Always check the patients equipment and interface.Consider: Poor mask fit/air-leak, FiO2 too high or incorrect equipment setup.If ABC and equipment setup are acceptable:Problem: If PCO2 remains high.Fix: Then increase IPAP by 2cmH20.Problem: If PO2 below target.Fix: Increase FiO2 or increase EPAP by 2cmH20.Problem: If increased work of breathing.Fix: Increase IPAP by 2cmH20.