The apnea test for brain death determination: an alternative approach

Neurocrit Care. 2004;1(3):363-6. doi: 10.1385/ncc:1:3:363.


Introduction: Problems associated with the standard apnea test relate to overshooting or undershooting the target PaCO2, potentially compromising the viability of organs for transplantation or invalidating the test.

Materials and methods: In 60 adult patients, the authors used an alternative method using exogenously administered CO2 and measurement of end-tidal CO2.

Results: All patients achieved an adequate respiratory stimulus (mean increase in PaCO2 was 28+/-3 mmHg, postapnea test pH was 7.20+/-.02). There was a clinically insignificant reduction in arterial blood pressure during testing, but no other complications occurred. Multiple regression analysis demonstrated a correlation between the predicted PaCO2 (predicted from the end-tidal CO2) and measured PaCO2 (64+/-9 versus 67+/-9; r=.75169, p<0.0001).

Conclusion: Exogenously administered CO2 as an alternative method for the standard apnea test was a reliable and safe method, with minimal complications that offers several advantages over the standard method.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Apnea*
  • Blood Gas Analysis
  • Brain Death / diagnosis*
  • Breath Tests
  • Carbon Dioxide / administration & dosage*
  • Carbon Dioxide / metabolism
  • Female
  • Humans
  • Male
  • Middle Aged
  • Partial Pressure
  • Respiration
  • Respiratory Function Tests / methods*


  • Carbon Dioxide