OTHER RESPIRATORY SYSTEM FUNCTIONS

1. Acid-Base Balance

Due to acid forming potential of CO2 and buffering capacity of hemoglobin

CO2 + H2O = H2CO3 (carbonic acid) = H⁺ + HCO₃^-
Hb + H⁺ = HHb (buffer)

Acid-Base balance covered with kidney

2. Water Balance

Ventilation saturates inhaled air; the water is lost on exhalation; minor pathway of water loss in humans (10-20% of total body water loss)

3. Heat Balance

respiratory water evaporation requires heat (latent heat of vaporization); generally minor pathway of heat loss in humans (5-10% of total body heat loss)

4. Filter Blood

remove microemboli from the circulation but large pulmonary emboli can be fatal

microemboli = small circulating foreign bodies, especially thromboemboli

5. Miscellaneous Functions

a. speech

b. exchange of other volatile substances (e.g. alcohol: the amount of alcohol in 2L of alveolar gas equals the amount of alcohol in 1 ml of blood)

c. Clearing airways (e.g. coughing and sneezing)

d. Endocrine and metabolic functions (e.g. angiotensin converting enzyme)