Do simple ventilation and gas exchange measurements predict early successful weaning from respiratory support in unselected general intensive care patients?

Monaco, F; Drummond, G B; Ramsay, Pamela; Servillo, G; Walsh, Timothy S

Abstract

Background. The value of respiratory variables as weaning predictors in the intensive care unit (ICU) is controversial. We evaluated the ability of tidal volume (Vtexp), respiratory rate ( f ), minute volume (MVexp), rapid shallow breathing index ( f/Vt), inspired–expired oxygen concentration difference [(I–E)O2], and end-tidal carbon dioxide concentration (PE′CO2) at the end of a weaning trial to predict early weaning outcomes.
Methods. Seventy-three patients who required .24 h of mechanical ventilation were studied. A controlled pressure support weaning trial was undertaken until 5 cm H2O continuous positive airway pressure or predefined criteria were reached. The ability of data from the last 5 min of the trial to predict whether a predefined endpoint indicating discontinuation of ventilator support within the next 24 h was evaluated.
Results. Pre-test probability for achieving the outcome was 44% in the cohort (n¼32). Non-achievers were older, had higher APACHE II and organ failure scores before the trial, and higher baseline arterial H+ concentrations. The Vt, MV, f, and f/Vt had no predictive power using a range of cut-off values or from receiver operating characteristic (ROC) analysis. The [I–E]O2 and PE′CO2 had weak discriminatory power [areaunder the ROC curve: [I–E]O2 0.64 (P¼0.03); PE′CO2 0.63 (P¼0.05)]. Using best cut-off values for [I–E]O2 of 5.6% and PE′CO2 of 5.1 kPa, positive and negative likelihood ratios were 2 and 0.5, respectively, which only changed the pre- to post-test probability by about 20%.
Conclusions. In unselected ICU patients, respiratory variables predict early weaning from mechanical ventilation poorly.

Citation

Monaco, F., Drummond, G. B., Ramsay, P., Servillo, G., & Walsh, T. S. (2010). Do simple ventilation and gas exchange measurements predict early successful weaning from respiratory support in unselected general intensive care patients?. British Journal of Anaesthesia, 105, 326-333. https://doi.org/10.1093/bja/aeq184

• Journal Article Type: Article
• Acceptance Date: May 19, 2010
• Publication Date: May 19, 2010
• Deposit Date: Jun 29, 2016
• Print ISSN: 0007-0912
• Electronic ISSN: 1471-6771
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 105
• Pages: 326-333
• DOI: https://doi.org/10.1093/bja/aeq184
• Keywords: Blood gas analysis; capnography; continuous positive airway pressure; mechanical ventilation; positive pressure ventilation; PEEP; pulmonary gas exchange; ventilator weaning
• Public URL: http://researchrepository.napier.ac.uk/id/eprint/10393
• Publisher URL: http://dx.doi.org/10.1093/bja/aeq184