Physiological and Perceived Effects of Forearm or Head Cooling During Simulated Firefighting Activity and Rehabilitation.

CONTEXT: Cooling devices aim to protect firefighters by attenuating a rise in body temperature. Devices for head cooling (HC) while firefighting and forearm cooling (FC) during rehabilitation (RHB) intervals are commonly marketed, but research regarding their efficacy is limited. OBJECTIVE: To investigate the physiological and perceived effects of HC and FC during firefighting drills and RHB. DESIGN: Randomized controlled clinical trial. SETTING: Firefighter training center. PATIENTS OR OTHER PARTICIPANTS: Twenty-seven male career firefighters (age = 39 ± 7 years; height = 169 ± 7 cm; weight = 95.4 ± 16.8 kg). INTERVENTION(S): Firefighters were randomly assigned to 1 condition: HC (n = 9), in which participants completed drills wearing a cold gel pack inside their helmet; FC (n = 8), in which participants sat on a collapsible chair with water-immersion arm troughs during RHB; or control (n = 10), in which participants used no cooling devices. Firefighters completed four 15-minute drills (D1-D4) wearing full bunker gear and breathing apparatus. Participants had a 15-min RHB after D2 (RHB1) and D4 (RHB2). MAIN OUTCOME MEASURE(S): Change (Δ) in gastrointestinal temperature (TGI), heart rate (HR), physiological strain index, and perceived thermal sensation. RESULTS: The TGI increased similarly in the HC and control groups, respectively (D1: 0.57°C ± 0.41°C, 0.73°C ± 0.30°C; D2: 0.92°C ± 0.28°C, 0.85°C ± 0.27°C; D3: -0.37°C ± 0.34°C, -0.01°C ± 0.72°C; D4: 0.25°C ± 0.42°C, 0.57°C ± 0.26°C; P > .05). The ΔHR, Δ physiological strain index, and Δ thermal sensation were similar between the HC and control groups during drills (P > .05). The FC group demonstrated a decreased TGI compared with the control group after RHB1 (-1.61°C ± 0.35°C versus -0.23°C ± 0.34°C; P < .001) and RHB2 (-1.40°C ± 0.38°C versus -0.38°C ± 0.24°C; P < .001). The physiological strain index score decreased in the FC group compared with the control group after RHB1 (-7.9 ± 1.3 versus -2.6 ± 1.7; P < .001) and RHB2 (-7.9 ± 1.6 versus -3.6 ± 1.1; P < .001), but no differences between groups were demonstrated for ΔHR or Δ thermal sensation (P > .05). CONCLUSIONS: The HC did not attenuate rises in physiological or perceptual variables during firefighting drills. The FC effectively reduced TGI and the physiological strain index score but not HR or thermal sensation during RHB. Clinicians and firefighters should not recommend the use of HC during firefighting but can consider using FC during RHB intervals in the field.

Electrocardiographic abnormalities as potential contributors to premature mortality in patients with mental illness in a psychiatric day treatment program.

OBJECTIVE: Because patients with mental illness can die prematurely, we sought to determine if undetected cardiovascular disease might be present in a psychiatric day treatment population. METHOD: We studied 96 patients in a day treatment program seen between February 2011 and August 2012. Data were obtained through an electronic medical record database. Electrocardiographic diagnoses were assigned by 1 investigator (M.L.). Medications were categorized into classes, and problem lists revealed comorbid diagnoses. Fisher exact test (2-tailed) and analysis of variance were used to compare findings between patient groups. Electrocardiogram (ECG) findings were the primary outcome measure. RESULTS: Ninety-two ECGs were performed in 37 patients. Of these 37 patients, 70% were women, 65% were 50 years of age or younger, and 54% were people of color. ECGs were performed mainly for chest pain/dyspnea (46%) and overdose/altered mental status (27%). Of these 37 patients, 20 (54%) had abnormal ECGs, 7 (19%) had borderline findings, and 10 (27%) had normal studies. When compared with the larger group of 59 patients without ECG testing, those with abnormal ECGs were more likely to be older (mean age = 47 vs 37 years, P < .001) and have more comorbid conditions (mean no. = 10.0 vs 3.8, P < .0001). The most common abnormalities were conduction disorders (prolonged QRS ≥ 105 ms, or prolonged QTc ≥ 450 ms in men or ≥ 460 ms in women), coronary artery disease, and arrhythmias. CONCLUSIONS: In psychiatric outpatients who underwent ECG testing, mainly for chest pain or altered mental status, over 50% had concerning findings. Older patients with multiple comorbidities were at higher risk of having abnormal ECGs. Generalizability of these findings depends on validation in larger samples in multiple settings.

The acid-activated ion channel ASIC contributes to synaptic plasticity, learning, and memory.

Many central neurons possess large acid-activated currents, yet their molecular identity is unknown. We found that eliminating the acid sensing ion channel (ASIC) abolished H(+)-gated currents in hippocampal neurons. Neuronal H(+)-gated currents and transient acidification are proposed to play a role in synaptic transmission. Investigating this possibility, we found ASIC in hippocampus, in synaptosomes, and in dendrites localized at synapses. Moreover, loss of ASIC impaired hippocampal long-term potentiation. ASIC null mice had reduced excitatory postsynaptic potentials and NMDA receptor activation during high-frequency stimulation. Consistent with these findings, null mice displayed defective spatial learning and eyeblink conditioning. These results identify ASIC as a key component of acid-activated currents and implicate these currents in processes underlying synaptic plasticity, learning, and memory.