Modified O2 insufflation device shows promise for ventilatory support

The modified Rapid-O2 oxygen insufflation device^TM (Rapid-O2) provides sufficient minute volumes (MV) in adults using a 14-gauge (G) inner catheter or 2-mm inner-diameter transtracheal catheter (ID TTC) at 15 L/min, demonstrating its potential for ventilation in cannot intubate, cannot oxygenate (CICO) events.

Rapid-O2 is a rescue oxygenation device used in CICO events or near-total airway obstruction (AO) comprising a T-connector with extension tubing. It can be used as a rescue and temporary manoeuvre to oxygenate a patient while a more secure and permanent airway is being established. [Anaesth Intensive Care 2019;47:553-560]

“To improve ventilation, the Rapid-O2 was modified to generate high-velocity gas flow and create sub-atmospheric pressure via the Venturi effect through a small-bore catheter during expiration,” the researchers said.

At a lung compliance level of 100 mL/cmH₂O, MVs obtained at an oxygen flow rate of 15 L/min were 3.84 L/min with a 14G and 4.74 L/min with a 2-mm ID TTC. These were slightly higher than those achieved at a lung compliance level of 50 mL/cmH₂O at 12 L/min (3.8 and 4.72 L/min, respectively). [Korean J Anesthesiol 2025;78:61-72]

“These results show that, at normal lung compliance levels of 50–100 mL/cmH₂O, an MV of at least 4.5 L/min, when a 2-mm ID TTC was used, can be achieved even when an oxygen flow rate of 12 L/min was used,” the researchers explained. “Considering that the normal range of minute respiratory volume in adults is 5–8 L/min, the MV obtained with a 2-mm ID TTC at an oxygen flow rate of 12 L/min would be acceptable despite being slightly lower.”

“However, 14G and 2-mm ID TTCs are considered suitable for use at a rate of 15 L/min. These MVs would be sufficient not only for reoxygenation but also for preventing hypercarbia in adults,” they continued.

The researchers explained that in CICO or near-complete AO, inserting a small-bore catheter through the cricothyroid membrane can provide effective reoxygenation via jet ventilation. However, a high-pressure ventilator needs an open or partially obstructed airway to allow the release of insufflated gas during expiration to prevent barotrauma.

“Rapid-O2 … can also be used in such situations. However, passive expiratory outflow through a small-bore catheter is extremely prolonged due to [its] high internal resistance … Hence, ventilation might not be achievable,” they pointed out.

One strategy to facilitate gas egress through a small-bore catheter is by using the Venturi effect, which creates negative pressure during expiration. [Br J Anaesth 2010;104:382-386] According to the researchers, the modified Rapid-O2 was designed based on the Venturi effect to mitigate Rapid-O2-induced hypercarbia.

The findings suggest that the modified Rapid-O2 may be comparable to the only commercially available device used for CICO or near-complete AO in terms of MV and inspiration-expiration ratio. Moreover, it can be easily assembled using clinically available materials and is simple to use.

To establish the most effective combination of inner (20G, 18G, 16G, 14G, 2-mm ID TTC) and insufflation catheters (16G, 14G, 2-mm ID TTC) for achieving optimum ventilation, the researchers measured insufflating and expiratory flows at an oxygen flow rate of 15 L/min and insufflating and expiratory pressures at 6–15 L/min. MVs were obtained based on insufflating and expiratory times.

As this is a preliminary evaluation or an ‘in vitro proof-of-concept’ non-clinical study of a prototype device, the researchers called for in vivo studies to validate the findings.