The relationship between the flow rate delivered by nasal cannula and the fraction of inspired oxygen in newborn infants.

ABSTRACT

To determine the relationship between the oxygen flow rate delivered by nasal consular and the fraction of inspired oxygen (FiO2) and to evaluate if the nasal consular influenced the infant’s respiratory status, 46 newborn infants, half with a birth weight (BW) of more than 2 kg, were enrolled in this study. In this sample, 23 had a respiratory rate (RR) of more than 60 bum and the otter half had a RR of or less than 60 bum. Their mean age at the time of study was 12.5 days (SD = 15.9). Oxygen saturation (SaO2) was recorded by the Critic are 503 Pulse Ox meter and the FiO2 was measured by the Minion I Oxygen Analyzer. Each infant was first examined using the traditional techniques of oxygen delivery. The Silverman-Anderson retraction score was assigned and the respiratory rate was counted visually for one minute. Each infant was then evaluated in the same way with a nasal canella in place. Humidified oxygen was delivered at a flow rate con-trolled by a low-flow floweret which was adjusted until the SaO2 reading reached the exact value obtained by the traditional techniques. A significant positive correlation between the FiO2 and flow rate was found in both BW and RR categories. The correlation coefficients were 0.86 (p = 0.0000) and 0.70 (p = 0.002) in the larger and the smaller infants, respectively; and 0.77 (p = 0.0000) and 0.87 (p = 0.0000) in the higher and lower RR groups, respectively. The differences of the slopes between groups in both BW and RR categories were not statistically significant (P = 0.82 AND 0.92, respectively). The relationship of oxygen flow rate, birthright, and respiratory rate to the FiO2 examined by stepwise multiple regression analysis showed that the combination of these three independent variables explained 67% of the variation in the FiO2 (p = 0000). However, the regression coefficients suggested a statistically significant contribution of flow rate (p = 0.000), nut not BW or RR. The highest FiO2 delivered by nasal cannel was 0.81 There was a significant decrease in the mean RR from 64.0 to 61.2 bum when changing from traditional methods to nasal cannel (p = 0.029). The difference of the Silverman-Anderson retraction scores was not significant. The regression lines of the FiO2 on flow rates are provided.