However, the increase in capillary pulmonary pressure occurring during the transition from mechanical to spontaneous ventilation depends on the type of weaning trial. The standard test for extubation readiness is the spontaneous breathing trial (SBT) performed using the T-tube by simply disconnecting the patient from the ventilator and providing additional oxygen. The weaning trial can also be performed without disconnecting the patient from the ventilator using a low level of pressure support, although respiratory rate and tidal volume are continuously monitored on the ventilator screen. Cabello et al.  compared three modalities of trial before extubation in a selected population of patients with difficult weaning. A SBT on a T-tube was compared with a low pressure support level (7 cmH2O) with or without PEEP. They showed that the patient effort was higher during a T-tube trial than during a pressure support trial. During the pressure support trial, addition of PEEP further decreased both the effort and capillary pulmonary pressure, suggesting that weaning trials must be done without PEEP to unmask latent cardiac dysfunction . In a large, multicentre, randomized controlled trial, although the proportion of patients who failed the first trial was higher using T-tube than using a pressure support trial , the rate of patients who were extubated after 48 h was similar when the weaning trial was performed using T-tube or pressure support trial. Other studies suggested that some patients who failed a T-tube trial could immediately succeed a pressure support trial [21,34] and could be extubated without an increased risk of extubation failure . Overall, this suggests that either the T-tube trial slightly delays weaning readiness due to higher respiratory muscle effort or, on the contrary that the pressure support trial may expose to a higher risk of reintubation. The use of pressure support was justified by reducing the imposed work of the ventilator circuit and the endotracheal tube . However, the postextubation period is characterized by a relatively high upper airway resistance and an overall work of breathing similar before and after removal of endotracheal tube . Therefore, addition of even low levels of pressure support may lead to underestimate the risk of extubation failure in some patients .
The two goals of a weaning trial are the early detection of patients who are able to breathe without a ventilator, in order to avoid complications of prolonged mechanical ventilation and the identification of patients who are not able to breathe spontaneously to avoid extubation failure and its potential complications. In the vast majority of patients, the main objective is the early detection of weaning trial success and a short trial is fully effective . However, a more challenging SBT using prolonged T-tube trial might be especially interesting in a population in which the risk of reintubation is particularly high [2▪▪,5].
Regardless of the weaning strategy used in ICUs, early identification of patients who are able to breathe spontaneously results in better outcomes, and it has been clearly demonstrated that the use of a weaning protocol, including daily screening followed by weaning trial and systematic extubation if successful, shortened intubation time without an increased risk of reintubation [13,38]. This strategy is usually caregiver-driven but can also be computer-driven by an automatic system, keeping the patient in a ‘respiratory comfort zone’ on the basis of respiratory rate, tidal volume and end-tidal CO2. This automated-weaning system allows to facilitate the weaning by gradually decreasing the level of pressure support and to perform a pressure support weaning trial when the lower level of assistance has been reached, suggesting to the clinician that the patient can be separated from the ventilator when this test is successful . A randomized controlled trial has revealed that automated-weaning system shortened overall ventilation time as compared with usual care , and a recent study [41▪▪] found similar results in postsurgical patients, but only in those after cardiac surgery. Although automated weaning could have no beneficial results compared to a nurse-driven protocol in units with a high nurse ratio and staffing , most studies that have compared automated-weaning system versus standard weaning found either reduction or similar duration of intubation time.
The SBT is meant to accurately predict the tolerance of unassisted breathing after extubation. However, it does not predict well the consequences of the tube removal in terms of upper airway patency and lower airway protection, removal of secretions and, ultimately, the ability to sustain spontaneous breathing. Interestingly, it has been suggested that extubation success may be well correlated to the patient's subjective perception of his ability to breathe without the ventilator .
Postextubation laryngeal oedema is due to the pressure exerted by the endotracheal tube and is favoured by the conditions of intubation and the duration of mechanical ventilation . Laryngeal oedema occurs in about 5–15% of the patients [56–60], more often in women [56,60], with a low patient's height/tube diameter ratio . A good marker of severe laryngeal oedema is the absence of air leak when the sealing balloon cuff of the endotracheal tube is deflated. A low cuff-leak volume (<110–130 ml) measured by the difference between the insufflated volume and the expired volume in assist-control volume mode after deflating the balloon may be useful in identifying patients at risk for postextubation stridor [57,58]. However, although the absence of air leak is a good predictor of laryngeal oedema, the presence of detectable leak does not rule out the occurrence of upper airway obstruction . Upper airway obstruction was found to be the cause of extubation failure in 7–20% of the cases [3,10,61], but reached 38% in a large multicentric study focusing on postextubation stridor . In this latter study, administration of methylprednisolone prior to extubation reduced the incidence of stridor and the rate of reintubation due to laryngeal oedema . Recently, it has been found that a majority of patients ventilated more than 24 h exhibited laryngeal lesions, suggesting that this may favour postextubation respiratory distress by increasing work of breathing and/or favouring aspiration through glottis dysfunction. Interestingly, unlike other causes, when reintubation is purely linked to transient laryngeal oedema, it does not seem to be associated with a poor prognosis .
The use of NIV to treat postextubation respiratory distress or as a prophylactic measure to avoid respiratory distress needs to be distinguished. The literature suggests that prophylactic NIV after extubation may be useful to prevent acute respiratory failure in selected populations [62–64], whereas NIV employed for treating postextubation acute respiratory failure has no proven benefit  and can even increase mortality by delaying reintubation . However, NIV could reduce the risk of reintubation in postoperative patients after major elective abdominal surgery  or lung resection , and could even reduce mortality in this latter group. Indications and results of postextubation NIV on outcome are summarized in Table 3 [11,62–67,68▪▪].
Papers of particular interest, published within the annual period of review, have been highlighted as:
Additional references related to this topic can also be found in the Current World Literature section in this issue (p. 72).
1. Esteban A, Ferguson ND, Meade MO, et al. Evolution of mechanical ventilation in response to clinical research. Am J Respir Crit Care Med 2008; 177:170–177.
2▪▪. Thille AW, Harrois A, Schortgen F, et al. Outcomes of extubation
failure in medical intensive care unit patients. Crit Care Med 2011; 39:2612–2618.
A prospective observational study showing that failed extubation was followed by marked clinical deterioration, suggesting a direct effect on patient outcomes. Age and underlying chronic cardiac/respiratory failure were the only factors associated with extubation failure.
3. Esteban A, Alia I, Gordo F, et al. Extubation
outcome after spontaneous breathing trials with T-tube or pressure support ventilation. The Spanish Lung Failure Collaborative Group. Am J Respir Crit Care Med 1997; 156:459–465.
4. Esteban A, Alia I, Tobin MJ, et al. Effect of spontaneous breathing trial
duration on outcome of attempts to discontinue mechanical ventilation. Spanish Lung Failure Collaborative Group. Am J Respir Crit Care Med 1999; 159:512–518.
5. Epstein SK, Ciubotaru RL, Wong JB. Effect of failed extubation
on the outcome of mechanical ventilation. Chest 1997; 112:186–192.
6. Vallverdu I, Calaf N, Subirana M, et al. Clinical characteristics, respiratory functional parameters, and outcome of a two-hour T-piece trial in patients weaning from mechanical ventilation
. Am J Respir Crit Care Med 1998; 158:1855–1862.
7▪▪. Peñuelas O, Frutos-Vivar F, Fernandez C, et al. Characteristics and outcomes of ventilated patients according to time to liberation from mechanical ventilation. Am J Respir Crit Care Med 2011; 184:430–437.
A secondary analysis of a large prospective cohort trial analysing outcomes of mechanically ventilated patients according to the new weaning classification. In the 6% of patients who were classified as prolonged weaning (>7 days), there was a significantly longer length of stay and higher ICU mortality.
8▪. Frutos-Vivar F, Esteban A, Apezteguia C, et al. Outcome of reintubated patients after scheduled extubation
. J Crit Care 2011; 26:502–509.
In this large prospective cohort trial including 1152 mechanically ventilated patients who succeeded a weaning trial, 16% were reintubated within 48 h after extubation and reintubation was independently associated with mortality.
9. Frutos-Vivar F, Ferguson ND, Esteban A, et al. Risk factors for extubation
failure in patients following a successful spontaneous breathing trial
. Chest 2006; 130:1664–1671.
10. Epstein SK, Ciubotaru RL. Independent effects of etiology of failure and time to reintubation on outcome for patients failing extubation
. Am J Respir Crit Care Med 1998; 158:489–493.
11. Esteban A, Frutos-Vivar F, Ferguson ND, et al. Noninvasive positive-pressure ventilation for respiratory failure after extubation
. N Engl J Med 2004; 350:2452–2460.
12. Boles JM, Bion J, Connors A, et al. Weaning from mechanical ventilation
. Eur Respir J 2007; 29:1033–1056.
13. Girard TD, Kress JP, Fuchs BD, et al. Efficacy and safety of a paired sedation and ventilator weaning protocol for mechanically ventilated patients in intensive care (Awakening and Breathing Controlled trial): a randomised controlled trial. Lancet 2008; 371:126–134.
14. Funk GC, Anders S, Breyer MK, et al. Incidence and outcome of weaning from mechanical ventilation
according to new categories. Eur Respir J 2010; 35:88–94.
15. Tonnelier A, Tonnelier JM, Nowak E, et al. Clinical relevance of classification according to weaning difficulty. Respir Care 2011; 56:583–590.
16. Sellares J, Ferrer M, Cano E, et al. Predictors of prolonged weaning and survival during ventilator weaning in a respiratory ICU
. Intensive Care Med 2011; 37:775–784.
17. Brochard L, Rauss A, Benito S, et al. Comparison of three methods of gradual withdrawal from ventilatory support during weaning from mechanical ventilation
. Am J Respir Crit Care Med 1994; 150:896–903.
18. Esteban A, Frutos F, Tobin MJ, et al. A comparison of four methods of weaning patients from mechanical ventilation. Spanish Lung Failure Collaborative Group. N Engl J Med 1995; 332:345–350.
19. Lemaire F, Teboul JL, Cinotti L, et al. Acute left ventricular dysfunction during unsuccessful weaning from mechanical ventilation
. Anesthesiology 1988; 69:171–179.
20. Buda AJ, Pinsky MR, Ingels NB Jr, et al. Effect of intrathoracic pressure on left ventricular performance. N Engl J Med 1979; 301:453–459.
21. Cabello B, Thille AW, Roche-Campo F, et al. Physiological comparison of three spontaneous breathing trials in difficult-to-wean patients. Intensive Care Med 2010; 36:1171–1179.
22. Caille V, Amiel JB, Charron C, et al. Echocardiography: a help in the weaning process. Crit Care 2010; 14:R120.
23. Carrié C, Bui HN, Gerbaud E, et al. Myocardial ischaemia and weaning failure: is angioplasty the heart of the problem? Intensive Care Med 2011; 37:1223–1224.
24. Grasso S, Leone A, De Michele M, et al. Use of N-terminal pro-brain natriuretic peptide to detect acute cardiac dysfunction during weaning failure in difficult-to-wean patients with chronic obstructive pulmonary disease. Crit Care Med 2007; 35:96–105.
25▪. Zapata L, Vera P, Roglan A, et al. B-type natriuretic peptides for prediction and diagnosis of weaning failure from cardiac origin. Intensive Care Med 2011; 37:477–485.
A prospective observational study showing that increases in natriuretic peptides during a SBT could predict weaning failure of cardiac origin. BNP performed better than NT-proBNP.
26▪. Ouanes-Besbes L, Dachraoui F, Ouanes I, et al. NT-proBNP levels at spontaneous breathing trial
help in the prediction of postextubation respiratory distress. Intensive Care Med 2012; 38:788–795.
This study suggests that high levels of BNP before SBT may predict postextubation respiratory failure.
27. Chien JY, Lin MS, Huang YC, et al. Changes in B-type natriuretic peptide improve weaning outcome predicted by spontaneous breathing trial
. Crit Care Med 2008; 36:1421–1426.
28▪▪. Mekontso Dessap A, Roche-Campo F, Kouatchet A, et al.
Natriuretic peptide-driven fluid management during ventilator weaning: a randomized controlled trial. Am J Respir Crit Care Med 2012 [Epub ahead of print].
This study suggests that negative balance using diuretics may hasten extubation, especially in patients with left ventricular dysfunction.
29. Wiedemann HP, Wheeler AP, Bernard GR, et al. Comparison of two fluid-management strategies in acute lung injury. N Engl J Med 2006; 354:2564–2575.
30. Lamia B, Maizel J, Ochagavia A, et al. Echocardiographic diagnosis of pulmonary artery occlusion pressure elevation during weaning from mechanical ventilation
. Crit Care Med 2009; 37:1696–1701.
31. Moschietto S, Doyen D, Grech L, et al. Transthoracic echocardiography with Doppler tissue imaging predicts weaning failure from mechanical ventilation: evolution of the left ventricle relaxation rate during a spontaneous breathing trial
is the key factor in weaning outcome. Crit Care 2012; 16:R81.
32▪. Papanikolaou J, Makris D, Saranteas T, et al. New insights into weaning from mechanical ventilation
: left ventricular diastolic dysfunction is a key player. Intensive Care Med 2011; 37:1976–1985.
A prospective observational study in a noncardiac population of mechanically ventilated patients suggesting that left ventricular diastolic dysfunction measured with echocardiography before the SBT was associated with weaning outcome.
33▪. Soummer A, Perbet S, Brisson H, et al. Ultrasound assessment of lung aeration loss during a successful weaning trial predicts postextubation distress. Crit Care Med 2012; 40:2064–2072.
This study suggests that the loss of lung aeration during a successful SBT may help to predict postextubation respiratory distress.
34. Ezingeard E, Diconne E, Guyomarc’h S, et al. Weaning from mechanical ventilation
with pressure support in patients failing a T-tube trial of spontaneous breathing. Intensive Care Med 2006; 32:165–169.
35. Brochard L, Rua F, Lorino H, et al. Inspiratory pressure support compensates for the additional work of breathing caused by the endotracheal tube. Anesthesiology 1991; 75:739–745.
36. Straus C, Louis B, Isabey D, et al. Contribution of the endotracheal tube and the upper airway to breathing workload. Am J Respir Crit Care Med 1998; 157:23–30.
37. Tobin MJ. Extubation
and the myth of ‘minimal ventilator settings’. Am J Respir Crit Care Med 2012; 185:349–350.
38. Ely EW, Baker AM, Dunagan DP, et al. Effect on the duration of mechanical ventilation of identifying patients capable of breathing spontaneously. N Engl J Med 1996; 335:1864–1869.
39. Dojat M, Harf A, Touchard D, et al. Clinical evaluation of a computer-controlled pressure support mode. Am J Respir Crit Care Med 2000; 161:1161–1166.
40. Lellouche F, Mancebo J, Jolliet P, et al. A multicenter randomized trial of computer-driven protocolized weaning from mechanical ventilation
. Am J Respir Crit Care Med 2006; 174:894–900.
41▪▪. Schadler D, Engel C, Elke G, et al. Automatic control of pressure support for ventilator weaning in surgical intensive care patients. Am J Respir Crit Care Med 2012; 185:637–644.
This prospective controlled study compares an automated weaning protocol with a standardized written protocol and shows no differences in the overall ventilation times in surgical patients.
42. Rose L, Presneill JJ, Johnston L, et al. A randomised, controlled trial of conventional versus automated weaning from mechanical ventilation
using SmartCare/PS. Intensive Care Med 2008; 34:1788–1795.
43. Perren A, Previsdomini M, Llamas M, et al. Patients’ prediction of extubation
success. Intensive Care Med 2010; 36:2045–2052.
44. Namen AM, Ely EW, Tatter SB, et al. Predictors of successful extubation
in neurosurgical patients. Am J Respir Crit Care Med 2001; 163:658–664.
45. Mokhlesi B, Tulaimat A, Gluckman TJ, et al. Predicting extubation
failure after successful completion of a spontaneous breathing trial
. Respir Care 2007; 52:1710–1717.
46. Smina M, Salam A, Khamiees M, et al. Cough peak flows and extubation
outcomes. Chest 2003; 124:262–268.
47. Khamiees M, Raju P, DeGirolamo A, et al. Predictors of extubation
outcome in patients who have successfully completed a spontaneous breathing trial
. Chest 2001; 120:1262–1270.
48. Coplin WM, Pierson DJ, Cooley KD, et al. Implications of extubation
delay in brain-injured patients meeting standard weaning criteria. Am J Respir Crit Care Med 2000; 161:1530–1536.
49. Ely EW, Shintani A, Truman B, et al. Delirium as a predictor of mortality in mechanically ventilated patients in the intensive care unit. JAMA 2004; 291:1753–1762.
50. De Jonghe B, Sharshar T, Lefaucheur JP, et al. Paresis acquired in the intensive care unit: a prospective multicenter study. JAMA 2002; 288:2859–2867.
51. De Jonghe B, Bastuji-Garin S, Durand MC, et al. Respiratory weakness is associated with limb weakness and delayed weaning in critical illness. Crit Care Med 2007; 35:2007–2015.
52. De Jonghe B, Bastuji-Garin S, Sharshar T, et al. Does ICU
-acquired paresis lengthen weaning from mechanical ventilation
? Intensive Care Med 2004; 30:1117–1121.
53. Garnacho-Montero J, Amaya-Villar R, Garcia-Garmendia JL, et al. Effect of critical illness polyneuropathy on the withdrawal from mechanical ventilation and the length of stay in septic patients. Crit Care Med 2005; 33:349–354.
54▪▪. Kim WY, Suh HJ, Hong SB, et al. Diaphragm dysfunction assessed by ultrasonography: influence on weaning from mechanical ventilation
. Crit Care Med 2011; 39:2627–2630.
This study shows that diaphragmatic dysfunction diagnosed by ultrasonography is seen in around 30% of patients without previous diaphragmatic diseases and is associated with weaning failure.
55. Tadié JM, Behm E, Lecuyer L, et al. Postintubation laryngeal injuries and extubation
failure: a fiberoptic endoscopic study. Intensive Care Med 2010; 36:991–998.
56. Darmon JY, Rauss A, Dreyfuss D, et al. Evaluation of risk factors for laryngeal edema after tracheal extubation
in adults and its prevention by dexamethasone. A placebo-controlled, double-blind, multicenter study. Anesthesiology 1992; 77:245–251.
57. Miller RL, Cole RP. Association between reduced cuff leak volume and postextubation stridor. Chest 1996; 110:1035–1040.
58. Jaber S, Chanques G, Matecki S, et al. Postextubation stridor in intensive care unit patients. Risk factors evaluation and importance of the cuff-leak test. Intensive Care Med 2003; 29:69–74.
59. Cheng KC, Hou CC, Huang HC, et al. Intravenous injection of methylprednisolone reduces the incidence of postextubation stridor in intensive care unit patients. Crit Care Med 2006; 34:1345–1350.
60. François B, Bellissant E, Gissot V, et al. 12-h pretreatment with methylprednisolone versus placebo for prevention of postextubation laryngeal oedema: a randomised double-blind trial. Lancet 2007; 369:1083–1089.
61. Ochoa ME, Marin Mdel C, Frutos-Vivar F, et al. Cuff-leak test for the diagnosis of upper airway obstruction in adults: a systematic review and meta-analysis. Intensive Care Med 2009; 35:1171–1179.
62. Nava S, Gregoretti C, Fanfulla F, et al. Noninvasive ventilation to prevent respiratory failure after extubation
in high-risk patients. Crit Care Med 2005; 33:2465–2470.
63. Ferrer M, Valencia M, Nicolas JM, et al. Early noninvasive ventilation averts extubation
failure in patients at risk: a randomized trial. Am J Respir Crit Care Med 2006; 173:164–170.
64. Ferrer M, Sellares J, Valencia M, et al. Noninvasive ventilation after extubation
in hypercapnic patients with chronic respiratory disorders: randomised controlled trial. Lancet 2009; 374:1082–1088.
65. Keenan SP, Powers C, McCormack DG, et al. Noninvasive positive-pressure ventilation for postextubation respiratory distress: a randomized controlled trial. JAMA 2002; 287:3238–3244.
66. Squadrone V, Coha M, Cerutti E, et al. Continuous positive airway pressure for treatment of postoperative hypoxemia: a randomized controlled trial. JAMA 2005; 293:589–595.
67. Auriant I, Jallot A, Herve P, et al. Noninvasive ventilation reduces mortality in acute respiratory failure following lung resection. Am J Respir Crit Care Med 2001; 164:1231–1235.
68▪▪. Su CL, Chiang LL, Yang SH, et al. Preventive use of noninvasive ventilation after extubation
: a prospective, multicenter randomized controlled trial. Respir Care 2012; 57:204–210.
This randomized controlled trial shows no benefit of prophylactic noninvasive ventilation in an unselected population.
69. Nava S, Ambrosino N, Clini E, et al. Noninvasive mechanical ventilation in the weaning of patients with respiratory failure due to chronic obstructive pulmonary disease. A randomized, controlled trial. Ann Intern Med 1998; 128:721–728.
70. Girault C, Daudenthun I, Chevron V, et al. Noninvasive ventilation as a systematic extubation
and weaning technique in acute-on-chronic respiratory failure: a prospective, randomized controlled study. Am J Respir Crit Care Med 1999; 160:86–92.
71. Ferrer M, Esquinas A, Arancibia F, et al. Noninvasive ventilation during persistent weaning failure: a randomized controlled trial. Am J Respir Crit Care Med 2003; 168:70–76.
72▪▪. Girault C, Bubenheim M, Abroug F, et al. Noninvasive ventilation and weaning in chronic hypercapnic respiratory failure patients: a randomized multicenter trial. Am J Respir Crit Care Med 2011; 184:672–679.