Transport of Respiratory Gases II - PDF

Transport of respiratory gases II Dr. Ghada Elgarawany Assistant professor of Medical Physiology www.gmu.ac.ae COLLEGE OF MEDICINE  List the mechanisms of carbon dioxide transport  Identify chloride shift phenomenon.  Describe CO2 dissociation Curve  Describe Haldane effect.  Differentiate betw...

Transport of respiratory gases II Dr. Ghada Elgarawany Assistant professor of Medical Physiology www.gmu.ac.ae COLLEGE OF MEDICINE  List the mechanisms of carbon dioxide transport  Identify chloride shift phenomenon.  Describe CO2 dissociation Curve  Describe Haldane effect.  Differentiate between Bohr effect and Haldane effect. Carbon dioxide transport by the blood CO2 content in the arterial blood = 48ml/dl Free in Physical solution (3ml/dl) In plasma and RBCs in Chemical Combination (45ml/dl) Carbamino Compound (3ml/dl) In RBCs : Carb-Hb In Plasma : Carbamino protein Bicarbonate (42ml/dl) In RBCs : KHCO3 In Plasma : NaHCO3 Carbon dioxide transport by the blood Tidal CO2 Definition: Under normal resting conditions, an average of 4 ml of CO 2 are transported from the tissues to the lungs in each 100 ml of blood. Buffering of tidal CO2 1. 0.4ml (10% of tidal CO2): dissolve in physical solution → decrease PH from 7.4 to 7.34. 2. 1ml (25% of tidal CO2): change to carbamino compound. deoxy Hb + CO2 = reduced Hb. 3. 2.6ml (65% of tidal CO2): are buffered by Hb with production of HCO3- (Cl- shift phenomenon. Carbon dioxide transport by the blood Cl- shift phenomenon At the tissues  Upon entering the red blood cell, CO2 is rapidly hydrated to H2CO3 by carbonic anhydrase.  H2CO3 is in equilibrium with H+ and its conjugate base, HCO3 −.  H+ can interact with deoxyhemoglobin to form reduced Hb, whereas HCO3 − can be transported outside of the cell via anion exchanger 1 (AE1 or Band 3) with Cl-.  In effect, for each CO2 molecule that enters the red cell, there is an additional HCO3 − leaves the RBC and Cl− enters RBC.  Because of this chloride shift, the Cl− content of the red cells in venous blood is significantly greater than that in arterial blood. Carbon dioxide transport by the blood At the Lung  An opposite process occurs.  HCO3- passes from plasma to RBCs and Clmoves out of the RBCs into the plasma.  Carbonic acid dissociates into H2O and CO2  CO2 diffuses to the alveoli to go outside with expiration. CO2 dissociation Curve Tissues From the curve: the more the CO2 tension , The more the content. At the lung:  PCO2 = 40mmHg → CO2 content = 48ml/dl. At the tissues:  PCO2 = 46mmHg → CO2 content = 52ml/dl. Lung Definition: It shows the relationship between the total CO2 content of blood and CO2 tension (PCO2) PCO2 CO2 dissociation Curve HaLdane effect At the Lung: Binding O2 with the Hb → displace (release) CO2 from the blood to the alveoli. At the tissues (point A):  PO2 = 40mmHg  PCO2 = 46mmHg → CO2 content = 52ml/dl. At the lung (point B):  PO2 = 100mmHg  PCO2 = 40mmHg → CO2 content = 48ml/dl. Without PO2 effect CO2 content will be reduced from 52 ml to 50 ml/dl. (only 2 ml loss of CO2 ) But On Entering the lung, PO2 rise → shift of CO2 dissociation curve down → additional 2ml loss of CO2 to become 48ml/dl. What is Bohr effect Increase CO2 and H+ → Shift of O2 dissociation curve to the right → Release of O2 to the Body tissue Which is more important, Haldane or Bohr effect?? Haldane effect Hypoxia Definition: oxygen deficiency at the tissue level. 1- Hypoxic Hypoxia (hypoxemia): due to decrease O2 in the inspired air 2- Anemic Hypoxia: due to anemia 3- Stagnant Hypoxia: due to cardiovascular disease 4- Histotoxic Hypoxia : The tissues are unable to use O2. Cyanosis Definition: bluish discoloration of the skin and mucous membrane when the amount of reduced hemoglobin above 5gm/100ml capillary blood. Site: lips , fingers (nail bed), ear lobes and tip of nose. Causes: 1. Hypoxic hypoxia 2. Stagnant hypoxia : heart failure 3. Asphyxia Summary  List the mechanisms of carbon dioxide transport  Identify chloride shift phenomenon.  Describe CO2 dissociation Curve  Describe Haldane effect.  Differentiate between Bohr effect and Haldane effect. Learning Resources  Hall JE, Hall ME. Guyton and Hall textbook of medical physiology e-Book. 14ed, Elsevier Health Sciences; 2021. Chapter 40, 511-520 and Chapter 41, 521-530. https://www-clinicalkeycom.gmulibrary.com/#!/content/book/3-s2.0-B9780323597128000412  Barrett, et al.eds. Ganong's Review of Medical Physiology, 26e. McGraw Hill; 2019. Chapter 35: Gas Transport & pH. https://accesspharmacy-mhmedicalcom.gmulibrary.com/content.aspx?bookid=2525&sectionid=204297654#1159055078  https://exchange.scholarrx.com/brick/oxygen-and-carbon-dioxide-transport  Power-point presentation in the Moodle. www.gmu.ac.ae COLLEGE OF MEDICINE Thank you