Monitoring the effectiveness of the vacuum bell during pectus excavatum treatment: Technical innovation

Abstract Background The vacuum bell (VB) is a valid and the only non-invasive treatment for pectus excavatum (PE). To elevate the sternum the patient himself creates a differential negative pressure inside the VB using a hand pump. A distance and differential pressure measuring device (DPMD) enables us for the first time to assess objectively those parameters. Methods After approval by the institutional review board, 53 patients recruited from our outpatient clinic were included in this retrospective study and distributed into three groups (group 1 aged 6 to 10years; group 2 aged 11 to 15years; group 3 aged 16 to 20years). Sternum elevation and differential negative pressure inside the VB compared to atmospheric pressure were assessed with the DPMD, a device developed by engineers at the University of Applied Sciences, Northwestern Switzerland. Pressure-elevation curves were recorded during VB therapy. For statistical comparison of the groups, analysis of variance was used. Post-hoc analysis was performed using the Tukey–Kramer test. A p -value of less than 0.05 was considered to be statistically significant. Results The VB therapy was monitored in 53 children (39 males, 14 females) aged from 6 to 20years (average, 14years). Relationships were established between the differential negative pressure inside the vacuum bell, the elevation of the sternum, and the patient's age. The younger the patient, the lower is the differential negative pressure difference required to obtain a complete elevation of the sternum. Patient's age, weight, the pectus depth, the differential negative pressure inside the VB, and the elevation of the sternum were correlated. When comparing the depth 25 of the pectus excavatum to the patient's age, a statistically significant difference was verified between the groups 3 and 1 ( p=0.0291 ) and 3 and 2 ( p=0.0489 ). The older the patient, the deeper is the pectus excavatum. However, no statistically significant difference between the groups was found when comparing the sternum elevation to the patient's age ( p=0.4574 ) and the elevation to pressure ratio to the patient's age ( p=0.8048 ). The sternum elevation and the elevation to pressure ratio are independent of the patient's age. Conclusions DPMD supplies objective data of the elevation of the sternum and the related pressure inside the VB during its application. Correlation between the patient's age, the elevation of the sternum and the pressure inside the VB were demonstrated, but additional data are needed to better understand their relationship and their impact in the treatment of PE by VB. Study type Diagnostic Study. Level of evidence IV.