MEASUREMENT OF SYSTOLIC BLOOD-PRESSURE USING PULSE OXIMETRY DURING HELICOPTER FLIGHT

Objective: Monitoring of vital signs in critically ill patients during helicopter flight is difficult because of the noise and vibrations of the aircraft. We evaluated the use of a pulse oximeter to measure systolic BP intraflight. Design: Systolic BP measured by pulse oximetry was compared with systolic BP measured by the direct intra-arterial and the arterial occulsion methods intraflight. Systolic BP by pulse oximetry was measured by observing the return of the plethysmographic waveform of the pulse oximeter as the BP cuff ipsilateral to the pulse oximeter probe was slowly deflated. Arterial occlusion pressure was measured by observing the return of the intra-arterial waveform as the BP cuff ipsilateral to the arterial cannula was slowly deflated. Setting: The study was performed during patient transport, intraflight. Patients: Ten critically ill patients were studied. Interventions: None. Measurements and Main Results: Seventy-three sets of measurements were recorded. The best correlation (r2 = .99) was found between pulse oximetry and the arterial occlusion method. The indirect methods correlated better with each other than with direct intra-arterial measurements. The noise and the vibrations of the helicopter did not significantly interfere with the operation of the pulse oximeter. Conclusions: We conclude that a pulse oximeter that displays a plethysmographic waveform can accurately measure systolic BP intraflight.