One of the Isoflurane respiratory effects is that, Isoflurane causes bronchodilatation by inhibiting bronchoconstriction.
As with other potent vapours, isoflurane impairs both ventilatory drive and hypoxic pulmonary vasoconstriction leading to hypercapnia and V/Q mismatch.
In asthmatic patients due to its lack of arrhythmogenic potential, drugs like aminophylline or agonists such as salbutamol may be less hazardous than with halothane. There is a decrease in FRC and lung compliance. These were some Isoflurane respiratory effects
Miller’s Anesthesia 7th Edition says the following about Isoflurane respiratory effects –
Anesthetics themselves may alter ventilation and thereby alter their own uptake. Modern potent agents (desflurane, halothane, isoflurane, sevoflurane) are profound respiratory depressants whose capacity to depress ventilation is directly related to anesthetic dose. At some concentration, all inhaled anesthetics probably produce apnea, a feature that must limit the maximum alveolar concentration (MAC) that can be obtained with spontaneous ventilation.
These observations imply that imposed alterations in ventilation (e.g., an increase produced by conversion from spontaneous to controlled ventilation) produce greater changes in anesthetic concentration (and thus effect) with more soluble agents. Because such effects include both anesthetic depth and depression of circulation, greater caution must be exercised when ventilation is augmented during anesthesia produced with a highly soluble agent.