Closed-Loop Controlled Inspired Oxygen Concentration for Mechanically Ventilated Very Low Birth Weight Infants With Frequent Episodes of Hypoxemia

Background. Mechanically ventilated very low birth weight infants often present with frequent episodes of hypoxemia, and maintaining arterial oxygen saturation by pulse oximetry (Spo₂) within a normal range by manual fraction of inspired oxygen (Fio₂) adjustments is difficult and time consuming.

Objectives. An algorithm for closed-loop Fio₂ control (cFio₂) to maintain Spo₂ within a target range was compared with continuous manual Fio₂(mFio₂) adjustments by a nurse in a group of ventilated infants who presented with frequent episodes of hypoxemia.

Results. Fourteen infants (birth weight: 712 ± 142 g; gestational age: 25 ± 1.6 weeks; age: 26 ± 11 days; synchronized intermittent mandatory ventilation rate: 24 ± 10 b/m; peak inspiratory pressure: 17.5 ± 2.0 cmH₂O; positive end-expiratory pressure: 4.3 ± 0.5 cmH₂O) were studied for 2 hours on each mode in random sequence. Both modes aimed to maintain Spo₂ between 88% and 96%.

There were 15 ± 7 and 16 ± 6 hypoxemic episodes/hour (Spo₂ <88%, >5 s) during mFio₂ and cFio₂, respectively; episode duration was 41 ± 23 and 32 ± 15 s, totaling 19 ± 16% and 17 ± 12% of recording time. There were 13 ± 10 and 10 ± 8 hyperoxemic episodes/hour (Spo₂>96%, >5 s) during mFio₂ and cFio_2,respectively; episode duration was 27 ± 15 and 24 ± 19 s, totaling 15 ± 14% and 10 ± 9% of recording time. Mean Spo₂ and Fio₂ levels were similar during both modes. The nurse made 29 ± 17 adjustments/hour during mFio₂. There was a significant increase in the duration of normoxemia (Spo₂ between 88%–96%) during cFio₂ (75 ± 13 vs 66 ± 14% of recording time).

Conclusion. In this group of infants, cFio₂ was at least as effective as a fully dedicated nurse in maintaining Spo₂ within the target range, and it may be more effective than a nurse working under routine conditions. We speculate that during long-term use, cFio₂ may save nursing time and reduce the risks of morbidity associated with supplemental oxygen and episodes of hypo- and hyperoxemia.