Original Contribution
The physiological effects and quality of chest compressions during CPR at sea level and high altitude,☆☆,☆☆☆

https://doi.org/10.1016/j.ajem.2014.07.007Get rights and content

Abstract

Background

Rescuers that undergo acute ascent without acclimatization can experience acute mountain sickness. Although performing cardiopulmonary resuscitation (CPR) for a short period requires intensive effort at sea level, performing CPR at high altitude is even more exhausting and can endanger the rescuer. Therefore, we conducted a pilot study to compare the quality of resuscitation in health professionals at high altitude (3100 m) and that at sea level.

Methods

Thirty-eight participants were asked to performed continuous chest compression CPR (CCC-CPR) for 5 minutes at sea level and at high altitude. Cardiopulmonary resuscitation recording technology was used to objectively quantify the quality of the chest compressions (CCs), including the depth and rate thereof.

Results

At high altitude, rescuers showed a statistically significant decrease in blood oxygen saturation and an increase in systolic blood pressure, diastolic blood pressure, heart rate, and fatigue, as measured with the Borg score, after CCC-CPR compared with resting levels. The analysis of the time-dependent deterioration in the quality of CCC-CPR showed that the depth of CCs declined from the mean depth of the first 30 seconds after CCC-CPR to that at more than 120 seconds after CCC-CPR at both sea level and high altitude. The average number of effective CCs declined after CCC-CPR was performed for 1 minute at sea level and high altitude.

Conclusions

The quality of CC rapidly declined at high altitude. At high altitude, the average number of effective CC decreases; and this decrease became significant after continuous CCs had been performed for 1 minute.

Introduction

A growing number of people visit mountainous areas worldwide. While ascending to high altitude, a number of acute physiological changes occur [1]. Cardiac arrest is the second most common cause of death in the mountains [2].

If a time-sensitive rescue operation is necessary, usually, no acclimatization time is available for rescuers. Prolonged cardiopulmonary resuscitation (CPR) at high altitude presents a significant physical challenge to rescuers. After continuous single-operator CPR at high altitude for 5 minutes, the rescuer’s arterial blood oxygen saturation (Spo2) decreases; and the rescuer’s Borg scale score, a subjective score of fatigue, becomes higher than that at sea level [3], [4]. Although a comprehensive review by Chalkias et al [1] addressed several important issues and proposed reasonable recommendations for CPR and the considerations of rescuers at high altitude, most guidelines for resuscitation do not provide specific recommendations for CPR at high altitude [1], [5]. Nonetheless, physiological changes during exercise at high altitude have been studied extensively, which, in conjunction with results indicating quality changes, should able to provide a rationale for modifying current guidelines regarding CPR performed at high altitude.

The quality of CPR is paramount to advanced cardiac life support. Previous studies have demonstrated that the return of the spontaneous circulation in patients experiencing an out-of hospital cardiac arrest is dependent on the quality of the CPR they receive [6], [7], [8]. Several investigations have also shown that improved outcomes are associated with greater chest compression depth [9], [10]. The quality of chest compressions during CPR has been demonstrated to decline rapidly after a short period [11], [12]. A number of simulations have shown that rescuers develop immediate fatigue during CPR and that chest compression depth declines after 1 to 3 minutes of CPR [12], [13], [14]. During continuous chest compression CPR (CCC-CPR), chest compressions are minimally interrupted; but the depth of compressions decreases more rapidly than in conventional CPR [15]. Data regarding the quality of CPR performed by rescuers and the acute physiological effects of CCC on rescuers at high altitude are still limited. Therefore, this pilot study aimed to compare the time-dependent deterioration of CCC-CPR quality and the acute physiological effects of CPR on rescuers at sea level and high altitude. We provide recommendations on how to best perform CPR at high altitude.

Section snippets

Data collection

Thirty-eight volunteers 18 years of age or older who had completed a basic life support and CPR training course in accordance with the 2010 American Heart Association (AHA) guidelines were recruited for this study. All of the participants were health care providers, including medical staff of a tertiary medical center and emergency medical technicians. The participants were also enrolled to establish a rescue team. Comprehensive demographic data were collected for all participants. This

Results

The baseline characteristics of the study participants are shown in Table 1. Thirty-eight volunteers were enrolled in this study, and 33 participants completed the 5-minute CCC-CPR at high altitude (3100 m). Five participants did not complete the 5-minute CCC-CPR at high altitude because they were tired and asked to cease the test.

Before CPR, the participants’ SBP and DBP were not significantly different between sea level and high altitude (Table 2). The pre-CPR LLS and Borg scores at high

Discussion

Our study showed a difference in the quality of chest compressions performed at sea level and high altitude. The results demonstrated that, at high altitude, the depth of chest compressions declined rapidly, reaching statistical significance at 60 seconds after the initiation of CCC-CPR. At high altitude, the average depth of chest compressions decreased to less than 5 cm and approached statistical significance after CCC-CPR for 2 minutes. Furthermore, prior to the observed decline in depth,

Conclusion

This is the first study to assess the quality of CPR performed by health care providers at high altitude using a real-time monitoring device. The quality of chest compressions rapidly declined at high altitude. In addition, the average number of effective chest compressions decreased after CCC-CPR was performed for 1 minute; and the average depth of chest compressions decreased to less than 5 cm after CCC-CPR was performed for 2 minutes. More research is needed to evaluate the appropriate

Acknowledgments

We gratefully acknowledge Kaz Hanamura and all members of KISSEI COMTEC CO, LTD, for their instruction in the operation of the Chest Compression Coach System. We also thank all of the ED staff at Tri-Service General Hospital for volunteering to participate in the study.

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    The authors declare that they received no financial support and have no disclosures.

    ☆☆

    Grants: DV101-04 and DV102-02 from the Ministry of National Defense–Medical Affairs Bureau and Taipei Veterans General Hospital.

    ☆☆☆

    Conflict of interest statement: There are no conflicts of interest to declare.

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