Physiology department1
Respiratory system.
Physiology department2
Questions for the oral exam
̶ A22: Hypoxia and ischemia
̶ A25: Lung ventilation, volumes, measurement
̶ A26: Dead space, measurement
̶ A27: Resistance of airways, measurement
̶ A28: Maximal respiratory flow - volume curve (spirogram)
̶ A45: Alveolar surface tension. Surfactant
̶ A46: Compliance of lungs. Respiratory work. Pneumothorax
̶ A47: Composition of atmospheric and alveolar air. Gas exchange in lungs and tissues
̶ A48: Transport of O2. Oxygen - haemoglobin dissociation curve. Transport of CO2
̶ A49: Regulation of ventilation
̶ A50: Respiratory responses to irritants
Physiology department3
A22: Hypoxia and ischemia
̶ Hypoxia is a general name for a lack of oxygen in the body or
individual tissues
̶ Ischemia, meaning insufficient blood flow to a tissue, can also
result in hypoxia
̶ The most common types of hypoxia:
̶ Hypoxic
̶ Transport (anemic)
̶ Ischemic (stagnation)
̶ Histotoxic
O2O2
O2O2
ERY ERY
ERY: ♀ 3.4 – 4.4 * 1012/l
♂ 4.5 – 5.5 * 1012/l
pO2: 21kPa
4
A22: Hypoxia and ischemia
̶ Hypoxic:
̶ physiological: stay at higher altitudes
̶ ↓ pO2; N Ery
̶ pathological: hypoventilation during lung or neuromuscular diseases
̶ ↓ ventilation; N pO2; N Ery
̶ Transport (anemic):
̶ reduced transport capacity of blood for oxygen (anemia, blood loss)
̶ N pO2; ↓ Ery/Hb
̶ Ischemic (stagnation):
̶ restricted blood flow to tissue (heart failure, obstruction of an artery)
̶ N pO2; N Ery
̶ Histotoxic
̶ cells are unable to utilize oxygen (cyanide poisoning)
̶ N pO2; N Ery
Physiology department5
A25: Lung ventilation, volumes, measurement
̶ Ventilation, or breathing, is the movement of air through the
conducting passages between the atmosphere and the lungs
̶ Principle: determination the air flow velocity from the
measured pressure differences between the inner and outer
spirometer membranes, the volumes being calculated
(PowerLab spirometry)
Physiology department6
A25: Lung ventilation, volumes, measurement
̶ Tidal volume (TV) – the volume of air that enters the lungs during each inspiration (or the volume that is exhaled during every expiration).
̶ Inspiratory reserve volume (IRV) – the maximal amount of additional air that can be drawn into the lungs by determined effort after a normal inspiration at rest.
̶ Expiratory reserve volume (ERV) – the additional amount of air that can be exhaled from the lungs by determined effort after a normal expiration.
̶ Residual volume (RV) – the volume of air still remaining in the lungs after the most forcible expiration possible.
V [l]
Vt (0,5 l)
IRV (2,5 l)
ERV (1,5 l)
RV (1,5 l)
Physiology department7
A25: Lung ventilation, volumes, measurement
Lung capacity:
̶ VC = VT + IRV + ERV
̶ TLC = VC + RV
̶ FRC = ERV + RV
̶ IC = IRV + VT
̶ EC = ERV + VT
Vt (0,5 l)
IRV (2,5 l)
ERV (1,5 l)
RV (1,5 l)
V [l]
Dynamic lung volumes:
̶ VE
̶ MMV
Physiology department8
A25: Lung ventilation, volumes, measurement
Dynamic lung volumes
V [l]
Time [s]
FVCRV
1 s
FEV1
―FVC – the maximum volume of air that can be exhaled
after maximum inhale
―FEV1 – the volume of air exhaled with the greatest
effort in 1 second after maximum inhale
―FEV1/FVC (%) – Tiffeneau index – around 0,8 (80 %)
Physiology department9
A25: Lung ventilation, volumes, measurement
1 s
V [l]
Time [s] 1 s
V [l]
Time [s]
FEV1
FEV1
FVC > FVC
Obstruction lung disease
(FVC=N; FEV1=↓)
― tracheal stenosis
― astma bronchiale
― CHOPN
― tumor
Restrictive lung disease
(FVC=↓; FEV1=N)
Pulmonarzy etiology
― pulmonary fibrosis
― lung resection
― pulmonary edema
― pneumonia
Extrapulmonary etiology
― ascites
― kyphoscoliosis
― burns
― high diaphragm condition
Physiology department10
A25: Lung ventilation, volumes, measurement
c=
𝑛
𝑉
V1
c1
V2=RV+V1
c2
V1× 𝑐1 = (𝑅𝑉 + 𝑉1) ×c2
𝑅𝑉 =
𝑉1 × 𝑐1
𝑐2
− 𝑉1
Helium dilution method – residual volume
Physiology department11
A28: Maximal respiratory flow - volume
curve (spirogram)
PEF
MEF25%
MEF50%
MEF75%
TLC
IRV Vt ERV RV
IRC
VC
FRC
RV
• PEF – peek expiratory flow; the highest
speed of air flow at peak of exhale
• MEF – maximum expiratory flow rates at
different FVC levels, which is still to be
exhaled (75 %, 50 % and 25 % of FVC)
Principle: the measurement of the air
flow velocity according to the speed of the
turbine and the volumes are calculated
(Cosmed).
Physiology department12
A26: Dead space, measurement
Physiology department13
A26: Dead space, measurement
Physiology department14
A27: Resistance of airways, measurement
Pneumotachograph:
―tubes of the same diameter, parallel arranged
―measures the differences in air pressure at the beginning and
end of the pneumotachograph in proportion to the velocity of
the inhaled or exhaled air
p atm alv p
p d
P P P P
V
R R
− −
= =
=p p atmP P P −
=alv alv atmP P P −
1alv
d p
p
P
R R
P
 
=  −   
⩒=
Δ𝑃
𝑅
Physiology department15
A45: Alveolar surface tension. Surfactant
― pneumocytes typ II
― reduces the surface tension depending on the size of the
alveolus
― increases lung compliance, reduces breathing work
The Laplace law (in constant tension):
the alveolus with bigger radius has lower pressure
→ the air would move from a smaller alveolus to a bigger one
→ collapse of smaller alveoli
r
T
P
2
=
Physiology department16
A46: Compliance of lungs. Respiratory
work. Pneumothorax
parietal pleura
visceral pleura
pleural fluid
pleural pressure
alveolar pressure
Physiology department17
A46: Compliance of lungs. Respiratory
work. Pneumothorax
̶ According to etiology:
̶ traumatic pneumothorax (due to an injury) occurs if the chest wall is perforated or during an injury of the esophagus, bronchi, and
during rib fractures.
̶ spontaneous pneumothorax
̶ primary idiopathic pneumothorax (without any known cause) may occur in tall healthy young men with an incidence of
pneumothoraxes in the family,
̶ secondary pneumothorax arises as a consequence of lung diseases (such as COPD or cystic fibrosis),
̶ iatrogenic pneumothorax (due to medical procedures) occurs during invasive medical examinations such as transparietal
aspiration biopsy, subclavian vein catheterization, or mechanical ventilation with positive pressure.
̶ artificially induced (deliberate) pneumothorax is used during thoracoscopy, an endoscopic examination the thoracic cavity.
̶ According to the communication of the pleural space with its surroundings
̶ open pneumothorax (when the hole in the pleural space remains open, the air in the pleural cavity moves back and forth with
each breath of the patient)
̶ closed pneumothorax (when a small opening through which air enters the pleural cavity closes)
̶ valvular pneumothorax (the tissue of the lungs or the chest wall covers the hole in such a way that a valve emerges, this valve
allows air to flow inside during inspiration, but it prevents the air from leaving the pleural cavity during exhalation).
Physiology department18
A46: Compliance of lungs. Respiratory
work. Pneumothorax
Respiratory system resistance
̶ Elastic resistance:
̶ elastic fibers
̶ alveolar surface tension
̶ Nonelastic resistance:
̶ viskose resistance
̶ airway resistance
Respiratory work:
̶ Elastic
̶ Viskose
̶ Work of airway resistance
Physiology department19
A46: Compliance of lungs. Respiratory
work. Pneumothorax
V (l)
Pt (kPa)
TLC
RV
Vt
Pt: Patm and Ppl Pt: Palv and Ppl
Pt: Patm and Palv
Physiology department20
A46: Compliance of lungs. Respiratory
work. Pneumothorax
V (l)
Pt (kPa)
TLC
RV
Vt
Pt (kPa)
V (l)
Respiratory work:
1 – elastic
2 – viscos
3 – airway resistance
21
A47: Composition of atmospheric and alveolar air.
Gas exchange in lungs and tissues.
BAROMETRIC PRESSURE IN SEA LEVEL
1 atmosphere = 760 mm Hg
1 kPa = 7,5 mm Hg (torr)
O2 20.95 % FO2  0,21
N2 78.09 % FN2  0,78
CO2 0.03 % FCO2  0,0004
PO2 = 760 x 0,21 = ~160 mm Hg
PN2 = 760 x 0,78 = ~593 mm Hg
PCO2 = 760 x 0,0004 = ~ 0,3 mm Hg
PARTIAL PRESSURE OF DRY AIR IN SEA LEVEL
COMPOSITION OF DRY ATMOSPHERIC AIR
Physiology department22
A47: Composition of atmospheric and alveolar air.
Gas exchange in lungs and tissues.
Physiology department23
A48: Transport of O2. Oxygen - haemoglobin
dissociation curve. Transport of CO2
O2 is transported in two forms :
― physically dissolved(1%)
― in chemical bond with Hb (99%)
― Fetal hemoglobin(2α, 2)
― Methemoglobin (Fe3+)
― Carboxyhemoglobin (CO)
― Carbaminohemoglobin (CO2)
― Oxyhemoglobin (O2)
― Deoxyhemoglobin (without any gases)
Physiology department24
A48: Transport of O2. Oxygen - haemoglobin
dissociation curve. Transport of CO2
Dissociation curve of Hb is influenced by:
― pH of blood
― pCO2 of blood
― Temperature
― Concentration of 2,3 - BPG
Physiology department25
A48: Transport of O2. Oxygen - haemoglobin
dissociation curve. Transport of CO2
CO2 is transported in next forms :
― physically dissolved(5 %)
― in the form of bicarbonate anions (85%)
― in chemical bond with Hb (10%)
CO2 + H2O H2CO3
KAH
H+ + Hb
HCO3
-
Cl-
CO2
H+ + HCO3
- CO2 + H2OHb H2CO3
KAH
Cl-
CO2
Physiology department26
A49: Regulation of ventilation
Physiology department27
A49: Regulation of ventilation
Physiology department28
A49: Regulation of ventilation
Physiology department29
A49: Regulation of ventilation
30
A50: Respiratory responses to irritants
The lungs are protected from damage by:
̶ presence of hair (vibrissae) in the nasal cavity (traps dust particles)
̶ presence of ciliary epithelium covered with mucus (cilia moving mucus in one direction into
the pharynx)
̶ pulmonary alveolar macrophages
̶ presence of antibodies in bronchial secretion (IgA)
Reflexes:
̶ Herring-Breuer reflexes (inflation/deflation)
̶ Sneeze reflex
̶ Cough reflex
̶ Hiccup
̶ Yawn
31
A50: Respiratory responses to irritants
Cough Reflex Sneeze Reflex Hiccup
Cough is an expulsive reflex that protects the
lungs and respiratory passage from foreign
bodies.
Causes of cough:
― Irritants-smokes, fumes, dusts, etc.
― Diseased conditions like COPD, tumors of
thorax, etc.
Pathway for cough reflex:
― Receptors in nose, paranasal sinuses,
pharynx, trachea, pleura, diaphragm,
perichondrium, stomach, ex.auditory canal
and tymphanic membrane
― V,IX,X cranial nerves and phrenic nerves
― medulla
― X cranial nerve, phrenic nerve, spinal
motor nerve
― primary and accessory respiratory
muscles
Sneeze is defined as the involuntary
expulsion of air containing irritants from nose.
Causes of sneeze:
― Irritation of nasal mucosa
― Excess fluid in airway
Pathway for sneeze reflex:
― Olfactory receptors or V cranial nerve
endings
― I and V cranial nerve
― medulla – nucleus solitarious and reticular
formation
― V, VII, IX, X cranial nerves and intercostal
muscles
― pharyngeal, tracheal and respiratory
muscles
Hiccup is spasmodic contraction of the
diaphragm which causes a sudden intake of
breath that is involuntarily cut off by closure of
the glottis, thus producing a characteristic
sound.
Causes of hiccup:
― Eating too fast or too much
― Strokes, brain tumors, damage to the
vagus or phrenic nerve
― Anxiety and stress
Pathway for sneeze reflex:
― Phrenic, vagus, and sympathetic nerves
― Midbrain
― Motor fibers of phrenic nerve and
accessory nerves
― Diaphragm and intercostal muscles
Physiology department32
Herring-Breuer reflexes (inflation/deflation)
̶ a. keeps the lungs from over-inflating with inspired air
̶ pulmonary stretch R – vagus nerve – medulla – inhibition of inspiration and initiation of
expiration
̶ b. serves to shorten exhalation when the lung is deflated
̶ pulmonary stretch R – vagus nerve – the pontine center
A50: Respiratory responses to irritants