Blebs and Bullae

Prevalence of blebs as high as 6% of young, healthy adults, although spontaneous rupture occurs only in 7.4 to 18 per 100,000.

Incidence of ruptured bulla is 26 per 100,000.

Increased incidence of primary disease in young males.

Increased prevalence with smoking (Hx, including tobacco and illicit substances), COPD, chronic bronchitis, cystic fibrosis, lung cancer, staphylococcal pneumonia, tuberculosis, Marfan syndrome, Ehlers-Danlos syndrome, alpha-1 antitrypsin deficiency, sarcoidosis, fiberglass pneumoconiosis, and BMI <22.

Pneumothorax

Bronchopleural fistulae

Caval compression of nonruptured giant bulla

Pulm Htn and RV failure

COPD

CV collapse from tension pneumothorax

Expanded dead-space ventilation

Inability to adequately ventilate due to bronchopleural fistula

Inadequate venous return from caval compression

Expansion of bulla leading to compressive effects or rupture

Bleb usually refers to a collection of air caused by ruptured alveoli within the visceral pleura without any other lining that is <1 cm in size.

Bullae >1 cm in size and arise from various sources, which cause destruction of lung parenchyma.

Nitrous oxide is contraindicated, and positive pressure ventilation should be avoided if possible.

• Nitrous oxide 35 times more soluble than nitrogen in blood. Because of this, nitrous oxide readily diffuses into any gas-filled cavity much more rapidly than nitrogen is absorbed, which leads to rapid expansion of pneumothoraces.

• In spontaneous ventilation, bullae are more compliant than normal lung tissue and preferentially fill. At higher pressures and volumes, bullae are much less compliant than normal lung and therefore have much higher peak pressures than normal tissue and are prone to rupture.