Detection of Airway Obstruction in Exercise-Induced Asthma Outcomes

Heart Rate Response

All patients increased their heart rates to 40-55 percent of predicted maximum heart rate during Wl and to 60-75 percent of predicted maximum heart rate during W2. In nearly all patients heart rates reached the steady state levels within three minutes; but in a few cases continuous increase in heart rates was observed, and by the end of the exercise, reached nearly 200 beats per minute. No extrasystoles or other arrhythmias were observed during the entire study. In nearly all patients the return of heart rates to preexercise values was observed within one to three minutes after exercise.

Clinical Scores

Results of the clinical scores are summarized in Figure 2. The numbers inside the circles represent the number of patients whose physical findings produced certain clinical scores at the appropriate time as described in Table 2. Points without circles mean that only one patient gave such a clinical change. It is evident after W1 that approximately half of the tested patients had no wheezing and no detectable respiratory difficulties. Similar results were observed after W2.

Peak Expiratory Flow Rate

Peak Expiratory Flow Rate

All patients were familiar with PEFR measurements due to the established practice of measuring PEFR several times daily on the wards. As seen in Figure 3, at baseline in both workloads nearly all the patients had PEFR values that were equal to or greater than their predicted values. Visually, there is a trend towards a decrease at 7 minutes and a return towards the baseline at 30 minutes. It can also be observed that on a number of occasions there is an increase in PEFR. PEFR (liters/minute ± SE) at baseline in W1 was 221.1 ± 15.9. At seven minutes after exercise a statistically insignificant deorease (186.2 ± 16.4) was seen, which had already improved at 30 minutes after exercise (217.5 ± 15.8). In W2 baseline value was 275.0 ± 16.4, and at seven minutes after exercise an insignificant decrease (223.2 ± 19.7) was also seen. Again, at 30 minutes the PEFR improved slightly (264.1 ± 15.9).

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In order to rule out the possibility that any change in PEFR occurred at times other than our established measurement periods (7 and 30 minutes after exercise), the PEFR was also tested at 5, 7, 15, and 30 minutes after exercise. No significant decreases in PEFR were found at any of these periods.

Spirometry

A. FVC and FEVi

Figure 4 demonstrates the results of spirometry. It is apparent that at baseline most patients were either equal to or above their predicted values in both workloads. After exercise the same patients showed decreases in both their FVC results (moving from right to left) and FEVi results (moving from top to bottom). It is obvious that the decreases seen in these two parameters are not proportional; if they were, the shift would be along the line of identity. There is obviously a greater decrease in FEVi than in FVC, since the major portion of values seven minutes after exercise shifts below the line of identity and parallel with the FEVi axis. In W2 there was an even greater effect on both of these flow-dependent parameters, for nearly all of the data shifted below the line of identity after exericse. Again, there was a greater decrease in FEV1 and in FVC.

B. MMEF

Results of MMEF (liters/second ± SE) are shown in Figure 5. The predicted value for both workloads was 2.66 ± 0.12. The baseline value in W1 (1.41 ± 0.09) and the baseline value in W2 (1.85 ± 0.18) were both statistically decreased from predicted values (p<0.01). At 7 minutes after exercise in Wl, a significant decrease to 1.03 ± 0.11 (p<0.02) was seen, whereas at 30 minutes after exercise, the MMEF had already slightly increased (1.17 ± 0.11). Similarly, in W2 a significant decrease was seen 7 minutes after exercise to 1.26 ± 0.13 (p<0.02), and again the MMEF increased slightly at 30 minutes (1.50 ± 0.12).

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spirometry

Body Box

A.Raw

The predicted value for Raw (cm Н2O/liters/second ± SE) for both groups was 4.97 ± 0.16. Raw at baseline in W1 was 3.07 ± 0.30 and at baseline in W2 was 2.70 ± 0.28; both of these values are significantly below predicted (p<0.01). In W1 the Raw increased significantly 7 minutes after exercise to 4.50 ± 0.44 (p<0.02), but at 30 minutes a slight but insignificant decrease from the 7 minute value was seen (3.90 ± 0.32). In W2 the Raw increased at seven minutes after exercise to 4.36 ± 0.79, but the increase was not significant (0.100.05). At 30 minutes after exercise the Raw slightly decreased from the 7-minute value to 3.36 ± 0.34 (p<0.10).

B.Vt

The predicted value for Vtg (liter ± SE) for both groups was 1.44 ± 0.06. Vtg at baseline in W1 was 2.54 ± 0.13 and at baseline in W2 was 2.52 ± 0.13; both of these values are significantly above the predicted (p<0.01). In W1 the Vtg did not significantly change at either 7 minutes (2.59 ± 0.15) or 30 minutes (2.47 ± 0.13) after exercise. In W2 a slight but insignificant increase in Vtg at seven minutes after exercise was observed (2.76 ± 0.14). At 30 minutes after exercise the Vtg had already decreased (2.50 ±0.26).

C. SGaK

Since Vtg has a significant effect on Raw, the results of the body box must also be reported as SGaw (Fig6).

In W1 the SGaw =((1/cm H2Osec) ± SE) at baseline was 0.15 ± 0.01 and decreased insignificantly at 7 minutes after exercise (0.11 ± 0.01) with a slight return toward baseline values at 30 minutes after exercise (0.12 ± 0.01). In W2 the SGaw (± SE) at baseline was 0.16 ± 0.01, and observed at seven minutes after exercise a statistical decrease to 0.11 ± 0.13 (p 0.05) was observed. At 30 minutes after exercise only a minimal increase from the 7-minute value was seen (0.13±0.01).

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Closing Volume

An attempt was made to measure CV in all of our patients at baseline and at 7 and 30 minutes after exercise. In both workloads CV was adequately and completely determined in only five patients (Fig 7). The baseline values for CV were somewhat higher than predicted values. In both workloads CV in all patients markedly increased 7 minutes after exercise; however, in three cases in W1 and in two cases in W2, rather than a return toward baseline, a further increase of CV was observed 30 minutes after exercise. In one case in W1 and also one in W2, an increase in CV was not apparent at the 7-minute post-exercise measurement but was seen 30 minutes after exercise (learn more).

Clinical asthma scoresFigure 2. Clinical asthma scores (see Table 2) as related to exercise. (For explanation, see text).
Fig3
Figure 3. Changes in peak flow (PEFR) liters/min.
Relationships of FVC
Figure 4. Relationships of FVC to FEVi as a percentage of predicted.
values in MMEF
Figure 5. Absolute values in MMEF ± SE (liters/sec) as determined before and after exercise in both workloads.
values in SG
Figure 6. Absolute values in SG.
Changes in CV
Figure 7. Changes in CV (expressed as percent VC) as measured before and after exercise in both workloads.