Oxygenation Instability and Maturation of Control of Breathing in Premature Infants

Recordings of SpO2 and heart rate will be analyzed by dedicated software to obtain frequency, duration and severity of episodes of hypoxemia and hyperoxemia.

Recordings of SpO2, heart rate, esophageal pressure, tidal volume, minute volume, respiratory rate and transcutaneous PCO2 will be analyzed to determine the prevalence, severity and duration of hypoxemia episodes produced by the different mechanisms.

Recordings of tidal volume, minute volume and respiratory rate will be analyzed to determine frequency of apnea, periodic breathing, distribution of inter-breath intervals.

In mechanically ventilated infants the apneic threshold of CO2 will be measured by transcutaneous PCO2 following a step wise increase in ventilator rate until spontaneous breathing ceases transiently. In spontaneously breathing infants the apnea threshold of CO2 will be measured during episodes central apnea.

The Dejours test will be used to assess peripheral chemoreceptor function by measuring the immediate ventilatory response to high-inspired oxygen.

Central chemo-receptor function will be assessed by measuring the ventilatory response to inspired CO2.