Abstract
IntroductionPhysiological determinants of weaning success and failure are usually studied in ventilator-supported patients, comparing those who failed a trial of spontaneous breathing with those who tolerated such a trial and were successfully extubated. A major limitation of these studies was that the two groups may be not comparable concerning the severity of the underlying disease and the presence of comorbidities. In this physiological study, we assessed the determinants of weaning success in patients acting as their own control, once they are eventually liberated from the ventilator.MethodsIn 30 stable tracheotomised ventilator-dependent patients admitted to a weaning center inside a respiratory intensive care unit, we recorded the breathing pattern, respiratory mechanics, inspiratory muscle function, and tension-time index of diaphragm (TTdi = Pdisw/Pdimax [that is, tidal transdiaphragmatic pressure over maximum transdiaphragmatic pressure] × Ti/Ttot [that is, the inspiratory time over the total breath duration]) at the time of weaning failure (T0). The measurements were repeated in all the patients (T1) either during a successful weaning trial (successful weaning [SW] group, n = 16) or 5 weeks later, in the case of repeated weaning failure (failed weaning [FW] group, n = 14).ResultsCompared to T0, in the FW group at T1, significant differences were observed only for a reduction in spontaneous breathing frequency and in TTdi (0.21 ± 0.122 versus 0.14 ± 0.054, P = 0.008). SW patients showed a significant increase in Pdimax (34.9 ± 18.9 cm H2O versus 43.0 ± 20.0, P = 0.02) and decrease in Pdisw/Pdimax (36.0% ± 15.8% versus 23.1% ± 7.9%, P = 0.004).ConclusionsThe recovery of an inadequate inspiratory muscle force could be the major determinant of 'late' weaning success, since this allows the patients to breathe far below the diaphragm fatigue threshold.
Highlights
Physiological determinants of weaning success and failure are usually studied in ventilator-supported patients, comparing those who failed a trial of spontaneous breathing with those who tolerated such a trial and were successfully extubated
In the present physiological study, we describe the mechanisms of weaning success or failure in difficult-to-wean patients, and for the first time, we use the recordings of respiratory mechanics during a trial of spontaneous breathing in an attempt to understand the underlying mechanism that enables a particular patient to be successfully weaned some time after having failed a previous weaning attempt
Jubran and Tobin [4] first reported systematic measurements of respiratory muscle function and respiratory mechanics in patients with chronic obstructive pulmonary disease (COPD) who failed a trial of spontaneous breathing, and compared the results with those obtained in COPD patients successfully extubated at the first attempt
Summary
Physiological determinants of weaning success and failure are usually studied in ventilator-supported patients, comparing those who failed a trial of spontaneous breathing with those who tolerated such a trial and were successfully extubated. A major limitation of these studies was that the two groups may be not comparable concerning the severity of the underlying disease and the presence of comorbidities In this physiological study, we assessed the determinants of weaning success in patients acting as their own control, once they are eventually liberated from the ventilator. In a multicenter study [1], it was found that approximately 15% of patients failed an initial attempt of weaning from mechanical ventilation This subset of patients usually requires prolonged mechanical ventilation and, for this reason, accounts for about 40% of total intensive care unit (ICU) costs [2]. In the present physiological study, we describe the mechanisms of weaning success or failure in difficult-to-wean patients, and for the first time, we use the recordings of respiratory mechanics during a trial of spontaneous breathing in an attempt to understand the underlying mechanism that enables a particular patient to be successfully weaned some time after having failed a previous weaning attempt
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