NIMV is theoretically able to counteract several physiological mechanisms associated with weaning difficulties. In ventilator-dependent chronic obstructive pulmonary disease (COPD) patients, NIMV has been shown to be as effective as invasive ventilation in reducing inspiratory effort and improving arterial blood gasses. In fact, following some uncontrolled clinical studies in which NIMV was used as a bridge to weaning, Nava et al. [5] performed the first study of this strategy. They randomized 50 COPD patients with hypercapnia into two groups and administered SBT with a T-piece 48 h after mechanical ventilation. One group was extubated and received pressure support ventilation (PSV) noninvasively, and the other group was administered invasive PSV. Patients in the group that received NIMV had lower weaning durations and nosocomial pneumonia incidence and higher 60-day survival rates. In addition, pH and PaCO₂ levels were similar in the NIMV group compared with the invasive mechanical ventilation (IMV) group.

Jiang et al. [6] conducted a prospective study on 93 patients who were randomized either to receive NIMV or oxygen therapy after planned or unplanned extubation, and they found no differences in the reintubation rates between two groups. Nava [7] and Ferrer et al. [8] performed two randomized trials to assess whether NIMV is effective in preventing the occurrence of post-extubation failure in patients at risk. Both of these studies showed that the groups treated with NIMV had a lower rate of intubation than the groups in which standard therapy was used. Furthermore, in one of the two studies, intensive care unit mortality was also reduced in the subgroup where patients with hypercapnia were treated with NIMV. Several randomized controlled trials, mainly conducted in patients with preexisting lung disease, have shown that the use of NIMV to avoid extubation in patients with difficult and prolonged weaning can result in reduced periods of endotracheal intubation, lower complication rates, and improved survival. NIMV is effective in avoiding respiratory failure after extubation and improving survival in patients at risk for complications [9]. In their randomized, prospective, clinical trial on 33 patients receiving IMV with acute respiratory failure diagnosis, Girault et al. [10] aimed to evaluate the utility of NIVM on systematic extubation in the difficult weaning process and its effects on weaning duration. They administered invasive PSV with decreasing pressure support levels until the extubation of all patients in both groups. Then they extubated patients in one group and administered NIMV with 2–4 h durations. Between NIVM administrations, they gave nasal oxygen. NIVM administration was performed via nasal or facial mask suitable for the face structure of the patient. In the other group, patients were extubated when invasive pressure support ventilation (IPSV) pressure suport levels were below 8 cmH₂O by decreasing levels with 3–5 cmH₂O, and they were given nasal oxygen following the extubation. The authors showed that it is possible to use NIMV as an early extubation and weaning technique and that it can reduce the duration of invasive mechanical ventilation (i.e., it permits earlier removal of the endotracheal tube) compared with invasive PSV in weaning intubated patients who are difficult to wean.