Effect of Acute Exposure to Altitude on the Quality of Chest Compression‐Only Cardiopulmonary Resuscitation in Helicopter Emergency Medical Services Personnel: A Randomized, Controlled, Single‐Blind Crossover Trial

Abstract

Background Helicopter emergency medical services personnel operating in mountainous terrain are frequently exposed to rapid ascents and provide cardiopulmonary resuscitation (CPR) in the field. The aim of the present trial was to investigate the quality of chest compression only (CCO)‐CPR after acute exposure to altitude under repeatable and standardized conditions. Methods and Results Forty‐eight helicopter emergency medical services personnel were divided into 12 groups of 4 participants; each group was assigned to perform 5 minutes of CCO‐CPR on manikins at 2 of 3 altitudes in a randomized controlled single‐blind crossover design (200, 3000, and 5000 m) in a hypobaric chamber. Physiological parameters were continuously monitored; participants rated their performance and effort on visual analog scales. Generalized estimating equations were performed for variables of CPR quality (depth, rate, recoil, and effective chest compressions) and effects of time, altitude, carryover, altitude sequence, sex, qualification, weight, preacclimatization, and interactions were analyzed. Our trial showed a time‐dependent decrease in chest compression depth ( P =0.036) after 20 minutes at altitude; chest compression depth was below the recommended minimum of 50 mm after 60 to 90 seconds (49 [95% CI, 46–52] mm) of CCO‐CPR. Conclusions This trial showed a time‐dependent decrease in CCO‐CPR quality provided by helicopter emergency medical services personnel during acute exposure to altitude, which was not perceived by the providers. Our findings suggest a reevaluation of the CPR guidelines for providers practicing at altitudes of 3000 m and higher. Mechanical CPR devices could be of help in overcoming CCO‐CPR quality decrease in helicopter emergency medical services missions. Registration URL: https://www.clinicaltrials.gov ; Unique identifier: NCT04138446.

Chest compressions at altitude are of decreased quality, require more effort and cannot reliably be self-evaluated

“…The authors analyze a secondary objective of a previous study that showed a reduction of chest compression (CC) depth at altitude [ 2 ] and show that heart rates are significantly higher at altitude before and after CPR. Such results support the results of a study that we recently published [ 3 ] as well one of Sato et al [ 4 ], where we both observed a significant decrease in peripheral oxygen saturation, an increase in heart rate, as well as an increase in fatigue during CPR at 3000 and 5000 m, and 3700 m, respectively. Conversely to Niederer et al, the forty-eight participants in our study, all helicopter emergency medical services (HEMS) providers, reached altitudes without physical effort simulating a rapid helicopter ascent in a hypobaric chamber [ 3 ].…”

“…Such results support the results of a study that we recently published [ 3 ] as well one of Sato et al [ 4 ], where we both observed a significant decrease in peripheral oxygen saturation, an increase in heart rate, as well as an increase in fatigue during CPR at 3000 and 5000 m, and 3700 m, respectively. Conversely to Niederer et al, the forty-eight participants in our study, all helicopter emergency medical services (HEMS) providers, reached altitudes without physical effort simulating a rapid helicopter ascent in a hypobaric chamber [ 3 ]. Nevertheless, we also observed an increase in heart rate during CPR that was even bigger compared to the one observed by Niederer et al and was dependent on the altitude reached.…”

“…Overall, the results of Niederer et al [ 1 , 2 ], as well as ours [ 3 ], show a greater effort and an impairment of the ability of providers to comply to resuscitation guidelines at altitude. Such impairment starts after 60 to 90 s of CC even in resting providers, so there is a significant risk that the depth of CCs can drop below the recommended 50 mm already before 2 min, when switching the CC provider is recommended by international CPR guidelines [ 5 ].…”

“…We did not investigate exhaustion but instead effort during CC. In our study the subjective effort, reported on a visual analogue scale (VAS), was significantly higher at 5000 m than at 200 and 3000 m [ 3 ]. As suspected by Niederer et al, we also showed that providers were not able to reliably self-evaluate the quality of CC at altitude.…”

Surgical masks and filtering facepiece class 2 respirators (FFP2) have no major physiological effects at rest and during moderate exercise at 3000-m altitude: a randomised controlled trial

“… 10 However, it is not known whether mask wearing at higher altitudes, either at rest or during physical activity, may influence blood gases to a greater extent. In such circumstances, hypoxaemia may impair physical 11 and cognitive performance, 12–14 negatively affecting work performance and occupational health, as well as increasing the risk of accidents. Besides hypoxaemia, wearing a mask may cause discomfort, affect wellbeing and challenge heat dissipation during exercise or hot weather conditions (while hypoxia further increases perceived exertion), which in turn may interfere with work performance or wearing adherence.…”