Effect of an Ultra-Endurance Event on Cardiovascular Function and Cognitive Performance in Marathon Runners.

Background: Ultra-marathon running participation has become increasingly more popular in recent years; however, there is inconclusive evidence concerning the effects of participation on cognition and cardiovascular function. The purpose of this study was to examine alterations in cardiovascular function and cognitive performance and their association in ultra-marathon runners prior to and following an ultra-endurance event. Methods: In total, 24 runners (19 males and 5 females) participated in an ultra-marathon race (FatDog120) held in British Columbia, Canada. Participants competed in varying races distances [48 km (n = 2), 80 km (n = 7), 113 km (n = 3), and 193 km (n = 12)]. Cognition was assessed prior to and upon race completion using simple reaction time, choice reaction time, discrimination reaction time, and recognition memory (% correct). Cardiovascular function was assessed prior to and upon race completion using radial applanation tonometry for diastolic pulse contour examination. Results: Cognitive performance displayed significantly (p < 0.001) slower reaction times post-race for simple (30.2%), discrimination (22.7%), and choice reaction time (30.5%), as well as a significant (p < 0.05) reduction in memory test performance (-8.2%). A significant association between systemic vascular resistance and choice reaction time was observed post-race (r = 0.41, p < 0.05). Significant changes in post-race cardiovascular function were observed in resting heart rate (31.5%), cardiac output (27.5%), mean arterial blood pressure (-5.6%), total systemic resistance (-17.6%), systolic blood pressure (-7.0%), pulse pressure (-11.2%), and rate pressure product (22.4%). There was evidence of enhanced cardiovascular function being associated with improved cognitive performance before and after the ultra-endurance event. Conclusion: Ultra endurance running is associated with marked impairments in cognitive performance that are associated (at least in part) with changes in cardiovascular function in healthy adults.

Exercise oscillatory ventilation during autonomic blockade in young athletes and healthy controls.

PURPOSE: Exercise oscillatory ventilation (EOV) is a form of periodic breathing that is associated with a poor prognosis in heart failure patients, but little is known about EOV in other populations. We sought to provide insights into the phenomenon of EOV after it was observed in young healthy subjects, including athletes, after the administration of dual autonomic blockade (DAB). METHODS: From 29 participants who completed cardiopulmonary exercise testing (CPET) with and without DAB (0.04 mg/kg atropine and 0.2 mg/kg metoprolol), 5 subjects developed EOV (age = 29 ± 5 years; 3/5 were athletes) according to American Heart Association criteria. For each case, we identified 2 non-EOV healthy controls (age = 34.2 ± 8.3; 7/10 were athletes) that were subsequently age- and sex-matched. RESULTS: No participants had EOV during exercise without DAB. The 5 participants (4 male, 1 female) who demonstrated EOV with DAB had lower mean tidal volume (1.7 ± 0.5 L/min vs. 1.8 ± 0.5 L/min; p = 0.04) compared to participants in the non-EOV group and a decrease in peak tidal volume (2.9 ± 0.6 L/min to 2.2 ± 0.7 L/min; p = 0.004) with DAB. There were few other differences in CPET measures between EOV and non-EOV participants, although the PETCO2 tended to be higher in the EOV group (p = 0.07). CONCLUSION: EOV can be elucidated in young healthy subjects, including athletes, during cardiopulmonary exercise testing, suggesting that it may not be an ominous sign in all populations.

Depression scores improve with continuous positive airway pressure in specialized sleep clinics: real-world data.

STUDY OBJECTIVES: To assess changes in Hospital Anxiety and Depression Scale (HADS) scores after continuous positive airway pressure (CPAP) in patients with obstructive sleep apnea. METHODS: Consecutive patients attending the Alfred Health sleep clinic, diagnosed with obstructive sleep apnea, and prescribed CPAP were recruited. The primary outcome was a change in the HADS depression (HADS-D) and anxiety (HADS-A) subscales from the time of diagnosis to follow-up. Secondary analysis compared high (> 4 hours) and low (< 4 hours) CPAP adherence groups and change in depression cases, defined by HADS-D ≥ 8, and anxiety cases, defined by HADS-A ≥ 11. RESULTS: We included 108 participants in the final analysis. Adherence groups were well matched in baseline mood, sleepiness, and apnea variables. Overall age (mean ± standard deviation) was 56.1 ± 12.8 years, and there was a median (interquartile ratio) apnea-hypopnea-index of 42.7 (27.5-58.1) or median (interquartile ratio) oxygen-desaturation-index of 43.0 (26.0-74.0). The median duration of CPAP therapy was 1.3 years. The HADS-D decreased after CPAP by -1.4 (adjusted 95% confidence interval, -2.1 to -0.6; P = .001). Patients with high-CPAP adherence (n = 84) had a tendency towards a greater reduction in HADS-D (-1.5) compared with those with low-CPAP adherence (n = 24; -0.3; adjusted P = .19). Depression cases (HADS-D ≥ 8) decreased by 13.1% in the high-CPAP-adherence group (P = .03) and increased by 4.1% in the low-CPAP-adherence group (P = .71). The HADS-A decreased after CPAP by -1.8 (adjusted 95% confidence interval, -1.8 to -0.4; P = .004). There was no significant difference between adherence groups or anxiety cases (HADS-A > 11). CONCLUSIONS: Specialized obstructive sleep apnea treatment with CPAP reduces depression scores, with a trend toward greater reduction in those with high CPAP adherence.

The association between heart rate variability, reaction time, and indicators of workplace fatigue in wildland firefighters.

PURPOSE: To understand the association between heart rate variability and indices of fatigue, total sleep time, and reaction time in shift workers. METHODS: Ten participants from the British Columbia Wildfire Service management team were examined over a 14-day active fire-line period. Daily measures of subjective fatigue, sleepiness, and alertness were recorded using a visual analog scale. Daily total sleep time was recorded using a wrist actigraph. Cardiac autonomic modulation was examined each morning using heart rate variability (HRV). Three measures of reaction time (simple reaction time, choice reaction tie, and discriminatory reaction time) was examined on days 1, 5, 10, and 14. Multiple linear regression analysis was utilized to examine the association between HRV and indices of fatigue, total sleep time, and reaction time. RESULTS: Mean shift duration was 13.8 ± 0.77 h. Significant inverse associations were observed between HRV and sleepiness [r = - 0.60, p = 0.000] and fatigue [r = - 0.55, p = 0.000], and a positive association with total sleep time (min) [r = 0.28, p = 0.009]. There were no significant relationships between HRV and simple reaction time (ms) [r = - 0.32, p = 0.182], choice reaction time (ms) [r = - 0.10, p = 0.850], or discriminatory reaction time (ms) [r = - 0.09, p = 0.881]. CONCLUSIONS: HRV displayed significant associations with indices of fatigue and sleep, whereby demonstrating its utility as a practical tool for monitoring the development of fatigue in wildland firefighters and for providing insight when to make lifestyle modifications to preserve alertness.

Fatigue and sleep patterns among Canadian wildland firefighters during a 17-day fire line deployment.

The purpose of this investigation was to enhance our understanding of the effects the current British Columbia Wildfire Service (BCWS) firefighting schedule have on the development of fatigue and sleep deprivation. This was a cohort study that objectively and subjectively measured sleep quantity, sleep quality, and fatigue throughout a 17-day British Columbia wildland firefighting deployment. Wildland firefighters (n = 30) conducted daily testing of sleep and fatigue measures during 14 days of activity on the fire line and three days immediately post deployment during their three-day rest period, for a total of 17 days of data collection. Sleep was assessed using wrist-worn actigraphy (ActiGraph LLC, Pensacola, FL) and subjective sleep questionnaires. Fatigue was assessed using subjective fatigue questionnaires and cognitive performance through the psychomotor vigilance test. Total sleep time was less on fire days (M = 6.6 h ± 49.2 min) compared to non-fire days (M = 6.8 h ± 92.2 min). Participants performed poorer on cognitive performance tests, (p = 0.288), and reported being significantly sleepier, (p = 0.038), toward the end of their 17-day deployment compared to day 1. Participants continued to report high levels of sleepiness, fatigue, and poor quality of sleep on their rest days compared to their fire line days. Working 14 consecutive days was associated with increased levels of objective fatigue and suboptimal sleep in wildland firefighters. Wildland firefighters reported significantly higher levels of fatigue and decreased alertness with increasing days on deployment and these levels did not improve following a three-day rest period.

Consecutive nursing shifts and the risk of hypoglycemia in critically ill patients who are receiving intravenous insulin: a multicenter study.

STUDY OBJECTIVES: Intensive care unit nurses commonly work multiple consecutive 12-hour shifts that leave little time for sleep between work shifts. Working multiple consecutive shifts could compromise vigilance and patient care, especially with respect to managing high-risk medications such as insulin infusions. We hypothesized that as the number of consecutive shifts worked by nurses increases, the rate of hypoglycemia in patients who are receiving an insulin infusion would also increase. METHODS: We identified patients who had hypoglycemia (glucose ≤ 3.5 mmol/L, 63 mg/dL) between December 2008 and December 2009 in 3 intensive care units in Vancouver, British Columbia, Canada. For each hypoglycemic event, we counted the number of shifts worked on consecutive days during the previous 72 hours by the bedside nurse who was caring for the patient at the time of hypoglycemia (case shift). For each case shift, we identified up to 3 control shifts (24, 48, and 72 hours before the hypoglycemic event in the same patient when there were no hypoglycemic events) and counted the number of consecutive shifts worked by those nurses in the previous 72 hours. This analysis allowed us to control for patient-associated confounders. Conditional logistic regression was used to determine the association between number of consecutive shifts worked and occurrence of hypoglycemic events. RESULTS: A total of 282 hypoglycemic events were identified in 259 patients. For 191 events, we were able to identify 1 or more control shifts. Compared with nurses who had not worked a shift in the preceding day, the odds ratio of a hypoglycemic event was 1.68 (95% confidence interval: 1.12-2.52), 2.16 (95% confidence interval:1.25-3.73), and 2.54 (95% confidence interval: 1.28-5.06) for nurses who were working their second, third, or fourth consecutive shift, respectively. CONCLUSIONS: Working multiple consecutive nursing shifts is associated with increased risk of hypoglycemic events in patients in an intensive care unit.

Validity of the Elite HRV Smartphone Application for Examining Heart Rate Variability in a Field-Based Setting.

Perrotta, AS, Jeklin, AT, Hives, BA, Meanwell, LE, and Warburton, DER. Validity of the elite HRV smartphone application for examining heart rate variability in a field-based setting. J Strength Cond Res 31(8): 2296-2302, 2017-The introduction of smartphone applications has allowed athletes and practitioners to record and store R-R intervals on smartphones for immediate heart rate variability (HRV) analysis. This user-friendly option should be validated in the effort to provide practitioners confidence when monitoring their athletes before implementing such equipment. The objective of this investigation was to examine the relationship and validity between a vagal-related HRV index, rMSSD, when derived from a smartphone application accessible with most operating systems against a frequently used computer software program, Kubios HRV 2.2. R-R intervals were recorded immediately upon awakening over 14 consecutive days using the Elite HRV smartphone application. R-R recordings were then exported into Kubios HRV 2.2 for analysis. The relationship and levels of agreement between rMSSDln derived from Elite HRV and Kubios HRV 2.2 was examined using a Pearson product-moment correlation and a Bland-Altman Plot. An extremely large relationship was identified (r = 0.92; p < 0.0001; confidence interval [CI] 95% = 0.90-0.93). A total of 6.4% of the residuals fell outside the 1.96 ± SD (CI 95% = -12.0 to 7.0%) limits of agreement. A negative bias was observed (mean: -2.7%; CI 95% = -3.10 to -2.30%), whose CI 95% failed to fall within the line of equality. Our observations demonstrated differences between the two sources of HRV analysis. However, further research is warranted, as this smartphone HRV application may offer a reliable platform when assessing parasympathetic modulation.