Abstract: Objective  To explore the different clinical outcomes in patients with stable primary spontaneous pneumothorax(PSP) treated with immediate therapy or delayed therapy. Methods  Eightythree patients admitted in the hospital  were randomly allocated to  immediate group(n=41) and delayed group(n=42). The durations of hospital stays of the two groups and the success rate of their primary treatment were compared.  The KaplanMeier method and the COX regression were used to analyze factors associated with hospital stay.  Results  The duration of hospital stay in immediate group was significantly longer than that of delayed group(P<0.01).  Univariate analysis showed that delayed treatment and large pneumothorax (pneumothorax size ≥50%), as well as right side pneumothoraxes were associated with prolonged hospital stay. However, only delayed treatment and large pneumothorax were risk factors for prolonged hospital stay by  multivariate COX proportional risk regression analysis(P＜0.05). The immediate group was better on both  hospital stay and  discharge rate on day 7 compared to the delayed group for patients with small PSP(P＜0.05). The immediate success rate for large PSP could be significantly improved by means of delayed treatment compared to the immediate treatment(P<0.01).  Conclusion  Without prolonging the duration of hospital stay, the delayed treatment shows higher immediate success rate for large stable PSP compared with that of the immediate treatment. Conservation may be choice of the outpatient management for some patients with stable small PSP.

Key words: pneumothorax, delayed treatment, hospital stay, the immediate success rate