Simple compartmental model including soluble gas transport in the alveoli, transfer between the bronchial circulation and the conducting airways, and metabolism.

Description

  This is a simple model of the pulmonary system where the lung is subdivided into 
  compartments representing air spaces: dead space, peripheral bronchial tract, and 
  the alveolar space; blood volumes: upper airway mucus, pulmonary capillary, systemic 
  blood flow; and tissue space: whole body excluding the lungs. The upper airway mucus 
  layer resides along the peripheral bronchial tract and has a continuous blood flow 
  QM which effectively communicates with the gas in the bronchial tract. 	

Equations

• Ventilation

The alveolar compartment changes volume with ventilation. Prior to steady state, the lung undergoes tidal breathing, represented by a sinusoid

After a pre-determined number of breaths, a secondary maneuver is performed: prolonged exhale or rebreathing. For a prolonged exhalation maneuver, the lungs are brought quickly to total lung capacity (TLC), then drained at a constant rate to the residual volume (RV).

In a rebreathing maneuver, an external bag is attached and the subjects breaths a number of breaths, generally 8, directly into and out of a bag.

Compartmental Definitions The following compartments use conservation of mass equations to follow the concentration of the soluble gas tracer.

• Dead Space

• Peripheral Bronchial Compartment

• Alveolar Compartment

• Body Compartment

• Rebreathing Bag