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Randomized Controlled Trial
. 2012 Jan;106(1):109-19.
doi: 10.1016/j.rmed.2011.07.012. Epub 2011 Aug 16.

Lung deflation and oxygen pulse in COPD: results from the NETT randomized trial

Carolyn E Come  1 , Miguel J Divo, Raúl San José Estépar, Frank C Sciurba, Gerard J Criner, Nathaniel Marchetti, Steven M Scharf, Zab Mosenifar, Barry J Make, Cesar A Keller, Omar A Minai, Fernando J Martinez, MeiLan K Han, John J Reilly, Bartolome R Celli, George R Washko; NETT Research Group
Collaborators, Affiliations
Randomized Controlled Trial

Lung deflation and oxygen pulse in COPD: results from the NETT randomized trial

Carolyn E Come et al. Respir Med. 2012 Jan.

Abstract

Background: In COPD patients, hyperinflation impairs cardiac function. We examined whether lung deflation improves oxygen pulse, a surrogate marker of stroke volume.

Methods: In 129 NETT patients with cardiopulmonary exercise testing (CPET) and arterial blood gases (ABG substudy), hyperinflation was assessed with residual volume to total lung capacity ratio (RV/TLC), and cardiac function with oxygen pulse (O(2) pulse=VO(2)/HR) at baseline and 6 months. Medical and surgical patients were divided into "deflators" and "non-deflators" based on change in RV/TLC from baseline (∆RV/TLC). We defined deflation as the ∆RV/TLC experienced by 75% of surgical patients. We examined changes in O(2) pulse at peak and similar (iso-work) exercise. Findings were validated in 718 patients who underwent CPET without ABGs.

Results: In the ABG substudy, surgical and medical deflators improved their RV/TLC and peak O(2) pulse (median ∆RV/TLC -18.0% vs. -9.3%, p=0.0003; median ∆O(2) pulse 13.6% vs. 1.8%, p=0.12). Surgical deflators also improved iso-work O(2) pulse (0.53 mL/beat, p=0.04 at 20 W). In the validation cohort, surgical deflators experienced a greater improvement in peak O(2) pulse than medical deflators (mean 18.9% vs. 1.1%). In surgical deflators improvements in O(2) pulse at rest and during unloaded pedaling (0.32 mL/beat, p<0.0001 and 0.47 mL/beat, p<0.0001, respectively) corresponded with significant reductions in HR and improvements in VO(2). On multivariate analysis, deflators were 88% more likely than non-deflators to have an improvement in O(2) pulse (OR 1.88, 95% CI 1.30-2.72, p=0.0008).

Conclusion: In COPD, decreased hyperinflation through lung volume reduction is associated with improved O(2) pulse.

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Figures

Figure 1
Figure 1
Consort diagram of the study cohorts. 1218 patients were enrolled in NETT. Of those, 847 completed baseline and 6 month follow-up non-invasive cardiopulmonary exercise tests (CPET) and had pulmonary function tests. Of the original 1218 patients, 238 were simultaneously enrolled in the ABG substudy. Of these, 129 had baseline and follow-up CPET data and had normal respiratory exchange ratios (RER). These 129 overlapped completely with the 847 patients. Therefore, the two groups were treated as separate cohorts (*): ABG substudy (N=129), validation cohort (N=847–129=718). 67 patients from the ABG substudy cohort met criteria for inclusion in the iso-work analysis.
Figure 2
Figure 2
Percent change in ratio of residual volume to total lung capacity (RV/TLC) from baseline to 6 month follow-up (panel A) and percent change in O2 pulse from baseline to 6 month follow-up (panel B) according to treatment assignment (medical vs. surgical) and deflator status for patients in the ABG substudy. Med-ND = medical non-deflator (N=52), Med-D = medical deflator (N=15), Surg-ND = surgical non-deflator (N=15), Surg-D = surgical deflator (N=47).
Figure 3
Figure 3
Comparison of baseline (â–´) and 6 month follow-up (â– ) values for O2 pulse (panel A), oxygen uptake (VO2, panel B), and heart rate (HR, panel C) at iso-work in surgical deflators included in the ABG substudy (N=24). Data is presented as means and standard deviations. *p < 0.05.
Figure 4
Figure 4
Comparison of baseline (â–´) and 6 month follow-up (â– ) values for O2 pulse (panel A), oxygen uptake (VO2, panel B), and heart rate (HR, panel C) at iso-work in surgical deflators in the validation cohort (N=303). Data is presented as means and standard deviations. *p < 0.05.
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References

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