Continuous capnography monitoring during transport of critically ill patients

Jia et al. [1] should be congratulated for their large prospective multi-centre observational study to identify the incidence and risk factors of adverse events (AEs) during intra-hospital transport (IHT) of critically ill patients. They a priori categorised the AEs associated with the transfer process into equipment related AEs (E-AEs) and those affecting patient stability (P-AEs). About 44 % (196) of the patients were receiving invasive ventilation during IHT. Although the overall incidence of reported AEs is high (79.8 %), the E-AEs (disconnection/depletion of oxygen supply, loss of ventilator power) and P-AEs (accidental extubation, airway obstruction) were reportedly low. However, a significantly higher proportion had arterial blood gas analysis-related P-AEs with abnormal partial pressure of oxygen in arterial blood (PaO2) and partial pressure of carbon dioxide in arterial blood (PaCO2). Logistic regression analysis indicated that ventilation was not a risk factor for P-AEs, in contrast to the previously published literature. Unfortunately, none of the patients in the study were monitored with continuous capnography, which has been recommended as a standard of monitoring in mechanically ventilated intensive care unit (ICU) patients during IHT by European, Australasian and American guidelines [2]. Capnography also has the added potential of providing non-invasive measurement of cardiac output, physiological dead space and total CO2 production. Continuous capnography monitoring has now been recommended in all mechanically ventilated ICU patients [3]. The lack of continuous capnography monitoring in patients receiving invasive ventilation during IHT introduces a significant bias into the findings of the study by Jia et al.; it either underestimates the E-AEs, by failing to identify true E-AEs, or overestimates the P-AEs, reflected by the reported higher incidence of abnormal