An indigenous in-line metered dose inhaler actuation device.

Sir,

Aerosolized bronchodilator therapy is the mainstay of treatment for the management of perioperative bronchospasm in reactive airway disease. Pressurized metered-dose inhalers (pMDIs) are routinely used for this purpose. Even in critical care setting, delivery of bronchodilators and steroids with pMDIs in mechanically ventilated patients has been used increasingly in recent years.[1] The use of pMDIs has several advantages over small volume nebulizers such as cost effectiveness, ease of administration, less time consumption, reliability of dosing, and a lower risk of contamination.[2]

pMDIs were actually never designed for inhalation therapy to mechanically ventilated patients, thus their adaptation for this purpose involved substantial modifications. For pMDIs to be used in ventilator-supported patients, actuation devices that could be connected in closed, pressurized circuits were required.[3] These devices range from simple adaptors with a port, for example, 22 mm male–22 mm female connector with an MDI insert (Intersurgical Ltd, UK) and single nozzle to more complex spacer chambers (Smiths Medical, Portex®).[4] During a brief period of nonavailability of such commercially available devices in our institution, we decided to create our own indigenous in-line pMDI actuation device. We took a standard 15 mm M/15 mm F elbow connector (which is itself a part of the anesthesia or ventilator circuit) [Figure 1]. We modified it by creating a conical hole (with base of the cone at the surface) in its wall at the angle part, facing the 15 mm F end. This was done using a stainless steel (SS) one inch long, 2.5 mm diameter tapered self-tapping screw [Figure 2]. The elbow adaptor was marked on its convexity diametrically opposite to the 15 mm F end with a No. 11 surgical blade. Then, the “tapered SS screw” was screwed on this mark till its advancing tapered end went through the wall of the elbow connector. The screw was subsequently removed leaving behind a through-n-through conical hole in the wall of the elbow connector [Figure 3].

Figure 1

Elbow connector (15 M/15 F)

Figure 2

Through hole created by drilling a conical screw in direction of the patient's airway

Figure 3

Conical through hole with 2.5 mm as maximum diameter at base

During aerosol therapy to the patient, this modified elbow connector can be attached between the standard endotracheal tube universal connector and the Y-connector [Figure 4]. The nozzle of the pMDI canister can then be fitted into the conical hole, and the pMDI can be actuated synchronized with inspiration for direct drug delivery to the tracheobronchial tree [Figure 5]. In vitro studies have shown that aerosol drug delivery to the lower respiratory tract ranges from 0.3% to 97.5% with pMDIs.[5] This wide variation in drug delivery can be attributed to various factors such as ventilator mode and settings, heat and humidification of the inspired gas, density of inhaled gas, size of endotracheal tube, and method of connecting pMDI in the ventilator circuit.[2] Thus, a correct technique of administration is essential for successful aerosol therapy using pMDIs. The optimal technique for drug delivery by pMDI in ventilated patients is as follows:[13]

Figure 4

Administration of aerosol therapy to the patient using the modified elbow connector

Figure 5

Metered-dose inhaler canister mounted at the conical thro’ hole with 2.5 mm as maximum diameter at base

Assure tidal volume >500 ml (in adults) during assisted ventilation

Remove excess secretions

Shake pMDI vigorously

Place pMDI in adaptor in ventilatory circuit

Coordinate pMDI actuation with beginning of inspiration

Allow a breath hold at end inspiration for 3–5 s

Allow passive exhalation

Wait at least 15s between actuations; administer total dose.

With the help of our indigenous in-line pMDI actuation device and following the above-mentioned technique of administration, we have been able to manage perioperative bronchospasm successfully as well as deliver aerosol therapy easily and effectively to critically ill patients.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.