一個運作功能正常的心臟是對於生物而言是十分重要的，所以心跳週期(R-R interval)是受到生理機制的嚴謹調控。許多調控心跳週期的機制經由許多的科學研究已被證實，本論文關注的調控機制有兩種：其一為呼吸性竇性心律不整(respiratory sinus arrhythmia, RSA)，以呼吸變化調控心跳週期的生理機制，不同的呼吸方式會影響心率變異度，而在醫學報告顯示健康的心血管系統具有高強度的呼吸性竇性心律不整表現[2]；其二為壓感反射(baroreflex)，以頭部血壓變化調控心跳週期的生理機制，許多中樞神經會影響壓感反射的靈敏度，因此可作為中樞神經正常運作的依據[3]。 本論文藉由不同呼吸方式來改變呼吸竇性心律不整的強度，並且利用倒立機的角度改變造成頭部血壓的變化，進而改變壓感反射的強度。利用非線性動力學中的同步現象來觀測呼吸方式與倒立機角度改變對心跳週期的調控。同步現象表示耦合振盪系統(coupling oscillators system)中出現相位鎖定或是頻率鎖定的關係[4]。更進一步，論文著重於相位鎖定也就是相位同步(phase synchronization)，並且利用相位同步圖與相位同步程度進行分析。實驗結果顯示在固定週期呼吸與倒立機週期擺動的情況下，多數受試者的相位同步圖與相位同步程度皆出現相位同步的跡象。 最後在共同調控中發現，呼吸訊號與倒立機擺動同相位時心率變異度增加，並且兩者為反相位時心率變異度減少。是否受試者可藉由同相位的共同調控使原有的心率變異度長期性的增加，抑或是增進受試者的生理健康，將是未來研究的方向。 ;The well-functional heart is vital to creature, so R-R interval should be regulated by rigorous mechanism of physiology. Many mechanisms of R-R interval regulation have been found, and this paper further focuses on two main mechanisms of R-R interval regulation. (i)Respiratory sinus arrhythmia (RSA): It is heart rate variability in synchrony with respiration, by which the R-R interval on an electrocardiogram (ECG) is shortened during inspiration and prolonged during expiration. (ii)Beroreflex: It is one of the body′s homeostatic mechanisms that helps to maintain blood pressure at nearly constant levels. The baroreflex provides a rapid negative feedback loop in which an elevated blood pressure reflexively causes the heart rate to decrease and also causes blood pressure to decrease. Decreased blood pressure decreases baroreflex (BR) activation and causes heart rate to increase and to restore blood pressure levels. The intensity of RSA is changed by different breathing modes, and the change of the angle of the tilting bed causes changes in the blood pressure of the head, thereby changing the intensity of BR. Synchronizaiton phenomena in nonlinear dynamics are used to observe the regulation of the breathing pattern and the change of the angle of the tilting bed to the heart period. Synchronization indicates the relationship between phase-locked or frequency- locked in the coupling oscillators system [4]. Furthermore, this paper focuses on phase-locked which means phase synchronization, and analyzes phase synchronization by synchrongram and synchronization degree. The experiment results show that in the case of fixed-cycle breathing and tilting bed oscillation, most of the subjects′ synchrongram and phase synchronization degree show signs of phase synchronization. Finally, in the case of fixed-cycle breathing and tilting bed oscillation, it is found that the heart rate variability increases when the respiratory signal is in phase with the oscillation of the tilting bed, and the heart rate variability decreases when phase difference is anti-phase. Whether the subject can increase the original heart rate variability in a long-term experiment by co-regulation of the same phase, or enhance the physical health of the subject, will be the direction of future research.
