Changes in the reactive hyperemia index after continuous and interval exercise.

INTRODUCTION: High-intensity interval exercise (HIIE) is more effective than moderate-intensity interval exercise (MICE) for improving macrovascular function (e.g., flow-mediated dilation), but less is known regarding the effect of HIIE on microvascular function. We used peripheral artery tonometry to measure the reactive hyperemia index (RHI) and examine the acute effects of HIIE and MICE on microvascular function. METHODS: Ten healthy participants (50% men, age: 26 ± 5 years, mass: 75.6 ± 15.1 kg, height: 170 ± 10 cm, body mass index: 26.0 ± 3.1 kg∙m-2) performed single bouts of HIIE and MICE cycling on separate occasions. The MICE protocol was 20 min at 60% of maximum power output. The HIIE protocol was a 12-min warm up at 50% of maximum power output immediately followed by an 8-min Tabata protocol where participants alternated between cycling at ⩾ 100% max power (20 sec) and rest (10 sec). The RHI was measured before, immediately after, and 1 h after exercise and compared by two-way repeated measures analysis of variance (condition [MICE, HIIE] and time [pre-, post-, and 1-h postexercise]). RESULTS: Compared to baseline, RHI increased 1 h after MICE only (p = 0.02). Heart rate was higher during MICE at 5 and 10 min (p = 0.02) and higher during HIIE at min 20 (p < 0.01). CONCLUSION: Within a sample of healthy adults, the RHI was improved 1 h after a single session of MICE but not HIIE. Future research is needed to determine the significance of the differential effects of exercise regimens on the macro- and microvasculature.

What is the optimal chest compression depth during out-of-hospital cardiac arrest resuscitation of adult patients?

BACKGROUND: The 2010 American Heart Association guidelines suggested an increase in cardiopulmonary resuscitation compression depth with a target >50 mm and no upper limit. This target is based on limited evidence, and we sought to determine the optimal compression depth range. METHODS AND RESULTS: We studied emergency medical services-treated out-of-hospital cardiac arrest patients from the Resuscitation Outcomes Consortium Prehospital Resuscitation Impedance Valve and Early Versus Delayed Analysis clinical trial and the Epistry-Cardiac Arrest database. We calculated adjusted odds ratios for survival to hospital discharge, 1-day survival, and any return of circulation. We included 9136 adult patients from 9 US and Canadian cities with a mean age of 67.5 years, mean compression depth of 41.9 mm, and a return of circulation of 31.3%, 1-day survival of 22.8%, and survival to hospital discharge of 7.3%. For survival to discharge, the adjusted odds ratios were 1.04 (95% CI, 1.00-1.08) for each 5-mm increment in compression depth, 1.45 (95% CI, 1.20-1.76) for cases within 2005 depth range (>38 mm), and 1.05 (95% CI, 1.03-1.08) for percentage of minutes in depth range (10% change). Covariate-adjusted spline curves revealed that the maximum survival is at a depth of 45.6 mm (15-mm interval with highest survival between 40.3 and 55.3 mm) with no differences between men and women. CONCLUSIONS: This large study of out-of-hospital cardiac arrest patients demonstrated that increased cardiopulmonary resuscitation compression depth is strongly associated with better survival. Our adjusted analyses, however, found that maximum survival was in the depth interval of 40.3 to 55.3 mm (peak, 45.6 mm), suggesting that the 2010 American Heart Association cardiopulmonary resuscitation guideline target may be too high. CLINICAL TRIAL REGISTRATION URL: http://www.clinicaltrials.gov. Unique identifier: NCT00394706.

Evaluation of respiratory function during Reeves stretcher use.

OBJECTIVE: We were aware of a small number of cases in our EMS system where patients in respiratory distress had a worsening of their condition after being removed from the home on a Reeves stretcher (RS). We sought to determine if this prehospital lifting device causes additional respiratory effort used in normal subjects by describing changes in heart rate, pulse oximetry, tidal volume, minute ventilation, and respiratory rate. METHODS: Forty-nine subjects were entered into this study. Data were collected while the subject was supine on the floor in the RS and once while suspended over the floor in the device. A randomized crossover design was used. Ten subjects were excluded because of inadvertent omission of a nose plug during spirometry. Data points were recorded in the final minute of a 3-minute exposure. Three minutes was chosen to simulate a prehospital transport time from the scene to the ambulance. Minute ventilation, tidal volume, heart rate, pulse oximetry, and respiratory rate were recorded for each subject during each phase. Subjects were also asked to rate the difficulty of breathing using the modified Borg scale. RESULTS: Data were obtained for 39 subjects. The mean respiratory rate while suspended was 9.9 +/- 3.0 breaths per minute compared to 9.1 +/- 2.5 breaths per minutes supine on the floor (p = 0.007). The mean minute ventilation while suspended in a RS was 8.17 +/- 3.25 L/min versus 7.37 +/- 2.37 while lying flat (p = 0.03). There was no difference in tidal volume, heart rate, pulse oximetry, or subjective modified Borg scale ratings. CONCLUSIONS: Subjects suspended in a RS for 3 minutes had statistically higher respiratory rates and minute ventilation than the same subjects lying flat. Although these modest changes are clinically insignificant in normal subjects, they could present a significant challenge to subjects in respiratory distress.

Training retention of Level C personal protective equipment use by emergency medical services personnel.

OBJECTIVES: To assess the six-month training retention for out-of-hospital providers donning and doffing Level C personal protective equipment (PPE). METHODS: In this prospective observational study, 36 out-of-hospital providers enrolled in a paramedic program were trained in Level C (chemical-resistant coverall, butyl gloves, and boots and an air-purifying respirator) PPE use. A standardized training module and checklist of critical actions developed by a hazardous materials (hazmat) technician were used to evaluate donning and doffing. Students were trained until they were able to correctly don and doff the Level C PPE. An investigator used the checklist accompanying the training module to assess proficiency and remediate mistakes. Six months after initial training, the subjects were reassessed using the same investigator and checklist. Errors were designated as either critical (resulted in major self-contamination of the airway, such as early removal of the respirator) or noncritical (potentially resulted in minor self-contamination not involving the airway). RESULTS: Only five subjects (14.3%) were able to don and doff PPE without committing a critical error. The most common critical errors were premature removal of the respirator (65.7%; n = 23) and actions allowing the contaminated suit to touch the body (54.3%; n = 19). The most common noncritical error was possible self-contamination due to the boots not being removed before exposing other body parts (37.1%; n = 13). Of the seven subjects (20%) with additional prior hazmat training, only two donned and doffed PPE without committing a critical error. CONCLUSIONS: Retention of proper donning and doffing techniques in paramedic students is poor at six months after initial training. Even in subjects with previous hazmat, firefighter, and emergency medical services training, critical errors were common, suggesting that current training may be inadequate to prevent harmful exposures in emergency medical services personnel working at a hazmat or weapons of mass destruction incident.