medical training - physiology & pathophysiology - for internal use only

Medical Training- Physiology & Pathophysiology -

For internal use only

© 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.


Contents

• Respiratory physiology • Spontaneous breathing• Respiratory mechanics• Gas exchange• Pathophysiology and clinical pictures• Indications for ventilation• Summary


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).


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


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


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


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


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


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


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.


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


Pressure-Volume Curve


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


External Respiration

• O2 diffuses from the alveoli

into the blood and CO2 from the blood into the alveoli along the alveolar-capillary membrane


Gas Exchange (External Respiration)

The gas exchange at the alveolar level depends on• Ventilation• Diffusion• Perfusion• Dead space ventilation• intrapulmonary right-left

shunt


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


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)


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)


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


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.

medical training - physiology & pathophysiology - for internal use only

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