A study of the pulmonary circulation during experimental asthma was conducted in anesthetized mongrel dogs with natural sensitivity to Ascaris suum antigen. They were intubated with an orotracheal tube and their respiration was maintained by transvenous phrenic nerve stimulation. Measurements of respiratory mechanics, gas exchange and pulmonary circulation were made before and serially for 2 hours after challenge with an aerosol of Ascaris suum extract. The determinations were made during apnea and consisted of respiratory resistance by forced oscillations, static lung compliance, FRC, dead space and alveolar ventilation, arterial blood gas determinations, pulmonary arterial and left atrial pressures, and cardiac output and pulmonary blood volume by a double indicator dilution technique. Nine of 14 dogs randomly selected for room air or 70% oxygen breathing responded to the antigen challenge with bronchospasm reflected by a transient decrease of mean specific respiratory conductance (reciprocal of respiratory resistance divided by FRC) to 50% of baseline after 5-15 minutes. This was accompanied by alveolar hypoventilation in all and respiratory acidosis in some animals. No changes were observed in static lung compliance or FRC. Transmural pulmonary arterial pressure, cardiac output, pulmonary vascular resistance and pulmonary blood volume remained unchanged both at FRC and simulated pulmonary hyperinflation (by continuous phrenic nerve stimulation) in all 9 dogs who responded with a decrease in specific respiratory conductance, regardless of whether or not arterial hypoxemia was allowed to develop. Similarly, no changes of the pulmonary circulation were detected in the 5 dogs who did not develop bronchospasm. These results indicate that in the canine asthma model, moderately severe acute, antigen induced bronchospasm is not associated with changes in transmural pulmonary arterial pressure or pulmonary vascular resistance, even in the presence of arterial hypoxemia and acidosis.
|Original language||English (US)|
|Number of pages||1|
|Journal||American Review of Respiratory Disease|
|Issue number||4 II|
|State||Published - Jan 1 1976|
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine