INSPIRA: study protocol for a randomized-controlled trial about the effect of spirometry-assisted preoperative inspiratory muscle training on postoperative complications in abdominal surgery

Abstract

Background: Rehabilitation strategies after abdominal surgery enhance recovery and improve outcome. A cornerstone of rehabilitation is respiratory physiotherapy with inspiratory muscle training to enhance pulmonary function. Pre-habilitation is the process of enhancing functional capacity before surgery in order to compensate for the stress of surgery and postoperative recovery. There is growing interest in deploying pre-habilitation interventions prior to surgery. The aim of this study is to assess the impact of preoperative inspiratory muscle training on postoperative overall morbidity. The question is, whether inspiratory muscle training prior to elective abdominal surgery reduces the number of postoperative complications and their severity grade.

Methods: We describe a prospective randomized-controlled single-centre trial in a tertiary referral centre. The primary outcome is the Comprehensive Complication Index (CCI) at 90 days after surgery. The CCI expresses morbidity on a continuous numeric scale from 0 (no complication) to 100 (death) by weighing all postoperative complications according to the Clavien-Dindo classification for their respective severity. In the intervention group, patients will be instructed by physiotherapists to perform inspiratory muscle training containing of 30 breaths twice a day for at least 2 weeks before surgery using Power®Breathe KHP2. Depending on the surgical schedule, training can be extended up to 6 weeks. In the control group, no preoperative inspiratory muscle training will be performed. After the operation, both groups receive the same physiotherapeutic support.

Discussion: Existing data about preoperative inspiratory muscle training on postoperative complications are ambiguous and study protocols are often lacking a clear design and a clearly defined endpoint. Most studies consist of multi-stage concepts, comprehensively supervised and long-term interventions, whose implementation in clinical practice is hardly possible. There is a clear need for randomized-controlled studies with a simple protocol that can be easily transferred into clinical practice. This study examines the effortless adjustment of the common respiratory physiotherapy from currently postoperative to preoperative. The external measurement by the device eliminates the diary listing of patients' performances and allows the exercise adherence and thus the effect to be objectively recorded.

Trial registration: ClinicalTrials.gov NCT04558151 . Registered on September 15, 2020.

Keywords: Abdominal surgery; Inspiratory muscle training; Overall morbidity; Postoperative complications; Pre-habilitation; Preoperative; Respiratory complications; Respiratory physiotherapy.

Fig. 1

Sensitivity of the sample size with regard to the expected effect size, θ, given a within group standard deviation of 10. An example is shown for θ =6 and a power of 90 %. The curves are smoothed and shown for illustration only