Author Archives: Cathy

Case

A 55 y/o male with a h/o EtOH abuse is intubated and admitted to the MICU for hypoxemic respiratory failure secondary to aspiration PNA.  Three days later, his vital signs have normalized, he is awake and able to follow commands, minimal secretions are noted with suctioning of his ET tube, and his SpO2 is >95% on 40% FiO2 and 5 PEEP.  He passes a 30 minute trial of spontaneous breathing with a T-piece.

Question

Following extubation, should he be given high-flow nasal oxygen to help prevent the need for reintubation?

Evidence

1. We previously reviewed the FLORALI trial, NEJM 2015 which looked at the up-front use of high-flow nasal cannula (HFNC) in patients with hypoxemic respiratory failure

1. 313 patients randomized to HFNC vs NIV
   1. HFNC did not lower need for intubation at 28 days
   2. HFNC did lower ICU and 90-day mortality
2. Interpretation of trial results complicated by significant cross-over in the use of HFNC and NIV between study arms

1. There is a growing body of literature on the use of HFNC following extubation
   1. We previously reviewed a JAMA 2015 trial looking at the use of HFNC vs NIV in 830 patients at high-risk of reintubation following cardiac surgery

1. No difference in treatment failure (defined as re-intubation, switch to other study treatment, or premature study discontinuation) between groups
2. Roughly 14% required re-intubation in each group (no difference)

• Similar dyspnea and comfort score between groups

1. 1. Nasal High-flow versus Venturi Mask Oxygen Therapy after Extubation, AJRCCM 2014, Italy

1. 105 patients with a P/F < 300 following SBT randomized to oxygen via HFNC (flow 50 L/min) or venturi mask for 48 hrs or until ICU discharge (the low P/F perhaps indicative of a group at higher risk of post extubation hypoxemia and need for reintubation)
   1. P/F ratio at 24 hrs (primary end point) significantly higher in HFNC group (287 vs 247). P/F also higher at 36 and 48 hrs in HFNC group
   2. Patient comfort significantly higher in HFNC group
   3. Significantly fewer reintubations in HFNC group (4% vs 21%) although the study was not powered for this outcome

1. 1. A new trial was just published on the use of HFNC following extubation in patients felt to be at low-risk of post-extubation hypoxemia – Effect of Post-extubation HFNC vs Conventional Oxygen Therapy on Reintubation in Low-Risk Patients, JAMA 2016, Spain

1. Methods
   1. Inclusion
      1. Pts on mechanical ventilation >12 hrs who passed an SBT and were defined as low risk of reintubation by having all of the following (few patients in our MICU would meet these criteria)
         1. Age <65
         2. Not initially intubated for CHF

• Absence of mod-severe COPD

1. APACHE II <12
2. BMI <30
3. No known airway problems and low risk of developing laryngeal edema

• Adequate cough and requiring suctioning <2xs Q8hrs
• Not difficult to wean

1. Mechanical ventilation <7 days
2. <2 co-morbidities

2. Exclusions
   1. DNR
   2. Trach
   3. Hypercapnia during SBT
3. Intervention
   1. Immediately following extubation, pts were randomized to either
      1. HFNC x 24 hrs
         1. set at 10L/min and titrated up at 5L/min intervals until pts experienced discomfort
         2. FiO2 titrated to SpO2 >92%.
      2. Conventional oxygen applied through facemask or nasal cannula titrated to SpO2 >92% x 24hrs

• Primary outcome
  1. Need for reintubation at 72 hrs

1. Results
   1. 1739 pts ready to be liberated from the vent  527 randomized (vast majority excluded as they were high risk for reintubation)
   2. Patient characteristics
      1. Age ≈51
      2. Neurologic co-morbidity 7.6% in HFNC group and 12.9% in conventional O2 group (only significant baseline difference between the two groups)
      3. Time on vent ≈ 1-2 days
      4. ≈30% admitted with primary neurologic diagnosis and ≈47% had either scheduled or urgent surgery at admission (not a typical MICU population)
   3. Outcomes

1. In multivariable analysis, HFNC was independently and inversely associated with all-cause reintubation.
2. NNT to prevent 1 reintubation = 14

1. Conclusion
   1. Among patients felt to be at low risk for reintubation, the use of HFNC following extubation vs conventional O2 reduced the need for reintubation at 72hrs with a NNT of 14

Faculty Feedback

I asked Dr. Ben Singer, Assistant Professor of Medicine in the Division of Pulmonary and Critical Care, whether he felt the JAMA trial was practice changing.  A summary of his comments:

• Important to remember that supplemental O2 is not an entirely benign therapy.  In both animal models and studies of healthy controls, high levels of FiO2 have been found to promote lung injury.  Supplemental FiO2 after extubation should therefore be used thoughtfully.
• With this in mind, it is important to note that the majority of the patients in the trial were placed on mechanical ventilation for surgical or neurologic diagnoses (only 16% had a primary respiratory reason for mechanical ventilation).  This population is likely at lower risk of lung injury from prolonged high levels of FiO2 than a patient recovering from PNA or ARDS.  This may have biased the trial toward a positive result.  Interestingly, more patients in the conventional O2 arm of the trial had ARDS (4.2% vs 1.5%) – perhaps contributing to the higher rates of reintubation seen in the control arm.
• As noted above, the patient population in the trial is not representative of patients typically cared for in the MICU.  As a result, the positive results seen with post-extubation HFNC are not necessarily generalizable to MICU patients.
• There were 7 cases of laryngeal edema necessitating reintubation in the control arm and 0 cases in the HFNC arm.  This is likely just an artifact of randomization as it is hard to imagine HFNC preventing severe laryngeal edema.  If 5 of the severe laryngeal edema patients had been randomized to the HFNC arm, the results of the trial would not have been significant.
• The curves from Fig 2  look convincing as they immediately separate during the first 24 hrs (when HFNC is being used) and then become essentially parallel suggesting a real benefit from HFNC

• Important for housestaff to recognize that this trial excluded hypercapnic patients, a group where the evidence supports the up-front use of NIV following extubation.
• Overall this was a well performed and methodologically rigorous trial.  The results are provocative but limited by the unique patient population (largely healthy neurocritical care and surgical patients).  The trial highlights the need for a large randomized trial of HFNC following extubation in a more inclusive group of MICU patients

Take-home Points

• The use of HFNC following extubation may reduce the risk of reintubation when compared to conventional O2.  Further trials are needed to clarify which patients stand to benefit most from this therapy.