This has appeared in the ancient Question 12 from the second paper of 2002. The candidates were asked to "compare and contrast the methods of delivery of beta-2 agonists in intubated patients". The college does not limit themselves to nebulisation; however this is the most common method, and will be the focus of this chapter.

LITFL has a good page about it, which does into some detail regarding the various types of nebuliser, and their relative merits.

Advantages of nebulized drug delivery

• Smaller dose than systemic administration
• Fewer systemic side effects due to decreased dose.
• Immediately available to the bronchial suface (an advantage for bronchodilators)
• Immediate onset of activity
• Bypasses first-pass metabolism

Problems with nebulising drugs in the ICU

• Some residual volume may remain in the delivery device
• The delivery to the lower airways is variable
• Manual bagging may be required to really "get it in there"

• Impossible with a HME: saturates the filter
• Delivery devices can add dead space and resistance
• Loss of PEEP can occur when circuits are broken to insert devices
• Amount of drug delivered to the site of maximum activity may be very small, due to the deposition of droplets on the plastic surfaces of artifical airways
• The pooling of droplets inside airway equipment may result in highly concentrated droplets, which - when they fall and are absorbed though the mucosa - make the dose rate erratic and unpredictable.
• Gas density affects the efficiency of drug delivery by aerosol particles. Lower viscosity gas mixtures, eg. 30/70 Heliox, are known to improve drug delivery to the alveoli and distal airways.

Available equipment

• Metered-dose inhalers
• Spacer devices
• Swivel tubing
• In-line ultrasonic nebulisers
• In-line jet nebulisers

Optimal technique

• Suction airway secretions
• Use warmed MDIs (not refrigerated)
• Coordinate MDI actuation with beginning of inspiration
  • Manual inspiratory bagging may be required
• Wait at least 15 s between doses

Other methods of administering bronchodilators

Prior to reading Question 12 from the second paper of 2002, I was not aware that beta-2 agonists could be given subcutaneously. Turns out, people have done this to infants, and "no local or general adverse reactions were observed".

A table of comparison is offered, as it is essentially the tabulated form of the college's own model answer.