FIG. 30: HOT-HMV was designed to look at acute respiratory failure exacerbations, according to the definitions listed in this Figure.[1,15] The trial looked at not only hospital admissions but also less severe exacerbations. The exacerbations were defined a priori as either COPD-related hospital admission, admissions for patients with symptoms of deterioration in COPD, or admission to hospital following a change in COPD therapy.

Also included were physician-assessed exacerbations, meaning exacerbations marked by a deterioration in COPD symptoms and an escalation of COPD therapy following a community review but not requiring hospital admission. Exacerbations could also be self-treated, ie, patients themselves noted a deterioration in lesser terms and initiated rescue pack therapy for management of their COPD, without a review by a healthcare professional.

Patients completed diary cards during the trial period. These were reviewed and assessed using a standard definition of a deterioration in COPD symptoms to define an untreated exacerbation when no change in COPD medication was initiated during the exacerbation period.

This system was hierarchical, so if the patient had an untreated exacerbation that was then self-treated and then reviewed by a physician, followed by hospital admission, this would count as one single exacerbation unless there was resolution of symptoms in between those stages.