How should the therapist instruct a patient to perform a Valsalva maneuver for the assessment of respiratory mechanics?

A. Have the patient pant rapidly just above and below normal tidal breathing for 12 seconds.
B. Instruct the patient to exhale as rapidly and as forcefully as possible against a closed glottis for several seconds.
C. Teach the patient to perform an inspiratory maneuver, similar to sucking on a straw, for several seconds.
D. Coach the patient to breath hold for approximately 10 seconds.

?ANS: B
A. Incorrect response: Having the patient pant rapidly just above and below normal tidal breathing for 12 seconds is essentially a maximum voluntary ventilation maneuver.
B. Correct response: A Valsalva maneuver is performed by instructing the patient to make a maximum and forceful expiratory maneuver against a closed glottis for several seconds. This maneuver causes a decreased stroke volume and reduces the cardiac output because it elevates the pleura pressure.
C. Incorrect response: Having the patient pant rapidly just above and below normal tidal breathing for 12 seconds is not used to evaluate breathing mechanics.
D. Incorrect response: Breath holding for 12 seconds is not part of the Valsalva maneuver.