Mosier and Law [
11] updated recent findings about airway management in critically ill patients. They highlighted the importance of pre-intubation evaluation for potential difficulty [
12] and appropriate planning and implementation of guidelines [
13], positioning, pre-oxygenation [
13] and, in selected patients, the use of a neuromuscular blocking agent have been shown to be useful for minimizing the difficult intubation and intubation-related complications [
13]. Although there are controversies regarding the use of video laryngoscopy as the primary method of intubation, it has been shown to be at least as good as, and often more successful than, direct laryngoscopy [
14,
15].
De Jong et al. [
15] systematically reviewed and meta-analysed RCTs and prospective [
14] and retrospective observational studies of video laryngoscope vs. direct laryngoscope (DL) in adults who were intubated in the ICU. Nine trials with a total of 2,133 participants (1,066 in VL and 1,067 in DL) were included in the analysis. Compared to direct laryngoscopy, video laryngoscope reduced the risk of difficult intubation [OR 0.29 (95 % confidence interval (CI) 0.20–0.44)], Cormack grade 3/4 [0.26 (0.17–0.41)], oesophageal intubation [0.14 (0.02–0.81)] and increased the first-attempt success rate [2.1 (1.4–3.2)]. No statistically significant differences were found for severe hypoxaemia, cardiovascular collapse or airway injury.
Graciano et al. [
16] evaluated the incidence and associated risk factors of difficult tracheal intubations in paediatric ICU. They used data collected prospectively from 15 paediatric ICUs related to tracheal intubation for the National Emergency Airway Registry for Children (NEAR4KIDS). A total of 1,516 oral tracheal intubations were reported (median 2 years of age) and 97 % of patients were intubated with direct laryngoscopy. Difficult tracheal intubation was reported in 9 % of intubations and was associated with a higher incidence of oxygen desaturation less than 80 % (48 vs. 15 %,
p < 0.001), adverse tracheal intubation-associated events (53 vs. 20 %,
p < 0.001) and severe tracheal intubation-associated events (13 vs. 6 %,
p = 0.003). A history of difficult airways and sign of upper airway obstruction were associated with difficult tracheal intubation.
Serpa Neto et al. [
17] performed an individual patient data meta-analysis of seven studies (2,184 patients) to assess the associations between tidal volume size, duration of mechanical ventilation and need of sedation in patients without ARDS. Patients were assigned to three groups based on tidal volume size (≤6, 6–10 and ≥10 ml/kg PBW). The number of patients breathing without assistance by day 28 was higher in the group ventilated with tidal volume ≤6 ml/kg PBW as compared to those ventilated with tidal volume ≥10 ml/kg PBW (93 vs. 89 %;
p = 0.03). Only two studies (187 patients) could be included in the meta-analysis of need of sedation. There were no differences in number of days patients received sedatives, opioids or neuromuscular blocking agents, or in the total dose of any of these drugs. The results suggest that use of lower tidal volumes in patients without ARDS at the onset of mechanical ventilation could be associated with shorter duration of ventilation. Use of lower tidal volumes seems not to affect sedation or analgesia needs, but this need to be confirmed in a robust well-powered RCT.
Non-invasive ventilation
In 2014, studies assessed the use of non-invasive ventilation (NIV) in medical [
18,
19] and surgical [
20,
21] patients. Lorut et al. [
22] reported a large multicentre RCT that investigated whether systematic postoperative NIV vs. standard care prevented respiratory complications following lung resection in a selected population of 349 COPD patients. NIV was delivered intermittently through facial or nasal masks 6 h per day for 48 h postoperatively. The rates of acute respiratory events (primary endpoint) or acute respiratory failure were not different between the NIV and control group. Rescue NIV was used less in the NIV group, but re-intubation rates were not different between the groups. Mortality rates were low in both groups. This paper was accompanied by an editorial [
23], which gave some possible explanations for the lack of beneficial effects. In the postoperative period, it is sometimes difficult to clearly separate “preventive” and “curative” application of NIV. Probably some of the patients received NIV for “grey zone” indications (at the time of starting NIV and also after) which may be considered as an intermediary state between “preventive” and “curative” application of NIV [
23]. Further studies are needed to better identify the patients who may benefit from NIV after thoracic surgery and the optimal NIV protocol (duration, settings, interfaces and humidification systems use for gas conditioning).
Lellouche et al. [
24] assessed the impact of the type of humidification system used on the success rate of NIV using ICU ventilators for ARF in an RCT. This international RCT included 247 patients, 128 of whom were allocated to a heat and moisture exchanger (HME) group and 119 to a heated humidifier (HH) group. There was no significant difference in the intubation rates (the primary endpoint) between the HH and HME groups (37 vs. 30 %, respectively,
p = 0.28). No significant difference was observed for NIV duration, ICU and hospital LOS or ICU mortality. In addition, no difference in the patients’ mucosal dryness was reported with HH in comparison with HME. These results suggest that despite a strong physiologic rationale supporting the use of HH during NIV [
25], this method cannot be recommended as a first-line treatment in all patients with ARF. The use of an HME (ideally with a low dead space) while removing the additional dead space (flex-tubing) seems to be acceptable in light of the results of this study. Finally, contrary to recommendations published in 2012 that propose HH for NIV rather than HME, the authors found no difference in outcomes. However, in the presence of persistent high PaCO
2 levels associated with threatening encephalopathy, the reduction of dead space with an HH may be considered. This paper was accompanied by an editorial [
26] which asked the question why a trial that finished enrolling patients in December 2003 would be published 10 years later. The authors of this editorial [
26] emphasized that every reasonable attempt should still be made to publish the data.
Brambilla et al. [
19] evaluated the efficacy of non-invasive continuous positive airway pressure (CPAP) to improve outcomes in severe hypoxaemic ARF (hARF) due to pneumonia in an RCT conducted in four Italian centres. Patients were randomised to receive helmet CPAP (CPAP group,
n = 40) or oxygen delivered with a Venturi mask (control group,
n = 41). Helmet CPAP reduced the risk of reaching criteria for endotracheal intubation (the primary endpoint) as compared to oxygen therapy (6/40 = 15 % vs. 26/41 = 63 %, respectively,
p < 0.001). The CPAP group also showed faster and greater improvement in oxygenation in comparison to controls. In either study group, no relevant adverse events were detected; two patients were intubated in the CPAP group and one in the control group.
Schnell et al. [
18] evaluated the use and outcomes of NIV over a 15-year period (1997–2011) from a multicentre database of critically ill patients who required ventilatory support for ARF. The impact of first-line NIV on 60-day mortality was evaluated using a marginal structural model. Of 3,163 patients, 1,232 (39 %) patients received NIV. Over the study period, use of first-line NIV increased from 29 to 42 % and NIV success rates increased from 69 to 84 %. NIV decreased 60-day mortality, and this was observed mainly in patients with acute-on-chronic respiratory failure, but not in patients with cardiogenic pulmonary oedema, or in patients with hARF (both immunocompetent and immunocompromised). NIV failure was an independent, time-dependent risk factor for mortality. The authors emphasized that further studies are warranted on early predictors of NIV failure to help in selecting patients for NIV [
27,
28].
Weaning
In their “Our paper 20 years later” Frutos-Vivar and Esteban described how withdrawal from mechanical ventilation has changed. At the beginning of the 1990s, there was little evidence regarding the best method of withdrawing patients from mechanical ventilation. Today, withdrawal from mechanical ventilation (or weaning) is one of the most common procedures in ICU. Esteban et al. [
29] published one of the seminal papers on weaning in which they reported that the best method for withdrawal from mechanical ventilation in difficult-to-wean patients was a once-daily spontaneous breathing trial with a T-piece. Following this study [
29,
30], several other studies [
31] have shaped weaning as an evidence-based technique. The results of these studies [
29,
32] have been applied progressively to clinical practice. Currently, the withdrawal from mechanical ventilation could be summarized as the performance of a spontaneous breathing trial to evaluate extubation readiness (this trial could be performed with a T-piece, which occurs most commonly, or with CPAP or low levels of pressure support). Most patients could be disconnected after passing the first spontaneous breathing trial. In patients who failed the first attempt at withdrawal, the use of a once-daily spontaneous breathing trial or a gradual reduction in pressure support is the preferred weaning method. However, new applications of the standard techniques, such as NIV, or new methods of mechanical ventilation, such as automatic tube compensation, automated closed-loop systems and automated knowledge-based weaning systems could play a role in the management of the patients with difficult or prolonged weaning. In the future, studies should better evaluate the relationship between the implementation of protocols for the optimization of sedation and weaning outcomes. Moreover, the focus should be on the relationship between ICU-acquired weakness and weaning failure. An early mobilization of patients could be proposed for the prevention or early therapy of ICU-acquired weakness associated with mechanical ventilation weaning-sedation protocols.