# All Respiratory-calculators Formulas List

## Total Lung Capacity (TLC), Closing Capacity (CC) Volume

#### Formula:

TLC = IRV + TV + ERV + RV
CC = CV + RV
CC / TLC(%) = 100 * CC / TLC

Where
,
TLC=Total lung capacity
CC=Closing capacity
IRV=Inspiratory Reserve Volume (Liters)
TV=Tidal Volume (Liters)
ERV=Expiratory Reserve Volum (Liters)
RV=Residual Volume (Liters)
CV=Closing Volume (Liters)

## Cerebral Blood Flow (CBF)

#### Formula:

Cerebral Blood Flow (CBF)=(MAP - ICP)/CVR
MAP(Mean art press)= DBP+[1/3(SBP-DBP)]

Where,
ICP=intracranial press
CVR = Cerebral Vascular Resistance (units are dynes = mmHg/mL/min)
Within the limits of systemic MAP, the human brain alters CVR to keep CBF constant.

## Average Blood Sugar (Glucose) Level

#### Formula:

mmol/L = ( HbA1c * 1.98 ) - 4.29

Where,

HbA1c - Glycosylated Hemoglobin
mmol/L - Avg. plasma blood glucose

## Red Blood Cell Distribution Width (RDW)

#### Formula:

RDW = (Std Dev of MCV*100/MCV)

## Respiratory Acidosis Acute

#### Formula:

(HCO3 (mg/dL)=(24+PaCO2 (mmHg)-Baseline PaCO2 /10))

## Fractional Excretion of Sodium (FENa)

#### Formula:

Fractional Excretion of Na ( FENa) in %=[ (urine Na) / (serum Na) ] x 100 / [ (urine Cr) / (serum Cr) ]

## Arterial Oxygen Content (CaO2)

#### Formula:

Metabolic Acidosis Compensation: Winters Formula
Arterial oxygen content =(Hgb x 1.36 x SaO2) + (0.0031 x PaO2)

where,
SaO2 = % of hemoglobin saturated with oxygen
(Normal range: 93-100%)
Hgb = hemoglobin
Normal range(Adults): Male: 13-18 g/dl Female: 12-16 g/dl
PaO2= Arterial oxygen partial pressure
(Normal range: 80-100)
CaO2: Directly reflects the total number of oxygen molecules in arterial blood (both bound and unbound to hemoglobin)

## Revised Trauma Score (RTS)

#### Formula:

RTS = (0.9368 * GCS Value) + (0.7326 * SBP Value) + (0.2908 * RR Value)

#### Where,

RTS - Revised Trauma Score
GCS - Glasgow Coma Scale
SBP - Systolic Blood Pressure
RR - Respiratory Rate

## Closing Capacity (CC) Volume of Alveoli Collapse

#### Formula:

CC = CV + RV

Where,
CC=Closing capacity
RV=Residual Volume (Liters)
CV=Closing Volume (Liters)

## Total Body Water (TBW) Deficit

#### Formula:

Body Water Deficit (in liters) = ( 0.6 * Wt * [(Na/140) - 1] )

Where,
Wt = current weight in kg
Na = measured serum Na in mmol/L
(Assumes Total Body Water is 60% of current body weight; may be less in female or cachectic patients)

## VO2 Max - Maximal Oxygen Consumption

#### Formula:

VO2 Max = C.O*(13*Hgb)*(SaO2-SvO2)

Where,
VO2 Max = Maximum oxygen consumption
C.O = Cardiac Output
HGB = Hemoglobin
SaO2 = Oxygen saturation(arterial blood)
SvO2 = Oxygen saturation(mixed venous hemoglobin)

## Partial Pressure of Inspired Oxygen (O2) at Sea Level

#### Formula:

CaO2= (Hgb * 1.36 * SaO2 / 100) + PaO2 * 0.0031

## Total Body Water ( TBW )

#### Formula:

Desired total Body Water (TBW) in L= (Measured serum Na x 0.6 x weight) / Normal serum Na
where,
Measured serum Na = Measured amount of sodium in mEq/L or mmol/L.
Normal serum na = Normal amount of sodium in mEq/L or mmol/L.

## Pulmonary Vascular Resistance Index

#### Formula:

PVRI = (79.92 * (MPAP - PCWP)) / CI

Where,

PVRI = Pulmonary Vascular Resistance Index
MPAP = Mean Pulmonary Art Pressure
PCWP = Pulmonary Capillary Wedge Pressure
CI = Cardiac Index

## Ankle Brachial Pressure Index

#### Formula:

Ankle Brachial Index (ABI) = Ankle Systolic Pressure / Brachial Systolic Pressure

## Pulmonary Shunt Calculation

#### Formula:

Qs/Qt(Fraction) = ( C - A ) / ( C - V )
Qs/Qt(%)= (( C - A ) / ( C - V )) × 100

Where,

P = Pulmonary shunt ratio
C = Oxygen content in pulmonary end capillary
A = Oxygen content in arterial
V = Oxygen content in mixed venous blood

## Peak Flow Meter | PEF

#### Formula:

PEF (Female) = e((0.376 x ln(Age)) - (0.012 x Age) - (58.8 / Height) + 5.63)
PEF (Male) = e((0.544 x ln(Age)) - (0.0151 x Age) - (74.7 / Height) + 5.48)