Obesity hypoventilation and laminectomy

64-year-old male for L4 laminectomy. Cancelled in anaesthetic bay 3/12 ago with SpO2 85% and HCO3 37


  • Lower limb neurology due to spinal canal stenosis
  • OSA/OHS – New diagnosis after last attempted surgery
  • Now on BiPAP (IPAP 18, EPAP 10, backup RR 10), daytime SpO2 improved to ~90%, ESS reduced
  • Obesity BMI 44
  • Distant ex-smoker, nil COPD
  • Mild asthma, distant puffer use.
  • HTN
  • AMI 2014, medical mx, now discharged from cardiologist care


  • unoptimised OHS?
  • ABG in clinic – PaCO2 55, PaO2 63, HCO3 30


  • Should procedure be postponed?
    • Significant lower limb neurology, neurogenic claudication, and numbness
  • Possible optimisation
    • May require O2 addition to BiPAP to further stimulate respiratory drive (although recent overnight oximetry shows SpO2 ~90% on average). 
    • Consultation and further adjustment of BiPAP may be possible while inpatient post-operatively
    • TTE to assess for cor-pulmonale due to OHS (difficult to assess due to limited mobility due to lower limb neurology, obesity, and chronic lower limb oedema).


  • TTE
  • Proceed with OT
  • Respiratory AT agrees with plan to proceed and asked to be notified on admission so that they can provide input postop.