1. if the patients have a consistent spo2\<80% when on evaluation with a fio2 of 0.6, or signs of respiratory fatigue (rr \> 40/min, paco2\> 50mmhg / ph\<7.30, and obvious accessory respiratory muscle use); 2. immediate need for intubation (pao2/fio2\< 50mmhg or spo2/fio2 \<90, unable to protect airway or mental status change); 3. unstable hemodynamic status(sbp\<90mmhg, mbp below 65 mmhg or requirement for vasopressor); 4. unable to collaborate with hfnc/pp with agitation or refuse hfnc/pp. 5. chest trauma or any contraindication for pp 6. pneumothorax 7. age \< 18 years

1. if the patients have a consistent spo2\<80% when on evaluation with a fio2 of 0.6, or signs of respiratory fatigue (rr \> 40/min, paco2\> 50mmhg / ph\<7.30, and obvious accessory respiratory muscle use); 2. immediate need for intubation (pao2/fio2\< 50mmhg or spo2/fio2 \<90, unable to protect airway or mental status change); 3. unstable hemodynamic status(sbp\<90mmhg, mbp below 65 mmhg or requirement for vasopressor); 4. unable to collaborate with hfnc/pp with agitation or refuse hfnc/pp. 5. chest trauma or any contraindication for pp 6. pneumothorax 7. age \< 18 years

if the patients have a consistent spo2<80% when on evaluation with a fio2 of 0.6, or signs of respiratory fatigue (rr > 40/min, paco2> 50mmhg / ph<7.30, and obvious accessory respiratory muscle use); immediate need for intubation (pao2/fio2< 50mmhg or spo2/fio2 <90, unable to protect airway or mental status change); unstable hemodynamic status(sbp<90mmhg, mbp below 65 mmhg or requirement for vasopressor); unable to collaborate with hfnc/pp with agitation or refuse hfnc/pp. chest trauma or any contraindication for pp pneumothorax age < 18 years

if the patients have a consistent spo2<80% when on evaluation with a fio2 of 0.6, or signs of respiratory fatigue (rr > 40/min, paco2> 50mmhg / ph<7.30, and obvious accessory respiratory muscle use); immediate need for intubation (pao2/fio2< 50mmhg or spo2/fio2 <90, unable to protect airway or mental status change); unstable hemodynamic status(sbp<90mmhg, mbp below 65 mmhg or requirement for vasopressor); unable to collaborate with hfnc/pp with agitation or refuse hfnc/pp. chest trauma or any contraindication for pp pneumothorax age < 18 years

1. if the patients have a consistent spo2<80% when on evaluation with a fio2 of 0.6, or signs of respiratory fatigue (rr > 40/min, paco2> 50mmhg / ph<7.30, and obvious accessory respiratory muscle use); 2. immediate need for intubation (pao2/fio2< 50mmhg or spo2/fio2 <90, unable to protect airway or mental status change); 3. unstable hemodynamic status(sbp<90mmhg, mbp below 65 mmhg or requirement for vasopressor); 4. unable to collaborate with hfnc/pp with agitation or refuse hfnc/pp. 5. chest trauma or any contraindication for pp 6. pneumothorax 7. age < 18 years

1. if the patients have a consistent spo2<80% when on evaluation with a fio2 of 0.6, or signs of respiratory fatigue (rr > 40/min, paco2> 50mmhg / ph<7.30, and obvious accessory respiratory muscle use); 2. immediate need for intubation (pao2/fio2< 50mmhg or spo2/fio2 <90, unable to protect airway or mental status change); 3. unstable hemodynamic status(sbp<90mmhg, mbp below 65 mmhg or requirement for vasopressor); 4. unable to collaborate with hfnc/pp with agitation or refuse hfnc/pp. 5. chest trauma or any contraindication for pp 6. pneumothorax 7. age < 18 years