Math  /  Data & Statistics

QuestionYou have a trauma patient in the ER on 3 L nasal cannula. Their PaO 2 is 95 , hemoglobin is 4 , and SaO 2 is 95%95 \%. What is their CaO 2 ? 5.4 25.8 10.8 20.6

Studdy Solution

STEP 1

What is this asking? We need to calculate the total arterial oxygen content (CaO2CaO_2) in a patient's blood, given their partial pressure of oxygen, hemoglobin level, and oxygen saturation. Watch out! Don't forget to convert the hemoglobin level from g/dL to g/100mL, and remember to account for dissolved oxygen, even though it's a small part of the total oxygen content!

STEP 2

1. Calculate the oxygen bound to hemoglobin.
2. Calculate the dissolved oxygen.
3. Calculate the total arterial oxygen content.

STEP 3

Alright, let's break down this CaO2CaO_2 calculation!
First, we'll tackle the oxygen bound to hemoglobin.
The formula is: (1.34HbSaO2)(1.34 \cdot Hb \cdot SaO_2), where HbHb is the hemoglobin level and SaO2SaO_2 is the oxygen saturation.
This formula tells us how much oxygen each red blood cell can carry!

STEP 4

We're given Hb=4Hb = 4 g/dL, and we need it in g/100mL.
Since 1 dL = 100 mL, our hemoglobin level is already in the correct units!
Our SaO2SaO_2 is **95%**, which we'll use as **0.95** in the formula.

STEP 5

Plugging in the values, we get 1.3440.95=5.0921.34 \cdot 4 \cdot 0.95 = 5.092.
This tells us that **5.092 mL** of oxygen is bound to every **100 mL** of blood thanks to hemoglobin.

STEP 6

Next up: dissolved oxygen!
The formula is (PaO20.003)(PaO_2 \cdot 0.003), where PaO2PaO_2 is the partial pressure of oxygen.
This part of the calculation tells us how much oxygen is floating freely in the blood, not bound to hemoglobin.

STEP 7

We're given PaO2=95PaO_2 = 95 mmHg.
Plugging this in, we get 950.003=0.28595 \cdot 0.003 = 0.285.
So, **0.285 mL** of oxygen is dissolved in every **100 mL** of blood.

STEP 8

Finally, let's put it all together! CaO2CaO_2 is simply the sum of the oxygen bound to hemoglobin and the dissolved oxygen.
We add these two values to find the *total* oxygen content in the arterial blood.

STEP 9

Adding our results from the previous calculations, we have 5.092+0.285=5.3775.092 + 0.285 = 5.377.
Therefore, the CaO2CaO_2 is **5.377 mL/100mL** of blood.

STEP 10

The CaO2CaO_2 is approximately **5.4 mL/100mL**.
So the closest answer is 5.4.

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