Final answer:
A spacer is the best option to help a client with difficulty coordinating breathing with an inhaler use, as it ensures better delivery of medication to the lungs.
Step-by-step explanation:
The client who is having problems coordinating his breathing with inhaler use would be best helped by using a spacer. A spacer is an attachment that can be added to an inhaler which makes it easier to use and helps to ensure that more medication reaches the lungs rather than being lost in the air or the back of the throat. It is especially useful for individuals who have difficulty timing their breaths with the release of medication from their inhaler. On the other hand, a turbo-inhaler is a type of inhaler that doesn't necessarily address the issue of coordination, nasal drops are for delivering medication to the nasal passages and not the lungs, and a metered-dose inhaler is likely what the client is already using and having trouble with. Therefore, the use of a spacer would be the most appropriate option to maximize drug absorption for the client.