Background There are several methods for apnea testing for the evaluation of neurological death, including oxygen via T-piece, oxygen cannula inserted into the endotracheal tube, and continuous positive airway pressure (CPAP). Lung suitability for transplantation is determined in part by the partial pressure of arterial oxygen (PaO2) to fraction of inspired oxygen (FiO2; P:F) ratio. We hypothesized that delivery of CPAP during apnea testing using a novel method would improve post-test P:F ratios.
Methods A retrospective review was performed at a level I trauma center for all patients undergoing apnea testing from 2010 to 2016. The CPAP system used a flow-inflating bag and was made available in 2012. It was used at the discretion of the clinician. Patients were classified as having an apnea test by CPAP or by non-CPAP method (T-piece, oxygen cannula in endotracheal tube, etc). The two groups were compared for baseline characteristics and the primary outcome of postapnea test P:F ratio.
Results During the study period, 145 patients underwent apnea testing; 67 patients by the CPAP method and 78 by non-CPAP method. There were no significant differences in demographics, mechanism of brain injury, pneumonia rate, smoking status, or antibiotic usage between the two groups. The pretest P:F ratio was similar between groups, but the CPAP group had significantly higher post-test P:F ratio (304 vs 250, p=0.02). There were no reported complications arising from CPAP use.
Conclusions We describe a novel method of delivering CPAP by a flow-inflating bag during examination for brain death. This method led to improved oxygenation, P:F ratios, and may decrease barotrauma. The flow-inflating bag was inexpensive, easily implemented, and without adverse effects. Multicentered, prospective trials are needed to elicit significant benefit in lung donation and transplantation.
Level of evidence Level IV, diagnostic tests.
- brain death
- continuous positive airway pressure
- lung function
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Contributors JLH and WLV designed the protocol and the study and did the data collection. RCD performed the statistical analysis. All authors participated in data interpretation. JLH wrote the manuscript, which all authors critically revised.
Disclaimer The content is the responsibility of the authors alone and does not necessarily reflect the views or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products, or organizations imply endorsement by the US Government.
Competing interests None declared.
Patient consent Obtained.
Ethics approval Local ethics committee in each of the participating centers.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement The only unpublished data are various clinical findings immediately before, during, and after apnea testing. Only the authors have access to the data.
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