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Exercise 40
Respiratory Physiology
1
Processes of respiration
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Pulmonary ventilation
External respiration
Transport of respiratory gases
Internal respiration or cellular
respiration
Mechanisms of respiration
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Pulmonary ventilation
 Inspiration
 Expiration
 Respiratory muscles
• Diaphragm
• External intercostal
• Others
Mechanisms of respiration
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4
Steps of ventilation
 Contraction of diaphragm and
external intercostal muscles
 Increase of thoracic volume
 Expansion of the pleural cavities and
lungs
 Decrease of lung pressure below
atmospheric pressure
Mechanisms of respiration
 Inspiration
 Lung
pressure becomes equal to
atmospheric pressure
 Air stops to flow inside
 Relaxation of respiratory muscles
 Recoiling of the lung tissue
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Mechanisms of respiration
 Decrease
of intrathoracic and
intrapulmonary volumes
 Increase of pulmonary pressure
 Expiration
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Mechanisms of respiration
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Pneumothorax it is the entry of air into
the pleural cavity
 It breaks the fluid bond between the
visceral and parietal pleura
 It will cause the lung to collapse –
atelectasis
Respiratory volumes and
capacities
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Spirometry
Tidal volume (TV)
 It is the amount of air inspired or
expired with each breath under
resting conditions
 500 ml
Respiratory volumes and
capacities
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9
Inspiratory reserve volume (IRV)
 It is the amount of air that can be
forcefully inspired after a normal tidal
inspiration
 3100 ml
Respiratory volumes and
capacities
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10
Expiratory reserve volume (ERV)
 It is the amount of air that can be
forcefully expired after a normal tidal
expiration
 1200 ml
 It is reduced in conditions in which
the elasticity of the lungs is
decreased
Respiratory volumes and
capacities
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11
Vital capacity (VC)
 It id the maximum amount of air that
can be expired after a maximal
inspiration
 4800 ml
 VC = TV + IRV + ERV
Respiratory volumes and
capacities
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Residual volume (RV)
 It is the amount of air that remains in
the lung after a ERV
 1200 ml
Respiratory volumes and
capacities
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13
Functional residual capacity (FRC)
 It is the amount of air that remains in
the lung after a quiet respiratory
cycle
 2400 ml
 FRC = ERV+RV
Respiratory volumes and
capacities
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Total lung capacity (TLC)
 It is the total volume of the lungs
 6000 ml
 TLC = VC+RV
Respiratory volumes and
capacities
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Respiratory volumes and
capacities
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Nonrecording spirometer
 Handheld dry spirometer
• Measures only expired air
 Wet spirometer
• Measures only expired air
Recording spirometer
 Measures inspired and expired air
Pulmonary disorders
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Obstructive
 Bronchitis
 Asthma
Restrictive
 Tuberculosis
 Poliomyelitis
Respiratory volumes and
capacities
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18
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
Respiratory volumes and
capacities
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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
Respiratory rate and depth
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Factors that changes the RR
 Exercise
 Coughing
 Waking
 Talking
 Laughing, etc
Respiratory sounds
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Bronchial sounds
 Heard below the larynx
Vesicular sounds
 Air filling the alveolar sacs
 Heard over the chest
Crepitation (crackles)
Wheezing – a whistling sound
Role of respiratory system in
acid-base balance of blood
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Blood pH
 7.35-7.45
 Carbonic acid-bicarbonate buffer
• The main body buffer
Acid-base imbalance
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Alkalosis
 Blood pH above 7.45
 Respiratory or metabolic
Acidosis
 Blood pH bellow 7.35
 Respiratory or metabolic