An optical oscillometric method for neonatal and premature infant blood pressure monitoring

A preliminary study of a new optical oscillometric method to noninvasively measure systolic, mean, and diastolic blood pressures, in addition to heart and respiratory rates in very small extremities, is described. It employs transillumination of an extremity and measures the optical oscillation amplitude during cuff deflation from suprasystolic to zero pressure. The amplitude of the optical pulsatile oscillations is similar to that produced with the conventional pneumatic oscillometric method; however, the pulsatile optical signal is much larger and is present at all times when the cuff is deflated.

Two types of blood pressure verification studies were performed: (1) a weanling piglet study using a weanling piglet tail and (2) a human study using the little fingers of adult participants. For the weanling piglet study, direct femoral artery pressure, tail-cuff pressure, and optical oscillations were recorded in 5 anesthetized weanling piglets ranging in weight from 2 to 4 kg. Ten measurements were made in the pressure range of 30 to 175 mm Hg. For human study, data were obtained from 23 adult participants of both sexes with a little finger circumference of 4 cm or less. Radial artery pressure, measured with the conventional pneumatic oscillometric method, was used as the standard and was compared with the simultaneous optical oscillometric pressure in the little finger of the opposite arm.

This is an initial study demonstrating the optical oscillometric technique as a viable alternative for noninvasive blood pressure measurement in low birth-weight infants.

The weanling piglet data show a high correlation between direct arterial pressure and this new optical oscillometric method over a pressure range of approximately 30 to 175 mm Hg. The correlation coefficients of linear regression were 0.93, 0.93, and 0.91, respectively. The human little finger data show a high correlation between the pneumatic oscillometric mean arterial pressure and this new optical oscillometric method over a pressure range of approximately 40 to 140 mm Hg. The correlation coefficient of linear regression was 0.87.

This new optical oscillometric technique simplifies noninvasive blood pressure measurement because it was designed specifically for small-diameter extremities such as those found in low birth-weight infants. This new optical oscillometric device has the added benefit of continually monitoring pulse and respiration rates.