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.
PurposeHypoxemia is associated with more severe lung disease and worse outcomes. In some patients with chronic obstructive lung diseases who desaturate on exertion, supplemental oxygen improves exercise capacity. The clinical significance of this exercise response to oxygen supplementation is not known.Patients and methodsWe identified chronic obstructive lung disease patients at our center who underwent a 6-minute walking test (6MWT) for ambulatory oxygen assessment and who desaturated breathing air and therefore had an additional walk test on supplemental oxygen, between August 2006 and June 2016. Responders were defined as walking ≥26 m further with oxygen. Survival was determined up to February 1, 2017. We compared survival in oxygen responders and nonresponders in patients with obstructive lung diseases.ResultsOne hundred and seventy-four patients were included in the study, median age 70 years. Seventy-seven (44.3%) of the patients were oxygen responders. Borg dyspnea score improved by 1.4 (±1.4) units (P<0.0005) on oxygen. Median survival was 66 months with death occurring in 84 (48.2%) patients. Kaplan–Meier analysis revealed no survival difference between both responders and nonresponders (P=0.571). Cox regression analysis showed that more 6MWT desaturation, lower 6-minute walking distance on room air, male gender, lower hemoglobin, and body mass index were associated with higher mortality risk.ConclusionAcute exercise response to supplemental oxygen is not associated with long-term survival in patients with obstructive lung disease. This supports the use of ambulatory oxygen treatment for symptomatic purposes only.
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