respiratory physiology - a
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Respiratory Physiology - ATRANSCRIPT
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RESPIRATORY RESPIRATORY PHYSIOLOGYPHYSIOLOGY
Agaton T. Panopio, Jr., MD, MHPEdAgaton T. Panopio, Jr., MD, MHPEd
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Lung PressuresLung Pressures
Intrathoracic PressureIntrathoracic Pressure
Pressure within the pleural cavityPressure within the pleural cavity
Intrapulmonic PressureIntrapulmonic Pressure
Pressure within the pulmonary alveoliPressure within the pulmonary alveoli
Transpulmonary PressureTranspulmonary Pressure
Pressure across lung parenchymaPressure across lung parenchyma
Transthoracic PressureTransthoracic Pressure
Pressure across the chest wallPressure across the chest wall
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Normally subatmospheric at rest, due to Normally subatmospheric at rest, due to inward elastic recoil of the lungs and inward elastic recoil of the lungs and outward elastic recoil of chest walloutward elastic recoil of chest wallPressure is more negative at upper thorax Pressure is more negative at upper thorax
due to gravity and posturedue to gravity and postureBecomes more negative during quiet Becomes more negative during quiet inspiration, less negative during quiet inspiration, less negative during quiet expirationexpiration
Lung PressuresLung Pressures
Intrathoracic (Intrapleural) Pressure Intrathoracic (Intrapleural) Pressure
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Initially equal to atmospheric pressure Initially equal to atmospheric pressure at restat restDuring inspiration, it becomes negative, During inspiration, it becomes negative, causing entry of air into alveolicausing entry of air into alveoliAlveolar pressure returns to zero and air Alveolar pressure returns to zero and air flow stopsflow stopsAt expiration, alveolar wall recoils, alveolar At expiration, alveolar wall recoils, alveolar gas is compressed, and pressure rises gas is compressed, and pressure rises above above atmospheric pressure atmospheric pressure
Lung PressuresLung Pressures
Intrapulmonic (Alveolar) PressureIntrapulmonic (Alveolar) Pressure
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During inspiration, as intrathoracic During inspiration, as intrathoracic pressure becomes more negative, pressure becomes more negative, transpulmonary pressure increases transpulmonary pressure increases and and alveoli expandalveoli expand
During expiration, as intrathoracic pressure During expiration, as intrathoracic pressure becomes less negative, transpulmonary becomes less negative, transpulmonary pressure decreases and alveoli recoilpressure decreases and alveoli recoil
Lung PressuresLung Pressures
Transpulmonary (Transmural) PressureTranspulmonary (Transmural) Pressure
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A measure of the elastic recoil of the A measure of the elastic recoil of the thoraxthorax
Lung PressuresLung Pressures
Transthoracic PressureTransthoracic Pressure
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Quiet InspirationQuiet Inspiration
Inspiratory muscles contractInspiratory muscles contract
Chest wall expandsChest wall expands
Thoracic volume increasesThoracic volume increases
Intrathoracic pressure becomes more negativeIntrathoracic pressure becomes more negative
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Quiet InspirationQuiet Inspiration
Alveolar transmural pressure gradient increasesAlveolar transmural pressure gradient increases
Alveoli expandAlveoli expand
Alveolar pressure falls below atmospheric Alveolar pressure falls below atmospheric pressurepressure
Air flows into the alveoliAir flows into the alveoli
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Quiet ExpirationQuiet Expiration
Inspiratory muscles recoilInspiratory muscles recoil
Thoracic volume decreasesThoracic volume decreases
Intrathoracic pressure becomes less negativeIntrathoracic pressure becomes less negative
Alveolar transmural pressure gradient Alveolar transmural pressure gradient decreasesdecreases
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Quiet ExpirationQuiet Expiration
Increased alveolar elastic recoilIncreased alveolar elastic recoil
Alveolar pressure rises above Alveolar pressure rises above atmospheric pressureatmospheric pressure
Air flows out of the alveoliAir flows out of the alveoli
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Amount of air that moves in and out of Amount of air that moves in and out of the lungs during normal resting the lungs during normal resting ventilationventilation
Usually 500-600 mlUsually 500-600 ml
Lung Volumes and CapacitiesLung Volumes and Capacities
Tidal VolumeTidal Volume
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The amount of air that can be inhaled The amount of air that can be inhaled maximally after a normal inhalationmaximally after a normal inhalation
About 2.5 litersAbout 2.5 liters
Lung Volumes and CapacitiesLung Volumes and Capacities
Inspiratory Reserve VolumeInspiratory Reserve Volume
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The amount of air than can be exhaled The amount of air than can be exhaled maximally after a normal maximally after a normal
exhalationexhalation
About 1.5 litersAbout 1.5 liters
Lung Volumes and CapacitiesLung Volumes and Capacities
Expiratory Reserve VolumeExpiratory Reserve Volume
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Amount of air that remains in the lungs Amount of air that remains in the lungs after a maximal exhalationafter a maximal exhalation
About 1.5 litersAbout 1.5 liters
Lung Volumes and CapacitiesLung Volumes and Capacities
Residual VolumeResidual Volume
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The amount of air that can be inhaled The amount of air that can be inhaled maximally after a normal maximally after a normal
exhalationexhalation
About 3 litersAbout 3 liters
Lung Volumes and CapacitiesLung Volumes and Capacities
Inspiratory CapacityInspiratory Capacity
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Amount of air that remains in the lungs Amount of air that remains in the lungs after a normal exhalationafter a normal exhalation
About 3 litersAbout 3 liters
Lung Volumes and CapacitiesLung Volumes and Capacities
Functional Residual CapacityFunctional Residual Capacity
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The maximum volume of air that can be The maximum volume of air that can be exhaled after the deepest possible exhaled after the deepest possible inspirationinspiration
About 4.5 litersAbout 4.5 liters
Lung Volumes and CapacitiesLung Volumes and Capacities
Vital CapacityVital Capacity
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Represents the total volume of air in the Represents the total volume of air in the lungs when maximally inflatedlungs when maximally inflated
About 6 litersAbout 6 liters
Lung Volumes and CapacitiesLung Volumes and Capacities
Total Lung CapacityTotal Lung Capacity
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Measurement of Lung Measurement of Lung Volumes and CapacitiesVolumes and Capacities
SpirometrySpirometry
Measures TV, IRV, ERV and VCMeasures TV, IRV, ERV and VC
Measurement of FRC, RV and TLCMeasurement of FRC, RV and TLC
Closed circuit method (helium dilution)Closed circuit method (helium dilution)
Open circuit method (nitrogen washout)Open circuit method (nitrogen washout)
Body plethysmographyBody plethysmography
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HELIUM DILUTION
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HELIUM DILUTION
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NITROGEN WASHOUT
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NITROGEN WASHOUT
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Dead Air SpaceDead Air Space
Anatomic Dead Air SpaceAnatomic Dead Air Space
Volume of air in the non-gas Volume of air in the non-gas exchanging airways (conducting exchanging airways (conducting portion)portion)
About 150 mlAbout 150 ml
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The portion of each inspiration that does The portion of each inspiration that does not equilibrate with gas in not equilibrate with gas in
pulmonary pulmonary capillary bloodcapillary blood
Dead Air SpaceDead Air Space
Physiologic Dead Air SpacePhysiologic Dead Air Space
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The air in alveoli not perfused by The air in alveoli not perfused by pulmonary capillary bloodpulmonary capillary blood
The difference between physiologic and The difference between physiologic and anatomic dead air spaceanatomic dead air space
Dead Air SpaceDead Air Space
Alveolar Dead Air SpaceAlveolar Dead Air Space
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Factors Affecting Anatomic Factors Affecting Anatomic Dead Air SpaceDead Air Space
AgeAgeAnatomic dead air space increases with age Anatomic dead air space increases with age due to loss of lung elasticitydue to loss of lung elasticity
Position of the headPosition of the headExtension of the neck increases dead air spaceExtension of the neck increases dead air space
DrugsDrugsBronchodilators increase dead air spaceBronchodilators increase dead air space
Snorkel breathingSnorkel breathingSnorkel increases dead air spaceSnorkel increases dead air space
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Factors Affecting Alveolar Factors Affecting Alveolar Dead Air SpaceDead Air Space
Ventilation-Perfusion RelationshipsVentilation-Perfusion Relationships
An increase in ventilation without a An increase in ventilation without a corresponding increase in perfusion corresponding increase in perfusion
increases alveolar dead air spaceincreases alveolar dead air space
An increase in perfusion without a An increase in perfusion without a corresponding increase in ventilation corresponding increase in ventilation
decreases alveolar dead air spacedecreases alveolar dead air space
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ComplianceCompliance
The volume of gas that can move into the The volume of gas that can move into the lungs for every unit of pressure changelungs for every unit of pressure change
It is a measure of elasticity of the It is a measure of elasticity of the bronchopulmonary systembronchopulmonary system
Determinants include:Determinants include:
Surface tensionSurface tension
Law of LaplaceLaw of Laplace
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ElastanceElastance
The reciprocal of complianceThe reciprocal of compliance
The tendency for the bronchopulmonary The tendency for the bronchopulmonary system to oppose stretchsystem to oppose stretch
The ability of the bronchopulmonary The ability of the bronchopulmonary system to return to its original position system to return to its original position after removal of a distending forceafter removal of a distending force
It is a measure of recoilIt is a measure of recoil
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Work of BreathingWork of Breathing
Mechanical WorkMechanical Work
Expressed in pressure change (cm Expressed in pressure change (cm water) x volume change water) x volume change (liter)(liter)
Metabolic WorkMetabolic Work
Refers to additional oxygen Refers to additional oxygen consumption x mechanical consumption x mechanical equivalent for oxygen consumptionequivalent for oxygen consumption
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Dynamic Lung VolumesDynamic Lung Volumes
Maximal Voluntary VentilationMaximal Voluntary Ventilation
Maximum volume of a gas that can be Maximum volume of a gas that can be ventilated during a given periodventilated during a given period
Forced Expiratory Vital CapacityForced Expiratory Vital Capacity
Maximum volume of gas that can be forcibly Maximum volume of gas that can be forcibly and rapidly exhaledand rapidly exhaled
Forced Expiratory VolumeForced Expiratory Volume
Volume of gas exhaled at a specified timeVolume of gas exhaled at a specified time
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T H A N K Y O U !