Airways resistance increase, smokers

The effects of desflurane and sevoflurane on bronchial smooth muscle reactivity have been compared in a randomized study of 40 patients (36). Anesthesia was induced with thiopental, followed by muscle relaxation and ventilation. Airway pressures were recorded during administration of desflurane or sevoflurane at one minimal alveolar concentration (MAC). Airway resistance increased by 5% in the desflurane group and fell by 15% in the sevoflurane group. The increase in airways resistance was greater in smokers and with desflurane, but did not differ with sevoflurane. The result was a surprise, given that desflurane stimulates the sympathetic nervous system. Thiopental also increased airways resistance by 10%. The result is important, because induction of anesthesia can cause bronchospasm and desflurane can exacerbate this. 

A 37-year-old man who had taken lithium and sulpiride for 14 years and who was a long-time smoker without respiratory symptoms or a history of asthma had lithium withdrawn because of an asymptomatic bradycardia (44 beats/minute) (125). Six weeks later, he developed symptoms of asthma, including nocturnal cough, exertional wheezing, increased airway resistance, and a low FEV1, attributed to lithium withdrawal. 

In children, capsaicin spray was demonstrated to cause a severe bronchospasm and pulmonary edema (Winograd, 1977 Bdlmire et al, 1996). In the Billmire study, a 4-week-old infant was exposed to 5% pepper spray after discharge from a self-defense device. The infant suffered respiratory failure and hypoxemia, requiring immediate extracorporeal membrane oxygenation. Inhaled capsaicin causes an immediate increase in airway resistance (Fuller, 1991). This dose-dependent bronchoconstriction after capsaicin inhalation in humans is the same as that demonstrated in asthmatics and smokers (Fuller et al, 1985). The capsaicin-induced bronchoconstriction and release of substance P is due to stimulation of nonmyelinated afferent C-fibers. 

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