Predictors of Success, Failure, And Need For Intubation In Noninvasive Ventilation From Emedicine

The section on Noninvasive Ventilation is outstanding.

This post continues excerpts from the Application of Noninvasive Ventilation webpage [the entire page should be reviewed].

The web page is very long and for my study and memory needs, I have broken the excerpts into several separate posts.

What follows are the Predictors of Success, Failure, and the Need For Intubation In Noninvasive Ventilation, Application of Noninvasive Ventilation webpage:

Predictors of successful noninvasive ventilation

Importantly, recognize that certain parameters may predict successful noninvasive ventilation or failure of noninvasive ventilation, so that patients are not subjected to continued treatment when optimal treatment requires intubation and mechanical ventilation. This includes changes during a trial of noninvasive ventilation. The changes, in turn, are a reflection of the patient’s ability to cooperate with noninvasive ventilation, patient-ventilatory synchrony, and noninvasive ventilation effectiveness. Trials of noninvasive ventilation are usually 1-2 hours in length and are useful to determine if a patient can be treated with noninvasive ventilation. Extended trials without significant improvement are not recommended because this only delays intubation and mechanical ventilation (unless patients are do-not-intubate status).

Predictors of success, with a response to a trial of NIV (1-2 h), are as follows:

  • Decrease in PaCO 2 greater than 8 mm Hg
  • Improvement in pH greater than 0.06
  • Correction of respiratory acidosis

Predictors of failure are as follows:

  • Severity of illness – Acidosis (pH <7.25), hypercapnia (>80 and pH <7.25), Acute Physiology and Chronic Health Evaluation II (APACHE II) score higher than 20
  • Level of consciousness – Neurologic score (>4 = stuporous, arousal only after vigorous stimulation; inconsistently follows commands), encephalopathy score (>3 = major confusion, daytime sleepiness or agitation), Glasgow Coma Scalescore lower than 8
  • Failure of improvement with 12-24 hours of noninvasive ventilation

Late admission predictors of failure (>48 h after initiation of noninvasive ventilation) are as follows:

  • Lower functional status (Activity score <2 = dyspnea light activity)
  • Initial acidosis (pH ≤ 7.22)
  • Hospital complications (pneumonia, shock, coma)

Certain patients may benefit from a trial of therapy; however, limiting trials is important to avoid delays in definitive therapy. Trials may be as short as a few minutes, in patients with immediate failure, and probably should not exceed 2 hours if patients fail to improve.

Objective criteria for discontinuation are important to limit trials in patients in whom noninvasive ventilation ultimately fails. This specifically refers to intubation criteria, which carry a subjective element but have been defined in the literature in investigational studies. All these criteria are subject to some degree of interpretation in the context of the patient’s clinical status. Importantly, recognize the following as guidelines to assist with the decision to intubate a patient. Most patients who meet these criteria are candidates for intubation, but a few may be able to be managed with continued noninvasive ventilation.

Intubation criteria

Major criteria (any one of the following) are as follows [8, 9] :

  • Respiratory arrest
  • Loss of consciousness with respiratory pauses
  • Gasping for air
  • Psychomotor agitation requiring sedation
  • Heart rate less than 50 bpm with loss of alertness
  • Hemodynamic instability with systolic blood pressure less than 70 mm Hg

Minor criteria (two of the following) are as follows:

  • Respiratory rate greater than 35 breaths/minute
  • pH less than 7.25 and decreased from onset
  • PaO 2 less than 45 mm Hg despite oxygen
  • Increase in encephalopathy or decreased level of consciousness

Intubation guidelines

Any one of the following [10] :

  • pH less than 7.20
  • pH 7.20–7.25 on 2 occasions 1 hour apart
  • Hypercapnic coma (Glasgow Coma Scale score <8 and PaCO 2 >60 mm Hg)
  • PaO 2 less than 45 mm Hg
  • Cardiopulmonary arrest

Two or more of the following in the context of respiratory distress:

  • Respiratory rate greater than 35 breaths/minute or less than 6 breaths/minute
  • Tidal volume less than 5 mL/kg
  • Blood pressure changes, with systolic less than 90 mm Hg
  • Oxygen desaturation to less than 90% despite adequate supplemental oxygen
  • Hypercapnia (PaCO 2 >10 mm increase) or acidosis (pH decline >0.08) from baseline
  • Obtundation
  • Diaphoresis
  • Abdominal paradox

See also:



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