Combining Dynamic Hyperinflation with Dead Space Volume during Maximal Exercise in Patients with Chronic Obstructive Pulmonary Disease

Abstract

Physiological dead space volume (V D ) and dynamic hyperinflation (DH) are two different types of abnormal pulmonary physiology. Although they both involve lung volume, their combination has never been advocated, and thus their effect and implication are unclear. This study aimed (1) to combine V D and DH, and (2) investigate their relationship and clinical significance during exercise, as well as (3) identify a noninvasive variable to represent the V D fraction of tidal volume (V D /V T ). Forty-six male subjects with chronic obstructive pulmonary disease (COPD) and 34 healthy male subjects matched for age and height were enrolled. Demographic data, lung function, and maximal exercise were investigated. End-expiratory lung volume (EELV) was measured for the control group and estimated for the study group using the formulae reported in our previous study. The V D /V T ratio was measured for the study group, and reference values of V D /V T were used for the control group. In the COPD group, the DH peak /total lung capacity (TLC, DH peak %) was 7% and the EELV peak % was 70%. After adding the V Dpeak % (8%), the V D DH peak % was 15% and the V D EELV peak % was 78%. Both were higher than those of the healthy controls. In the COPD group, the V D DH peak % and V D EELV peak % were more correlated with dyspnea score and exercise capacity than that of the DH peak % and EELV%, and had a similar strength of correlation with minute ventilation. The V Tpeak /TLC (V Tpeak %), an inverse marker of DH, was inversely correlated with V D /V T (R 2 ≈ 0.50). Therefore, we recommend that V D should be added to DH and EELV, as they are physiologically meaningful and V Tpeak % represents not only DH but also dead space ventilation. To obtain V D , the V D /V T must be measured. Because obtaining V D /V T requires invasive arterial blood gases, further studies on noninvasive predicting V D /V T is warranted.

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

“…V T /IC and V T / VC and V T /FEV 1 (emphysema factor) [13] and dynamic hyperinflation (DH) as represented by EELV peak /TLC [11] have been reported to be mildly to moderately negatively related toVE=VCO2S in the literature (Supplementary Table, r = − 0.31 --0.35 and − 0.48 --0.60). However, in the current study, even though none of the markers of volume excursion and DH as represented by V T /TLC [38,39] were related toVE=VCO2S, the emphysema factor was mildly negatively related toVE=VCO2S (r = − 0.32).…”

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

“…However, in this study, V D /V T R was not correlated with the lung function variables suggesting that V D /V T and lung hyperinflation, air trapping or diffusing capability might be different components in physiology. 22 V D /V T R was correlated with cigarette consumption, carboxyhemoglobin, and pulmonary hypertension measured by chest radiography ( Table 4 ). Thus, V D /V T R may offer additional information to lung function test, whereas FEV 1 %, RV/TLC, and D L CO% were more related to lung function test ( Table 4 ).…”

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

“…We established 6MWT distance by having our participants walk back and forth on a 30 m-long walkway with two cones placed at both ends, and we recorded changes in oxygen saturation and perceived exertion on the Borg scale during 6MWT. In addition, a cardiopulmonary exercise test can detect any gas exchange abnormalities during exercise in patients with COPD [ 28 , 29 ]. Patients with COPD have a higher VE/VCO 2 slope [ 29 ] and Vd/Vt [ 28 ] during exercise.…”

“…In addition, a cardiopulmonary exercise test can detect any gas exchange abnormalities during exercise in patients with COPD [ 28 , 29 ]. Patients with COPD have a higher VE/VCO 2 slope [ 29 ] and Vd/Vt [ 28 ] during exercise. In this study, we measured these parameters during peak exercise.…”