Objective: To explore the nature of pathology of sluggishness of lung-defensive qi and to offer objective experimental indexes for weifen syndrome (defensive phase syndrome).Methods: According to the completely random design, the plasma levels of vasoactive intestinal peptide (VIP) and thromboxane B2 (TXB₂) of 19 patients with weifen syndrome and 13 patients with qifen syndrome (qi phase syndrome) were detected by radioimmunoassay. The plasma levels of VIP and TXB₂ at different stages of weifen syndrome and qifen syndrome were observed.Results: The plasma levels of VIP in weifen syndrome and in the late stage of weifen syndrome increased greatly at different stages as compared to qifen syndrome and the blank group (P<0.01), while the plasma level of TXB₂ of weifen syndrome was higher only at the late stage than the blank group and qifen syndrome (P<0.01). As for the levels of VIP and TXB₂ in weifen syndrome with different internal organs infected, there was no significant difference (P>0.05).Conclusion: VIP may be an index reflecting the pathology of weifen syndrome, and it is one of the material foundations of sluggishness of lung-defensive qi, but it has nothing to do with the infected internal organs. The level of TXB₂ increases only after the fever of patients with weifen syndrome subsided, so it can not be the basis for diagnosis of the early stage of weifen syndrome. It doesn't increase in qifen syndrome either, the mechanism remains to be further studied.

Key words: weifen diseases, vasoactive intestinal peptide, thromboxane B2