Diaphragmatic dysfunction secondary to experimental lower torso ischaemia-reperfusion injury is attenuated by thermal preconditioning

Background: Preconditioning describes the process whereby tissue exposure t o a subcritical stress confers protection from subsequent injuries. This st udy assessed diaphragmatic muscle function after lower torso ischaemia-repe rfusion (IR) and the role of thermal preconditioning in attenuation of this injury. Methods: Sprague-Dawley rats were randomized into three groups (24 per grou p): a control group, an IR group that had aortic cross-clamping for 1 h fol lowed by reperfusion, and a third group that received thermal preconditioni ng 18 h before IR. Diaphragmatic function was assessed at 24 h, 48 h and 7 days. Results: IR resulted in significant diaphragmatic twitch and tetanic dysfun ction compared with control muscle. Thermal preconditioning significantly a ttenuated this injury (P < 0.05). Mean(s.e.m.) muscle twitch and tetanic fo rces in the IR group were 204.9(17.2) and 282.7(19.2) g respectively at 24 h. Corresponding twitch and tetanic forces in preconditioned muscle were 27 0.4(25.1) and 552.0(35.2) g. Conclusion: This study demonstrated that systemic IR injury produced a resp iratory muscle mechanical dysfunction that was attenuated by thermal precon ditioning, at 24 h, 48 h and 7 days. Preconditioning may have a role in cli nical practice, particularly before elective surgery.