UnknownAn small but elegant experimental study in CJA explores the impact of nasal passage occlusion on mask ventilation in the unresponsive patient. Tidal volumes may be reduced by more than half when the nose is totally occluded.

The study
A cross-over study on 20 healthy female patients who were due for elective surgery in general anaesthesia. Patients were 1:1 randomised to mask ventilation with either total nasal passage occlusion with a swimmers’ nose clip or with an open nasal passage. After having being placed in a standard induction sniffing position, the patients were anaesthetised using remifentanil and propofol followed by rocuronium.

Measurements started after confirming zero count response to TOF-stimulation. The primary outcome was the averaged  tidal volumes generated by mechanical ventilation at 10, 15, 20 cmH20. Other ventilator settings were 8 breaths per minute, I/E 1:2 and oxygen flow of 4L/min. After having obtained the first measurements the patients were crossed over to application or removal of the nose clip, respectively.

Screen Shot 2017-09-13 at 14.24.40In this study tidal volumes were reduced by as much as >6o%.

At 10 cmH20, application of the nose clip reduced mean tidal volumes from 300 (230-328) mL to 100 (55-135)mL.

At 20 cmH20, application of the nose clip reduced mean tidal volumes from 790 (713-823) mL to 270 (215-390] mL.

Take-home message
Nasal passage patency is of critical importance for mask ventilation in the unresponsive patient. Occlusion will greatly reduce tidal volumes generated by mask ventilation at any given pressure.  Patients with nasal occlusion, such as from max-fax trauma, may require higher airway pressures than you are normally comfortable with. It also underscores the importance og having and using nasopharyngeal airways.

Paper lives here:
Yamasaki T, Komasawa N, Kido H, Minami T.Contribution of the nasal passage to face mask ventilation: a prospective blinded randomizedcrossover trial. Can J Anaesth. 2017 Jun 16. doi: 10.1007/s12630-017-0911-3. 

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