NIV – Acute Hypercapnic Respiratory Failure

Last Updated on by frcemuser


  • COPD: pH < 7.35 AND PaC02 ≥ 6.5 RR > 23 despite one hour of medical management
  • Neuromuscular Disease:  Respiratory illness with RR >20 if usual VC <1L or pH < 7.35 AND PaC02 ≥ 6.5
  • Obesity: pH < 7.35 AND PaC02 ≥ 6.5, RR > 23 or daytime PaC02 ≥ 6.0 and drowsy

NIV is not usually indicated in Asthma/ Pneumonia

Contraindications to NIV


  • Severe facial deformity
  • Facial burns
  • Fixed upper airway obstruction


  • pH <7.15
  • pH <7.25 and additional adverse features
  • GCS <8
  • Agitation/confusion
  • Cognitive impairment

Initial setting

  • EPAP : 3 ( higher if OSA)
  • IPAP: 15 (20 if PH and EPAP: 4 (higher in OSA)
  • Increase IPAP over 10-30 minutes to 20-30 cmH20 (IPAP to not exceed 30 Or EPAP 8)

Alter NIV settings: 

PaC02 Remains High: Persistent respiratory acidosis

  • Is there too much oxygen? adjust Fi02 to target sat 88•92%.
  • IS there leak? Should be Consider total mask.
  • IS the patient rebreathing? Check the expiratory port is not occluded.
  • Is the patient spending long enough on the machine? Address compliance issue
  • Is the IPAP high enough? increase tidal volume (TV) by increasing IPAP
  • Look at pervious used on previous admissions.

Paco2 Improved but Pa02 Low: Target Pao2 7

  • Reassess for clinical deterioration; consider pneumothorax, aspiration , mucus pluging
  • Increase Fi02
  • Increase EPAP  (remember you may need to increase IPAP to maintain TV)
  • Consider senior review/ICU


  • Arterial blood gas (ABG) analysis should be performed at baseline, 1 hour after commencing NIV, 4 hours after commencing NIV, and 1 hour after changing any settings

Red flag

  • If pH < 7.25 on optimal NIV, RR >25 continuously or new-onset confusion -> clinical review.
  • Check synchronisation, mask fit, exhalation port. Consider chest physio, bronchodilators, anxiolytics, ICU

indication for ICU referral:

  • AHRF (Acute Hypercapnic Respiratory Failure) in Asthma
  • AHRF with impending respiratory arrest
  • NIV treatment failure: decreased chest wall movement, unable to decrease PaC02
  • Inability to maintain target Sp02 on NIV
  • Need for IV sedation, closer monitoring
  • +/- possible difficult intubation

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