Preterm infants often experience hyperoxia while receiving supplemental oxygen. Prolonged exposure to hyperoxia during development is associated with pathologies such as bronchopulmonary dysplasia and retinopathy of prematurity. Over the last 25 years, however, experiments with animal models have revealed that moderate exposures to hyperoxia (e.g., 30–60% O2 for days to weeks) can also have profound effects on the developing respiratory control system that may lead to hypoventilation and diminished responses to acute hypoxia. This plasticity, which is generally inducible only during critical periods of development, has a complex time course that includes both transient and permanent respiratory deficits. Although the molecular mechanisms of hyperoxia-induced plasticity are only beginning to be elucidated, it is clear that many of the respiratory effects are linked to abnormal morphological and functional development of the carotid body, the principal site of arterial O2 chemoreception for respiratory control. Specifically, developmental hyperoxia reduces carotid body size, decreases the number of chemoafferent neurons, and (at least transiently) diminishes the O2 sensitivity of individual carotid body glomus cells. Recent evidence suggests that hyperoxia may also directly or indirectly impact development of central neural control of breathing. Collectively, these findings emphasize the vulnerability of the developing respiratory control system to environmental perturbations.

Newborn rats chronically exposed to moderate hyperoxia (60% O2) exhibit abnormal respiratory control, including decreased eupneic ventilation. To further characterize this plasticity and explore its proximate mechanisms, rats were exposed to either 21% O2 (Control) or 60% O2 (Hyperoxia) from birth until studied at 3 – 14 days of age (P3 – P14). Normoxic ventilation was reduced in Hyperoxia rats when studied at P3, P4, and P6-7 and this was reflected in diminished arterial O2 saturations; eupneic ventilation spontaneously recovered by P13-14 despite continuous hyperoxia, or within 24 h when Hyperoxia rats were returned to room air. Normoxic metabolism was also reduced in Hyperoxia rats but could be increased by raising inspired O2 levels (to 60% O2) or by uncoupling oxidative phosphorylation within the mitochondrion (2, 4-dinitrophenol). In contrast, moderate increases in inspired O2 had no effect on sustained ventilation which indicates that hypoventilation can be dissociated from hypometabolism. The ventilatory response to abrupt O2 inhalation was diminished in Hyperoxia rats at P4 and P6-7, consistent with smaller contributions of peripheral chemoreceptors to eupneic ventilation at these ages. Finally, the spontaneous respiratory rhythm generated in isolated brainstem-spinal cord preparations was significantly slower and more variable in P3-4 Hyperoxia rats than in age-matched Controls. We conclude that developmental hyperoxia impairs both peripheral and central components of eupneic ventilatory drive. Although developmental hyperoxia diminishes metabolism as well, this appears to be a regulated hypometabolism and contributes little to the observed changes in ventilation.

Background: Successful combined Laparoscopic cholecystectomy and endoscopic retrograde cholangiopancreatography (ERCP) in the Same Session (LESS) has been reported in several studies in adult patients with choledocholithiasis. Methods: This was a retrospective analysis of data collected prospectively in the Pediatric ERCP Database Initiative using REDCAP. Adverse events were recorded separately and were reviewed for this study. The primary outcome was the hospitalization days. Secondary outcomes included total duration of anesthesia, morbidity, time from diagnosis to procedure. Results: Twenty-five patients underwent LESS, and 42 underwent the traditional ERCP followed by laparoscopic cholecystectomy. The groups were similar in age, weight, ASA. The median length of stay in the LESS group was 3 days, compared with 4 days (P = .32). Total procedure time was similar between the 2 groups, but anesthesia time was shorter in the LESS group (P = .0401). Morbidity was similarly low between the 2 groups. Conclusions: Relative to 2 interventions, a single session combining ERCP and laparoscopic cholecystectomy in pediatric patients is effective with a similar adverse event rate and length of stay. The use of a single sedation and reduced total anesthesia time are potential benefits of this approach. This modality may be considered for pediatric patients with choledocholithiasis with or without hemolytic disease.

Chronic exposure to sustained hyperoxia alters the development of the respiratory control system, but the respiratory effects of chronic intermittent hyperoxia have rarely been investigated. We exposed newborn rats to short, repeated bouts of 30% O2 or 60% O2 (5 bouts h−1) for 4–15 days and then assessed their hypoxic ventilatory response (HVR; 10 min at 12% O2) by plethysmography. The HVR tended to be enhanced by intermittent hyperoxia at P4 (early phase of the HVR), but it was significantly reduced at P14-15 (primarily late phase of the HVR) compared to age-matched controls; the HVR recovered when individuals were returned to room air and re-studied as adults. To investigate the role of carotid body function in this plasticity, single-unit carotid chemoafferent activity was recorded in vitro. Intermittent hyperoxia tended to decrease spontaneous action potential frequency under normoxic conditions but, contrary to expectations, hypoxic responses were only reduced at P4 (not at P14) and only in rats exposed to higher O2 levels (i.e., intermittent 60% O2). Rats exposed to intermittent hyperoxia had smaller carotid bodies, and this morphological change may contribute to the blunted HVR. In contrast to rats exposed to intermittent hyperoxia beginning at birth, two weeks of intermittent 60% O2 had no effect on the HVR or carotid body size of rats exposed beginning at P28; therefore, intermittent hyperoxia-induced respiratory plasticity appears to be unique to development. Although both intermittent and sustained hyperoxia alter carotid body development and the HVR of rats, the specific effects and time course of this plasticity differs.

Under hypoxic conditions, the ventilatory response to the Wingate test is perhaps more important than aerobic capacity per se in determining whether or not Wingate performance is decremented.