If a patient has 7 g% Hb, an SaO₂ of 65 percent, and a PaO₂ of 175 mm Hg, approximately how much oxygen is being transported to the peripheral tissues in each 100 ml of blood? A) 6.6 vol% O₂ B) 9.4 vol% O₂ C) 10.5 vol% O₂ D) 11.8 vol% O₂ E) 12.7 vol% O₂

Question

Quizplus · Accepted Answer

The first step to solving this problem is to calculate the total oxygen-carrying capacity of the blood, which is determined by the amount of hemoglobin (Hb) present in the blood.

In this case, the patient has a Hb level of 7 g%, which corresponds to a Hb concentration of 70 g/L (since 1 g% = 10 g/L). Each gram of Hb can bind to 1.34 mL of oxygen, so the total oxygen-carrying capacity of the blood can be calculated as follows:

Total O₂ content = (Hb concentration x 1.34 mL O₂/g Hb) + (PaO₂ x 0.003 mL O₂/mm Hg)
Total O₂ content = (70 g/L x 1.34 mL O₂/g Hb) + (175 mm Hg x 0.003 mL O₂/mm Hg)
Total O₂ content = 93.8 mL O₂/L blood

Next, we need to calculate how much of the total oxygen-carrying capacity is actually being used to transport oxygen to the peripheral tissues. This is determined by the saturation of hemoglobin with oxygen, which is represented by the SaO₂.

In this case, the patient has a SaO₂ of 65 percent, which means that only 65 percent of the available Hb sites are bound to oxygen. The remaining Hb sites are either empty or bound to carbon dioxide or other gases.

To calculate how much oxygen is being transported to the peripheral tissues per 100 mL of blood, we can use the following equation:

O₂ content = (SaO₂ x total O₂ content) / 100

Plugging in the values we have, we get:

O₂ content = (65 x 93.8) / 100
O₂ content = 60.9 mL O₂/100 mL blood

Finally, we need to express the amount of oxygen as a percentage of the total blood volume, which is referred to as the oxygen saturation or O₂sat. This is calculated as follows:

O₂sat = (O₂ content / total blood volume) x 100

Plugging in the values we have, we get:

O₂sat = (60.9 mL O₂/100 mL blood) / 0.93 L/L
O₂sat = 0.656 x 100
O₂sat = 65.6 vol% O₂

Therefore, the approximate amount of oxygen being transported to the peripheral tissues in each 100 ml of blood is 6.6 vol% O₂, which corresponds to answer choice A.

If a Patient Has 7 G% Hb, an SaO2 of 65

If a Patient Has 7 G% Hb, an SaO₂ of 65