Intermittent obstructive apnea in conscious rats

Abstract

We developed a new method to intermittently obstruct the airway in conscious rats to replicate the hypercapnea and respiratory effort characteristic of sleep apnea. A teflon tube (6 mm long, o.d. 2.5 mm, i.d. 2.1 mm) was inserted in the trachea of adult male rats. This tube contained the tip of an inflatable balloon catheter made from polyurethane tubing (10 cm long, o.d. 1.0 mm, i.d. 0.6 mm, Scientific Commodities, USA). The open end of the balloon catheter left the trachea through the incision, and was led subcutaneously to a metal connector that was externalized between the shoulder blades. Thus inflation of the balloon catheter closed the trachea without causing pain. Rats rapidly regained body weight after surgery and appeared healthy, although breathing occasionally was audible during the subsequent 1 – 2 months. Inflation of the balloon for 10 sec with 15 μL water caused forceful breathing movements. Heart rate became irregular and fell by up to 200 beats/min, and these effects were blocked by pretreatment with 3 mg atropine. Balloon inflation increased blood pressure by up to 40 mm Hg, and caused caused alertness, locomotion and rearing. These effects disappeared almost instantly after disinflation. Inflations repeated every 3 min gave reproducible cardiovascular changes. This method seems suitable for the analysis of the effects of chronic intermittent apnea. Financial support: FAPESP, CNPq.