Bronchiolitis Obliterans Syndrome

Incidence in USA: 1:40,000

Racial predilection: None

Occurs primarily after lung and hematopoietic stem cell transplantation

Industrial workers exposed to inhalants who have presented with BOS: nylon-flock, battery workers, manufacturer of flavorings (diacetyl butter-like flavoring), and textile workers

Hypoxemia and severe periop airway obstruction.

Pulm infection, sepsis, and pulm edema post transplant.

Injury to tracheal anastomosis due to ETT placement.

Prolonged intubation (increased sensitivity to medications including muscle relaxants, pulm functions, renal impairment, and pulm edema).

Complications of immunosuppression (infection, hemorrhage, and renal impairment).

Preop focus must differentiate between active invasive pulm infection and ongoing chronic rejection with colonization, as well as maximizing medical condition and stratifying risk.

Pulm functions

Differentiating BOS from untreated invasive pulm infection and other disorders

Side effects of immunosuppression including infection with invasive techniques, hemorrhage, and renal failure with cyclosporine

Airway and vascular allograft denervation (physiologic and pharmacologic side effects)

Other effects of etiologic agents

Delayed-onset allograft dysfunction and continual decline in FEV ₁ not due to other etiologies of transplant dysfunction; it frequently occurs with signs of airflow obstruction.

Because BO is difficult to confirm histologically (transbronchial biopsy of larger airways with sporadic involvement often provides insufficient samples and has a high false-negative diagnostic rate), the International Society for Heart and Lung Transplantation proposed a staged clinical definition of BO termed BOS (stages 0 to 3 defined by changes in pulm functions, and based on spirometry, rather than histology).

BOS clinical staging is important to the clinician because it indicates allograft function.