Obstructive Lung Diseases: COPD |

Influence of Lung Diffusion on Exercise Capacity in Patients With COPD FREE TO VIEW

Mehrdad Behnia, MD; Courtney Wheatley, PhD; Alberto Avolio, PhD; Bruce Johnson, PhD
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Macquarie University, Sydney, NSW, Australia

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

Chest. 2016;150(4_S):891A. doi:10.1016/j.chest.2016.08.991
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SESSION TYPE: Original Investigation Poster Discussion

PRESENTED ON: Monday, October 24, 2016 at 12:00 PM - 01:30 PM

PURPOSE: Factors contributing to exercise intolerance in patients with COPD remain complex. Lung diffusing capacity for carbon monoxide (DLCO) gives an overall assessment of functional lung surface area for gas exchange and can be assessed by various methods. We were interested if the intra-breath method may give a more sensitive measure of useable gas exchange surface area than the more typical single breath method and if subjects with the largest DLCO relative to pulmonary blood flow (Qc) would have a more preserved exercise capacity.

METHODS: Included obtaining informed consent, St George Quality of Life (QOL) questionnaire, hemoglobin, spirometry, exhaled nitric oxide (exNO), single breath (SB) DLCO, intra-breath (IB) DLCO, with Qc determination during the IBDLCO method; then followed by a progressive cycle ergometry test to exhaustion with measures of oxygen saturation (SaO2) and expired gases.

RESULTS: 32 subjects (47% female, 66±9 yrs, BMI 30.4±6.3 kg/m2, smoking hx 35±29 pkyrs, 2.3±0.8 on the 0-4 GOLD scale) participated. Most were on multiple inhaled medications with 20% on oral steroids. Baseline averages were: 44±21 for QOL (range 8-84), 21±17 for exNO (range 5-89), and 58±10 for FEV1/FVC % Pred (range 33 to 78%). Peak VO2 averaged 11.4±3.1 ml/kg/min and the IBDLCO averaged 72% of the SBDLCO (r=0.88, SB vs IB methods). Using univariate regression, both the SB and IBDLCO were predictive of VO2peak; but the SBDLCO/Qc ratio (r=0.63, p<0.001) was the best predictor of exercise capacity (VO2peak expressed in ml/kg/min) with maximal expiratory flows over the mid to lower lung volumes being the most significant predictors (r=0.49, p<0.01). Using multiple and stepwise regression, only BMI added additional predictive value to the SBDLCO/Qc for predicting aerobic capacity (r=0.73).

CONCLUSIONS: In moderate to severe COPD, preservation of lung gas exchange surface area as assessed using the resting SBDLCO method relative to Qc, is a better predictor of exercise capacity than more classic measures of lung mechanics.

CLINICAL IMPLICATIONS: SBDLCO is recommended as a more reliable predcitor of exercse tolerance in COPD than spirometry alone.

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

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