| Age yrs | 68±13 |
| Males/females | 41/8 |
| Mechanical ventilation time days | 7±5 |
| APACHE II score | |
| Admission | 17±7 |
| Study entry | 10±4 |
| Underlying diseases | |
| Chronic respiratory disorders# | 33 (67) |
| COPD | 23 |
| Non-COPD | 10 |
| Chronic heart disorders¶ | 13 (26) |
| Immunosuppression+ | 7 (14) |
| Diabetes mellitus | 12 (24) |
| Reason for initiating mechanical ventilation | |
| Exacerbation of chronic respiratory disorders | 13 (27) |
| Congestive heart failure | 6 (12) |
| Pneumonia | 6 (12) |
| Sepsis | 5 (10) |
| Post-operative respiratory failure | 2 (4) |
| Neurological disease | 2 (4) |
| Other causes | 15 (31) |
Data are presented as mean±sd, n or n (%), unless otherwise stated. n=49. APACHE: Acute Physiology and Chronic Health Evaluation; COPD: chronic obstructive pulmonary disease. #: including COPD, chronic bronchitis associated with dyspnoea and current or former history of smoking in the absence of pulmonary function testing, sequelae of pulmonary tuberculosis, chest wall deformity or obesity associated with a restrictive ventilatory disorder, and bronchiectasis; ¶: including coronary artery disease, hypertensive or valvular heart diseases, and dilated myocardial disease of any cause; +: including neutropenia after chemotherapy or bone marrow transplantation, drug-induced immunosuppression in solid-organ transplantation, or as a result of corticosteroid or cytotoxic therapy, and HIV-related disorders.