Presented with O2 sat 81% to the ED, what's next?


Max flow through standard NC ~6L/min.

~3-4% increase in FiO2 per L, so 2L/min ~= 30% FiO2.

Minute ventilation ~5L/min if assume 10 breaths per minute, ~500mL tidal volume, but: - those are averaged over one minute - moment inspiration will exceed that flow rate, - the seal isn't perfect,

we're typically putting O2 on dyspneic people, so those assumptions typically do not hold.

Large-bore NC

Bigger tube, up to ~15L/min. Otherwise same as NC.

Venturi mask

Size of holes determines rough amount of entrainment.


One-way exhale valves, bag w 100% O2. Still getting some entrainment, but overall higher O2 delivered.


Optiflow, Airvo, etc.

Up to 60L, 100% FiO2. Humidified air, more complete seal on nose piece. Less complications from dry air (massive epistaxis), less entrainment (though depends on if their mouth is closed). Also provides up to ~5L PEEP.

Blends 100% O2 and medical air to achieve the set FiO2.

FLORALI trial - intubation rate between HFNC and NIPPV was not different (primary outcome) - ventilator free-days were different (higher in HFNC) - 90d mortality rate better for HFNC than NIPPV


Pressure increase (mean airway pressure), more O2 exchange d/t greater partial pressures of delivered O2 over more time.

Invasive ventilation

Next week…