Final answer:
The greatest positive response to the nurse's use of caring touch in the form of a backrub is when the client falls asleep shortly after the backrub.
Step-by-step explanation:
The greatest positive response to the nurse's use of caring touch in the form of a backrub is when the client falls asleep shortly after the backrub. When a client falls asleep, it indicates a deep level of relaxation and trust in the nurse's touch. This response suggests that the backrub was effective in promoting relaxation and helping the client feel comfortable and at ease.
The other client reactions mentioned are also positive, but they do not indicate the same level of relaxation and positive response as falling asleep. When the nurse observes the client smiling, it suggests that the client is enjoying the backrub and finding it pleasant. Feeling the client's back muscles relaxing is another positive response, indicating that the backrub is helping to release tension and promote relaxation. Lastly, when the client tells his wife that the nurse is nice, it suggests that the client perceives the nurse positively, but it may not directly reflect the physical effects of the backrub.