Table A [Posted as supplied by authors.] Characteristics of trials included in the review. All trials used randomised allocation of treatment and were of parallel group design. (Reference numbers refer to the full version of the paper.)
 

Study	Included patient characteristics	NPPV intervention	Comparison with UMC
Avdeev et al19	58 adult patients (29 in each group). NPPV group means: pH = 7.28, age = 63.4 yrs, FEV1 = 0.68 L, M/F ratio = 26/3. UMC group means: pH = 7.26, age = 66.2 yrs, FEV1 = 0.74 L, M/F ratio = 22/7.	BiPAP ventilators used. Inspiratory positive airway pressure (IPAP) titrated to 30 cm H2O, expiratory pressure (PEEP) between 4-6 cm H2O. Both face and nasal masks used. Mean duration of NPPV was 29 hours (SD 25). Conducted on an intermediate care unit.	Usual medical care (UMC) included oxygen, bronchodilators, steroids and theophylline.
Barbe et al16	24 adult male patients (10 in UMC, 14 in NPPV group). NPPV group means: pH = 7.34, age = 70 yrs, FEV1 = 36% predicted. UMC group means pH = 7.30, age = 65 yrs, FEV1 = 30% predicted.	BiPAP ventilators used with a mean IPAP of 14.8 cmH2O, PEEP set at 5 cmH2O. Nasal masks used. NPPV given for two 3-hour periods for 3 days on a hospital ward.	UMC included oxygen, bronchodilators and steroids.
Bott et al2	60 adult patients (10 in each group at each of the 3 centres). NPPV group means: pH = 7.34, age £ 80 yrs. UMC group means: pH = 7.33, age £ 80 yrs.	Volume-cycled NPPV used with nasal masks. NPPV was provided for median 7.63 hrs per day over 6 days. Conducted on the ward.	UMC included oxygen, bronchodilators, steroids, antibiotics, methylxanthines, doxapram and diuretics.
Brochard et al3	85 adult patients (42 in UMC & 43 in NPPV group). NPPV group means: pH = 7.27, age = 71 yrs. UMC group means: pH = 7.28, age = 69 yrs.	Pressure support ventilation was initiated at 20 cm H2O. Patients underwent NPPV for at least six hours each day. Conducted in ICU.	UMC included oxygen, bronchodilators, steroids, methylxanthines, antibiotics, diuretics and heparin (sc).
Celikel et al14	30 adult patients (15 in each group). NIPPV group means: pH = 7.27, FEV1 = 1.03 L. UMC group means: pH = 7.28, FEV1 = 1.00 L.	Pressure support ventilation was initiated at 15 cm H2O, with 5 cmH2O of PEEP. Full-face masks used. Mean duration of NPPV was 26.7 hours (SD 16.1). NPPV was conducted in ICU.	UMC included oxygen, bronchodilators, steroids, antibiotics and theophylline.
Dikensoy et al20	34 adult male patients (17 in each group). NPPV group means: pH = 7.28, age = 65.1 yrs, FEV1 = 37.9% predicted. UMC group means: pH = 7.29, age = 64.2 yrs, FEV1 = 42.2% predicted.	BiPAP ventilators were used with an initial IPAP of 9 cmH2O, and a fixed PEEP set at 1 cmH2O. Mean duration of NPPV was 11.2 hr (SD 9.5). Full-face masks were used. Study was conducted on general medical ward.	UMC included oxygen, salbutamol, ipratropium bromide, prednisolone 1mg/kg/day i.v., aminophylline infusion 0.5mg/kg/day i.v., enoxaparin sodium 20mg/day s.c. and antobiotics if indicated.
Kramer et al17	23 patients. Mixed group of patients, outcomes for COPD patient presented separately (11 in NPPV group & 12 in UMC group). NPPV group means: pH = 7.27UMC group means: pH = 7.29.	BiPAP ventilators were titrated from an initial IPAP of 8 cmH2O to a maximum of 20 cmH2O. PEEP was set at 2 cm H2O. Nasal masks were used. Mean duration of NPPV was at least 8 hrs per day. Conducted in ICU or a step-down unit.	UMC included oxygen, bronchodilators, steroids and antibiotics.
Plant et al15	236 adult patients (118 in each group). NPPV group means: pH = 7.32 (median), age = 69 yrs, FEV1 = 0.71(median), M/F ratio = 54/64. UMC group means: pH =7.31 (median), age = 69 yrs, FEV1 = 0.68 (median), M/F ratio = 63/55.	BiPAP ventilators were used with IPAP initially set at 10 cmH2O and PEEP 4cmH2O. Both nasal and face mask were used. Median use of NPPV was 8hrs on day 1, 7hrs day 2 and 5hrs day 3. NPPV was conducted on the ward.	UMC included oxygen, bronchodilators, steroids, antibiotics, methylxanthines, and doxapram.