Total Oxygen Content Calculations

Questions and Answers

What is the formula for Total Oxygen Content - Arterial (CaO2)?

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

Calculate CaO2 if Hgb = 15 g/dl, SaO2 = 97%, and PaO2 = 100.

19.8 vol%

What is the formula for Total Oxygen Content - Mixed Venous (CvO2)?

CvO2 = (1.34 x Hgb x Svo2) + (PvO2 x 0.003)

Calculate CvO2 if Hgb = 15 g/dl, SvO2 = 75%, and PvO2 = 40 mmHg.

15.2 vol% Signup and view all the answers

What is C(a-v)O2?

CaO2 - CvO2 Signup and view all the answers

Calculate C(a-v)O2 if CaO2 = 20 vol% and CvO2 = 15 vol%.

5 vol% Signup and view all the answers

What is the normal Deadspace/Tidal Volume Ratio (Vd/Vt)?

33% Signup and view all the answers

What is Bohr's Equation?

Vd/Vt = (PaCO2 - PeCO2) / PaCO2 Signup and view all the answers

Calculate PAO2 with PB = 760 mmHg, PH2O = 47 mmHg, FIO2 = 21%, and PaCO2 = 40 mmHg.

100 mmHg Signup and view all the answers

What is the formula to calculate Percent Solution?

V1C1 = V2C2 Signup and view all the answers

How much do you need to add to 15 mL of 20% Mucomyst to achieve a 15% solution?

5 mL Signup and view all the answers

What is the formula for Alveolar Ventilation (VA)?

VA = f(Vt - Vd) Signup and view all the answers

Calculate VA if f = 12, Vt = 500 mL, and Vd = 150 mL.

4200 mL/min Signup and view all the answers

What is the formula for calculating Ideal Body Weight (IBW) for MEN?

IBW = 106 + 6 for each inch over 5' Signup and view all the answers

What does the Classic Shunt Equation (Qs/Qt) calculate?

Qs/Qt = (CcO2 - CaO2) / (CcO2 - CvO2) Signup and view all the answers

When should you use the Classic Shunt Equation?

When the patient is on a FIO2 = 30%. Signup and view all the answers

What is the equation for the Modified Shunt Equation (Qs/Qt)?

Qs/Qt = P(A-a)O2 x 0.003 / [P(A-a)O2 x 0.003 + C(a-v)O2] Signup and view all the answers

When should you use the Modified Shunt Equation?

When the PO2 is ≥ 150 mmHg on any given FIO2. Signup and view all the answers

What is Static Compliance (Cst)?

Cst = corrected Vt / (Pplat - PEEP) Signup and view all the answers

What is the formula for Cylinder Duration (gas)?

Cylinder Duration = PSI x tank factor / liter flow Signup and view all the answers

What is the formula for calculating Percent Body Humidity?

Content / 44 mg/L times 100 = % Body Humidity Signup and view all the answers

Study Notes

Total Oxygen Content - Arterial (CaO2)

CaO2 formula: CaO2 = (1.34 x Hgb x SaO2) + (PaO2 x 0.003)
Normal hemoglobin (Hgb): 12-16 g/dl
Normal arterial Hgb saturation (SaO2): >92%
Normal partial pressure of oxygen in arterial blood (PaO2): >80 mmHg (60-100 mmHg)

Total Oxygen Content Calculation Examples

For Hgb = 15 g/dl, SaO2 = 97%, PaO2 = 100 mmHg, CaO2 = 19.8 vol%

Total Oxygen Content - Mixed Venous (CvO2)

CvO2 formula: CvO2 = (1.34 x Hgb x SvO2) + (PvO2 x 0.003)
Normal venous Hgb saturation (SvO2): 70-75%
Normal partial pressure of oxygen in venous blood (PvO2): 37-43 mmHg

Mixed Venous Oxygen Content Calculation Example

For Hgb = 15 g/dl, SvO2 = 75%, PvO2 = 40 mmHg, CvO2 = 15.2 vol%

Arterial-Mixed Venous Oxygen Content Difference (C(a-v)O2)

C(a-v)O2 formula: C(a-v)O2 = CaO2 - CvO2

C(a-v)O2 Calculation Example

Given CaO2 = 20 vol%, CvO2 = 15 vol%, resulting in C(a-v)O2 = 5 vol%

Deadspace/Tidal Volume Ratio (Vd/Vt)

Vd/Vt ratio normal value: 33%
Vd = deadspace; Vt = tidal volume

Bohr's Equation

Bohr's Equation: Vd/Vt = (PaCO2 - PeCO2) / PaCO2
Example calculation: Vd/Vt = 0.125 or 13%

Alveolar Air Equation (PAO2)

PAO2 = (PB - PH2O)FIO2 - (PaCO2/RQ)
Normal values: PAO2 = 99 mmHg, PB = 760 mmHg, PH2O = 47 mmHg, RQ = 0.8

PAO2 Calculation Example

Given PB = 760 mmHg, PH2O = 47 mmHg, FIO2 = 21%, PaCO2 = 40 mmHg, PAO2 = 100 mmHg

Active Ingredient Concentration

Relationship: mL active/mL total = mg active/mL total

Active Ingredient Example

In a 1% solution, 10 mg is present in 1 cc (mL).

Active Ingredient Calculation Example

In 0.7 mL of 1:200 Isuprel, there are 3.5 mg of active ingredient.

Concentration Calculation of Solutions

Use V1C1 = V2C2 to find concentrations or volumes.

Dilution Calculation Example

To dilute 15 mL of 20% Mucomyst to 15%, add 5 mL of diluent.

Alveolar Ventilation (VA)

VA formula: VA = f(Vt - Vd)
VA measures alveolar ventilation per minute using respiratory rate (f), tidal volume (Vt), and deadspace (Vd).

Ideal Body Weight (IBW) Formula

For men: IBW = 106 + 6 for each inch over 5'
For women: IBW = 100 + 5 for each inch over 5'

Classic Shunt Equation (Qs/Qt)

Qs/Qt formula: Qs/Qt = (CcO2 - CaO2) / (CcO2 - CvO2)

When to Use Classic Shunt Equation

Applicable when FIO2 ≥ 30%.

Modified Shunt Equation (Qs/Qt)

Modified formula: Qs/Qt = (P(A-a)O2 x 0.003) / [(P(A-a)O2 x 0.003) + C(a-v)O2]
P(A-a)O2 = alveolar-arterial oxygen tension gradient.

When to Use Modified Shunt Equation

Relevant when PO2 ≥ 150 mmHg on any FIO2.

Static Compliance (Cst)

Cst formula: Cst = corrected Vt / (Pplat - PEEP)

Cylinder Duration for Gas

Calculation: PSI x tank factor / liter flow, with specific tank factors for different gases.

Cylinder Duration for Liquid

Calculation: 3.44 x liquid weight / liter flow.

Percent Body Humidity Calculation

Formula: Content / 44 mg/L x 100 = % Body Humidity.

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Description

This quiz focuses on calculating the Total Oxygen Content in arterial blood (CaO2) using hemoglobin content, oxygen saturation, and partial pressure of oxygen. Examine the formula and practice your calculation skills with sample values to enhance your understanding of respiratory physiology.