dead space ventilation
Ventilation of lung areas where no gas exchange occurs, including anatomical and physiological dead space.
Full Definition
Dead space ventilation refers to the portion of each breath that does not participate in gas exchange. It includes anatomical dead space (conducting airways) and physiological dead space (alveolar areas with poor perfusion). Normal dead space represents about 25-30% of tidal volume. Increased dead space occurs with pulmonary embolism, ARDS, or ventilation-perfusion mismatch, leading to inefficient ventilation and potential hypercapnia. Respiratory therapists monitor dead space fraction (VD/VT ratio) to assess ventilation efficiency and adjust ventilator settings accordingly. High dead space ventilation may require increased minute ventilation to maintain adequate CO2 elimination.
Usage
Usage note: Often expressed as VD/VT ratio; distinguish from total minute ventilation in calculations.
In Context
- "Increased dead space ventilation contributed to the patient's persistent hypercapnia." — Arterial blood gas interpretation
- "The VD/VT ratio of 0.65 indicated significant dead space ventilation requiring ventilator adjustment." — Respiratory mechanics assessment