In the present meta-analysis and systematic review, we found that compared to traditional chest drainage system, digital chest drainage system reduced the risk of incidence of prolonged air leak, and shortened the duration of chest drainage and length of hospital stay in patients after pulmonary resection.
PAL remains a common complication after pulmonary resection. Several studies had shown that PAL was associated with longer hospital stay and more hospital costs [18, 19]. It was also suggested that PAL was associated with an increased rate of postoperative morbidity, such as empyema, fever and pneumonia [20]. The risk of PAL can be predicted by several preoperative and intraoperative factors such as a low predicted postoperative forced expiratory volume in 1 s (ppoFEV1), pleural adhesions and upper lobectomy [20]. Besides, improvement in postoperative chest drainage system is an important approach to reduce PAL rate and accelerate the recovery.
There are several advantages of digital chest drainage system in management of patients after pulmonary resection. First of all, the digital system can regulate its suction pressure according to the condition in the pleural cavity, and the pleural pressure can be maintained at a preset level within 0.1 cmH2O. It had been shown that wide oscillation in early postoperative pleural pressure was associated with a higher incidence of PAL [21]. Thus, the digital chest drainage system may promote the sealing of air leaks by stabilizing the pleural pressure with minimal oscillation. Second, the digital system measures the extent of air leak objectively, and the historical data can be exported and reviewed. Thus, the digital chest drainage system reduces the interobserver variability, and helps medical personnel decide when to remove the chest tube more accurately. It had been proved by several clinical trials that digital chest drainage system not only reduced interobserver variability between different groups of medical staffs (surgeons, residents and nurses) [22], but also between surgeons with comparable experience [23]. The reduced interobserver variability leads to shorter duration of chest drainage and length of hospital stay. Furthermore, the digital system facilitates an early patient mobilization and improves postoperative physiotherapy, which can reduce the risk of secretion and pneumonia, and facilitates pulmonary re-expansion [14]. Finally, the digital device such as the Thopaz chest drain system (Medela Switzerland) can serve as a portable suction unit, and patients can be discharged earlier with this system [24].
Since the traditional chest drainage system is subjective and inaccurate in judging air leak, there is risk of removing the chest tube prematurely. In that situation, chest tube reinsertion is needed. A clamping test had traditionally been taken to prevent this error. It had been suggested by Takamochi et al. that over 50% patients underwent clamping test before removing the chest tube in the traditional group, while none clamping test was taken in the digital group [17]. It had also been shown by Gilbert et al. that chest tube reinsertions for worsening pneumothorax or subcutaneous emphysema after chest tube removal occurred only in the traditional group, none chest tube reinsertion happened in the digital group [13].
Some clinicians hypothesized that the intermittent suction pressure provided by the digital system may reduce the pressure gradient for fluid filtration across the pleural membrane and lighten the inflammatory response. However, the study conducted by Waele et al. did not find such effect [16].
Apart from objective outcomes, subjective outcome (such as patient satisfaction) is also important in evaluating chest drainage system. The multicenter study conducted by Pompili et al. evaluated the patient satisfaction with digital chest drainage system, and the result suggested that patients in the digital group had a more positive perception of the chest drainage, which was associated the comfort, portability and convenience of the digital system [12].
Recently, a meta-analysis of randomized controlled trials conducted by Zhou et al. suggested that digital chest drainage following pulmonary surgery reduced the duration of chest tube placement, length of hospital stay, air leak duration and postoperative cost [25]. Compared to their study, the present systematic review focused on patients after pulmonary resection, and obtained similar results. Another recent study discussed the postoperative air leak pattern in lung cancer patients after pulmonary resection with the help of digital chest drainage system, which suggested that the detailed air leak pattern can be used to predict the duration of air leakage and chest tube drainage [26].