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Ventilation 27-Apr-17 Ventilation

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Pulmonary Ventilation Tidal volume 500 ml Total ventilation 7500 ml/min Anatomical dead space 150 ml Frequency = 15 per min Alveolar gas 3000 ml Alveolar ventilation 5250 ml/min Pulmonary blood flow 5000 ml/min Pulmonary capillary blood 70 ml 27-Apr-17 Ventilation

Text of Ventilation 27-Apr-17 Ventilation

Ventilation 27-Apr-17 Ventilation Pulmonary Ventilation
Tidal volume 500 ml Total ventilation 7500 ml/min Anatomical dead space 150 ml Frequency = 15 per min Alveolar gas 3000 ml Alveolar ventilation 5250 ml/min Pulmonary blood flow 5000 ml/min Pulmonary capillary blood 70 ml 27-Apr-17 Ventilation Pulmonary Ventilation
Minute ventilation (VE) Volume of air inspired or expired per minute Depends on the frequency (f) Depth of breathing (tidal volume, VT) VE = ( VT * f) 27-Apr-17 Ventilation Pulmonary Ventilation
At rest VT= 500 ml , f = 12 to 15 breath per minute VE= (500 * 12) = 6000 ml/min VE= (500 * 15) = 7500 ml/min 27-Apr-17 Ventilation Anatomical Dead Space Trachea Conducting zone 1 The first 16 generation plus trachea and upper respiratory tract form Conducting zone of the airways Transport gas from & to exterior Bronchi 2 3 4 17 Respiratory bronchiole 18 Trachea, bronchi, bronchioles Warm & humidify air Distribute air to the depth of the lungs Part of the bodys defense system Removal of dust, bacteria, noxious gases from lungs 19 Respiratory zone 20 Alveolar duct 21 22 23 27-Apr-17 Ventilation Anatomical Dead Space Made up of Upper respiratory tract Trachea
Conducting zone 1 Made up of Upper respiratory tract Trachea Bronchi, bronchioles, terminal bronchioles Constitute the anatomical dead space Bronchi 2 3 4 17 Respiratory bronchiole 18 Trachea, bronchi, bronchioles Warm & humidify air Distribute air to the depth of the lungs Part of the bodys defense system Removal of dust, bacteria, noxious gases from lungs 19 Respiratory zone 20 Alveolar duct 21 22 23 27-Apr-17 Ventilation Dead Space Ventilation (VD)
This is a portion of the minute ventilation That fails to reach areas of lungs involved in gas exchange Portion of tidal volume air that remain in dead space (150 ml) Tidal vol = 500 ml Portion of tidal air that gets into alveoli (350 ml) Alveolar air 27-Apr-17 Ventilation Dead Space Ventilation (VD)
Anatomical dead space (VD) Volume of gas occupying the conducting zone of airways Is equal to 150 ml Dead space ventilation Is equal to VD * f 150 * 15 = 2.25 l/min Portion of tidal volume air that remain in dead space (150 ml) Tidal vol = 500 ml Portion of tidal air that gets into alveoli (350 ml) Alveolar air 27-Apr-17 Ventilation Function of Anatomical Dead Space
Conditioning of inspired air Warming the air to body temp Adding moisture Saturate with water vapour Addition of water vapour dilutes oxygen and nitrogen concentration of inspired air 27-Apr-17 Ventilation Function of Anatomical Dead Space
Removal of foreign material Foreign particles Filtered by nose Impacted in lower airways Dissolved on moist surface of airways Small particles (soot, pollen) Impact on the surface of the airways 27-Apr-17 Ventilation Function of Anatomical Dead Space
Impaction Stick to mucus lining Carried in the mucus towards the mouth Expectorated Swallowed Mucus is propelled upwards towards the mouth Cilia of the respiratory epithelium 27-Apr-17 Ventilation Function of Anatomical Dead Space
Foreign materials in inspired gas (cigarette smoke, smog) Stimulate irritant receptors in the airways Cause coughing Increase secretion of mucus Hypertrophy of mucus glands 27-Apr-17 Ventilation Function of Anatomical Dead Space
Prolonged breathing air containing foreign material Cause chronic bronchitis Increase airway resistance, difficult in breathing 27-Apr-17 Ventilation Alveolar Dead Space In health individuals In people with lung diseases
Trachea Conducting zone 1 In health individuals Anatomical dead space represent the entire dead space volume In people with lung diseases Some alveoli do not get blood supply Such alveoli do not participate in gas exchange They constitute alveolar dead space Bronchi 2 3 4 17 Respiratory bronchiole 18 Trachea, bronchi, bronchioles Warm & humidify air Distribute air to the depth of the lungs Part of the bodys defense system Removal of dust, bacteria, noxious gases from lungs 19 Respiratory zone 20 Alveolar duct 21 22 23 27-Apr-17 Ventilation Total Dead Space Total (physiologic) dead space include
Trachea Conducting zone 1 Total (physiologic) dead space include Anatomical dead space Alveolar dead space Bronchi 2 3 4 17 Respiratory bronchiole 18 Trachea, bronchi, bronchioles Warm & humidify air Distribute air to the depth of the lungs Part of the bodys defense system Removal of dust, bacteria, noxious gases from lungs 19 Respiratory zone 20 Alveolar duct 21 22 23 27-Apr-17 Ventilation Alveolar Ventilation Volume of fresh gas that reaches the alveoli per minute Participate in exchange of O2 & CO2 It is equal to Amount of new air reaching the alveolitimes the breathing frequency Portion of tidal volume air that remain in dead space (150 ml) Tidal vol = 500 ml Portion of tidal air that gets into alveoli (350 ml) Alveolar air 27-Apr-17 Ventilation Alveolar Ventilation Alveolar ventilation (VA) VA = (VT VD) * f
VA = 4200 ml/min Portion of tidal volume air that remain in dead space (150 ml) Tidal vol = 500 ml Portion of tidal air that gets into alveoli (350 ml) Alveolar air 27-Apr-17 Ventilation Alveolar Ventilation Alveolar ventilation Alveolar CO2 tension (PACO2)
Major factor in determining the conc of O2 and CO2 in the alveoli Alveolar CO2 tension (PACO2) Regulated at value of 40 mm Hg Determined by the Rate of production Portion of tidal volume air that remain in dead space (150 ml) Tidal vol = 500 ml Portion of tidal air that gets into alveoli (350 ml) Alveolar air 27-Apr-17 Ventilation Alveolar Ventilation Alveolar O2 tension (PA O2)
O2 is continually removed from the alveoli by diffusion Inspiration brings Fresh air into the alveoli Maintain the alveolar O2 tension (PA o2)at about 100 mm Hg Portion of tidal volume air that remain in dead space (150 ml) Tidal vol = 500 ml Portion of tidal air that gets into alveoli (350 ml) Alveolar air 27-Apr-17 Ventilation Alveolar Capillary Gas Exchange
alveoli Pulmonary blood flow 5000 ml/min Pulmonary capillary blood 70 ml 27-Apr-17 Ventilation Alveolar/capillary Exchange
CO2 Composition of alveolar gas mixture Contain respiratory gases Oxygen, carbon dioxide Together with Nitrogen, water vapour O2 Alveolar space CO2 O2 CO2 O2 27-Apr-17 Ventilation Alveolar/capillary Exchange
CO2 The volume of alveolar space Functional residual capacity (FRC) 2.4 to 3 liters To this vol fresh air is added O2 is removed CO2 is added O2 Alveolar space CO2 O2 CO2 O2 27-Apr-17 Ventilation Alveolar/capillary Exchange
CO2 The conc of O2 in the alveoli (FAO2) depends on Rate of diffusion of oxygen in blood (VO2) Oxygen uptake Rate of entry of O2 into the lung (FIo2) * (VA) O2 Alveolar space CO2 O2 CO2 O2 27-Apr-17 Ventilation Alveolar/capillary Exchange
CO2 Where (FIO2) is the conc of O2 in inspired air (VA) is alveolar ventilation O2 Alveolar space CO2 O2 CO2 O2 27-Apr-17 Ventilation Alveolar/capillary Exchange
CO2 The alveolar CO2 conc(FACO2) depends on Rate of excretion of CO2 from blood into alveolar Rate of CO2 removal from the alveoli (FACO2) * (VA) O2 Alveolar space CO2 O2 CO2 O2 27-Apr-17 Ventilation Alveolar/capillary Exchange
CO2 Where (FACO2) is the alveolarCO2 conc (VA) is alveolar ventilation O2 Alveolar space CO2 O2 CO2 O2 27-Apr-17 Ventilation Alveolar Partial Pressures
In a mixture of gases Each gas exerts its own partial pressure (tension) According to Daltons law Partial pressure equal Fraction of gas present (concentration) times the total pressure Partial pressure of gas in a mixture is a measure of the concentration of the gas in the mixture 27-Apr-17 Ventilation Partial Pressure % Composition of dry air at sea level contain
Total pressure *% conc For O2 Po2= 760 * = 159 mm hg 27-Apr-17 Ventilation Partial Pressure For CO2 For N2 PCO2 = 760 * 0.0003 = 0.2 mm Hg
PN2= 760 * = 600 mm Hg 27-Apr-17 Ventilation Partial pressures & conc of O2, CO2 in alveoli
Oxygen Conc of O2in alveoli (FAO2)& PAO2 Depend on Rate of diffusion into blood (VO2) Rate of entry of O2 in lungs (FIO2) * (VA) Alveoli FAO2 PACO2 PAO2 CO2 O2 CO2 O2 Pulmonary capillary 27-Apr-17 Ventilation Partial pressures & conc of O2, CO2 in alveoli
Hence If you increase O2 consumption (VO2) You need to increase alveolar ventilation (VA) To maintain PAO2 at 100 mmHg Alveoli FAO2 PACO2 PAO2 CO2 O2 CO2 O2 Pulmonary capillary 27-Apr-17 Ventilation Partial Pressures & conc of O2, CO2 in Alveoli
When the oxygen uptake (VO2) is 250 ml/min You require alveolar vent of about 5 liters /min to maintain PAO2 = 100mm Hg VO2 = 250 ml/min 150 100 PAO2 = 100 mm Hg PAO2 & PACO2 mm Hg VO2 = 1000 ml/min 40 PACO2 = 40 mm Hg 20 30 5 10 15 Alveolar ventilation (L/min) 27-Apr-17 Ventilation Partial Pressures & conc of O2, CO2 in Alveoli
When the oxygen uptake (VO2) is 1000 ml/min You require alveolar vent of about 20 liters /min to maintain PAO2 = 100mm Hg VO2 = 250 ml/min 150 100 PAO2 = 100 mm Hg PAO2 & PACO2 mm Hg VO2 = 1000 ml/min 40 PACO2 = 40 mm Hg 20 30 5 10 15 Alveolar ventilation (L/min) 27-Apr-17 Ventilation Partial pressures & conc of O2, CO2 in alveoli
For CO2 The alveolar CO2 conc (FACO2) and the PACO2 depend on rate of Excretion of CO2 from blood into the alveoli CO2 removal from alveoli (VA * FACO2) Alveoli FAO2 PACO2 PAO2 CO2 O2 CO2 O2 Pulmonary capillary 27-Apr-17 Ventilation Partial Pressure of Respiratory Gases (mm Hg)
Atmospheric air Alveolar gas Expired air O2 159.0 (20.84%) 104.0 (13.6%) 120.0 (15.7%) CO2 0.3 (0.04%) 40.0 (5.3%) 26.0 (3.6%) N2 597.0 (78.62%) 569.0 (74.9%) 566.0 (74.5) H2O 3.7 (0.5%) 47.0 (6.2%) Total 760 (100%) From Guyton 27-Apr-17 Ventilation Diffusion 27-Apr-17 Ventilation Diffusion of Gases Through the Respiratory Membrane
Ficks law The rate of transfer of gas through a sheet of tissue is proportional to Tissue area Diffusing gas partial pressures Is inversely proportion

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