Formulas Flashcards
What is the formula for converting a gas % to mm Hg?
% x 7 = mm Hg
FEV1 x ___ = MVV
FEV1 x 35 = MVV
The most IMPORTANT equation on the exam:
What is the alveolar air equation?
What do you need to calculate it?
Pick one:
The correct answer (can/can’t) be higher than the result of the equation.
(Fio2 x 7) - PaCO2
To calculate it, you will need the FiO2 and the PaCO2 from an ABG
The correct answer CAN’T be higher than the result of the equation.
*page D-16
What is the cardiac output equation?
Qt =
VO2
____
(a - v) x 10
*page D-18
What is the arterial oxygen content (CaO2) equation?
What do you need to calculate it?
Is it similar to the mixed venous oxygen content (CvO2) equation? What is the difference?
CaO2 = (Hb x 1.34 x SaO2)
You will need the pt’s Hb and SaO2
CaO2 and CvO2 equations are similar. The difference is a CvO2 requires a SvO2 in place of the SaO2.
*page D-17
Note: Hb can be obtained from a CBC and SaO2 from an ABG
What is the arterial-venous oxygen content difference calculation?
CaO2 - CvO2
*page D-17
How do you calculate shunt percentage?
Start with 5%. Add 5% for every 100 torr in the A-a gradient.
Note: NEVER pick an answer above your calculated result. Pick the closest answer to yours that is the same or lower.
*page D-19
What is the formula to calculate deadspace to tidal volume ratio?
What values do you need to calculate it?
PaCO2 - PeCO2
_____________
PaCO2
You will need PaCO2 from an ABG, and PETCO2 from capnography
*page D-21
How do you estimate anatomic deadspace when given the patient’s body weight?
Anatomic deadspace is typically 1ml per lb of body weight.
*page E-22
How do you calculate MHR (maximum heart rate)?
220 - age
*page E-8
How do you calculate MAP (mean arterial pressure)?
(diastolic x 2) + systolic
__________________
3
*page E-28
