Evaluation of the severity of chronic lung disease in premature infants by pulse oximeter

Abstract

Three parameters obtained by pulse oximeter were tested to assess the severity of chronic lung disease (CLD) in premature infants. The FiO2 required to keep oxygen saturation of 90% on pulse oximeter at rest condition was defined as FiO2Sp90. The value of oxygen saturation with a FiO2 of 0.21 at rest was defined as room air saturation. The percentage of the time duration that oxygen saturation exceeded 90% during the measurement with the FiO2Sp90 was defined as time-percentage of SpO2 > or = 90% with FiO2Sp90. These parameters were monitored for 60 minutes once weekly in very low birth weight infants for at least 4 weeks beginning at 34 weeks of postconceptional age. Thirty-four infants were enrolled; 13 of them had CLD. There were totally 57 measurements in 13 infants with CLD, and 84 measurements in 21 infants with no CLD. Values of each parameter significantly correlated with the FiO2 used during the measurement; the FiO2Sp90 had positive correlation with FiO2 (r = 0.991, p < 0.001), the room air saturation and time percentage of SpO2 > 90% with FiO2Sp90 had negative correlation (r = -0.975, p < 0.001 and r = -0.668, p < 0.05, respectively). In the serial measurements, room air saturation improved even after the FiO2Sp90 reached 0.21. Time-percentage of SpO2 > or = 90% with FiO2Sp90 showed increase with age even after the room air saturation reached over 90%. Therefore, room air saturation was more sensitive than FiO2Sp90, and the time-percentage of SpO2 > or = 90% with FiO2Sp90 was more sensitive than room air saturation in estimating the severity of CLD. For clinical use, FiO2Sp90 may be used as a guide for oxygen concentration required. Room air saturation may offer a criterion in deciding the need of further oxygen therapy, and time-percentage of Sp02 > or = 90% with FiO2Sp90 could be used to follow up the improvement of lung function, even after the oxygen therapy was discontinued.