Weaning Infants from Mechanical Ventilation
Introduction
Mechanical ventilation (MV) is considered one of the major advances in neonatal medicine and is a widely used method of treatment, especially in the extremely preterm population. In a large cohort analysis of extremely low-birth-weight infants (ELBW) infants, 89% were treated with MV during the first day of life, and, almost 95% of survivors were invasively ventilated during their hospital stay.1 Recently, a multicenter randomized controlled trial (RCT) compared the use of noninvasive and invasive respiratory support immediately after birth and showed that 83% of the ELBW infants initially assigned to noninvasive support required endotracheal (ET) intubation and MV during hospitalization.2 In a large cohort of infants born at less than 28 weeks’ gestational age (GA), 74% were intubated and received surfactant therapy during their hospital stay.3 The Continuous Positive Airway Pressure or Intubation (COIN) trial included only infants between 25 and 28 weeks of GA with adequate respiratory efforts at birth. Nevertheless, 46% of the infants initially assigned to noninvasive support required ET intubation and MV.4 Thus, MV is a common therapy in neonatal intensive care units (NICUs), even in the current era of noninvasive respiratory support. Although MV offers essential support while the respiratory system recovers from acute failure and is necessary for survival, this therapy is associated with risks and complications, including mortality and neurodevelopmental impairments.1, 5 Therefore, when caring for extremely premature infants, clinicians should focus on weaning and removing MV as expeditiously as possible. Success of extubation is only 60% to 73% in ELBW infants.6, 7 Higher success rates (80%–86%) have been reported in some series that include all preterm infants.8, 9 Infants who fail and require reintubation, with its attendant risks, may experience deterioration of their respiratory status because of atelectasis. Episodes of hypoxemia or hypercapnia before reintubation may expose them to additional risks. Reintubation itself is unpleasant and may be traumatic and accompanied by bradycardia, hypercapnia, and alterations of cerebral blood flow and oxygenation.10, 11 On the other hand, many infants self-extubate and remain extubated subsequently.12 Those infants may therefore have been exposed to MV and potential ventilator-induced lung injury for longer than necessary. Protracted MV is not benign; in preterm baboons, 5 days of elective MV resulted in a greater degree of brain injury when compared with only 1 day.13 Using data from the National Institute of Child Health and Human Development Neonatal Research Network, Walsh and colleagues1 showed that each week of additional MV was associated with a significant increase in the likelihood of neurodevelopmental impairment. In addition, the ET tube (ETT) acts as a foreign body, quickly becoming colonized and acting as a portal of entry for pathogens, increasing the risk of ventilator-associated pneumonia and late-onset sepsis.14 Clearly, both premature extubation and unnecessarily prolonged MV are undesirable.
There is a striking paucity of good data to guide the clinician regarding optimal ways to wean respiratory support as well as to judge an infant's readiness for extubation. In this article, the available literature is summarized and reasonable evidence-based recommendations for expeditious weaning and extubation are formulated.
Section snippets
Reducing ventilator support
Weaning from MV is usually achieved by the gradual reduction of ventilatory support until the settings are judged to be low enough to remove support. Considerable controversy persists regarding the best ways to accomplish this goal, but some general evidence-based guidelines can be formulated.
Permissive Hypercapnia
Accepting higher levels of Paco2 during ventilation weaning to facilitate earlier extubation has been investigated extensively and is reviewed in detail elsewhere in this issue. Randomized clinical trials in preterm infants suggest that mild permissive hypercapnia is safe, but clinical benefits are modest.26 The safe limits of hypercapnia both during the first few days when the risk of intraventricular hemorrhage is highest and later on during the chronic phase of BPD have not been definitively
Extubation readiness
Failure of extubation is a common problem in extremely premature infants. Although neonatology has experienced major advances in MV and postextubation respiratory support, the science of determining if the patient is ready for extubation is still imprecise. Most preterm infants are easily extubated after a short period of MV but a few patients, for reasons such as respiratory muscle weakness, airway abnormalities, presence of a hemodynamically significant patent ductus arteriosus, immature
Predictors of extubation readiness
Over the past decades, several studies have investigated prediction tools that could help neonatologists determine extubation readiness in neonates with the highest chances of success. Several of these studies were performed before routine or widespread use of antenatal steroids and surfactant. Also, postextubation management was different from current practice, with infants being extubated to a headbox with humidified oxygen or room air.8, 57, 58, 59 More recently, other predictors have been
CPAP Versus Oxyhood or Nasal Cannula
The use of CPAP after extubation in preterm infants is superior to extubation to headbox or oxyhood.80 The physiologic basis for this finding is the inability of the immature rib cage of the ELBW infant to maintain adequate functional residual capacity because of its excessive compliance/insufficient rigidity. In addition, after being intubated for some time, the infant's vocal cords are edematous, preventing effective grunting; a mechanism the preterm infant normally uses to maintain internal
Summary
Weaning and extubation from MV remain an inexact science. Available evidence strongly suggests that early extubation is desirable, but our ability to predict the point at which this can be accomplished safely in ELBW infants remains limited. Volume-targeted ventilation may accelerate weaning from MV. There is a strong evidence base for using caffeine and distending airway pressure after extubation. Other adjuncts to weaning and extubation are less well established. Improved tools for predicting
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Disclosure: The authors have nothing to disclose.