Ratings of blood pressure Monitors
Blood pressure measurement using pulse oximeter waveform change was compared with an oscillometric measurement and the gold standard, intra-arterial measurement, in children after cardiac surgery. Forty six patients were enrolled and divided into groups according to weight. Simultaneous blood pressure measurements were obtained from the arterial catheter, the oscillometric device, and the pulse oximeter. Pulse oximeter measurements were obtained with a blood pressure cuff proximal to the oximeter probe. The blood pressure measurements from the pulse oximeter method correlated better with intra-arterial measurements than those from the oscillometric device (0.77–0.96 0.42–0.83). The absolute differences between the pulse oximeter and intra-arterial measurements were significantly smaller than between the oscillometric and intra-arterial measurements in children less than 15.0 kg. The pulse oximeter waveform change is an accurate and reliable way to measure blood pressure in children non-invasively, and is superior to the oscillometric method for small patients.
Automated oscillometric measurement of blood pressure has been the standard of care for non-invasive blood pressure assessment in children since the early 1980s. These devices transmit the pressure oscillations generated by arterial pulsation to a blood pressure cuff. The oscillations are then measured by a transducer and fed into a microprocessor. Oscillometric measurements have been shown repeatedly to correlate well with the gold standard of intra-arterial measurements, but the absolute accuracy of the measurements has been problematical. The 95% confidence interval for absolute accuracy has been shown repeatedly to exceed 15 mm Hg.
Studies have also indicated that oscillometric measurements become less accurate when blood pressure is low, especially if mean arterial pressure is less than 40 mm Hg. Nevertheless, it has remained the preferred method for non-invasive blood pressure measurement because other options such as palpation, auscultation, and Doppler are either even less accurate or are technically difficult to undertake in children.