Chapter 6, Problem 1RQ

Summary Introduction

Introduction:

Oxygen (O₂) in blood exerts a certain amount of partial pressure, which causes some of the oxygen to get dissolved in the blood. When the amount of oxygen in blood increases, the partial pressure also increases and it eventually increases the amount of dissolved oxygen. This is known as Henry’s law. It states that the concentration of dissolved oxygen in the blood is directly proportional to the partial pressure of oxygen. When written in the equation, the constant of proportionality is 0.003 mL/mmHg of oxygen/dL (milliliter per millimeter of mercury per deciliter) of the blood. Also, hemoglobin (Hb) plays an important role in determining the total amount of oxygen dissolved in the blood. The concentration of hemoglobin bound oxygen can be calculated by multiplying the factor 1.34 to the g/dl (gram per deciliter) of the hemoglobin present. The value obtained is for 100% oxygen saturation of blood.

Answer to Problem 1RQ

Correct answer:

The amount of total oxygen present in blood to be transported to the peripheral tissues is 16 mL/dL.

Explanation of Solution

Justification/Explanation for the correct answer:

Option (a) is, ‘16mL/dL.’ In the given case, the hemoglobin level of the patient is 14g/dL and the partial pressure of oxygen is 55mmHg (85 percent saturated with oxygen). Thus, the amount of oxygen that is transported to the peripheral tissues in every 100mL blood can be calculated as follows:

$\begin{array}{l}\text{Dissolved Oxygen}=\text{dissolved oxygen factor }\times \text{ partial pressure of oxygen}\hfill \\ \text{Dissolved Oxygen}=\text{0}\text{.003 mL}/\text{mmHg}/\text{dL }\times \text{ 55 mmHg}\hfill \\ \text{Dissolved Oxygen}=\text{0}\text{.165 mL}/{\text{dL O}}_{\text{2}}\hfill \end{array}$

$\begin{array}{l}\begin{array}{l}\text{Oxygen bound to hemoglobin}=\text{g}/\text{dL of Hb}\times {\text{O}}_2\text{ bound to Hb factor}\times \text{\% saturation of oxygen}\\ \text{Oxygen bound to hemoglobin}=\text{14 g}/\text{dL}\times \text{1}\text{.34}\times \text{0}\text{.85}\end{array}\hfill \\ \text{Oxygen bound to hemoglobin}=\text{15}\text{.946 mL}/{\text{dL O}}_{\text{2}}\hfill \\ \hfill \end{array}$

$\begin{array}{l}{\text{Total O}}_{\text{2}}\text{ to be transported}={\text{dissolved O}}_{\text{2}}+{\text{O}}_{\text{2}}\text{ bound to Hb}\hfill \\ {\text{Total O}}_{\text{2}}\text{ to be transported}=\text{0}\text{.165mL}/\text{dL}+\text{15}\text{.946mL}/\text{dL}\hfill \\ {\text{Total O}}_{\text{2}}\text{ to be transported}=\text{16}\text{.11 mL}/\text{dL}\hfill \\ {\text{Total O}}_{\text{2}}\text{ to be transported }=\text{~16 mL}/\text{dL}\hfill \end{array}$

Hence, option (a) is correct.

Explanation for incorrect answer:

Option (b) is, ‘17mL/dL.’ The total oxygen dissolved in blood to be transported to the peripheral tissues is not equal to 17 mL/dL. So, it is an incorrect option.

Option (c) is, ‘18mL/dL.’ In each 100 mL of blood, the dissolved oxygen to be transported is about 16 mL/dL. So, it is an incorrect option.

Option (d) is, ‘19mL/dL.’ The amount of oxygen to be transported to the peripheral tissues in 100 mL of blood is less than 19 mL/dL. So, it is an incorrect option.

Hence, options (b), (c), and (d) are incorrect.

Conclusion

Therefore, it can be concluded that the amount of oxygen dissolved in blood depends on the partial pressure of oxygen in the blood as well as on hemoglobin bound to the oxygen. The percent saturation of oxygen also affects the amount of oxygen dissolved in the blood, which is transported to the peripheral tissues in the body.