<qa>  What is the risk of death for COPD patients?Patients with COPD or ARDS that require mechanical ventilation are at high risk of death either from their disease or from complications during critical illness. Those that survive the acute phase of their illness often require prolonged mechanical ventilation and often have difficulty weaning from ventilator support. While lung parenchymal abnormalities and deconditioning are significant components of this weaning failure, respiratory muscle strength, and potentially respiratory muscle blood flow, may play a role. 