Equations Flashcards
What is the formula for cardiac output (CO)?
CO = heart rate * stroke volume
What is the formula for systemic vascular resistance (SVR)?
SVR = (MAP - CVP) / CO
What is the formula for pulmonary vascular resistance (PVR)?
PVR = (MPAP - PCWP) / CO
What is the formula for oxygen delivery (DO2)?
DO2 = CO * arterial oxygen content (CaO2)
What is the formula for oxygen consumption (VO2)?
VO2 = CO * (CaO2 - CvO2)
What is the formula for alveolar-arterial oxygen gradient (A-a gradient)?
A-a gradient = (PAO2 - PaO2)
What is the formula for shunt fraction?
Shunt fraction = (Qs/Qt) * 100%
Qs/Qt = (CcO2 - CaO2) / (CcO2 - CvO2)
CcO2 can be assumed as per oxygen varying capacity equation at 100%Spo2 and the PaO2 can be derived from the alveolar gas equation
What is the formula for oxygen extraction ratio (OER)?
OER = (CaO2 - CvO2) / CaO2
What is the formula for Fick principle?
VO2 = CO * (CaO2 - CvO2)
What is the formula for mean pulmonary artery pressure (MPAP)?
MPAP = (systolic PAP + 2 * diastolic PAP) / 3
What is the formula for cardiac index (CI)?
CI = CO / BSA
What is the formula for oxygen content in arterial blood (CaO2)?
CaO2 = (Hb x 1.34 x SaO2) + (PaO2 x 0.0031)
What is the formula for alveolar oxygen tension (PAO2)?
PAO2 = (PB - PH2O) x FiO2 - (PaCO2 / R)
Henderson hasselbalch equation
Considers relationship of buffer system to pH
pH = pKa + Log (base/acid)
Strong ion difference
SID = (Na + K + Ca + Mg) - (Cl + Lactate)
Plasma H+ concentration is related to Strong Ion Difference, partial pressure of CO2 and total weak acid concentration
So sodium and chloride are key components to change H+ via SID via change in dissociation of water to H+
E.g. hyperchloraemic acidosis in patients given high volumes of saline 0.9%
