5. Explain how oxygen content accurately describes oxygen delivery to the tissue

Question

5. Explain how oxygen content accurately describes oxygen delivery to the tissues and explain why PaO2, SaO2, and hemoglobin (Hb) are often unreliable measures of total oxygen delivery to the tissues. 

6. Explain the result of alveolar-capillary shunts in the production of a venous admixture and explain the role hypoxemia plays in the development of these intrapulmonary shunts.

7. Suggest specific complicating inter-atrial sequelas for atrial septal defects (ASD) and relate

    the generalized effect on hemodynamic measurements.

8. Indicate the hemodynamic effect of morbid obesity on pressure measurements and determine

    at least three clinical symptoms that are indicated as risks (complications) for obesity.

Explanation / Answer

5.

the tissue oxygenation depends upon the rate of oxygen delivered to the tissues (DO2) and the rate of oxygen consumed by the tissues (VO2). (DO2) is the volume of oxygen delivered to the systemic vascular bed per minute and is the product of cardiac output (CO) and arterial oxygen concentration (CaO2). So,  DO2 = CO x CaO2.

Hence DO2= CO x CaO2, oxygen delivery can be compromised as much by a low hemoglobin concentration or low cardiac output as by a fall in the SaO2. The arterial oxygen content is based on the amount of hemoglobin (Hb), the saturation of hemoglobin with oxygen (SaO2), and the amount of oxygen that each gram of hemoglobin can carry, which has been calculated to be between 1.32 and 1.39, depending on the circumstances.

CaO2=(1.34 X Hgb X SaO2) + (0.003 X PaO2)

Therefore, oxygen delivery can be affected by changes in cardiac output as well as changes in the oxygen saturation of hemoglobin, the amount of hemoglobin available, and to a much smaller extent the PaO2 (the amount of oxygen dissolved in the blood).

6.

The blending of unoxygenated blood with oxygenated blood is known as venous admixture. There are two reasons for venous admixture: a shunt, and a low Va/Q proportion. The aggregate sum of venous admixture because of an anatomic shunt and a low Va/Q proportion measures up to physiological shunt and speaks to the aggregate sum of wasted blood that does not get completely oxygenated.

A pneumonic shunt frequently happens when the alveoli load with liquid, making parts of the lung be unventilated despite the fact that they are still perfused. Intrapulmonary shunting is the primary driver of hypoxemia (insufficient blood oxygen) in aspiratory edema and conditions, for example, pneumonia in which the lungs end up solidified.

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