No abstract

Overnight 12 hour tape recordings of arterial oxygen saturation (SaO2, pulse oximeter in the beat to beat mode), breathing movements, and airflow were made on 66 preterm infants (median gestational age 34 weeks, range 25-36) who had reached term (37 weeks) and were ready for discharge from the special care baby unit. No infant was given additional inspired oxygen during the study. The median baseline SaO2 was 99-4% (range 88-9-100% In the present study, the same techniques have been applied to a group of preterm infants who were studied when they were ready for discharge from the special care baby unit and had reached at least 37 weeks' gestation. Two specific questions were asked: what is the influence of gestational age on the pattern of oxygenation, and (based on our study of term infants4) how does oxygenation differ between full term and preterm infants?Patients and methods Between August 1986 and July 1987 all preterm infants who were born at three maternity hospitals and who received special care immediately after birth had overnight tape recordings made of selected physiological variables. The study was carried out when infants were assessed as ready for discharge, and only on those who were considered to have a good prognosis for survival. A total of 305 infants fulfilled the criteria, and 261 (86%) had parental consent for the investigation. The project was approved by the hospitals' ethics committees. For the purpose of this study, all 72 infants with gestational ages of 37 weeks or more at the time of discharge, and who underwent their recordings within the three days before discharge, were included in the analysis.All 72 infants underwent 12 hour overnight recordings of arterial oxygen saturation (SaO2) (Nellcor N100 with new software equivalent to N200 and specially modified to provide beat to beat data); each photoplethysmographic pulse waveform from a pulse oximeter (for the validation of the saturation signals); breathing movements from a volume expansion capsule (Graseby) or from respiratory inductance plethysmography (Studley Data Systems); and nasal airflow either through a thermistor (Yellow Springs Instruments) or from expired carbon dioxide sampling (Engstrom Eliza). The recordings were stored on tape (Racal FM4) and subsequently printed onto graph paper by an ink jet recorder at 3-2 mm/second. As the study was prospective and non-invasive the recordings were not used for clinical management.Six recordings (8%) gave poor quality oxygen saturation signals throughout and were removed from the study. Of the remaining 66 recordings, 31 (47%) were done on the last day before discharge, 26 (39%) two days, and eight (12%)