20 years clinical application of the vacuum bell for conservative treatment of pectus excavatum—past, present, future
Original Article

20 years clinical application of the vacuum bell for conservative treatment of pectus excavatum—past, present, future

Frank-Martin Haecker1,2

1Department of Pediatric Surgery, Children’s Hospital of Eastern Switzerland, St. Gallen, Switzerland; 2Faculty of Medicine, University of Basel, Basel, Switzerland

Correspondence to: Frank-Martin Haecker, MD. Professor of Pediatric Surgery, Consultant Pediatric Surgeon, Children’s Hospital of Eastern Switzerland, Claudiusstrasse 6, 9006 St. Gallen, Switzerland; Faculty of Medicine, University of Basel, Basel, Switzerland. Email: frank-martin.haecker@kispisg.ch.

Background: For decades, open surgical repair was the only available method to treat pectus excavatum (PE). In 1998 Donald Nuss described first time a minimally invasive repair of pectus excavatum (MIRPE), and today MIRPE is performed with increasing frequency worldwide. However, despite its minimally invasive approach, with the widespread use of MIRPE the character and number of complications have increased. 20 years ago, non-surgical measures such as vacuum bell therapy (VBT) were introduced as a useful complement for specific treatment of PE patients. However, until today there are no existing validated guidelines concerning VBT.

Methods: The study includes the results of an online survey submitted to the members of Chest Wall International Group (CWIG), a selective review of the English spoken current literature with focus on VBT and an analysis of our own previous studies concerning VBT.

Results: Seventy-two percent of the CWIG members practicing in 47 different institutions confirmed to use VBT for PE patients. Furthermore, within the last 10 to 15 years an increasing number of studies were identified reporting on successful use of VBT for PE. However, a recently published study stated that the effect of VBT is predominantly because of thickening of the chest wall by increasing pre-sternal adipose tissue. There was one study comparing VBT to MIRPE but no randomized and/or prospective studies comparing conservative treatment vs. surgical repair or conservative treatment vs. no specific therapy. Variables predictive of an excellent outcome could be identified. Especially in younger PE patients, VBT is reported with increasing frequency in the survey as well as in the literature. However, validated guidelines concerning VBT are still not available.

Conclusions: Non-operative treatment of PE with VBT proved to be safe and a potential alternative to surgical repair in carefully selected PE patients. Patient’s age at diagnosis and severity of the PE represents relevant variables to decide which kind of therapy might be successful to correct PE. Especially in PE patients under the age of 10 years, VBT seems to represent the first step of specific therapy.

Keywords: Pectus excavatum (PE); conservative treatment; vacuum bell therapy (VBT); outcome

Submitted Mar 13, 2024. Accepted for publication Jul 03, 2024. Published online Aug 15, 2024.

doi: 10.21037/jtd-23-408

Highlight box

Key findings

• The vacuum bell therapy (VBT) for conservative treatment of pectus excavatum (PE) could be established as an additional useful tool in specific treatment of PE patients within the last 20 years.

What is known and what is new?

• Within the last decade, an increasing number of studies have reported on an increasing number of PE patients treated with VBT.

• Variables predicting a successful outcome could be identified.

What is the implication, and what should change now?

• Based on the review and the identified variables, validated guidelines concerning VBT have to be determined.

Introduction

Pectus excavatum (PE) represents the most common congenital and acquired chest wall deformity, occurring in approximately 1 in every 300–400 births. It shows a male predominance (approx. 4:1 ratio). Depending on the degree of the malformation, manifestation may be noticed at birth, during infancy or during/after a pubertal growth spurt. Commonly held beliefs include the opinion that PE deformity is “only a cosmetic problem”, PE patients do not suffer from relevant clinical symptoms, and open surgical repair is the only available method to correct the defect. For decades, open surgical repair (Ravitch procedure) was the gold standard to correct PE (1). The non-surgical technique of applying suction to the ventral chest wall to elevate the sternum was first described in a textbook of Pediatrics in the early 20th century (2), and taken up in the early 21st century by an engineer, using a vacuum bell (VB) made from silicon (3,4). An essential paradigm shift in the treatment of PE occurred with the introduction of the technique of minimally invasive repair of pectus excavatum (MIRPE) by D. Nuss in 1998 (5). The introduction of MIRPE as well as vacuum bell therapy (VBT), and increasing interest and patient’s self-perception have changed the view on the treatment of PE within the last 15–20 years. An increasing number of pediatric PE patients (<10 years of age) with a mild degree of PE are referred to the outpatient clinic. In many cases of these pediatric patients, the degree of pectus deformity does not immediately warrant surgery, yet patients may benefit from some type of non-surgical treatment. Adolescent and adult patients who refused operative treatment by previously available procedures due to several reasons, now appear at the outpatient clinic and request to be considered for conservative treatment methods. Furthermore, reports on character and number of possible complications associated with the MIRPE (6,7) have made conservative VBT a focus of interest of patients, their parents as well as surgeons.

Since there are no validated guidelines concerning VBT available, we performed an online survey about clinical practice of VBT. This review summarizes the results from our online survey submitted to the members of the Chest Wall International Group (CWIG), and a review of the current English spoken literature focusing on VBT for non-surgical treatment of PE including our own experience with the VBT. A special focus was set on the identification of variables predictive of an excellent outcome. I present this article in accordance with the SURGE reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-23-408/rc).

Methods

An online survey including 26 questions concerning the use of VBT was submitted to all registered CWIG members. A review of the literature was performed in accordance with PRISMA guidelines and included specific terms such as: “vacuum bell”, “chest wall lifter”, “pectus excavatum” and “funnel chest”. The data bases used were: PubMed, Embase, Scopus and MEDLINE, and the first 10 pages of Google Scholar. The search was restricted to English-language publications and human studies. Finally, we summarize our own results from previously published studies.

The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). Our own studies were approved by the local ethics committee (reference numbers: 2008, 2016-02211, and 2017-00241) and individual consent for this retrospective analysis was waived.

Results

Online survey

The Chest Wall International Group (www.cwig.info) aims to advance the science and art of chest wall surgical and non-surgical procedures through research, education and collaboration with our interdisciplinary and international group of experts. Established in 2008, CWIG has grown to a vast network of over 350 distinguished members spanning seven continents including more than 200 departments. An online survey comprised 26 questions concerning the use of VBT as well as some demographic information. The invitation-link to the survey was submitted to all registered CWIG members by email. Approximately 5–6 minutes were needed to complete the survey, which was open for four months. Non-responders received one reminder after 3 weeks, again via email. No incentives were provided. Since there are many institutions with two and more pectus surgeons within the same unit, we accepted one reply per institution.

Pectus surgeons from 47 different institutions from all around the world answered the survey, with the majority representing pediatric surgeons (56.5%) and thoracic surgeons (41.3%). Table 1 shows further details. More than two thirds of pectus surgeons were more than 10 years in practice (>20 years in practice: 48%; >10 years in practice: 30%). Eighty-one percent of pectus surgeons are working in a specialized chest wall unit. For surgical repair of PE, MIRPE was the most common used technique (91.5%), followed by open repair (modified Ravitch procedure: 40%) and other techniques. 4.3% answered to provide no surgery for their pectus patients (Table 1). VBT was provided by 72.4% whereas 27.6% did not offer VBT due to different reasons (Table 1).

Table 1

Vacuum bell therapy—general information

Values
Specialty (47 different institutions)
   Pediatric surgery 56.5%
   Thoracic surgery 41.3%
   Plastic surgery 2.2%
Country/region
   Europe 61.7%
   South America 19.15%
   USA/Canada 8.5%
   Asia 6.4%
   Australia 2.13%
   Africa 2.13%
Do you treat patients with CWDs?
   Under the age of 10 years 51%
   Aged 10 to 20 years 91.5%
   Older than 20 years 64%
Do you offer surgical repair of PE?
   MIRPE 91.5%
   Open repair 40%
   Other techniques 23.4%
   No surgery 4.3%
Do you offer VBT for PE?
   Yes 72.4%
   No 27.6%
    Not available 3 (6.4%)
    Not covered by insurance 3 (6.4%)
    Not convinced 2 (4.2%)
    Not yet started, but want to 1 (2.1%)

CWD, chest wall deformity; PE, pectus excavatum; MIRPE, minimally invasive repair of pectus excavatum; VBT, vacuum bell therapy.

Tables 2,3 summarize details concerning age group, indication/contra-indication, diagnostic work-up before starting VBT, monitoring during VBT and follow-up. The majority of pectus surgeons started within the last 1 to 5 years with VBT in their practice. Pediatric and young adolescent patients represent the dominant age group. Mild degree of PE is reported as the most common indication for VBT (Table 2, Figure 1). Interestingly, approximately 63% apply VBT as alternative to surgical repair, and 44% use VBT as pre-treatment before surgery. Coagulopathies and major cardiac malformations represent the most common contraindications for VBT (Table 2). Diagnostic work-up before starting VBT include in particular non-invasive measures like patient’s history, clinical examination, photo documentation and measurement of depth of PE (Table 2, Figure 2). More than 50% of pectus surgeons recommend to perform VBT 12 to 24 months. Follow-up visits were mostly after 3 to 6 months, including clinical examination, standardized photo documentation and standardized measurement of depth of PE (Table 3, Figure 3). Remarkable that a minority applied CT or MRI scan for routine follow-up assessment (Figure 3). Most centers provide a final follow-up visit 6–12 months after cessation of VBT (Figure 4).

Table 2

Vacuum bell therapy—results part I

Values
When did you start VBT for PE?
   Less than 1 year ago 13%
   1 to 5 years ago 41%
   6 to 10 years ago 28%
   More than 10 years ago 18%
To which age group do you apply VBT?
   Under the age of 10 years 59%
   10 to 15 years of age 72%
   16 to 20 years of age 33%
   Older than 20 years of age 23%
Indication to apply VBT
   Mild degree of PE 79.1%
   Alternative to surgical repair 62.8%
   Patient under the age of 10 years 58.15%
   Pre-treatment before surgical repair 44.2%
Contra-indication to apply VBT
   Coagulopathies 72.5%
   Major cardiac malformations 60%
   Marfan syndrome 32.5%
   Previous cardiac surgery 30%
   Skeletal disorders 27.5%
Diagnostic workup before starting VBT
   Patient’s history 90%
   Clinical examination 90%
   Photo documentation 80%
   Measurement of depth of PE 77.5%
   Body weight/height 60% (each)
   Echocardiography 50%
   Assessment of negative pressure 40%
   CT scan/MRI 35%
Measurement of depth of PE
   Patient in upright position 52.4%
   Patient in supine position 54.8%
   Patient in expiration 31%
   Patient in inspiration 19%
Diagnostic workup during VBT
   Clinical examination 90%
   Measurement of depth of PE 86%
   Photo documentation 74%
   Duration of daily application time 40.5%
   Body weight/height 30% (each)

PE, pectus excavatum; VBT, vacuum bell therapy; CT, computed tomography; MRI, magnetic resonance imaging.

Table 3

Vacuum bell therapy—results part II

Values
How long do you recommend to use VBT?
   12 months 37.5%
   18 months 15%
   24 months 20%
   More than 24 months 20%
How often do you see patients under VBT?
   Every 3 months 40%
   Every 6 months 21%
   Every 6 weeks 18.6%
   Every 12 months 9.3%
How often do you see patients after cessation of VBT?
   After 6 months 42.5%
   After 3 months 30%
   After 12 months 27.5%
   More than 12 months after cessation 15%
   Never 10%
How do you define success of VBT?
   Decreasing depth of PE 75%
   Complete correction of PE 55%
   Increasing negative pressure 7.5%
When do you stop application of VBT?
   Significant improvement of PE 75.86%
   Decreasing motivation 58.6%
   Patients/parents decision 62.1%
   Complete correction of PE 47.5%
   Improvement of PE 27.5%
How many of your patients stopped VBT early?
   Less than 10% 43.6%
   10–25% 30.8%
   26–50% 10.3%
   More than 50% 15.4%
Did you observe any complication during VBT?
   No complication 71.8%
   Complications (redness/hematoma, local skin irritation/dermatitis) 28.2%

PE, pectus excavatum; VBT, vacuum bell therapy.

Figure 1 Indication for VBT. VBT, vacuum bell therapy; PE, pectus excavatum.
Figure 2 Diagnostic work-up before starting VBT. VBT, vacuum bell therapy; CT, computed tomography; MRI, magnetic resonance imaging; ECG, electrocardiogram; PE, pectus excavatum.
Figure 3 Diagnostic work-up during vacuum bell therapy. PE, pectus excavatum; CT, computed tomography; MRI, magnetic resonance imaging.
Figure 4 Follow-up after cessation of VBT. VBT, vacuum bell therapy.

Duration of application was recommended for at least 12 months (37.5%) to more than 24 months (20%). Application without any complication was reported by 71.8%, 28.2% observed minor complications like local redness, hematoma, local skin irritation and/or localised dermatitis (Table 3). Success of treatment was defined as decreasing depth of PE in 75% and complete correction of PE in 55%, respectively (Table 3). As a consequence, 75.86% of pectus surgeons stopped VBT when significant improvement was observed. However, the second most common reason (62.1%) to stop VBT was decreasing motivation followed by patients and or parents’ decision to stop VBT (58.6%) (Table 3).

Approximately 71.8% of patients and/or parents were satisfied with duration and success of VBT, which is in contrast to the assessment of pectus surgeons (68.4% were satisfied). Nevertheless, 90.5% of pectus surgeons considered VBT as a useful tool for treatment of PE, and 93% requested guidelines for standardization of VBT (Table 4).

Table 4

Vacuum bell therapy—results part III

Values
Were patients/parents satisfied with duration and success of VBT?
   Yes 71.8%
   No [no (significant) improvement of PE; recurrence after decreasing application/cessation] 28.2%
Were you/your team satisfied with duration and success of VBT?
   Yes 68.4%
   No [no (significant) improvement of PE; duration too long; no follow-up] 31.6%
Do you consider VBT as a useful tool in the treatment of PE?
   Yes 90.5%
   No (not enough effective) 9.5%
Do you consider that CWIG should promote guidelines for the standardization of VBT?
   Yes 93%
   No 7%

PE, pectus excavatum; VBT, vacuum bell therapy; CWIG, Chest Wall International Group.

Review of the current literature

A total of 62 studies reporting on conservative treatment of PE using the VB could be identified. Interestingly, from 2005 to 2014, eleven studies were identified, which is in contrast to the period between 2015 and 2022 with 51 published papers. Ten studies (16.13%) described the effectiveness of the VB to elevate the sternum as a method of treatment, but did not analyze a specified patient population. 8 studies with an abstract in English had to be excluded, since the manuscript was in French (2), Chinese, Dutch, German, Russian, Spanish or Turkish (1 each), respectively (8-15). Furthermore, 4 articles summarized relevant, but partial aspects of previously published retrospective studies (16-19). A case report and a retrospective study including 30 patients reported on the assessment of cardiac function before and during temporary sternal elevation using the VB (20,21). Three studies focused on non-invasive methods for initial assessment and follow-up monitoring during VBT describing technical details (22-24). Two case reports described VBT as effective in conservative treatment of thoracic trauma, in one patient with polytrauma that included anterior chest flail (25) as well as in one pediatric patient presenting with isolated sternal fracture (26). Alaca et al. analysed the effect of a standardized physiotherapy program applied in addition to VBT (27) and confirmed that their standardized rehabilitation program applied simultaneously with VBT had a positive effect on the final outcome.

Eight studies report on the intraoperative use of the VB for sternal elevation to increase safety of MIRPE and visibility during a robotic procedure, respectively (4,28-34). Since the manufacturer does not provide an approved sterilization program for the device, the intraoperative use has to be classified as “off-label use”. However, different reasonable and approved methods are available and reported for intraoperative application.

Seventeen studies presented detailed information about VBT and are listed in Table 5 (4,28,35-49). Two studies included a prospective kept data base, but the analysis was retrospective (39,43). Again, the majority of these studies were published after 2015. Before 2015, clinical trials and retrospective studies, respectively, reported on preliminary results including a heterogeneous study population. Starting into the second decade with increasing clinical application, a couple of technical devices were introduced to increase safety of VBT and enable objective assessment. We introduced a measurement device for quantitative assessment of applied negative pressure (39). Toselli et al. extended this idea and developed a vacuometer which is provided for application in home environment (45). Our group developed a prototype of an electronic device for objective assessment of sternal elevation in correlation to applicated pressure (42). Deng et al. used a novel three dimensional (3D) printed VB device in 42 patients (44). Most importantly, there was one study comparing VBT to MIRPE (46). Jung et al. demonstrated that VBT showed comparable outcomes in comparison to MIRPE (46). However, we could not identify any randomized and/or prospective studies comparing conservative treatment vs. surgical repair and/or conservative treatment vs. no specific therapy.

Table 5

Studies presenting detailed information about vacuum bell therapy

Study Year No. of patients Age (years) Follow-up (months)
Schier et al. (4) 2005 60 14.8 [6.1–34.9] 10 [2–18]
Haecker et al. (28) 2006 34 17.8 [6–52] 10.4 months duration of treatment
Haecker (35) 2011 93* 17.8 [3–61] 16 [3–60]
Haecker (36) 2011 133* 16.21 [3–61] 16 [3–60]
Lopez et al. (37) 2016 73 Adults/children 13 [6–24]
Haecker et al. (38) 2016 300* 16.28 [2–61] 27.6 [1–73]
Haecker et al. (39) 2016 434* 16.2 [2–61] 27.9 [1–76]
Togoro et al. (40) 2018 30 8–35 NA
Obermeyer et al. (41) 2018 115 12.7 [4–23] 12 [4–48]
Sesia et al. (42) 2018 53 14 [6–20] NA
St-Louis et al. (43) 2019 31 14 [6–21] 18 [12–24]
Deng et al. (44) 2020 42 3.6 11.1
Toselli et al. (45) 2021 54* 12.6±6.0 13.2
Jung et al. (46) 2021 33 16.48±8.21 12
Yi et al. (47) 2021 63 15.4±6.23 12
Luo et al. (48) 2022 139 4.6±1.7 9
Toselli et al. (49) 2022 186* 11.9±6.5 24

Data are presented as median, median [range] or mean ± standard deviation, unless otherwise indicated. *, cumulative study building on previous patients group. NA, not applicable.

The studies listed on Table 5 show heterogeneity concerning patients’ age for VBT, selection criteria/indication, VBT protocol, length of VBT and follow-up, and in particular definition of success and completion of VBT, respectively. A generally applied standardized VBT protocol is still not available. We observe age specific differences of success. Therefore, interpreting the presented results across groups is difficult. Summarizing the results of these studies (Table 5), VBT as a non-operative treatment of PE proved to be safe and efficient in carefully selected PE patients. Variables predicting a good to excellent outcome include a mild symmetric PE, chest wall depth <1.5 cm, age <11 years, remaining chest wall flexibility, daily application of the VB more than 2 hours, and VB use over 12 consecutive months. Figures 5,6 show two of these patients before and after treatment.

Figure 5 A 5-year-old girl before VBT (A, depth of PE: 1.7 cm), after 9 months (B, depth of PE: 0.4 cm) and 2 years after cessation of VBT (C, depth of PE: 0.4 cm). PE, pectus excavatum; VBT, vacuum bell therapy.
Figure 6 A 10-year-old boy before VBT with concomitant costal flaring (A, depth of PE: 1.8 cm) and 3 months after cessation of VBT (B, depth of PE: 0.5 cm). PE, pectus excavatum; VBT, vacuum bell therapy.

Of course, we have to notice and pay attention to potential side effects of VBT. Complications and side effects include petechiae, local pain and back pain, thickening and/or darkening of the skin, blistering and paresthesia of the upper extremity during application. None of these complications were permanent and severe. With modification of the daily application, or a short pause if needed, cessation of all side effects could be achieved.

A recently published study stated that the effect of VBT is predominantly because of thickening of the chest wall by increasing pre-sternal adipose tissue (50). The authors pointed out that the perceived correction of PE is due to localised fat tissue enlargement and not due to sternal elevation (50). This observation was confirmed by Tedde (51). Of course, this observation has to be noticed seriously. However, some details of Furuta’s study have to be noted. They include only a small number of non pediatric patients, patients selection is unclear, and they did not provide a recommended treatment protocol (50). Toselli’s and our reply corroborated the importance of proper patient selection and proper treatment protocols for VBT (51).

Discussion

Albeit the deformity is noticeable at birth in the majority of PE patients, most pediatric PE patients present with a mild degree of PE, which is usually stable during childhood. However, what we observe and have to realize is the fact that there is an increase of PE severity in nearby all patients during a pubertal growth spurt. This observation implies that one should not wait for worsening of the deformity, but to consider starting a less invasive treatment option earlier, before puberty. The preliminary results of our survey as well as from this review of the current literature including our own experience confirm that in particular pediatric PE patients and young adolescents may qualify for VBT and benefit from this conservative treatment method. In case no specific treatment is performed before pubertal growth spurt starts, we recommend close observation of these patients until after puberty.

In the first description of VBT more than 100 years ago, a glass bell was used applying a vacuum to elevate the sternum in a PE patient (2). Although described a long time ago, the routine use of the VB technique could not be established within the last century due to different reasons. The technique was taken up in the early 21st century by an engineer, using a VB made from silicon (3,4). Pilot studies describing the use of VBT in PE patients have been published more than 15 years ago, describing promising initial results in a few patients (4,28,35). CT-scans showed that the device lifted the sternum and ribs immediately (4,40). The effect of the VB was also confirmed using the device for sternal elevation during the MIRPE procedure (4,28-34). The use of the VB led to a clear elevation of the sternum and this was confirmed by thoracoscopy.

Within the last 10 years, an increasing number of studies reported on an increasing number of patients (Table 5). The first systematic retrospective study summarizing the results of 133 patients was published in 2011 (36). Our online survey confirmed that today VBT is established and applied worldwide in chest wall units. More than 70% of pectus surgeons who answered our survey provide VBT as part of their specialized treatment concept. This is important since, according to others and our own experience, approximately 80% of PE patients applied for conservative treatment using the VB whereas only 20% underwent surgical repair (16,39). Even if the studies listed in table 5 show heterogeneity in different aspects like patients age, selection criteria, treatment protocol, etc., the results of these studies identified variables predicting a successful outcome. Pediatric and young adolescent patients represent the dominant age group to apply VBT. Mild degree of PE is reported as the most common indication for VBT. In contrast, PE patients who presented with asymmetric and/or deep PE, seemed to show a less successful outcome. Obermeyer et al. reported on an excellent outcome for patients ≤11 years, chest wall depth ≤1.5 cm, chest wall flexibility, and VB use over 12 consecutive months (41). St. Louis et al. identified remaining chest wall flexibility and daily application of the VB more than 2 hours as additional relevant factors (43). Chest wall depth ≤2.0 cm, patients age ≤11 years and patients’ motivation as variables predicting successful outcome could be identified in our own cumulative studies (36,39,52). To the best of our knowledge, until today there are no standardized protocols available for detailed patients’ selection criteria, treatment schedule, follow-up etc. for VBT. The results of our survey as well as from this review confirm a broad consensus concerning the above-mentioned criteria and a VBT treatment algorithm. The vital necessity to provide validated guidelines concerning VBT is confirmed by the fact that 93% of pectus surgeons requested guidelines for standardization of VBT. Based on the conclusion of this review, we are encouraged to create a draft. A consensus conference may enable us to determine such guidelines.

Albeit the number of included VBT patients increased within the last decade and many authors followed their own standardized detailed treatment algorithm, no randomized and/or prospective studies comparing conservative treatment vs. surgical repair and/or conservative treatment vs. no specific therapy have been performed to this day. We could identify one study comparing the results of VBT to MIRPE (46). Jung et al. performed a retrospective study including 57 patients who underwent MIRPE or performed VBT. They analyzed the change between pre-treatment Haller index (HI) and post-treatment HI, in the MIRPE group after pectus bar removal. The post-treatment HI between the 2 groups did not show statistical significance for immediate post-treatment and 1-year post-treatment. However, the degree of HI improvement was significantly greater in the MIRPE group (46). The statistical approach used in this study is debatable, and as a consequence we may challenge the authors conclusions. Even if it might be difficult and a real challenge to design an IRB accepted study protocol, we should be encouraged and have the obligation to create a study protocol for a randomized prospective study comparing the results of VBT to MIRPE.

Of course, as in any established treatment method, there is no effect without potential side effect. Complications and side effects reported in the survey as well as in literature include petechiae, local pain and back pain, thickening and/or darkening of the skin, blistering and paresthesia of the upper extremity during application. None of these complications were permanent and classified as severe (4,28,35-49). With modification of the daily application, or a short pause if needed, cessation of all side effects could be achieved. Neither in the survey nor the literature listed in table 5, the phenomena of localized thickening of the chest wall by increasing pre-sternal adipose tissue was observed, as reported by Furuta et al. (50) and confirmed by Tedde (51). The authors pointed out that the perceived correction of PE is due to localised fat tissue enlargement and not due to sternal elevation (50,51). Of course, this observation has to be noticed seriously. However, as mentioned above, certain details of Furuta’s study should be noted before drawing conclusions. Furthermore, we published another study including 27 patients, who underwent VBT for 17 months. Because of lack of permanent treatment effect of VBT, they underwent surgical repair. Interestingly, preoperative imaging did not demonstrate pre-sternal fat tissue enlargement (53).

Proper selection of patients and proper treatment protocol for VBT is mandatory. Concerning the relevance of chest wall flexibility, we could confirm that the applied differential negative pressure required to the lift the sternum is lower or higher dependent on patient’s age (42,54). Furthermore, there was a statistically significant correlation between depth of PE and patient’s age. That confirms patients’ age as a relevant variable for a successful outcome and corroborate the recommendation the see PE patients at younger age, early before puberty, and consider to start specific therapy early or before puberty, respectively. Haje et al. reported on similar experience applying not VBT but another conservative treatment option including bracing and exercises (55).

Additionally, measurement of the applied negative pressure as reported previously by us (39) is helpful. Toselli et al. developed a vacoumeter which is provided for application in home environment (45). However, in many institutions the measurement device is still only available for the outpatient clinic visit, and not for the PE patient during daily VBT at home. More advanced techniques such as a chip to monitor the daily application time, intensity of applicated negative pressure and data transfer via Bluetooth are warranted.

Limitations

Our online survey was submitted to the members of CWIG, a pre-selected group of pectus experts. We did not analyse in detail the group of non-responders. The presented review of the current literature included only English spoken literature, focusing on VBT for non-surgical treatment of PE. Furthermore, VBT for conservative treatment of PE has its limitations. As already mentioned above, even though there is a broad consensus concerning indication/contraindication and treatment recommendations for VBT, there are no standardized guidelines available today. After delivering the device to the patient and instruction of daily application, there is no possibility to monitor the application (e.g., frequency and duration of daily application, intensity of vacuum, etc.) at home. We have to rely on self-reported use of the VB at home with regard to daily application time and applicated pressure. Positioning of the device and intensity of the negative pressure may vary from day to day. Furthermore, objective assessment of success of VBT is still difficult, and also the definition of success may vary according to individuals. Long-term outcome including follow-up more than 20 years is still missing. Complications and side effects as reported above have to be noticed. Furthermore, concomitant malformations like asymmetry and/or costal flaring may affect the efficacy of the treatment method. The importance of patients age, severity of the defect and flexibility of the chest wall were already mentioned.

Nevertheless, the results of our online survey and the review of the current literature enable us to provide a draft for validated guidelines concerning all aspects of VBT including indication/contraindication, optimal age to start VBT, diagnostic work-up before and under treatment, duration of daily application, frequency and program of follow-up visits, duration of treatment, etc.

Conclusions

In conclusion, VBT seems to be safe and has been established as an additional useful tool in specific treatment of PE patients. Identified variables let us recommend starting the application in children under the age of 10 years, if needed. VBT is a complement in the specific treatment of PE patients, applicable to a significant majority of PE patients, and may allow some patients with PE to avoid surgery. Even if guidelines for standardization of VBT are still missing, the results of our online survey and the review of the current literature provide validated variables to establish guidelines. Furthermore, a randomized prospective study comparing the results of VBT to MIRPE might enable us to assess and define clear criteria for meticulous patients’ selection. Potential side effects of VBT have to be noticed and monitored seriously.

Acknowledgments

Funding: None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, Journal of Thoracic Disease, for the series “Minimally Invasive Treatment of Pectus Deformities”. The article has undergone external peer review.

Reporting Checklist: The author has completed the SURGE reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-23-408/rc

Data Sharing Statement: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-23-408/dss

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-23-408/prf

Conflicts of Interest: The author has completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-23-408/coif). The special series “Minimally Invasive Treatment of Pectus Deformities” was commissioned by the editorial office without any funding or sponsorship. F.M.H. served as the unpaid Guest Editor of the series. The author has no other conflicts of interest to declare.

Ethical Statement: The author is 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.The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). Our own studies were approved by the local ethics committee (reference numbers: 2008, 2016-02211, and 2017-00241) and individual consent for this retrospective analysis was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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Cite this article as: Haecker FM. 20 years clinical application of the vacuum bell for conservative treatment of pectus excavatum—past, present, future. J Thorac Dis 2024;16(8):5285-5298. doi: 10.21037/jtd-23-408

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