medical training - physiology & pathophysiology - for internal use only
TRANSCRIPT
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Medical Training- Physiology & Pathophysiology -
For internal use only
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© WEINMANN GERÄTE FÜR MEDIZIN GMBH+CO.KG, Medical Training Physiology & Pathophysiology, June 2008 2
Objective of the Presentation
• This presentation on the physiology of the respiratory system gives participants an overview of of the anatomical structures required for normal respiration in a human being, the terminology used for respiratory mechanics and the normal values for a human subject.
• The area of pathophysiology covers known clinical pictures and indications for ventilation.
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Contents
• Respiratory physiology • Spontaneous breathing• Respiratory mechanics• Gas exchange• Pathophysiology and clinical pictures• Indications for ventilation• Summary
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Respiratory Physiology • Coverage of an organism‘s energy needs requires
– continuous supply of nutrients – oxygen (O2)
to obtain stored ATP (adenosine triphosphate) from cells.
• During the conversion CO2 and water are released.
• Prerequisites:– Functional respiratory drive and respiratory musculature– Intact gas exchange unit (lung parenchyma)– Sufficient O2 transport (blood circulation function).
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Spontaneous Breathing
• Spontaneous breathing is triggered by a reflex. • It is an unconscious process which – in contrast to other reflexes –
can be partly controlled by holding one‘s breath. • Stimulus to breathe is made up of the following
– increase of the CO2 level in the blood
– decrease in O2 level in the blood
– decrease of pH level in the blood
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Respiratory Mechanics• Intrapulmonary pressure
– Inspiration:• < atmospheric pressure• active process,
overcoming the elastic retraction force of the lungs– Expiration:
• > atmospheric pressure• passive process,
by means of elastic retraction force of the lungs
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Introduction and Brief Overview Ventilation/ Volume
Tidal Volume (TV) is the volume of air that is inhaled in one normal breath (about 500ml/at rest 6-8ml/kg)
Quelle: Schmidt, Thews, Lang, Physiologie des Menschen, Springer, 2000
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Lung Volumes
• Tidal Volume (TV): 500-800 ml• Total Capacity (TC): 6000 ml • Residual Volume (RV): 1200 ml
– Maximum Expiration• Vital Capacity (VC): approx. 5000 ml
– Difference between Total Capacity and Residual Volume• Inspiration Capacity (IC) : 2500 – 3500 ml
– Inspiration from resting end-expiratory position• Functional Residual Capacity (FRC) : 2300 ml
– Sum of Residual Volume and Expiratory Reserve Volume
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Resistance/ Compliance
Resistance: • Measurement of flow resistance of the respiratory system that must
be overcome during inspiration and expiration.
Compliance: • Measurement of the lungs‘ intrinsic elasticity• Describes the elastic properties of the respiratory system
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Resistance
• Measure for airways resistance = flow resistance• Defined by the pressure difference behavior between the beginning
and end of a conduit (therefore, between the atmosphere and the alveoli) and the gas volume that flows through the conduit per time unit (= flow)
• R = Δp/V [R] = 1 mbar/l/sec• In a healthy adult: 2 – 4 mbar/l/sec
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Compliance• Measure of the lungs‘expansibility• Describes the elastic properties of the respiratory apparatus• Defined as the ratio of volume change to the related pressure
change:• C = ΔV / Δp [C] = 1 ml/mbar• Depends on the elasticity of the pulmonary fiber network,
intrapulmonary fluid level and on surfactant activity.
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Surfactant
• Surface active agent • Substance which is active on the inner surface of the alveoli• Reduction of surface tension by a factor of 15 to 20• Decrease of “opening pressure” of small alveoli • Increase in lung compliance• Prevention of alveoli collapse
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Pressure-Volume Curve
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Respiration
• Gas exchange between organism and environment– external respiration (at the alveolar level)
– internal respiration (at the cellular level)
• O2 consumption: 3 – 5 ml/kgKG/min
• CO2 production: 3 ml/kgKG/min
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External Respiration
• O2 diffuses from the alveoli
into the blood and CO2 from the blood into the alveoli along the alveolar-capillary membrane
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Gas Exchange (External Respiration)
The gas exchange at the alveolar level depends on• Ventilation• Diffusion• Perfusion• Dead space ventilation• intrapulmonary right-left
shunt
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Partial Pressures Depending on Airway
pO2 (mmHg) pCO2 (mmHg)
Atmosphere 150-160 0
Inspired air 140-150 0
Alveolar air 100 40
Arterial blood 90 - 100 40
Gem. venous blood 40 45
Cells < 5 > 45
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Disruption of O2 Availability/Transport to Alveolar Level
• Decrease in O2 availability (CO2 enrichment)• Mechanical disorders
– Secrete accumulation– Swelling of mucus membranes (bronchial asthma, bronchitis)– Lengthening of exchange route (pulmonary edema)– Bronchial spasms– Foreign bodies– Tumor stenosis
• Disorder of Central Respiratory Control (head injury)• Respiratory mechanics disability caused by trauma to thorax• Failure of respiratory musculature (intoxication)
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Disruption of O2 Transport from Alveolar Level to Cellular O2 Supply
• Impaired pulmonary perfusion (emphysema, ARDS)• Heart failure• Lack of volume (bleeding, burns)• Impeded transport capacity of erythrocytes (intoxication)• Impaired O2 utilization – internal respiration (intoxication)
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Indications for Ventilation
• Ventilation disorders– Trauma to thorax– Injuries of the diaphragm
• Diffusion disorders– Pulmonary edema
• Central respiratory disorders– SHT
• Perfusion disorders– Pulmonary embolism, emphysema
• Disorders of distribution
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Summary
• Basic knowledge of anatomy is a prerequisite for understanding respiratory physiology.
• Basic knowledge of respiratory physiology facilitates the understanding of respiratory disorders.
• Understanding of processes in respiratory physiology and standard values make possible patient-adapted care in cases of respiratory disorders and indications for ventilation.