life science
M.A. Lung/PHYO2202/Respiration/13-14
VENTILATION
．
Pulmonary Ventilation (V)
It is the amount of air moved into or out of the lungs per minute; normal value is about 6 L/min.
．
V = f x TV
where f, frequency of breathing (breaths/min)
TV, tidal volume (L)
．
Alveolar Ventilation (VA)
It is the amount of air reaching the functioning alveoli (exchange surface) per minute; normal value is about 4.2 L/min.
．
VA = f x VA or f x (TV - VD)
where VA, volume of air reaching the functioning alveoli, L.
VD, volume of dead space, L.
．
PACO2 - VA Relationship
At steady state, amount of CO2 exhaled per minute equals to amount of CO2 produced per minute.
At a constant level of CO2 production, the PACO2 varies inversely with the level of alveolar ventilation. ．
PAO2 - VA Relationship
At steady state, the amount of O2 uptake per minute equals to the amount of O2 consumed per minute. At a constant level of O2 consumption and a fixed inspired O2 concentration, there is a direct relationship between PAO2 and the level of alveolar ventilation.
Physiological Dead Space Volume (VD)
It is the space in the lungs where gas exchange cannot take place. It oncludes:
1.
2.
Anatomical Dead Space - those parts of the respiratory tract (nose, pharynnx, trachea, bornchi, bronchioles) which act as passageways.
Alveolarl Dead Space – alveolar space that does not receive blood supply and/or space in which ventilation is in excess of the need to arterialize the blood.
Learning objectives:
You should now be able to:
1.
define pulmonary ventilation and state the formula relating pulmonary ventilation, tidal volume and breathing frequency.
2.
define alveolar ventilation and state the formula for calculating alveolar ventilation.
3.
state the effects of alveolar ventilation on PCO2 and PO2 in the body.
4.
define physiological dead space.
4
M.A. Lung/PHYO2202/Respiration/13-14
PULMONARY GAS DIFFUSION
Simultaneous processes of pulmonary
VENTILATION
．
Pulmonary Ventilation (V)
It is the amount of air moved into or out of the lungs per minute; normal value is about 6 L/min.
．
V = f x TV
where f, frequency of breathing (breaths/min)
TV, tidal volume (L)
．
Alveolar Ventilation (VA)
It is the amount of air reaching the functioning alveoli (exchange surface) per minute; normal value is about 4.2 L/min.
．
VA = f x VA or f x (TV - VD)
where VA, volume of air reaching the functioning alveoli, L.
VD, volume of dead space, L.
．
PACO2 - VA Relationship
At steady state, amount of CO2 exhaled per minute equals to amount of CO2 produced per minute.
At a constant level of CO2 production, the PACO2 varies inversely with the level of alveolar ventilation. ．
PAO2 - VA Relationship
At steady state, the amount of O2 uptake per minute equals to the amount of O2 consumed per minute. At a constant level of O2 consumption and a fixed inspired O2 concentration, there is a direct relationship between PAO2 and the level of alveolar ventilation.
Physiological Dead Space Volume (VD)
It is the space in the lungs where gas exchange cannot take place. It oncludes:
1.
2.
Anatomical Dead Space - those parts of the respiratory tract (nose, pharynnx, trachea, bornchi, bronchioles) which act as passageways.
Alveolarl Dead Space – alveolar space that does not receive blood supply and/or space in which ventilation is in excess of the need to arterialize the blood.
Learning objectives:
You should now be able to:
1.
define pulmonary ventilation and state the formula relating pulmonary ventilation, tidal volume and breathing frequency.
2.
define alveolar ventilation and state the formula for calculating alveolar ventilation.
3.
state the effects of alveolar ventilation on PCO2 and PO2 in the body.
4.
define physiological dead space.
4
M.A. Lung/PHYO2202/Respiration/13-14
PULMONARY GAS DIFFUSION
Simultaneous processes of pulmonary