Claude Veriter

An improved porcine model of stable methacholine-induced bronchospasm

AbstractnObjective. To validate an animal model replicating the pathophysiological characteristics of severe induced bronchospasm observed in humans, with a high level of stability permitting measurements such as the assessment of ventilation-perfusion relationships with the multiple inert gas elimination technique.nDesign and setting. Experimental study in an animal research laboratory.nSubjects. 13 piglets (age 3–4xa0months) were studied and 7 underwent the complete protocolnInterventions. The animals were anesthetized and paralyzed. Mechanical ventilation was initiated in a volume-controlled mode. Ventilatory parameters were adjusted to obtain normocapnia and were maintained constant during the bronchospasm. Methacholine was administered via a synchronized nebulizer and progressively adjusted to obtain a stable twofold increase in peak inspiratory pressure.nMeasurements and results. Cardiopulmonary physiological data including assessment of lung mechanics and measurement of ventilation-perfusion relationships were obtained before and during the bronchospasm. Peak inspiratory pressure increased from 19.7±2.9 to 44.4±7.1xa0cmH2O during the bronchospasm. The latter remained stable over 2xa0h. Respiratory mechanics, gas exchange, and ventilation-perfusion distribution changes typical of those observed in severe bronchospasm in humans were observed in all animals.nConclusions. The present experimental model replicates some of the physiopathological characteristics of severe human bronchospasm, and its stability should facilitate studies of the effects of different ventilatory modes in the setting of acute severe asthma.

Even distribution of 133Xe bolus inhaled at residual volume in healthy subjects.

We selected from among 46 healthy students (22 to 31-yr-old) 7 subjects (group A) in whom the normalized height of phase IV (height of phase IV/phase IIIx100), after inhaling a bolus of He at RV, was very small (10%). We compared them with 6 subjects (group B) selected on the basis of a tall phase IV (78%, A vs. P P less than 0.005). Age and height were comparable, but weight was lower (P less than 0.05) and RV/TLC ratio (but not other spirographic indices) was larger (P less than 0.025) in group A. The average amplitude of cardiac oscillations was 4 times higher in group B (P less than 0.005). He closing volume, but not closing capacity was less in group A (P less than 0.05). A bolus of 133Xe inhaled at RV was nearly uniformly distributed in group A while producing a large vertical gradient in group B. The difference between groups A and B may reflect a difference in the mechanical properties of the chest wall leading to a less complete empting of the lung in the former group.