MUST KNOW Physiology SEE/NCE FORMULAS

Question 1

Dynamic compliance =

Answer 1

Cdyn = Tidal volume / PIP - PEEP

Question 2

Static compliance =

Answer 2

Cstat = Tidal Volume / Plateau pressure - PEEP

Question 3

Vd / Vt RATIO (dead space to tidal volume ratio)

Answer 3

Vd / Vt x 100
Vd: dead space
Vt: Tidal volume

Question 4

Serum Osmolality=

Answer 4

2 (Na+) + (BUN/2.8) + (Glucose/18)

Question 5

Cerebral Perfusion Pressure (CPP) =

Answer 5

MAP - ICP

Question 6

Anion GAP =

Answer 6

Na - (Cl + HCO3)

Question 7

CO =

Answer 7

CO = HR x SV

Question 8

Alveolar Gas Equation and constant to know: (PAO2)

Answer 8

PAO2 = FiO2 x (Patm - PH2O) - (PaCO2 / RQ)

FiO2: amount of FiO2/100
Patm: if not given to you is 760mmHg
PH2O : 47 mmHg
PaCO2:  Partial pressure of CO2 (will be given)
RQ: (Respiratory quotient):  0.8

Question 9

A-a Gradient is

Answer 9

A-a = PAO2 - PaO2

You will need to use alveolar gas equation first to calculate it (DONT FORGET TO minus PaO2)

Question 10

DO2 = Oxygen delivery =

Answer 10

DO2= CO x CaO2

Question 11

CaO2 = Oxygen Carrying Capacity =

Answer 11

CaO2 = (1.34 x Hgb x SaO2/100) + (PaO2 x 0.003)

Question 12

SV = Stroke Volume =

Answer 12

SV = EDV - ESV

Question 13

EF = Ejection Fraction =

Answer 13

EF = SV/EDV x 100 (if question asked for percentage )

Question 14

MAP = Mean Arterial Pressure =

Answer 14

MAP = SBP + 2 (DBP) / 3

Question 15

PP = Pulse Pressure =

Answer 15

PP = SBP - DBP

Question 16

SVR =

Answer 16

SVR = MAP - CVP/ CO x 80

Question 17

Given an inspiratory time of 1.2 seconds and an expiratory time of 3 seconds, calculate
the I:E ratio and the respiratory rate.

Answer 17

1. First calculate Total Cycle Time (TCT)
   TCT= Ti(insp) + Te (exp)
   = 1.2 + 3 = 4.2 seconds
   I: E ratio is Te/Ti = (bigger number on top)
   3/1.2 = 2.5 so the I:E ratio is 1: 2.5
2. f = 60/ TCT
   f = 60/ 4.2 = 14.24 ~ rate of 14

Question 18

Given an inspiratory time of 0.8 seconds and an expiratory time if 1.5, calculate the I:E ratio and the rate

Answer 18

TCT = Ti + Te = 0.8 + 1.5 = 2.3 seconds
f = 60/TCT = 60/2.3 sec = 26 (rate of 26)
I:E ratio is 
1.5 / 0.8 = 1.875
1: 1.875  so 1:1.9

Question 19

Given an expiratory time of 1.75 seconds and an inspiratory time of 1 second, calculate
the I:E ratio and the rate.

Answer 19

TCT = 1 + 1.75 = 2.75 seconds
I: E ratio is 1.75/1 = 1: 1.75
Respiratory Rate
f = 60/ TCT = 60/2.75 = 21.8 ~ 22 rate

Question 20

Given a f of 40/min and an I:E ratio of 1:2, calculate the inspiratory and expiratory time.

Answer 20

TCT = Ti + Te (both unknown)
f = 60/TCT 
40= 60/TCT
TCT = 60/40 = 1.5 seconds
Ti = TCT/I+E
Ti = 1.5 / 1+2 = 1.5 / 3 = 0.5
TCT = Ti + Te
1.5 sec = 0.5sec + Te
1.5-0.5 = Te
Te= 1

Question 21

The doctor orders a f of 50/minute and an I:E ration of 1:1.5. Calculate the Inspiratory and expiratory time.

Answer 21

Inspiratory time is 0.48

Expiratory time is 0.7

Question 22

PVR =

Answer 22

Mean PAP - PAOP/ CO x 80

PAOP or PCWP

Question 23

MAP other formula is

Answer 23

MAP = CO x SVR/80 x CVP

Question 24

During intraoperative fluoroscopy, the patient receives 32 mR at a distance of 1 foot from the fluoroscopy tube. The maximum radiation dose possible to the anesthesia provider, standing at a distance of 4 feet from the fluoroscopy tube is: (Enter numerical answer in box below. Click ‘Next’ when completed.)

Answer 24

(I1) (D1)^2 = (I2) (D2)^2
I = intensity, D = distance
(32 mR)(1 ft)2 = (I2)(4 ft)2; I2 = 2 mR