Evaluation of consistency and correlation between non-invasive and invasive blood pressure monitoring among critically illed patients

Abstract:

Objective：To evaluate the consistency and correlation between invasive blood pressure（IBP） and non-invasive blood pressure（NIBP） in critically illed patients. Methods：Five hundred critically illed patients in department of critical care medicine in General Hospital of NingXia Medical University from March 2010 to March 2012 were randomly enrolled. Right radial artery IBP monitoring and bilateral brachial artery NIBP monitoring were conducted synchronistically. According to IBP level，patients were divided into three groups：group A，systolic blood pressure（SBP）< 90 mmHg，n=116；group B，SBP 90-140 mmHg，n=172；group C，SBP≥140 mmHg，n=212. Methods of correlation coefficient and Bland-Altman analysis were employed to assess the correlation and consistency of NIBP and IBP. Results：（１）Consistency analysis showed that the average difference levels for invasive SBP and non-invasive SBP in group A were accordingly -2.9 mmHg（left brachial artery） and -5.6 mmHg（right brachial artery），in group B（4.5 mmHg and 1.9 mmHg），in group C（20 mmHg and 17.3 mmHg），respectively. Incidences beyond the consistency zone of upper and lower limit in group A were 0.0%，3.4%（left brachial artery） and 0.0%，4.3%（right brachial artery），in group B（1.7%，3.5% and 1.7%，2.3%），in group C（2.0%，0.0% and 2.0%，0.0%），respectively. （２）Consistency analysis showed that average difference levels for invasive diastolic blood pressure（DBP） and non-invasive DBP in group A were accordingly -3.5 mmHg（left brachial artery） and -5.8 mmHg（right brachial artery），in group B（-3.2 mmHg and -3.5 mmHg），in group C（0.3 mmHg and 1.2 mmHg），respectively. Incidences beyond the consistency zone of upper and lower limit in group B were 6.0%，1.7%（left brachial artery） and 3.4%，2.6%（right brachial artery），in group B（1.2%，2.9% and 1.7%，3.5%），in group C（2.4%，4.2% and 3.3%，2.8%），respectively. ③Correlation coefficients between invasive and non-invasive SBP of three groups were accordingly 0.105-0.108（group A），0.417-0.444（group B） and 0.144-0.166（group C）. As to DBP，they were 0.409-0.427（group A），0.598-0.617（group B） and 0.546-0.596（group C）. Conclusions：During hypotension and hypertension in critically illed patients，consistency between IBP and NIBP is obviously decreased. NIBP monitoring tends to overestimate or underestimate patient’s real blood pressure.