Experimental adaptation of the Enk oxygen flow modulator for potential pediatric use

A bench study of the Enk oxygen flow modulator (Enk OFM) was conducted to test its performance and potential use in pediatric patients using the Advanced Paediatric Life Support (APLS) guidelines (Advanced Paediatric Life Support, 2005: 224).

The Enk OFM is a preassembled emergency transtracheal ventilation device.

The Enk OFM was connected to two sources of oxygen: first, to a Precision Medical flowmeter and second, to an Aestiva anesthetic machine axillary flowmeter. Testing was performed on standard cannulae of 20, 18, and 16 gauge caliber and also a 7.5 cm 15G Emergency Transtracheal Airway Catheter (Cook Medical). Serial hole occlusion of the Enk OFM was applied and the resulting flow rates were measured by a RespiCal Timeter.

Oxygen flow was best controlled by occluding all holes of the Enk OFM and incrementally increasing oxygen flow by the flowmeter with an initial setting of 1 l min(-1) year(-1) of age. Contrary to the original description of this device (Anesth Analg 1998; 86: 203S), sequential occlusion of the five side holes does not lead to a significant exponential increase in gas flow. Incomplete occlusion of the Enk OFM provided insufficient and unpredictable flow.

The Enk OFM should be fully occluded for inspiration with flow rates set at 1 l min(-1) year(-1) of age and adjusted to effect. These flow rates are consistent with the APLS recommendations. Flows above 15 l min(-1) are potentially dangerous and the Enk OFM fails to perform as an on-off device. Flowmeter settings of <1 l min(-1) risk no flow. Cannulae of at least 18G should be used for optimal flow.