Results of Conscious Perception of Bronchospasm as a Protective Phenomenon in Asthma

Table 1 represents comparisons for the following indices of pulmonary function: total lung capacity (TLC), FRC, RV, FEVi, Raw, Vmax50 (uncorrected for lung volume), and V/V25-75. Comparisons were made in the following fashion. Consider the values of Raw for subject 1. On the first occasion listed, subject 1 was asymptomatic, the Raw being 76 percent of predicted. A change of 127 percent from that baseline level was seen when symptoms first became apparent.

On the second occasion listed, subject 1 again initially was asymptomatic, but her baseline value of Raw was somewhat impaired (166 percent of predicted). On this occasion, only a 93 percent increase from this baseline level was required for her to reach a threshold point. Subject 1 was thus considered to be relatively more sensitive to acute fluctuation on the occasion when she commenced with already impaired pulmonary function. Such a comparison was not possible in every subject, since baseline indices did not necessarily differ by 25 percent or more. Thus, only those tests when baseline fluctuation allowed such comparisons are tabulated.

Pulmonary Function

Seven of the ten subjects demonstrated sufficient fluctuation in baseline values for static lung volumes (TLC, FRC, or RV) to allow comparisons. In each case, as the baseline value for static lung volume increased, the relative change (ie, further increase) needed to attain a threshold point became less.

A 25 percent fluctuation in baseline FEV1 was not seen in any subject. When Raw was considered, comparisons of sensitivity to internal loading were possible in six subjects. In four of these six subjects, as baseline Raw became impaired, the subject appeared relatively more sensitive to further acute deterioration. Similar trends were seen in four of the seven subjects in whom comparisons of Vmax50 were possible and in six of the seven subjects in whom comparisons of V/V25-75 were made. Thus, only a minority of subjects had a relative blunting in their perception of acute “bronchospasm” as their baseline pulmonary function deteriorated.

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Table 1—Comparison of Baseline indices of Pulmonary Function and Change Required to Produce Threshold Symptoms

Subject and Measurement TLC FRC RV FEVi Raw Vmax50 V/V25-75**
Subject 1 (F, 21 yr) Determination 1 Initial value, percent of predicted 66 99 76 121 3.4
Percent change to threshold 13 84 127 40 15
Determination 2 Initial value, percent of predicted 114f 173t 166t 71 1.9t
Percent change to threshold 8t 4t 93t 43 8t
Subject 2 (M, 23 yr) Determination 1 Initial value, percent of predicted 82 2.9
Percent change to threshold 31 28
Determination 2 Initial value, percent of predicted 63 2.01
Percent change to threshold 53 13t
Subject 3 (F, 22 yr) Determination 1 Initial value, percent of predicted 71< 65
Percent change to threshold 56 158
Determination 2 Initial value, percent of predicted 1211 152t
Percent change to threshold 30f 511
Subject 4 (M, 24 yr) Determination 1 Initial value, percent of predicted 93 46 4.1
Percent change to threshold 79 43 37
Determination 2 Initial value, percent of predicted 143t 32t 2.8t
Percent change to threshold 72t 35t Ht
Subject 5 (M, 22 yr) Determination 1 Initial value, percent of predicted 76 83 101 46 1.8
Percent change to threshold 53 151 79 43 38
Determination 2 Initial value, percent of predicted lilt 1811 2631 32t 1.4t
Percent change to threshold 18t 59t 72t 35t 27t
Subject 6 (F, 25 yr) Determination 1 Initial value, percent of predicted 87 121 81
Percent change to threshold 20 21 21
Determination 2 Initial value, percent of predicted 1231 179t 39
Percent change to threshold iot 2t 37
Subject 7 (M, 23 yr) Determination 1 Initial value, percent of predicted 87 116 2.4
Percent change to threshold 63 49 28
Determination 2 Initial value, percent of predicted 155t 68t 1.4t
Percent change to threshold 19t 24t 12t
Subject 8 (F, 31 yr) Determination 1 Initial value, percent of predicted 130 74 2.5
Percent change to threshold 141 194 25
Determination 2 Initial value, percent of predicted 172t 286 1.7
Percent change to threshold 116t 334 50
Subject 9 (M, 23 yr) Determination 1 Initial value, percent of predicted 85 60 86 68 2.2
Percent change to threshold 27 152 49 2 27
Determination 2 Initial value, percent of predicted 114f 172t 156t 441 1 6t
Percent change to threshold 5t 17t 341 ot 6t
Subject 10 (M, 22 yr) Determination 1 Initial value, percent of predicted 139
Percent change to threshold 151
Determination 2 Initial value, percent of predicted 238
Percent change to threshold 426
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