Respiratory rhythm of rats under acute emotional stress

Irregularity of the rhythm of breathing, the breathing rate, blood pressure and heart rate were studied in rats under acute emotional stress induced by non-periodic stimulation of the skin and ventromedial hypothalamus. The irregularity of the rhythm of breathing was substantially increased during stimulation of the hypothalamus up to short-term respiratory arrests in animals predisposed to emotional stress. Disturbances of the rhythm of breathing may be one of objective prognostic criteria of the animals' survival or lethality under emotional stress.     

Cardiorespiratory synchronism: revealing in human,dependence on properties of nervous system and functional states of an organism

Cardiorespiratory synchronism (CRS) shows that at the breathing frequency, which as usual exceeds the baseline heart rhythm, the heart makes one contraction per each breathing. It is shown that CRS arises as a result of reproduction by the heart the rhythm of signals, coming to the heart via vagus nerves. CRS characterized by the synchronization range, duration of its development after the beginning of the rapid respiration, difference between the baseline heartbeat frequency and lower limit of synchronization range. The CRS parameters were determined in humans at the age of 5-65. The CRS parameters depends on nervous system type, vegetative tonus of the nervous system and functional states of an organism.     

Features of cardio-respiratory synchronization phenomenon in children with different types of the nervous system

Human breathing and cardiac rhythms become synchronized during voluntary respiration of a subject with the rate higher than the initial cardiac rate. This phenomenon is observed during driving of the breathing rhythm with rhythmical flashes of a photostimulator lamp. The broadest bandwidth of the range of cardiorespiratory synchronization was observed in phlegmatic children, and the narrowest bandwidth was observed in choleric children. The dependence of characteristics of combined heart and breathing rhythmogenesis on temperamental types is determined by the properties of the nervous system, i.e., force, balance, and flexibility.     

存在睡眠呼吸异常的慢病患者呼吸影响心率变异性的初步分析*

目的: 基于整体整合生理学医学理论提出的呼吸引起循环指标变异的假说,分析研究存在睡眠呼吸异常的慢病患者睡眠期间呼吸和心率变异之间的相关关系。方法: 纳入存在睡眠呼吸异常且呼吸暂停低通气指数（AHI）≥15次/小时的慢病患者11例,签署知情同意书后完成标准化症状限制性极限运动的心肺运动试验（CPET）和睡眠呼吸监测,计算分析病人睡眠期间波浪式呼吸（OB）期与正常平稳呼吸期的呼吸鼻气流、心电图R-R间期心率变异的规律。结果: 存在睡眠呼吸异常的慢病患者CPET峰值摄氧量（Peak VO₂）和无氧阈（AT）为（70.8±13.6）%pred和（71.2±6.1）%pred;CPET有5例存在运动诱发的波浪式呼吸（EIOB）,6例为呼吸不稳定,提示整体功能状态低于正常人。本组慢病患者AHI为每小时（28.8±10.0）次,睡眠呼吸异常总时间占睡眠总时间的比值为（0.38±0.25）;OB周期的平均时间长度为（51.1±14.4）s。本组慢病患者正常平稳呼吸期的呼吸周期数与心率变异周期数的比值（B-n/HRV-B-n）为1.00±0.04,每个呼吸周期节律的心率变异平均幅度（HRV-B-M）为（2.64±1.59） bpm,虽然低于正常人（P<0.05）,但却与无睡眠呼吸异常的慢病患者相似（P>0.05）;HRV-B-M的变异度CV（HRV-B-M的SD/x）为( 0.33±0.11）,期间血氧饱和度（SpO₂）虽略低,但并无明显规律性下降与上升。本组慢病患者的OB期间呼吸周期数与心率变异周期数（OB-B-n/OB-HRV-B-n）比值为（1.22±0.18）,OB期每个呼吸周期节律的心率变异平均幅度（OB-HRV-B-M）为（3.56±1.57）bpm及其变异度（OB-CV =OB-HRV-B-M的SD/x）为（0.59±0.28）,每个OB周期节律的心率变异平均幅度（OB-HRV-OB-M）为（13.75±4.25）bpm,OB期间低通气时SpO₂出现明显的下降,OB期间SpO₂平均变异幅度（OB-SpO₂-OB-M）为（4.79±1.39）%,OB期的OB-B-n/OB-HRV-B-n比值、OB-HRV-OB-M比其正常平稳呼吸期对应指标显著增大（P<0.01）。OB-HRV-B-M虽然与正常平稳呼吸期HRV-B-M相比差异无统计学意义（P>0.05）,但其变异度OB-CV却显著增大（P<0.01）。结论: 睡眠呼吸异常的慢病患者OB期的心率变异幅度大于其正常平稳呼吸期,当呼吸模式发生改变时心率变异也发生明显改变,其平稳呼吸期的呼吸周期数与心率变异周期数的比值与正常人以及无睡眠呼吸异常的慢病患者相同,证实心率变异为呼吸源性;而其OB期间心率变异周期数相对于呼吸周期减少直接源于此时的低通气或者呼吸暂停,心率变异也是呼吸源性。     

Study of cardiac, respiratory, and motor activities in rat fetuses

Development of the cardiac, respiratory, and motor activities in rat fetuses with preserved placental circulation was studied at the 16th, 18th, and 20th gestation days. The presence of three main movement types has been found: complexes of generalized activity, local movements, and jerks. In development of respiratory function, there is observed a gradual transition from individual inspirations to series of breathing movements and then to formation of periodic breathing episodes. At the studied period, the heart rate has been found to increase. The existence of the slow-wave modulations of the heart rate with a period of 2040 s has been revealed. Analysis of interrelations between the respiratory and motor systems has shown that in the 16-day fetuses, each breathing movement is accompanied by extensor jerk. By the 20th days of embryonic development (E20), uncoupling of the respiratory and motor activities occurs. Comparison of the activity observed in the cardiac and somatomotor systems has shown that at E16, the cardiac rhythm fluctuations do not depend on the motor excitation jerks. In the 18-day fetuses, brief slowing down (decelerations) of the cardiac rhythm appeared during the motor activity jerks, whereas at E20, on the contrary, an increase of frequency (accelerations) of the cardiac rhythm occurred.     

Nonstationary Heart Rate Variability in Respiratory Tests

A new method was proposed for processing a nonstationary heart rate by using frequency-modulated signals rather than amplitude-modulated signals equally spaced over several points of time as in the conventional method. A frequency-modulated signal is a set of identical Gaussian peaks that coincide with the true time points of heart beats. A continuous wavelet transform was used to quantitatively describe the heart rhythm signal. A test with controlled breathing was performed as an example and included three consecutive stages: rest, rhythmic breathing at a specified frequency, and exhalation. Tachograms recorded during the breath test was found to be a nonstationary signal with the alternation of peaks of different spectral ranges. A system of quantitative parameters was developed to describe the dynamics of changes in the spectral properties of the tachogram in transitional areas. A static clustering by the effect of the respiratory test and a dynamic clustering in order to identify the time points when the autonomic nervous system is stressed were performed for all subjects. The article discusses the prospects of using the method as a means to analyze the transient effects in various functional tests and as biofeedback that would help to change the heart rhythm.     

Heart rate variability in subjects with different respiratory rates

The variability of the cardiac rhythm was studied in males with different initial respiratory rates. At rest and during voluntarily controlled breathing, subjects with medium respiratory rates were found to have a less variable heart rate than their counterparts with low or high respiratory rates.     

Cardiorespiratory interactions to external stimuli

Respiration is a powerful modulator of heart rate variability, and of baro- or chemo-reflex sensitivity. This occurs via a mechanical effect of breathing that synchronizes all cardiovascular variables at the respiratory rhythm, particularly when this occurs at a particular slow rate coincident with the Mayer waves in arterial pressure (approximately 6 cycles/min). Recitation of the rosary prayer (or of most mantras), induces a marked enhancement of these slow rhythms, whereas random verbalization or random breathing does not. This phenomenon in turn increases baroreflex sensitivity and reduces chemoreflex sensitivity, leading to increases in parasympathetic and reductions in sympathetic activity. The opposite can be seen during either verbalization or mental stress tests. Qualitatively similar effects can be obtained even by passive listening to more or less rhythmic auditory stimuli, such as music, and the speed of the rhythm (rather than the style) appears to be one of the main determinants of the cardiovascular and respiratory responses. These findings have clinical relevance. Appropriate modulation of breathing, can improve/restore autonomic control of cardiovascular and respiratory systems in relevant diseases such as hypertension and heart failure, and might therefore help improving exercise tolerance, quality of life, and ultimately, survival.     

Correlation of atrial and ventricular contractility. The possibility of using the atria for controlling the artificial heart]

A possibility of the artificial ventricle regulation using information on the atrial contraction is discussed. Correlations between atrial wall tension and ventricle tension as well as the pressure under radom heart rhythm variations were studied. The wall tension of the appropriate heart portion was recorded by the arched tensiometers, and intraventricular pressure under cavity catheterization by the electric manometer. The cardiac rhythm varied between 2.0 c-1 and 4.0 c-1. A correlation between the tension and interpulse interval, (correlation coefficient being 0.62 +/- 0.05) was established. The close relationships "atrial wall tension-intramuscular pressure" were observed. For such relationships the correlation coefficient changed from 0.713 +/- 0,09 to 0,874 +/- 0.02 depending on the average value of interpulse interval. It is concluded that the information on the atrial contraction can be used for artificial heart regulation.     

Changes in cardiac rhythm in humans during breathing compressed air under pressure up to 1.1 MPa (results of the rhythmo-cardiographic study)]

Dynamics of cardiac rhythm has been considered according to rhythmocardiographic characteristics of heart rate under orthostatic test and one-stage step-test in four altitude chamber experiments where air under pressure of 0.4-1.1 MPa is used as a breathing mixture. It is shown that these characteristics linearly depend on the partial nitrogen and oxygen pressure and hyperbaric bradycardia essentially decreases in the final period of isopression due to toxic oxygen effect. Cytochrome C decreases hyperbaric bradycardia. Under hyperbaric conditions the regulation of cardiac rhythm proceeds with altered central vegetative effects provided a direct effect of higher nitrogen and oxygen pressure on the sinusal node cells.     

Assimilation of rhythm by the isolated dog heart during gradual raising of stimulation frequency

An ability for a forestalling regulation of contractility of the heart with calculation of the tendency of rhythm increasing was revealed under a gradual increasing of heart rhythm. A forestalling regulation of heart contractility occurs with rhythm assimilation at the cell level of the heart and irrespective of the influence of Frank-Starling law and neurohumoral factors on the work of the heart. A 5-10% increasing of heart rhythm is characterized by optimal rhythm assimilation. A 15-40% increasing of heart rhythm is not optimal and results in transformation of the rhythm. The following sequence of events take place in the process of transition from rhythm assimilation to rhythm transformation under a gradual increasing of heart rhythm: rhythm assimilation--rhythm by mechanical function--incomplete rhythm assimilation by electrical function-transformation of rhythm by electrical function.     

窦性节律下家兔心率与在位心室肌纤维有效不应期的关系

在自然呼吸和窦性节律下,用浮置式玻璃微电极引导在体单个左心室肌纤维动作电位,作为兴奋的指标,以其 0相触发产生期前的试验刺激,测定有效不应期(ERP)。38只家兔的测定结果表明,在R-R间期为205—330ms的范围内,随着心率加快(R-R间期缩短),ERP减小,而 ERP/RR 间期增大,说明 ERP 与心率直接有关。并且,在较快的心率时,ERP 相对延长。通过相关与回归分析,制出了能够删除心率影响的校正公式。静脉注射酒石酸锑钾(50mg/kg)发现,在窦性和起搏节律下,酒石酸锑钾均能轻度延长 ERP(P<0.001)。窦性节律下的校正后值与起搏节律的测定结果完全一致。证明校正后值能够用来比较处理前后不同心率条件下,各种药物、离子及其它因素对ERP 的影响。 本文的校正公式虽然只适用于同种动物和方法,但此校正公式的制作原理也可以广泛应用到其它多种动物。     

Long-term measurement of heart rate in chicken eggs

Taking advantage of acoustocardiogram (ACG), we measured the heart rate (HR) of chick embryos continuously from day 12 until hatching and then investigated the development of HR irregularities (HRI), HR variability (HRV), and the existence of a circadian rhythm in mean HR (MHR). HRI comprised transient bradycardia and tachycardia, which first developed on day 14 and 16 in most embryos, respectively. Transient bradycardia increased in frequency and magnitude with embryonic development and occurred over periods of up to 30 min in some embryos. MHR was maximal on around days 14-15 and thereafter decreased to about 250-260 bpm on days 16-18. Baseline HRV, which is an oscillation of the MHR baseline, occurred as HR decreased from days 15-16 and became predominant on days 17-18. The magnitude of the baseline oscillations reached up to 50 bpm in some embryos and the period ranged between about 40-90 min (ultradian rhythm). A circadian rhythm of MHR was not found in late chick embryos. On days 18-19, embryonic activities were augmented and then breathing movements began to occur, disturbing ACG signals and thus making it difficult to measure the HR. Instead, the development of breathing activities was recorded. Breathing frequency was irregular at first and then increased to a maximum of about 1.5 Hz prior to hatching.     

Phase-dependence of breathing and finger tracking movements during normocapnia and hypercapnia

The coordination between breathing and other motor activities usually implies that the respiratory rhythm has become entrained by the rhythm of the simultaneous movement. Our hypothesis was that by increasing the respiratory drive, e.g. by hypercapnia, we would be able to reduce the subordination of breathing to other movements and, on the other hand, enhance effects of breathing on those movements. We investigated interactions between breathing and finger flexion movements in a visually controlled step-tracking procedure which allowed us to distinguish the mutual effects and to detect the dependence of these effects on the phase-relationship between breathing and movement. In contrast to our hypothesis, we found no large increase of the respiratory influences on finger movements during hypercapnia. A noteworthy difference to normocapnia was a shortening of the finger flexion time during the final stage of expiration which was associated with an increased frequency of coincidence between the end of flexion time and the transition from expiration to inspiration. On the other hand, the response of breathing to the finger movement increased when the tracking signal was presented at the beginning of inspiration. The results of the study disproved our hypothesis and demonstrated that, during hypercapnia, breathing can be even more susceptible to influences originating from motor control. Thus, they are in agreement with the findings of a previous study that the coordination between breathing and rhythmic limb movements becomes closer during hypercapnia.     

Cardiac rhythms in developing emu hatchlings

Six emu hatchlings were non-invasively measured for electrocardiogram (ECG) from their chest wall using flexible electrodes, and the instantaneous heart rate (IHR) was determined from ECG throughout the first week of post-hatching life. Although the baseline heart rate (HR) was low, approximately 100-200 beats per min (bpm), compared with chick hatchlings, the IHR fluctuated markedly. The fluctuation of IHR comprised HR variability and irregularities that were designated as types I, II and III in chick hatchlings and additional large accelerations distinctive of emu hatchlings. Type I was HR oscillation with a mean frequency of 0.37 Hz (range 0.2-0.7 Hz), i.e. respiratory sinus arrhythmia (RSA). From RSA, breathing frequency in emu hatchlings was estimated to be approximately half of that in chickens. Type II HR oscillation was also found in the emu; the frequency ranged from approximately 0.04 to 0.1 with a mean of 0.06 Hz, and the magnitude tended to be large compared with that of chickens. In addition to type III HRI, which was designated in chickens, large, irregular HR accelerations were characteristic of emu hatchlings. From IHR data, developmental patterns of mean heart rate (MHR) were constructed and plotted on a single graph to inspect the diurnal rhythm of MHR by visual inspection and power spectrum analysis. A circadian rhythm was not clear in the emu hatchlings, in contrast to chick hatchlings, which showed a dominant diurnal rhythm.     

Respiratory modulation of the autonomic nervous system during Cheyne-Stokes respiration

Cheyne-Stokes respiration (CSR) is associated with increased mortality among patients with heart failure. However, the specific link between CSR and mortality remains unclear. One possibility is that CSR results in excitation of the sympathetic nervous system. This review relates evidence that CSR exerts acute effects on the autonomic nervous system during sleep, and thereby influences a number of cardiovascular phenomena, including heart rate, blood pressure, atrioventricular conduction, and ventricular ectopy. In patients in sinus rhythm, heart rate and blood pressure oscillate during CSR in association with respiratory oscillations, such that both peak heart rate and blood pressure occur during the hyperpneic phase. Inhalation of CO2 abolishes both CSR and the associated oscillations in heart rate and blood pressure. In contrast, O2 inhalation sufficient to eliminate hypoxic dips has no significant effect on CSR, heart rate, or blood pressure. In patients with atrial fibrillation, ventricular rate oscillates in association with CSR despite the absence of within-breath respiratory arrhythmia. The comparison of RR intervals between the apneic and hyperpneic phases of CSR indicates that this breathing disorder exerts its effect on ventricular rate by inducing cyclical changes in atrioventricular node conduction properties. In patients with frequent ventricular premature beats (VPBs), VPBs occur more frequently during the hyperpneic phase than the apneic phase of CSR. VPB frequency is also higher during periods of CSR than during periods of regular breathing, with or without correction of hypoxia. In summary, CSR exerts multiple effects on the cardiovascular system that are likely manifestations of respiratory modulation of autonomic activity. It is speculated that the rhythmic oscillations in autonomic tone brought about by CSR may ultimately contribute to the sympatho-excitation and increased mortality long observed in patients with heart failure and CSR.     

Spectral analysis on fluctuation of heat period in paralyzed,vagotomized, and unanesthetized decerebrate cats

Spectral analysis was performed on the heart period fluctuation in vagotomized, paralyzed, and unanesthetized decerebrate cats. The heart period was measured as the time interval between successive R waves of the electrocardiograms. When end-tidal P _{CO 2} was set at the same level as that before immobilization, the power spectral density plot of the heart period fluctuation showed several distinct peaks: one peak corresponded to the frequency of the artificial ventilator and the others to its harmonics. In addition, the spectral density plot had another peak centered at the intrinsic respiratory frequency evaluated by recording efferent phrenic neural discharges. The amplitude of these spectral peaks tended to become greater when the end-tidal P _{CO 2}was increased by adding CO₂ to the input gas. Our results, therefore, provide evidence that the heart period is modulated not only by the artificial ventilation rhythm but also by the centrally generated respiratory rhythm, and suggested that the strength of such central interactions between cardiac and respiratory rhythms varies depending on the end-tidal P _{CO 2} level.     

Voluntary and Involuntary Control of Breathing with Imposed Ventilation Parameters

To clarify the mechanisms of interaction between voluntary and involuntary control of respiratory movements in a waking human, respiratory patterns were studied during self-controlled artificial ventilation used in place of natural breathing. Seven subjects controlled both the duration of artificial inhalations and the flow rate of air at excess pressure, continuously adjusting their actions to obtain the sensation of comfortable breathing. At rest, pulmonary ventilation was higher during self-controlled artificial breathing than during natural breathing. This trend was also noted during exercise. A correlation was observed between the velocity of the movement that started air flow and the artificial ventilation volume (r = 0.91). During self-controlled artificial breathing, the subjects sometimes took natural breaths. Natural inhalations did not influence the beginning or end of an artificial inhalation. Information received from respiratory receptors was assumed to play a certain role in the self-control of artificial breathing.     

Changes in heart rate during breathing interrupted by recurrent apneas in humans

Heart rate varies with breathing patterns, especially in sleep apnea. To assess the effects on heart rate of recurrent apneas interrupting tidal breathing, we studied five normal awake male subjects. These subjects voluntarily changed their breathing pattern from regular tidal breathing to tidal breathing interrupted by breath holding at end expiration. This recurrent apneic breathing pattern did not change mean heart rate but increased its variance significantly. In addition, the variations in heart rate formed a cyclic pattern of oscillation with a mean cycle length identical to both arterial O2 saturation (SaO2) (R = 0.95; P less than 0.01) and ventilation (R = 0.92; P less than 0.01). Cyclic changes in either SaO2 or ventilation reproduced the oscillatory patterns of heart rate seen with tidal breathing interrupted by multiple apneas, but the amplitude of the variance in heart rate was smaller. Finally, preventing the cyclic declines in SaO2 with supplemental O2 did not significantly alter the heart rate changes seen in tidal breathing interrupted by apneas.     

Study of circadian activity in the crayfish <Emphasis Type="Italic">Pontastacus Leptodactylus</Emphasis> during their multimonth maintenance in the river water flow

By the method of non-invasive on-line recording and processing of photoplethysmograms of testaceous invertebrates, the circadian rhythm of cardioactivity was studied in crayfish Pontastacus leptodactylus by recording for several month of the heart rate (HR) and stress-index (characteristics of variational pulsometry). The crayfish were kept in the natural running water in regime of the natural illumination alternation (the first group) or at constant artificial illumination of low intensity (the second group). The circadian rhythm was more frequent and more pronounced in crayfish of the first group. The criteria were established to determine the appearance and stabilization of the nocturnal, active rhythm phase: an increase of HR by more than 30% as compared with the daytime rest period and duration of such increase for at least 2.5 h. The stress-index has been shown to be a reliable parameter of the beginning of the nocturnal phase of cardioactivity, while preservation of the typical circadian rhythm can be considered as a bioindicator in the biomonitoring systems of the quality of surface waters.