Exercise 40

Respiratory Physiology

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Processes of respiration

Pulmonary ventilation External respiration Transport of respiratory gases Internal respiration or cellular

respiration

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Mechanisms of respiration

Pulmonary ventilationInspirationExpirationRespiratory muscles

• Diaphragm• External intercostal• Others

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Mechanisms of respiration

Steps of ventilationContraction of diaphragm and

external intercostal musclesIncrease of thoracic volumeExpansion of the pleural cavities and

lungsDecrease of lung pressure below

atmospheric pressure

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Mechanisms of respiration

InspirationLung pressure becomes equal to

atmospheric pressureAir stops to flow insideRelaxation of respiratory musclesRecoiling of the lung tissue

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Mechanisms of respiration

Decrease of intrathoracic and intrapulmonary volumes

Increase of pulmonary pressureExpiration

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Mechanisms of respiration

Pneumothorax it is the entry of air into the pleural cavityIt breaks the fluid bond between the

visceral and parietal pleuraIt will cause the lung to collapse –

atelectasis

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Respiratory volumes and capacities

Spirometry Tidal volume (TV)

It is the amount of air inspired or expired with each breath under resting conditions

500 ml

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Respiratory volumes and capacities

Inspiratory reserve volume (IRV)It is the amount of air that can be

forcefully inspired after a normal tidal inspiration

3100 ml

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Respiratory volumes and capacities

Expiratory reserve volume (ERV)It is the amount of air that can be

forcefully expired after a normal tidal expiration

1200 mlIt is reduced in conditions in which

the elasticity of the lungs is decreased

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Respiratory volumes and capacities

Vital capacity (VC)It id the maximum amount of air that

can be expired after a maximal inspiration

4800 mlVC = TV + IRV + ERV

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Respiratory volumes and capacities

Residual volume (RV)It is the amount of air that remains in

the lung after a ERV1200 ml

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Respiratory volumes and capacities

Functional residual capacity (FRC)It is the amount of air that remains in

the lung after a quiet respiratory cycle

2400 mlFRC = ERV+RV

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Respiratory volumes and capacities

Total lung capacity (TLC)It is the total volume of the lungs6000 mlTLC = VC+RV

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Respiratory volumes and capacities

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Respiratory volumes and capacities

Nonrecording spirometerHandheld dry spirometer

• Measures only expired airWet spirometer

• Measures only expired air Recording spirometer

Measures inspired and expired air

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Pulmonary disorders

Obstructive BronchitisAsthma

RestrictiveTuberculosisPoliomyelitis

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Respiratory volumes and capacities

Forced vital capacity (FVC)It is the amount of air expired after a

deep inspiration and a forced and quick expiration

Reduced in restrictive pulmonary diseases

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Respiratory volumes and capacities

Forced expiratory volume measurement (FEV1%)It is the percentage of vital capacity

that is exhaled during specific intervals of time

It is reduced in obstructive diseases

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Respiratory rate and depth

Factors that changes the RRExercise CoughingWakingTalkingLaughing, etc

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Respiratory sounds

Bronchial soundsHeard below the larynx

Vesicular soundsAir filling the alveolar sacsHeard over the chest

Crepitation (crackles) Wheezing – a whistling sound

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Role of respiratory system in acid-base balance of blood

Blood pH7.35-7.45Carbonic acid-bicarbonate buffer

• The main body buffer

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Acid-base imbalance

AlkalosisBlood pH above 7.45Respiratory or metabolic

AcidosisBlood pH bellow 7.35Respiratory or metabolic

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