A PRACTICAL AND RELIABLE METHOD OF MEASURING BLOOD-PRESSURE IN THE NEONATE BY PULSE OXIMETRY

Objective: We investigated the reliability of the plethysmographic wav eform of the pulse oximeter to measure systolic blood pressure in sick neonates. Methods: Fifty infants admitted to the neonatal intensive c are unit, with indwelling arterial catheters placed for their ongoing care, were enrolled. Median gestational age was 31 weeks (range, 24 to 40 weeks), and the mean birth weight was 1711 gm (range, 546 to 3856 gm). Blood pressure was recorded by an oscillometric method as well as from a transducer connected to an arterial catheter. Additionally, pu lse oximeter blood pressures were obtained by gradually inflating an a ppropriately sized blood pressure cuff in increments of 2 to 5 mm Hg, on the same extremity as the oximeter probe, until the waveform just d isappeared. The cuff was then rapidly inflated another 20 mm Hg and th en gradually deflated in increments of 2 to 5 mm Hg until the waveform reappeared on the oximeter screen display. The pulse oximeter blood p ressures were calculated both as the blood pressure noted at disappear ance of the pulse oximeter waveform and as the blood pressure noted by the average purse oximeter blood pressure at the disappearance and re appearance of the waveform. The mean intraarterial systolic blood pres sure was 54 mm Hg (range, 36 to 82 mm Hg). Results: Blood pressures ob tained by pulse oximetry showed a significantly better correlation wit h intraarterial measurements in comparison with those obtained by osci llometric instruments. Additionally, the limits of agreement (mean dif ference +/-2 SD) between blood pressures obtained by intraarterial mea surements and those obtained by pulse oximetry were within a clinicall y acceptable range as opposed to those obtained by the comparison of i ntraarterial and oscillometric methods. Conclusion: Measurements of bl ood pressure in the neonate by means of pulse oximetery waveform analy sis are easily obtainable and more accurate than those obtained by the oscillometric method.