Criteria for use of noninvasive positive pressure ventilation(NPPV)
| Criteria for selecting severe asthmatic patients for NPPV trial# |
| Tachypnea with respiratory rate >25 breaths·min−1 |
| Tachycardia with fC >110 breaths·min−1 |
| Use of accessory muscles of respiration |
| Hypoxia with a Pa,O2/FI,O2 ratio >200 mmHg |
| Hypercapnia with Pa,CO2 <60 mmHg |
| FEV1 <50% pred¶ |
fC: cardiac frequency; Pa,O2: arterial oxygen tension; FI,O2: inspiratory oxygen fraction; Pa,CO2: arterial carbon dioxide tension; FEV1: forced expiratory volume in 1 s; % pred: % predicted. #: in the absence of absolute contraindication the presence of at least one criterion would suffice for an NPPV trial; ¶: FEV1 <50% pred after at least two consecutive nebulisations with salbutamol 2.5 mg and ipratropium 0.25 mg.