Perceived Stress Levels, Performance During a Simulated CPR
Perceived Stress Levels, Performance During a Simulated CPR
This study was conducted at the Simulator Center of the University Hospital in Basel, Switzerland, between December, 2007 and May, 2008. Workshops were offered to 4th year medical students and presented as a learning experience in a patient simulator. Prior to this simulation, no CPR training had been offered to the students within their medical curriculum. No information about the content of the scenarios and about our specific hypotheses was provided to students before the study (blinding).
The study was done in compliance with the Helsinki Declaration, approved by the local ethical committee (Ethikkommission beider Basel, EKBB, http://www.ekbb.ch/), and written informed consent was obtained from all participants.
For this study, we used a high fidelity manikin with the possibility of remote control of vital signs (Human Patient Simulator, METI). This full body simulator is a computer-based manikin with human physiology emulation capability that also can interact very realistically, e.g. by talking.
This is a prospective randomized controlled study. Prior to the test-scenario, all students were made familiar with the simulator in a baseline training session followed by a general video-assisted debriefing focusing on ACLS algorithms (Figure 1). Students were then randomly allocated to two different randomization arms using computer generated randomization lists. Students in the control group did not receive any further instructions. Students in the intervention group received a 10 minute instruction to cope with stress. They were informed that an emergency situation is a stressful experience for health care workers and that perceived stress may interfere with their decision-making abilities and performance. Particularly, feeling overwhelmed by stress may cause cognitive impairment potentially leading to loss of concept how to deal with an emergency situation, which in turn further increases stress (vicious cycle). However, it is possible to overcome this situation by focusing on the basic conditions of the situation and the immediate actions that are needed. They were instructed that they should ask two task-focusing questions aloud ("what is the patient's condition?", "what immediate action is needed?") to overcome the negative consequences of feeling overwhelmed by stress.
(Enlarge Image)
Figure 1.
Flow chart of randomisation groups. N denotes number of participants.
The test-scenario was a simulated witnessed cardiac arrest. Students performed the test-scenario alone. They were supported by a nurse, blinded to the experimental condition, who was instructed to be active on request only and not provide any information concerning CPR algorithms. When students entered the simulator room, the patient was conscious and responded to the questions of the students. Two minutes after the medical student started to take the medical history, the patient fainted and the monitor displayed ventricular tachycardia.
Upon completion of the simulation, perceived levels of stress and feeling overwhelmed were measured for different time points during the study period: (a) the baseline period immediately before resuscitation, (b) during the resuscitation period, (c) when the "patient" awakes, and d) during the debriefing period after the resuscitation. For each time point, we asked the students to quantify perceived levels of stress and feeling overwhelmed, measured on a Likert scale ranging from 1–20 (1 being lowest and 20 being highest). In a previous study, we found that perceived stress was best represented by a combination of these two items: feeling "stressed" and feeling "overwhelmed". We therefore combined the two items into a "stress/overload" index.
The primary outcome was the average level of stress/overload during the resuscitation period for the experimental and the control group. Secondary outcomes were three performance measures, two relating to medical performance and one relating to team coordination. The two medical performance measures were: (a) hands-on time defined as duration of uninterrupted chest compressions and defibrillation in the first 120 seconds after the onset of the cardiac arrest. Each defibrillation was rated as 10 seconds of hands-on time. Interruptions of chest compressions to perform ventilation were rated as continuous hands-on time if the interruption was < 10 sec; (b) the time elapsed until CPR was started, defined as the time to the first meaningful measure (either defibrillation, chest compression or ventilation) after the onset of the cardiac arrest; the team coordination measure (c) was the number of leadership statements coded, using a predefined checklist containing the following categories based on previous research: task assignment/task distribution, decision what to do, decision how to do, command. We also assessed the effectiveness of the instruction in the intervention group by investigating whether the two structuring questions were, indeed, asked aloud.
Using frame-in-frame technology, the teams' performance and the monitor displaying the "patient's" vital signs were simultaneously recorded. Data to assess CPR performance measures and leadership statements were assessed based on the video-tapes recorded during simulation. More precisely, CPR-related actions were coded second by second; communication was transcribed, and each statement was coded as outlined above.
Sample size calculations were based on assumptions from a previous observational study. A study sample of 49 participants per randomisation arm gave the study a power of 90% to detect a relative 20% decrease in perceived stress/overload levels (from 12 to 10) assuming a two-tailed test, a 5% level of significance, and a standard deviation of ±3 in both groups. Assuming that 20% of participants would not follow the protocol, we included a total of 124 participants.
Discrete variables are expressed as counts (percentage) and continuous variables as means and standard deviation (SD). Students T-test were used for between condition comparisons. We also calculated linear regression models to investigate the association of the intervention with the primary and secondary outcomes. For all analyses we calculated an intention-to-treat analysis including all randomised students, and a per-protocol analysis considering only students that followed the instructions in the intervention group. All tests were two-tailed and P values < 0.05 were considered to indicate statistical significance. All analyses were performed using STATA 9.2 (Stata Corp, College Station, TX).
Methods
Participants and Simulator
This study was conducted at the Simulator Center of the University Hospital in Basel, Switzerland, between December, 2007 and May, 2008. Workshops were offered to 4th year medical students and presented as a learning experience in a patient simulator. Prior to this simulation, no CPR training had been offered to the students within their medical curriculum. No information about the content of the scenarios and about our specific hypotheses was provided to students before the study (blinding).
The study was done in compliance with the Helsinki Declaration, approved by the local ethical committee (Ethikkommission beider Basel, EKBB, http://www.ekbb.ch/), and written informed consent was obtained from all participants.
For this study, we used a high fidelity manikin with the possibility of remote control of vital signs (Human Patient Simulator, METI). This full body simulator is a computer-based manikin with human physiology emulation capability that also can interact very realistically, e.g. by talking.
Study Design and Intervention
This is a prospective randomized controlled study. Prior to the test-scenario, all students were made familiar with the simulator in a baseline training session followed by a general video-assisted debriefing focusing on ACLS algorithms (Figure 1). Students were then randomly allocated to two different randomization arms using computer generated randomization lists. Students in the control group did not receive any further instructions. Students in the intervention group received a 10 minute instruction to cope with stress. They were informed that an emergency situation is a stressful experience for health care workers and that perceived stress may interfere with their decision-making abilities and performance. Particularly, feeling overwhelmed by stress may cause cognitive impairment potentially leading to loss of concept how to deal with an emergency situation, which in turn further increases stress (vicious cycle). However, it is possible to overcome this situation by focusing on the basic conditions of the situation and the immediate actions that are needed. They were instructed that they should ask two task-focusing questions aloud ("what is the patient's condition?", "what immediate action is needed?") to overcome the negative consequences of feeling overwhelmed by stress.
(Enlarge Image)
Figure 1.
Flow chart of randomisation groups. N denotes number of participants.
Test-scenario
The test-scenario was a simulated witnessed cardiac arrest. Students performed the test-scenario alone. They were supported by a nurse, blinded to the experimental condition, who was instructed to be active on request only and not provide any information concerning CPR algorithms. When students entered the simulator room, the patient was conscious and responded to the questions of the students. Two minutes after the medical student started to take the medical history, the patient fainted and the monitor displayed ventricular tachycardia.
Assessment of Stress Parameters
Upon completion of the simulation, perceived levels of stress and feeling overwhelmed were measured for different time points during the study period: (a) the baseline period immediately before resuscitation, (b) during the resuscitation period, (c) when the "patient" awakes, and d) during the debriefing period after the resuscitation. For each time point, we asked the students to quantify perceived levels of stress and feeling overwhelmed, measured on a Likert scale ranging from 1–20 (1 being lowest and 20 being highest). In a previous study, we found that perceived stress was best represented by a combination of these two items: feeling "stressed" and feeling "overwhelmed". We therefore combined the two items into a "stress/overload" index.
Outcomes and Measurements
The primary outcome was the average level of stress/overload during the resuscitation period for the experimental and the control group. Secondary outcomes were three performance measures, two relating to medical performance and one relating to team coordination. The two medical performance measures were: (a) hands-on time defined as duration of uninterrupted chest compressions and defibrillation in the first 120 seconds after the onset of the cardiac arrest. Each defibrillation was rated as 10 seconds of hands-on time. Interruptions of chest compressions to perform ventilation were rated as continuous hands-on time if the interruption was < 10 sec; (b) the time elapsed until CPR was started, defined as the time to the first meaningful measure (either defibrillation, chest compression or ventilation) after the onset of the cardiac arrest; the team coordination measure (c) was the number of leadership statements coded, using a predefined checklist containing the following categories based on previous research: task assignment/task distribution, decision what to do, decision how to do, command. We also assessed the effectiveness of the instruction in the intervention group by investigating whether the two structuring questions were, indeed, asked aloud.
Data Analysis
Using frame-in-frame technology, the teams' performance and the monitor displaying the "patient's" vital signs were simultaneously recorded. Data to assess CPR performance measures and leadership statements were assessed based on the video-tapes recorded during simulation. More precisely, CPR-related actions were coded second by second; communication was transcribed, and each statement was coded as outlined above.
Statistical Analysis
Sample size calculations were based on assumptions from a previous observational study. A study sample of 49 participants per randomisation arm gave the study a power of 90% to detect a relative 20% decrease in perceived stress/overload levels (from 12 to 10) assuming a two-tailed test, a 5% level of significance, and a standard deviation of ±3 in both groups. Assuming that 20% of participants would not follow the protocol, we included a total of 124 participants.
Discrete variables are expressed as counts (percentage) and continuous variables as means and standard deviation (SD). Students T-test were used for between condition comparisons. We also calculated linear regression models to investigate the association of the intervention with the primary and secondary outcomes. For all analyses we calculated an intention-to-treat analysis including all randomised students, and a per-protocol analysis considering only students that followed the instructions in the intervention group. All tests were two-tailed and P values < 0.05 were considered to indicate statistical significance. All analyses were performed using STATA 9.2 (Stata Corp, College Station, TX).
