Water Vapor Pressure @ $37{}^{\circ }C=47\text{mmHg}$$37\ ^{\circ}C = 47\ \text{mmHg}$

$1\text{mmHg}=1\text{torr}$$1\ \text{mmHg} = 1\ \text{torr}$

• mmHG is used in air

• torr is used in fluid

$pK=6.10$$pK = 6.10$

• normal numan value

$\alpha =0.0301$$\alpha = 0.0301$

• solubility coefficient for $C{O}_2$$CO_2$

${\text{O}}_2\text{ capacity}=\left(1.34\frac{{\text{mL O}}_2}{\text{g Hgb}}\right)\cdot \left(14\frac{\text{g Hgb}}{100\text{mL blood}}\right)$$\text{O}_2 \text{ capacity} = \left(1.34 \, \frac{\text{mL O}_2}{\text{g Hgb}}\right) \cdot \left(14 \, \frac{\text{g Hgb}}{100 \, \text{mL blood}}\right)$

$O_2$$O_2$ Content = ${\text{HgbO}}_2$$\text{HgbO}_2$ + dissolved $O_2$$O_2$

• ${\text{HgbO}}_2$$\text{HgbO}_2$ is also known as $O_2$$O_2$ capacity

$F_{I{O}_2}$$F_{IO_2}$ or $F_{O_2}$$F_{O_2}$ $=0.2095$$=0.2095$

$O_2$$O_2$ Solubility Coefficient $=\frac{0.00304mL{O}_2}{100mLblood\cdot torr}$$= \frac{0.00304\ mL\ O_2}{100\ mL\ blood\ \cdot torr}$

$\text{vol \%}=\frac{mL{O}_2}{100\text{mL blood}}$$\text{vol\ \%} = \frac{mL\ O_2}{100\ \text{mL blood}}$

Boyle’s Law : At constant temperature, pressure and volume are inversely related

• $P_1$$P_1$ = initial pressure

• $V_1$$V_1$ = initial volume

• $P_2$$P_2$ = final pressure

• $V_2$$V_2$ = final volume

Ideal Gas Law : Relates state variables of an ideal gas

• $P$$P$ = pressure

• $V$$V$ = volume

• $n$$n$ = moles of gas

• $R$$R$ = universal gas constant

• $T$$T$ = absolute temperature

Partial Pressure of a Gas : Fractional concentration times barometric pressure

• $P_{gas}$$P_{gas}$ = partial pressure of the gas

• $F_{gas}$$F_{gas}$ = fractional concentration of the gas

• $P_b$$P_b$ = barometric pressure

Inspired Partial Pressure of O₂ : Inspired O₂ adjusted for water vapor

• $P_{I{O}_2}$$P_{I O_2}$ = inspired O₂ partial pressure

• $P_b$$P_b$ = barometric pressure

• $P_{H_{2}O}$$P_{H_2O}$ = water vapor pressure

• $F_{O_2}$$F_{O_2}$ = fractional concentration of O₂ in inspired air

Alveolar Gas Equation ( O₂ ) : Determines alveolar O₂ partial pressure

• $P_{A{O}_2}$$P_{A O_2}$ = alveolar O₂ partial pressure

• $P_b$$P_b$ = barometric pressure

• $P_{H_{2}O}$$P_{H_2O}$ = water vapor pressure

• $F_{I{O}_2}$$F_{I O_2}$ = inspired O₂ fraction

• $P_{AC{O}_2}$$P_{A C O_2}$ = alveolar CO₂ partial pressure

• $R$$R$ = respiratory exchange ratio

Alveolar CO₂ : Relates alveolar CO₂ pressure to production and ventilation

• $P_{AC{O}_2}$$P_{A C O_2}$ = alveolar CO₂ partial pressure

• ${\dot{V}}_{C{O}_2}$$\dot{V}_{C O_2}$ = CO₂ production rate

• $P_b$$P_b$ = barometric pressure

• $P_{H_{2}O}$$P_{H_2O}$ = water vapor pressure

• ${\dot{V}}_A$$\dot{V}_A$ = alveolar ventilation

Transpulmonary Pressure : Difference between alveolar and pleural pressure

• $P_L$$P_L$ = transpulmonary pressure

• $P_{Alveolar}$$P_{Alveolar}$ = alveolar pressure

• $P_{pleural}$$P_{pleural}$ = pleural pressure

Chest Wall Transmural Pressure : Difference across the chest wall

• $P_w$$P_w$ = chest wall transmural pressure

• $P_{pl}$$P_{pl}$ = pleural pressure

• $P_b$$P_{b}$ = body surface pressure

Respiratory System Pressure : Sum of transpulmonary and chest wall pressures

• $P_{rs}$$P_{rs}$ = respiratory system pressure

• $P_L$$P_L$ = transpulmonary pressure

• $P_w$$P_w$ = chest wall transmural pressure

Laplace’s Law : Relates pressure in a sphere to surface tension and radius

• $P_s$$P_s$ = pressure

• $T$$T$ = surface tension

• $r$$r$ = radius

Pressure-Flow Relationship : Pressure difference equals flow times airway resistance

• $\mathrm{\Delta }P$$\Delta P$ = pressure difference

• $\dot{V}$$\dot{V}$ = flow

• $R_{aw}$$R_{aw}$ = airway resistance

Compliance : Change in volume per unit change in pressure

• $C_L$$C_L$ = compliance

• $\mathrm{\Delta }V$$\Delta V$ = change in volume

• $\mathrm{\Delta }P$$\Delta P$ = change in pressure

Airway Resistance : Via Poiseuille’s law

• $R$$R$ = resistance

• $\mathrm{\Delta }P$$\Delta P$ = pressure difference

• $\dot{V}$$\dot{V}$ = flow rate

• $\eta$$\eta$ = viscosity

• $L$$L$ = length

• $r$$r$ = radius

Reynolds Number : Dimensionless number indicating flow regime

• $R_e$$R_e$ = Reynolds number

• $r$$r$ = radius

• $v$$v$ = velocity

• $d$$d$ = density

• $\eta$$\eta$ = viscosity

Poiseuille’s Law for Flow : Flow in a tube depends on pressure and dimensions

• $\dot{V}$$\dot{V}$ = volume flow rate

• $P$$P$ = driving pressure

• $r$$r$ = radius

• $\eta$$\eta$ = viscosity

• $L$$L$ = length

Minute Ventilation : Tidal volume times frequency

• ${\dot{V}}_E$$\dot{V}_E$ = minute ventilation

• $V_T$$V_T$ = tidal volume

• $f$$f$ = breathing frequency

Total Ventilation : Sum of dead space and alveolar ventilation

• ${\dot{V}}_E$$\dot{V}_E$ = minute ventilation

• ${\dot{V}}_D$$\dot{V}_D$ = dead space ventilation

• ${\dot{V}}_A$$\dot{V}_A$ = alveolar ventilation

Tidal Volume Components : Tidal volume = dead space volume + alveolar volume

• $V_T$$V_T$ = tidal volume

• $V_D$$V_D$ = dead space volume

• $V_A$$V_A$ = alveolar volume

Dead Space Ventilation Rate : Fraction of tidal volume that is dead space times total ventilation

• ${\dot{V}}_D$$\dot{V}_D$ = dead space ventilation rate

• $V_D$$V_D$ = dead space volume

• $V_T$$V_T$ = tidal volume

• ${\dot{V}}_E$$\dot{V}_E$ = minute ventilation

Respiratory Quotient : Ratio of CO₂ produced to O₂ consumed

• $R$$R$ = respiratory quotient

• ${\dot{V}}_{C{O}_2}$$\dot{V}_{C O_2}$ = CO₂ production rate

• ${\dot{V}}_{O_2}$$\dot{V}_{O_2}$ = O₂ consumption rate

Alveolar CO₂ Elimination : Depends on alveolar ventilation and alveolar CO₂ fraction

• ${\dot{V}}_{C{O}_2}$$\dot{V}_{C O_2}$ = CO₂ elimination rate

• ${\dot{V}}_A$$\dot{V}_A$ = alveolar ventilation

• $F_{AC{O}_2}$$F_{A C O_2}$ = alveolar fraction of CO₂

O₂ Uptake by Diffusion : O₂ flux across a membrane

• ${\dot{V}}_{O_2}$$\dot{V}_{O_2}$ = O₂ uptake rate

• $A$$A$ = area

• $T$$T$ = thickness

• $D$$D$ = diffusion coefficient

• $P_{out:O_2}$$P_{out:O_2}$ = partial pressure outside ( alveolar )

• $P_{in:O_2}$$P_{in:O_2}$ = partial pressure inside ( blood )

Mixed Expired CO₂ : CO₂ elimination from difference in inspired/expired fractions

• ${\dot{V}}_{C{O}_2}$$\dot{V}_{C O_2}$ = CO₂ elimination rate

• ${\dot{V}}_E$$\dot{V}_E$ = minute ventilation

• $F_{EC{O}_2}$$F_{E C O_2}$ = expired fraction CO₂

• $F_{IC{O}_2}$$F_{I C O_2}$ = inspired fraction CO₂

Mixed Expired O₂ : O₂ uptake from differences in inspired and expired O₂ fractions

• ${\dot{V}}_{O_2}$$\dot{V}_{O_2}$ = O₂ uptake rate

• ${\dot{V}}_E$$\dot{V}_E$ = minute ventilation

• $F_{I{O}_2}$$F_{I O_2}$ = inspired O₂ fraction

• $F_{E{O}_2}$$F_{E O_2}$ = expired O₂ fraction

Work : Pressure times change in volume

• $W$$W$ = work

• $P$$P$ = pressure

• $\mathrm{\Delta }V$$\Delta V$ = change in volume

Starling Equation : Fluid movement across capillaries

• $\text{Flux}$$\text{Flux}$ = fluid flux

• $K_{fc}$$K_{fc}$ = filtration coefficient

• $P_{jv}$$P_{jv}$ = capillary hydrostatic pressure

• $P_{is}$$P_{is}$ = interstitial hydrostatic pressure

• ${\sigma }_d$$\sigma_d$ = reflection coefficient

• ${\pi }_{jv}$$\pi_{jv}$ = capillary oncotic pressure

• ${\pi }_{is}$$\pi_{is}$ = interstitial oncotic pressure

Henderson–Hasselbalch Equation : Relates pH to bicarbonate and CO₂

• $pH$$pH$ = acidity measure

• $pK$$pK$ = dissociation constant

• $[HC{O}_3^{-}]$$[ HCO_3^- ]$ = bicarbonate concentration

• $\alpha$$\alpha$ = CO₂ solubility coefficient

• $P_{C{O}_2}$$P_{C O_2}$ = partial pressure of CO₂

Dissolved Gas Concentration : Concentration = solubility * partial pressure

• $[gas]$$[ gas ]$ = dissolved gas concentration

• $\alpha$$\alpha$ = solubility

• $P_{gas}$$P_{gas}$ = partial pressure of the gas

Bicarbonate Buffer System : Equilibria between CO₂ , carbonic acid , and bicarbonate

• $H_{2}O$$H_2O$ = water

• $C{O}_2$$C O_2$ = carbon dioxide

• $H_{2}C{O}_3$$H_2C O_3$ = carbonic acid

• $H^{+}$$H^+$ = hydrogen ion

• $HC{O}_3^{-}$$HCO_3^-$ = bicarbonate ion

Cardiac Output : Heart rate times stroke volume

• ${\dot{Q}}_t$$\dot{Q}_t$ = cardiac output

• $f_{HR}$$f_{HR}$ = heart rate

• $SV$$SV$ = stroke volume

Stroke Volume : Difference between end-diastolic and end-systolic volumes

• $SV$$SV$ = stroke volume

• $EDV$$EDV$ = end-diastolic volume

• $ESV$$ESV$ = end-systolic volume

Mean Arterial Pressure ( General ) : Output times resistance

• $\overline{P_a}$$\overline{P_a}$ = mean arterial pressure

• $f_H$$f_H$ = heart rate

• $SV$$SV$ = stroke volume

• $TPR$$TPR$ = total peripheral resistance

Mean Arterial Pressure ( Approx 1 ) : Weighted mean

• $\overline{P_a}$$\overline{P_a}$ = mean arterial pressure

• $DBP$$DBP$ = diastolic blood pressure

• $SBP$$SBP$ = systolic blood pressure

Mean Arterial Pressure ( Approx 2 ) : Simple averaging method

• $\overline{P_a}$$\overline{P_a}$ = mean arterial pressure

• $DBP$$DBP$ = diastolic blood pressure

• $SBP$$SBP$ = systolic blood pressure

O₂ Delivery : Cardiac output times arterial O₂ content

• $\text{Delivered }{O}_2$$\text{Delivered } O_2$ = O₂ delivery to tissues

• ${\dot{Q}}_t$$\dot{Q}_t$ = cardiac output

• $C_{a{O}_2}$$C_{a O_2}$ = arterial O₂ content

O₂ Consumption : Cardiac output times arterial-venous O₂ difference

• ${\dot{V}}_{O_2}$$\dot{V}_{O_2}$ = O₂ consumption rate

• ${\dot{Q}}_t$$\dot{Q}_t$ = cardiac output

• $C_{a{O}_2}$$C_{a O_2}$ = arterial O₂ content

• $C_{v{O}_2}$$C_{v O_2}$ = venous O₂ content