Hospitals are the usual location for the treatment of older patients with acute illnesses, such as pneumonia (lung infection), congestive heart failure (fluid in the lungs caused by problems with the heart's pumping ability), chronic obstructive pulmonary disease (lung disease often attributable to smoking), and cellulitis (skin infection). However, older patients who are hospitalized often experience complications of treatment, confusion, weakness, and loss of ability to care for themselves. Some small, preliminary studies suggest that it is possible to provide hospital-like care for these conditions in patients' homes. However, most previous studies used models of care more similar to typical skilled care services than to hospital care and were performed in countries with national health insurance.