Objective. Oxygen delivery through nasal cannulae to convalescent preterm infants is a common but largely unstudied practice. To learn more about current nasal cannula oxygen delivery practices, we examined the variations in oxygen delivery through nasal cannulae among the centers of the Neonatal Research Network, the frequency of prescription of low levels of oxygen, and the success of weaning to room air. We hypothesized that some infants treated with oxygen through nasal cannulae were receiving oxygen levels equivalent to those of room air.

Methods. This was a descriptive, nested, cohort study of nasal cannula oxygen prescription among 187 infants with birth weights of <1250 g. All infants were studied at a postmenstrual age of 36 weeks, with a timed oxygen reduction challenge to establish their ability to be weaned to room air. The results of this challenge were compared with the fraction of inspired oxygen (Fio2) delivered, calculated as effective Fio2. Infants who maintained oxygen saturation values of ≥90% during oxygen weaning and during a 30-minute period in room air were defined as passing the challenge.

Results. Fifty-two infants (27.8%) were receiving oxygen concentrations and flow rates through nasal cannulae that delivered an effective Fio2 of <0.23, of whom 16 were receiving oxygen concentrations and flow rates that delivered an effective Fio2 of 0.21. In addition, 22 infants (11.8%) were prescribed room air through nasal cannulae intentionally. Seventy-two percent of those prescribed an effective Fio2 of <0.23 passed the room air challenge.

Conclusions. Prescription of oxygen with combinations of flow rates and oxygen concentrations that delivered a low effective Fio2 was common. We speculate that some of this, including the inadvertent prescription of an effective Fio2 equivalent to that of room air, is related to lack of knowledge of the effective Fio2. Routine calculation of effective Fio2 values may prompt earlier trials of room air and thus reduce unnecessary days of oxygen therapy.

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