Table 2—

Baseline vital signs and arterial blood gas results of the study patients at the time of randomisation

CharacteristicsPatients receivingp-value
Bi-level NPPVPlacebo
Subjects n1010
Heart rate beats·min−1122.4±22 (74–158)122±20 (95–150)ns
Respiratory rate breaths·min−136.7±10.3 (20–52)37.5±7.2 (24–47)ns
Added O2 L·min−13.8±3.5 (1–10)5.7±2.63 (1–8)ns
Arterial pH7.28±0.08 (7.1–7.39)7.24±0.11 (7.08–7.43)ns
Pa,CO2 mmHg56.3±16.5 (35–93)59.9±19 (45–102)ns
Pa,O2 mmHg78.3±37.2 (37–155)64.2±19.7 (41–92)ns
Sa,O2 %87.9±11.3 (61–96.1)83.5±12.1 (61–96.2)ns
Sp,O2 %89.1±8.3 (71–98)79.7±7.2 (50–96)ns
  • Data are presented as mean±sd (range)

  • ns: not significant

  • O2: oxygen

  • Pa,CO2: carbon dioxide tension in arterial blood

  • Pa,O2: oxygen tension in arterial blood

  • Sa,O2: arterial oxygen saturation

  • Sp,O2: transcutaneous Sa,O2 measured from a pulse oxymeter with a finger probe

  • NPPV: noninvasive positive-pressure ventilation

  • 1 mmHg=0.133 kpA