Power spectrum analysis of heart rate fluctuations and respiratory movements associated with cooling the human skin

Kokedama and essential oils had a relaxing psychophysiological effect on Taiwanese women during the COVID-19 pandemic

BACKGROUND

During the COVID-19 pandemic, we designed an indoor nature activity program for citizens with a relaxing effect similar to forest bathing to promote their physical and mental health. We integrated an indoor horticultural activity (Kokedama) with the breathing of Pseudotsuga menziesii (P. menziesii) and Lavandula angustifolia (L. angustifolia) essential oils (EOs) with the goal of creating a nature-inspired environment in an indoor setting where participants would feel as if immersed in a forest atmosphere.

METHODS

Taiwanese women participated in the experiment, using two Saturday mornings, one Saturday in a university classroom in the city center; and the other Saturday in a workshop in a Suburban Park. Intra-group comparisons were used to assess the Physiological responses to urban and suburban environmental stimuli and measured self-reported psychological responses. We recorded parameters associated with heart-rate variability and brainwaves. We also administered the State-Trait Anxiety Inventory-State (STAI-S) questionnaire before and after the participants had completed the entire program.

RESULTS

After the participants had breathed the P. menziesii and L. angustifolia EOs, the levels of some physiological parameters increased (standard deviation of normal-to-normal intervals, normalized high frequency, and high alpha wave) and those of others decreased (normalized low frequency, low- to high-frequency ratio power, high beta wave, and gamma wave). These findings were corroborated by the data from the STAI-S questionnaires.

CONCLUSIONS

The psychophysiological data from this study provide significant scientific evidence for the health benefits of an indoor nature activity program in women.

The sympathetic-vagal balance against endotoxemia

The goal of this study was to establish a convenient and effective approach to anti-inflammation treatment by rebalancing the sympathetic-vagal system via vagal nerve stimulation (VNS). We established an endotoxemia model in Sprague-Dawley rats using lipopolysaccharide (LPS) injection. Electrical discharges in the vagal system, including the nucleus tractus solitarii (NTS) and afferent and efferent cervical vagal nerves, were detected. The condition of sympathetic-vagal balance, presented as heart rate variability (HRV) and hepatic norepinephrine/acetylcholine (NE/ACh), was measured following endotoxemia with and without VNS. Discharges in afferent and efferent vagal nerves increased significantly following LPS injection compared with the basis level and corresponding time points in the control group. Discharges in the NTS also increased significantly following LPS injection. The HRV components, including normalized high frequency (HFnm), normalized low frequency (LFnm), LF/HF, and very low frequency (VLF), increased significantly following LPS injection. HFnm values in the LPS + VNS group increased significantly compared with the LPS group. Conversely, LFnm, LF/HF, and VLF in the LPS + VNS group decreased significantly compared with the LPS group. Hepatic NE and ACh significantly decreased within 6 h after LPS injection compared with the basal level and the control groups (P < 0.05). VNS did not significantly improve hepatic NE, but the ACh levels in the LPS + VNS group were higher than those in other groups. Sympathetic and vagal nervous systems are enhanced following endotoxemia. The overexcitation of the sympathetic system leads to sympathetic-vagal disequilibrium. The rebalance of the sympathetic and vagal system is crucial for critically ill patients.

Effects of low ambient temperature on heart rate variability during sleep in humans

The effects of cold exposure on heart rate variability (HRV) during sleep were examined. Eight male subjects slept under three different conditions: 3 degrees C, 50-80% relative humidity (RH) [3]; 10 degrees C, 50% RH [10]; and 17 degrees C 50% RH [17]. No significant differences were observed in HRV during rapid eye movement sleep (REM) and wakefulness. The ratio of the low frequency (LF) to high frequency component (HF) of HRV (LF/HF) significantly differed among the conditions during stage 2 and slow wave sleep (SWS) that decreased as the ambient temperature decreased. The normalized LF [LF/(LF + HF)] significantly decreased in 3 and 10 than in 17 during SWS. In low ambient temperature, predominant cardiac parasympathetic activity during stage 2 with no significant difference during REM and wakefulness may cause variations in HRV at transition from stage 2 to REM and wakefulness. These results may partly explain the peak in adverse cardiac events during winter.

Diameter variations of retinal blood vessels during and after treatment with hyperbaric oxygen

AIMS

To quantify retinal vascular change during and after hyperbaric oxygenation (HO) for 6x5 weekly 90 minute treatments.

METHODS

Fundus photographs were taken before, during, and after HO at 2.5 atmospheres absolute pressure (ATA) on days 1, 2, 3, 10, 20, 29, and 30 of treatment on three patients using a specially developed hand held ophthalmoscope with a digital colour camera. Blood vessel diameter was estimated on red free retinal images. The mean of three measurements of arterioles and venoles close to the optic disc was calculated. Consistency and repeatability of the method was verified by estimating the diameter of the vessels by three measurements in each of seven images taken within 70 seconds on the same person. Analysis of variance with Bonferroni correction for multiple comparisons was conducted to ascertain whether significant intergroup differences existed.

RESULTS

Breathing 100% oxygen at 2.5 ATA constricts retinal arterioles by 9.6% (standard deviation 0.3%) and venoles by 20.6% (SD 0.3%) of their size in air at ambient pressure. Constriction escalates during treatment. Ten minutes after the HO, arterioles dilate to 94.5% (SD 0.3%) and venoles to 89.0% (SD 0.3%) of their primary size. This pattern is the same for each day of measurement. Heart frequency falls continually during HO. Systolic, diastolic, and mean arterial pressures stay constant.

CONCLUSION

Exposure to hyperbaric oxygen causes constriction of the retinal vessels. It is found that this constriction is constant through the series of treatments. This suggests that oxygen or products thereof are responsible for the vascular changes during and after hyperbaric oxygenation probably through autoregulation of the retinal vessels.

Heart rate variability in healthy volunteers during normobaric and hyperbaric hyperoxia

Inhaled supranormal partial pressure of oxygen induces bradycardia and peripheral vasoconstriction. The exact mechanism of the decreasing heart rate is not clear, but the autonomic nervous system is partly involved. In the present study the role of the autonomic nervous system in hyperoxic bradycardia was evaluated by using the power spectral analysis of heart rate variability. Ten healthy volunteers participated in four experiments: (i) hyperbaric oxygen treatment (100% oxygen at 2.5 ATA), (ii) hyperbaric air treatment (O2 21% at 2.5 ATA), (iii) oxygen treatment at normal pressure (100% O2, 1 ATA) and (iv) air breathing at normal pressure (21% O2, 1 ATA). During the experiments, ECG was registered and subjected to power spectral analysis. The volunteers rated their perception of temperature, ear discomfort, sweating and excitement on a visual analogue scale. Statistical comparison of the results of the four trials was conducted with a two-way ANOVA for repeated measurements. Heart rate decreased during all interventions, but there were no statistically significant differences between the sessions. High frequency variability of heart rate variability and Hayano's index of HF power increased and LF/HF ratio decreased with increasing partial pressure of oxygen. Our results suggest, that normobaric and hyperbaric hyperoxia increase parasympathetic influence in the regulation of the heart.

Cold face test demonstrates parasympathetic cardiac dysfunction in familial dysautonomia

In familial dysautonomia (FD), i.e., Riley-Day syndrome, parasympathetic dysfunction has not been sufficiently evaluated. The cold face test is a noninvasive method of activating trigeminal brain stem cardiovagal and sympathetic pathways and can be performed in patients with limited cooperation. We performed cold face tests in 11 FD patients and 15 controls. For 60 s, cold compresses (0-1 degrees C) were applied to the cheeks and forehead while we monitored heart rate, respiration, beat-to-beat radial artery blood pressure, and laser-Doppler skin blood flow at the first toe pulp. From these measurements heart rate variability parameters were calculated: root mean square of successive differences (RMSSD), coefficient of variation (CV), low- and high-frequency (LF and HF, respectively) power spectra of the electrocardiogram, and the LF transfer function gain between blood pressure and heart rate. All patients perceived cold stimulation and acknowledged discomfort. In controls, heart rate and skin blood flow decreased significantly during cold face test; in patients, both parameters decreased only briefly and not significantly. In controls, blood pressure, RMSSD, CV, and heart rate HF-power spectra increased but remained unchanged in patients. Respiration, as well as heart rate LF power spectra, did not change in either group. In controls, LF transfer function gain between blood pressure and heart rate indicated that bradycardia was not secondary to blood pressure increase. We conclude that the cold face test demonstrated that patients with FD have a reduced cardiac parasympathetic response, which implies efferent parasympathetic dysfunction.

Alterations of fibrinolytic activity in human during and after hyperbaric oxygen exposure

To clarify the stage of fibrinolytic activation by hyperbaric oxygen (HBO) exposure, we examined its alterations in human during and after the HBO exposure. Eight healthy female volunteers breathed oxygen at 284 kPa (2.8 atmospheres absolute). Blood samples were collected before compression, shortly after compression to the pressure 284 kPa, shortly before the start of decompression, shortly after decompression, and then again 3 hours after decompression. We estimated the euglobulin fibrinolytic activity (EFA) and, the activities and antigens of both tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1). The PAI-1 activity and PAI-1 antigen showed significant decrease after compression to a pressure 284 kPa, before the start of decompression, and after decompression. The EFA level and t-PA activity rose significantly shortly after decompression, and 3 hours later returned on baseline. These findings suggest that fibrinolytic activity is elicited after HBO rather than during HBO.

Assessment of autonomic neurotoxicity in occupational and environmental health as determined by ECG R-R interval variability: a review

Measurement of heart rate variability (coefficient of variation of ECG R-R intervals, CVRR) provides a useful approach for the objective assessment of the autonomic nervous function. It is noninvasive and clinically practical, although it tends to be distorted by confounding factors such as age, alcohol, and tobacco. Specifically, two component coefficients of variation of the respiratory sinus arrhythmia (RSA) and Mayer wave-related sinus arrhythmia (MWSA) in the CVRR (i.e., C-CVRSA and C-CVMWSA), computed from component spectral powers by autoregressive spectral and component analyses, are expected to reflect parasympathetic and sympathetic functions, respectively. This article is intended to present an overview of research, utilizing the CVRR method including the C-CVRSA and C-CVMWSA, in occupational and environmental health. The available literature, addressing the impact of some chemicals and work-related factors on human autonomic nervous system, indicates that parasympathetic activity appears to be more vulnerable to these factors than does sympathetic activity. Since decreased cardiac vagal tone is associated with an increased risk of sudden cardiac death or coronary artery disease, attention should be directed to further discovery of hazardous factors in the environment and work place, which are likely to affect the autonomic nervous system.

Spectral characteristics of heart period variability during cold face stress and shock avoidance in normal subjects

Spectral analysis of heart period variability was used to examine autonomic cardiac control in several tasks used in experimental and clinical assessments of autonomic nervous system function. Cardiovascular measures were recorded in healthy humans during quiet rest, reaction time shock-avoidance, cold face stress, and combined shock-avoidance/cold face stress. Shock-avoidance was characterized by sympathetic beta-adrenergic dominance, as evidenced by (1) shorter heart periods, (2) less high-frequency spectral power, (3) elevated low-frequency power, (4) increased ratios of low- to high-frequency power, and (5) a steep regression line fitted to the log-log plot of the power spectra. Cold face stress yielded (1) longer heart periods, (2) more high-frequency power, (3) decreased low-frequency spectral power, and (4) a flat regression slope, indicating vagal dominance. Quiet rest appeared as mildly vagal, with less total spectral power, and the combination task elicited a mixed vagal-sympathetic pattern. These results are discussed in the context of (1) the autonomic underpinnings of low-frequency power, (2) the autonomic effects of facial cooling, and (3) the utility of spectral analysis of heart period variability during autonomic challenge tasks for basic research and clinical application.

Exercise and diving, two conflicting stimuli influencing cardiac vagal tone in man

1. In order to increase our understanding of the central regulation of human cardiac vagal motoneurones we studied the interaction between two opposing influences on cardiac vagal tone, one related to diving and the other to exercise. 2. The heart rate response to cooling the face (0 degrees C, trigeminal cutaneous receptor stimulation, TGS) and to a brief isometric muscle contraction was studied in fourteen healthy young adults (8 males, 6 females) during controlled ventilation at supine rest. 3. Fluctuations in R-R interval were quantified by spectral analysis. In addition the absolute values of R-R intervals occurring in any one of ten arbitrary phases of a respiratory cycle were measured over thirty to sixty cycles to give a graph of the changes in R-R interval throughout a respiratory cycle. 4. TGS produced a significant decrease in heart rate (-21 +/- 2 beats min-1 in females, -19 +/- 2 beats min-1 in males; means +/- S.E.M.). In addition the autospectral plots of R-R interval variability showed that during TGS there was a significant increase both in the high frequency peak and in the low frequency peak in all subjects. These data suggested that in these experiments the bradycardia of TGS was due to an increase in cardiac vagal tone. 5. Voluntary isometric contractions at 40 and 60% of maximum (40% MVC, 60% MVC) were timed to occur early in expiration or early in inspiration. Analysis of the changes in R-R interval produced by these contractions was confined to the respiratory cycle in which they were initiated. The early onset of these changes was interpreted as showing a decrease in cardiac vagal tone. 6. The 40% MVC and 60% MVC increased heart rate significantly within one respiratory cycle with maximum effects having a mean of 9.5 +/- 3 and 11 +/- 3 beats min-1, respectively. When isometric muscle contraction was initiated during TGS the 60% MVC but not the 40% MVC was able to significantly decrease R-R interval and hence increase heart rate. 7. It is concluded that the TGS excitatory inputs and the muscle inhibitory inputs to cardiac vagal neurones do not interact by one input gating the other early in the pathway but more probably by a process of algebraic summation closer to the cardiac vagal neurone.

Cardiovascular changes during an isometric contraction combined to a cold pressor test

Fifteen normotensive male subjects (age, 27.9 +/- 1.3 years) performed isometric contractions (handgrip) at 15, 30 and 50% maximal voluntary contraction respectively for 7, 3 and 1 min. The contractions were sustained with or without a cold pressor test of the same duration (immersion of one foot in water of 5.2 +/- 0.1 degrees C). At rest, under the influence of a cold pressor test for 3 min, the heart rate increased from 74.3 +/- 2.2 to 83.3 +/- 2.1 beats min-1 (P < 0.001) in less than 10 s, and returned to the control value in 3 min; on the contrary, at the end of 3 min of cold pressor test, the systolic blood pressure was still above the control value (135.5 +/- 4.2 and 121.0 +/- 3.2 mmHg, P < 0.001). During the contractions, there was no significant difference between heart rate and systolic blood pressure values obtained with or without cold pressor test. Similarly, there was no significant change in the concentrations of plasma catecholamines. This absence of cardiovascular effect of cold pressor test associated with isometric contraction (for three relative force levels) is probably due to the increasing importance of sympathetic cardiac activation produced by the contraction with respect to that produced by the cold pressor test, the absence of supplementary changes in total peripheral resistance and a partial reciprocal inhibition of pain produced by the simultaneous performance of these two tests.