Comparison of non-invasive and invasive blood pressure in aeromedical care

Authors

  • N. McMahon,

    1.  Consultant, Emergency Medical Retrieval Service, Glasgow, UK
    2.  Consultant, Emergency Department, Royal Alexandra Hospital, Paisley, UK
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  • L. A. Hogg,

    1.  Consultant, Emergency Medical Retrieval Service, Glasgow, UK
    2.  Consultant, Anaesthetic Department, New Royal Infirmary of Edinburgh, Edinburgh, UK
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  • A. R. Corfield,

    1.  Consultant, Emergency Medical Retrieval Service, Glasgow, UK
    2.  Consultant, Emergency Department, Royal Alexandra Hospital, Paisley, UK
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  • A. D. Exton

    1.  Consultant, Emergency Medical Retrieval Service, Glasgow, UK
    2.  Consultant, Emergency Department, Royal Alexandra Hospital, Paisley, UK
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Correspondence to: A. R. Corfield
Email: a.corfield@nhs.net

Summary

Blood pressure measurement is an essential physiological measurement for all critically ill patients. Previous work has shown that non-invasive blood pressure is not an accurate reflection of invasive blood pressure measurement. In a transport environment, the effects of motion and vibration may make non-invasive blood pressure less accurate. Consecutive critically ill patients transported by a dedicated aeromedical retrieval and critical care transfer service with simultaneous invasive and non-invasive blood pressure measurements were analysed. Two sets of measurements were recorded, first in a hospital environment before departure (pre-flight) and a second during aeromedical transport (in-flight). A total of 56 complete sets of data were analysed. Bland-Altman plots showed limits of agreement (precision) for pre-flight systolic blood pressure were −37.3 mmHg to 30.0 mmHg, and for pre-flight mean arterial pressure −20.5 mmHg to 25.0 mmHg. The limits of agreement for in-flight systolic blood pressure were −40.6 mmHg to 33.1 mmHg, while those for in-flight mean blood pressure in-flight were −23.6 mmHg to 24.6 mmHg. The bias for the four conditions ranged from 0.5 to −3.8 mmHg. There were no significant differences in values between pre-flight and in-flight blood pressure measurements for all categories of blood pressure measurement. Thus, our data show that non-invasive blood pressure is not a precise reflection of invasive intra-arterial blood pressure. Mean blood pressure measured non-invasively may be a better marker of invasive blood pressure than systolic blood pressure. Our data show no evidence of non-invasive blood pressures being less accurate in an aeromedical transport environment.

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