Effect of baseline oxygenation on the ventilatory response to inhaled 100% oxygen in preterm infants

Abstract

We tested the hypothesis that the immediate (< 1 min) ventilatory response to 100% O2 in preterm infants, a test of peripheral chemoreceptor activity characterized by a decrease in ventilation due to apnea, is more pronounced at lower baseline O2 concentrations. We studied 12 healthy preterm infants [birth weight 1,425 +/- 103 (SE) g; study weight 1,670 +/- 93 g; gestational age 30 +/- 1 wk; postnatal age 27 +/- 7 days] during quiet sleep. The infants inhaled 15, 21, 25, 30, 35, 40, and 45% O2 for 5 min in a randomized manner (control period), followed by 100% O2 for 2 min, and then the same initial O2 concentration again for 2 min (recovery period). A nose piece and a flow-through system were used to measure ventilation. The immediate decrease in ventilation with 100% O2 was 46% on 15% O2, 24% on 21% O2, 11% on 25% O2, 8% on 30% O2, 12% on 35% O2, and 8% on 40% O2; there was no decrease on 45% O2 (P < 0.01). The corresponding mean duration of apnea was 29 s during 15% O2, 18 s during 21% O2, 8 s during 25% O2, 9 s during 30 and 35% O2, and 3 s during 40% O2; only one infant developed a 5-s apnea during 45% O2 (P < 0.001). The findings suggest that 1) the ventilatory decrease in response to 100% O2 is dependent on the baseline oxygenation, being more pronounced the lower the baseline O2 concentration; and 2) this ventilatory decrease is entirely related to more prolonged apneas observed with lower baseline O2 concentrations. We speculate that the peripheral chemoreceptors, being so active in the small preterm infant with relatively low arterial PO2, are highly susceptible to changes in PO2, and this makes them prone to irregular or periodic breathing, especially during sleep.

Fetal acidosis and hypotension during repeated umbilical cord occlusions are associated with enhanced chemoreflex responses in near-term fetal sheep

“…Furthermore, we found a significant correlation in this group between the rate of initial fall of the FHR and the severity of evolving hypotension during the episodes of umbilical cord occlusion. These findings are consistent with data indicating that preexisting hypoxemia increases peripheral arterial chemoreceptor activity in several settings (7,11,17) and strongly suggest that attenuation of the chemoreflex only occurs in response to episodes of relatively mild hypoxia (14,15).…”

Paradoxical effect of oxygen administration on breathing stability following post‐hyperventilation apnoea in lambs

“…It has been suggested that the PB seen in premature infants may be of the episodic or cluster variety (Webber & Speck, 1981). Certainly, published recordings of PB in premature infants (Rigatto & Brady, 1972; Miller & DiFiore, 1995; Haider et al 1995) show an abrupt onset of breathing with little change in tidal volume before apnoea develops; this is similar to the episodic breathing pattern illustrated in Fig. 4.…”

Effect of Supplemental Oxygen on Sleep Architecture and Cardiorespiratory Events in Preterm Infants

“…Indeed, preterm infants with lower baseline oxyhemoglobin saturations are more prone to have apnea and periodic breathing. 18 Furthermore, exposure to an hypoxic gas mixture may lead to prolonged or recurrent apnea in infants. 19 Conversely, decreases in apnea density and periodic breathing ensued after inhalation of 100%.…”