We used P=0.31 m to estimate pressure and found it to be 99.3 ± 5.7 percent of measured Pm determined by planimetry. The SIP before training was significantly correlated with MIP-FRC (r = .667, p<.05) and with MIP-RV (Fig 4, r = .89, p<.01). more
Over the course of six weeks, IMT produced significant increases in inspiratory training pressure (Pm), external work/minute and pressure-time integral (Table 4). The SIP after training was measured in five patients and found to be higher (49.1 ± 14.0 cm H20) than both pretraining SIP (25.4 ± 17.2, p<0.005) and final training pressure (41.4 ± 17.4, p<0.025).
Breathing Pattern The effects of IMT on breathing pattern are illus trated in Figure 5. Duty cycle during threshold breathing was initially quite long (0.54 ±0.10) but shortened after six weeks of training (0.42 ±0.11, p<0.005). Mean inspiratory flow (VT/Ti) during threshold pressure breathing increased from 0.40±0.15 Us before training to 0.53 ±0.21 Us after training (p<0.05). Resting Ti/Ttot was shorter after training (0.36±0.06) than before (0.44 ±0.06, p<0.005) but resting VT/Ti was not significantly altered. None of these breathing pattern indices measured during incremental cycle exercise was significantly different after six weeks IMT than before it.
Static Inspiratory Pressure
The IMT produced substantial increases in MIP-FRC (p<0.005) and MIP-RV (p<0.025). In the control group, no significant change in MIP was observed over six weeks (Table 2). Patients who underwent IMT had significantly higher MIP-FRC and MIP-RV after training than those who did not (p<0.05).
The FRC, TLC and RV were measured in four of the eight patients, and no significant change after training was detected. In two patients, all three lung volumes were higher after training, while in one, all three volumes were lower.
Table 4—Breathing Pattern During IMT
|Wfeek I||Week 6|
|Pm, cm H,0||23 ±14||37 ± 15t|
|/Pm.dt, cm HtO,s/min||544 ±296||627 ± 293*|
|f, breaths/min||18±7||19 ±6|
Figure 4. Relationship of sustained inspiratory pressure to maximal inspiratory pressure at RV prior to training.
Figure 5. Left column: average respiratory cycle with Vt/Ti represented by the slope of the ascending limb of the schematic spirogram and end-expiratory lung volume taken as zero. Continuous lines; before training; dashed lines; after training; Bars, one SD from the mean. Right column: Ti/Ttot before (open circles) and after (closed circles) six weeks IMT. Top row, during threshold breathing; middle row, at rest; Bottom row, during maximal cycle exercise. Bars indicate one SD either side of the mean.
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