Oxygen Hemoglobin Dissociation Curve Lecture Notes

Introduction

• Lecturer: Eddie Watson from ICU Advantage
• Goal: Simplify complex critical care subjects for better understanding
• Invitation to subscribe and access lesson notes on YouTube and Patreon
• Additional resources: quizzes, gift card opportunities, and support options available at icuadvantage.com

Key Concepts

Relationship of Oxygen in Blood

• Explores how oxygen levels affect its availability in the body
• Represented by the oxygen hemoglobin dissociation curve

Saturation

• Refers to the amount of oxygen bound to hemoglobin
• Measured via pulse oximetry (SpO2) or blood gas analysis
• Red blood cells transport oxygen using hemoglobin
• Hemoglobin structure: four subunits (2 alpha, 2 beta) with iron binding sites
  • Maximum of four oxygen molecules can bind per hemoglobin molecule
  • Each red blood cell contains approximately 270 million hemoglobin molecules

Cooperativity

• Binding of oxygen to one hemoglobin subunit increases affinity for additional oxygen
• Fully saturated hemoglobin means all four subunits are bound with oxygen

Partial Pressure of Oxygen

• Defined as the pressure of oxygen gas available
• More oxygen = higher partial pressure (PaO2)
• Dissolved oxygen contributes minimally to overall availability compared to hemoglobin-bound oxygen

Oxygen Hemoglobin Dissociation Curve

• Graph with:
  • X-axis: Partial pressure of oxygen
  • Y-axis: Percent hemoglobin saturation
• S-shaped (sigmoid) appearance
• Represents the saturation levels at various oxygen availabilities
  • Example: At 50 mmHg partial pressure, saturation ~85%
• Plateau phase at high saturation levels (near 100%) indicates limited increase in saturation despite more oxygen availability

Physiological Shifts in the Curve

Right Shift

• Indicates decreased affinity of hemoglobin for oxygen, easier unloading
• Example:
  • At 50 mmHg PaO2, saturation drops to ~75%
• Causes of right shift include:
  • Increased CO2
  • Increased acidosis (lower pH)
  • Increased 2,3-DPG (byproduct of glycolysis)
  • Increased temperature
• Areas of increased unloading: muscle tissue, during exercise, placenta

Left Shift

• Indicates increased affinity of hemoglobin for oxygen, less unloading
• Example:
  • At 50 mmHg PaO2, saturation rises to ~90%
• Causes of left shift include:
  • Decreased CO2
  • Decreased acidosis (higher pH)
  • Decreased 2,3-DPG
  • Decreased temperature
  • Fetal hemoglobin (higher affinity for oxygen)

Clinical Implications

• Physiological shifts can impact oxygen delivery and binding
• Examples:
  • Acidosis may hinder oxygen binding in the lungs
  • Correcting acidosis may impede oxygen unloading in tissues
• Understanding these shifts is crucial for managing critically ill patients

Conclusion

• Importance of understanding the oxygen hemoglobin dissociation curve and physiological shifts
• Encouragement to engage with content (like, comment, subscribe)
• Appreciation for support from YouTube and Patreon members
• Invitation to follow for future lessons and additional resources.