Relationships between forced vital capacity and subjective responses to added resistive load to inspiration

1. 1. This study was conducted to investigate the effects of forced vital capacity on breathing pattern and subjective responses to inspiratory resistance. 2. 2. The subjects were divided into two groups according to their %FVC [large (L) and small (S) group; five subjects in each]. 3. 3. Added inspiratory resistances were 0.6 (control), 1.5 (R1), 2.5 (R2), 3.1 (R3) cmH₂O · 1^-1 · s. 4. 4. Breathing pattern was analyzed by personal computer during rest and exercise with bicycle ergometer. 5. 5. The degree of sensation of breathing difficulty was expressed in SNS reported in our previous study. 6. 6. SNS in S group increased with resistance while no tendency was observed in L group. SNS in S group was significantly greater than that in L group at R3 condition. 7. 7. The breathing pattern of S group was characterized in smaller tidal volume and faster respiratory frequency compared to those of L group with no resistive load. 8. 8. However, outstanding changes in breathing pattern were observed in S group with longer inspiratory time and lower mean inspiratory flow rate when resistive loads were added, which led to increased tidal volume and decreased respiratory frequency.