Introduction

Pneumothorax is described as a pathological accumulation of air between the pleural leaves, causing lung collapse (1). Spontaneous pneumothorax (SP) is classified under two main headings as ‘primary’ and ‘secondary.’

Primary SP (PSP) usually occurs in young, tall, smoking men without any lung disease. Sub-pleural blisters or blew ruptures are blamed in the etiology. The incidence is highest around the 20s. In the past, it was about 6-times more common among men. However, today, this ratio reaches around 3, possibly due to the increase in smoking among women (2).

There is underlying lung pathology in patients with secondary SP (SSP) (3). Thus, the process may be more severe in patients whose lung function is already impaired due to existing disease. SSP affects the elderly more frequently, chronic obstructive pulmonary disease (COPD) being the most common cause. Its incidence in these patients is approximately 26/100 thousand/year (4).

Atmospheric pressure, temperature (°C), humidity, or sudden weather changes are blamed for being involved in the etiology of SP (5,6). Due to conflicting literature between the relationship between atmospheric changes and SP, there is a need for further clarifying studies.

This study aimed to investigate the effects of weather and atmospheric pressure changes on SP hospital admissions in Bursa Yüksek İhtisas Training and Research Hospital located in Bursa city where southwestern winds are prevalent.

Materials and Methods

Study Design

This study was designed as descriptive-analytical cross-sectional research. Survey reporting was done per the STROBE guidelines (7).

Setting

The study was conducted retrospectively using the hospital records of patients diagnosed with SP in the emergency department or thoracic surgery outpatient clinics between January 2016 and December 2018. This hospital is the largest and most comprehensive health center in Bursa city of Turkey with a capacity of 1.370 beds. The daily number of patients served is approximately 10,000. Approximately 3500 patients are seen each day in the emergency department.

Ethics committee approval was received for this study from the Medical Ethics Committee of University of Health Sciences Turkey, Bursa Yüksek İhtisas Training and Research Hospital (approval no: 2011-KAEK-25 2019/06-20, date: 23.11.2011).

Participants

In this study, the data of 264 (2.1 per 1000) adult persons diagnosed with pneumothorax from 1 203 339 patients who applied to the hospital throughout the 944 days between 01.06.2016 and 31.12.2018 (Figure 1), and the climatic data between these dates were analyzed.

The diagnosis of SP was made from the patient’s history, physical examination findings, posterior-anterior chest radiography, and thorax-computed tomography. PSP and SSP were differentiated using clinical examination and radiological imaging.

The patient admissions were grouped according to the days, months, and seasons. Meteorological data, including daily average °C, atmospheric pressure (millibars), moisture (%), and wind (meters/second), were obtained from Bursa meteorological directorate. The meteorological data on the days with and without SP was compared.

Variables

The primary outcome variable of the study was “the presence of pneumothorax”. The independent variables were age, sex, type of pneumothorax, affected lung side, the presence of southwestern winds (lodos), season, mean daily atmospheric pressure, mean daily humidity, mean daily °C, and the total number of emergency applications.

Study Size

Without sampling, all patients diagnosed with pneumothorax between 01.06.2016 and 31.12.2018 were included in the study.

Statistical Analysis

The data were analyzed using the Statistical Package for the Social Sciences (SPSS) version 25.0 software (SPSS Inc., Chicago, IL, USA). The results of the study are presented as frequencies and percentages for categorical variables and as means and standard deviations for numerical variables. The normal distribution of the numerical variables was evaluated by checking the skewness coefficients. The independent samples t-test, Mann-Whitney U test, Kruskal-Wallis test, or One-Way ANOVA were used to compare the groups. Multivariate comparisons were examined by logistic regression analysis. The statistical significance threshold was taken as p<0.05.

Results

The median number of daily emergency admissions during the study period was 1263 (minimum: 875, maximum: 1643). Total 264 patients diagnosed with pneumothorax were included in this study. Of the patients, 27 (10.2%) were female, and 237 (89.8%) were male. The mean age was 36.71±17.95 years (minimum 18, maximum 92). One hundred-eighty five (70.0%) patients had PSP, while 79 (29.9%) had SSP. Out of 1 203 339 emergency applications, 264 cases of SP were encountered (2.1 cases per 10 000 emergency admissions).

PSP vs. SSP distribution among males and females [males: 165 (69.6%) vs. 72 (30.4%), females: 20 (74.1%) vs. 7 (25.9%), respectively] was not significantly different (chi-square=0.229, p=0.632). However, the mean age was significantly higher among patients with SSP (61.08±11.42 years) compared to patients with PSP (26.30±6.46 years) (Mann-Whitney U Z=12.855, p<0.001).

At the time of the study, the min.-max. values of daily °C, atmospheric pressure, and humidity in Turkey were reported as -3.6-30.9 °C, 749.5-1024.6 millibar, and 31.3-98.8%, respectively. At least one pneumothorax application was made to the hospital in 214 (22.7%) of 944 days included in the study.

All the patients were hospitalized. Tube thoracostomy was applied in 94.7% (n=250) of the patients, and medical therapy (oxygen inhalation, analgesia, and observation) was performed in 5.2% (n=14) of the patients. Fifty-six (22.4%) patients who underwent tube thoracostomy required surgical intervention. During the follow-up, one patient died from severe COPD and respiratory failure. Hence, the mortality rate was 0.3%. COPD was the most common etiology in patients with SSP.

The highest rate of SP was seen in autumn (24.9%, n=68), followed by summer (23.9%, n=66), spring (20.7%, n=38), and winter (19.9%, n=42). There was no difference concerning the seasons (chi-square=2.371, p=0.499).

Although southwestern winds were reported during 703 days (74.5%), these winds were not present on 241 days (25.5%). Regarding the daily number of pneumothorax patient admissions, there was no statistically significant relationship between southwestern winds and SP (Table 1).

Statistical significance was determined in the One-Way ANOVA test conducted to determine whether there was a difference in the distribution of atmospheric pressure (mb), humidity (%) and °C according to month (p<0.05). In the post-hoc tukey test conducted to determine the months of the difference, lower atmospheric pressure and humidity and higher °C were detected in July, August and September. In the Kruskal-Wallis test conducted to determine whether there is a difference between the distribution of PSP, SSP and TSP by months, it was seen that SSP was significantly higher due to August and September (p<0.05) (Table 2 and Figure 2).

Although the mean atmospheric pressure was slightly lower during the days with SP admissions, there was no statistically significant difference between the number of pneumothorax cases and the meteorological variables (Table 3).

Discussion

This study demonstrated the prevalence of 2.1 SP cases per 10,000 emergency admissions. There was a decrease in the mean atmospheric pressure during July, August, and September. The presence of southwestern winds, daily atmospheric pressure, daily humidity, and daily °C do not increase the number of diagnoses of total SP. However, SSP cases present most commonly during August and September when the atmospheric pressure was relatively low.

SP is a relatively rare disease, but it is one of the most common pathologies encountered in thoracic surgery. It is often seen as a PSP, and there is no underlying etiological cause. The annual incidence of PSP was reported as 7.4-18/100,000 for men and 1.2-6/100,000 for women. In SSP cases, the yearly rate is given as 6.3/100,000 for males and 2.0/100,000 for females (8). In this study, we could calculate only the incidence of SP among emergency applications.

We did not record the presence of concomitant diseases or a history previous pneumothorax. However, the most frequent concomitant lung diseases are reported as COPD, tuberculosis, cystic fibrosis, lung cancer (5). Although it is more common in patients with PSP, recurrent pneumothorax can be seen in various proportions ranging from 16 to 52% (9,10).

The influence of climatic conditions on human health has been extensively studied. There are reports that °C, humidity, and atmospheric pressure changes may play a role in the hospital admission, hearing loss, asthma, myocardial infarction, and joint problems (11-15). In our study, lower atmospheric pressure and humidity and higher °C were detected in July, August and September. As the °C increases, the air pressure decreases. We found that SSP was significantly higher in August and September. These are the hottest and driest months in Bursa (16). Perhaps the °C-dependent air pressure may have a threshold; when it falls below a certain level, it may increase an increase in the incidence of pneumothorax.

Studies reporting the relationship between seasonal changes and SP rates are inconsistent. Earlier in 1972, it was mentioned that the frequency of SPs was highest between October and March (17). However, this could not be confirmed by later studies (18,19). Although our study did not reveal a significant difference in the number of total SP applications, there was a seasonal variation concerning SSP, which was more common during the months with relatively low atmospheric pressure. However, we could not demonstrate a relationship between the atmospheric pressure and the number of SP. Thus, we infer that this finding may be due to secondary factors affecting pneumothorax. It may be postulated that the higher rate of SSP during the days with low atmospheric pressure may be due to the worsening of COPD during these days (20). Besides, it was argued that that atmospheric ozone was higher in the spring, which allegedly causes pleural bled and blister rupture (21).

According to a study conducted in the northeast of Turkey, the wind speed was lower on the days with SP compared to the other days (22). However, no significant difference was found in a study investigating the effect of weather and Chinook winds on SP (19). In our research, most of our cases SP were PSP, and most of these cases occurred in southwestern wind days and autumn. However, we could not find a statistically significant between the number of pneumothoraxs and southwest winds as in previous studies.

In a study to investigate whether atmospheric pressure changes played a role in the formation of SP, no effect was demonstrated (23). Other studies could not confirm a significant impact of daily °C, humidity, and atmospheric pressure changes on SP formation (24,25). However, some studies claimed a substantial relationship between PSP and climatic changes with an increased incidence of PSP in case of low atmospheric pressure (26,27). Another study stated that increased air pollution and sudden atmospheric pressure change increased the frequency of PSP (28). As to a report from Japan, the incidence of SP increases significantly when atmospheric pressure drops (27). Also, in a study conducted in Tunisia, where the Mediterranean climate is dominant, it was found that there was a significant relationship between the seasons with high average air °C and SP (29). In our study, no statistically significant difference was found between the incidence of pneumothorax and daily atmospheric pressure.

Study Limitations

The absence of data from other hospitals in Bursa city was considered a limitation of the study. Since SP is a rare condition, including other health centers could yield more significant results by increasing the sample size. Addition, other potentially substantial factors and confounders such as air pollution and co-morbidities deserved attention in this study.

Conclusion

SSP was significantly higher in August and September because of lower atmospheric pressure, humidity and higher °C.

Ethics

Ethics Committee Approval: Ethics committee approval was received for this study from the Medical Ethics Committee of University of Health Sciences Turkey, Bursa Yüksek İhtisas Training and Research Hospital (approval no: 2011-KAEK-25 2019/06-20, date: 23.11.2011).

Informed Consent: Retrospective study. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. No animal or human studies were carried out by the authors in this article.

Peer-review: Externally and internally peer-reviewed.

Authorship Contributions

Surgical and Medical Practices: M.A.H., E.A., Concept: M.A.H., E.A., Design: M.A.H., E.A., Ö.Ş.D., Data Collection or Processing: M.A.H., E.A., Ö.Ş.D., M.Ö., Analysis or Interpretation: M.A.H., M.Ö., M.O.A., H.K., M.Y., Literature Search: M.A.H., M.Ö., M.O.A., H.K., M.Y., Writing: M.A.H., E.A., M.O.A., H.K., M.Y.

Conflict of Interest: No conflict of interest was declared by the authors.

Financial Disclosure: The authors declared that this study received no financial support.