Jet Nebulization of the Supine Patient: The Need for a Modified Front-loading Mask with a Swivel Adaptor and Curvilinear Connector.

Sir,

Gas-driven jet nebulization in patients in supine position in Intensive Care Units (ICUs) and operation theaters during acute respiratory events is usually done by “T”-piece nebulization[1] through the circuit while maintaining ventilation under general anaesthesia. But, improper aerosolization (drug gets accumulated on one side rather than at the base of chamber due to gravity) and drug spillage (drug chamber parallel to ground) with bottom-loading or partially front-loading masks [Figure 1a] is a major setback during jet-nebulisation in patients under regional anethesia in the OTs or in supine patients in ICUs. Trying to make chamber straight by turning patient's head to one side compromises mask fit and aerosol loss and may be contraindicated in specific ICU patients. Usage of multiple connectors between mask and chamber to straighten the chamber may cause turbulent flow and also drug condensation at angles [Figure 1c and d].

Figure 1

(a) Clear plastic face mask with jet nebulizer (chamber tilted may cause drug spillage, facial, and ocular drug deposition). (b) Front-loaded mask with connection to jet nebulizer (chamber straight and no drug spillage). (c and d) Swivel adaptor connector of mask connected to jet nebulizer, rotated to either side of patient as per convenience

The standard clear plastic face mask (Hudson mask) used along with jet nebulizers (gas-driven) is a bottom-loading type so that the jet reaches the nostrils [Figure 1a]. However, facial and ocular deposition of drug[2] with such masks due to aerosol inertia[3] is a well-known fact with side effects such as nebulizer associated anisocoria[4] and acute angle-closure glaucoma.[5] There are various other types of redesigned face masks manufactured, such as the Dragon aerosol face mask (Dragon Mask, KidsMED, Hinsdale, Indiana) and the Fish Aerosol Face Mask (Bubbles the Fish, Pari Respiratory Equipment, Monterey, California, USA), especially used in pediatrics for better seal and improved drug delivery to the patient,[3] while reducing the facial and eye deposition, especially with the latest bubbles the Fish II pediatric aerosol mask with ProVent technology. An adult version of such a mask is also available. This mask is front-loaded with an improved aerosol trajectory, i.e., the connector orifice is turned toward the mouth and nose of the patient rather than toward the upper-end of the face mask and the shape of the connector itself is curvilinear (improved trajectory with laminar flow) rather than straight. Lin et al.[3] in their study on face mask design on inhaled mass of aerosol albuterol had concluded that the Fish mask delivered a higher inhaled mass. The “Swirler” nebulizer[6] is used for ventilation/perfusion imaging with 99Tcm-diethylenetriaminepentaacetic acid aerosol and not for aerosolization of respiratory drugs in acute conditions.

With this background, we suggest that in a supine patient, gas-driven jet nebulization may be improvised by a similar mask such as the Fish aerosol face mask (front-loading), but with a swivel-adaptor connector orifice (as in the noninvasive ventilation mask [Figure 1b]) leading to a rotatable curvilinear connector which can be faced laterally toward one side instead of facing downward, so that the patient can still be nebulised in supine position, as well as on either side of the patient's head as per convenience [Figure 1c and d]. Such a mask is not available at present and the authors suggest the requirement for manufacturing of such a mask. Advantages of such a design would be better drug delivery by drug trajectory facing toward nose/mouth (front-loading), lesser facial and ocular deposition of drug, no drug spillage due to chamber tilting, no need for lateral rotation of head or holding the mask by hand while trying to maintain a better fit, and at the same time not having multiple angled connections as the “T”-piece nebuliser which may cause turbulent flow and drug condensation at the angles of connectors [Figure 1b–d].

Combination of this type of face mask with the swivel adaptor with rotatable curvilinear connector (as in Fish aerosol face mask) is an added advantage as it becomes less cumbersome in delivering aerosol drug in patients intraoperatively under regional anesthesia with central neuraxial blockade (where head elevation position for aerosol delivery may interfere with level of blockade, hemodynamics, and even the surgical procedure). The flow in a curvilinear connector is less turbulent. The anesthesiologist would be hands free to handle other important activities in the operation theater, rather than holding an ill-fitting mask and trying to prevent drug spillage from the nebulizer chamber. In the ICUs, it may be most useful in patients restricted to supine position, such as cervical spine injury patient, where positional changes of head for nebulization may be deleterious.

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Conflicts of interest

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