Real-time evaluation of pulmonary ventilation of HP movements based on electrical impedance tomography: an observational study

Objective To explore the feasibility of electrical impedance tomography (EIT) for real-time and accurate monitoring of respiration during HP anti-G movements and the key parameters of pulmonary ventilation. Methods Twelve healthy male students in our university were enrolled in September 2023 and subjected in this study. HP anti-G movements were performed 3 times each for 30 s in the anti-G physiological training apparatus, during which EIT and ophthalmic horizontal arterial pressure were measured to analyze the relationship of the global and local parameters of pulmonary ventilation, including inspiratory volume (IV), expiratory uniform (EU), expiratory speed (ES), center of ventilation (COV) and right-to-left lung ventilation ratio (RtoL) with anti-G ability of anti-G straining maneuver (AGSM). Results The average eye horizontal systolic blood pressure (SBP) at the eye level was 148.82±22.75 mmHg during HP anti-G movements, which was significantly higher than that during quiet breathing (PJ) (95.17±8.51 mmHg, P < 0.001). From the global pulmonary ventilation, the participants had significantly increased IV during HP anti-G movements (P < 0.001). According the d value (mean increase of eye horizontal SBP=SBPHP - SBPPJ), the subjects were divided into 3 groups, with the d value of >60, 30~60 and < 30 mmHg, respectively. The inspiratory volume ratio (IVHP/IVPJ) was the highest in the >60 mmHg group and the smallest in the < 30 mmHg group (P < 0.01). The subjects had significantly decreased EU and more evenly expiration (P < 0.05), but no change was seen in the expiratory uniformity ratio (EUHP/EUPJ) among the 3 groups. ES was obviously faster during HP anti-G movements (P < 0.001), and the expiratory speed ratio (ESHP/ESPJ) had no significant difference among the 3 groups. The inspiratory time and expiratory time were 0.77±0.32 and 1.59±0.21 s, respectively, and both of them were notably shorter during HP anti-G movements (P < 0.001, P < 0.01). From the local pulmonary ventilation, COV during HP anti-G movements was significantly smaller than that during PJ (P < 0.001), and the ventilation center deviated to the ventral side, and RtoL was decreased and the ventilation distribution deviated to the left lung (P < 0.05). Conclusion EIT can perform real-time imaging of pulmonary global and local ventilation during HP anti-G movements, and it has a great application prospect in AGSM training and monitoring.