Clase 41 Fisiología Respiratoria - Transporte de O2 y CO2 en la sangre y tejidos (IG:@doctor.paiva)

Overview of Respiratory Physiology Class

In this class, the focus is on the transport of oxygen and carbon dioxide in the blood and tissues. Generalities about oxygen and carbon dioxide transport, hemoglobin's role, oxygen dissociation curve, Bohr effect, and Haldane effect are discussed.

Transport of Blood Gases

• Clarification on Arterial and Venous Ends: The correct terminology for arterial and venous ends is explained to avoid confusion between the artery pulmonar (carrying deoxygenated blood) and vena pulmonar (carrying oxygenated blood).

• Understanding Arteries vs. Veins: Explanation of why the pulmonary artery carries deoxygenated blood despite being called an artery due to its origin from the heart.

• Circulatory System Overview: Differentiation between pulmonary circulation (circulación menor or pulmonar) and systemic circulation (circulación mayor or systèmes).

Oxygen Transport in Alveoli-Capillary Membrane

• Oxygen Exchange Process: Details on how deoxygenated blood in the pulmonary artery gets oxygenated in alveoli-capillary membrane with a shift in partial pressures.

• Bypassing Alveolar-Capillary Membrane: Discussion on 2% of blood bypassing alveolar-capillary membrane leading to physiological shunt towards arterial blood without oxygenation.

• Mixing of Deoxygenated Blood: Explanation of how deoxygenated blood from bronchial circulation mixes with oxygenated blood before reaching the left atrium as venous mixture.

Tissue Oxygenation Process

• Oxygen Delivery to Tissues: Description of tissue oxygen levels varying from interstitial space to intracellular levels crucial for cellular functions.

• Cellular Oxygen Utilization: Insights into how tissues utilize oxygen based on factors like blood oxygen levels, flow rate, and tissue metabolic demands.

Understanding Gas Exchange in the Body

In this section, the discussion revolves around the dynamics of gas exchange in the body, focusing on oxygen and carbon dioxide transport and their impact on tissue oxygenation.

Gas Exchange Dynamics

• The blood arterial pressure for carbon dioxide is 40 mmHg, while tissues release carbon dioxide into the interstitium, resulting in a partial pressure of 45 mmHg before returning to venous blood at 45 mmHg.

• Carbon dioxide diffuses faster than oxygen due to its properties, facilitating efficient gas exchange from capillaries to alveoli.

• While oxygen is taken up by hemoglobin in arterial blood for transport to tissues, carbon dioxide is released during exhalation as it diffuses from tissues to capillaries.

Regulation of Gas Partial Pressures

• Contrary to oxygen regulation, an increase in blood flow decreases tissue carbon dioxide partial pressure. Conversely, decreased metabolism or increased blood flow elevates tissue CO2 levels.

• Metabolic changes directly influence tissue CO2 levels; reduced metabolism lowers CO2 partial pressure while increased metabolic activity raises it.

Hemoglobin Function and Oxygen Transport

• Hemoglobin acts as an essential carrier of oxygen in the blood. Each hemoglobin molecule can bind reversibly with four molecules of oxygen due to its structure.

• Approximately 97% of oxygen is transported by hemoglobin in the blood. The remaining 3% dissolves in plasma and other cells.

Oxygen Transport Calculation

• With each gram of hemoglobin capable of binding up to 1.34 ml of oxygen, calculations show that under normal conditions, about 19.4 ml of oxygen are transported per 100 ml of blood.

• Arterial and venous blood exhibit different levels of hemoglobin saturation based on their respective oxygen pressures: arterial at 97% saturation and venous at 75%.

Monitoring Oxygen Saturation Levels

This segment delves into methods for monitoring oxygen saturation levels using pulse oximetry devices and understanding the significance behind these measurements.

Pulse Oximetry Monitoring

• Pulse oximeters measure hemoglobin's percentage saturation with oxygen rather than arterial oxygen partial pressure. They provide valuable insights into respiratory function alongside heart rate monitoring.

• Blood contains approximately 15 grams of hemoglobin per 100 ml, with each gram capable of binding up to a maximum amount of oxygen molecules for efficient transport.

Interpretation and Clinical Application

• Calculations based on hemoglobin's binding capacity reveal that under typical conditions, around 19.4 ml of oxygen are transported per every 100 ml volume within the bloodstream.

Intense Exercise and Oxygen Utilization

The discussion delves into the utilization of oxygen during intense exercise, focusing on the percentage of oxygen remaining in venous blood after intense cellular activity.

Intense Exercise and Oxygen Utilization

• During intense exercise, cells can utilize up to 15 ml of oxygen per 100 ml of blood, with an average utilization coefficient of 75%.

• In cases of very intense exercise, utilization coefficients close to one hundred percent have been recorded.

• Hemoglobin is referred to as oxyhemoglobin when bound to oxygen and deoxyhemoglobin when oxygen is not bound. This distinction contributes to the color variation between arterial and venous blood.

• Hemoglobin acts as a buffer, maintaining oxygen saturation levels even when partial pressure decreases.

Factors Affecting Oxygen-Hemoglobin Dissociation Curve

This segment explores factors that influence the affinity of hemoglobin for oxygen, affecting the dissociation curve in either direction.

Factors Affecting Oxygen-Hemoglobin Dissociation Curve

• Factors can shift the curve left (increased affinity) or right (decreased affinity), impacting oxygen release from hemoglobin.

• Rightward shifts indicate increased oxygen release from hemoglobin into tissues due to factors like high hydrogen ions or low pH levels.

• Leftward shifts signify enhanced oxygen binding by hemoglobin, influenced by factors opposite to those causing rightward shifts.

pH Influence on Oxygen-Hemoglobin Dissociation Curve

The impact of pH variations on the dissociation curve's position and its implications for oxygen binding are discussed.

pH Influence on Oxygen-Hemoglobin Dissociation Curve

• pH alterations affect the dissociation curve; acidic conditions shift it rightwards while alkaline conditions shift it leftwards.

Bohr Effect and Carbon Dioxide Release

The Bohr effect elucidates how carbon dioxide release influences pH changes and subsequently affects hemoglobin-oxygen binding.

Bohr Effect and Carbon Dioxide Release

• Carbon dioxide combines with water in cells, forming carbonic acid. This process increases hydrogen ions in blood, shifting the dissociation curve rightwards.

• In lungs where carbon dioxide is released, a leftward shift occurs due to decreased hydrogen ions and carbon dioxide levels. This enhances oxygen binding by hemoglobin.

Exercise Impact on Oxygen Binding

The effects of exercise-induced metabolic changes on pH levels and temperature altering hemoglobin-oxygen affinity are explored.

Exercise Impact on Oxygen Binding

Understanding Cellular Metabolism and Gas Transport in the Body

In this section, the discussion revolves around the utilization of oxygen by cells through ATP (adenosine triphosphate) conversion and its role in cellular metabolism. The relationship between ATP concentrations, oxygen utilization, and metabolic rates is explored.

Cellular Metabolism and Oxygen Utilization

• Increased cellular energy demand leads to higher ADP concentrations, influencing oxygen utilization rates determined by ATP levels.

• Oxygen utilization by cells is dependent on ATP concentrations; higher ATP levels result in increased oxygen usage due to elevated metabolic demands.

• Lower ATP concentrations lead to reduced oxygen utilization, affecting cellular metabolic rates when values drop below critical levels.

Transport of Carbon Dioxide in the Bloodstream

This segment delves into the mechanisms of carbon dioxide transport within the bloodstream, focusing on its various forms and interactions with hemoglobin for efficient exchange.

Carbon Dioxide Transport Mechanisms

• Concentrations of carbon dioxide directly impact pH balance: higher CO2 levels increase hydrogen ions, lowering pH (acidic), while lower CO2 levels decrease hydrogen ions, raising pH (alkaline).

• Carbon dioxide is transported primarily as bicarbonate (70%), carbamino compounds with hemoglobin (23%), and dissolved CO2 (7%) within erythrocytes.

Role of Hemoglobin in Gas Exchange

The focus shifts to hemoglobin's role in gas exchange processes, particularly how it facilitates carbon dioxide transport through reversible binding mechanisms.

Hemoglobin-Mediated Gas Exchange

• Hemoglobin binds reversibly with carbon dioxide in tissues forming carbaminohemoglobin; this weak bond allows easy release of CO2 at alveoli due to lower partial pressure.

• Carbon dioxide reacts with water in erythrocytes catalyzed by carbonic anhydrase enzyme to form bicarbonate ions rapidly for efficient transport.

Regulation of Oxygen and Carbon Dioxide Levels

This part discusses the regulation of oxygen and carbon dioxide levels within blood circulation concerning their partial pressures across different physiological states.

Regulation Mechanisms

• Arterial blood carries 40 mmHg of CO2 while venous blood contains 45 mmHg; tissue capillaries have 52 ml/100 ml blood CO2 content compared to pulmonary capillaries' 48 ml/100 ml.

Understanding Gas Exchange in the Body

The transcript delves into the process of gas exchange in the body, focusing on how oxygen and carbon dioxide interact with hemoglobin to facilitate respiration.

Hemoglobin Interaction with Gases

• Hemoglobin primarily interacts with carbon dioxide and hydrogen.

• Oxygen binds to hemoglobin only in the lungs.

• Two ways for carbon dioxide movement:

• Oxygen binding releases hydrogen ions, creating an acidic environment that reduces carbon dioxide affinity for hemoglobin.

• Bicarbonate combines with released hydrogen ions to form carbonic acid, leading to dissociation into carbon dioxide and water.

Haldane Effect vs. Bohr Effect

• Both effects occur simultaneously due to the enzyme carbonic anhydrase.

• Haldane effect is more crucial for transporting carbon dioxide than the Bohr effect for oxygen transport.

• Key difference:

• Haldane effect: Carbon dioxide and hydrogen ions affect hemoglobin's oxygen affinity.