Oxygen therapy is extensively used in premature infants and adults with respiratory insufficiency. In the premature infant the goal during manual control of the FIO2 is to maintain adequate oxygenation and to minimize the exposure to hypoxemia, hyperoxemia, and oxygen. However, this is frequently not achieved during routine care, which increases the risks of associated side effects affecting the eye, lungs, and central nervous system. In the adult the primary goal is to avoid hypoxemia, but conventional methods of oxygen supplementation may fall short during periods of increased demand. On the other hand, there are growing concerns related to unnecessarily high FIO2 levels that increase the exposure to hyperoxemia and excessive oxygen use in settings where resources are limited. Systems for automated closed loop control of FIO2 have been developed for use in neonates and adults. This paper will give an overview of the rationale for the development of these systems, present the evidence, and discuss important advantages and limitations.
The central excitatory amino acid (EAA) neurotransmitter glutamate has been shown to mediate the ventilatory response to hypoxia through N-methyl-D-aspartate (NMDA) receptors in anesthetized adult animals. To determine the role of the EAA glutamate in the neonatal ventilatory response to hypoxia, 19 unanesthetized chronically instrumented piglets were studied. Minute ventilation (VE), oxygen consumption (VO2), arterial blood pressure (ABP), heart rate (HR), and blood gases were measured in room air (RA) and after 1, 5, and 10 min of hypoxia (inspired oxygen fraction = 0.10) before and after an infusion of saline or CGS-19755, a competitive NMDA-receptor blocker (10 mg/kg i.v.). Nine control piglets [age 6 +/- 1 (SD) days; weight 2.02 +/- 0.40 kg] and 10 CGS-19755-treated animals (age 6 +/- 1 days; weight 1.90 +/- 0.66 kg) were studied during quiet sleep and in a thermoneutral environment. There was a marked decrease in the VE response to hypoxia after the administration of CGS-19755. The ventilatory response to hypoxia was not modified by saline infusion. Changes in ABP and arterial PO2 during hypoxia were similar between groups, whereas the decrease in arterial PCO2 was significantly less after CGS-19755 administration. The increase in HR with hypoxia was eliminated by the NMDA-receptor blocker administration. VO2 decreased with hypoxia in both groups, but this decrease was more marked after the NMDA-receptor blockade. These results suggest that the central EAA glutamate mediates, at least in part, the hypoxic hyperventilation in unanesthetized newborn piglets.
Caffeine is one of the most commonly prescribed drugs among premature infants. It is a potent respiratory stimulant indicated primarily to reduce the incidence of episodes of apnea associated with an immature central nervous system. It is also used frequently in these infants to facilitate weaning from mechanical ventilation. Despite the widespread use of caffeine for these indications, the evidence to support its use is based on the results of a few relatively small and short-term studies.1 Information is lacking on possible long-term effects of prolonged administration of caffeine on the development of the brain and other organs.In this . . .
