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Non-invasive ventilation following extubation in high-risk patients reduces need for re-intubation .

Citation/s: Nava S, Gregoretti C, Fanfulla F, Squadrone E, Grassi M, Carlucci A, Beltrame F, Navalesi P. Noninvasive ventilation to prevent respiratory failure after extubation in high-risk patients. Crit Care Med 2005; 33: 2465-2470

Lead author: Stefano Nava, Respiratory Unit, Fondazione S Maugeri, Istituto Scientifico di Pavia, ITALY.

Three-part Clinical Question: In intensive care patients ventilated for >48hrs and at high-risk of failure of extubation, does the application of non-invasive ventilation (NIV) reduce the need for re-intubation?

Search Terms: Ventilator weaning; randomised controlled trial.

The Study: Non-blinded, concealed, randomised controlled trial with intention-to-treat.

The Study Patients: Mixed adult ICU, Inclusion: ventilation >48 h and successful weaning trial (daily reduction of PSV or single daily T-piece trial), PLUS any one of the following risk factors for developing post-extubation respiratory failure: more than one consecutive failure of weaning trial; chronic heart failure; PaCO₂ >6kPa after extubation; more than one co-morbidity (excluding chronic heart failure); weak cough (defined as Airway Care Score* ≥8 and <12 or upper airways stridor at extubation not requiring immediate reintubation.

Exclusion: coma, inability to protect the airways defined as a Airway Care Score >12 or a documented swallowing problem; cervical spine injury; neuromuscular diseases; lack of informed consent or uncooperative state; anatomical abnormalities interfering with mask fit; uncontrolled cardiac ischaemia or arrhythmias; failure of more than two organs. Also excluded: BMI>=30; obstructive sleep apnoea; and those on home non-invasive ventilation.

1170 patients were screened for inclusion, 855 were ventilated >48 hours, 122 met the at risk criteria; 25 were excluded; 7 were missed and not recruited, 2 refused entry and 16 met pre-determined exclusion criteria. Mean SAPS II scores were approximately 32 in each group. The case mix was a mixture of surgical and medical patients and over one third in each group had an exacerbation of COPD

Control group (N = 49; 49 analysed): Oxygen therapy delivered to achieve arterial oxygen saturation (SaO₂) of >92%. Re-intubation was performed if with one major or two minor criteria were met after receiving assigned management of one hour:

Major criteria: respiratory acidosis (pH<7.35 with a pCO₂> 6 kPa or if hypercapnic at the time of extubation, a PaCO₂ increase of >15%); hypoxaemia (SaO₂ <90% for FiO₂ >50%).

Minor criteria: increase in respiratory rate >20% from time of extubation and in any case >35/Min; clinical signs of respiratory muscle fatigue (e.g. accessory muscle use); severe dyspnoea; inability to remove secretions (Airway Care Score >12). Re-intubation also performed in emergency situations such as cardiac or respiratory arrest. Both groups received standard medical care including daily respiratory physiotherapy.

Experimental group (N = 48; 48 analysed): NIV beginning after randomisation. Specifically designed ventilator or ICU ventilator used with facemask interface in first instance (changed in some to a nasal mask). Non-hypercapnic patients were given an initial PEEPext of 5 cmH₂O which could be increased until the oxygen saturation was constantly >92% and the Pinsp was initially set at 10cmH2O and increased to a maximum tolerated. Hypercapnic patients were given PEEPext of 6 cmH₂O and Pinsp adjusted according to tolerance. In both target was a respiratory rate < 25breaths/min, oxygen saturations > 92%, pH >7.35. FiO₂ adjusted to achieve SaO₂>92%. Applied using 'sequential protocol' for at least 48 hours and then withdrawn, if the patient was stable, if not it could be continued beyond 48 hours at the discretion of the clinician. The protocol demanded at least 8 hours of NIV in each 24 hour period. Re-intubation criteria: as control group.

The Evidence:

The trial was stopped after recruiting 50% of the planned patients because of a planned interim analysis demonstrating a benefit from the intervention.
 

EBM comments:

 

1. Do the methods allow accurate testing of the hypothesis? Yes. Not possible to blind during intervention and re-intubation was according to stringent pre-determined criteria. No mention by authors of blinding at data collation/analysis stage.
   
    

2. Do the statistical tests correctly test the results to allow differentiation of statistically significant results? Yes. The conclusion regarding the primary outcome of re-intubation is valid although it could have been demonstrated using a simpler statistical method.    Re-intubation is associated with increased risk of ICU mortality, however, on an intention-to-treat basis the provision of non-invasive ventilation following extubation does not alter mortality rate.

3. Are conclusions valid in light of the results? Yes, with regard to the effect on need for re-intubation. Despite the authors assertions to the contrary, there is no evidence that the use of non-invasive ventilation in high-risk patient reduces ICU mortality.
   
    

4. Did results get omitted, and why? No.
   
    

5. Did they suggest areas of further research? No.
   
    

6. Did they make any recommendations based on the results and were they appropriate? No.
   
    

7. Is the study relevant to my clinical practice? Yes, but one must bear in mind that this group represents only 11% of patients ventilated for more than 48 hours.  The case mix was a mixture of surgical and medical patients and over one third in each group had an exacerbation of COPD.  The indications for re-intubation were at a lower threshold than used in UK ICUs.  This may reflect differences in unit organisation and staffing.
   
    

8. What level of evidence does this study represent? 1⁺.

9. What grade of recommendation can I make on this result alone? B.

10. What grade of recommendation can I make when this study is considered along with other available evidence? B. At the time of writing this is the only trial of its type using NIV as a pre-emptive, preventative measure following extubation. [Edit: since writing Ferrer M, et al. Am J Respir Crit Care Med2006; 73: 164-170 demonstrated a reduction in post-extubation respiratory failure but not in re-intubation rates.]

11. Should I change my practice because of these results? Yes, in patients you think are at high-risk of re-intubation, provision of non-invasive ventilation following extubation may help reduce re-intubation rate.   A factor which may help you decide whether this process is worthwhile is how common is re-intubation in your ICU?  However, note that this did not change ICU mortality or length of stay; had these outcomes had been affected we would feel likely to alter our practice.

12.  Should I audit my current practice because of these results? Yes – Perhaps auditing your own re-intubation rate first.

 Appraised by: Andrew J Cadamy, SpR in Anaesthesia and Intensive Care Medicine, Glasgow Royal Infirmary; 20 March 2006

Email: ajcadamy@hotmail.com

Kill or Update By: March 2010

Reviewed & Edited by Chris Cairns & Malcolm Daniel

* The Airway Care Score referred to is a semi-quantitative score based on six fields for spontaneous cough, gag, sputum quantity, sputum viscosity, frequency of suctioning, and purulence of sputum. (Coplin et al. Am J Respir Crit Care Med  2000; 161: 1530–1536)

Citation: EBM Critical Appraisals. Scottish Intensive Care Society EBM Group. 2006 & JICS 2006 Vol7(3);69-71. Cadamy AJ. Nava S, Gregoretti C, Fanfulla F, Squadrone E, Grassi M, Carlucci A, Beltrame F, Navalesi P. Noninvasive ventilation to prevent respiratory failure after extubation in high-risk patients. Crit Care Med 2005; 33: 2465-2470 

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