Background: In respiratory failure due to COPD and cardiogenic pulmonary edema, noninvasive positive pressure ventilation decreases need for intubation and improves mortality,1 while its utility in other scenarios such as ARDS and pneumonia has yet to be proven.1,2 We know that patients on NIV with delays to needed intubation have a higher mortality,1,3 but intubation and mechanical ventilation come with risks that it is preferable to avoid if possible.
So how and when can we determine that NIV is not working?
The HACOR (Heart rate, Acidosis, Consciousness, Oxygenation, Respiratory rate) score at 1 hour after NIV initiation has been demonstrated to be highly predictive of NIV failure requiring intubation.4,5
Initial development/validation: Score > 5 after 1 hour of NIV corresponds to >80% risk of NIV failure4
Earlier intubation (before 12 hours) in these patients = better survival
External validation: Score > 8 after 1 hour of NIV most predictive of eventual NIV failure 5
Average score @ 1-hour of patients with NIV success = 3.8
Score remained predictive at 6, 12, 24, 48 hours as well & mortality worsened as delay to intubation time increased
Baseline, pre-NIV score not predictive
Better predictive agreement in pneumonia and ARDS
Bottom Line:
Patients on NIV require close reassessment to prevent worsened survival due to intubation delay should invasive mechanical ventilation be indicated.
A HACOR score >8 after 1 hour of NIV should prompt intubation in most instances, with strong consideration given to a score >5.
*Note: ABGs were obtained for PaO2 assessment in the above studies -- the use of SpO2 was not evaluated -- but we are often not obtaining ABGs in our ED patients with acute respiratory failure. The following chart provides an estimated SpO2 to PaO2 conversion.
WHO 2001
Caveats:
