M. Y. M. Wong

The Effect of Music on Hypertensive Patients

The aim of this study is to examine if, and to what extent, daily listening to a certain type of music can help hypertensive patients lower their blood pressure (BP). Experiments were conducted at an elderly home. Thirty subjects aged 63-93 years participated in the study and were randomly assigned into either a music group (n=15) or a control group (n=15). There were no significant differences between the two groups in initial BP values, age, gender, or medication status. Subjects in the music group listened to selected music, 25 min every day for 4 weeks. BP was measured twice a week by a registered nurse with a sphygmomanometer during the 4-week study period and after the completion of the study. Four subjects dropped from the experiment due to a change of medical conditions or to personal reasons. After 4 weeks, the average decrease for the music group (n=12) in systolic BP (SBP) and diastolic BP (DBP) was 11.8 mmHg (/>=0.008) and 4.7 mmHg (/>=0.218), respectively, whereas there was no significant changes in SBP or DBP for the control group (n=14). The results suggest that listening to a certain type of music serves to reduce high SBP and therefore music therapy may be an alterative for hypertension treatment.

A novel method for the contactless and continuous measurement of arterial blood pressure on a sleeping bed

Nighttime blood pressure (BP) is found to best predict the 5-year risk of cardiovascular death in comparison to daytime BP, BP measured over a 24-hour period and clinical BP. In view of this, a novel contactless system has been developed on a sleeping bed for the cuffless and continuous estimation of BP at night. Experiments were conducted on 11 subjects to evaluate the contactless system, particularly its performance compared to a contact system. The results of this study showed that the accuracy of the contactless system to estimate BP by a cuffless approach is comparable to that of the contact system when measured at the same posture. More studies have to be conducted in order to understand the difference of the cuffless BP estimation approach when measuring at supine and sitting postures.

Comparison of median filter and discrete dyadic wavelet transform for noise cancellation in electrocardiogram

Development of noise cancellation algorithm is essential to facilitate accurate detection of electrocardiogram (ECG) in mobile health and wearable medical devices. In this study, we captured ECG from 20 subjects when they were at rest and during routine activities. The motion artifact in ECG was filtered using two non-linear filters: median filter and discrete dyadic wavelet transform. Signal-to-noise ratio (SNR) and computation time of the filters were determined. We found that median filter showed larger SNR (7.61±1.21 dB) than discrete dyadic wavelet transform did (5.35±1.34 dB). Conversely, discrete dyadic wavelet transform benefited to its short computation time. The algorithms of these non-linear filters should be further investigated to achieve both high SNR and fast computation in wearable and mobile monitoring systems.

Can the Timing-Characteristics of Phonocardiographic Signal be Used for Cuffless Systolic Blood Pressure Estimation?

Continuous and non-invasive measurement of blood pressure (BP) is always important to critically ill patients. To achieve continuous and cuffless BP monitoring, pulse transit time (PTT) has been reported as a potential parameter. Recently a novel parameter RS2 (defined as the time interval measured from the R wave of electrocardiographic (ECG) signal to the peak of second heart sound of phonocardiographic (PCG) signal) is proposed for the same purpose. In this study, the relationship between systolic BP (SBP) and PTT as well as the relationship between SBP and RS2 on 25 healthy subjects, aged 24plusmn3 years, were compared after exercise. The results in current study showed that SBP is correlated with both PTT and RS2, where the mean individual correlations are r=-0.95 and r=-0.85 respectively. The mean standard deviation of the differences between the measured SBP and the SBP predicted from the regression lines in scatter plots of SBP~PTT and SBP~RS2 are 4.1 mmHg and 7.2 mmHg respectively. In summary, the results showed that RS2 is possible to be used for continuous and non-invasive monitoring of SBP after exercise. In the future, it is important to investigate more robust techniques for locating characteristic points on the PCG signals

Impedance cardiography for cuffless and non-invasive measurement of systolic blood pressure

In this study, we have used impedance cardiography to determine blood pressure (BP) cufflessly and non-invasively. We have devised a new parameter, QdZ [the duration measured from the foot of electrocardiogram (ECG) Q wave to the peak of impedance cardiogram (ICG)], for this purpose. Twenty-two subjects performed four minutes of treadmill exercise such that systolic BP (SBP) was increased significantly. We found that SBP was closely correlated with QdZ (R2=0.65) demonstrating the potential application of ICG to cuffless and non-invasive BP measurement.

The time-frequency analysis of variabilities of heart rate, systolic blood pressure and pulse transit time on normotensive subjects after exercise

Spectral components of cardiovascular oscillations are related to complex autonomic control mechanisms. Since these oscillations are non-stationary, time-frequency (T-F) analysis has been used in studying cardiovascular oscillations such as variabilities of heart rate and blood pressure; however, few studies have extended the T-F analysis to other cardiovascular signals such as pulse transit time (PTT). In this preliminary study, a T-F analysis method based on a time-variant autoregressive model was used to study the beat to beat spectra of R-R interval (RRI) of electrocardiogram, systolic blood pressure (SBP) and PTT on 8 normotensive subjects after exercise. It is observed from the results that spectra of RRI, SBP and PTT comprised of two distinguished components in the 0.03–0.15 Hz and 0.18–0.4 Hz respectively and that the spectra of SBP and PTT were relatively similar compared to spectra of RRI. However, the beat to beat power spectral densities (PSD) of the signals were not the same all the time. Furthermore, a physiological mechanism-based model was proposed for the generation of ECG, BP and PPG signals, and to interpret the phenomena observed in experiments. Further investigation is needed to quantify this similarity and to study the inherent correlations and mechanisms mediating these cardiovascular oscillations.

Study on the Responses of Hypertensive Patients to Music

Many clinical findings indicate that certain types of music can reduce blood pressure (BP) under various medical conditions. Therefore, it is of great interest to investigate the BP responses of hypertensive patients to music and to what extent the music can help them to lower their BP if they listen to the selected music daily. Fifteen subjects from an elderly home participated in the study. Eight of them had initial systolic BP (SBP) higher than 140 mmHg. They listened to the selected music for 25 minutes per day for 4 weeks. BP was measured twice a week by a registered nurse with a sphygmomanometer during the 4-week study period and after the completion of the study. Three subjects, including one with initial SBP higher than 140 mmHg, dropped during the experiment due to changes of medical conditions or personal reasons. After 4 weeks, the average decrease in SBP and diastolic BP (DBP) was 11.8 mmHg (p=0.008) and 4.7 mmHg (p=0.218) (n=12), respectively. For the subgroup of subjects with initial SBP higher than 140 mmHg, the average decrease in SBP and DBP was 19.9 mmHg (p<0.001) and 8.5 mmHg (p=0.087) (n=7), respectively. The results demonstrated that listening to a certain type of music may serve as an alternative method to reduce high SBP and the responses of hypertensive patients to music depend on the baseline BP.

The long-term effect of music on hypertensive patients

Previous studies of physiological responses to music showed the reduction of blood pressure (BP) under various medical conditions. However, the long-term lasting effect of music on hypertensive patients has not been systematically investigated. In this study, 30 subjects aged 63-93 years were enrolled and randomly assigned into either a music group (n=15) or a control group (n=15). There were no significant differences between two groups in initial BP values, age, and gender. Subjects in the music group listened to selected music, 25 min every day for 4 weeks. Four subjects dropped from the experiment due to a change of medical conditions or personal reasons. Immediately and 4 weeks after the completion of 4-weekpsilas music treatment, the average changes for the music group (n=12) in systolic BP (SBP) were -.7plusmn18 mmHg (p=0.01) and -10.3plusmn17.2 mmHg (p=0.04), in diastolic BP (DBP) were -4.6plusmn9.8 mmHg (p=0.22) and 4.0plusmn13 mmHg (p=0.24), respectively, whereas there were no significant changes in SBP or DBP for the control group (n=14). The results suggested that listening to a certain type of music may reduce high SBP and the effect could last up to four weeks.

The Variabilities of Blood Pressure and Pulse Arrival Time in Normotensive Young Subjects under Dynamic Conditions

Investigators are paying more attention to blood pressure variability (BPV) because of its associations with target-organ damage in hypertensive subjects and cardiovascular morbidity. In spite of its importance, parameter for continuous and non-invasive BPV estimation has not been studied systematically. In this study, the relationships between the variabilities of BP and pulse arrival time (PAT) were investigated on 8 normotensive subjects (aged 28plusmn4 years) under resting and dynamic conditions. The continuous brachial BP and intermittent arterial BP were measured by Finometerreg and automatic BP machine respectively. The BPV and PATV were regarded as the beat-to-beat differences of BP and PAT respectively. The results of this study showed that arterial SBP increased significantly (p<0.05) after exercises but the increase of arterial DBP was insignificant. Furthermore, PATV was inversely correlated with SBPV in both resting (r=-0.56) and post-exercise (r =-0.58) conditions but not with DBPV. In summary, the acute effects of exercises on the correlation between BPV and PATV after mild exercises should be further investigated in the future with improved experimental procedures and new design of dry electrodes.