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Editor—In developing countries where resources are limited, oxygen is usually given straight into the incubator without blending, whereas in modern neonatal intensive care units nasal cannulas are more usual, as well as oxygen blenders and servo control systems.1 2
Oxygen concentrations were measured in four different models of incubators including Air Shields Isolette C2H2-1, ISIS Mediprema, Air Shields C100-200, and Air Shields Neocare 142 at oxygen flow rates of 1–15l/minute at Gazi University Hospital neonatal intensive care unit. Measurements were made using an SLE T-801oxygen monitor (Specialised Laboratory Equipment Ltd, UK) which was calibrated daily when there were no patients in the incubators. Oxygen flow rates, starting from 1 l/min up to 15 l/min were studied with 1 l/min increments after a stabilisation period of 15 minutes. For each flow rate, oxygen concentrations in the incubators were measured five to eight times, and mean values were taken. Unblended free flow oxygen was delivered into the incubator through the upper hole of the incubator. The sensor probe of the oxygen monitor was placed into the incubator through the side port and was left on the corner, at the level of the mattress, at the maximum distance from the oxygen tubing.
The lowest oxygen concentration at 1 l/min flow rate was 30% in Air Shields Neocare 142 and ISIS Mediprema, and the highest oxygen concentration was 87% at 15 l/min flow rate in Air Shields C100-200 incubators. The oxygen concentrations were above 40% at 4 l/min flow rate in all incubators.
Excess oxygen has well known adverse effects on tiny babies. The inspired oxygen concentration must be known, not only to help avoid retinopathy of prematurity,3 but also for the planning of decisions about the transmission of infants from incubator to crib. Our small study serves as a reminder to neonatal units that do not measure oxygen concentration that although the estimated oxygen concentration ranges for different flow rates are indicated on most incubators, these ranges are often too wide, making it difficult to fine tune the oxygen treatment.
Even with low flow rates of oxygen into incubators, the measured oxygen concentration may be higher than expected. Even in neonatal units with limited resources a simple oxygen concentration monitor for use in the incubator is a high priority purchase.
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