COPD exacerbation: acute respiratory failure: a low initial pH was associated with failure of non-invasive ventilation

Clinical bottom line (level 1b)

  1. One in five patients with COPD and acute respiratory failure failed non-invasive ventilation.
  2. The risk of failure was increased with a low initial pH.
Ambrosino et al: Thorax 1995; 59 : 755-757
Expires June 2004

The study

Inception cohort study with objective outcomes, adjusted for confounding factors, not validated in an independent set of patients.

Setting: acute hospital, Italy

47 patients (aged mean 65, % male) with 59 consecutive episodes of COPD and acute respiratory failure treated with non-invasive mechanical ventilation

Excluded if
  • relevant concomittant diseases


Factors studied:
  • age, sex, weight, serum albumin, pulmonary function, blood gases, cause of relapse, APACHE II score, neurological status, complciance with ventilation, heart rate


    Stepwise logistic regression analysis was used to adjust for confounding factors.

    100% followed for 2 hours

    Outcomes studied:
    • endotracheal intubation or death

      The evidence

      outcome time to outcome number of patients/total number %
      (95% CI)      		 NNF
      (95% CI)
      endotracheal intubation or death 2 hours 13/59 22%
      (12% to 33%)      		 5
      (3 to 9)

        • A low pH before initiation of ventilation was independently associated with failure of non-invasive ventilation.

      Citation

      1. Ambrosino N, Foglio K, Rubini F, et al: non-invasive mechanical ventilation in acute respiratory failure due to chronic obstructive pulmonary disease: correlates for success. Thorax 1995; 59 : 755-757
      Search Terms: from reference list of AHRQ review
      Contributor: Chris Ball, June 2002
      Reviewer:

      Clinical Question.
      Patient COPD exacerbation and acute respiratory failure
      Intervention or Exposure pH
      Outcome failure of non-invasive ventilation