Canadian Neighbor Pharmacy: Results of Imposed Pursed-Lips Breathing on Respiratory Mechanics and Dyspnea at Rest and During Exercise in COPD

Whereas none of our subjects claimed to have dyspnea at rest, during control exercise at 60% of WLmax, dyspnea scores ranged between 3.5 and 9. With PLB, breathlessness increased in four of the eight patients, was relatively unaltered in two patients, and decreased in two patients (Fig 1).

Effect of PLB on Breathing Pattern

Individual and average values for breathing pattern variables at rest and during exercise are shown in Tables 2 and 3, respectively. PLB prolonged total breath duration, slowed breathing frequency (fB), and increased Vt both at rest and during exercise.

Effect on End-Expiratory and End-Inspiratory Lung Volumes

Whereas EELV increased on average by approximately 350 mL with exercise alone, it was variably altered by PLB at rest and during exercise across patients (Tables 2 and 3). On average, the increased Vt and unaltered EELV caused the end-inspiratory lung volume (EILV), which was 81% of TLC at rest without PLB, to increase to 86% of TLC with PLB (p < 0.05). Furthermore, due to a combined dynamic hyperinflation and increased Vt values, EILV during exercise increased to 91% of TLC without PLB and was 92% of TLC with PLB. Changes in the dyspnea scores promoted by PLB were significantly correlated with changes in EELV (as a percentage of TLC; r2 = 0. 82; p = 0.002).

Effect of PLB on Respiratory Mechanics

As shown in Table 4 and also illustrated by the respective horizontally lined and hatched areas of the average plots of Vt vs Ppl shown for two representative subjects in Figure 2 (panel A in upper and lower panels) because PLB promoted larger Vt values, Wires and WEres were significantly increased with PLB at rest and during exercise However, the total resistive work of breathing [W(l + E)res] per minute was not significantly altered by using PLB during exercise.

As evidenced by the higher expiratory Pga values observed in the average VT-Pga loops presented in Figure 2 (panel B in upper and lower panels), PLB performed at rest promoted an increased abdominal expiratory muscle recruitment compared to control breathing This was a consistent finding in all subjects As presented also in Figure 2 (panel B in upper and lower panels), exercise without PLB promoted greater clockwise looping in all patients compared to control breathing at rest, indicating the presence of more expiratory abdominal muscle activity However, PLB during exercise further increased abdominal muscle recruitment in only three of the patients.

In general, neither mean Pdi nor TTdi were altered by PLB at rest or during exercise (Table 4) However, as shown in the individual exercise VT-Pdi loops of Figure 2 (panel C in upper and lower panels), end-expiratory Pdi was increased as a result of Pdi increasing prior to the onset of inspiratory flow, which was a consistent finding in all COPD patients breathing with and without PLB during exercise, and was observed in four of the eight patients during control breathing at rest The mean end-expiratory Pdi, which was 2. 5 ± 1. 6 cm H2O during control breathing at rest and increased to 8 0 ± 3 6 cm H2O with exercise, was not significantly altered by PLB under either condition

Effect of PLB on Inspiratory Muscle Capacity

The mean PcapI at FRC was —67. 5 ± 18. 4 cm H2O, where the mean FRC for the group was 69. 1 ± 8. 2% of TLC, while at TLC the mean PcapI was —24. 2 ± 9. 5 cm H2O. Individual and average group values of the mean inspiratory ratio of Ppl/ PcapI (in percent) are presented in Table 4. The ratio was increased significantly with PLB at rest but was inconsistently altered by PLB during exercise Changes occurring in the Ppl/Pcapl ratio with PLB during exercise were significantly correlated with changes in EELV (as a percentage of TLC; r2 = 0.65, p = 0.016) and EILV (as a percentage of TLC; r2 = 0.60; p = 0.024).

Figure 3 illustrates the relationship between the concurrent changes occurring in the dyspnea scores and the ratio of mean inspiratory Ppl to Pcapl with PLB during exercise. Subjects who experienced less breathlessness when using PLB exhibited decreases in the mean inspiratory ratio of Ppl to Pcapl (r2 = 0.84; p = 0.001).

Figure 1. Average breathlessness scores (VAS) from the last 4 min of constant-work-rate exercise in each of the eight COPD patients during control breathing (O) and PLB (•). Lines of asterisks represent the average dyspnea scores for the group.

Figure 2. Average loops of Ppl (A panels), Pga (B panels), and Pdi (C panels) plotted against Vt and obtained with breath-by-breath analysis during the last 4 min of resting breathing (upper panels) and exercise (lower panels) for two representative COPD patients. Dashed lines = control breathing; solid lines = PLB; О = points of end-expiration; • = points of end-inspiration. The loops in the A panels move in the clockwise direction, the direction of the loops in the B panels are indicated by the arrows, and the loops in the C panels move in the counterclockwise direction Error bars represent the SD for Vt and the respective pressures. Horizontally lined and hatched areas in the A panels represent the increased Wires and WEres values that occurred in the two subjects with PLB.

Figure 3. Relationship between changes in dyspnea and the concurrent changes in the ratio of mean inspiratory Ppl to Pcapl (as a percentage) occurring with PLB during steady-state exercise. The points represent the values for each individual patient with corresponding patient number.

Table 2—Ventilatory Parameters in Eight Patients With COPD During Resting Breathing

Table 3—Ventilatory Parameters in Eight Patients With COPD During Exercise

Table 4—Respiratory Mechanics in Eight Patients With COPD During Exercise