Physiological dead space

Physiological dead space refers to the portion of the respiratory system where gas exchange does not occur. It includes the anatomical dead space, which is the volume of the conducting airways, and the alveolar dead space, which is the volume of alveoli in which there is no gas exchange due to inadequate perfusion.

Definition

Physiological dead space is defined as the volume of the lungs that does not participate in gas exchange. It is the sum of the anatomical dead space and the alveolar dead space. The anatomical dead space is the volume of the conducting airways, which includes the trachea, bronchi, and bronchioles. The alveolar dead space is the volume of alveoli in which there is no gas exchange due to inadequate perfusion.

Measurement

The physiological dead space can be measured using the Bohr equation, which calculates the ratio of the volume of carbon dioxide in the alveoli to the volume of carbon dioxide in the expired air. This ratio is then multiplied by the tidal volume to give the physiological dead space.

Clinical significance

An increase in physiological dead space is a common feature of many lung diseases, including chronic obstructive pulmonary disease (COPD), pulmonary embolism, and acute respiratory distress syndrome (ARDS). It can also increase in conditions that affect the blood supply to the lungs, such as heart failure.

See also

• Anatomical dead space
• Alveolar dead space
• Bohr equation
• Chronic obstructive pulmonary disease
• Pulmonary embolism
• Acute respiratory distress syndrome

Physiological dead space Resources
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