Ch18 - Gas Exchange

BME 302

What is normal partial pressure of oxygen (Po)?

100 mmH0

What is normal partial pressure of CO2 (Pco2)?

40 mmHg

What influences alveolar gas exchange?

O2 reaching alveoli, Gas diffusion between alveoli and blood, adequate perfusion of alveoli

What is the main factor affecting inspired air composition?

Altitude

Hypoventilaltion

Low alveolar ventilation

Diffusion rate is proportional to;

surface area * concentration gradient * barrier permability

Diffusion rate is inversely proportional to:

1/distance²

What is the main factor that decreases in healthy adults in the diffusion formula?

Pressure gradient

What disease decreases surface area in the lungs?

Emphysema

What disease affects diffusion barrier permeability?

Fibrotic lung diseases

What diseases can increase diffusion distance?

Pulmonary edemaH

How does pulmonary BP increase?

Mitral valve dysfunction or left ventricular failure

What affects air to liquid gas diffusion?

Pressure gradient, solubility, temperature

What do gases dissolve into first when entering blood?

Plasma

Mass flow formula:

mass flow = concentration * volume flow

Oxygen consumption formula:

CO * (arterial oxygen content - venous oxygen content)

Where is oxygen stored in the blood

Plasma AND Hemoglobin

What determines how much O2 binds to hemoglobin?

Po2 in the plasma/RBCs and number of potential hemoglobin binding sites available in the RBCs

Percent saturation of hemoglobin:

(amount of O2 bound / max that could be bound) * 100

What are some factors that affect O2-Hb binding?

plasma pH, temperature, and Pco2

What affects oxygen dissolved in plasma?

Composition of inspired air, alveolar ventilation, O2 diffusion between alveolar and blood, and adequate perfusion of alveoli

How is CO2 stored in the blood?

Plasma (7%), Hb in RBC (23%), converted to HCO3 in RBC

Why is CO2 converted to HCO3- in blood?

Easy to transport and helps regulate blood pH