Variations of human heart bioelectrical signals at hypoxic exposure

Abstract

BACKGROUND: In the area of physiology and medicine, special emphasis is placed on the study of hypoxic conditions. Hypoxic responses of some major physiological systems, including blood circulation, are described. However, the cardiological component of these individual responses, and their variability at different levels of acute hypoxia (AH) remains a poorly-studied aspect.
 AIM: To study the individual characteristics of the response types in conjugated ECG parameters, and their variations at different stages of mild and medium AH.
 MATERIAL AND METHODS: The experiments were performed on male subjects (1826 years old) divided into two groups (n1=30 and n2=29), who were exposed to AH of 14.5% at 12.3% O2 for 20 min. Amplitude (P1II, RII, T1II, BAL, BAR) and temporal (RR, QT) ECG parameters, and blood oxygenation (SpO2) were determined at AH periods (at 5, 10, and 20 min respectively). In subgroups (clusters), the features of types with low and high responses, and their stability in AH are described.
 RESULTS: Clustering of ECG variations with AH of 14.5% and 12.3% O2 identified two subgroups (clusters), that differed at least in the magnitude of the decrease in the total BAL and RR. With AH of 14.5% O2, the number of different ECG parameters between subgroups gradually increased: at 5 min BAL (p 0.001), at 20 min RII (p=0.047), T1II (p=0.016), BAL (p 0.001), RR (p=0.035), QT (p=0.008), and with AH 12.3% O2 only BAL (p 0.001). It was found that at all periods of AH of 14.5% O2, in 60% of individuals, the type of response remained. Regarding AH of 12.3% O2 in 55.2% of the other cases, the type of response of ECG parameters changed. At the same time, no parallels were observed between the types of reactions and deviations in SрO2.
 CONCLUSION: From this study, It can be assumed that there are two types of conjugated reactions of ECG parameters in response to mild and medium AH, and their variability is absent in 40% and 44.8% of cases, respectively, as well as the independence of differentiation of ECG responses types from hypoxemia.