261 OXYGEN THERAPY AND MATURATIONAL DIFFERENCES IN INFANTS WITH BRONCHIOLITIS

Abstract

Fifteen infants (3 wks to 8 mth) treated for bronchiolitis were monitored while in head-box oxygen (total of 840 hrs) with SaO2, pulse rate, activity, microphone, ECG heart rate, chest and abdominal excursion, were recorded to a computer aided display and analysis system (CARDAS). 8 were term and 7 were ex-preterm infants.Sleep disruption was marked. Term infants had tachypnea, range in quiet sleep (QS):49-71 [normal infants: 38-25 between 1 & 6 months]; obstruction (usually partial) with increased thoraco-abdominal phase angle (TAPA; Normals QS: 11±1; term bronchiolitis: 40±13; active sleep (AS): 130±19). Arousals periodically relieved progressive hypoxemia/hypoventilation. Ex-preterm infnats hypoventilated with progressive hypoxia. All had periodic breathing (PB) usually terminating the hypoventilation and increasing the SaO2. The PB cycle lengUi was 12-14 sec with < 10 sec apneas. 2 infants had periods of long central or mixed apnea (some > 30 sec); the fall in SaO2 from a “flat” 100% (hyperoxia) and bradycardia was delayed before arousal and onset of breathing occurred.1] The responses of ex-preterm infants are consistent with inhibitory mechanisms prevailing over excitatory ones from obstruction or airway irritation since they had minimal chest wall distortion and more apnea, apparently promoted by hyperoxia in some of them.2] Clinical staff were unaware of these events and were misled by intermittent SaO2 measurements, not recognising hyperoxia, apnea, or true from false hypoxemia. High dependency care was probably unnecessarily prolonged by relying on intermittent pulse oximetry.