This question was recently studied by a group from the UK. They compared noninvasive blood pressure (NIBP) with intra-arterial blood pressure measurements (IABP) at several points including pre-flight and in-flight. They did some complex statistics to study the levels of agreement between the two measurement methods.
This is something that is directly relevant to us at ARHT. While it doesn’t apply to all of our patients, we do transport a significant minority who are critically ill – where BP must be accurately measured.
The authors report, not surprisingly, that the NIBP was quite variable and often didn’t correlate well with the IABP both pre-flight and in-flight. But the take home point in their conclusion is that the non-invasive MAP is closer to the IABP. The authors conclude:
“From our results, IABP monitoring should be used in any unwell patient in whom accurate blood pressure measurement is desirable. The general inaccuracy of the NIBP measurements obtained dictate that IABP monitoring should remain the accepted ‘gold standard’ of care in any critical care environment. Notwithstanding this, in our study, the aeromedical transport environment does not lead to less precise NIBP results than the non-transport environment. Thus, we conclude, where NIBP measurement is the only option, that the mean blood pressure should be used in preference to systolic measurements”
*bold is my emphasis
Source McMahon N et al. Anesthesia 2012; 67:1343-1347. Comparison of non-invasive and invasive blood pressure in aeromedical care