Acute psychological stress has a multifaceted impact on cardiovascular physiology, including increases in chronotropy, inotropy, and vascular tone. Chronic exposure to stress may greatly increase cardiovascular risk. To examine the cardiovascular impact of acute stress comprehensively, new multimodal portable monitoring solutions are needed. We examined the feasibility of using a compact multimodal wearable patch to measure laboratory-based stress-induced cardiovascular responses in a diverse sample with recent myocardial infarction (MI) and healthy participants (N = 37, 28 MI) during a protocol with a public-speaking stressor. Using the electrocardiogram, seismocardiogram, and photoplethysmogram captured from the device, we found several significant (p < 0.05) autonomic changes in the pooled sample suggesting stress activation: increases in heart rate, chest photoplethysmogram amplitude, and perfusion index and decreases in heart rate variability, left ventricular ejection time, pulse arrival time, and pulse transit time. We, thus, demonstrated that a single wearable device can capture stress-induced cardiovascular changes, enabling simultaneous examination of stress-induced inotropic, chronotropic, and vascular effects. This portable, wireless chest patch may be useful in comprehensively and unobtrusively examining stress-induced cardiovascular effects in-lab. Given the public health importance of psychological stress and cardiovascular disease, future studies should assess the device’s full clinical potential in larger groups with longer monitoring periods.

Cold exposure activates thermoregulatory processes through the autonomic nervous system that, while maintaining homeostasis, reduce peripheral blood flow and dexterity in the extremities. Transcutaneous median nerve stimulation (tMNS) represents a promising method for autonomic regulation through activation of parasympathetic vagal nerve afferents to the brain. However, the effect of this type of non-invasive therapy has not been investigated thoroughly in the context of thermoregulation. We analyzed peripheral skin temperature data in an ancillary study from a cohort of 19 participants who underwent two study visits of a protocol, each involving a dose-response activity, a cold pressor activity, and either tMNS or sham stimulation. Data from each protocol segment was averaged and then normalized as a percent difference from a baseline rest section. Paired t-tests and Pitman-Morgan tests were run on data from the cold pressor and dose-response activities respectively to determine statistical significance. We found that tMNS had a significant$(p=0.036)$effect of blunting peripheral skin temperature drops during cold pressor recovery as compared to sham stimulation. Additionally, tMNS had a general regulatory effect on skin temperature change during the dose-response activity, with significantly less variance than sham stimulation$(p<0.05)$. These results indicate that possible regulation of peripheral skin temperature with tMNS can serve as a therapy for cold exposure. Future work should investigate this mechanism in a larger cohort with a protocol designed to assess reactivity in temperature and dexterity to both cold and heat exposure.

Pleural effusion (PE) affects millions of people and is caused by a wide variety of underlying diseases. The excess of fluid in the pleural cavity leads to shortness of breath and increased risk for infections that require timely interventions. Yet, existing clinical assessments lack the temporal resolution for continuous monitoring of PE and associated respiratory symptoms. Novel wearable technologies capable of measuring multi-frequency transthoracic bioimpedance (BioZ) continuously hold promise for PE monitoring. In this study, we evaluated the feasibility of monitoring a bilateral PE in a pig model using continuous multi-frequency transthoracic BioZ obtained with a previously-validated wearable device. A novel multi-resolution approach yielded strong and significant correlations to the infused PE at the DClbaseline, respiratory windows, and breath-by-breath resolutions. A total of 1.65 L of saline was infused bilaterally, first left then right, in steps of 275 mL. The low-frequency DC resistance yielded the strongest correlation to the PE size (R2=O.99, −14%/L, p

BACKGROUND: Posttraumatic stress disorder (PTSD) causes heightened fight-or-flight responses to traumatic memories (i.e., hyperarousal). Although hyperarousal is hypothesized to cause irregular breathing (i.e., respiratory variability), no quantitative markers of respiratory variability have been shown to correspond with PTSD symptoms in humans. OBJECTIVE: In this study, we define interpretable markers of respiration pattern variability (RPV) and investigate whether these markers respond during traumatic memories, correlate with PTSD symptoms, and differ in patients with PTSD. METHODS: We recruited 156 veterans from the Vietnam-Era Twin Registry to participate in a trauma recall protocol. From respiratory effort and electrocardiogram measurements, we extracted respiratory timings and rate using a robust quality assessment and fusion approach. We then quantified RPV using the interquartile range and compared RPV between baseline and trauma recall conditions, correlated PTSD symptoms to the difference between trauma recall and baseline RPV (i.e., ∆RPV), and compared ∆RPV between patients with PTSD and trauma-exposed controls. Leveraging a subset of 116 paired twins, we then uniquely controlled for factors shared by co-twins via within-pair analysis for further validation. RESULTS: We found RPV was increased during traumatic memories (p .001), ∆ RPV was positively correlated with PTSD symptoms (p .05), and patients with PTSD exhibited higher ∆ RPV than trauma-exposed controls (p . 05). CONCLUSIONS: This paper is the first to elucidate RPV markers that respond during traumatic memories, especially in patients with PTSD, and correlate with PTSD symptoms. SIGNIFICANCE: These findings encourage future studies outside the clinic, where interpretable markers of respiratory variability are used to track hyperarousal.

Studies of stress often assume that baseline periods, stressors, and neutral conditions elicit their intended responses. This assumption may not always hold. In this study, we use a comprehensive set of cardiovascular and respiratory markers to demonstrate that factors including habituation and apprehension can lead to unintended physiological responses. Re-analyzing the data from a previous investigation of traumatic stress, we studied N = 26 participants with history of prior trauma. These participants took part in a three-hour protocol involving repeated exposure to traumatic stressors and neutral conditions. Electrocardiogram, photoplethysmogram, seismocardiogram, and respiratory effort signals were collected. Unlike previous studies, we investigated the physiological responses to each neutral condition and traumatic stressor separately, rather than aggregating over repetitions. We find that habituation reduces the physiological responses to repeated traumatic stressors. We also observe transient stress responses during the first neutral conditions of the protocol. We attribute this stress to apprehension. Notably, the stress exhibited during the first neutral condition was on par with that of the second traumatic stressor. To our knowledge, the data herein are the first to quantitatively show that apprehension during a neutral condition can produce stress responses on par with trauma recall. These results advocate against classifying periods of data as "stress" or "no stress" based solely on the protocol. Instead, studies of stress should incorporate physiological sensing to assess whether the protocol’s intended effects are consistent with observed changes in physiological markers.

Acute decompensated heart failure (ADHF) is one of the leading causes for hospitalization in the US. Patient’s weight and limb girth are monitored to assess medication efficacy and readiness for hospital discharge. Such metrics are assessed manually by a trained professional at discrete time intervals, thereby missing potentially critical information about treatment responsiveness. Full, upper, and lower-body bioimpedance analysis have shown promise in tracking changes in patient weight, but requires bulky systems to place electrodes across different limbs. In this work, we evaluate the use of convenient ankle limb bioimpedance for tracking fluid status changes in a proof-of-concept dataset obtained in 9 hospitalized patients with ADHF. Continuous bioimpedance measurements were recorded while the patients received diuretic treatment for more than 2 days. Biomarkers derived from the low-frequency bioimpedance measurements, ratio of low-to-high bioimpedance measurements and limb girth were significantly different from hospital admission to discharge. Bioimpedance measures correlated to changes in weight (Pearson’s r = − 0.63, subject-specific), and limb girth (Pearson’s r = − 0.83 and r = − 0.87, subject-specific and global, respectively). Such bioimpedance measures captured from the ankle in a wearable form-factor and in a continuous manner provide better insight to the patient’s acute response to medication. Such a tool can be further used to better schedule medications and alter dosage in the clinic and be sent home with patients to detect fluid accumulation early.

Stress leads to widespread peripheral effects, including manifestations of respiratory distress. The combination of respiratory monitoring and non-invasive Peripheral Nerve Stimulation (PNS) represents a promising technological approach to quantify and reduce the physiological manifestations of stress. Such technologies require non-invasive, reliable respiratory information with adequate signal quality during various conditions. In this work, we computed an established respiratory quality index (RQI) on four respiratory signals derived from three common respiratory sensing modalities (respiratory effort (RSP), electrocardiogram-derived respiration (EDR), and Impedance Pneumography (IP)) in a complex stress protocol wherein 15 subjects underwent three stressors while receiving 1 of 3 active PNS modalities or sham. Our results indicate that the RQI of all signals changed substantially throughout the protocol with a maximal reduction from baseline of 21.28% (p< 0.001) during stressors involving speech. Further, RSP and IP resulted in the highest average quality and both were significantly higher in quality than the two EDR signals (p < 0.001). These results provide unique information that may inform the design of new technologies and studies leveraging respiratory markers for continuous stress detection and mitigation.

Chronic respiratory diseases affect millions and are leading causes of death in the US and worldwide. Pulmonary auscultation provides clinicians with critical respiratory health information through the study of Lung Sounds (LS) and the context of the breathing-phase and chest location in which they are measured. Existing auscultation technologies, however, do not enable the simultaneous measurement of this context, thereby potentially limiting computerized LS analysis. In this work, LS and Impedance Pneumography (IP) measurements were obtained from 10 healthy volunteers while performing normal and forced-expiratory (FE) breathing maneuvers using our wearable IP and respiratory sounds (WIRS) system. Simultaneous auscultation was performed with the Eko CORE stethoscope (EKO). The breathing-phase context was extracted from the IP signals and used to compute phase-by-phase (Inspiratory (I), expiratory (E), and their ratio (I:E)) and breath-by-breath acoustic features. Their individual and added value was then elucidated through machine learning analysis. We found that the phase-contextualized features effectively captured the underlying acoustic differences between deep and FE breaths, yielding a maximum F1 Score of 84.1 ±11.4% with the phase-by-phase features as the strongest contributors to this performance. Further, the individual phase-contextualized models outperformed the traditional breath-by-breath models in all cases. The validity of the results was demonstrated for the LS obtained with WIRS, EKO, and their combination. These results suggest that incorporating breathing-phase context may enhance computerized LS analysis. Hence, multimodal sensing systems that enable this, such as WIRS, have the potential to advance LS clinical utility beyond traditional manual auscultation and improve patient care.