Dry Atmospheric Gas at Standard Barometric Pressure Po2 159.0 torr Pco2 0.3 torr PN2 600.6 torr

Inspired Gas at Standard Barometric Pressure PIo2 149.0 torr PIco2 0.3 torr PIN2 564.0 torr PIH2O 47.0 torr

Alveolar Gas at Standard Barometric Pressure PAo2 104.0 torr PAco2 40.0 torr PAN2 569.0 torr PAH2O 47.0 torr

ALVEOLAR AIR EQUATION 2 PACO2 PAO2 = PIO2 - + F R PAO2 = FIO2 ( PB - PH O) -

Mixed Expired Air at Standard Barometric Pressure PEo2 120.0 torr PEco2 27.0 torr PEN2 566.0 torr PEH2O 47.0 torr

Solubility of O2 in Plasma At 37°C 1 ml of plasma contains 0.00003 ml O2 / torr PO2

O2 Carrying Capacity of Hemoglobin 1 gram of hemoglobin can combine with 1.34ml of oxygen when fully saturated

O2 bound to Hb % Hb saturation = x 100% O2 capacity of Hb

Hemoglobin saturation, % 100 80  Pco2 ,  pH  temp,  BPG Pco2 ,  pH temp,  BPG 60 Hemoglobin saturation, % 50% 40 20 Figure 2-24 Maximal expiratory flow-volume curves representative of obstructive and restrictive diseases 20 40 60 80 100 120 140 160 P50 Partial pressure of oxygen, torr

CYANOSIS Occurs when more than 5 grams of hemoglobin/100 ml of arterial blood are in the “deoxy” state Absence of cyanosis does not rule out hypoxemia (anemia) Presence of cyanosis does not always indicate hypoxemia (polycythemia)

At 37°C 1 ml of plasma contains 0.03 mmol of CO2 / torr Pco2 Solubility of CO2 in Plasma At 37°C 1 ml of plasma contains 0.03 mmol of CO2 / torr Pco2 Or 0.0006 ml of CO2 / torr Pco2

Carbamino Compound R - N + CO2 R - N + H+ H COO- Terminal amine group

Transport of CO2 by the Blood (Gas phase) Carbonic Anhydrase _ CO2 + H2O H2CO3 H+ + HCO3 (Dissolved in the aqueous phase)

TISSUE PLASMA ERYTHROCYTE CO2 CO2 dissolved CO2 H2O H2O + CO2 CO2 Carbonic anhydrase dissolved H2CO3 Cl- Cl- CAPILLARY WALL HCO3- HCO3- + H+ H+ + HbO2 O2 O2 O2 O2 + HHb HHb+CO2 Carbamino compounds

ALVEOLUS PLASMA ERYTHROCYTE CO2 CO2 dissolved CO2 H2O H2O + CO2 CO2 Carbonic anhydrase dissolved H2CO3 Cl- Cl- CAPILLARY WALL HCO3- HCO3- + H+ H+ + HbO2 O2 O2 O2 O2 + HHb HHb+CO2 Carbamino compounds

A Classification of the Causes of Hypoxia Increased FIo2 helpful? PAo2 Pao2 Cao2 Pvo2 Cvo2 Classification Hypoxic hypoxia Low alveolar Po2 Diffusion impairment Right to left shunts V/Q mismatch Anemic hypoxia CO poisoning Hypoperfusion hypoxia Histotoxic hypoxia Low Norm Low Norm Low Norm Low High Low High Yes No Possibly