Heart rate profiles and heart rate variability during scuba diving.

AIMS: The aim of the present study was to describe heart rate profiles and heart rate variability patterns in non-selected scuba divers of different ages under non-experimental real-world conditions. METHODS: We used specially designed silver-loaded polydimethylsiloxane dry electrodes for underwater ECG recordings. With a custom-built setup, heart rate profiles and heart rate variability patterns were documented before submersion, during diving and after resurfacing in 18 separate dives. RESULTS: Heart rates of the divers just before descent were remarkably high (median 114 bpm, interquartile range [IQR] 83-154) with a statistically significant rapid decrease after submersion (median 90 bpm, IQR 70-116; p = 0.008). The percentage heart rate reduction by submersion was individually very variable (median 21%, range 5-39%). We noted a general increase in autonomic nervous system (ANS) activity without predominance of parasympathetic parameters, suggesting a concomitant sympatheticadrenergic activation. CONCLUSIONS: Scuba diving under real-world conditions by non-selected divers is characterised by relatively high heart rates just before submersion, an individually variable but significant bradycardic dive response, and induces an immediate and sustained parallel increase of parasympathetic and sympathetic-adrenergic autonomic nervous system activity. These observations could explain several specific pathophysiological mechanisms of diving incidents (haemodynamic decompensation, arrhythmias, acute coronary syndromes) and underlines the importance of cardiovascular risk stratification in diving eligibility assessment.

Efficacy of intramuscular hydroxocobalamin supplementation in cats with cobalamin deficiency and gastrointestinal disease.

BACKGROUND: In humans, absorption and tissue retention rates of intramuscularly administered hydroxocobalamin (OH-Cbl) are superior compared to cyanocobalamin (CN-Cbl). Supplementation with OH-Cbl has not been described in cats. OBJECTIVES: To evaluate effects of parenteral OH-Cbl supplementation on clinical signs, serum Cbl and methylmalonic acid (MMA) concentrations in hypocobalaminemic cats with gastrointestinal disease. ANIMALS: Twenty-three client-owned cats. METHODS: Prospective study. Serum Cbl and MMA concentrations were determined at enrollment (t0), immediately before the 4th OH-Cbl IM injection (300 µg, given q2 weeks) (t1), and 4 weeks after the 4th injection (t2). Severity of clinical signs (activity, appetite, vomiting, diarrhea, body weight) was graded at each time point and expressed as clinical disease activity score. RESULTS: Median clinical disease activity score decreased significantly from t0 (6; range, 2-10) to t1 (1; range, 0-6) and t2 (1; range, 0-9). Median serum Cbl concentration increased significantly from 111 pmol/L (range, 111-218; reference range, 225-1451 pmol/L) at t0 to 1612 pmol/L (range, 526-14 756) (P < .001) at t1, and decreased again significantly to 712 pmol/L (range, 205-4265) (P < .01) at t2. Median baseline serum MMA concentration at t0 (802 nmol/L; range, 238-151 000; reference range, 120-420 nmol/L) decreased significantly (P < .001) to 199 nmol/L (range, 29-478) at t1, and was 205 nmol/L (range, 88-734) at t2. Serum MMA concentrations normalized in 22/23 cats at t1, and were not significantly higher at t2 compared to t1. CONCLUSIONS AND CLINICAL IMPORTANCE: The herein described OH-Cbl injection scheme appears efficacious for normalization of cellular Cbl deficiency in cats with gastrointestinal disease.

Effects of storage conditions and duration on cobalamin concentration in serum samples from cats and dogs.

OBJECTIVE To evaluate the effects of storage conditions and duration on cobalamin concentration in serum samples from dogs and cats. DESIGN Experiment. SAMPLE Serum samples from 9 client-owned cats and 9 client-owned dogs. PROCEDURES Serum harvested from freshly obtained blood samples was separated into 11 aliquots/animal. One aliquot (baseline sample) was routinely transported in light-protected tubes to the laboratory for cobalamin assay; each of the remaining aliquots was stored in a refrigerator (6°C; n = 5) or at room temperature (20°C) with exposure to daylight (5) for 24, 48, 72, 96, or 120 hours. Aliquots were subsequently wrapped in aluminum foil, frozen (-20°C), and then transported to the laboratory for measurement of cobalamin concentration, all in the same run. Percentage decrease in cobalamin concentration from baseline was analyzed by means of linear mixed modeling. RESULTS No differences in cobalamin values were identified between cats and dogs; therefore, data for both species were analyzed together. Median baseline serum cobalamin concentration was 424 ng/L (range, 178 to 1,880 ng/L). Values for serum samples stored with daylight exposure at room temperature were significantly lower over time than were values for refrigerated samples. Although values for refrigerated samples did not decrease significantly from baseline values over time, values for the other storage condition did; however, the mean percentage decrease for serum samples stored at room temperature was small (0.14%/h; 95% confidence interval, 0.07% to 0.21%/h). CONCLUSIONS AND CLINICAL RELEVANCE Overall, serum cobalamin concentration appeared stable for 5 days when feline and canine serum samples were refrigerated at 6°C. The effect of light and room temperature on serum cobalamin concentration, although significant, was quite small for samples stored with these exposures for the same 5-day period.

Specialist advice may improve patient selection for decompression therapy following diving accidents: a retrospective observational study.

BACKGROUND: Even in a landlocked country like Switzerland recreational diving is becoming more and more popular. Smaller lakes in the Alps are located at an altitude of 2500 m above sea level. The incidence of diving accidents among all helicopter emergency service missions and the consecutive medical knowledge about decompression injuries is low. Thus, a collaboration between the Swiss Air-Ambulance (Rega) and the divers alert network (DAN) was initiated to improve patient treatment and identification of decompression injury and necessity of hyperbaric oxygen therapy (HBO). METHODS: Retrospective observational study that includes all patients treated by the Rega which have been classified to have had a diving accident from 2005 to 2014. Patient and diving epidemiology was assessed and the impact of DAN collaboration on patient selection and identification of patients needing transport to HBO facilities were analysed. RESULTS: In the 10-year observational period 116 patients with diving accidents were treated by Rega. Mean patient age was 40 (SD 11) years and 95 (82%) were male. If the Rega emergency physician suspected a decompression injury (DCI), without DAN contact 27/28 (96%) of these patients were transported directly to a HBO facility, whereas with DAN contact only 53/63 (84%) needed transport to a HBO facility. DAN was involved in 66/96 (69%) of the cases with suspected DCI on scene, with a significant increase over time (p = 0.001). Mean flight time to HBO facilities was significantly longer (28.9, SD 17.7 min.), compared to non-HBO facilities (7.1, SD 3.2 min., p < 0.001). Due to specialist advice, patients may have been selected who finally did not need a transport to a HBO facility, although DCI was primarily suspected by the emergency physician on the scene. These patients experienced a significantly reduced flight time to the (non-HBO) hospital of 25.6 (SD 6.5) min. (p < 0.001). DISCUSSION: Collaboration of DAN and Rega may allow a safe patient selection and a consecutive reduction of flight time and costs. Due to international collaborations, evacuation to HBO-facilities for acute recompression therapy can be provided by HEMS within less than 30 min all over Switzerland. CONCLUSIONS: For diving accidents among HEMS missions, specialist advice by diving medicine specialists (DAN) appears mandatory to accurately identify and transport patients with decompression injury, as exposure of emergency physicians towards diving accidents and the diagnosis of DCI is low.