Gas-exchange impairment: its correlation to lung mechanics in acute airway obstruction (studies on a rabbit asthma model).
A rabbit model was developed for the studies of ventilation/perfusion relationships (VA/Q) and thorax mechanics during bronchial provocation tests. Baseline data from 14 anaesthetized rabbits show a VA/Q distribution that is broader (less efficient VA/Q match) than that of lung-healthy humans, dogs and horses. Airway provocation was created by inhalation of ammonia, prostaglandin (PGE1) and methacholine bromide. Methacholine bromide was the only substance that triggered measurable VA/Q changes. Measurements 5 min after methacholine provocation showed markedly increased thorax resistance, widened VA/Q distribution and in some rabbits an increased shunt. Fifteen minutes after provocation that was still a broad VA/Q distribution and in several rabbits a further increase of shunt. Both thorax resistance and perfusion of regions with low VA/Q were reduced. Our results suggest a correlation between thorax resistance and perfusion of regions with low VA/Q. However, the slower normalization in VA/Q disturbance and the remaining or increased shunt suggests that factors other than airway resistance contribute to the gas-exchange impairment. These factors might be alveolar oedema, or mucus and oedema in the smallest airways.
Lagerstrand
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L
Department of Animal Research, Huddinge University Hospital, Stockholm, Sweden.
Hedenstierna
G
G
D000402:Airway Obstruction / Q000503:physiopathology*; D000641:Ammonia / Q000494:pharmacology; D000818:Animals; D001249:Asthma / Q000503:physiopathology*; D001980:Bronchi / Q000187:drug effects / Q000378:metabolism; D001985:Bronchial Provocation Tests; D004195:Disease Models, Animal; D006439:Hemodynamics; D008168:Lung / Q000503:physiopathology*; D008688:Methacholine Compounds / Q000494:pharmacology; D011458:Prostaglandins E / Q000494:pharmacology; D011659:Pulmonary Gas Exchange; D011817:Rabbits; D015656:Respiratory Mechanics; D014692:Ventilation-Perfusion Ratio
D008688:Methacholine Compounds; D011458:Prostaglandins E; D000641:Ammonia