A holistic investigation of the global outcomes of spontaneous pneumothorax during 1980-2021, including the COVID-19 pandemic A bibliometric approach

Abstract

Background:

During coronavirus pandemic, despite the increase in the number of studies on spontaneous pneumothorax (SP), there is not enough bibliometric study in the literature. In this study, it was aimed to analyze scientific articles published on SP.

Methods:

Studies published on SP between 1980 and 2021 were obtained from the Web of Science database and analyzed using statistical and bibliometric methods. Spearman correlation coefficient was used for correlation studies. The exponential smoothing estimator was used to forecast publication trend for coming years. Network visualization maps were used to analyze citations and identify trending topics.

Results:

A total of 2422 publications were found. 1403 (57.9%) of these publications were articles. The articles on SP have increased with a non-linear trend in recent years. The top 5 contributors to the literature were USA (231, 16.4%), Japan (161, 11.4%), United Kingdom (98, 6.9%), France (81, 5.7%), and Taiwan (78, 5.5%). The top 3 most active institutions were National Taiwan University Hospital (22, 1.5%), Catholic University Korea (19, 1.3%), and National Taiwan University (19, 1.3%). The top 3 journals that published the most articles were Chest (51), Annals of Thoracic Surgery (46), and Journal of Thoracic Disease (45). The most studied subjects were primary SP, recurrence, thoracoscopy, pleurodesis, video-assisted thoracoscopic surgery, COVID-19, video-assisted thoracic surgery, chest tube(s), and secondary spontaneous pneumothorax. According to trend topics analysis, the keywords studied in recent years are COVID-19, chest tubes, pneumonia, subcutaneous emphysema, risk factors, dyspnea, primary SP, FLCN gene, tension pneumothorax, uniportal, postoperative recurrence, secondary spontaneous pneumothorax, chronic obstructive pulmonary disease, and uniportal.

Conclusion:

In this comprehensive bibliometric study, we summarized 1403 articles about SP, which has an increasing trend in the number of articles during the COVID-19 pandemic process. This article can be a useful resource for clinicians and scientists through presenting a summary of worldwide studies related to SP, including the ones during COVID-19 pandemic.

1. Introduction

Pneumothorax occurs as a result of air accumulation in the pleural space. After that, collapse occurs in the lungs.^[1] Pneumothorax is classified as spontaneous, traumatic, or iatrogenic. Spontaneous pneumothorax (SP) is an important global health problem that can be life-threatening.^[2-4] SP may develop due to visceral pleural tears or bullae near the surface of the lung.^[5] Numerous respiratory disorders can cause SP. The most common underlying diseases are emphysema, chronic obstructive pulmonary disease (COPD), cystic fibrosis, tuberculosis, lung cancer, acquired immunodeficiency syndrome, and HIV-associated pneumocystis carinii pneumonia.

The type of treatment is determined according to the degree of pneumothorax. Small pneumothoraxes may be self-limiting, the patient can be followed clinically. In some cases, surgical treatment may be required. The surgical technique applied is usually video-assisted thoracoscopic surgery (VATS) and bulla resection.^[3,6]

Bibliometric is a statistical branch that uses statistical methods to analyze scientific articles in the literature.^[7] Due to increase in the number of publications in the literature, bibliometric studies have started to gain interest in recent years and bibliometric studies have been conducted on many subjects.^[7-14] Bibliometric studies reveal the most active authors, journals, countries, and the most cited studies in a cross-sectional period.^[8-12] Therefore, bibliometric studies enable researchers to perceive the literature in a short time.^[10] Keywords obtained as a result of analyzes make it easier for researchers to see past and current trends and to design new studies.^[13,14]

During coronavirus pandemic; the number of studies conducted worldwide on SP to evaluate the relationship between COVID-19 and SP is increasing. However, there are not enough bibliometric studies in the literature on this subject. In this study; we aimed to analyze scientific articles on SP published between 1980 and 2021 using bibliometric methods. As a result of the analyzes, we aimed to identify the most cited studies, the most active journals, institutions, authors, and countries, to reveal cross-country collaborations and trend issues, and thus to present a general summary of SP.

2. Material and methods

Web of Science Core Collection database (WoS) (by Clarivate Analytics, USA) was used for literature review. The publication search was done in the “Title” section of the studies. SP was used as the search keyword in WoS. In this way, all articles with the phrase “Spontaneous Pneumothorax” (Spontaneous Pneumothorax, Spontaneous Pneumothoraces, etc) in the title were obtained from the WoS database. Since there were no publications on this subject in WoS before 1980, the search process was determined as 1980 to 2021 (access date: November 05, 2021). Following criterion is used in the WoS database: TITLE: (pneumothor^*) and TITLE: (spontaneous^*); Timespan: 1980-2021. Indexes: SCI-Expanded, SSCI, A&HCI, CPCI-S, CPCI-SSH, BKCI-S, BKCI-SSH, ESCI.

The World map drawing was created to show the distribution of articles by country. For this, the website (https://datawrapper.de) was used. Bibliometric network visualizations and citation analyzes were performed using the VOSviewer (Version 1.6.17, Leiden University’s Center for Science and Technology Studies) package program.^[15] Statistical analyzes were performed with the SPSS (Version 22.0, SPSS Inc., Chicago, IL) package program. Normal distribution test of numerical data was analyzed with Kolmogorov-Smirnov test. The Exponential Smoothing estimator was used in the Microsoft Office Excel program to forecast the number of possible publications in the coming years based on past publication trends.

We investigated whether there is a relationship between the productivity of scientific work on SP and economic power of the countries. To determine this, correlation analysis was performed between the number of articles produced by the countries and the economic development of the countries. Gross domestic product (GDP) and gross domestic product per capita (GDP per capita) of countries were used for economic development indicator.^[16] Correlation analyzes were evaluated with Spearman correlation coefficient, since the data were not normally distributed. A P value of .05 is considered as statistically significant. In our analysis, article authors were identified as “first author or first author et al.”

3. Results

As a result of the literature search, a total of 2422 publications on SP published between 1980 and 2021 were found in WoS: Article (1403, 57.9%), meeting abstract (409, 16.8%), letter (234, 9.6%), review (103, 4.2%), proceedings paper (60, 2.4%), and the others (n=213; editorial material, note, correction, book chapter, early access, correction addition, discussion, and news item). Bibliometric analyzes were carried out with 1403 articles from a total of 2422 publications. 1247 (88.8%) of these articles were in English, 47 (3.3%) in French, 47 (3.3%) in German, 31 (2.2%) in Spanish, 16 (1.1%) in Russian, and the rest in Turkish (7), Portuguese (4), Italian (2), Japanese (1), and Polish (1). The h-index of 1403 articles was 63; average citations per article are 14.88; and sum of times cited is 20,880 (without self-citations: 12,512).

3.1. Development and future trends

The distribution of the number of published articles according to years is shown in Fig. 1. The number of forecasted articles, estimates of the Exponential Smoothing model that can be published in 2021 and beyond, are shown in Fig. 1. The number of articles published in 2021 was not included in the forecasting model. Based on the estimation model results, it was estimated that 108 (confidence interval %: 92-124) articles on SP would be published in 2021 and 114 (confidence interval %: 97-130) articles in 2025 (Fig. 1).

Figure 1. Distribution of articles published on spontaneous pneumothorax by years and the number of articles expected to be published in the future.

3.2. Active research areas

The research areas on SP articles are (>60 articles published) are respiratory system (487, 34.7%), surgery (470, 33.5%), cardiac cardiovascular systems (258, 18.3%), general internal medicine (245, 17.4%), pediatrics (70, 4.9%), critical care medicine (68, 4.8%), and emergency medicine (63, 4.4%).

3.3. Active countries

The distribution of the number of articles by countries is shown in Fig. 2. Top 10 countries with the highest number of articles are (published >50 articles) USA (231, 16.4%), Japan (161, 11.4%), United Kingdom (98, 6.9%), France (81, 5.7%), Taiwan (78, 5.5%), China (77, 5.4%), Turkey (77, 5.4%), South Korea (71, 5.0%), Italy (57, 4.0%), and Germany (53, 3.7%) (Fig. 2).

Figure 2. World map showing the distribution of articles published on spontaneous pneumothorax by world countries.

There are 84 countries. Twenty eight of these countries produced at least 5 articles whose authors have international cooperation. Cluster analysis was performed among these articles and respective countries. This analysis is shown in Fig. 3A.

Figure 3. A, Network visualization map of cluster analysis on international collaboration between countries on spontaneous pneumothorax. Colors indicate clustering. The size of the circle indicates the large number of articles. B, Density map for international collaboration of countries on spontaneous pneumothorax. The strength of international collaboration score increases from blue to red (blue-green-yellow-red).

According to clustering analysis, 7 different clusters related to international cooperation were formed: Cluster 1: Denmark, Sweden. Cluster 2: France, Belgium, Greece, Italy, Switzerland. Cluster 3: England, Scotland, Germany, Austria, Iran. Cluster 4: Australia, Ireland, New Zealand, Portugal. Cluster 5: Spain, China, Taiwan, Egypt. Cluster 6: Canada, Saudi Arabia. Cluster 7: USA, South Korea, India, Japan, Israel. In addition, the total link strength scores, showing the cooperation power of 28 countries, were calculated and the international collaboration density map of these scores is shown in Fig. 3B.

3.4. Correlation analysis

A statistically significant positive high correlation was found between the number of articles produced by countries and GDP values. Between GDP per capita and the number of articles, there was a statistically significant positive moderate correlation (rGDP=0.711, P<.001; rGDP per capita=0.623, P<.001, respectively).

3.5. Active authors

The 9 most active authors, who have published ≥10 articles on SP, were Chen JS (15, 1.06%), Hsu HH (14, 0.99%), Chou SH (12, 0.85%), Postmus PE (12, 0.85%), Tsuboshima. K (11, 0.78%), Kim YD (10, 0.71%), Matoba Y (10, 0.71%), Noppen M (10, 0.71%), and Wakahara T (10, 0.71%).

3.6. Active institutions

Top 10 institutions that have published ≥10 articles on SP were National Taiwan University Hospital (22, 1.5%), Catholic University Korea (19, 1.3%), National Taiwan University (19, 1.3%), Chinese University Hong Kong (13, 0.9%), Kaohsiung Medical University (12, 0.8%), China Med University (11, 0.7%), Yonsei University (11, 0.7%), Kuwait University (10, 0.7%), Nissan Tamagawa Hospital (10, 0.7%), and Takasago Municipal Hospital (10, 0.7%).

3.7. Active journals

One thousand four hundred three articles on SP were published in 474 different journals. The first 61 most active journals producing ≥5 articles, the total number of citations received by these journals, and the average number of citations per article are presented in Table 1. The citation network visualization map between these journals is shown on Fig. 4.

Table 1 .

The 61 most active journals that have published >5 articles on spontaneous pneumothorax.

Journals	RC	C	AC	Journals	RC	C	AC
Chest	51	2822	55.3	Helvetica Chirurgica Acta	8	15	1.9
Annals of Thoracic Surgery	46	2077	45.2	Emergency Medicine Journal	7	136	19.4
Journal of Thoracic Disease	45	187	4.2	Pediatric Surgery International	7	92	13.1
European Journal of Cardio-Thoracic Surgery	38	947	24.9	Journal of the Formosan Medical Association	7	60	8.6
Thoracic and Cardiovascular Surgeon	26	201	7.7	Minimally Invasive Therapy & Allied Technologies	7	33	4.7
European Respiratory Journal	25	1210	48.4	Respirology Case Reports	7	2	0.3
Respiratory Medicine	25	520	20.8	Surgical Endoscopy-Ultrasound and Interventional Techniques	6	188	31.3
Surgery Today	21	220	10.5	Internal Medicine	6	84	14.0
Interactive Cardiovascular and Thoracic Surgery	20	215	10.8	Pediatric Emergency Care	6	72	12.0
Journal of Cardiothoracic Surgery	19	193	10.2	Journal of Emergency Medicine	6	58	9.7
General Thoracic and Cardiovascular Surgery	19	69	3.6	Heart & Lung	6	15	2.5
American Journal of Emergency Medicine	18	219	12.2	Lung India	6	15	2.5
Journal of Thoracic and Cardiovascular Surgery	17	996	58.6	Zentralblatt fur Chirurgie	6	12	2.0
Thorax	17	846	49.8	Revista Clinica Espanola	6	3	0.5
Respiration	17	275	16.2	Vestnik Khirurgii Imeni II Grekova	6	0	0.0
Cureus	16	43	2.7	European Journal of Respiratory Diseases	5	195	39.0
Turk Gogus Kalp Damar Cerrahisi Dergisi-Turkish Journal of Thoracic and Cardiovascular Surgery	15	14	0.9	Journal of the American Animal Hospital Association	5	136	27.2
Surgical Endoscopy and Other Interventional Techniques	14	436	31.1	American Journal of Roentgenology	5	93	18.6
Journal of Pediatric Surgery	14	239	17.1	International Surgery	5	59	11.8
World Journal of Surgery	14	196	14.0	Aviation Space and Environmental Medicine	5	39	7.8
Annals of Thoracic and Cardiovascular Surgery	13	102	7.8	Journal of Laparoendoscopic & Advanced Surgical Techniques	5	37	7.4
Respiratory Medicine Case Reports	13	17	1.3	Acta Chirurgica Belgica	5	36	7.2
American Surgeon	11	59	5.4	Clinical Respiratory Journal	5	26	5.2
Revue des Maladies Respiratoires	11	46	4.2	Asian Journal of Surgery	5	21	4.2
Archivos De Bronconeumologia	10	100	10.0	Kardiochirurgia I Torakochirurgia Polska	5	19	3.8
BMJ Case Reports	10	13	1.3	BMC Pulmonary Medicine	5	3	0.6
Postgraduate Medical Journal	9	133	14.8	Medicine	5	3	0.6
Chirurg	9	76	8.4	Revue De Pneumologie Clinique	5	3	0.6
American Journal of Respiratory and Critical Care Medicine	8	654	81.8	Lyon Chirurgical	5	2	0.4
American Journal of Surgery	8	178	22.3	Pan African Medical Journal	5	2	0.4
Scandinavian Journal of Thoracic and Cardiovascular Surgery	8	98	12.3
AC=average citation per document, C=number of citation, RC=record count.

Figure 4. Network visualization map for citation analysis of active journals on spontaneous pneumothorax. The size of the circle indicates the large number of articles. The average number of citations per article by journals increases from blue to red (blue-green-yellow-red).

3.8. Citation analysis

The first 20 articles with the highest number of citations, out of 1403 articles were presented in Table 2. The last column of Table 2 presents the average number of citations per year.

Table 2 .

The top 20 most cited articles on spontaneous pneumothorax by total number of citations.

No	Article	Author	Journal	PY	TC	AC
1	Management of spontaneous pneumothorax - an American College of Chest Physicians Delphi Consensus Statement	Baumann, MH. et al.	Chest	2001	649	30.9
2	Risk of renal and colonic neoplasms and spontaneous pneumothorax in the Birt-Hogg-Dube syndrome	Zbar, B. et al.	Cancer Epidemiology Biomarkers & Prevention	2002	336	16.8
3	Smoking and the increased risk of contracting spontaneous pneumothorax	Bense, L. et al.	Chest	1987	260	7.43
4	Birt-Hogg-Dube syndrome, a genodermatosis associated with spontaneous pneumothorax and kidney neoplasia, maps to chromosome 17p11.2	Schmidt, LS. et al.	American Journal of Human Genetics	2001	214	10.19
5	Current aspects of spontaneous pneumothorax	Schramel, FMNH. et al.	European Respiratory Journal	1997	200	8
6	Lung cysts, spontaneous pneumothorax, and genetic associations in 89 families with Birt-Hogg-Dube syndrome	Toro, JR. et al.	American Journal of Respiratory and Critical Care Medicine	2007	188	12.53
7	Video-assisted thoracoscopic surgery versus thoracotomy for spontaneous pneumothorax	Waller, DA. et al.	Annals of Thoracic Surgery	1994	185	6.61
8	Manual aspiration versus chest tube drainage in first episodes of primary spontaneous pneumothorax - a multicenter, prospective, randomized pilot study	Noppen, M. et al.	American Journal of Respiratory and Critical Care Medicine	2002	180	9
9	Recurrence of primary spontaneous pneumothorax	Sadikot, RT. et al.	Thorax	1997	166	6.64
10	Uniportal vs standard three-port VATS technique for spontaneous pneumothorax: comparison of post-operative pain and residual paraesthesia	Jutley, RS. et al.	European Journal of Cardio-Thoracic Surgery	2005	160	9.41
11	Intrapleural tetracycline for the prevention of recurrent spontaneous pneumothorax - results of a department-of-veterans-affairs cooperative study	Light, RW. et al.	JAMA-Journal of the American Medical Association	1990	157	4.91
12	Safety and efficacy of video-assisted thoracic surgical techniques for the treatment of spontaneous pneumothorax	Naunheim, KS. et al.	Journal of Thoracic And Cardiovascular Surgery	1995	154	5.7
13	ERS task force statement: diagnosis and treatment of primary spontaneous pneumothorax	Tschopp, JM. et al.	European Respiratory Journal	2015	133	19
14	3 years experience in video-assisted thoracic-surgery (vats) for spontaneous pneumothorax	Inderbitzi, RGC. et al.	Journal of Thoracic and Cardiovascular Surgery	1994	132	4.71
15	Computed-tomography in the etiologic assessment of idiopathic spontaneous pneumothorax	Lesur, O. et al.	Chest	1990	130	4.06
16	Spontaneous pneumothorax - comparison of simple drainage, talc pleurodesis, and tetracycline pleurodesis	Almind, M. et al.	Thorax	1989	129	3.91
17	Spontaneous pneumothorax - comparison of thoracic drainage vs immediate or delayed needle aspiration	Andrivet, P. et al.	Chest	1995	126	4.67
18	The role of awake video-assisted thoracoscopic surgery in spontaneous pneumothorax	Pompeo, E. et al.	Journal of Thoracic and Cardiovascular Surgery	2007	125	8.33
19	Simple aspiration versus intercostal tube drainage for spontaneous pneumothorax in patients with normal lungs	Harvey, J. et al.	British Medical Journal	1994	120	4.29
20	Video-assisted thoracoscopic surgery for primary spontaneous pneumothorax - Evaluation of indications and long-term outcome compared with conservative treatment and open thoracotomy	Sawada, S. et al.	Chest	2005	113	6.65
AC=average citations per year, PY=publication year, TC=total citation.

3.9. Co-citation analysis

There were a total of 10,035 studies cited in the references section of all 1403 articles. Among these studies, the first 6 studies that received the most co-citations (>100 citations) were Baumann (2001) (number of citation: NC=244), Bense (1987) (NC=134), Macduff (2010) (NC=212), Melton (1979) (NC=146), Sahn (2000) (NC=204), and Schramel (1997) (NC=104).^[2,3,5,7-9]

3.10. Trend topics

One thousand three hundred seventy one different keywords were used in 1403 articles published on SP. Sixty five different keywords, which were used in at least 7 different articles, are shown in Table 3. The cluster network visualization map showing the results of clustering analysis between these keywords is shown in Fig. 5. Trend network visualization map performed to reveal trend topics is shown in Fig. 6. Citation network visualization map performed to reveal most cited topics is shown in Fig. 7.

Table 3 .

The 63 most frequently used keywords in articles about spontaneous pneumothorax.

Keywords	Number of uses	Keywords	Number of uses	Keywords	Number of uses
Pneumothorax	397	Primary spontaneous pneumothorax (PSP)	18	Chronic obstructive pulmonary disease	9
Spontaneous pneumothorax	262	Lung	17	Pleural disease	9
Primary spontaneous pneumothorax	114	Thoracoscopic surgery	17	Thoracic surgery	9
Recurrence	75	Spontaneous	16	Complications	8
Thoracoscopy	68	Bullae	15	FLCN gene	8
Pleurodesis	62	Video-assisted thoracoscopy	15	Pleural drainage	8
Video-assisted thoracoscopic surgery	45	Blebs	14	Smoking	8
VATS	39	Pediatric	13	Subcutaneous emphysema	8
COVID-19	30	Pleural abrasion	13	Thoracostomy	8
Video-assisted thoracic surgery	29	Temperature	12	Videothoracoscopy	8
Chest tube(s)	26	Aspiration	11	Bilateral pneumothorax	7
Secondary spontaneous pneumothorax	26	Bulla	11	Bleb	7
Pneumomediastinum	22	Computed tomography	11	Dyspnea	7
Bullectomy	21	Drainage	11	Minocycline	7
Pleurectomy	21	Management	11	Pneumonia	7
Risk factor(s)	21	Pleura	11	Postoperative recurrence	7
Thoracotomy	21	Talc	11	Single-incision thoracoscopic surgery	7
Surgery	20	Chest tube drainage	10	Surgical treatment	7
Video-assisted thoracoscopic surgery (VATS)	20	Children	10	Talc pleurodesis	7
Atmospheric pressure	19	Emphysema	10	Tension pneumothorax	7
Birt-hogg-dube syndrome	18	Chemotherapy	9	Uniportal	7

Figure 5. Network visualization map for cluster analysis based on keyword analysis on spontaneous pneumothorax. Colors indicate clustering. Keywords in the same cluster are of the same color. The size of the circle indicates the number of uses of the keyword. Cluster 1: bullectomy, pediatric, pleural abrasion, pleurectomy, postoperative recurrence, primary spontaneous pneumothorax (PNP), recurrence, risk factor, thoracoscopic surgery, uniportal, VATS. Cluster 2: aspiration, chest tube drainage, chronic obstructive pulmonary disease, minocycline, pleural drainage, secondary spontaneous pneumothorax, surgical treatment, talc pleurodesis, thoracoscopy, video-assisted thoracic surgery. Cluster 3: chest tubes, complications, drainage, lung, pleura, pleural disease, pneumothorax, surgery, thoracic surgery. Cluster 4: bilateral pneumothorax, chemotherapy, dyspnea, risk factors, smoking, tension pneumothorax, thoracostomy. Cluster 5: bleb, bulla, pleurodesis, talc, thoracotomy, video-assisted thoracoscopic surgery, videothoracoscopy. Cluster 6: COVID-19, emphysema, pneumomediastinum, pneumonia, subcutaneous emphysema. Cluster 7: blebs, bullae, computed tomography, video-assisted thoracoscopy. Cluster 8: atmospheric pressure, management, spontaneous, temperature. Cluster 9: birt-hogg-dube syndrome, FLCN gene, primary spontaneous pneumothorax, single-incision thoracoscopic surgery. Cluster 10: children.

Figure 6. Network visualization map for trends on spontaneous pneumothorax. In the indicator given in the lower right corner of the figure, the topicality of the article increases from blue to red (blue-green-yellow-red). The size of the circle indicates the number of uses of the keyword.

Figure 7. Network visualization map of the most frequently cited topics on spontaneous pneumothorax. In the indicator given in the lower right corner of the figure, the number of citations received by the topic increases from blue to red (blue-green-yellow-red). The size of the circle indicates the number of uses of the keyword.

4. Discussion

Between 1980 and 1992 the average number of articles on SP was 17; the average number was 31 between 1993 and 2015, and it was 76 between 2016 and 2020. The number of articles published in 2020 has exceeded 100, and there has been a remarkable increase in the number of articles in recent years and 107 articles were published in 2020. In recent years, there has been an increase in the number of articles with an exponential trend. When the Exponential Smoothing estimator results are evaluated, the number of articles will continue with an increasing exponential trend.

The significant increase in the number of published articles in 2020 reveals the effect of the COVID-19 pandemic, which started in December 2019, on pneumothorax. Studies have also shown that the incidence of pneumothorax in patients with a diagnosis of COVID-19 is higher than in non-COVID patients.^[17,18] Pneumothorax is considered as a common complication of acute respiratory distress syndrome (ARDS) associated with COVID-19 infection.^[19] The result of our bibliometric analysis shows that with the increase in COVID-19 cases, the number of publications on pneumothorax has increased. This shows that the number of pneumothorax cases has increased due to the COVID-19 pandemic.

When the publication distribution of the countries was examined; the most active countries were developed countries such as USA, Japan, United Kingdom, France, China, South Korea, Italy, and Germany. According to the results of the correlation analysis, there is a high level significant correlation between article productivity and GDP; and a moderate level significant correlation between productivity and GDP per capita. This shows that the country economic development has an important affect in publication productivity. In the bibliometric studies conducted on different medical topics in the literature, it is stated that economic power is effective in productivity.^[8-11]

When the density map created according to the total cooperation score between countries is evaluated; the countries with the most intensive cooperation were determined as USA, England, Italy, France, Canada, Netherlands, Switzerland, Belgium, Germany, and Australia. This also show when the co-authorship cooperation of countries is examined, it is seen that cooperation based on geographical location is effective in the production of articles. Similarly, according to some studies, it is stated that geographical proximity is effective in the production of publications.^[11,14] However, countries that do not have geographical proximity also conduct joint studies. (Canada, Saudi Arabia), (Spain, China), (USA, Japan), (Scotland, Germany). The cooperation of countries with no geographical proximity, which we obtained in our research, can be attributed to the developing technology, and this shows that universal clinical conclusions can be reached about pneumothorax cases.

The journals that publish the most articles on SP were Chest, Annals of Thoracic Surgery, Journal of Thoracic Disease, European Journal of Cardio-Thoracic Surgery, Thoracic and Cardiovascular Surgeon, European Respiratory Journal, Respiratory Medicine, Surgery Today, Interactive Cardiovascular, and Thoracic Surgery. We can suggest that authors who want to publish on SP can consider these journals.

When the citation analyzes of the journals are evaluated, the most effective journals according to the average number of citations per article are American Journal of Respiratory and Critical Care Medicine, Journal of Thoracic and Cardiovascular Surgery, Chest, Thorax, European Respiratory Journal, Annals of Thoracic Surgery, European Journal of Respiratory. Diseases were Surgical Endoscopy-Ultrasound and Interventional Techniques, Surgical Endoscopy and other Interventional Techniques. We can suggest that researchers who want their articles to be cited more can consider these journals.

According to the mean and total citation count, we recommend clinicians and researchers to read the following articles; Baumann et al, Zbar et al, Bense et al, Schmidt et al, Schramel et al, Brown et al, Vega et al, Tschopp et al, Ucpinar et al, Toro et al, Miro et al, Bobbio et al.^[6,20-30]

According to keyword analysis, SP formed 10 different clusters. The most cited keywords were minocycline, aspiration, management, video-assisted thoracoscopy, chest tube drainage, birt-hogg-dube syndrome, primary spontaneous pneumothorax (PSP), single-incision thoracoscopic, talc pleurodesis, and uniportal surgery. According to trend topics analysis, the keywords studied in recent years are COVID-19, chest tubes, pneumonia, subcutaneous emphysema, risk factors, dyspnea, PSP, FLCN gene, tension pneumothorax, uniportal, postoperative recurrence, secondary spontaneous pneumothorax, COPD, and uniportal. According to the keyword analysis in our bibliometric research, we can state that pneumothorax and COVID-19, thoracic surgery, and COPD are closely related. In addition, the frequent use of the keywords “risk factors,” “birt-hogg-dube syndrome,” and “FLCN gene” in studies reveals the clinical effort of researchers to detect pneumothorax risk factors and genetic tendency.

If we evaluate the results clinically; our bibliometric study provides clinicians with the opportunity to conduct research on pneumothorax more quickly and practically by identifying the most popular researches, journals, and authors on pneumothorax. This study can serve as a guide so that researchers can produce more articles on pneumothorax. In addition, although a statistical analysis was made with our bibliometric study, the results we obtained clinically revealed a significant increase in pneumothorax cases in a lung-specific epidemic such as the COVID-19 pandemic. Therefore, a more detailed evaluation of organ-specific diseases, such as pandemics and epidemics, that seriously endanger public health, after bibliometric analyzes will contribute significantly to approaches to these diseases.

As a result of the literature review on SP, we could not find any bibliometric study. We can say that our study on this subject is the first bibliometric research. The usage of WoS for literature review in the study has caused a limitation. Wedid not prefer Scopus database, because it indexed journals with low impact levels. The WoS indexes articles published in journals with a higher impact level than other databases.^[31,32]On the other hand, citation and co-citation analyzes cannot be performed in PubMed database. Therefore, WoS has been preferred more widely in bibliometric analyzes.^[7-14]

5. Conclusion

In this bibliometric study, we shared a summary of 1403 articles published between 1980 and 2021 on SP, which has had an increasing trend in the number of articles during the COVID-19 pandemic. According to trend topics analysis, the keywords studied in recent years are COVID-19, chest tubes, pneumonia, subcutaneous emphysema, risk factors, dyspnea, PSP, FLCN gene, tension pneumothorax, uniportal, postoperative recurrence, secondary spontaneous pneumothorax, COPD, and uniportal. This article can be a useful resource for clinicians and scientists via presenting a summary of studies related to SP, including the COVID-19 pandemic duration.

Author contributions

The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Conceptualization: Ramazan Baldemir, Gülay Ülger.

Data curation: Ramazan Baldemir, Gülay Ülger.

Formal analysis: Ramazan Baldemir, Gülay Ülger.

Investigation: Ramazan Baldemir, Gülay Ülger.

Methodology: Ramazan Baldemir, Gülay Ülger.

Project administration: Ramazan Baldemir, Gülay Ülger.

Resources: Ramazan Baldemir, Gülay Ülger.

Supervision: Ramazan Baldemir, Gülay Ülger.

Visualization: Ramazan Baldemir, Gülay Ülger.

Writing - original draft: Ramazan Baldemir, Gülay Ülger.

Writing - review & editing: Ramazan Baldemir, Gülay Ülger.