPD patients who can expand gas exchange surface area during exercise relative to pulmonary blood flow have more preserved exercise capacities.

CLINICAL IMPLICATIONS: The subclass of COPD patients with a more efficient alveoalr-capillary recruitment during exercise, are the ones who have the best exercise tolerance. Cardiopulmonary exercise testing is recommended in COPD patients for stratification.

DISCLOSURE: The following authors have nothing to disclose: Mehrdad Behnia, Alberto Avolio, Bruce Johnson

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