O2 transport and regulation

Ventilation-perfusion (V/Q) matching

refers to the coordination between the amount of air (ventilation) reaching the alveoli and the amount of blood (perfusion) flowing

For Successful Gas Exchange:

The sequence of oxygen movement

atmospheric O2 determines

Alveolar O2 determines

Plasma O2 determines

HbO2

What is responsible for these pressure gradients?

Living and existing dirives gas exchange

Oxygen and carbon dioxide

O2 enters co2 leaves pulmonary capillary

For Successful Gas Exchange:

Oxygen needs to reach alveoli

Oxygen needs to diffuse across

Oxygen needs to reach blood

In peripheral/systemic

To optimize tissue oxygenation

Vasoconstriction: high oxygen low carbon dioxide

Vasodilation(run from tiger): high co2 and low o2 because uses oxygen for metabolism

In pulmonary

To optimize gas exchange

Vasoconstriction: high co2 and low o2

Vasodilation: high o2 and low co2

Lung’s goal

is to not “waste” perfusion to poorly ventilated areas.

Ventilation and perfusion

Ventilation/perfusion

V/Q

Ideal is 0.8

PAO2

alveolar oxygen pressure

PaO2

arterial oxygen pressure

For gas exchange to be effective,

blood flow (perfusion) must “match” air flow (ventilation) right to left heart

Underventilated

High PAco2 low PAo2

Arterioles constrict

Well ventilated

arterioles dilate

TPV=

RR x Tidal Volume

Avg RR = 12-18 br/min (~15br/min)

Avg TV/breath = 500ml/br

Avg TPV = 6 – 9 L/min

Ventilation

Air flow

Avg alveolar ventilation ~ 4 L/min

Perfusion

Blood flow

Avg = 5 L/min

Low V/Q

High V/Q

V/Q = 0

V/Q =∞

Ventilation issues

Perfusion issues

Shunt

The lower the V/Q ratio, the closer the outflowing blood composition gets to mixed venous blood

Alveolar gas

The higher the V/Q ratio, the closer the outflowing blood composition

Dead space

Memorize