Evaluation of Cardiorespiratory Function During Cardiopulmonary Exercise Testing in Untreated Hypertensive and Healthy Subjects

Yahui Zhang; Zhihao Jiang; Lin Qi; Lisheng Xu; Xingguo Sun; Xinmei Chu; Yanling Liu; Tianjing Zhang; Stephen E Greenwald

doi:10.3389/fphys.2018.01590

Evaluation of Cardiorespiratory Function During Cardiopulmonary Exercise Testing in Untreated Hypertensive and Healthy Subjects

Front Physiol. 2018 Nov 14:9:1590. doi: 10.3389/fphys.2018.01590. eCollection 2018.

Authors

Yahui Zhang¹, Zhihao Jiang¹, Lin Qi¹, Lisheng Xu¹, Xingguo Sun², Xinmei Chu³, Yanling Liu⁴, Tianjing Zhang², Stephen E Greenwald⁵

Affiliations

¹ Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang City, China.
² Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Science, Beijing, China.
³ Beijing Haidian Hospital, Peking University Third Hospital Haidian Campus, Beijing, China.
⁴ Beijing Rehabilitation Hospital of Capital Medical University, Beijing, China.
⁵ Blizard Institute, Barts, The London School of Medicine, Dentistry, Queen Mary University of London, London, United Kingdom.

Abstract

Objective: This study aimed to compare differences in cardiorespiratory function between untreated hypertensive subjects (UHS) and healthy subjects (HS) during cardiopulmonary exercise testing (CPET). Additionally, it also aimed to explore the potential mechanisms of different exercise responses in cardiorespiratory function before, during and after CPET. Methods: Thirty subjects (15 UHS and 15 HS) were enrolled. Photoplethysmography (PPG), respiratory signal, and ECG were simultaneously collected while subjects were performing CPET. Fiducial points (a, b, c, d, e) were extracted from the second derivative of the PPG (SDPPG), and the ratios b/a, c/a, d/a, e/a, and (b-c-d-e)/a (named Aging Index, AGI) were calculated as markers of systolic and diastolic function. Additionally, respiratory rate was calculated and analyzed. Results:Before CPET, there were no significant differences in b/a, d/a, and AGI between two groups. However, after CPET, b/a (-0.9 ± 0.19 vs. -1.06 ± 0.19, p-value = 0.03) and AGI (-0.49 ± 0.75 vs. -1.15 ± 0.59, p-value = 0.011) of the UHS group were significantly higher than those of the HS. The d/a (-0.32 ± 0.24 vs. -0.14 ± 0.17, p-value = 0.024), and c/a (-0.33 ± 0.26 vs. -0.07 ± 0.19, p-value = 0.004) were significantly lower in UHS than those in HS. In contrast, before CPET, e/a (0.22 ± 0.11 vs. 0.32 ± 0.09, p-value = 0.007) in UHS was significantly lower than that in HS, while after CPET there was no significant difference between the two groups in this variable. In addition, during CPET, AGI (p-value = 0.003), and respiratory rate (p-value = 0.000) in UHS were significantly higher in comparison with before CPET. Conclusions: Different exercise responses showed the differences of cardiorespiratory function between UHS and HS. These differences not only can highlight the CV risk of UHS, but also can predict the appearance of arterial stiffness in UHS. Additionally, during CPET, significant differences in AGI, autonomic nervous function and respiratory activity assessed by respiratory rate were found between the two groups in comparison with before CPET.

Keywords: SDPPG; cardiopulmonary exercise testing (CPET); cardiorespiratory function; healthy subject; untreated hypertensive subject.