Reduction in Hospital Transfers at a US COVID-19 Alternate Care Site: Maintaining Surge Capacity Support in Imperial County, California.

OBJECTIVE: The transfer rate for patients from an Alternate Care Site (ACS) back to a hospital may serve as a metric of appropriate patient selection and the ability of an ACS to treat moderate to severely ill patients accepted from overwhelmed health-care systems. During the coronavirus infectious disease 2019 (COVID-19) pandemic, hospitals worldwide experienced acute surges of patients presenting with acute respiratory failure. METHODS: An ACS in Imperial County, California was re-established in November 2020 to help decompress 2 local hospitals experiencing surges of COVID-19 cases. The patients treated often had multiple comorbid illnesses and required a median supplemental oxygen of 3 L/min (LPM) on admission. Numerous interventions were initiated during a 2-wk period to improve clinical care delivery. RESULTS: The objectives of this retrospective observational study are to evaluate the impact of these clinical and staff interventions at an ACS on the transfer rate and to provide issues to consider for future ACS sites managing COVID-19 patients. CONCLUSIONS: The data suggest that continuous, real-time process-improvement interventions helped reduce the transfer rate back to hospitals from 36.7% to 14.5% and that an ACS is a viable option for managing symptomatic COVID-19 positive patients requiring hospital-level care when hospitals are overburdened.

Vascular and central hemodynamic changes following exercise-induced heat stress.

This study examined the effects of moderate exercise-induced heat stress (EIHS) on vascular function, central hemodynamic load and indices of coronary perfusion. Vascular-hemodynamic measures were collected in 12 healthy men (aged 22±3 years) pre and post 100 minutes of moderate, intermittent exercise in two randomized conditions: heat stress (HS; wearing firefighter personal protective equipment (PPE)), and no heat stress (NHS; wearing a cooling shirt and equivalent PPE weight). Aortic blood pressure, reflected wave pressure (Pb), systolic (SPTI) and diastolic pressure time-integral (DPTI), and aortic stiffness were assessed before and after each condition. SPTI was significantly greater, and DPTI and Pb were significantly lower for HS-post compared to NHS-post (p<0.05). Pulse wave velocity was not different between conditions. In conclusion, EIHS does not affect aortic stiffness, but increases indices of myocardial work and reduces indices of coronary perfusion which may be related to chronotropic responses to EIHS. The mismatch between oxygen demand and oxygen supply may increase cardiac vulnerability to ischemia during strenuous work in the heat.

Effect of base layer materials on physiological and perceptual responses to exercise in personal protective equipment.

Ten men (non-firefighters) completed a 110 min walking/recovery protocol (three 20-min exercise bouts, with recovery periods of 10, 20, and 20 min following successive bouts) in a thermoneutral laboratory while wearing firefighting personal protective equipment over one of four base layers: cotton, modacrylic, wool, and phase change material. There were no significant differences in changes in heart rate, core temperature, rating of perceived exertion, thermal discomfort, and thermal strain among base layers. Sticking to skin, coolness/hotness, and clothing humidity sensation were more favorable (p < 0.05) for wool compared with cotton; no significant differences were identified for the other 7 clothing sensations assessed. Separate materials performance testing of the individual base layers and firefighting ensembles (base layer + turnout gear) indicated differences in thermal protective performance and total heat loss among the base layers and among ensembles; however, differences in heat dissipation did not correspond with physiological responses during exercise or recovery.

The effect of precooling on cardiovascular and metabolic strain during incremental exercise.

The purpose of this study was to investigate the effect of precooling on the chronotropic index defined as the slope of the heart rate (HR) and oxygen uptake during incremental exercise. Ten men performed incremental exercise following 2 conditions: control (rest in a thermoneutral laboratory, 21.5 ± 0.7 °C; performed first) and precooling (cold-water immersion, 23.1 ± 0.2 °C). Prior to exercise, core temperature was significantly lower for precooling (36.6 ± 0.3 °C) compared with control (37.1 ± 0.4 °C; p < 0.001) and remained lower throughout exercise (p < 0.05). Time to volitional fatigue during the incremental exercise test was significantly longer in the control (914 ± 97 s) compared with precooling (889 ± 97 s; p = 0.015). Precooling reduced HR by 8-10 beats·min(-1) compared with control throughout exercise (peak HR: precooling, 178 ± 9 beats·min(-1); control, 188 ± 6 beats·min(-1); p = 0.001). Oxygen uptake did not differ between conditions (p > 0.05). The chronotropic index did not differ between conditions (p = 0.301); however, the y intercept was significantly lower (p = 0.009) for precooling (53.6 ± 11.0) compared with control (67.3 ± 11.0). Thus, the benefit of precooling was a lower HR that was maintained throughout exercise rather than a reduced rate of rise in HR. These results suggest the potential use of precooling to mitigate cardiovascular strain in individuals working at elevated metabolic rates. However, the reduced exercise time warrants consideration.

Effect of clothing layers in combination with fire fighting personal protective clothing on physiological and perceptual responses to intermittent work and on materials performance test results.

Personal protective clothing (PPC) shields firefighters from thermal and other occupational hazards; however, it also contributes to physiological and perceptual strain. This study examined the effect of clothing layers worn under structural fire fighting turnout gear (TOG) on physiological and perceptual responses during alternating work/recovery cycles and assessed the clothing ensembles' (PPC + base layer) material performance. Values are reported as mean ± standard error of the mean. Ten men (age, 21 ± 0.3 yr; height, 1.74 ± 0.02 m; weight, 74.3 ± 2.3 kg; VO2max, 58.9 ± 2.0 mL/kg/min) completed a 110-min alternating work/recovery walking protocol (three 20-min exercise bouts/10-, 20-, and 20-min recovery sessions) in a thermo-neutral (21.0°C, 58.7% RH) laboratory while wearing a cotton t-shirt (COT) or COT and a station uniform (SU) shirt under fire fighting TOG (COT+TOG and COT+SU+TOG, respectively). Changes in heart rate (HR), core temperature (Tco), skin temperature (Tsk), rating of perceived exertion (RPE), and thermal sensations (TS) were compared across exercise and recovery periods. During exercise sessions, HR, Tco, Tsk, and RPE reached similar levels for COT+TOG and COT+SU+TOG. During Recoveries 1, 2, and 3, mean chest Tsk decreased by 3.96, 6.64, and 6.49°C, respectively, for COT+TOG compared with 2.24, 3.78, and 4.09°C for COT+SU+TOG (p < 0.05 for each period). Change in TS differed during Exercise 1; however, mean peak TS corresponded to "hot" for both ensembles. This study demonstrates that the additional layer of clothing in the COT+SU+TOG ensemble imposed no greater level of physiological or perceptual strain during moderate-intensity work bouts compared with the COT+TOG ensemble. However, some modest benefits were experienced during the recovery sessions for the COT+TOG ensemble as evidenced by a lower chest Tsk. In addition, materials performance testing revealed COT+SU+TOG provided greater thermal protection (64.8 ± 1.9 vs. 56.4 ± 0.3 cal/cm(2); p < 0.05) and equivalent heat dissipation compared with COT+TOG. These findings could guide departmental decisions about the use of station shirts.

Firefighter's personal protective equipment and the chronotropic index.

The purpose of this study was to investigate the effects of personal protective equipment (PPE) on cardiovascular and metabolic responses during incremental exercise, and to determine if PPE affects the relationship between heart rate (HR) and oxygen uptake when expressed as the chronotropic index (CI). Ten male participants performed graded exercise tests under three conditions: control (CON), (PPE) and weighted vest (WV) (same weight as PPE). Time to exhaustion was significantly longer in the CON compared to the other conditions (p < 0.01). Submaximal oxygen uptake and HR were significantly lower in the CON compared to the PPE and WV conditions. The CI (CON, 32.2 ± 4.5; PPE, 31.7 ± 5.7; WV, 32.6 ± 4.9) was similar in all three conditions. This study has shown that additional weight and encapsulating clothing leads to elevations in HR and oxygen uptake compared to a control condition, however, the CI remains unaffected. PRACTITIONER SUMMARY: Firefighters wear personal protective equipment that is designed to protect the wearer; however it also imposes a physiological burden. It is known that work in firefighting PPE increases cardiovascular and metabolic strain. This study has shown that PPE does not alter the relationship between heart rate and oxygen uptake.