Research at the University of Chicago was halted in March 2020.

The purpose of this study is to evaluate the effect of breathing a slightly reduced amount of oxygen will have on a rescuer's ability to provide chest compressions during CPR.

Cardiac arrest can occur in any setting, even flying on a commercial airliner, and chest compressions are a critical, lifesaving component of cardiopulmonary resuscitation (CPR). If a cardiac arrest occurs on board a commercial flight, CPR may be administered by cabin crew members or health care professionals who are passengers and volunteer their assistance. The in-flight environment presents significant challenges, including an unfamiliar environment, an unknown patient, cramped space, and the fact that the pressure altitude in the cabin is between 6,000 feet and 8,000 feet. Even though the fraction of inspired oxygen (FiO2) is still 0.21, with decreased pressure the rescuer is effectively breathing a FiO2 of 0.15 and is mildly hypoxic. Although the decreased PaO2 seen in even in healthy passengers is a normal occurrence when flying on a commercial airliner, it may impair the ability of a rescuer to perform adequate CPR. Administering supplemental oxygen to the rescuer may enable provision of more effective chest compressions. In this study, we will measure the quality of chest compressions in normoxic and hypoxic conditions during short simulation scenarios. We hypothesize that chest compressions will be more effective in a normoxic environment.

All tasks are being performed for research purposes. All tasks will take place at the University of Chicago in an empty conference room. After the pre-study screening survey, subjects will be asked to perform chest compressions during a simulated cardiac arrest and will then fill out a survey. Subjects will participate in 2 sessions each; the sessions will be at least one day apart. During each session, the subject will wear a face mask. Subjects will be randomized and blinded to one of two conditions: During CPR, the subject will receive a FiO2 of 0.21 or 0.15 by face mask, which will produce a partial pressure of oxygen similar to, but slightly higher than, that of a commercial airliner. The gas mixture will be delivered by a normobaric hypoxia training device. During the second session, subjects will receive the other oxygen concentration.

Each session will consist of a simulation in which a passenger on an airplane (i.e., a mannequin) has an asystolic cardiac arrest. Participants will provide compression-only CPR. Every 2 minutes, the preceptor will ask the subject stop compressions for 10 seconds for a pulse and rhythm check, similar to actual established protocols. The participant will be wearing a pulse oximeter. The scenario will end after 30 minutes (14 rounds of 2 minutes each of CPR by the subject, consistent with the Universal Guidelines for Termination of CPR), or if the subject becomes fatigued and wishes to stop or is no longer providing high quality chest compressions.

Inclusion Criteria:

• Previous CPR training
• Baseline exercise tolerance of at least 4 metabolic equivalents (METS)

Exclusion Criteria:

• Heart disease
• Moderate or severe asthma
• Carpal tunnel syndrome
• Mononucleosis
• Respiratory infections
• Current injury (e.g., sprain, fracture, or dislocation)
• Acute or chronic muscle or joint pain
• Recent exposure to high altitude
• Any other condition that limits physical activity
• Any condition that precludes flying on a commercial airline flight

The participant is unaware of the oxygen concentration that he or she is breathing during either arm of the trial.