Respiratory Physiology

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Respiratory Physiology Matter of WHY &HOW ? : 

1 Respiratory Physiology Matter of WHY &HOW ? Respiratory Physiology Matter of WHY &HOW ? By Dr. Nermine Mounir Lecturer of Chest Diseases Faculty of Medicine Ain shams University

Respiratory System Functions : 

2 Respiratory Physiology Matter of WHY &HOW ? Respiratory System Functions Gas exchange: Oxygen enters blood and carbon dioxide leaves Regulation of blood pH: Altered by changing blood carbon dioxide levels Voice production: Movement of air past vocal folds makes sound and speech Olfaction: Smell occurs when airborne molecules drawn into nasal cavity Protection: Against microorganisms by preventing entry and removing them

Non-Respiratory Lung Functions : 

3 Respiratory Physiology Matter of WHY &HOW ? Non-Respiratory Lung Functions Reservoir of blood available for circulatory compensation Filter for circulation: thrombi, microaggregates etc Metabolic activity: activation: angiotensin III inactivation: noradrenaline bradykinin 5 H-T some prostaglandins Immunological: IgA secretion into bronchial mucus

The Respiratory Defense System : 

4 Respiratory Physiology Matter of WHY &HOW ? The Respiratory Defense System Consists of a series of filtration mechanisms Removes particles and pathogens * Components of the Respiratory Defense System Goblet cells and mucous glands: produce mucus that bathes exposed surfaces Cilia: sweep debris trapped in mucus toward the pharynx (mucus escalator) Filtration in nasal cavity removes large particles Alveolar macrophages engulf small particles that reach lungs

Pulmonary Function Testing : 

5 Respiratory Physiology Matter of WHY &HOW ? Pulmonary Function Testing Tests can be divided into categories: Airway Function Lung Volumes and Gas Distribution Diffusing Capacity Blood Gas and Exchange Tests Cardiopulmonary Exercise Tests

Indications : 

6 Respiratory Physiology Matter of WHY &HOW ? Indications Detect disease Evaluate extent and monitor course of disease Evaluate treatment Measure effects of exposures Assess risk for surgical procedures

Contraindications of PFTs : 

7 Respiratory Physiology Matter of WHY &HOW ? Contraindications of PFTs Patient with poor coordination or lack of ability Patient with severe dyspnea Very old or very young patient Those who cannot follow specific instructions Patients with contagious diseases, i.e., TB Patients with aneurysms, hernias, pulm. emboli, or arrhythmias

The Airways : 

8 Respiratory Physiology Matter of WHY &HOW ? Weibel ER: Morphometry of the Human Lung. Berlin and New York: Springer-Verlag, 1963 The Airways Conducting zone: no gas exchange occurs Anatomic dead space Transitional zone: alveoli appear, but are not great in number Respiratory zone: contain the alveolar sacs

Respiration : 

9 Respiratory Physiology Matter of WHY &HOW ? Respiration Ventilation: Movement of air into and out of lungs External respiration: Gas exchange between air in lungs and blood Transport of oxygen and carbon dioxide in the blood Internal respiration: Gas exchange between the blood and tissues

Intrapulmonary Pressure : 

10 Respiratory Physiology Matter of WHY &HOW ? Intrapulmonary Pressure Also called intra-alveolar pressure Is relative to Patm In relaxed breathing, the difference between Patm and intrapulmonary pressure is small: about —1 mm Hg on inhalation or +1 mm Hg on expiration

Intrapleural Pressure : 

11 Respiratory Physiology Matter of WHY &HOW ? Intrapleural Pressure Pressure in space between parietal and visceral pleura Averages —4 mm Hg Maximum of —18 mm Hg Remains below Patm throughout respiratory cycle

Transpulmonary Pressure : 

12 Respiratory Physiology Matter of WHY &HOW ? Transpulmonary Pressure Transpulmonary pressure = Alveolar pressure* – Pleural pressure *With no air movement and an open upper airway, mouth pressure equals alveolar pressure

Pulmonary Pressures : 

13 Respiratory Physiology Matter of WHY &HOW ? Pulmonary Pressures

The Mechanics of Breathing : 

14 Respiratory Physiology Matter of WHY &HOW ? The Mechanics of Breathing Inhalation: always active Exhalation: active or passive

3 Muscle Groups of Inhalation : 

15 Respiratory Physiology Matter of WHY &HOW ? 3 Muscle Groups of Inhalation Diaphragm: contraction draws air into lungs 75% of normal air movement External intracostal muscles: assist inhalation 25% of normal air movement Accessory muscles assist in elevating ribs: sternocleidomastoid serratus anterior pectoralis minor scalene muscles

Muscles of Active Exhalation : 

16 Respiratory Physiology Matter of WHY &HOW ? Muscles of Active Exhalation Internal intercostal and transversus thoracis muscles: depress the ribs Abdominal muscles: compress the abdomen force diaphragm upward

Alveolar Pressure Changes : 

17 Respiratory Physiology Matter of WHY &HOW ? Alveolar Pressure Changes

Inspiration : 

18 Respiratory Physiology Matter of WHY &HOW ? Inspiration Active process – requires ATP for muscles contraction

Expiration : 

19 Respiratory Physiology Matter of WHY &HOW ? Expiration Passive process –muscles relax

Airway resistance : 

20 Respiratory Physiology Matter of WHY &HOW ? Airway resistance Caused by: Elastic recoil of lung and chest wall Inertia of the respiratory system Frictional resistance of the lung and chest wall Frictional resistance of the airways to airflow Pulmonary tissue resistance Airway resistance (80%)+ pulmonary tissue resistance (20%) = Pulmonary resistance

Airway Resistance : 

21 Respiratory Physiology Matter of WHY &HOW ? Friction Flow (F), pressure (P), and resistance (R) is: Airway Resistance ?P Pressure gradient Gas flow is inversely proportional to resistance with the greatest resistance being in the medium-sized bronchi

Resistance : 

22 Respiratory Physiology Matter of WHY &HOW ? Resistance Length Viscosity of substance Radius R ? L?/r4

Surface Tension : 

23 Respiratory Physiology Matter of WHY &HOW ? Surface Tension Lung collapse Surface tension tends to oppose alveoli expansion Pulmonary surfactant reduces surface tension

Surfactant : 

24 Respiratory Physiology Matter of WHY &HOW ? Surfactant Produced and secreted into the alveolar airspace by alveolar Type II cells Begins week 25 of fetal development in humans reaching functional levels at 32 weeks, eight weeks before normal delivery Respiratory distress syndrome: Premature infants born before 32 weeks

Surfactant : 

25 Respiratory Physiology Matter of WHY &HOW ? Surfactant Increases compliance Decreases surface tension in alveoli and prevents small alveoli from collapsing, equalizing pressure between large and small alveoli Prevent Pulmonary oedema.

Slide 26: 

26 Respiratory Physiology Matter of WHY &HOW ?

Compliance of the Lung : 

27 Respiratory Physiology Matter of WHY &HOW ? Compliance of the Lung An indicator of expandability Low compliance requires greater force High compliance requires less force Factors That Affect Compliance Connective-tissue structure of the lungs Level of surfactant production Mobility of the thoracic cage

Compliance varies within the lung according to the degree of inflation : 

28 Respiratory Physiology Matter of WHY &HOW ? Compliance varies within the lung according to the degree of inflation Poor compliance is seen at low volumes (because of difficulty with initial lung inflation) and at high volumes (because of the limit of chest wall expansion) Best compliance is in the mid-expansion range.

Work of breathing : 

29 Respiratory Physiology Matter of WHY &HOW ? Work of breathing Work to overcome the elastic forces of the lung Work to overcome the viscosity of the lung and the chest wall structures. Work to overcome airway resistance. Normal respiration uses 3-5% of total work energy Heavy exercise can require 50 x more energy

Volumes Versus Capacities. : 

30 Respiratory Physiology Matter of WHY &HOW ? Volumes Versus Capacities. There are four volume subdivisions which: do not overlap. can not be further divided. when added together equal total lung capacity. Lung capacities are subdivisions of total volume that include two or more of the 4 basic lung volumes.

Pulmonary Volumes : 

31 Respiratory Physiology Matter of WHY &HOW ? Pulmonary Volumes Tidal volume Volume of air inspired or expired during a normal inspiration or expiration Inspiratory reserve volume Amount of air inspired forcefully after inspiration of normal tidal volume Expiratory reserve volume Amount of air forcefully expired after expiration of normal tidal volume Residual volume Volume of air remaining in respiratory passages and lungs after the most forceful expiration

Pulmonary Capacities : 

32 Respiratory Physiology Matter of WHY &HOW ? Pulmonary Capacities Inspiratory capacity Tidal volume plus inspiratory reserve volume Functional residual capacity Expiratory reserve volume plus the residual volume Vital capacity Sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume Total lung capacity Sum of inspiratory and expiratory reserve volumes plus the tidal volume and residual volume

Slide 33: 

33 Respiratory Physiology Matter of WHY &HOW ? Respiratory volumes

Spirometer and Lung Volumes/Capacities : 

34 Respiratory Physiology Matter of WHY &HOW ? Spirometer and Lung Volumes/Capacities

Spirometry : 

35 Respiratory Physiology Matter of WHY &HOW ? Spirometry Measurement of the air moving in and out of the lungs during various respiratory maneuvers. It allows one to determine how much air can be inhaled and exhaled , and how fast.

Silhouette of Hutchinson Performing Spirometry : 

36 Respiratory Physiology Matter of WHY &HOW ? Silhouette of Hutchinson Performing Spirometry From Chest, 2002

Lung Factors Affecting Spirometry : 

37 Respiratory Physiology Matter of WHY &HOW ? Lung Factors Affecting Spirometry Mechanical properties Resistive elements

Mechanical Properties : 

38 Respiratory Physiology Matter of WHY &HOW ? Mechanical Properties Compliance Describes the stiffness of the lungs Change in volume over the change in pressure Elastic recoil The tendency of the lung to return to it’s resting state A lung that is fully stretched has more elastic recoil and thus larger maximal flows

Resistive Properties : 

39 Respiratory Physiology Matter of WHY &HOW ? Resistive Properties Determined by airway caliber Affected by Lung volume Bronchial smooth muscles Airway collapsibility

Data generated : 

40 Respiratory Physiology Matter of WHY &HOW ? Data generated Volume time curve (spirogram) FEV1, FVC, Ratio Flow volume loop Peak flow FVC FEF 25-75 Inspiratory flow data

Flow-Volume Loop : 

41 Respiratory Physiology Matter of WHY &HOW ? Flow-Volume Loop Illustrates maximum expiratory and inspiratory flow-volume curves Useful to help characterize disease states (e.g. obstructive vs. restrictive) Ruppel GL. Manual of Pulmonary Function Testing, 8th ed., Mosby 2003

Breathing : 

42 Respiratory Physiology Matter of WHY &HOW ? Breathing

Pulmonary Factors Can Reduce Vital Capacity : 

43 Respiratory Physiology Matter of WHY &HOW ? Pulmonary Factors Can Reduce Vital Capacity Loss of Distensible Tissue e.g. pneumonectomy, atelectasis. Decreased Compliance. e.g. respiratory distress syndrome, alveolar edema, or infiltrative interstitial lung diseases. Increased Residual Volume. e.g. emphysema, asthma, or lung cysts.

Extrapulmonary Factors Can Reduce Vital Capacity : 

44 Respiratory Physiology Matter of WHY &HOW ? Extrapulmonary Factors Can Reduce Vital Capacity Limited Thoracic Expansion. e.g. thoracic deformities (Kyphoscoliosis) and pleural fibrosis. Limited Diaphragmatic Descent. e.g. ascites and pregnancy. Nerve or Muscle Dysfunction. Pain (surgery, rib fracture) Primary neuromuscular disease (e.g. Guillain-Barré Syndrome).

Airway Function Tests : 

45 Respiratory Physiology Matter of WHY &HOW ? Airway Function Tests Spirometry Flow – Volume Loop (FVL)

Slide 46: 

46 Respiratory Physiology Matter of WHY &HOW ? Airflow obstruction Mild on left Severe on right

Slide 47: 

47 Respiratory Physiology Matter of WHY &HOW ? Pulmonary restriction

Slide 48: 

48 Respiratory Physiology Matter of WHY &HOW ? Variable extrathoracic Fixed Large airway obstruction

FVC : 

49 Respiratory Physiology Matter of WHY &HOW ? FVC Interpretation of % predicted: 80-120% Normal 70-79% Mild reduction 50%-69% Moderate reduction <50% Severe reduction FVC

FEV1 : 

50 Respiratory Physiology Matter of WHY &HOW ? FEV1 Interpretation of % predicted: >70 Mild 60-69 Moderate 50-59 Moderately severe obstruction 35-49 Severe <35 Very severe FEV1 FVC

FEF25-75 : 

51 Respiratory Physiology Matter of WHY &HOW ? FEF25-75 Interpretation of % predicted: >60% Normal 40-60% Mild obstruction 20-40% Moderate obstruction <10% Severe obstruction

Lung volumes : 

52 Respiratory Physiology Matter of WHY &HOW ? Lung volumes Dynamic lung volumes Static lung volumes

Residual Volume is determined by one of 3 techniques. : 

53 Respiratory Physiology Matter of WHY &HOW ? Residual Volume is determined by one of 3 techniques. Gas Dilution Techniques Nitrogen washout Helium dilution Whole Body Plethysmography Radiography

Volume-constant body plethysmograph : 

54 Respiratory Physiology Matter of WHY &HOW ? Volume-constant body plethysmograph

Functions of body box : 

55 Respiratory Physiology Matter of WHY &HOW ? Functions of body box 1-Allows complete analysis of breathing mechanics of the respiratory system? Specific airway resistance(sRaw) Intrathoracic gas volume (FRCpleth) Both ?Airway resistance (Raw) 2-In combination with spirometry ? Absolute volumes ?RV-TLC Partial volumes ? ERV-IRV Lung capacities ? VC-IC

Three types of measurments: : 

56 Respiratory Physiology Matter of WHY &HOW ? Three types of measurments: 1- Insp. and exp. flow rate during the breathing cycle. 2-Air volume changes inside the cabinet 3 – Changes in air pressure at the subject mouth 1+2 ?Determine sRaw 2+3 ?Determine ITGV

Boyle’s Law : 

57 Respiratory Physiology Matter of WHY &HOW ? Boyle’s Law If temperature is constant: Pressure1 x Volume1 = Pressure2 x Volume2 P1 and V1 are the absolute pressure and volume before the manoeuvre while P2 and V2 are the prssure and volume after the manoeuvre.

Body - Measurement : 

58 Respiratory Physiology Matter of WHY &HOW ? Body - Measurement

Calculated parameters : 

59 Respiratory Physiology Matter of WHY &HOW ? Calculated parameters RV = FRCplet – ERV TLC = VC + RV

Important resistance parameters : 

60 Respiratory Physiology Matter of WHY &HOW ? Important resistance parameters sRtot ? the points of max. volume shift on the loop. ?high sensitivity down to the peripheral airways. sReff ? derived from the area covered by the work of breathing. ?high sensitivity within the central airways. Rtot= sRtot/(FRCplet +VT/2) Reff= sReff/(FRCplet +VT/2)

Interpretation : 

61 Respiratory Physiology Matter of WHY &HOW ? Interpretation Shape of the graphs resistance ? Raw =0.6-2.8 cm/L/sec sRaw =0.19-0.667 cm/L/sec pred./best < 80% Lung volumes? FRC and RV?65-135% TLC? 80-120% RV/TLC%? 20-35% VC ?80-120%

Lung volumes : 

62 Respiratory Physiology Matter of WHY &HOW ? Lung volumes

What about lung volumes and obstructive and restrictive disease? : 

63 Respiratory Physiology Matter of WHY &HOW ? What about lung volumes and obstructive and restrictive disease?

COPD : 

COPD

Asthma : 

Asthma

Emphysema+asthma : 

Emphysema+asthma

Restriction : 

Restriction

Slide 68: 

68 Respiratory Physiology Matter of WHY &HOW ? The main function of the lung is to establish gas exchange between the body tissues and the surrounding air.O2 is taken up and CO2 is eliminated. This function can be subdivided into 3 stages: 1-Ventilation 2-Alveolar-capillary diffusion 3-Perfusion

Respiratory Membrane - The thin membrane of alveoli where gas exchange takes place : 

69 Respiratory Physiology Matter of WHY &HOW ? Respiratory Membrane - The thin membrane of alveoli where gas exchange takes place Parts of the Respiratory Membrane Squamous epithelial lining of alveolus Basement membrane Interstial fluid Endothelial cells lining an adjacent capillary Diffusion- Across respiratory membrane is very rapid: because distance is small gases (O2 and CO2) are lipid soluble

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70 Respiratory Physiology Matter of WHY &HOW ?

Gas Pressure : 

71 Respiratory Physiology Matter of WHY &HOW ? Gas Pressure Atmospheric pressure (760 mm Hg): produced by air molecules bumping into each other Each gas contributes to the total pressure: in proportion to its number of molecules (Dalton’s law)

Partial Pressure: Dalton’s Law : 

72 Respiratory Physiology Matter of WHY &HOW ? Partial Pressure: Dalton’s Law In a gas mixture the pressure exerted by each individual gas in a space is independent of the pressures of other gases in the mixture Pgas = % of total gases x Ptotal

Composition of Air : 

73 Respiratory Physiology Matter of WHY &HOW ? Composition of Air Nitrogen (N2) about 78.6% Oxygen (O2) about 20.9% Water vapor (H2O) about 0.5% Carbon dioxide (CO2) about 0.04%

Partial Pressure : 

74 Respiratory Physiology Matter of WHY &HOW ? Partial Pressure The pressure contributed by each gas in the atmosphere All partial pressures together add up to 760 mm Hg

Henry’s Law : 

75 Respiratory Physiology Matter of WHY &HOW ? Henry’s Law The amount of gas absorbed by a liquid with which it does not combine chemically is directly proportional to the partial pressure and the solubility of the gas in the liquid.

Henry’s Law : 

76 Respiratory Physiology Matter of WHY &HOW ? Henry’s Law Figure 23–18 When gas under pressure comes in contact with liquid: gas dissolves in liquid until equilibrium is reached At a given temperature: amount of a gas in solution is proportional to partial pressure of that gas

Gas solubility : 

77 Respiratory Physiology Matter of WHY &HOW ? Gas solubility CO2 20 times more soluble in water than O2 N2 almost insoluble H2O H2O H2O Carbondioxide Oxygen Nitrogen

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78 Respiratory Physiology Matter of WHY &HOW ?

Physical Principles of Gas Exchange : 

79 Respiratory Physiology Matter of WHY &HOW ? Physical Principles of Gas Exchange Diffusion of gases through the respiratory membrane Depends on membrane’s thickness, the diffusion coefficient of gas, surface areas of membrane, partial pressure of gases in alveoli and blood, volume of capillary network, contact time Relationship between ventilation and pulmonary capillary flow Increased ventilation or increased pulmonary capillary blood flow increases gas exchange

Fick’s Law for Diffusion for Gases : 

80 Respiratory Physiology Matter of WHY &HOW ? Fick’s Law for Diffusion for Gases

Gas Diffusion : 

81 Respiratory Physiology Matter of WHY &HOW ? Gas Diffusion The alveoli provide an enormous surface area for gas exchange with pulmonary blood (between 50-100m2) Under resting conditions pulmonary capillary blood is in contact with the alveolus for about 0.75 second in total and is fully equilibrated with alveolar oxygen after only about a third of the way along this course. Lung disease impairs diffusion: At rest there is usually still sufficient time for full equilibration of oxygen During exercise, pulmonary blood flow is quicker, shortening the time available for gas exchange, and so those with lung disease are unable to oxygenate the pulmonary blood fully and thus have a limited ability to exercise. Carbon dioxide diffuses across the alveolar-capillary membrane 20 times faster than oxygen so the above factors are less liable to compromise transfer from blood to alveoli.

Pathway for diffusion : 

82 Respiratory Physiology Matter of WHY &HOW ? Pathway for diffusion

Slide 83: 

83 Respiratory Physiology Matter of WHY &HOW ? What is the pulmonary diffusion capacity and what are the factors affecting it??

Slide 84: 

84 Respiratory Physiology Matter of WHY &HOW ? Pulmonary diffusion capacity (DL) is the amount of gas which is transferred between alveolar space and capillary blood ,per minute and per partial pressure difference. It measures the effectiveness of gas exchange.

The factors affecting diffusion: : 

85 Respiratory Physiology Matter of WHY &HOW ? The factors affecting diffusion: The active Surface area The partial pressure difference of the gas The thickness of the alveolar-capillary membrane The molecular weight of gas and its solubility The intravascular component: diffusion through the plasma and the reaction with hemoglobin Growth and aging Lung volume Ventilatory flow Perfusion Standards of the examination

Patient Preparation : 

86 Respiratory Physiology Matter of WHY &HOW ? Patient Preparation Patients should be asked to refrain from smoking for 24 hours before the test. Patients should avoid alcohol for at least 4 hours before testing. The test should be performed at least 2 hours after eating and with the patient having refrained from recent strenuous exercise. The patient should be seated for at least 5 minutes before testing and remain seated throughout the procedure. Supplemental O2 should be discontinued at least 5 minutes before beginning the test. If this cannot be done safely, the results interpreted with caution. Assessment of patients

How to perform CO –Diffusion Single Breath test ? : 

87 Respiratory Physiology Matter of WHY &HOW ? How to perform CO –Diffusion Single Breath test ? After entering regular tidal breathing , the patient is asked to maximal expirate to residual volume. As fast as possible he then inspires a composed gas mixture of about 9% helium and 0.3% CO until he reaches TLC . At TLC a valve is closed and the patient hold his breath for about 8-10 sec. Then deep expiration is followed.

Slide 88: 

88 Respiratory Physiology Matter of WHY &HOW ?

DL,CO INTERPRETATION : 

89 Respiratory Physiology Matter of WHY &HOW ? DL,CO INTERPRETATION Interpreting the DL,CO, in conjunction with spirometry and lung volumes assessment, may assist in diagnosing the underlying disease.

Slide 90: 

90 Respiratory Physiology Matter of WHY &HOW ? Adjustments of DL,CO for changes in haemoglobin and carboxyhaemoglobin are important, especially in situations where patients are being monitored for possible drug toxicity, and where haemoglobin is subject to large shifts (e.g.chemotherapy for cancer).

DLCO Interpretation : 

91 Respiratory Physiology Matter of WHY &HOW ? DLCO Interpretation Low DLCO with normal spirometry Pulmonary Vascular Disease Anaemia - correct for Hb Early ILDs or early emphysema Chronic pulmonary embolism Primary pulmonary hypertension Low DLCO with restriction Interstitial Lung Disease Low DLCO with obstruction Emphysema COPD Lymphangioleiomyomatosis DO NOT USE DLCO/VA or KCO Often Normal in Interstitial Lung Disease

Possible Causes* of High DLCo : 

92 Respiratory Physiology Matter of WHY &HOW ? Possible Causes* of High DLCo Intrapulmonary Haemorrhage Asthma Obesity ??? *DLCO is not always high in these patients

Important parameters : 

93 Respiratory Physiology Matter of WHY &HOW ? Important parameters DLCOsb Diffusing capacity of CO KCO DLCO per VA (krogh factor) VA Alveolar volume RV Residual volume TLC Total lung capacity ERV Expiratory reserve volume Hb Hemoglobin FRC Functional residual capacity

Slide 94: 

94 Respiratory Physiology Matter of WHY &HOW ? Adjusting DL,CO for lung volume using DL,CO/VA or DL,CO/TLC is controversial . Conceptually, a loss of DL,CO that is much less than a loss of volume (low DL,CO but high DL,CO/VA) might suggest an extraparenchymal abnormality, such as a pneumonectomy or chest wall restriction. whereas, a loss of DL,CO that is much greater than a loss of volume (low DL,CO and low DL,CO/VA) might suggest parenchymal abnormalities.

Slide 95: 

95 Respiratory Physiology Matter of WHY &HOW ? Degree of severity of decrease in diffusing capacity for carbon monoxide (DL,CO) Degree of severity DL,CO % pred Mild 60% -80% Moderate 40–60% Severe <40 % pred: % predicted; LLN: lower limits of normal

Interpretation Flow Chart : 

96 Respiratory Physiology Matter of WHY &HOW ? Interpretation Flow Chart

Hemoglobin and Oxygen Transport : 

97 Respiratory Physiology Matter of WHY &HOW ? Hemoglobin and Oxygen Transport Oxygen is transported by hemoglobin (98.5%) and is dissolved in plasma (1.5%) Oxygen-hemoglobin dissociation curve shows that hemoglobin is almost completely saturated when P02 is 80 mm Hg or above. At lower partial pressures, the hemoglobin releases oxygen. A shift of the curve to the left because of an increase in pH, a decrease in carbon dioxide, or a decrease in temperature results in an increase in the ability of hemoglobin to hold oxygen

Hemoglobin and Oxygen Transport : 

98 Respiratory Physiology Matter of WHY &HOW ? Hemoglobin and Oxygen Transport A shift of the curve to the right because of a decrease in pH, an increase in carbon dioxide, or an increase in temperature results in a decrease in the ability of hemoglobin to hold oxygen The substance 2.3-bisphosphoglycerate increases the ability of hemoglobin to release oxygen Fetal hemoglobin has a higher affinity for oxygen than does maternal

Oxyhemoglobin Dissociation Curve : 

99 Respiratory Physiology Matter of WHY &HOW ? Oxyhemoglobin Dissociation Curve Reprinted, by permission, from S.K. Powers and E.T. Howley, 2004, Exercise physiology: Theory and application to fitness and performance, 5th ed. (New York: McGraw-Hill Companies), 205. With permission from The McGraw-Hill Companies.

Significance of Sigmoid Curve4 Point Curve : 

100 Respiratory Physiology Matter of WHY &HOW ? Significance of Sigmoid Curve4 Point Curve

Four (+one) Things Change Oxyhemoglobin Affinity : 

101 Respiratory Physiology Matter of WHY &HOW ? Four (+one) Things Change Oxyhemoglobin Affinity Hydrogen Ion Concentration, [H+] Carbon Dioxide Partial Pressure, PCO2 Temperature [2,3-DPG] Special Case: Carbon Monoxide

Effects of pH and Temperature on the Oxyhemoglobin Dissociation Curve : 

102 Respiratory Physiology Matter of WHY &HOW ? Effects of pH and Temperature on the Oxyhemoglobin Dissociation Curve Reprinted, by permission, from S.K. Powers and E.T. Howley, 2004, Exercise physiology: Theory and application to fitness and performance, 5th ed. (New York: McGraw-Hill Companies), 206. With permission from The McGraw-Hill Companies.

Transport of Carbon Dioxide : 

103 Respiratory Physiology Matter of WHY &HOW ? Transport of Carbon Dioxide Carbon dioxide is transported as bicarbonate ions (70%) in combination with blood proteins (23%) and in solution with plasma (7%) Hemoglobin that has released oxygen binds more readily to carbon dioxide than hemoglobin that has oxygen bound to it (Haldane effect) In tissue capillaries, carbon dioxide combines with water inside RBCs to form carbonic acid which dissociates to form bicarbonate ions and hydrogen ions

Transport of Carbon Dioxide : 

104 Respiratory Physiology Matter of WHY &HOW ? Transport of Carbon Dioxide In lung capillaries, bicarbonate ions and hydrogen ions move into RBCs and chloride ions move out. Bicarbonate ions combine with hydrogen ions to form carbonic acid. The carbonic acid is converted to carbon dioxide and water. The carbon dioxide diffuses out of the RBCs. Increased plasma carbon dioxide lowers blood pH. The respiratory system regulates blood pH by regulating plasma carbon dioxide levels

Carbon Dioxide Transport : 

105 Respiratory Physiology Matter of WHY &HOW ? Carbon Dioxide Transport Bicarbonate ions Muscle: CO2 + H2O ? H2CO3 ? H+ + HCO3- Lung: H+ + HCO3- ? H2CO3 ? CO2 + H2O Dissolved in blood plasma Bound to hemoglobin (carbaminohemoglobin)

CO2 Transport and Cl- Movement : 

106 Respiratory Physiology Matter of WHY &HOW ? CO2 Transport and Cl- Movement

Bohr Effect : 

Bohr Effect Unit 1 - Objective 8 Bohr Shift Curve

The Bohr Effect : 

The Bohr Effect Did you notice that when PCO2 increased from 40 to 80 mm Hg, oxygen saturation decreased from 75 % to about 65 %. This made an extra 10% oxygen available to the tissues. This would come in handy during increased activity. The Bohr shift is a very positive adaptation!

Summary: Gas Transport : 

109 Respiratory Physiology Matter of WHY &HOW ? Summary: Gas Transport

Slide 110: 

110 Respiratory Physiology Matter of WHY &HOW ? HALDANE EFFECT AT THE LUNGS BOHR EFFECT AT THE TISSUES

Ventilation : 

111 Respiratory Physiology Matter of WHY &HOW ? Ventilation The distribution of ventilation across the lung is related to the position of each area on the compliance curve at the start of a normal tidal inspiration (the point of the FRC) Because the bases are on a more favourable part of the compliance curve than the apices, they gain more volume change from the pressure change applied and thus receive a greater degree of ventilation. Although the inequality between bases and apices is less marked for ventilation than for perfusion, overall there is still good V/Q matching and efficient oxygenation of blood passing through the lungs.

Ventilation-Perfusion Coupling : 

112 Respiratory Physiology Matter of WHY &HOW ? Ventilation-Perfusion Coupling Ventilation Perfusion Ventilation and perfusion must be tightly regulated for efficient gas exchange Changes in alveoli PO2 Low PO2 High PO2 Changes in PCO2 in the alveoli Dilate Constrict

V/Q Mismatching : 

113 Respiratory Physiology Matter of WHY &HOW ? V/Q Mismatching Diseased lungs may have marked mismatch between ventilation and perfusion. Some alveoli are relatively overventilated while others are relatively overperfused Even normal lungs have some degree of ventilation/perfusion mismatch;the upper zones are relatively overventilated while the lower zones are relatively overperfused & underventilated

Respiratory Structures in Brainstem : 

114 Respiratory Physiology Matter of WHY &HOW ? Respiratory Structures in Brainstem

Regulation of breathing : 

115 Respiratory Physiology Matter of WHY &HOW ? Regulation of breathing DRG stimulates inspiratory muscles, 12-15 times / minute VRG active in forced breathing Pontine respiration centre: finetuning of breathing / inhibits DRG Marieb, Human Anatomy & Physiology, 7th edition

Rhythmic Ventilation : 

116 Respiratory Physiology Matter of WHY &HOW ? Rhythmic Ventilation Starting inspiration Medullary respiratory center neurons are continuously active Center receives stimulation from receptors and simulation from parts of brain concerned with voluntary respiratory movements and emotion Combined input from all sources causes action potentials to stimulate respiratory muscles Increasing inspiration More and more neurons are activated Stopping inspiration Neurons stimulating also responsible for stopping inspiration and receive input from pontine group and stretch receptors in lungs. Inhibitory neurons activated and relaxation of respiratory muscles results in expiration.

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117 Respiratory Physiology Matter of WHY &HOW ?

Slide 118: 

118 Respiratory Physiology Matter of WHY &HOW ?

Factors that influence respiration : 

119 Respiratory Physiology Matter of WHY &HOW ? Factors that influence respiration Hypothalamus (emotions / pain) Cortex (voluntary control) Chemoreceptors: Central (in medulla oblongata): responds to CO2 ? CO2 passes blood brain barrier CO2 + H2O H2CO3 H+ + HCO3- H+ stimulates receptors ? breathing depth ? + rate ? Peripheral (in aortic / carotid bodies): responds when O2 < 60 mm Hg ? increase ventilation Responds to pH ? ? increase ventilation

Factors Influencing Respiration : 

Factors Influencing Respiration

Herring-Breuer Reflex : 

121 Respiratory Physiology Matter of WHY &HOW ? Herring-Breuer Reflex Limits the degree of inspiration and prevents overinflation of the lungs Infants Reflex plays a role in regulating basic rhythm of breathing and preventing overinflation of lungs Adults Reflex important only when tidal volume large as in exercise

5 Sensory Modifiers of Respiratory Center Activities : 

122 Respiratory Physiology Matter of WHY &HOW ? 5 Sensory Modifiers of Respiratory Center Activities Chemoreceptors are sensitive to: PCO2, PO2, or pH of blood or cerebrospinal fluid Baroreceptors in aortic or carotid sinuses: sensitive to changes in blood pressure

5 Sensory Modifiers of Respiratory Center Activities : 

123 Respiratory Physiology Matter of WHY &HOW ? 5 Sensory Modifiers of Respiratory Center Activities Stretch receptors: respond to changes in lung volume Irritating physical or chemical stimuli: in nasal cavity, larynx, or bronchial tree Other sensations including: pain changes in body temperature abnormal visceral sensations

Chemoreceptor Reflexes : 

124 Respiratory Physiology Matter of WHY &HOW ? Chemoreceptor Reflexes Respiratory centers are strongly influenced by chemoreceptor input from: * cranial nerve IX -The glossopharyngeal nerve: from carotid bodies stimulated by changes in blood pH or PO2 * cranial nerve X -The vagus nerve: from aortic bodies stimulated by changes in blood pH or PO2 * receptors that monitor cerebrospinal fluid- Are on ventrolateral surface of medulla oblongata Respond to PCO2 and pH of CSF

Slide 125: 

125 Respiratory Physiology Matter of WHY &HOW ? Thank you