Jet Insufflator for cannot intubate cannot ventilate situation. An Indian Jugaad.

Sir,

A majority of children with difficult airways can be identified during pre-anaesthetic assessment. The reported incidence of difficult intubation in infants is 0.24%–4.7% and 0.07–0.7% in older children.[1] The incidence of cannot intubate cannot ventilate (CICV) is even lower. The debate between scalpel, small bore cannula and cannula over trocar is almost over as Difficult Airway Society (DAS) as well as All India Difficult Airway Association (AIDAA) guidelines for paediatric airway management recommend cannula technique in the absence of ENT surgeon for formal tracheostomy in the CICV situation. DAS guidelines recommend cannula <4 mm for the front of neck access while AIDAA recommends a 16 or 18 gauge intravenous cannula for the same.[12]

DAS and AIDAA guidelines recommend the use of jet ventilation devices with pressure regulators (e.g., Manujet III™ [VBM, Medizintechnik GmBH, Sula and Neckar, Germany]) for oxygenation once the cannula is appropriately placed in the trachea. However, these mechanical jet ventilation devices do not provide any room for egress of gases and tactile feedback.[3]

The Enk Oxygen Flow Modulator (Cook Inc, Bloomington, IN, USA) and the Rapid O2™ Insufflator (Meditech Systems Ltd, Shaftesbury, UK) have demonstrated safer expiratory profile as compared with the Manujet III™.[3] Their use is also supported by the advanced paediatric life support group.[4] However, none of these devices is available in India so far.

Hence, we improvised to make an oxygenation device using our existing Jackson-Rees (JR) circuit, a universal connector and 100 cm venous extension. JR circuits' machine end is connected to a flow meter from central oxygen supply or from an oxygen cylinder, and the bag and corrugated tubing are removed [Figure 1a]. The patient end is connected to a 4 mm ID endotracheal tube universal connector. A 10–15 cm portion of venous extension with Luer-lock connection in situ is attached to the universal connector [Figure 1b]. By occluding the free end of the T connector with the thumb, the oxygen gets directed to the patient [Figure 1c] and on releasing the thumb, the expired gases along with oxygen are vented out in atmosphere [Figures 1d and 2]. The inner diameter of the venous extension is 3 mm. It should be is large enough to provide adequate flow for chest expansion. As per Hagen-Poiseuille's law decrease in diameter will increase resistance and decrease flow. Flow meters regulate flow, but they do not regulate pressure. In contrast, Jet injectors regulate pressures with very high-flow rate till the pressures are equilibrated across the cannula. With increasing upper airway resistance and no exhalation possible through cannula, end-expiratory pressure increases. Oxygen delivery by jet is dependent on pressure difference, and no ventilation is possible once end-expiratory pressure reaches to set the highest pressure for ventilation. Pressures are equilibrated early across the cannula with jets injectors, but much slowly in our innovation because oxygen flow is considerably less compared to jet. Hence, the chances of barotrauma are decreased. We have tested this apparatus on test lungs.

Figure 1

Assembly and working of indigenous jet ventilation device. (a) Encircled part needs to be removed. Machine end (O) of Jackson-Rees Circuit connected to intermediate pressure oxygen source. (b) Sequential connection between A to B, C to D and E to Cannula (inserted into the trachea) completes the assembly. (c) Thumb occlusion of ‘T’ end leads to Inspiration and (d) on releasing expiration occurs

Figure 2

Occlusion of open end of the T-piece causes inspiration by directing fresh gas flow towards the patient. Expiration occurs once open end is released

Ventilation with this device is similar to the Rapid O2(illustrative videos are available online at Video 1 www.youtube.com). The single large opening similar to Rapid O2 Insufflator provides immediate tactile feedback to the thumb in the event of kinking of the catheter. This tactile feedback will also be able to detect the inadvertent migration of the catheter into the tissues surrounding the airway. Initial oxygen flow rate should be set at 1 L/min/year of age and then should be adjusted to achieve visible chest rise. Inspiration should be terminated once the chest expansion is seen, following which passive expiration will occur. Airway pressures cannot be monitored with our device, however, allowing adequate chest recoil (giving adequate time for expiration) can prevent breath stacking and subsequent barotrauma.

Although CICV situation is rare, airway clinicians must have equipment and training to rescue the airway should this emergency occur. It is not cost-effective to stock Manujets™ in locations where a CICV emergency could occur and practically not possible for our freelancer colleagues to carry another heavy equipment in their bags.

Low cost and light weight of our equipment make it ideal to stock in locations in hospital where CICV could occur and make it an ideal tool for freelancers who can prepare this equipment from their existing resources and use it as the need arises.

Video available on www.ijaweb.org

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.