Resting Dead Space Fraction as Related to Clinical Characteristics, Lung Function, and Gas Exchange in Male Patients with Chronic Obstructive Pulmonary Disease

Abstract

Background Measures of forced expired volume in one second % predicted (FEV 1 %), residual volume to total lung capacity ratio (RV/TLC) and diffusing capacity for carbon monoxide measurements (D L CO) are the standard lung function test for evaluating patients with chronic obstructive pulmonary disease (COPD). The dead space fraction (V D /V T ) has been shown to be a robust marker of gas exchange abnormality. However, the use of V D /V T has gradually become less common. As V D /V T measured at rest (V D /V T R) has been successfully used in non-COPD conditions, it was hypothesized that in COPD the V D /V T R was more sensitive than the standard lung function test in correlation with clinical characteristics and gas exchange. This study aimed to test the hypothesis and to identify the variables relevant to V D /V T R. Methods A total of 46 male subjects with COPD were enrolled. Clinical characteristics included demographic data, oxygen-cost diagram (OCD), and image studies for pulmonary hypertension. The standard lung function was obtained. To calculate V D /V T , invasive arterial blood gas and pulmonary gas exchange (PGX) were measured. The variables relevant to V D /V T R were analyzed by multiple linear regression. Results Compared to lung function, V D /V T R was more frequently and significantly related to smoking, carboxyhemoglobin level, pulmonary hypertension and P a CO 2 (all p <0.05) whereas FEV 1 % was more related to lung function test, P a O 2 and OCD score. V D /V T R and FEV 1 % were highly related to resting gas exchange but RV/TLC and D L CO% were not. Cigarette consumption, the equivalent for CO 2 output, arterial oxyhemoglobin saturation, and the product of tidal volume and inspiratory duty cycle were identified as the parameters relevant to V D /V T R with a power of 0.72. Conclusion Compared to lung function test, V D /V T R is more related to clinical characteristics and is a comprehensive marker of resting gas exchange. Further studies are warranted to provide a noninvasive measurement...

The Independent Contribution of Estimated Dead Space Fraction to Other Common Variables for Survival Analysis in Patients with Chronic Obstructive Pulmonary Disease

“…The mechanism underlying the predictive ability of estV D /V Trest for COPD death is not clear; however, it may be due to its broad associations with lung and non-lung factors. 23 Based on the hierarchical strati cation concept, estV D /V Trest was the primary pulmonary factor and BMI was the non-pulmonary factor.…”

“…However, V D /V T can be estimated using statistical methods. 23,32 In this study, V D /V Trest and V D /V Tpeak were obtained using simpli ed versions of the equations using multiple linear regression analysis as follows: estV D /V Trest = 1.18449 + 0.00356 ⋅ age − 0.00416 ⋅ height − 0.05676 ⋅ FRC% − 0.12206 ⋅ FEV 1 /FVC (r 2 = 0.28, p = 0.01) and estV D /V Tpeak = 0.48428 − 0.00189 ⋅ Weight − 0.07579 ⋅ TLC% + 0.42374 ⋅ RV/TLC − 0.11938 ⋅ D L CO% (r 2 = 0.31, p = 0.007), where FRC% is functional residual capacity % predicted, FVC is forced vital capacity, TLC% is total lung capacity % predicted, RV is residual volume. These formulae were revised from our previous reports using fewer and available variables for simplicity and generalizability.…”

“…These formulae were revised from our previous reports using fewer and available variables for simplicity and generalizability. 23,32 For the original equations from our previous reports, please refer to the Appendix.…”

“…It is related to FEV 1 and is more related to clinical characteristics and gas exchange than FEV 1 . 22,23 V D /V T has yet to be shown to a predictor of COPD mortality; however, it is related to hypoxemia and hypercapnia, which are related to mortality. 18,24−26 However, to obtain V D /V T invasive arterial catheterization must be established, and applying an invasive method in a large-scale study is di cult.…”

Respiratory Muscle Training Can Improve Cognition, Lung Function, and Diaphragmatic Thickness Fraction in Male and Non-Obese Patients with Chronic Obstructive Pulmonary Disease: A Prospective Study

“…The VE/VCO 2 slope, also known as exercise ventilatory efficiency, is an essential prognostic factor in COPD. Vd/Vt, also called the dead space fraction, is considered a comprehensive marker of gas exchange in patients with COPD [ 40 ]. RMT cannot enhance ventilator efficiency, and the dead space fraction is probably because RMT can only improve respiratory muscle strength, and not alveolar function of gas exchange.…”