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Assessment of Pulmonary Capillary Blood Volume, Membrane Diffusing Capacity, and Intrapulmonary Arteriovenous Anastomoses During Exercise

Assessment of Pulmonary Capillary Blood Volume, Membrane Diffusing Capacity, and Intrapulmonary Arteriovenous Anastomoses During Exercise

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

Ming-Lung Chuang^1,2

¹Department of Internal Medicine and Division of Pulmonary Medicine, Chung Shan Medical University Hospital, #110, Section 1, Chien-Kuo North Road, South District, Taichung, 40201, Taiwan, Republic of China. yuan1007@ms36.hinet.net.

Respiratory Research

|August 9, 2020

Abstract

Background:

Exercise ventilatory inefficiency is usually defined as high ventilation ([Formula: see text]) versus low CO₂ 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 (FEV₁%) (r = - 0.27), and hence the FEV₁%- [Formula: see text] relationship was paradoxical. The higher the [Formula: see text], the higher the pH and P_aO₂, and the lower the P_aCO₂ 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 .

Keywords:

Dead space and tidal volume ratio Incremental exercise test Intercept for ventilation versus CO2 output Obstructive airway disease Slope for ventilation versus CO2 output Ventilatory equivalents for oxygen and CO2

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