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Safety and tolerability of three consecutive bronchoscopies after allergen challenge in volunteers with mild asthma
  1. H H Kariyawasam1,
  2. M Aizen1,
  3. A Barry Kay2,
  4. D S Robinson3
  1. 1Department of Allergy and Clinical Immunology, Leukocyte Biology Section, MRC and Asthma UK Centre in Allergic Mechanisms of Asthma, Faculty of Medicine, National Heart and Lung Institute, Imperial College London, London, UK
  2. 2Leukocyte Biology Section, MRC and Asthma UK Centre in Allergic Mechanisms of Asthma, Faculty of Medicine, National Heart and Lung Institute, Imperial College London, London, UK
  3. 3Department of Allergy and Clinical Immunology, Leukocyte Biology Section, MRC and Asthma UK Centre in Allergic Mechanisms of Asthma, Faculty of Medicine, National Heart and Lung Institute, Imperial College London, London, UK
  1. Correspondence to:
    Professor A Barry Kay
    Sir Alexander Fleming Building, Leukocyte Biology Section, Imperial College London, South Kensington Campus, London SW7 2AZ, UK; a.b.kay{at}imperial.ac.uk

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Ethical and safety considerations limit the design of studies with more than two consecutive fibreoptic bronchoscopies (FOBs) in patients with asthma. We present data on the safety and tolerability of three consecutive bronchoscopies at baseline, and 24 h and 7 days after allergen provocation. The study included 15 volunteers with mild asthma (9 men and 6 women); median age 25 (range 19–46) years; percentage predicted forced expiratory volume in 1 s (FEV1) 97% (range 75.4–125.7%); and a mean provocative concentration of methacholine causing a 20% fall in FEV1 (PC20) of 2.1 (95% confidence interval (CI) 1.2 to 3.6) mg/ml at baseline FOB, 0.93 (95% CI 0.38 to 2.2) mg/ml at 24 h (p = 0.08) and 0.90 (95% CI 0.45 to 1.8) mg/ml at 7 days (p = 0.03) after the allergen challenge.

FOB was not associated with a significant fall in FEV1 at baseline (median FEV1 93.9% predicted (range 80–120.1%) before FOB and 92.8% predicted (73.6–119.0%) at discharge). However, there was a significant reduction in median (range) percentage predicted FEV1 after FOB performed both 24 h and 7 days after the inhaled allergen challenge: 94.9% (75.1–111.1%) before FOB and 85.5% (62.4–119%) at discharge, p = 0.04, 24 h post challenge; and 100.1% (70.56–119%) before FOB, falling to 90.2% (66.2–119%) 7 days later, p = 0.009. We found a correlation between the percentage of instilled bronchoalveolar lavage volume recovered and change in FEV1 at discharge (r = 0.31, p = 0.04) when comparing combined data for all three bronchoscopies.

The median (range) pre-FOB oxygen saturation on room air was 99% (95–100%), with no significant change at discharge (97% (96–100%), p = 0.25). During FOB, the median (range) maximum oxygen saturation recorded was 99% (98–100%), whereas the minimum was 96% (92–100%). End procedure median (range) saturation was 98% (91–100%) on 2–4 l supplemental oxygen. Oxygen saturation on room air 10 min post procedure was maintained at a median (range) of 98% (95–99%).

The median (range) oxygen saturation pre-FOB on room air was 99% (96–100%) at 24 h after the allergen challenge and 97% (94–100%) at discharge (p = 0.02). The peak median (range) oxygen saturation recorded was 99% (98–100%) and the lowest level recorded was 96% (94–100%). The end median (range) saturation was 97% (93–100%) on 2–4 l of entrained oxygen, whereas the saturation on room air 10 min post procedure was 98% (94–100%).

The median (range) pre-FOB oxygen saturation was 98.5% (96–100%) at 7 days and 97.5% (96–100%) at discharge (p = 0.05). The highest recorded median (range) oxygen saturation was 99.5% (98.5–100%) and the lowest was 96% (92–98%). No clinical consequence as a result of desaturation was seen during the course of bronchoscopy.

We found no significant correlation between the change in oxygen saturation and the percentage volume of bronchoalveolar lavage recovered.

Table 1 summarises the effects of FOB on asthma control the day after bronchoscopy. FOB was associated with increased symptoms on all occasions. A significant fall in FEV1 was seen only after FOB that was preceded by the allergen challenge (p = 0.002) and was associated with the most significant increases in symptoms (p = 0.001) and corresponding drug usage (p = 0.004). None of these changes required treatment other than inhaled short-acting β2-agonists and all had resolved by the second day after FOB. Of the 15 volunteers, 12 returned for follow-up 2–6 weeks after the end of the study. The median (range) percentage predicted FEV1 was 99.88% (79–109%) at follow-up compared with 95.18% (75.41–114.8%) measured at the study entry screening visit. All 12 of these volunteers were still maintained on short-acting β2-agonists only and none reported clinical deterioration of asthma control in the weeks after the study.

Table 1

 Summary of the effect of bronchoscopy on asthma control in terms of percentage predicted forced expiratory volume in 1 s, symptom scores and frequency of reliever drugs recorded the day before and the day after fibreoptic bronchoscopy

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Footnotes

  • Funding: This study was sponsored by the Imperial College Trust Fund.

  • Competing interests: None declared.

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