Murphy - Figure 20
2 Weeks Following Resolution of Hypercapnic Acidosis
FIG. 20: It was important that we could show not only that the enrolled patients had persistent hypercapnia, but that they did not have persistent decompensation. So they needed to be assessed at ≥2 weeks after resolution of hypercapnic acidosis, thus demonstrating a persistent hypercapnia with a PaCO2 of >7 kPa and a pH of ≥7.30 for at least 2 weeks preceding the assessment.[1]
The HOT-HMV trial design also stipulated that patients should have chronic hypoxia, using standard criteria that would be accepted for the provision of long-term O2 therapy, ie, a PaO2 <7.3 kPa or <8 kPa with features of secondary organ injury due to hypoxia such as pulmonary hypertension, peripheral edema, or significant nocturnal hypoxia.
References
Murphy P, Arbane G, Bourke S, et al. Effect of home non-invasive ventilation with oxygen therapy vs oxygen therapy alone on hospital readmission or death after an acute COPD exacerbation: a randomized controlled trial. JAMA. In press.