Respiratory Therapy Study Guide: Chapters 11-12 Notes

CO. Transport Mechanisms

• Bicarbonate Buffer System (main method):
  • CO2 + H2O \rightleftharpoons H2CO3 \rightleftharpoons H^+ + HCO_3^-
• Other methods:
  • Dissolved in plasma
  • Bound to hemoglobin
  • Incorrect method: Transformation into a chlorine ion

Body Compensation for Hypoxia

• The body responds by increasing cardiac output and sometimes respiratory rate to deliver more oxygen.

Key Concepts

• Understand the difference between oxygen content (how much is in the blood) and oxygen saturation (how much hemoglobin is carrying oxygen).
• Practice interpreting gas exchange concepts, such as what happens during CO poisoning or hypoxia.
• Review pressure relationships in breathing: mouth-alveoli-pleural space.
• Be familiar with the basic gas laws and how they apply to ventilation mechanics.

Airflow Patterns in the Lungs

• Laminar Flow:
  • Smooth, parallel layers of air typically seen in smaller airways.
• Turbulent Flow:
  • Erratic, choppy movement of air, occurs with high airflow rates or in larger airways.
• Tracheobronchial/Transitional Flow:
  • Combination of laminar and turbulent flow often occurring after airway branches.

Pressure Gradients and Air Movement

• Inspiration:
  • Air moves from higher pressure at the mouth to lower pressure in the alveoli.
  • This is due to diaphragm contraction, which increases thoracic volume and decreases pressure in the lungs

Lung Compliance

• Static Compliance:
  • Measured when no air is moving (at end-inspiration).
  • Reflects true elasticity of lungs and chest wall.
• Dynamic Compliance:
  • Measured during active breathing.
  • Influenced by airway resistance.

Pressure-Volume Relationship

• Peak Airway Pressure:
  • Highest pressure during inspiration
  • Found at the top of the pressure-volume curve.
• Transpulmonary Pressure:
  • Difference between alveolar and pleural pressure
  • Indicates force needed to keep alveoli open.
• Hooke's Law:
  • Pressure is directly proportional to volume - applies to lung elasticity.

Oxygenation and Hemoglobin

• Hypoxemia:
  • Low oxygen levels in the blood (PaO_2).
• Hypoxia:
  • Low oxygen available to tissues (may be caused by hypoxemia).
• Cyanosis:
  • Bluish skin or mucous membranes due to poor oxygenation.

Oxygen Transport

• Most O_2 is transported bound to hemoglobin in red blood cells.
• Oxyhemoglobin Dissociation Curve:
  • At PaO_2 > 60 mm Hg, hemoglobin is ~90% saturated.
  • The curve flattens, meaning increased O_2 has minimal effect on saturation.

Carbon Monoxide (CO) Effects

• CO binds to hemoglobin to form carboxyhemoglobin, which:
  • Prevents O_2 from binding.
  • Reduces O_2 delivery to tissues.
  • Does not change PaO_2, making it difficult to detect on pulse oximetry.