Heart Rate Complexity in US Army Forward Surgical Teams During Pre Deployment Training

Reliability of carotid-femoral arterial waveforms for the derivation of ultra-short term heart rate variability in injured British servicemen: An inter-rater reliability study

In this study, the comparative precision of carotid versus femoral arterial waveforms to measure ultra-short term heart rate variability (HRVUST) following traumatic injury was investigated for the first time. This was an inter-rater reliability study of 50 British servicemen (aged 23-44 years) with non-acute combat-related traumatic injury (CRTI). Paired continuous arterial waveform data for HRVUST analysis, were simultaneously sampled at the carotid and femoral arterial sites (14-16 seconds) during pulse wave velocity (PWV) measurement. HRVUST was reported as the root mean square of the successive differences (RMSSD). Following the determination of the superior sampling site (carotid versus femoral), the blinded inter-rater agreement in RMSSD for the preferred site was quantified using the Intra-class Correlation Coefficient (ICC) and the Bland-Altman plot. The mean age of participants was 34.06±4.88 years. The femoral site was superior to the carotid site with a significantly higher number of reliable signals obtained (Fisher's Exact test; p<0.001). The inter-rater agreement in femoral-derived RMSSD was excellent [ICC 0.99 (95%CI: 0.994-0.997)] with a moderate level of agreement (mean difference [bias]: 0.55; 95% CI: -0.13-1.24 ms). In this study, we demonstrated that the femoral artery is a more reliable site than the carotid artery for HRVUST measurement and post-trauma risk stratification following CRTI.

Association between non-acute Traumatic Injury (TI) and Heart Rate Variability (HRV) in adults: A systematic review and meta-analysis

Heart rate variability (HRV) is a non-invasive measure of autonomic function. The relationship between unselected long-term traumatic injury (TI) and HRV has not been investigated. This systematic review examines the impact of non-acute TI (>7 days post-injury) on standard HRV indices in adults. Four electronic databases (CINAHL, Medline, Scopus, and Web of Science) were searched. The quality of studies, risk of bias (RoB), and quality of evidence (QoE) were assessed using Axis, RoBANS and GRADE, respectively. Using the random-effects model, mean difference (MD) for root mean square of successive differences (RMSSD) and standard deviation of NN-intervals (SDNN), and standardized mean difference (SMD) for Low-frequency (LF): High-Frequency (HF) were pooled in RevMan guided by the heterogeneity score (I2). 2152 records were screened followed by full-text retrieval of 72 studies. 31 studies were assessed on the inclusion and exclusion criteria. Only four studies met the inclusion criteria. Three studies demonstrated a high RoB (mean RoBANS score 14.5±3.31) with a low QoE. TI was associated with a significantly higher resting heart rate. Meta-analysis of three cross-sectional studies demonstrated a statistically significant reduction in RMSSD (MD -8.45ms, 95%CI-12.78, -4.12, p<0.0001) and SDNN (MD -9.93ms, 95%CI-14.82, -5.03, p<0.0001) (low QoE) in participants with TI relative to the uninjured control. The pooled analysis of four studies showed a higher LF: HF ratio among injured versus uninjured (SMD 0.20, 95%CI 0.01-0.39, p<0.04) (very low QoE). Albeit low QoE, non-acute TI is associated with attenuated HRV indicating autonomic imbalance. The findings might explain greater cardiovascular risk following TI. Trial registration PROSPERO registration number: CRD: CRD42021298530.

Cardiac autonomic disturbance following resistance and sprint-interval exercises in non-obese and obese young men

This study examined the alterations of heart rate variability (HRV) following iso-duration resistance (RES) and sprint-interval (SIE) exercises by comparing with that of non-exercise control (CON) in 14 non-obese (NOB) and 15 obese (OB) young men. Time and frequency domain measures as well as non-linear metrics of HRV were assessed before and immediately after exercise, and during every 20 min until 120 min post exercise. The variables during the first 4 hrs of actual sleep time at night, and the period of 12-14 hrs post exercise were also measured. All trials were scheduled at 20:00. It was found that RES and SIE attenuated the HRV in both NOB and OB (P <0.05), and the attenuated HRV restored progressively during subsequent recovery. Although the changes in HRV indices among various time points during the recovery period and its interaction across RES, SIE and CON were not different between NOB and OB, the restoration of the declined HRV indices to corresponding CON level in the two exercise trials in OB appeared to be sluggish in relative to NOB. Notwithstanding, post-exercise HRV that recorded during actual sleep at night and during 12-14 hrs apart from exercise were unvaried among the three trials in both groups (P>0.05). These findings suggest that obesity is likely to be a factor hindering the removal of exercise-induced cardiac autonomic disturbance in young men. Nonetheless, the declined HRV following both the RES and SIE protocols were well restored after a resting period of ~10 hrs regardless of obesity. The study was registered at ISRCTN as DOI:10.1186/ISRCTN88544091.

Potential causes of the preoperative increase in the rectosigmoid cyclic motor pattern: A high-resolution manometry study

Background

Cyclic motor patterns (CMPs) are the most common motor pattern in the distal colon. This study used high‐resolution (HR) colonic manometry to quantify trends in distal colonic motor activity before elective colonic surgery, determine the effect of a preoperative carbohydrate load, and compare this with a meal response in healthy controls.

Methods

Fiber‐optic HR colonic manometry (36 sensors, 1 cm intervals) was used to investigate distal colonic motor activity in 10 adult patients prior to elective colonic surgery, 6 of whom consumed a preoperative carbohydrate drink (200 kCal). Data were compared with nine healthy volunteers who underwent HR colonic manometry recordings while fasted and following a 700 kCal meal. The primary outcome was the percentage of recording occupied by CMPs, defined as propagating contractions at 2–4 cycles per minute (cpm). Secondary outcomes included amplitude, speed, and distance of propagating motor patterns.

Results

The occurrence of CMPs progressively increased in time periods closer to surgery (p = 0.001). Consumption of a preoperative drink resulted in significantly increased CMP occurrence (p = 0.04) and propagating distance (p = 0.04). There were no changes in amplitude or speed of propagating motor patterns during the preoperative period. The increase in activity following a preoperative drink was of similar magnitude to the colonic meal response observed in healthy controls, despite the lesser caloric nutrient load.

Conclusion

Distal colonic CMP increased in occurrence prior to surgery, amplified by ingestion of preoperative carbohydrate drinks. We hypothesize that anxiety, which is also known to rise with proximity to surgery, could play a contributing role.

Monitoring stress and allostatic load in first responders and tactical operators using heart rate variability: a systematic review

BACKGROUND

Awareness of the cumulative stress placed on first responders and tactical operators is required to manage acute fatigue, which can impair occupational performance, and may precipitate negative chronic health outcomes. The aim of this review was to investigate the utility of heart rate variability (HRV) to monitor stress and allostatic load among these populations.

METHODS

A systematic search of Academic Search Complete, MEDLINE complete, PsycINFO, SPORTDiscus and Scopus databases was conducted. Eligibility criteria: original peer reviewed research articles, written in English, published between 1985 and 2020, using human participants employed as a first responder or tactical operator, free from any psychological disorder.

RESULTS

Of the 360 articles screened, 60 met the inclusion criteria and were included for full text assessment. Articles were classified based on single or repeated stressor exposure and the time of HRV assessment (baseline, during stressor, post stressor). Singular stressful events elicited a reduction in HRV from baseline to during the event. Stressors of greater magnitude reduced HRV for extended durations post stressor. Lower resting HRV was associated with lower situational awareness and impaired decision-making performance in marksmanship and navigation tasks. There were insufficient studies to evaluate the utility of HRV to assess allostatic load in repeated stressor contexts.

CONCLUSION

A reduction in HRV occurred in response to acute physical and cognitive occupational stressors. A slower rate of recovery of HRV after the completion of acute occupational stressors appears to occur in response to stressors of greater magnitude. The association between lower HRV and lower decision-making performance poses as a useful tool but further investigations on within subject changes between these factors and their relationship is required. More research is required to investigate the suitability of HRV as a measure of allostatic load in repeated stress exposures for fatigue management in first responder and tactical operators.