Modified use of the Triflo II® incentive spirometer and its effects on feedback ball elevation, selective closure of air inlets, and inspiratory flow and pressure: A bench study

Background: The Triflo II® incentive spirometer (TF) is widely prescribed for lung expansion exercise, but its high inspiratory flow rate and short inspiratory time, leading to increased effort and lower tidal volume, are recognized limitations. Modifying its use may improve its effectiveness. Objectives: As an initial step before human studies, a bench test was conducted to evaluate inspiratory flow and pressure responses under controlled conditions. Materials and methods: A bench test was conducted under two conditions: (1) three target ball elevation levels were marked on the wall of each TF chamber, and airflow rate and pressure responses were evaluated during simulated airflow at each target level; and (2) selective closure of air inlets was performed by closing one or two of the three air inlet holes of the TF device, and the corresponding airflow rate and pressure responses were evaluated. Results: No significant differences were observed in the 900 mL/sec chamber. In the 600 mL/sec chamber, the fourth quarter had a significantly higher flow rate (652±6 mL/sec) than the second (605±5 mL/sec, p<0.001) and third (601±8 mL/sec, p<0.001). Similarly, in the 1200 mL/sec chamber, the fourth quarter (994±13 mL/sec) had a significantly higher flow rate than the second (917±8 mL/sec, p<0.001) and third (914±7 mL/sec, p<0.001). Closing the second and third air inlet holes while lifting the 600 mL/sec ball produced the lowest inspiratory flow rate (432±15 mL/sec) and pressure (-4.0±0.3 cm H₂O) among conditions. Conclusion: Feedback ball elevation influenced inspiratory flow and pressure in the 600 and 1200 mL/sec chambers, whereas no significant differences were observed in the 900 mL/sec chamber. Selective closure of air inlets, particularly closure of two inlets, markedly reduced inspiratory flow and pressure. Further in vivo studies in human subjects are warranted to validate these findings.