Useful tip on nebulisation technique

There is a very good reason why whenever a prescription is written for "Salbutamol 5mg by nebulisation" the healthcare staff should select two(2) vials of the Salbutamol nebules 2.5mg/2.5mL strength, in preference to one(1) vial of the Salbutamol nebules 5mg/2.5mL strength.

Obviously in each case you get the nominal dose of Salbutamol 5mg prescribed, but a mechanical factor limiting the performance of nebuliser machines leads to different results. All available nebulisers suffer the limitation called "dead volume"; which is a fixed volume of solution which is left in the medication cup of the nebuliser after each procedure. This fixed volume of liquid medication cannot be picked up and aerosolised by the machine and is left behind.

This gives a margin of error to the actual dose of the drug that is discharged to the patient.

Nebuliser brands differ in the extent of the "dead volume", but let's assume a figure of 0.5mL in order to demonstrate its significance.

When a prescription for "Salbutamol 5mg by nebulisation" is written and two(2) vials of Salbutamol nebules 2.5mg/2.5mL is filled into the nebuliser, if you adjust for a dead volume of 0.5mL you get 4.5mg of the drug discharged to the patient. If the same procedure is performed by filling one(1) vial of Salbutamol nebules 5mg/2.5mL into the machine you obtain only 4mg of Salbutamol discharged to the patient.

The 0.5mg variation between the two procedures makes a lot of difference in inhalation therapy. Remember that usual prescribed dose for Salbutamol inhaler for an adult is only 0.2mg (200micrograms), meaning that 0.5mg (500micrograms) cannot be ignored.