Visual Obstruction of Flow Indicator Increases Inspiratory Volumes in Incentive Spirometry

Incentive spirometers were developed to facilitate sustained maximum inspiration. In addition to a slow-rising float that indicates volume displacement, the incentive spirometers includes a sensitive, rapid-fluttering flow indicator. Achieving the target inspiratory volume is believed to be the most important factor in successful incentive spirometers use. This investigation hypothesized that patients focus on the rapid fluttering of the flow indicator rather than volume float during incentive spirometers use. The effects of adjusting hand positioning to cover the flow indicator on inspiratory volumes were evaluated.

A randomized, prospective, counter-balanced crossover analysis of postoperative subjects was completed. In alternating assignment, the subjects were randomized to 1 of 2 study groups: (A) with the flow indicator covered first followed by the flow indicator standard exposed, and (B) with the flow indicator standard exposed first, followed by the flow indicator covered. The subjects were asked to perform 2 inhalations on their incentive spirometers in the first flow indicator condition: covered or the standard exposed. After a 2-min delay, the subjects were then asked to perform an additional 2 inhalations with the alternate flow indicator condition. The difference between mean inspiratory volumes under covered and standard exposed conditions was evaluated for all subjects, within and between groups.

A total of 42 subjects were evaluated. For all the subjects, there was a mean increase of 255.4 mL of inspired volume when the flow indicator was covered (1,869.0 vs 1,613.7 mL, P < .001). For the subjects in group B who had their flow indicators covered after standard exposure, mean inspiratory volumes increased by 285.7 mL (1,613.1 vs 1,898.8 mL, P = .009). For subjects in group A who had their flow indicator covered before standard exposure, their mean inspiratory volumes increased by 225.0 mL (1,614.3 vs 1839.3 mL, P = .007) when covered. There was no significant difference between the mean increases across patients in groups A and B (225.0 vs 285.7 mL, P = .63).

Covering the flow indicator during incentive spirometers significantly increased achieved inspiratory volumes. Increased volumes were generated, irrespective of flow indicator covering order, which strongly suggested that the covering effect was greater than any learning or condition order carry-over effects. Because achieving target inspiratory volumes is considered the most important factor in successful incentive spirometers use, these findings may have immediate applications for improving incentive spirometers protocols, patient education, and device design implications.