Applying novel wearables to perform cardiovascular and hemodynamic monitoring in parabolic flights

Introduction:

With the upcoming Artemis lunar missions and the rise of commercial spaceflight, the void in our knowledge of space physiology poses a significant threat to our astronaut's health and mission success. Although advancements in aerospace medicine have improved our understanding of the physiological adaptations to gravitational changes, they remain incompletely characterized. Wearable technology offers a compact, efficient solution for real-time monitoring of vital parameters, essential for assessing the physiological demands of space missions. This study utilizes an advanced wearable sensor to evaluate cardiopulmonary responses under varying gravitational forces experienced during parabolic flights, aiming to enhance current knowledge of cardiovascular adaptation in altered gravity environments.

Methods: 

Parabolic flights were conducted aboard the A310 ZERO-G aircraft, collaborating with Novespace, to simulate microgravity, normogravity, and hypergravity conditions. Each flight consisted of 31 parabolas, including approximately 20–30 seconds of hypergravity (up to 1.8 G) during ascent and descent, separated by 20-second microgravity intervals. Continuous monitoring of cardiopulmonary parameters—including respiratory rate, pulse pressure, oxygen saturation (SpO₂), body temperature, cardiac output, heart rate, stroke volume, systemic vascular resistance, systolic and diastolic blood pressure, and heart rate variability—was achieved using a wearable chest-patch sensor with photoplethysmography technology. Data were recorded at 5-second intervals for eight upright-positioned subjects. Statistical analysis was performed with the Friedman test, followed by post-hoc tests for pairwise comparisons across gravitational conditions.

Results: 

Data collection was successful for all subjects, yielding high-quality data in 197 of 248 parabolas. A significant increase in respiratory rate was observed under both hypergravity [mean 15.7/min versus 15.2/min, IQR: 13–18, p < 0.01] and microgravity [mean 16.4/min versus 15.2/min, IQR: 15–18, p < 0.01], indicating a measurable respiratory response to gravitational shifts. Oxygen saturation levels remained stable across all gravitational phases, showing no significant difference between hypergravity and microgravity. Although blood pressure was continuously monitored, the data revealed inconsistent patterns without a clear correlation to the gravitational phase. Stroke volume remained unchanged across all phases, suggesting minimal circulatory adaptation in this parameter. Results were consistent when analyzed both individually and as a group.

Conclusion:

This study demonstrates the feasibility of using wearable photoplethysmography for continuous cardiopulmonary monitoring in variable gravitational environments encountered during parabolic flights. The findings confirm the practical application of wearable technology in spaceflight and contribute valuable insights into the physiological stress associated with altered gravity. While some observed cardio-circulatory adaptations align with known principles of space physiology, other findings suggest potential areas for further investigation. Future studies should validate wearable sensor data against standardized measurements under these conditions. A controlled gravitational setup could further clarify the circulatory adaptations observed in this study, advancing the understanding of human physiology in spaceflight contexts.