Health-related quality of life: implications for critical care interventional studies and why we need to collaborate with patients.

Purpose of review: Health-related quality of life (HRQoL) is an important patient-reported outcome measure following critical illness. ‘Validated’ and professionally endorsed generic measures are widely used to evaluate critical care intervention and guide practice, policy and research. Although recognizing that they are ‘here to stay’, leading QoL researchers are beginning to question their ‘fitness for purpose’. It is therefore timely to review critiques of their limitations in the wider healthcare and social science literatures and to examine the implications for critical care research including, in particular, emerging interventional studies in which HRQoL is the primary outcome of interest. Recent findings: Generic HRQoL measures have provided important yet limited insights into HRQoL among survivors of critical illness. They are rarely developed or validated in collaboration with patients and cannot therefore be assumed to reflect their experiences and perspectives. Summary: Collaboration with patients is advocated in order to improve the interpretation and utility of such data. Failure to do so may result in important study effects being overlooked and the dismissal of potentially useful interventions.

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

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.