Anaesthesia Coffee Break Wests Zones | Respiratory Physiology
Jan 4, 2025
Explore the fascinating concept of West zones in lung physiology! Discover how different pressures affect blood flow in various zones, including the intriguing mechanics of the Starling resistor. Delve into Zone 1, where dead space occurs, and learn how positioning can shift zone dynamics. The discussion reveals how interstitial pressure in Zone 4 limits perfusion due to factors like edema. This insightful chat combines essential medical knowledge with practical implications for clinicians.
AI Snips
Chapters
Books
Transcript
Episode notes
Perfusion Depends On Pressures And Resistance
- West zones classify lung regions by interaction of alveolar, arterial and venous pressures to explain vertical perfusion differences.
- Blood flow equals arterial minus venous pressure divided by resistance, modified by external pressures (Starling resistor).
Zone 1 Creates Dead Space
- Zone 1 occurs when alveolar pressure exceeds arterial and venous pressures, causing little or no blood flow.
- This creates physiologic dead space and widens the gap between end-tidal CO2 and PaCO2.
Limit High Airway Pressures And Monitor Volume
- Avoid excessive alveolar pressures (high PEEP or high airway pressures) when possible to prevent creating Zone 1 dead space.
- Recognize hypovolemia or shock can lower pulmonary arterial pressure and convert regions into Zone 1.
