Rapid exposure at high altitude is likely to cause Acute Mountain Sickness (AMS) of different levels. This paper designs a "quick acclimatization" method to make the volunteers adapt to 3,600 meters (m) after 2-day training and 3,900 m after 3-day training. Especially, we investigate the effects of mindful breathing on rapid hypoxia preacclimatization training. 8 young male volunteers were randomly divided into one treatment group and one control group. Peripheral Saturation of Oxygen (SpO2), Heart Rate (HR) and Respiratory Rate (RR) were recorded from the beginning to the end. We find that: (1) Hypoxic Preacclimatization Training Scheme (HPTS): at 3600 m, the increment of SpO2 was 3.18% after 2-day training (P < 0.01); at 3900 m, 8 volunteers got obviously higher SpO2 (2.65%, P < 0.05) and lower HR (–5.31 bpm, P < 0.05) after 3-day training. (2) Mindful Breathing Training Scheme (MBTS): at 3,600 m, the treatment group obtained better SpO2 level (2.21%) with obviously lower HR (–7.1 bpm) and unobvious higher RR (2.85 br/min) than control group after 2-day training; at 3900 m, the treatment group did not show a significant difference after 3-day training. Besides, the treatment group exhibited a comprehensive better performance over the control group at night, which obtained a higher SpO2 with lower HR and lower RR. In the comparison of different altitudes, the two groups had similar RR while the treatment group had a higher SpO2 (P < 0.05) and a lower HR (P < 0.001). In the dynamic comparison during mindful breathing training, SpO2 occurred remarkable differences: P < 0.05 every 15 minutes started from the 45th minute. We conclude that HPTS successfully helped volunteers adapt to the setting altitude in a short time. MBTS can induce significant phenomenon of sustained gain effect. It can effectively increase the acclimatization speed to quickly return to lower HR and RR and obtain higher SpO2. MBTS can enable beginners without any experience of mindfulness and breathing training to initially stimulate the trend of "energy-saving" acclimatization in 2–3 days.

Obstructive sleep apnea (OSA) is regarded as one of the most common sleep-related breathing disorders, which causes various diseases and affects people's daily life severely. Up to now, massive efforts have been devoted to identifying OSA events during sleep based on different signals (e.g., PSG, ECG, nasal airflow and EMG, etc.). However, there still are more or less shortcomings in current studies. In this paper, we propose a novel framework to improve the performance of identifying OSA events. Particularly, the key idea of our framework is to divide each potential event segment (i.e., a data segment that may or may not contain an OSA event) into different phases, from which we further extract fine-grained features to characterize respiratory pattern comprehensively. Concretely, we first automatically locate potential event segments from raw ballistocardiography (BCG) data by identifying arousals. Afterwards, each potential event segment is divided into three phases (i.e., Apnea Phase, Respiratory Effort Phase and Arousal Phase) by an adaptive threshold-based division algorithm. Based on these phases, we further extract and select efficient features that can characterize respiratory pattern from different aspects. Finally, these potential event segments are classified into OSA events or non-OSA events using BP neural network. Experimental results based on a real BCG dataset that contains 3,790 OSA events and 2,556 non-OSA events show that our framework outperforms the baselines and the precision, recall and AUC reach 94.6%, 93.1%, and 0.951, respectively.

This study aimed to employ the recently developed fuzzy measure entropy (FuzzyMEn) method to compare the difference in heart rate variability (HRV) between rest and exercise states in hypoxic environment. Four healthy male volunteers were enrolled in this study. For each subject, electrocardiography (ECG) and finger pulse were recorded in ten days to obtain the heart rate (HR) time series. For each day, the measurement lasted 150 min and was divided into six consecutive experimental sections: 3 repeat rest sections (each 30 min) and 3 repeat exercise sections (each 20 min). The repeat rest and repeat exercise sections were in turn. In each rest or exercise section, the segment of HR time series from the second 5 min episode (from the 6th min to the 10th min) was selected for the FuzzyMEn calculation. The effects of subject, day, repeat measurement and state (rest or exercise) on the FuzzyMEn were investigated. The mean FuzzyMEn differences among ten days and between rest and exercise states were also analyzed. Results showed that day and state factors have significant effects on FuzzyMEn (both P

We designed two types of pre-adaption plans for this study. One was a pre-adaption training with progressive intermittent hypoxia, with a constant lower pressure oxygen tank used in the plain before arriving at the plateau (PG). The other was by progressively increasing the time of exposure to hypoxia with oxygen supplied in stages after radical plateau (RG). By testing the blood oxygen saturation (SpO2), heart rate (HR), and quality of sleep after arriving at the 3800 m high plateau, results showed that the pre-acclimatization and radical groups performed better than the control group (CG). Both strategies were equivalent in terms of effects and principles in providing more flexible choices for acclimatization.

Acute hypoxia activates several autonomic mechanisms, mainly in cardiovascular system and respiratory system. The influence of acute hypoxia on linear and nonlinear heart rate variability (HRV) has been studied, but the parameters in the process of hypoxia are still unclear. Although the changes of HRV in frequency domain are related to autonomic responses, how nonlinear dynamics change with the decrease of ambient atmospheric pressure is unknown either. Eight healthy male subjects were exposed to simulated altitude from sea level to 3600 m in 10 min. HRV parameters in frequency domain were analyzed by wavelet packet transform (Daubechies 4, 4 level) followed by Hilbert transform to assess the spectral power of modified low frequency (0.0625–0.1875 Hz, LFmod), modified high frequency (0.1875–0.4375 Hz, HFmod), and the LFmod/HFmod ratio in every 1 min. Nonlinear parameters were also quantified by sample entropy (SampEn) and short term fractal correlation exponent (α1) in the process. Hypoxia was associated with the depression of both LFmod and HFmod component. They were significantly lower than that at sea level at 3600 m and 2880 m respectively (both p < 0.05). The LFmod/HFmod ratio was acutely increased at 3600 m (p < 0.05). SampEn was significantly declined at 2880 m (p < 0.05). Although the value of α1 was close to 1, it changed not significantly in the whole process. These results indicated hypoxia gradually attenuated both spectral HRV parameters and SampEn. The balance of sympathovagal shifted towards sympathetic dominance at a certain altitude. Monitoring linear and nonlinear HRV parameters continuously in the process of hypoxia would be an effective way to evaluate the different regulatory mechanisms of autonomic nervous system.

Currently, a number of people have various sleep disorders, and sleep stages play an important role in assessment of sleep quality and health status. This paper proposes an effective approach of analyzing the sleep stages based on ballistocardiography (BCG), which can be continuously detected with micro-movement sensitive mattress (MSM) in this work, during non-intrusive sleep in home environment. This paper focuses on extracting features from BCG from the following three aspects: multi-resolution wavelet analysis of the heartbeat intervals based time-domain features, Welch’s power spectrum estimation based frequency-domain features and the detrended fluctuation analysis (DFA) value for long term correlation based features. Moreover, the support vector machine (SVM) with or without the factor of sleep rhythm, and recurrent neural network (RNN) are adopted to build the classifiers, and both the personal model and self-independent model are investigated for different scenarios. Experimental result of 56 subjects [25 women and 31 men, aged from 16 to 71] was evaluated applying the proposed method and compared to the result provided by professional visual scoring by ECG and EEG. The SVM with the factor of sleep rhythm shows better performance with an average accuracy between 73.21

This study was aimed to assess the responses of cardiac autonomic nerve during the simulated altitude ascending from sea level to 3000m in 10 minutes, and then returning to sea level using the same time. R-R interval (RRI) series were analyzed continuously by wavelet packet transform followed by Hilbert transform to assess the amplitudes of modified total (TPmod: 0-0.4375 Hz), low (LFmod: 0.0625-0.1875 Hz) and high (HFmod: 0.1875-0.4375 Hz) frequency component, as well as the ratio of LFmod/ HFmod in every one minute. The results suggested that the autonomic heart rate control was gradually attenuated in the process of ascent, and was progressively enhanced during descent. The balance of sym-pathovagal shifted to sympathetic dominance during the study. Monitoring cardiac autonomic nervous responses in the process of ascent and descent would be an effective way to evaluate the regulatory mechanism for acclimatization to hypoxia.

Objective This study aimed to understand the continuous physiological parameters during sleep under the guidance of Chinese medical theory and clinical practice and to establish the method to diagnose the physical and mental status by analyzing nocturnal sleep data.Methods More than 2000 subjects were recruited in the nocturnal sleep examination using the micro-movement sensitive mattress sleep monitoring system.Based on the analysis of the sleep indices and nocturnal physiological parameters combined with clinical data,a hypothesis was put forward that sleep cycle could reflect the circulation status of qi and blood,as well as some preliminary exploration on revealing the status of qi,blood,yin and yang.Results Sleep structure could reflect the status of qi and blood circulation in different meridians according to the traditional Chinese time unit.Sleep structure and sleep cycle could show corresponding changes if there is morbidity in some meridian,zang-viscera and fu-viscera.Heart rate,respiration rate and other physiological parameters could reflect the alternative predominance of yin and yang.Conclusion Interpreting the physiological parameters during sleep could be a supplementary diagnosis method for Chinese medicine syndrome differentiation.

Contrary to the problem of plateau acute reaction caused by the low oxygen partial pressure, we designed a simulated altitude environment atmospheric hypoxia chamber. The control system is based on fuzzy adaptive algorithm combined with expert algorithm and PD algorithm, which can justify parameter itself to fit the environment of time-delay and instability. During 10 days of hypoxic training, the simulating altitude inside the chamber is controlled within expected limits, which is able to recover after an interfere is occurred. This system solves the problem of controlling difficulty due to the complex environment of the chamber, and provides strong robustness as well as high accuracy, which provides a scientific platform for the related research of hypoxia.