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Biomedical subjects

M Tahan

Publications and source records attributed to M Tahan.

5 recordsLinked to original sources
PubMed1996

Comparative influence of a single allergen exposure on the different components of airway response to methacholine.

We compared the effects of an allergen challenge on airway responsiveness to methacholine, the slope of the dose-response curve (DRC) and post-methacholine fall in forced vital capacity (FVC) or forced expiratory volume in 1 s (FEV1)/FVC, and determined whether any changes in these parameters were related to the presence and magnitude of the late asthmatic response (LAR) in mild stable asthma. Twenty-three allergic asthmatic subjects had an allergen challenge, preceded and followed 24 (n = 12) and/or 48 (n = 22) h later by a methacholine challenge. Sixteen subjects had a dual asthmatic response to the allergen. On the post-allergen methacholine challenge, as compared with the pre-allergen test, differences in mean fall in FVC or FEV1/FVC at 20% fall in FEV1 and the slope of the DRC did not achieve statistical significance, even in the group with LAR, which showed a significant increase in airway responsiveness at 24 h. There was, however, a correlation between allergen-induced changes in PC20 and (1) the change in post-methacholine FVC fall in the LAR group at 48 h, and (2) the change in the slope of the DRC in the early-asthmatic-response group at 24 h. In conclusion, allergen-challenge-induced changes in airway response to methacholine are heterogeneous among asthmatic subjects and although it may increase airway responsiveness (PC20), particularly in late responders, it minimally affects the other aspects of airway response to methacholine, suggesting that a more powerful or sustained allergic stimulus is required to modify the latter.

Administration, Inhalation↗
PubMed1994

Effects of acute allergen exposure on posture-induced changes in airway responsiveness to methacholine in asthma.

BACKGROUND: The influence of an allergen challenge on recumbency induced changes in airway responsiveness to methacholine was documented in seven nonsmoking subjects with stable mild asthma (3M, 4F). METHODS: All subjects spent four hours (8 to 12 AM) in the supine position before and 24 hours after an allergen challenge that induced a dual asthmatic response. FEV1 was measured hourly in the supine position and a methacholine challenge was done in the sitting position before and after each 4-hour period. None used bronchial antiinflammatory drugs before or during the study. RESULTS: The mean maximal fall in FEV1 (+/- SEM) was 31.0 +/- 1.1% within one hour of the last allergen inhalation and 27.5 +/- 4.9% between two and eight hours later. Presupine/postsupine session FEV1 (%pred +/- SEM) was unchanged either at baseline or postallergen challenge sessions, with values of 89.3 +/- 2.7/88.3 +/- 5.1 and 86.6 +/- 4.2/87.4 +/- 5.7. Presupine/postsupine PC20 methacholine was slightly reduced but this did not reach statistical significance (P > .05), with a mean PC20 (mg/mL) of 0.83 +/- 1.44/0.52 +/- 1.46 (preallergen session); 0.55 +/- 1.44/0.39 +/- 1.37 (postallergen challenge session). This delta PC20 (baseline/post-session) did not differ between the two sessions (P > .05). The delta PC20 was not correlated with the magnitude of the late asthmatic response to allergen nor the postallergen increase in airway responsiveness. CONCLUSIONS: We conclude that an acute allergen challenge does not significantly increase recumbency-induced changes in airway response to methacholine in patients with mild asthma. The possibility of a significant influence of pro-inflammatory stimuli on recumbency-induced changes in bronchomotor tone in more severe patients or if the stimulus is repeated should be further assessed.

Adult↗
PubMed1993

Perception of acute or progressive resistive loads in normal and asthmatic subjects.

To determine if the rapidity of increase in airway resistance influences its perception, we looked at the perception of acute and progressive expiratory resistive loads in 9 controls (CN) and 9 asthmatics (AS). Each had 4 single-blind tests in a randomized order, during which resistances were increased from 0 to 24 cm H2O/l/s in 1, 3 or 6 steps or decreased in 6 steps. Dyspnea scores were recorded on a modified Borg scale (0-10). FEV1 and lung volumes were measured in all subjects initially and after the last resistance applied during tests C and D. Tidal volume, respiratory rate, the ratio of inspiratory time over total breathing time (Ti/Ttot) and minute ventilation were measured throughout each test. Borg scores were not significantly different from one test to the other. Overall, AS tended to have a higher perception of resistive loads than CN, although it did not reach statistical significance. FEV1 did not change significantly in both groups between the tests and before and after application of resistances. Functional residual capacity was not significantly different between AS and CN or before and after the tests. Residual volume was higher in AS (mean of the 4 tests: 1.6 +/- 0.05 l) compared to CN (1.1 +/- 0.14 l) (p = 0.003) but was unchanged after the applied resistances. Ti/Ttot ratio was similar for AS and CN and decreased significantly from 0 to 24 cm H2O/l/s in both groups (all tests, p < 0.01). Respiratory rate was higher in CN than in AS at all resistances (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Influence of posture on expiratory flows and airway responsiveness to methacholine in asthma.

This study looked at the effects of posture on the morning/evening expiratory flows and airway responsiveness to methacholine. Fourteen nonsmoking subjects with stable asthma (eight men, six women) were included in the study. Subjects were randomly allocated to spend 4 h in the supine or seated position on separate days, in the morning from 8 to 12 AM and in the evening from 8 to 12 PM. The FEV1 was measured hourly in the assigned position. Before and after each 4-h period, a methacholine inhalation test was done in the sitting position. In the morning study, baseline FEV1 measurements on the supine and seated days were not different. There was no significant difference between the baseline and postsession FEV1 on both days (baseline and postsession FEV1 percent predicted +/- SEM; seated: 83.6 +/- 2.9, 83.8 +/- 3.3; supine: 85.8 +/- 2.8, 85.4 +/- 3.7; n = 13). delta FEV1 (baseline/postsession) was not different between the two sessions. In the evening study, baseline FEV1 measurements on the supine and seated days were similar. FEV1 decreased after both sessions, although this difference reached statistical significance only in the supine position (baseline and postsession FEV1 percent predicted +/- SEM; seated: 90.0 +/- 4.1, 84.9 +/- 4.1, p = 0.08; supine: 90.7 +/- 3.1, 82.9 +/- 4.5, p = 0.02; n = 8). delta FEV1 (baseline/postsession) was not different between the two evening sessions. In the morning, after the seated position, PC20 methacholine was unchanged (mean PC20 [mg/ml]: beginning = 1.00, end = 1.02) while after the supine position it was slightly reduced from a mean of 0.97 to 0.73 mg/ml. This last reduction was mainly observed in the most hyperresponsive subjects and its magnitude was significantly correlated with baseline PC20 (r = 0.637, p = 0.024). The increase in methacholine response (delta PC20) after the supine session was significantly higher than after the seated session. In the evening study, there was a slight reduction in PC20 after both sessions, but this was only significant after the supine position (mean PC20 baseline and postsession [mg/ml]: seated: 0.63, 0.47, p = 0.08; supine: 0.62, 0.44, p = 0.04). No difference was found between delta PC20 of the two sessions. We conclude that the supine position does not have persistent effects on FEV1, but it may increase airway responsiveness in the most hyperreactive subjects.

Adolescent↗