A modified device for continuous non-invasive blood pressure measurements in humans under hyperbaric and/or oxygen-enriched conditions.

Background: It would be desirable to safely and continuously measure blood pressure noninvasively under hyperbaric and/or hyperoxic conditions, in order to explore haemodynamic responses in humans under these conditions.

Methods: A systematic analysis according to 'failure mode and effects analysis' principles of a commercially available beat-by-beat non-invasive blood pressure monitoring device was performed using specifications provided by the manufacturer. Possible failure modes related to pressure resistance and fire hazard in hyperbaric and oxygen-enriched environments were identified and the device modified accordingly to mitigate these risks. The modified device was compared to an unaltered device in five healthy volunteers under normobaric conditions. Measurements were then performed under hyperbaric conditions (243 kPa) in five healthy subjects.

Results: Modifications required included: 1) replacement of the carbon brush motorized pump by pressurized air connected through a balanced pressure valve; 2) modification of the 12V power supply connection in the multiplace hyperbaric chamber, and 3) replacement of gas-filled electrolytic capacitors by solid equivalents. There was concurrence between measurements under normobaric conditions, with no significant differences in blood pressure. Measurements under pressure were achieved without problems and matched intermittent measurement of brachial arterial pressure.

Conclusion: The modified system provides safe, stable, continuous non-invasive blood pressure trends under both normobaric and hyperbaric conditions.