Question

How does Pulmonary edema affect gas exchange? I know that it
• Increases distance over which gases must exchange
• slows down gas exchange
• may result in respiratory failure
But I'm not sure about specifics.. can someone explain to me the details on the effect of fluid in lungs please? Thank you

Answer 1

By the process of diffusion the exchange of oxygen and carbon dioxide occurs in the alveolar-capillary membrane area. The relationship between ventilation (airflow) and perfusion (blood flow) affects the efficiency of the gas exchange. Normally there is a balance between ventilation and perfusion. However, certain conditions can offset this balance, resulting in impaired gas exchange. Altered blood flow from a pulmonary embolus or decreased cardiac output or shock can cause ventilation without perfusion. Conditions that cause changes or collapse of the alveoli impair ventilation, such as atelectasis, pneumonia, pulmonary edema, and adult respiratory distress syndrome (ARDS). Other factors affecting gas exchange include high altitudes, hypoventilation, and altered oxygen carrying capacity of the blood from reduced hemoglobin. Elderly patients have a decrease in pulmonary blood flow and diffusion as well as reduced ventilation in the dependent regions of the lung where perfusion is greatest. Chronic conditions such as chronic obstructive pulmonary disease (COPD) put these patients at greater risk for hypoxia. Other patients at risk for impaired gas exchange include those with a history of smoking or pulmonary problems, obesity, prolonged periods of immobility, and chest or upper abdominal incisions.
Related Factors

Altered O2 supply
Alveolar-capillary membrane changes
Altered blood flow
Altered oxygen-carrying capacity of blood