Mechanisms affecting exercise ventilatory inefficiency-airflow obstruction relationship in male patients with chronic obstructive pulmonary disease

摘要

BACKGROUND:Exercise ventilatory inefficiency is usually defined as high ventilation ([Formula: see text]) versus low CO 2 output ([Formula: see text]). The inefficiency may be lowered when airflow obstruction is severe because [Formula: see text] cannot be adequately increased in response to exercise. However, the ventilatory inefficiency-airflow obstruction relationship differs to a varying degree. This has been hypothesized to be affected by increased dead space fraction of tidal volume (V D /V T ), acidity, hypoxemia, and hypercapnia.METHODS:A total of 120 male patients with chronic obstructive pulmonary disease were enrolled. Lung function and incremental exercise tests were conducted, and [Formula: see text] versus [Formula: see text] slope ([Formula: see text]) and intercept ([Formula: see text]) were obtained by linear regression. Arterial blood gas analysis was also performed in 47 of the participants during exercise tests. V D /V T and lactate level were measured.RESULTS:V D /V Tpeak was moderately positively related to [Formula: see text] (r?=?0.41) and negatively related to forced expired volume in 1 sec % predicted (FEV 1 %) (r?=?-?0.27), and hence the FEV 1 %- [Formula: see text] relationship was paradoxical. The higher the [Formula: see text], the higher the pH and P a O 2 , and the lower the P a CO 2 and exercise capacity. [Formula: see text] was marginally related to V D /V Trest . The higher the [Formula: see text], the higher the inspiratory airflow, work rate, and end-tidal PCO 2peak .CONCLUSION:1) Dead space ventilation perturbs the airflow- [Formula: see text] relationship, 2) increasing ventilation thereby increases [Formula: see text] to maintain biological homeostasis, and 3) the physiology- [Formula: see text]- [Formula: see text] relationships are inconsistent in the current and previous studies.TRIAL REGISTRATION:MOST 106-2314-B-040-025 .