Wrist ballistocardiography and invasively recorded blood pressure in healthy volunteers during reclining bike exercise

Paced breathing causes tonic change rather than phasic modulation of superficial venous diameter

BACKGROUND

Respiratory modulation is generally observed in the inferior vena cava (IVC). If similar respiratory modulation exists in peripheral superficial veins, it would be possible to dilate the vein diameter by respiratory control. This may improve the success rate of venipuncture in clinical practices. Hence, the present study aimed to investigate the respiratory modulation in peripheral superficial veins.

METHODS

This study included 21 healthy female volunteers (mean age 21.8 ± 0.9 years). Participants performed spontaneous breathing (SB) and paced breathing (PB). B-mode ultrasound imaging was used to continuously monitor the cutaneous veins of the left elbow fossa for 50 s.

RESULTS

Vein diameter demonstrated a clear modulation consistent with paced breathing, and the amplitude of vein diameter modulation was greater at 10 s-PB than at 3 s-PB. Additionally, PB affected the baseline of modulation (mean vein diameter). The baseline exhibited the largest diameter in SB, followed by 3 s-PB and 10 s-PB. The baseline for SB and 10 s-PB demonstrated a statistically significant difference (p = 0.03). Respiratory modulation was confirmed in peripheral superficial veins; however, tonic change in baseline diameter was dominant over phasic modulation. Even when vein diameter was most dilated at 10 s-PB, the diameter at that time was smaller than the mean diameter at SB.

CONCLUSIONS

This study demonstrated that the peripheral superficial vein diameter exhibited respiratory modulation, similar to the IVC. Although respiratory modulation of the IVC has been well documented in previous studies, the present findings provide novel evidence of this phenomenon in the peripheral superficial veins. Additionally, this study identified tonic changes in the mean vein diameter, which were more dominant than phasic modulations. Furthermore, the mean vein diameter during SB was greater than the maximum diameter observed during 10 s-PB. These findings suggested that PB for 50 s during venipuncture did not enhance venous access.

Electrically Stable and Reliably Adhered E-Skin for Heart Health Monitoring

Electronic skin (e-skin) has been extensively investigated for its potential application in heart health monitoring, such as screening cardiovascular diseases and evaluating cardiac activity. Nevertheless, the poor electrical stability of traditional metal electrodes and insufficient adhesion of ordinary flexible substrates are primary impediments that hinder its further product marketing in the healthcare field. Herein, we propose a novel integrated e-skin that incorporates embedded stretchable electrodes with high electrical stability (within 20% strain) and a microsucker array with improved adhesion, which facilitates the effective reduction of motion artifact interference. Moreover, a wireless heart health monitoring system based on the e-skin is designed to realize synchronous electrocardiogram (ECG) and ballistocardiogram (BCG) detection by collecting chest epidermal mechano-acoustic signals and vibration-voltage signals. The monitoring results of the same adult volunteer indicate that the ECG and BCG data recorded by this system have good consistency with data from commercial cardiovascular monitoring devices. Furthermore, the ECG and BCG signal monitoring results of different volunteers further validated the potential of this system in cardiovascular disease diagnosis and long-term heart health monitoring.

Cardiac output estimation using ballistocardiography: a feasibility study in healthy subjects

There is no reliable automated non-invasive solution for monitoring circulation and guiding treatment in prehospital emergency medicine. Cardiac output (CO) monitoring might provide a solution, but CO monitors are not feasible/practical in the prehospital setting. Non-invasive ballistocardiography (BCG) measures heart contractility and tracks CO changes. This study analyzed the feasibility of estimating CO using morphological features extracted from BCG signals. In 20 healthy subjects ECG, carotid/abdominal BCG, and invasive arterial blood pressure based CO were recorded. BCG signals were adaptively processed to isolate the circulatory component from carotid (CCc) and abdominal (CCa) BCG. Then, 66 features were computed on a beat-to-beat basis to characterize amplitude/duration/area/length of the fluctuation in CCc and CCa. Subjects' data were split into development set (75%) to select the best feature subset with which to build a machine learning model to estimate CO and validation set (25%) to evaluate model's performance. The model showed a mean absolute error, percentage error and 95% limits of agreement of 0.83 L/min, 30.2% and - 2.18-1.89 L/min respectively in the validation set. BCG showed potential to reliably estimate/track CO. This method is a promising first step towards an automated, non-invasive and reliable CO estimator that may be tested in prehospital emergencies.