Pulmonary Equations

Basic EQUATIONS

The dots are left off of the symbols, but if the units are volume per time you will see a dot over the symbol in most text books

You should know (and be able to rearrange) the following equations:

Alveolar oxygen pressure:  P_AO₂ = P_IO₂ - P_ACO₂/R

Respiratory exchange ratio:  R = VCO₂/VO₂

Inspired oxygen pressure:  P_IO₂ = (P_B - 47) x F_IO₂

Alveolar ventilation: V_A = VCO₂/PaCO₂ x 863

Dead Space (Bohr) equation:  V_D / V_T = (P_ACO₂ - P_ECO₂)/ P_ACO₂

Minute ventilation: V_E = V_A + V_D

Fick principle: VO₂ = CO x (CaO₂ - CvO₂)

Henderson-Hasselbalch equation:  pH = pK’ + log [HCO3-]/0.03 PCO₂

Laminar fluid flow (blood or air): Flow = DP/R = DP x pr⁴/ 8hl

Shunt:      Qs/Qt = (CcO₂ - CaO₂)/CcO₂ - CvO₂)

NORMAL VALUES FOR PULMONARY INSPIRED AND BLOOD GASES DATA

Value	Symbol	Normal Value Sea Level	Normal Value 1600 meters	Units
Barometric Pressure	PB	760	630	mm Hg
Inspired 02 fraction	FI02	0.21	0.21	m102/ml air
Inspired 02 pressure	PI02	149	122	mm Hg
Inspired C02 fraction	FIC02	0.03	0.03	mlC02/ml air
Alveolar C02 pressure	PAC02	40	36	mm Hg
Alveolar 02 pressure	PA02	100	77	mm Hg
Arterial C02 pressure	Pa C02	40	36	mm Hg
Arterial 02 pressure	Pa02	95	72	mm Hg
Arterial saturation	Sata	97	93	%
Arterial pH	pHa	7.40	7.40	pH units
Plasma bicarbonate	HC03-	24	22	mmol /L
Oxygen consumption	V02	250	250	ml02/min
Carbon dioxide production	VC02	200	200	mlC02/min
Respiratory Exchange Ratio	R	0.8	0.8
Diffusing Capacity	DLCO	24	24	ml/min/mm Hg

* Approximate values for adults (70 kg) measured at STPD

NORMAL VALUES FOR PULMONARY DATA (continued)

LUNG VOLUMES AND CAPACITIES	SYMBOL	SEA LEVEL	1600 m	UNITS
Inspiratory capacity	IC	3600	3600	ml BTPS
Expiratory reserve volume	ERV	1200	1200	ml BTPS
Vital capacity	VC	4800	4800	ml BTPS
Residual volume	RV	1200	1200	ml BTPS
Functional residual capacity	FRC	2400	2400	ml BTPS
Total lung capacity	TLC-	6000	6000	ml BTPS
RV/TLC x 100	RV/TLC	20	20	%
VENTILATION
Tidal volume	VT	500	533	ml BTPS
Frequency	f	12	12	br/min
Minute volume^*	VE	6000	6396	ml/min
Dead space	VD	150	150	ml
Alveolar ventilation	VA	4200	4596	ml/min
Maximum voluntary ventilation	MVV	170	190	L/min
Forced expiratory vol. 1n 1 sec	FEV1	4000	4200	ml

* measured by collecting exhaled gas, thus VE