Abstract: AIM: To set up a fatigued diaphragm model in vitro duo to hypoxic, hypercapnic acidosis, and to observe the effects of salmeterol and caffeine on this model. METHODS: The fatigued diaphragm model was set up with mixed gas including 21 %O₂, 12 %CO₂ and 67 % N₂, and the effects of salmeterol (10^-9-10^-6mol·L^-1) and caffeine (10^-5-10^-3 mol·L^-1) on fatigued diaphragmatic contractility were surveyed. RESULTS: The value of force decreased by gas mixture at each frequency (5-120Hz).PTT, maintaining tension, and tension by muscle-stimulation decreased significantly; diaphragmatic contractile force of diaphargma increased by salmeterol with the concentration of 10^-9-10^-6mol·L^-1at the frquencies 40-120 Hz(P <0.05);contractile force of diaphragma and PTT, maintaining tension and tension by muscle-stimulation significantly increased by caffeine with the concentration of 10^-4 or 10^-3mol·L^-1 atall stimulus frequencies (5-120 Hz) (P <0.01). CONCLUSION: The model of rat diaphragmatic fatigue in vitro induced by hypoxic and hypercapnic acidosis can be set up by aerating with 3 kind of gas mixed with 21 % O₂, 12 %CO2 and 67 %N₂, and contractility of fatigued diaphragm of rat enhanced by salmeterol and caffeine to some extent.

Key words: salmeterol, caffeine, diaphragmatic fatigue, model