comparison of different methods of ventilation via cannula cricothyroidotomy in a trachealung model background cannula cricothyroidotomy is recommended in recent guidelines as a rescue intervention in the cannotintubate cannotventilate scenario several methods of providing ventilation via a cannula cricothyroidotomy have been described but there are no data comparing these methods and using cannulae of differing diametersmethods using a benchtop trachealung model comprising a siemens test lung attached to commercially available breathing system tubing we compared delivered minute volumes mvs for five methods of ventilation administered through cannulae of diameters 20 16 14 and 13 g the ventilation methods were an enk oxygen flow modulator a manujet a selfinflating resuscitation bag the oxygen flush of an anaesthetic machine and oxygen from a wallmounted flow meter attached via a threeway tap to the cannula all experiments were performed with and without a proximal 25 mm diameter constriction to simulate partial upper airway obstructionresults mvs increased with increasing cannula diameter in the absence of a proximal constriction mvs delivered via a 20 g cannula were 2 litre min1 at cannula sizes of or16 g mvs were greater in the presence of a proximal constriction but did not exceed 4 litre min1 using the lowpressure devicesconclusions extrapolated to the clinical situation these data suggest that lowpressure devices will not deliver adequate mvs via a cannula cricothroidotomy and should no longer be advocated purposemade devices should be available in all areas where anaesthesia is administered or airway interventions are performed