Can pulse-oximetry be used to record blood pressure in neonates accurately?

Blood pressure measurement is an important parameter in neonatal care. Oscillometric and intra-arterial methods are reported to be more accurate but due to various limitations they are not widely used. The present study involves BP measurement by analysing changes in plethysmogram of pulse-oximeter during slow inflation and deflation of BP cuffaroundipsilateral limb applied proximal to pulse-oximeter probe.

One hundred neonates were taken in this study after approval by ethical committee. A blood pressure cuff of appropriate size (connected to sphygmomanometer) was tied around the limb. Pulse-oximeter probe was applied in the finger/toe of same limb. When pulse-oximeter showed a smooth plethysmogram, cuff pressure was slowely raised and point of disappearance of plethysmogram was noted (DP). Pressure was further raised by 20 mm Hg quickly, and reduced slowly. The point where plethysmogram reappeared was noted (RP). Three readings were repeated at an interval of 5 minutes. Mean of DP and RP (MDR) was calculated. Simultaneously BP was taken by oscillometric method. The results were analysed statistically.

One hundred neonates of either sex (M-50, F-50), age (1–28 d), maturity (term 89, preterm 11), health status (sick 16, healthy 84), birth wt (950–3800 gm) were evaluated. Three hundred observations were taken by both methods. Correlation coefficients were calculated for each group. The r value for RP was o.89. The correlation with MDR was r = 0.87. Correlation coefficient for DP was r = 0.73. The mean pressures by different methods were -oscillometric 73.920, RP-71.880, DP-95.120 and MDR-83.460. In this study no significant difference was found between blood pressures by any of methods based on maturity, sex, health status and birth weight.

In our study based on 300 BP recordings in neonates, we found that systolic BP correlates better withpulse-oximetric blood pressure recordings taken at reappearance of plethysmogram while slowly deflating the BP cuff. This method of systolic blood pressure measurement is simple, accurate, non-invasive, reliable and cost effective. Hence, it is recommended for use in care of neonates where other reliable methods of BP recording are not available.