We included 20 patients with ARF, defined as a blood
oxygen saturation (measured via pulse oximetry [SpO2
])
96% while receiving humidified oxygen via face mask,
with a fraction of delivered oxygen (FDO2
) of 0.5. The
exclusion criteria were: unstable clinical status (eg, marked
changes in respiratory variables in the 60 min prior to
inclusion in the study); need for endotracheal intubation;
decreased consciousness (Glasgow coma scale 14); severe
hemodynamic instability despite fluid therapy and
vasopressors; severe failure of 2 organs apart from respiratory
failure; pregnancy; and lack of patient cooperation.
The study was approved by the ethics committee of our
center, and patients gave their informed consent to participate.