Respiratory System Gas Transport by the Blood Xinping
Respiratory System Gas Transport by the Blood Xinping Yue xyue@lsuhsc. edu Department of Physiology LSUHSC-NO
At Standard Barometric Pressure Dry Atmospheric Inspired Gas Alveolar Gas (P) (PI) (PA) Mixed Expired Gas (PE) Po 2 159. 0 mm. Hg 149. 0 mm. Hg 104. 0 mm. Hg 120. 0 mm. Hg Pco 2 0. 3 mm. Hg 40. 0 mm. Hg 27. 0 mm. Hg PN 2 600. 6 mm. Hg 564. 0 mm. Hg 569. 0 mm. Hg 566. 0 mm. Hg PH 2 O 0 mm. Hg 47. 0 mm. Hg
Gas Transport O 2 = 150 torr CO 2 = 0 torr O 2 = 100 torr CO 2 = 40 torr CO 2 = 45 torr O 2 = 100 torr CO 2 = 40 torr
Transport of O 2 by the blood Ø Physically dissolved • At 37°C, 1 ml of plasma contains 0. 00003 ml O 2/mm Hg PO 2 • Normal arterial blood contains 0. 3 ml O 2/100 ml Ø Chemically combined to hemoglobin • 1 gram of hemoglobin can combine with 1. 34 ml of O 2 when fully saturated • A person with 15 g Hb/100 ml of blood can carry 20. 1 ml O 2/100 ml blood % Hb saturation = O 2 bound to Hb O 2 capacity of Hb x 100%
Hemoglobin, human, adult (heterotetramer, (αβ)2) Heme b group The protein's α and β subunits are in red and blue, and the iron-containing heme groups in green
Oxyhemoglobin Dissociation Curve
Bohr effect
Hemoglobin saturation, % 100 80 60 Pco 2 , p. H temp, BPG 50% 40 20 20 40 60 80 100 120 P 50 Partial pressure of oxygen, mm Hg 140 160
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)
Transport of CO 2 by the blood Ø Physically dissolved (5 -10%) • At 37°C, 1 ml of plasma contains 0. 0006 ml CO 2/mm Hg PCO 2 • Normal arterial blood contains 2. 4 ml CO 2/100 ml Ø Carbamino compounds (5 -10%) Ø Bicarbonate (80 -90%) CO 2 (Gas phase) CO 2 + H 2 O (Dissolved in the aqueous phase) Carbonic Anhydrase H 2 CO 3 H+ + HCO 3 -
Carbamino Compound H H R-N + CO 2 H Terminal amine group R-N + COO- Carbamino compound H+
Carbon Dioxide Dissociation Curve Haldane effect
A Classification of the Causes of Hypoxia Increased FIo 2 helpful? PA o 2 Pao 2 Cao 2 Pvo 2 Cvo 2 Low Low Low Yes Diffusion impairment Norm Low Low Yes Right to left shunts Norm Low Low No V/Q mismatch Norm Low Low Yes Anemic hypoxia Norm Low Low No CO poisoning Norm Low Low Possibly Hypoperfusion hypoxia Norm Low No Histotoxic hypoxia Norm High No Classification Hypoxic hypoxia Low alveolar Po 2
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