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Evaluation of Cardiorespiratory Function During Cardiopulmonary Exercise Testing in Untreated Hypertensive and
Yahui Zhang1, Zhihao Jiang1, Lin Qi1
1Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang City, China.
Insights
Cardiopulmonary exercise testing reveals distinct cardiorespiratory function differences in untreated hypertensive subjects compared to healthy individuals, highlighting cardiovascular risks and arterial stiffness.
Area of Science:
- Cardiology
- Exercise Physiology
- Biomedical Engineering
Background:
- Untreated hypertension (UHS) poses significant cardiovascular risks.
- Cardiopulmonary exercise testing (CPET) is crucial for assessing cardiorespiratory function.
- Understanding exercise responses in UHS is vital for risk stratification.
Purpose of the Study:
- Compare cardiorespiratory function between UHS and healthy subjects (HS) during CPET.
- Explore mechanisms behind differing exercise responses in UHS.
- Identify potential predictors of arterial stiffness in UHS.
Main Methods:
- Simultaneous collection of photoplethysmography (PPG), respiratory signals, and ECG during CPET.
- Analysis of PPG fiducial points (a-e) and derived ratios (b/a, c/a, d/a, e/a, Aging Index - AGI) for systolic and diastolic function.
- Calculation and analysis of respiratory rate during CPET.
Main Results:
- After CPET, UHS showed significantly higher b/a and AGI, and lower d/a and c/a compared to HS.
- Before CPET, UHS had a significantly lower e/a ratio than HS.
- During CPET, UHS exhibited significantly higher AGI and respiratory rate compared to pre-CPET levels.
Conclusions:
- Exercise responses during CPET reveal significant cardiorespiratory function differences between UHS and HS.
- These differences can indicate cardiovascular risk and predict arterial stiffness in UHS.
- CPET effectively highlights alterations in autonomic nervous function and respiratory activity in UHS.
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.
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