Constrictive Bronchiolitis Obliterans: The Fibrotic Airway Disorder

Gary R. Epler

Expert Rev Resp Med. 2007;1(1):139-147.

Pulmonary Function Testing

Pulmonary function tests traditionally show major airway irreversible obstruction with decreased FEV₁ and FEV₁:FVC ratio with no response to bronchodilator inhalation. However, as the large airways are not involved, a restrictive pattern may occur with decreased vital capacity and corresponding FEV₁, resulting in no decrease in the FEV₁:FVC ratio. In this setting, the small airways are often completely obliterated on a focal basis, resulting in a normal diffusing capacity because remaining lung is normally ventilated and perfused. Markopoulou and others found that among 19 patients with bronchiolar obliteration from both fibrotic and inflammatory lesions, 11 had airflow obstruction, one had restrictive pattern, one had mixed obstructive and restriction, two had air trapping, and four had normal spirometric values.^[61]

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Abstract and Introduction
Pathological Description
Cause & Clinical Settings
Lung-transplant Bronchiolitis Obliterans
Radiologic Features
Pulmonary Function Testing
Clinical Course
Management & Treatment
Summary & Conclusions
Expert Commentary
Five-year View
Sidebar: Key Issues

Causes and Clinical Associations of Constrictive Bronchiolits
Idiopathic Fume or oral toxin exposure Toxic fumes: sulfur dioxide, ammonia, methylisocyanate (industrial accident, Bhopal, India) or fire smoke Mustard gas from chemical warfare Diacetyl exposure from butter flavoring Ingested liquid mixture of Sauropus androgynus Bone marrow transplantation Stem cell transplantation Lung transplantation Post infection Mycoplasma pneumoniae Adenovirus Influenza virus Drug reaction Gold therapy Penicillamine Connective tissue disorders Rheumatoid arthritis Scleroderma Miscellaneous disorders Ulcerative colitis Stevens-Johnson syndrome Neuroendocrine cell hyperplasia Neuroendocrine cell hyperplasia with carcinoid tumorlets Aspiration of foreign bodies or esophageal gastric contents

Classification of Bronchiolitis Obliterans Syndrome
Stage	Classification details
BOS 0	¹ > 90% of baseline and FEF²⁵ ⁷⁵ > 75% baseline
BOS 0-p*	FEV₁ 81-90% of baseline and/or FEF²⁵≤ 75% baseline
BOS 1	FEV₁ 66-80% of baseline
BOS 2	FEV₁ 51-65% of baseline
BOS 3	FEV₁ 50% or less of baseline

*This category has been created because studies suggest that FEF²⁵ ⁷⁵deteriorates before FEV₁ in most recipientsp.^[31,38]
BOS: Bronchiolitis obliterans syndrome; BOS 0-p: Potential BOS stage ;0; FEF²⁵75:Forced mid-expiratory flow; FEV₁: Forced expiratory volume in 1 s.

Classification of Primary Graft Dysfunction
Grade	Classification details
0	PaO₂:FiO₂ ratio >300 mmHg; normal x-ray
1	PaO₂:FiO₂ ratio >300 mmHg; pulmonary edema x-ray
2	PaO₂:FiO₂ ratio 200-300 mmHg; pulmonary edema x-ray
3	PaO₂:FiO₂ ratio <200 mmHg; pulmonary edema x-ray

PaO²:FiO²: Ratio of artial pressure of arterial oxygen to the fraction of inspired oxygen.

Data from ^[46].

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