Chronic Respiratory Failure (Diagnosis of the Month) - Mercy Medical Center

Chronic Respiratory Failure (Diagnosis of the Month)

Posted on: November 27, 2018

Chronic respiratory failure is caused by abnormalities of oxygenation and carbon dioxide elimination due to chronic lung disease.

Classification of chronic respiratory failure:

    • Hypoxic
    • Hypercapnic
    • Unspecified

Common causes of chronic respiratory failure:

    • Severe COPD
    • Pulmonary fibrosis
    • Interstitial lung disease
    • Cystic fibrosis

Diagnostic Criteria:

    • Hypoxemia of variable severity (often with baseline pO2 <60 on room air)
    • Elevated pCO2
    • Elevated bicarbonate level 
    • Normal pH (7.35-7.45)         

Dependence on continuous home oxygen is an important indicator of chronic hypoxic respiratory failure. Patients who qualify for continuous home O2 have a baseline pO2 <60 (SpO2 <91%) on room air.

If continuous home O2 is documented in the medical record, then chronic respiratory failure should be documented also.

Acute on Chronic Respiratory Failure

An acute exacerbation or decompensation of chronic respiratory failure is recognized by any of the following:

  • pCO2 >50mm Hg + pH <7.35
  • Increase in baseline pCO2 (if known) by 10mm Hg or more
  • pO2 <60 mmHg or SpO2 <91% on the patient’s usual home oxygen flow rate or higher     
  • Worsening dyspnea requiring an increase in chronic supplemental oxygen
  • Greater hypoxemia: decreased pO2 or SpO2 from baseline (if known)

(Pinson & Tang, 2018, p. 155)

In general, one of the most helpful things to look for is if a patient requires more than their baseline FiO2, e.g. patient usually is on 2L O2 at home, which had to be increased to 4–5L during an admission.

* Please note that an acute exacerbation of COPD in a patient with chronic respiratory failure does not by itself constitute a diagnosis of acute on chronic respiratory failure. The patient should meet one of the criteria indicated (left) in order to be given the acute respiratory failure diagnosis.  


Pinson, R.D. & Tang, C. L. (2018).  CDI Pocket Guide. Middleton, MA: HCPro.


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