The study aims to evaluate the association between spontaneous pneumothorax onset and weather parameters.

The aim of this study is to analyse the relation between onset of the PSP and exposure to environmental factors such as atmospheric pressure.

A case-crossover epidemiological study will be conducted in 14 French hospitals. SP recorded from 2009 to 2013 will be exhaustively included. Demographic and clinical characteristics will be collected. For each incident case of SP, the period of occurrence of the event (case period) will be compared to several other periods temporally distant from the case period (control periods prior to and after the event). Exposure will be assessed using meteorological stations localized in the vicinity of each patient's home. A potential threshold effect and/or time lag effect between exposure and admission for SP will be explored.

The results of this study will help to identify the meteorological factors associated with the occurrence of SP, and to deepen our knowledge of the pathophysiological mechanisms of SP especially the influence of meteorological factors on bleb rupture.

Inclusion Criteria:

• age over 18 years
• first episode of primary spontaneous pneumothorax

Exclusion Criteria:

• Patients with traumatic
• Patients with secondary pneumothorax
• Patients with recurrent pneumothorax and patients with short-term readmissions (recurrence was defined as a new ED admission for the same diagnosis more than 14 days after the first admission).

Patients were recruited in the emergency departments (ED) of fourteen French hospitals that are members of the EXPRED Network (EXPRED Study) (Desmettre et al. 2011) where emergency admission management software was available.

A search was performed of ED admissions databases to identify all patients with a primary diagnosis of pneumothorax (International Classification of Diseases (ICD) 10 code = J93) admitted between June 1, 2009 and May 31, 2013).