P2875

         Eur Respir J 1993 Apr;6(4):547-51

        Respiration after phrenicotomy and hydrocortisone treatment in

        anaesthetized rats.

        Nachazel J, Palecek F.

        Institute of Pathophysiology, 2nd Medical Faculty, Charles University,

        Praha, Czechoslovakia.

        The study was designed to determine the extent to which respiratory

        muscle wasting, resulting from corticosteroid-induced atrophy, may

        affect respiration in normal rats and in rats with denervated diaphragm.

        Twenty four male Wistar rats were divided into four groups: 1) controls

        with sham operation (SX) and vehicle injections: 2) SX with eight

        hydrocortisone (HC) injections (60 mg.kg-1.day-1 i.m.); 3)

        phrenicotomized (PX), injected with vehicle; 4) PX and HC-treated. HC

        treatment was started on the thirteenth day after surgery. Under

        urethane anaesthesia, tidal volume, respiratory rate, arterial carbon

        dioxide tension (PaCO2) and occlusion pressure were measured at rest and

        after 5 min of stimulated-breathing induced by added dead space 22nd day

        after surgery. All HC-treated animals decreased body weight by 32%

        compared to untreated rats. The diaphragm weight was reduced in PX rats

        by 29%, and after HC by 44%, while in PX rats with HC treatment

        diaphragm weight decreased by only 21%. PX rats (HC-untreated) had the

        lowest minute ventilation and occlusion pressure. There was no

        difference in ventilation between control and both HC-treated groups at

        rest. However, ventilation in PX and HC-treated rats did not increase

        upon stimulation, and the occlusion pressure increased significantly

        only in the HC-untreated animals. We conclude that in the rat, HC

        treatment did not affect resting ventilation, but it impaired

        ventilation performance, during increased demand, in animals handicapped

        by diaphragm denervation.

        Comment in:

        Eur Respir J. 1993 Apr;6(4):465-6.