Changes in cardiac output during air ambulance repatriation.

OBJECTIVES: To measure, with the use of suprasternal Doppler ultrasound, the hemodynamic changes in patients and volunteers during air ambulance repatriation.
DESIGN: Unblinded prospective observational study.
SETTING: Chartered air ambulances for the international repatriation of patients. PATIENTS AND PARTICIPANTS: Six medical crew members and seven patients transported back to hospitals in the UK.
INTERVENTIONS: The measurement of non-invasive blood pressure, ECG, heart rate, oxygen saturation and hemodynamic variables with suprasternal Doppler. MEASUREMENTS AND
RESULTS: There was a drop in systolic and mean arterial blood pressure in the patient's group once in the air. Oxygen saturation dropped in both groups once at cruising altitude. Heart rate remained unchanged. Stroke distance and minute distance increased significantly in the patient's group and non-significantly in the volunteers. Peak velocity increased significantly in the patient's group. There was an overall reduction of systemic vascular resistance during take off and once at cruising altitude.
CONCLUSIONS: Hemodynamic changes happen during air ambulance transportation in fit and healthy volunteers and patients alike. These may be due to a combination of hypobaric hypoxia and gravitational forces. It is necessary to establish if these changes have short- or long-term effects in the critically ill.