There is very few data in the literature comparing term and preterm infants regarding the response to 100% oxygen. It is well known that newborn infants and adults have a similar peripheral chemoreceptor response to hyperoxia. It is also known that preterm infants also decrease ventilation after administration of high oxygen concentrations and the response is similar in quiet and rem sleep. In this study, we report marked differences in the ventilatory response of term and preterm infants to 100% oxygem observed during measurements of FRC with the N2 washout technique. We analysed the ventilatory response to 100% oxygen in 10 fullterm (39 ± 1.2 weeks) and 10 preterm infants (35 ± 1.5 weeks). All infants were breathing room air and none of the preterm infants had been previously exposed to more than 24 hs of oxygen. Studies were performed with the infants in quiet sleep and no sedation. Air flow was measured with a face mask and a pneumotach before and during exposure to 100% oxygen during a 2 minute nitrogen washout. Data was digitized in computer and stored for further analysis. We analysed changes in ventilatory parameters (Vt, Ti, Ve and f) before and during the oxygen exposure. Mean birth weight was 2970 ± 150 g for the term and 1570± 210 g for the preterm infants. We measured ventilation second by second and report here the mean data for the first 10 seconds after oxygen exposure. Our data is shown on the table below: All infants showed an imediate decrease in tidal volume and frequency. The response was much more marked in the preterm infants. Mean% change in VE was 18% for the term and 37% for the preterm. Our data show that peripheral chemoreceptor response is exarcerbated in healthy preterms compared to fullterms infants. It implies that a maturation in the respiratory control of breathing must occur until term.(CNPq)
