Mathematical Formulas Flashcards by Jo'esha Tate

What is the cylinder tank factors for an E and a H tank?

E is 0.28, H is 3.14

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What is the formula to calculate duration of flow?

PSI X CF/Lpm

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What is Heliox used for and what are the factors for a 70/30 mix and a 80/20 mix?

Heliox is used for upper airway obstruction and asthma exacerbation.
70/30=1.6 80/20 = 1.8

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What is the formula to estimate the suction catheter size for an adult patient?

(ETT SIZE X 2 - 2)

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What is the formula used to estimate an ETT size for children?

ID = age +16/4

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What is the formula for the Clark’s rule? hint: estimated child dose

Child’s weight in lbs x adult dose/150

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What is the temperature conversion for F to C?

C = f-32/1.8

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What is the temperature conversion for C to F?

F= (C x 1.8) +32

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What is RAW used for? What is the normal value and the formula used to determine it?

RAW is used to estimate the level of PSV needed to overcome imposed WOB, 0.5-2.5
formula: RAW = PIP-pPlat/Flow L/s

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What does Cstat measure? What is the formula used to determine it?

Measures the compliance of the lungs and the thorax, Cs= Vte/Pplat-PEEP

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What does Cdyn measure? What is the formula used to determine it?

Measures impedance to ventilation by movement of gas through airways., Cdyn=Vte/PIP-PEEP

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If a pt’s condition rapidly deteriorates but there is no change in static or dynamic compliance, suspect a ___.

P.E.

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Higher compliance = lower ___ = easier to ventilate = less side effects of CMV.

PIP’s

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Lower compliance = _______ _______ = less compliance = higher ventilating pressures

stiffer lungs

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Increased RAW = ______ PIP & _____ flows.

increased, decreased

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Cdyn and Cstat worsening over time = ____ problem.

LUNG

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Cdyn worsening but Cstat not changing = ______ problem.

AIRWAY

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What is the formula for RSBI? What does it stand for and what values indicates weaning?

RR/VT, rapid shallow breathing index, <105.

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What is the formula used to calculate alveolar minute ventilation?

VA = ( Vt-Vd) x RR

What is the Bohr equation(VD/VT)? What does it represent?

VD/VT= PaCO2-PECO2/PaCO2, Portion of VT not taking place in gas exchange (wasted ventilation)

What is the range for a normal VD/VT ratio?

0.2-0.4 (20-40%)

What is the formula for delivery of oxygen(DO2)?

DO2= QT X CaO2

For adequate O2 diffusion, blood contact needs to be at least ____s.

0.75

O2 delivery is _____ related to cardiac output and total O2 content.

directly

List some conditions that reduces oxygen delivery to the tissues.

shock, ischemia, hypixemia,etc

What is a normal total O2 content? What is the formula used to determine it?

17-21 vol% ml/dl, CaO2= (Hgb x sao2 x 1.34) + (pao2 x 0.003)

List the values for the following CaO2 indexes. Mild, moderate, and severe hypoxemia.

mild: 15-16% vol mod: 12-14% vol sev: < 12 vol%

What is normal mixed venous content(CVO2)? What does this represnet?

12-16 vol%, represents the blood that is returning to the lungs.

What is the normal value for the arteriovenous content(C(a-v)O2)? What does this measure?

3.5-5.0 vol%, measures O2 consumption(VO2) by the tissues.

A decreased CO = ______ C(a-v)O2.

increased

A increased CO = _____ C(a-v)O2.

decreased

CO = ____ x _____

HR , SV

What are the methods used to determine cardiac output?

PAC (thermodilution or dye) or Fick equation method.

What is the formula for the Fick equation that is used to determine CO?

QT = VO2/ C(a-v)O2 x10

What is normal MAP, and what is the formula used to determine it?

80-100 mmHg, MAP= SBP + 2(DBP)/3

Under normal conditions CO2 is directly related to ____ and indirectly related to _____.

VO2, C(a-v)O2

What is the formula used to determine VO2?

QT X C(a-v)O2 x 10

What is normal A-a gradient on RA? On 100%?

RA: 5 to 10 mmHg, 25-65 mmHg

What A-a gradient signifies the presence of a VQ mismatch or a shunt?

VQ mismatch= <300 Shunt= > 300 tip: the higher the A-a gradient, the higher the shunt

What is the formula used to determine the PAO2?

PAO2= (PB-PH2O)FiO2 - (PaCO2/0.8)

What is the a/A ratio?

The ratio of blood transported from the alveoli into the blood.

What a/A ratio value is normal, represents a VQ mismatch or shunting?

Normal: > 75% VQ mismatch: 35-75% Shunt: <35%

What is the formula used to calculate the degree of a shunt?

P(A-a)O2 X 0.003/ C(a-v)O2 + (P(A-a)O2 x 0.003)

What shunt value is normal, indicates mild, mod, or severe shunting?

normal: <10% mild: 10-20% mod: 20-30% sev: >30%

How is pulse pressure calculated?

SBP - DBP