With the aim of reducing the duration of invasive respiratory support, neonatologists should consider a shorter process of discontinuing mechanical ventilation as well as an earlier appreciation of readiness for spontaneous breathing trials. Actually, both premature and delayed extubation can cause severe harm, thus de ning the precise moment for extubation could be very challenging in some patients. A delayed extubation may further increase the inherent risk of MV and ETT complications. On the other hand, premature MV discontinuation may imply a set of different problems, including dif culty in re-establishing arti cial airways, compromised gas exchange and hemodynamic destabilization. Therefore, a weaning process which is both expeditious and safe is highly desirable. Most infants are easily extubated after a short period of MV. However, in some patients weaning may be much more dif cult and prolonged, sometimes being complicated by one or more episodes of extubation failure. This could be due to a number of causes, including iatrogenic airway injuries, congenital airway abnormalities, respiratory muscle weakness, underlying cardiac abnormalities, recurrent apnoeic episodes, or acquired infections, among others. The prevalence of extubation failure in newborns may quite vary, ranging from 10 to 80% [8]. This large variability depends upon several factor
Patient readiness to be successfully extubated is usually based upon both clinical and objective tests. Yet, not a single index has been deemed as suf ciently sensitive and speci c so far [25]. Ideally, simple measurements should be available to clinicians to best predict which newborns are ready for a spontaneous-breathing trial (SBT) and in which patients these trials are most likely to be successful.
The aim of spontaneous breathing trials is to assess an infant’s ability to breathe while receiving minimal or no respiratory support. To achieve this, full respiratory support modes such as volume- assist control or pressure control are switched to ventilatory modes such as pressure support, continuous positive airway pressure, or ventilation with a T-piece. The latter is characterized by a complete absence of positive end expiratory pressure, thus giving the patient the lowest amount of support possible. During SBT an integrated assessment of different criteria are usually checked, including respiratory pattern and rate, gas exchange parameters, hemodynamic stability, mental status, comfort and diaphoresis. In most circumstances, SBT should be considered only if the patient is awake or not receiving excessive sedation.
In the last two decades, a variety of tests have been evaluated to improve the ability to predict a successful extubation in preterm newborns, including spontaneous minute ventilation, various spontaneous breathing tests and pulmonary function testing. In fact, none of these predictors were found to be consistently reliable [26-29].
In a small randomized clinical trial, Gillespie et al. assessed infants’ readiness for extubation by using the minute ventilation test (MVT) [30]. The MVT test evaluates the effectiveness of spontaneous breathing and respiratory muscle endurance, by processing data obtained with a relatively simple pulmonary monitoring system, routinely available in any ventilator nowadays. In 42 preterm infants with respiratory distress syndrome, a signi cant reduction in time from randomization to extubation was observed in those evaluated by the MVT, when compared to clinical assessment only (mean time of 8 hours versus 36 hours, respectively) [30].
In a pilot study performed in Australia, Kamlin et al. evaluated a very short SBT (three minutes of spontaneous breathing during ETT continuous positive airway pressure before extubation) to predict the extubation readiness of 50 VLBW infants [27]. During such test, investigators were simply observing changes in heart rate and oxygen saturation, for three minutes, reporting very promising results in terms of positive and negative predictive values, speci city and sensitivity. SBT was then adopted as a standard of care in their Unit [27]. Subsequently, in a large prospective study, Kamlin and colleagues demonstrated that after using the 3-min SBT in their current practice, preterm infants were extubated earlier and at higher ventilatory settings compared with the period before SBT was introduced. Of note,these results were achieved without worsening the extubation failure rate [31].
Recently, by reviewing data of their rst study on 44 infants (weighing less than 1,250 g), the same group was able to improve speci city from 63 to 75%, with a positive predictive value of 95%, by combining the SBT with measured variability in respiratory parameters. More speci cally, infants who eventually did need to be re-intubated had a lower variability index of mean inspiratory ow prior to extubation. Although promising, these predictive tools need to be con rmed in larger prospective trials