The PaCO2-ETCO2 gradient in pre-hospital intubations of all aetiologies from a single UK helicopter emergency medicine service 2015-2018.

Background: Control of the arterial partial pressure of carbon dioxide (PaCO2) is important in the ventilated patient. End-tidal carbon dioxide (ETCO2) levels are often used as a proxy, but are clinically limited. The difference between the PaCO2 and ETCO2 has been suggested to be 0.5-1.0 kPa. However, this has not been consistently reflected in the physiologically unstable pre-hospital patient. This study aims to elucidate the PaCO2-ETCO2 gradient for pre-hospital intubated patients. Methods: This was a retrospective, cohort study using data identified from the HEMSbase 2 database (Feb 2015-Nov 2018). Patients were included if they had documented ETCO2 and arterial PaCO2 measurements. Arterial PaCO2 data that could not be linked to within 5 minutes of ETCO2 were excluded. Bland-Altman plots were calculated to describe agreement. Results: A total of 73 patients were identified. Aetiology was arranged into three categories: 13 (17.8%) medical, 22 (30.1%) traumatic and 38 (52.1%) out-of-hospital cardiac arrest (OHCA). The median PaCO2-ETCO2 gradient was 2.0 [1.3-3.1] kPa. A PaCO2-ETCO2 gradient of 0-1 kPa was seen for only 11 (15.1%) of total patients. The Bland-Altman agreement for all aetiologies was more than the accepted gradient of 0-1 kPa with the largest bias and widest limits of agreement seen for OHCA (-3.2 [0.3 - -6.8]). Conclusion: The magnitude of the differences between the ETCO2 and PaCO2, levels of variation and inability to predict this suggest that ETCO2 is not a suitable surrogate upon which to base ventilatory settings in conditions where pH or PaCO2 require precise control.

Comparison of deliberate self-harm incidents attended by Helicopter Emergency Medical Services before and during the first wave of COVID-19 in the East of England.

INTRODUCTION: There is significant interest in the mental health impact of the COVID-19 pandemic. Helicopter Emergency Medical Services (HEMS) attend the most seriously unwell and injured patients in the community; their data therefore present an early opportunity to examine self-harm trends. The primary aim was to compare the incidence of deliberate self-harm incident (DSH-I) encounters by HEMS before and during the first wave of COVID-19. METHODS: Data were obtained from all three East of England HEMS: total number of activations and stand-downs, number of DSH-I activations and stand-downs, self-harm mechanism and number of 'severe' DSH-I patient encounters, in two 61-day periods: 1 March to 30 April in 2019 (control) and 2020 (COVID-19). Severe DSH-I was defined as cardiac arrest and/or died prehospital. Proportions were compared with a Fisher's exact test. RESULTS: There were a total of 1725 HEMS activations: n=981 (control) and n=744 (COVID-19), a decrease of 24.2% during COVID-19. DSH-I patient encounters increased by 65.4%: n=26 (control) and n=43 (COVID-19). The proportion of encounters that were DSH-I and severe DSH-I both significantly increased during COVID-19: p=0.002 and p=0.001, respectively. The absolute number of hangings and falls from height both approximately tripled during COVID-19, whereas the number of other mechanisms remained almost constant. CONCLUSION: Despite a reduction in overall HEMS patient encounters, there were significant increases in both the proportion of DSH-Is and their severity attended by HEMS during the first wave of the COVID-19 pandemic in the East of England.

Markers of physiological stress during exercise under conditions of normoxia, normobaric hypoxia, hypobaric hypoxia, and genuine high altitude.

PURPOSE: To investigate whether there is a differential response at rest and following exercise to conditions of genuine high altitude (GHA), normobaric hypoxia (NH), hypobaric hypoxia (HH), and normobaric normoxia (NN). METHOD: Markers of sympathoadrenal and adrenocortical function [plasma normetanephrine (PNORMET), metanephrine (PMET), cortisol], myocardial injury [highly sensitive cardiac troponin T (hscTnT)], and function [N-terminal brain natriuretic peptide (NT-proBNP)] were evaluated at rest and with exercise under NN, at 3375 m in the Alps (GHA) and at equivalent simulated altitude under NH and HH. Participants cycled for 2 h [15-min warm-up, 105 min at 55% Wmax (maximal workload)] with venous blood samples taken prior (T0), immediately following (T120) and 2-h post-exercise (T240). RESULTS: Exercise in the three hypoxic environments produced a similar pattern of response with the only difference between environments being in relation to PNORMET. Exercise in NN only induced a rise in PNORMET and PMET. CONCLUSION: Biochemical markers that reflect sympathoadrenal, adrenocortical, and myocardial responses to physiological stress demonstrate significant differences in the response to exercise under conditions of normoxia versus hypoxia, while NH and HH appear to induce broadly similar responses to GHA and may, therefore, be reasonable surrogates.

Incidence of acute mountain sickness in UK Military Personnel on Mount Kenya.

BACKGROUND: Acute mountain sickness (AMS) is a common problem of trekkers to high altitude. The UK military train at high altitude through adventurous training (AT) or as exercising troops. The ascent of Point Lenana at 4985 m on Mount Kenya is frequently attempted on AT. This study sought to establish the incidence of AMS within this population, to aid future planning for military activities at altitude. METHODS: A voluntary questionnaire was distributed to all British Army Training Unit Kenya based expeditions attempting to ascend Mount Kenya during the period from February to April 2014. The questionnaire included twice daily Lake Louise and Borg (perceived exertion scale) self-scoring. All expeditions were planned around a 5-day schedule, which included reserve time for acclimatisation, illness and inclement weather. RESULTS: Data were collected on 47 participants, 70% of whom reached the summit of Point Lenana. 62% (29/47) self-reported AMS (defined as Lake Louise score (LLS) ≥3) on at least one occasion during the ascent, and 34% (10/29) suffered severe AMS (LLS ≥6). Those who attempted the climb within 2 weeks of arrival in Kenya had a higher incidence of AMS (12/15 (80%) vs 17/32 (53%), p=0.077). Participants recording a high Borg score were significantly more likely to develop AMS (16/18 vs 9/21, p=0.003). CONCLUSIONS: This represents the first informative dataset for Mount Kenya ascents and altitude. The incidence of AMS during AT on Mount Kenya using this ascent profile is high. Adapting the current ascent profile, planning the ascent after time in country and reducing perceived exertion during the trek may reduce the incidence of AMS.