Part 1: Using Clinical Cadavers we've tested various flow/PEEP combinations using a BVM and nasal prongs. In an apneic state using an aggressive mask-VE jaw thrust, 15 lpm via BVM and 10 lpm with NP we consistently get (apneic) CPAP alveolar recruitment without manual ventilation. An OPA is helpful but requires breaking your seal for placement which depending on timing and context may be an issue. These flows are necessary to 'charge' the PEEP valve because of the intrinsic flow decay via the BVM. Flows of 5 lpm through the NP were inadequate in our tests. Part 2: As we know de-recruitment occurs rapidly with loss of preoxygenation when flows are turned off or the mask seal is lost. See Mosier et al. Time to loss of preoxygenation. If the seal is broken to place an OPA or for some other reason re-oxygenation/recruitment should occur with breath to breath monitor-guided mask ventilation (pressure manometer and waveform CO2). Re-oxygenation/recruitment will most often occur within 3-5 carefully delivered breaths using a BVM/PEEP combination. After an RSI in the patient who begins to desaturate during the last phase of preoxygenation as they transition to apneic state should recieve monitor-guided mask ventilation.
