Alveolar volume

Decrease in lung capacity, alveolar volume, and diffusing capacity for carbon monoxide values remained depressed for at least 72 h after last exposure. Persistent inflammation of proximal portion of alveolar ducts and adjacent alveoli. 

Start with the theoretical lungs shown in the figure and remember that each Vt has a component that is dead space ( Vd) and a remainder that must take part in gas exchange at the alveolus (Vt - Vd). This is the alveolar volume. 

Cotes, J.E., Dabbs, J.M., Evans, M.R., and Holland, P., Effect of CS aerosol upon lung transfer and alveolar volume in healthy men, Q.J. Exp. Physiol., 57, 199-206, 1972a. 

Mechanical restriction caused by chest bellows malfunction may result from chest wall or skeletal deformity, loss of neuromuscular function, fibrosis of the pleural space, and abdominal overdistension causing upward displacement of the diaphragm, as well as decreased diaphragm movement. The most common pulmonary function pattern seen in these patients is a decrease in TLC and VC with only a slight decrease in RV. The RV is maintained in these diseases because lung compliance remains normal. The Dlco is normal or only minimally reduced, and the Dlco a (corrected for alveolar volume) is normal. The RV/TLC ratio is often increased in patients with restrictive chest bellows disease. Patients with neuromuscular disease also have reduced respiratory muscle function with a reduction in their MIP. 

Activated neutrophils and platelets adhere to the pulmonary capillary endothelium, initiating multiple inflammatory cascades with a release a variety of toxic substances. There is diffuse pulmonary endothelial cell injury, increased capillary permeability, and alveolar epithelial cell injury. Consequently, interstitial pulmonary edema occurs and gradually progresses to alveolar flooding and collapse. The end result is loss of functional alveolar volume, impaired pulmonary compliance, and profound hypoxemia. ... 

Studies measuring exhaled nitric oxide (NO) at several exhalation flow rates have revealed that the alveolar NO concentration correlates negatively with Dlco. vital capacity, and alveolar volume, suggesting that it may be a marker of disease severity (53). 

Fig. 3.3.5. Vital capacity and residual volume expressed as percentage of predicted total lung capacity. Worker 3 has a large residual volume and a preserved vital capacity, suggesting that any airflow collapse was insufficient to limit expiration. His alveolar volume (from a 10-s helium dilution breath hold) was 7.621 and his plethysmographic volume 8.571, a 0.95-1 difference showing some increased air-trapping. Worker 4 shows similar results with an alveolar volume (from a 10-s helimn dilution breath hold) of 5.981 and a plethysmographic volume 6.931, also a 0.95-1 difference showing some increased air-trapping...

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