Weaning and extubation readiness in pediatric patients

Abstract

Objective: A systematic review of weaning and extubation for pediatric patients on mechanical ventilation.

Data selection: Pediatric and adult literature, English language.

Study selection: Invited review.

Data sources: Literature review using National Library of Medicine PubMed from January 1972 until April 2008, earlier cross-referenced article citations, the Cochrane Database of Systematic Reviews, and the Internet.

Conclusions: Despite the importance of minimizing time on mechanical ventilation, only limited guidance on weaning and extubation is available from the pediatric literature. A significant proportion of patients being evaluated for weaning are actually ready for extubation, suggesting that weaning is often not considered early enough in the course of ventilation. Indications for extubation are even less clear, although a trial of spontaneous breathing would seem a prerequisite. Several indices have been developed in an attempt to predict weaning and extubation success but the available literature would suggest they offer no improvement over clinical judgment. Extubation failure rates range from 2% to 20% and bear little relationship to the duration of mechanical ventilation. Upper airway obstruction is the single most common cause of extubation failure. A reliable method of assessing readiness for weaning and predicting extubation success is not evident from the pediatric literature.

Figure 1

A schematic of the time and pressure courses of mechanical ventilation, along with the defined phases, in a PICU patient.

Figure 2

The failure rate of planned extubations of patients within the first 48 hours of arrival in the PICU is, on average, half that of the rate for patients ventilated for longer than 48 hours. This presents previously unpublished data from the 2003 report of Kurachek et al of extubation practices in 16 PICUs across the United States.

Figure 3

The rates of failed extubation in 16 PICUs across the United States along with their average number of days of mechanical ventilation. There are marked variations in the lengths of ventilation and also the failed extubation rates, with no relationship between the two, i.e. longer ventilation does not result in fewer failed extubations and vice versa. This presents previously unpublished data from the report of Kurachek et al.

Figure 4

The resistance of air flow through an endotracheal tube, modified from the work of Manczur et al. The various endotracheal sizes are identified by red lettering, representing the internal diameters of the tubes in millimeters. As flow rates (in liters/minute) are increased there is an increase in resistance, which becomes greater the smaller the internal diameter of the ETT. Thus, small diameter (i.e. pediatric) ETTS have become associated with high airflow resistances and the notion of “breathing through a straw” was (wrongly) conceived. Peak inspiratory flow rates are approximately 0.5 L/kg ideal body weight/min at all ages in humans. On the abscissa, the 3 arrows (from right) represent the peak flows for a 60 kg adult (intubated with a 6.5 – 8.5 mm ID ETT), a 10 kg child (using a 4 – 4.5 mm ID ETT) and a newborn infant.of 3 kg (with a 3 mm ID ETT), respectively. All resistances generated at these flows are well within normal limits and are, in fact, all less than 50 cmH₂O/L/s). Note, for simplicity of interpretation, the linear data for the 2.5 mm ID ETT have been extended into the lower flow range where it had not been measured by the authors of the original paper. (Modified from Manczur et al. with permission)

Figure 5

The Work of Breathing (as approximated using pressure-rate product by Willis et al.84) measured in 17 infants and young children under the various randomly applied conditions (from left to right) of: Pressure supported breaths (5cm H₂O), continuous positive airway pressure (4 cm H₂O), T-piece with oxygen, T-piece with Heliox, and postextubation. As demonstrated, the work of breathing rose slightly for each condition, but always remained low and was statistically significantly lower only for breaths supported with pressure support and CPAP. (Modified from Willis et al. with permission)