Respiratory Physiology
Ho Jae Han
College of Veterinary Medicine
Seoul National University
Contents
Respiratory physiology
I. Lung volumes and capacities
II. Mechanics of breathing
III. Gas exchange
IV. Oxygen transport
V. CO2 Transport
VI. Pulmonary circulation
VII. V/Q defects
VIII. Control of breathing
IX. Integrated responses of the respiratory system
X. Non-respiratory system of the lung
XI. Respiration in birds
Lung volumes and capacities - Spirometry
Mechanics of breathing - Breathing cycle-pressures and airflow
Mechanics of breathing - Alveolar surface tension & surfactant
Mechanics of breathing – Surfactant production by type II alveolar cells
Mechanics of breathing - FEV1/FVC values in obstructive & restrictive lung diseases
Mechanics of breathing – Spirometry of obstructive & restrictive lung diseases
Gas exchange - Partial pressures of O2 and CO2
Gas exchange - Diffusion of O2 and CO2
Gas exchange - Perfusion/diffusion limited gas exchange
Oxygen transport - O2 binding capacity and O2 content of blood
O2-binding capacity of blood
-maximum amount of O2 that can be bound to hemoglobin(Hb) of blood
-measured at 100% saturation
-dependent on: Hb concentration of blood
O2 content of blood
-total amount of O2 in blood
-Bound O2 + dissolved O2
-dependent on: Hb concentration, Po2, P50 of Hb
Oxygen transport - Hb-O2 dissociation curve
At a PO2 of 100mmHg (e.g., arterial blood)
- hemoglobin is 100% saturated; O2 is bound to
all four heme groups on all hemoglobin molecules.
At a PO2 of 40mmHg (e.g., mixed venous blood)
- hemoglobin is 75% saturated,
At a PO2 of 25mmHg (P50)
- hemoglobin is 50% saturated.
Oxygen transport - Changes in the Hb-O2 dissociation curve
Bohr effect:
Increases in Pco2 or decreases in pH shift the curve
to the right by decreasing affinity of Hb for O2
Oxygen transport - Hypoxemia and Hypoxia: causes of hypoxemia
Hypoxemia: decrease in arterial Po2
Oxygen transport - A-a gradient and the alveolar gas equation
Oxygen transport - Hypoxemia and Hypoxia: causes of hypoxia
Hypoxia: decreased O2 delivery to the tissues
O2 delivery = Cardiac Output X O2 content of blood
CO2 transport - Transportation of CO2 in Blood
1. Dissolved CO2: minor
2. CO2 bound to hemoglobin (carbaminohemoglobin): minor
3. HCO3- (by hydration CO2 in RBC): major (90%)
Pulmonary circulation - Shunts
Right-to-left shunt Left-to-right shunt
Admixture of venous blood with arterial Admixture of arterial blood with venous
blood blood
Decrease in arterial Po2 No decrease of arterial Po2
Tetralogy of Fallot Patent ductus arteriosus
Pulmonary circulation - Distribution of pulmonary blood flow
Ventilation/perfusion ratio - V/Q distribution in the lung
Control of Breathing - Central control of breathing
Control of Breathing - Central and peripheral chemoreceptors
Sensitive to pH (H+) Sensitive to Pco2, Po2, [H+]
Respiratory responses - Exercise
Respiratory responses - Adaptation to high altitude
Avian respiration - Anatomy of bronchi
Avian respiration – Inhalation & exhalation
Avian respiration – Structure of parabronchus
Avian respiration – Mechanism of counter-current gas exchange
ET Exchange tissue
PL Parabronchial lumen
IPA Inter-parabronchial artery
IPV Inter-parabronchial vein
MSAS Multi-capillary arterialization
system
Avian respiration – Comparison of avian and mammalian gas exchange
Avian respiration – Effect of counter-current gas exchange
Co-current gas exchange Counter-current gas exchange
