physiology & pathophysiology of
respiration, mvdr i uhrikova phd
physiology – what is essential for
breathing?
1.pulmonary ventilation (athmosphere – alveoli)
2.diffusion (alveoli – blood)
3.transport of gases (blood – tissues)
4.(regulation)
what is essential for breathing
1. pulmonary ventilation (athmosphere – alveoli)
–
–
–
–
–
–
muscles
pressure in thoracic cavity
lung compliance
thorax compliance
pulmonary volume
alveolar ventilation
impaired pulmonary ventilation
PLEURAL EFFUSION
• normally 0.1-0.3 ml/kg of fluid
• communication between left & right pleural space (?)
• inflammatory vs non-inflammatory effusion
impaired pulmonary ventilation
PLEURAL EFFUSION
• normally 0.1-0.3 ml/kg of fluid
• communication between left & right pleural space (?)
• inflammatory vs non-inflammatory effusion
impaired pulmonary ventilation
PLEURAL EFFUSION
• normally 0.1-0.3 ml/kg of fluid
• communication between left & right pleural space (?)
• inflammatory vs non-inflammatory effusion
impaired pulmonary ventilation
PLEURAL EFFUSION
• normally 0.1-0.3 ml/kg of fluid
• communication between left & right pleural space (?)
• inflammatory vs non-inflammatory effusion
impaired pulmonary ventilation
PLEURAL EFFUSION
• normally 0.1-0.3 ml/kg of fluid
• communication between left & right pleural space (?)
• inflammatory vs non-inflammatory effusion
impaired pulmonary ventilation
PLEURAL EFFUSION
• transudate
• modified transudate
•
•
•
•
•
¼ Hct
hemorrhage
Bie>Bis
bile
milky
chyle
septic exudate (pyothorax)
aseptic exudate (neoplasia, FIP)
what is essential for breathing
2. diffusion (alveoli - blood)
–
–
–
–
composition of gases in alveoli
diffusion capacity of the alveolar membrane
pressure of blood in the pulmonary vessels
amount of the blood in systemic vs pulmonary
circulation
– distribution of the blood according to ventilation
impaired diffusion
PULMONARY EMBOLISM
• fq of small emboli probably high
• arise from deep vein thrombosis of the lower
extremities
• mechanism in thrombi formation:
– stasis of blood
– alteration in coagulation
– alteration of vessel wall
impaired diffusion
PULMONARY EMBOLISM
• most commonly cardiomyopathy in cats
• heartworm disease in dogs
impaired diffusion
PULMONARY EMBOLISM
• pulmonary hemodynamics:
thrombi + reflective vasoconstriction
increase in pulmonary artery pressure
right-ventricle heart failure
(pulmonary oedema)
obstruction
of at least
½ of
pulmonary
circulation
impaired diffusion
PULMONARY EMBOLISM
• pulmonary mechanics:
decreased alveolar pCO2
bronchoconstriction + alveolar duct constriciton
increase in pulmonary resistance
impaired diffusion
PULMONARY EMBOLISM
• gas exchange:
ventilation-perfusion inhomogeneity
increased dead space
impaired diffusion
PULMONARY EDEMA
• accumulation of fluid in extravascular tissue
• two phases
– interstitial edema
– alveolar edema
alveoli
impaired diffusion
PULMONARY EDEMA
• interstitial edema increases alveolar-capillary
thickness by 15-20 %
- fluid moves from gas-exchange site to perivascular
site – remains unaffected
unless
- when interstitial space expands >50 % alveolar
edema occurs
impaired diffusion
PULMONARY EDEMA
• alveolar edema
– leakage site: junction between alveoli & small
alveolar ducts OR epithelial tight junctions
impaired diffusion
PULMONARY EDEMA
• decrease in lung compliance
• decrease in pO2
• further progress in  lung compliance
impaired diffusion
PULMONARY EDEMA
• most commonly
left sided heart failure
( hydrostatic pressure)
may be without alveolar edema due to
adjustment of the lymphatic drainage
impaired diffusion
PULMONARY EDEMA
• most commonly
excessive i.v. fluids, acute renal failure
( hydrostatic pressure
 permeability)
toxins (endotoxin, exotoxins)
( permeability)
lymphatic drainage
what is essential for breathing
3. transport (blood - tissues)
– haemoglobin content
what is essential for breathing
3. transport (blood - tissues)
what is essential for breathing
4. regulation
– respiratory center
– peripheral receptors
impaired regulation
IVERMECTIN TOXICOSIS
• border collie, australian shepherd, collies, longhaired whipet, etc.
• ivermectin cross hematoencephalic barrier
• stimulate GABA release
• ataxy, mydriasis, hypersalivation, vomiting,
blindness, tremor, seizures, bradykardia, bradypnoe
diagnostics
•
•
•
•
pulse oxymetry
arterial blood gases
capnography
plethysmograph
thank you for attention
references
Cohn LA, Reinero CR. Respiratory defense in health and disease. Vet Clin North
Am Small Anim Pract 2007; 37: 845-860.
Dunlop RH, Malbert CH. Veterinary patophysiology. Blackwell publishing 2004,
Iowa, USA.
Epstein SE. Exudative pleural disease in small animals. Vet Clin Small Anim
2014; 44:161-180.
Guyton AC, Hall JE. Textbook of medical physiology. Elsevier 2006,
Pennsylvania, USA.
Hoffman A. Airway physiology and clinical testing. Vet Clin North Am Small
Anim Pract 2007; 37: 829-843.