• 29
    Mar
  • Recovery of Gas Exchange Variables and Heart Rate: RESULTS

Spirometric and Vo,^ values were within normal limits in the control group (Table 1). In the patients with COPD, mean FEVi was 43 percent of predicted (SD, 15 percent), and Voa was significantly reduced at 15.9 ml/kg/min (SD, 3.25 ml/kg/min; p<0.001 vs controls).

Table 1—Demographic, Spirometric, and Maximal Exercise Data

Data

Control

COPD

Age, yr

62 ±6

69±5

Height, in

68±3

69±3

Wfeight, lb

169 ±25

162 ±14

FVC, percent of predicted

116±11

79 ±16

FEV,, percent of predicted

123 ±14

43± 15

FEFso*, L/mint

132 ±20

24± 13

Vow, ml/kg/min

27.4 ±6.3

15.9 ±3.3

FIGURE 1 . Percentage

FIGURE 1. Percentage of recovery of VE (± SD) in control subjects.

Percentage of recovery for ventilation and Vo2 are shown in Figures 1 and 2 for control subjects and Figures 3 and 4 for the patients with COPD; the pattern of return to baseline for all variables was biphasic, with a rapid initial recovery followed by a slower late decline. All gas exchange variables and HR recovered more slowly in the group with COPD (Table 2). For each variable the half-time of relative recovery was approximately twice as long in the patients with COPD as in the control subjects. Nevertheless, the extent of recovery was not significantly different between the groups for any of the gas exchange variables and HR (Table 3).
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FIGURE 2. Percentage

FIGURE 2. Percentage of recovery of VOJ/KG (±SD) in control subjects.

Table 2—Half-Times of Recovery of Gas Exchange Variables and HR

Half-Ише, min

Data

Control

COPD

p Value



Ve

2.0 ±0.5

3.3± 1.7

0.037

Vco2

1.6±0.3

3.1±1.6

0.012

VoAg .

1.3±0.2

2.3± 1.3

0.025

Excess Vco2

2.9±0.6

5.7±2.4

0.002

HR

2.3± 1.0

4.6±2.8

0.032

FIGURE 3. Percentage

FIGURE 3. Percentage of recovery of VE (± SD) in patients with COPD.

In the patients with COPD, correlation of the half- times of recovery with the FEVj showed that all gas exchange variables were slowed in proportion to the severity of the airway disease (Table 4); the highest correlation was with excess Vco2. The recovery rate of the HR did not correlate with FEV,. Correlation with FVC was not significant (data not shown). Al­though the extent of recovery was similar in the two groups, the time required for 90 percent recovery of excess Vco2 was greater than ten minutes in ten of 12 patients with severe COPD (FEV,, 0.8 to 1.4 Us) and in two of four patients with mild disease (FEVb 1.9 to 2.1 L/s), whereas only one of ten control subjects had 90 percent recovery time for excess Vco2 which exceeded ten minutes. canada pharmacy mall

FIGURE 4. Percentage ofrecovery

FIGURE 4. Percentage of recovery of VoAg (± SD) in patients with COPD.

Table 3—Extent of Recovery for Gas Exchange Variables and HR

Data

Control

COPD

p Value

Ve,
percentf

133 ±27

121 ±18

NS

Vco2, percentf

116± 23

115± 17

NS

VOa/kg,
percent

111±16

109 ±12

NS

Excess Vco2, ml/kg/minf

0.66 ±0.28

0.89 ±0.84

NS

HR, percentf

114 ±8

116 ±7

NS

In the control group, the respiratory rate was 15.5/ min during warm-up and 19.5/min during eight to ten minutes of recovery, compared with values of 23.4/ min and 25.7/min, respectively, in the group with COPD. The differences between groups are signifi­cant at both intervals (p<0.01), but the changes within each group after exercise are not significant.

Table 4—Correlation Coefficients for FEVX Half-Times of Recovery in Patients with COPD

Data


r

p
Value



Ve

-0.65

0.009

Vco2

-0.64

0.010

voAg

-0.61

0.017

Excess Vco2

-0.77

0.001

HR

-0.29

0.295

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