Individual and combined impact of hypoxia and acute inorganic nitrate ingestion on autonomic thermoregulatory responses to the cold [Abstract]

No description supplie

Reliability and validity of novel methods in the assessment of cold-induced shivering

Introduction: This study assessed the test-retest reliability and validity of four metrics of shivering onset; oxygen uptake (V̇O2), electromyography (EMG), mechanomyography (MMG) and bedside shivering assessment scale (BSAS). Methods: Ten volunteers attended three identical experimental sessions involving passive deep-body cooling via lower-body cold water immersion at 10°C water temperature. V̇O2, EMG and MMG were continuously assessed, while the time elapsed at each BSAS stage was recorded. To determine shivering onset, metrics were graphed as a function of time and rectal temperature (Trec). A baseline was visually identified, followed by two inflection points for intermittent and constant shivering. Inflection points were classified by three independent researchers and the median was used. Results: Shivering was observed across all subjects, with an onset time ranging from 1238 to 3367s across trials and metrics. Time provided a more reliable indicator of shivering onset than Trec (mean Intraclass Correlation [ICC]; time, 0.92; Trec, 0.83 ). MMG presented the most reliable indicator of shivering onset time between trials (ICC; intermittent shivering, 0.94; constant shivering, 0.96), followed by BSAS and V̇O2, while EMG presented the least reliable (ICC; intermittent, 0.84; constant, 0.82). Chronologically, MMG and EMG were similar in detecting onset, whereas a mean lag of 99s or 0.03°C Trec was seen in V̇O2 identification. A 312s or 0.13°C Trec lag was seen in BSAS identification compared to the mean of objective metrics. Signal-noise ratio favoured EMG (SNR, 1.99 ± 1.33), followed by MMG (SNR, 1.68 ± 0.51) and finally V̇O2 (SNR, 1.37 ± 0.24) in the analysis of inflection points. Conclusion: Good to excellent reliability can be seen across all metrics, yet given the observed lag times, SNR’s, along with known advantages/disadvantaged of each metric, it is recommended that no single metric should be used in isolation. These results have been used to develop an integrated multi-modal measure of shivering

Glycated hemoglobin vs fasting plasma glucose as a predictor of left ventricular dysfunction after st-elevation myocardial infarction

The World Health Organization and the American Diabetes Association recommend a level of glycated hemoglobin (HbA1c) ≥ 6.5% as diagnostic for diabetes. However, concordance between fasting plasma glucose (FPG) and HbA1c levels in acutely unwell patients is unknown. Furthermore, the prognostic value of HbA1c for left ventricular (LV) dysfunction is unclear. This study aimed to evaluate the concordance between HbA1c levels and FPG in consecutive patients with acute ST-elevation MI (STEMI) and compare their prognostic value in predicting LV dysfunction and elevated filling pressures on echocardiography.A total of 142 patients with a first incidence of STEMI were prospectively recruited. LV diastolic function was defined as mean septal and lateral early diastolic velocities (average e'); filling pressure was the ratio of transmitral E velocity to average e' (average E/e').Mean FPG and HbA1c levels were 7.7 ± 2.8 mmol/L and 6.5% ± 1.6%, respectively. Of 109 patients without previous diabetes, HbA1c levels identified an additional 18 patients (16.5%) as having diabetes, and the concordance with FPG was poor. Between diabetic and nondiabetic patients, there were no differences in LV end-diastolic volume (116 ± 37 vs 118 ± 43 mL; P = 0.78), end-systolic volume (69 ± 33 vs 68 ± 35 mL; P = 0.93), and ejection fraction (42 ± 12 vs 44 ± 11%; P = 0.49). On multivariable analyses, average e' was independently associated with HbA1c (β = -0.161; P = 0.045) but not FPG (P = 0.82). Similarly, average E/e' was independently associated with HbA1c (β = 0.168; P = 0.04) but not FPG (P = 0.32). Receiver operating characteristic curve analysis showed that an HbA1c cutoff of 6.4% (area under the curve, 0.68; P = 0.002) was associated with an elevated LV filling pressure.Only HbA1c was independently associated with impaired LV diastolic function and increased filling pressures after STEMI

Reliability and validity of methods in the assessment of cold-induced shivering thermogenesis

Purpose: To compare two analytical methods for the estimation of the shivering onset inflection point, segmental regression and visual inspection of data, and to assess the test-retest reliability and validity of four metrics of shivering measurement; oxygen uptake (V̇O2), electromyography (EMG), mechanomyography (MMG) and bedside shivering assessment scale (BSAS). Methods: Ten volunteers attended three identical experimental sessions involving passive deep-body cooling via cold water immersion at 10°C. V̇O2, EMG and MMG were continuously assessed, while the time elapsed at each BSAS stage was recorded. Metrics were graphed as a function of time and rectal temperature (Tre). Inflection points for intermittent and constant shivering were visually identified for every graph and compared to segmental regression. Results: Excellent agreement was seen between segmental regression and visual inspection (ICC, 0.92). All measurement metrics presented good to excellent test-retest reliability (ICC’s > 0.75 and 0.90 respectively), with the exception of visual identification of intermittent shivering for V̇O2 measurement (ICC, 0.73) and segmental regression for EMG measurement (ICC, 0.74). In the assessment of signal-to-noise ratio (SNR), EMG showed the largest SNR at the point of shivering onset, followed by MMG and finally V̇O2. Conclusions: Segmental regression provides a successful analytical method for identifying shivering onset. Good-excellent reliability can be seen across V̇O2, EMG, MMG and BSAS, yet given the observed lag times, SNR’s, along with known advantages/disadvantaged of each metric, it is recommended that no single metric is used in isolation. An integrative, real-time measure of shivering is proposed

Effect of virtual reality and whole-body heating on motion sickness severity: A combined and individual stressors approach

Background: Virtual reality (VR) use is limited by the potential side effects of prolonged exposure to vection, leading to motion sickness. Air temperature (Ta) may exacerbate the severity of such side effects through a synergistic interaction. This study assessed the individual and combined impact of a hot Ta and VR on motion sickness severity. Method: Thirteen healthy volunteers were exposed to a 20 min visual stimulus, across four experimental conditions: N_CS: 22 °C Ta with computer screen; N_VR: 22 °C Ta with VR; H_CS: 35 °C Ta with computer screen; H_VR: 35 °C Ta with VR. Motion sickness was assessed via fast motion sickness scale (FMS) and simulator sickness questionnaire (SSQ). Physiological indices of motion sickness including, sweat rate, rectal temperature, cutaneous vascular conductance (CVC), skin temperature, blood pressure and heart rate were also examined. Results: FMS and SSQ ratings indicate a significant main effect for VR, increasing sickness severity (p < 0.001). A significant main effect of Ta was observed for SSQ, but not FMS ratings (FMS, p = 0.07; SSQ, p < 0.04). Despite trends towards synergism, no interaction (Ta × VR) was observed for FMS (p = 0.2) or SSQ scores (p = 0.07), indicating an additive response. Synergistic trends were also observed for sweat rate and CVC. Conclusion: Synergism between VR and heat on motion sickness remains unclear, possibly as a result of considerable inter-individual variation in the reported subjective responses. Understanding of the questions raised by this study inform safe working guidelines for the use of VR in commercial and occupational settings

Reliability and validity of methods in the assessment of cold-induced shivering thermogenesis

Purpose: To compare two analytical methods for the estimation of the shivering onset inflection point, segmental regression and visual inspection of data, and to assess the test–retest reliability and validity of four metrics of shivering measurement; oxygen uptake (V̇O2), electromyography (EMG), mechanomyography (MMG) and bedside shivering assessment scale (BSAS). Methods: Ten volunteers attended three identical experimental sessions involving passive deep-body cooling via cold water immersion at 10 °C. V̇O2, EMG, and MMG were continuously assessed, while the time elapsed at each BSAS stage was recorded. Metrics were graphed as a function of time and rectal temperature (Tre). Inflection points for intermittent and constant shivering were visually identified for every graph and compared to segmental regression. Results: Excellent agreement was seen between segmental regression and visual inspection (ICC, 0.92). All measurement metrics presented good-to-excellent test–retest reliability (ICC’s > 0.75 and 0.90 respectively), with the exception of visual identification of intermittent shivering for V̇O2 measurement (ICC, 0.73) and segmental regression for EMG measurement (ICC, 0.74). In the assessment of signal-to-noise ratio (SNR), EMG showed the largest SNR at the point of shivering onset followed by MMG and finally V̇O2. Conclusions: Segmental regression provides a successful analytical method for identifying shivering onset. Good-to-excellent reliability can be seen across V̇O2, EMG, MMG, and BSAS, yet given the observed lag times, SNRs, along with known advantages/disadvantaged of each metric, it is recommended that no single metric is used in isolation. An integrative, real-time measure of shivering is proposed

Independent and combined impact of hypoxia and acute inorganic nitrate ingestion on thermoregulatory responses to the cold

Purpose: This study assessed the impact of normobaric hypoxia and acute nitrate ingestion on shivering thermogenesis, cutaneous vascular control, and thermometrics in response to cold stress. Method: Eleven male volunteers underwent passive cooling at 10 °C air temperature across four conditions: (1) normoxia with placebo ingestion, (2) hypoxia (0.130 FiO2) with placebo ingestion, (3) normoxia with 13 mmol nitrate ingestion, and (4) hypoxia with nitrate ingestion. Physiological metrics were assessed as a rate of change over 45 min to determine heat loss, and at the point of shivering onset to determine the thermogenic thermoeffector threshold. Result: Independently, hypoxia expedited shivering onset time (p = 0.05) due to a faster cooling rate as opposed to a change in central thermoeffector thresholds. Specifically, compared to normoxia, hypoxia increased skin blood flow (p = 0.02), leading to an increased core-cooling rate (p = 0.04) and delta change in rectal temperature (p = 0.03) over 45 min, yet the same rectal temperature at shivering onset (p = 0.9). Independently, nitrate ingestion delayed shivering onset time (p = 0.01), mediated by a change in central thermoeffector thresholds, independent of changes in peripheral heat exchange. Specifically, compared to placebo ingestion, no difference was observed in skin blood flow (p = 0.5), core-cooling rate (p = 0.5), or delta change in rectal temperature (p = 0.7) over 45 min, while nitrate reduced rectal temperature at shivering onset (p = 0.04). No interaction was observed between hypoxia and nitrate ingestion. Conclusion: These data improve our understanding of how hypoxia and nitric oxide modulate cold thermoregulation

Koinonia

Best Practice FeaturesLife on Life Learning: Steps Towards Authentic Mentoring, Brian Jensen The Heart of the Honor Code: I am My Brother\u27s Keeper, Emily J. Darnell Spotlight FeaturesOld People are Whole Persons, Too: Why Understanding Heritage is a Foundational Component of College Student Development, Philip Byers Ministry and Learning in Residence Life, Josh Arnold Shepherding in an Age of Edupunks, Drew Moser The Gap in the Curtain: Seeing Pieces of a Residential Community\u27s Future, David Johnstone InterviewsA Conversation with Juana Bordas, conducted by Rob Pepper Looking Into the Future: Two Educators\u27 Perspectives on Christian Higher Education, by Kim Stave and Ken Heffner (edited by Kirstin Vander Giessen-Reitsma) Book ReviewsThe Unlikely Disciple (by Kevin Roose), reviewed by Christopher Bohle ReflectionsSeven Greek Words that Mean the World to Me, Bob Crow FeaturesThe President\u27s Corner Editor\u27s Deskhttps://pillars.taylor.edu/acsd_koinonia/1013/thumbnail.jp