Corresponding author. Department of Thoracic Surgery, West China Hospital, Sichuan University, No. 37, Guoxue Alley, Chengdu, Sichuan 610041, China. Tel: +86-28-85422494; fax: +86-28-85422494; e-mail: lunxu_liu@aliyun.com (L. Liu).
Search for other works by this author on:Jian Zhou and Nan Chen two authors contributed equally to this work.
Interactive CardioVascular and Thoracic Surgery, Volume 28, Issue 1, January 2019, Pages 29–36, https://doi.org/10.1093/icvts/ivy216
19 July 2018 30 January 2018 Revision received: 07 June 2018 12 June 2018 19 July 2018Jian Zhou, Nan Chen, Yang Hai, Mengyuan Lyu, Zihuai Wang, Yuanjing Gao, Long Pang, Hu Liao, Lunxu Liu, External suction versus simple water-seal on chest drainage following pulmonary surgery: an updated meta-analysis, Interactive CardioVascular and Thoracic Surgery, Volume 28, Issue 1, January 2019, Pages 29–36, https://doi.org/10.1093/icvts/ivy216
Navbar Search Filter Mobile Enter search term Search Navbar Search Filter Enter search term Search
The decision to apply simple water-seal drainage or the addition of an external suction to the simple water-seal drainage following pulmonary surgery is made based on the surgeon’s experience or preference and has remained controversial. This meta-analysis aimed to assess the effects of the addition of suction to simple water-seal on the postoperative outcomes.
PubMed, EMBASE and Web of Science were searched from their inception to 30 August 2017. The risk ratio and the weight mean difference were calculated for dichotomous and continuous outcomes, respectively, each with 95% confidence intervals (CIs). The heterogeneity and risk of bias were also assessed.
A total of 10 randomized controlled trials enrolling 1601 patients were included. Overall, compared with simple water-seal, the addition of external suction reduced the occurrence of postoperative pneumothorax (risk ratio 0.35, 95% CI 0.13–0.93; P = 0.04) and other cardiopulmonary complications (risk ratio 0.65, 95% CI 0.48–0.89; P = 0.008), and increased the duration of chest tube drainage (weight mean difference 0.92 days, 95% CI 0.04–1.81, P = 0.04). However, the effect difference between the 2 groups was not significant regarding air leak duration, length of hospital stay and the occurrence of prolonged air leak. The stability of these studies was strong. No evidence of publication bias was detected.
CONCLUSIONSThe addition of suction to simple water-seal made no difference to air leak duration, hospital stay or the occurrence of prolonged air leak following pulmonary surgery. In patients where there is concern about a residual or increasing pneumothorax, the addition of suction may be applied selectively.
The essential principles of a chest drainage system are to permit drainage of fluid and air, to eliminate the residual pleural space, facilitate lung re-expansion and to maintain negative pressure [ 1].
There are 2 different concepts of chest tube management currently in use: simple water-seal (non-suction drainage) or water seal with the addition of external suction (suction drainage) [ 2]. The choice is made based on the clinician’s preference without much consideration of sound evidence [ 3]. Some hold the idea that the addition of suction might reduce the air leak and, therefore, accelerate lung rehabilitation, whereas other surgeons assert that simple water-seal could shorten the air leak duration after pulmonary surgery [ 4–6]. The difference in opinion is related to whether there is an advantage in the addition of external suction to water seal. There can be no doubt that mechanistical suction results in more rapid removal of air and fluid and re-expansion of the lung. The question that remains is which provides the better overall outcome for the patient [ 4]. We conducted this further meta-analysis to answer this question.
The articles were searched by 2 independent reviewers in the PubMed, EMBASE and Web of Science from their inception to 30 August 2017 with the following terms: ‘lung surgery’, ‘lung resection’, ‘pulmonary surgery’, ‘pulmonary resection’, ‘lobectomy’, ‘segmentectomy’, ‘wedge resection’ AND ‘chest drain’, ‘chest tube’, ‘chest drainage’, ‘air leak’, ‘air leakage’, ‘suction’. Both reviewers also manually searched the reference lists of eligible studies to identify potential relevant publications.
For inclusion, the studies need to (i) be randomized controlled trials; (ii) focus on patients who had undergone pulmonary surgery and (iii) compare the addition of suction drainage and simple water-seal. The studies were excluded if they met one of the following criteria: (i) essential information was incomplete, (ii) were conference abstracts, letters, review, case reports and animal experiments and (iii) the article was not written in English. Two researchers assessed the suitability of studies independently. Any disagreement was solved by further discussion, and if necessary, a third assessor would arbitrate.
The risk of bias of each eligible study was evaluated according to the Cochrane Handbook for Systemic Reviews of Interventions. The criteria for evaluating the risk of bias includes sequence generation and concealment of allocation (selection bias), blinding of participants and personnel (performance bias), blinding of outcome assessors (detection bias), incomplete outcome data addressed (attrition bias), free of selective reporting (reporting bias) and other bias. Also, this work was independently assessed by 2 reviewers (J.Z. and N.C.). Any disagreement was solved by consensus.
The following information was extracted from each eligible study: the first author, publication year, country, disease type, surgery type, grade of air leak, number of subjects, pressure of suction and postoperative outcomes including air leak duration, length of hospital stay, the duration of chest tube drainage, the occurrence of prolonged air leak and postoperative pneumothorax.
A total of 1827 references were found from the initial search. After 2 independent researchers screened the titles and abstracts, and if necessary, found full text to confirm, only 10 randomized controlled trials [ 5–14] recruiting 1568 patients were included. Included articles were published between 2001 and 2016. The sample size of these studies ranged from 31 to 500. Most researchers recruited participants who underwent lung resection for lung disease, whereas Ayed et al. [ 8] enrolled patients who underwent video-assisted thoracic surgery for primary spontaneous pneumothorax (PSP). The drainage systems used were conventional water-seal chest drainage systems except Leo et al. [ 12] and Brunelli et al. [ 9] who applied an electronic drainage system, which could record air leaks digitally. The postoperative outcome parameters included the occurrence of prolonged air leak and postoperative pneumothorax, the duration of chest tube drainage, air leak duration and length of hospital stay. The PRISMA flow diagram of literature retrieval is shown in Fig. 1. The main characteristics of the included studies are presented in Table 1.
Main characteristics of the included randomized controlled trials
| Study . | Sample size . | Ethnicity . | Participant . | Disease . | Number of tubes . | Initial suction . | Suction pressure (cmH2O) . | Drainage system . | Definition of PAL (days) . | Drainage threshold of removal (ml/day) . |
|---|---|---|---|---|---|---|---|---|---|---|
| Alphonso et al. [ 7] | 239 | White | Lung surgery | Lung disease | 1–2 | No | −20 | Regular | >6 | |
| Ayed et al. [ 8] | 100 | White | VATS | PSP | 1 | No | −20 | Regular | >5 | |
| Brunelli et al. [ 5] | 145 | White | Lobectomy | Lung cancer | 2 | Yes | −20 | Regular | >7 | |
| Brunelli et al. [ 9] | 100 | White | Lobectomy | Lung cancer | 1 | NA | −11 to −20 | Digital | >7 | NA |
| Cerfolio et al. [ 10] | 33 | Mixed | Lung surgery | Lung cancer | NA | NA | −20 | Regular | >5 | NA |
| Gocyk et al. [ 6] | 294 | White | Lung surgery | Lung disease | 1–2 | Yes | −20 | Regular | >7 | |
| Kakhki et al. [ 11] | 31 | White | Lung surgery | Lung disease | 1 | Yes | −10 to −18 | Regular | >7 | NA |
| Leo et al. [ 12] | 500 | White | Lung resection | Lung disease | 1–2 | Yes | −15 | Digital | >6 | |
| Marshall et al. [ 13] | 68 | Mixed | Lung resection | Lung disease | NA | Yes | −20 | Regular | >8 | |
| Prokakis et al. [ 14] | 91 | White | Lobectomy | Lung cancer | 2 | No | −15 to −20 | Regular | >7 |
| Study . | Sample size . | Ethnicity . | Participant . | Disease . | Number of tubes . | Initial suction . | Suction pressure (cmH2O) . | Drainage system . | Definition of PAL (days) . | Drainage threshold of removal (ml/day) . |
|---|---|---|---|---|---|---|---|---|---|---|
| Alphonso et al. [ 7] | 239 | White | Lung surgery | Lung disease | 1–2 | No | −20 | Regular | >6 | |
| Ayed et al. [ 8] | 100 | White | VATS | PSP | 1 | No | −20 | Regular | >5 | |
| Brunelli et al. [ 5] | 145 | White | Lobectomy | Lung cancer | 2 | Yes | −20 | Regular | >7 | |
| Brunelli et al. [ 9] | 100 | White | Lobectomy | Lung cancer | 1 | NA | −11 to −20 | Digital | >7 | NA |
| Cerfolio et al. [ 10] | 33 | Mixed | Lung surgery | Lung cancer | NA | NA | −20 | Regular | >5 | NA |
| Gocyk et al. [ 6] | 294 | White | Lung surgery | Lung disease | 1–2 | Yes | −20 | Regular | >7 | |
| Kakhki et al. [ 11] | 31 | White | Lung surgery | Lung disease | 1 | Yes | −10 to −18 | Regular | >7 | NA |
| Leo et al. [ 12] | 500 | White | Lung resection | Lung disease | 1–2 | Yes | −15 | Digital | >6 | |
| Marshall et al. [ 13] | 68 | Mixed | Lung resection | Lung disease | NA | Yes | −20 | Regular | >8 | |
| Prokakis et al. [ 14] | 91 | White | Lobectomy | Lung cancer | 2 | No | −15 to −20 | Regular | >7 |
PAL: prolonged air leak; PSP: primary spontaneous pneumothorax; VATS: video-assisted thoracic surgery.
Main characteristics of the included randomized controlled trials
| Study . | Sample size . | Ethnicity . | Participant . | Disease . | Number of tubes . | Initial suction . | Suction pressure (cmH2O) . | Drainage system . | Definition of PAL (days) . | Drainage threshold of removal (ml/day) . |
|---|---|---|---|---|---|---|---|---|---|---|
| Alphonso et al. [ 7] | 239 | White | Lung surgery | Lung disease | 1–2 | No | −20 | Regular | >6 | |
| Ayed et al. [ 8] | 100 | White | VATS | PSP | 1 | No | −20 | Regular | >5 | |
| Brunelli et al. [ 5] | 145 | White | Lobectomy | Lung cancer | 2 | Yes | −20 | Regular | >7 | |
| Brunelli et al. [ 9] | 100 | White | Lobectomy | Lung cancer | 1 | NA | −11 to −20 | Digital | >7 | NA |
| Cerfolio et al. [ 10] | 33 | Mixed | Lung surgery | Lung cancer | NA | NA | −20 | Regular | >5 | NA |
| Gocyk et al. [ 6] | 294 | White | Lung surgery | Lung disease | 1–2 | Yes | −20 | Regular | >7 | |
| Kakhki et al. [ 11] | 31 | White | Lung surgery | Lung disease | 1 | Yes | −10 to −18 | Regular | >7 | NA |
| Leo et al. [ 12] | 500 | White | Lung resection | Lung disease | 1–2 | Yes | −15 | Digital | >6 | |
| Marshall et al. [ 13] | 68 | Mixed | Lung resection | Lung disease | NA | Yes | −20 | Regular | >8 | |
| Prokakis et al. [ 14] | 91 | White | Lobectomy | Lung cancer | 2 | No | −15 to −20 | Regular | >7 |
| Study . | Sample size . | Ethnicity . | Participant . | Disease . | Number of tubes . | Initial suction . | Suction pressure (cmH2O) . | Drainage system . | Definition of PAL (days) . | Drainage threshold of removal (ml/day) . |
|---|---|---|---|---|---|---|---|---|---|---|
| Alphonso et al. [ 7] | 239 | White | Lung surgery | Lung disease | 1–2 | No | −20 | Regular | >6 | |
| Ayed et al. [ 8] | 100 | White | VATS | PSP | 1 | No | −20 | Regular | >5 | |
| Brunelli et al. [ 5] | 145 | White | Lobectomy | Lung cancer | 2 | Yes | −20 | Regular | >7 | |
| Brunelli et al. [ 9] | 100 | White | Lobectomy | Lung cancer | 1 | NA | −11 to −20 | Digital | >7 | NA |
| Cerfolio et al. [ 10] | 33 | Mixed | Lung surgery | Lung cancer | NA | NA | −20 | Regular | >5 | NA |
| Gocyk et al. [ 6] | 294 | White | Lung surgery | Lung disease | 1–2 | Yes | −20 | Regular | >7 | |
| Kakhki et al. [ 11] | 31 | White | Lung surgery | Lung disease | 1 | Yes | −10 to −18 | Regular | >7 | NA |
| Leo et al. [ 12] | 500 | White | Lung resection | Lung disease | 1–2 | Yes | −15 | Digital | >6 | |
| Marshall et al. [ 13] | 68 | Mixed | Lung resection | Lung disease | NA | Yes | −20 | Regular | >8 | |
| Prokakis et al. [ 14] | 91 | White | Lobectomy | Lung cancer | 2 | No | −15 to −20 | Regular | >7 |
PAL: prolonged air leak; PSP: primary spontaneous pneumothorax; VATS: video-assisted thoracic surgery.
The PRISMA flow diagram of literature retrieval.
Two independent researchers assessed the risk of bias of the included studies. Ayed et al. [ 8] and Brunelli et al. [ 9] did not report enough details of sequence generation and concealment of allocation, whereas Kakhki et al.[ 11], Leo et al. [ 12] and Marshall et al. [ 13] performed randomization-based clinical decision, which indicates a potential of high risk of bias. The graph of the risk of bias for the included studies is shown in Table 2 and Fig. 2.
Risk of bias assessment
| Study . | Sequence generation . | Concealment of allocation . | Blinding of participants and personnel . | Blinding of outcome assessors . | Incomplete outcome data addressed . | Free of selective reporting . | Other bias . |
|---|---|---|---|---|---|---|---|
| Alphonso et al. [ 7] | Low | Low | Low | Low | Low | Low | Low |
| Ayed et al. [ 8] | Unclear | Unclear | Low | Low | Low | Low | Low |
| Brunelli et al. [ 5] | Unclear | Unclear | Low | Low | Low | Low | Low |
| Brunelli et al. [ 9] | Low | Low | Low | Low | Low | Low | Low |
| Cerfolio et al. [ 10] | Low | Low | Low | Low | Low | Low | Low |
| Gocyk et al. [ 6] | Low | Low | Low | Low | Low | Low | Low |
| Kakhki et al. [ 11] | High | Low | Low | Low | Low | Low | Low |
| Leo et al. [ 12] | High | Low | Low | Low | Low | Low | Low |
| Marshall et al. [ 13] | High | Low | Low | Low | Low | Low | Low |
| Prokakis et al. [ 14] | Low | Low | Low | Low | Low | Low | Low |
| Study . | Sequence generation . | Concealment of allocation . | Blinding of participants and personnel . | Blinding of outcome assessors . | Incomplete outcome data addressed . | Free of selective reporting . | Other bias . |
|---|---|---|---|---|---|---|---|
| Alphonso et al. [ 7] | Low | Low | Low | Low | Low | Low | Low |
| Ayed et al. [ 8] | Unclear | Unclear | Low | Low | Low | Low | Low |
| Brunelli et al. [ 5] | Unclear | Unclear | Low | Low | Low | Low | Low |
| Brunelli et al. [ 9] | Low | Low | Low | Low | Low | Low | Low |
| Cerfolio et al. [ 10] | Low | Low | Low | Low | Low | Low | Low |
| Gocyk et al. [ 6] | Low | Low | Low | Low | Low | Low | Low |
| Kakhki et al. [ 11] | High | Low | Low | Low | Low | Low | Low |
| Leo et al. [ 12] | High | Low | Low | Low | Low | Low | Low |
| Marshall et al. [ 13] | High | Low | Low | Low | Low | Low | Low |
| Prokakis et al. [ 14] | Low | Low | Low | Low | Low | Low | Low |
Risk of bias assessment
| Study . | Sequence generation . | Concealment of allocation . | Blinding of participants and personnel . | Blinding of outcome assessors . | Incomplete outcome data addressed . | Free of selective reporting . | Other bias . |
|---|---|---|---|---|---|---|---|
| Alphonso et al. [ 7] | Low | Low | Low | Low | Low | Low | Low |
| Ayed et al. [ 8] | Unclear | Unclear | Low | Low | Low | Low | Low |
| Brunelli et al. [ 5] | Unclear | Unclear | Low | Low | Low | Low | Low |
| Brunelli et al. [ 9] | Low | Low | Low | Low | Low | Low | Low |
| Cerfolio et al. [ 10] | Low | Low | Low | Low | Low | Low | Low |
| Gocyk et al. [ 6] | Low | Low | Low | Low | Low | Low | Low |
| Kakhki et al. [ 11] | High | Low | Low | Low | Low | Low | Low |
| Leo et al. [ 12] | High | Low | Low | Low | Low | Low | Low |
| Marshall et al. [ 13] | High | Low | Low | Low | Low | Low | Low |
| Prokakis et al. [ 14] | Low | Low | Low | Low | Low | Low | Low |
| Study . | Sequence generation . | Concealment of allocation . | Blinding of participants and personnel . | Blinding of outcome assessors . | Incomplete outcome data addressed . | Free of selective reporting . | Other bias . |
|---|---|---|---|---|---|---|---|
| Alphonso et al. [ 7] | Low | Low | Low | Low | Low | Low | Low |
| Ayed et al. [ 8] | Unclear | Unclear | Low | Low | Low | Low | Low |
| Brunelli et al. [ 5] | Unclear | Unclear | Low | Low | Low | Low | Low |
| Brunelli et al. [ 9] | Low | Low | Low | Low | Low | Low | Low |
| Cerfolio et al. [ 10] | Low | Low | Low | Low | Low | Low | Low |
| Gocyk et al. [ 6] | Low | Low | Low | Low | Low | Low | Low |
| Kakhki et al. [ 11] | High | Low | Low | Low | Low | Low | Low |
| Leo et al. [ 12] | High | Low | Low | Low | Low | Low | Low |
| Marshall et al. [ 13] | High | Low | Low | Low | Low | Low | Low |
| Prokakis et al. [ 14] | Low | Low | Low | Low | Low | Low | Low |
Assessment of risk of bias. (A) Graph of the risk of bias for the included studies and (B) graph of the risk of bias summary for the included studies.
Ten studies assessed the occurrence of prolonged air leak: 795 individuals received the simple water-seal in addition to suction, whereas 806 received simple water-seal on chest drains. There was no significant difference between the 2 groups concerning the occurrence of prolonged air leak (Fig. 3A) (RR 1.23, 95% CI 0.79–1.92; P = 0.36). No significant difference was revealed in subgroup analysis.
Meta-analysis of the effect of the addition of suction to simple water-seal or simple water-seal on the occurrence of (A) prolonged air leak and (B) postoperative pneumothorax.
From 5 studies comprising 262 patients with suction and 269 with simple water-seal, we concluded that the patients in the suction group had a lower occurrence of postoperative pneumothorax compared with the simple water-seal group (RR 0.35, 95% CI 0.13–0.93; P = 0.04) (Fig. 3B). No significant difference was found in subgroup analysis.
A total of 6 studies measured the duration of chest tube drainage. Results indicated that simple water-seal may significantly shorten the duration of chest tube drainage compared with the addition of suction drainage (WMD 0.92 days, 95% CI 0.04–1.81; P = 0.04) (Fig. 4A).
Meta-analysis of the effect of the addition of suction to simple water-seal or simple water-seal on (A) the duration of chest tube drainage, (B) air leak duration and (C) length of hospital stay.
Four studies assessed the duration of air leak, with 304 patients on suction drainage and 303 on simple water-seal drainage. The effect difference between the 2 groups was not significant (WMD 0.81 days, 95% CI −0.21 to 1.82; P = 0.12) (Fig. 4B).
Five studies assessed the length of hospital stay, with no statistically significant difference between the suction drainage and simple water-seal (WMD 1.57 days, 95% CI −0.83 to 3.98; P = 0.20) (Fig. 4C). Subgroup analyses were conducted based on the drainage volume threshold for removal: 4 studies removed the chest tube when drainage volume was less than 200 ml/day, whereas 1 study removed the chest tube when drainage volume was less than 300 ml/day. Our analysis indicated that a lower drainage volume threshold for removal was significantly associated with an increased hospital stay (I 2 0%, WMD 1.02 days, 95% CI 0.41–1.62, P = 0.001).
We also analysed the incidence of other cardiopulmonary complications including pneumonia, empyema, atelectasis, arrhythmia and bleeding. We found that the addition of suction had a lower incidence of postoperative cardiopulmonary complications compared with simple water-seal (RR 0.65, 95% CI 0.48–0.89; P = 0.008). We were unable to draw any significant conclusions regarding specific cardiopulmonary complications.
For other parameters, we looked at effusion and staple line (length of the stapled parenchyma for each patient). However, we found no significant difference in effusion volume within the first 24 h or 48 h. The results from 2 studies recruiting 213 patients indicated that the suction group had bigger ‘air leak days/cm of the staple line’ compared with the simple water-seal group (WMD 0.07, 95% CI 0.01–0.13, P = 0.03), which meant that suction drainage may prolong air leak days per centimetre of staples. No significant difference was found concerning the value ‘chest tube days/cm of the staple line’. All the main results of our analysis are listed in Table 3.
Main results of our analysis
| Outcomes . | No. of studies . | No. of participants . | Results . | Heterogeneity . | |||||
|---|---|---|---|---|---|---|---|---|---|
| RR/WMD . | 95% CI . | P-value . | I 2 (%) . | PH . | Model . | ||||
| Occurrence of PAL | 10 | 1601 | RR 1.23 | 0.79 | 1.92 | 0.36 | 52 | 0.03 | Random |
| Ethnicity | |||||||||
| White | 8 | 1500 | RR 0.98 | 0.67 | 1.43 | 0.90 | 27 | 0.21 | Random |
| Mixed | 2 | 101 | RR 2.81 | 1.46 | 5.39 | 0.002 | 0 | 0.97 | Random |
| Drainage threshold of removal | |||||||||
| 200 ml/day | 5 | 869 | RR 1.26 | 0.64 | 2.50 | 0.50 | 49 | 0.10 | Random |
| The definition of PAL | |||||||||
| >7 days | 6 | 729 | RR 1.10 | 0.73 | 1.64 | 0.65 | 0 | 0.47 | Random |
| >6 days or 5 days | 4 | 872 | RR 1.42 | 0.59 | 3.43 | 0.43 | 79 | 0.002 | Random |
| Occurrence of postoperative pneumothorax | 5 | 531 | RR 0.35 | 0.13 | 0.93 | 0.04 | 24 | 0.26 | Random |
| Ethnicity | |||||||||
| White | 3 | 430 | RR 0.46 | 0.15 | 1.47 | 0.19 | 33 | 0.23 | Random |
| Drainage threshold of removal | |||||||||
| 3 | 430 | RR 0.46 | 0.15 | 1.47 | 0.19 | 33 | 0.23 | Random | |
| Duration of chest tube | 6 | 798 | WMD 0.92 | 0.04 | 1.81 | 0.04 | 78 | 0.0004 | Random |
| Ethnicity | |||||||||
| White | 5 | 730 | WMD 0.73 | 0.12 | 1.34 | 0.02 | 14 | 0.33 | Random |
| Drainage threshold of removal | |||||||||
| 4 | 630 | WMD 0.73 | 0.02 | 1.44 | 0.04 | 28 | 0.24 | Random | |
| Duration of air leak | 4 | 607 | WMD 0.81 | −0.21 | 1.81 | 0.12 | 81 | 0.001 | Random |
| Ethnicity | |||||||||
| White | 3 | 539 | WMD 0.37 | −0.26 | 1.01 | 0.25 | 0 | 0.79 | Random |
| Length of hospital stay | 5 | 504 | WMD 1.57 | −0.83 | 3.98 | 0.2 | 92 | Random | |
| Ethnicity | |||||||||
| White | 4 | 436 | WMD 0.62 | −0.27 | 1.51 | 0.17 | 27 | 0.25 | Random |
| Drainage threshold of removal | |||||||||
| 200 ml/day | 3 | 336 | WMD 1.02 | 0.41 | 1.62 | 0.001 | 0 | 0.72 | Random |
| Effusion volume in the first 24 h | 2 | 354 | WMD 43.62 | −34.47 | 121.72 | 0.27 | 88 | 0.003 | Random |
| Effusion volume in the first 48 h | 3 | 499 | WMD 10.42 | −124.77 | 145.61 | 0.88 | 80 | 0.007 | Random |
| Air leak days/cm of the staple line | 2 | 213 | WMD 0.07 | 0.01 | 0.13 | 0.03 | 85 | 0.01 | Random |
| Chest tube days/cm of the staple line | 2 | 213 | WMD 0.09 | −0.02 | 0.20 | 0.11 | 93 | Random | |
| Cardiopulmonary complications | 3 | 745 | RR 0.65 | 0.48 | 0.89 | 0.008 | 0 | 0.68 | Random |
| Pneumonia | 3 | 736 | RR 0.64 | 0.34 | 1.22 | 0.17 | 0 | 0.58 | Random |
| Empyema | 2 | 591 | RR 1.44 | 0.24 | 8.74 | 0.69 | 0 | 0.68 | Random |
| Atelectasis | 2 | 591 | RR 0.57 | 0.24 | 1.35 | 0.20 | 0 | 0.45 | Random |
| Arrhythmia | 3 | 736 | RR 0.93 | 0.47 | 1.86 | 0.84 | 43 | 0.18 | Random |
| Bleeding | 2 | 591 | RR 0.98 | 0.37 | 2.57 | 0.96 | 0 | 0.65 | Random |
| Outcomes . | No. of studies . | No. of participants . | Results . | Heterogeneity . | |||||
|---|---|---|---|---|---|---|---|---|---|
| RR/WMD . | 95% CI . | P-value . | I 2 (%) . | PH . | Model . | ||||
| Occurrence of PAL | 10 | 1601 | RR 1.23 | 0.79 | 1.92 | 0.36 | 52 | 0.03 | Random |
| Ethnicity | |||||||||
| White | 8 | 1500 | RR 0.98 | 0.67 | 1.43 | 0.90 | 27 | 0.21 | Random |
| Mixed | 2 | 101 | RR 2.81 | 1.46 | 5.39 | 0.002 | 0 | 0.97 | Random |
| Drainage threshold of removal | |||||||||
| 200 ml/day | 5 | 869 | RR 1.26 | 0.64 | 2.50 | 0.50 | 49 | 0.10 | Random |
| The definition of PAL | |||||||||
| >7 days | 6 | 729 | RR 1.10 | 0.73 | 1.64 | 0.65 | 0 | 0.47 | Random |
| >6 days or 5 days | 4 | 872 | RR 1.42 | 0.59 | 3.43 | 0.43 | 79 | 0.002 | Random |
| Occurrence of postoperative pneumothorax | 5 | 531 | RR 0.35 | 0.13 | 0.93 | 0.04 | 24 | 0.26 | Random |
| Ethnicity | |||||||||
| White | 3 | 430 | RR 0.46 | 0.15 | 1.47 | 0.19 | 33 | 0.23 | Random |
| Drainage threshold of removal | |||||||||
| 3 | 430 | RR 0.46 | 0.15 | 1.47 | 0.19 | 33 | 0.23 | Random | |
| Duration of chest tube | 6 | 798 | WMD 0.92 | 0.04 | 1.81 | 0.04 | 78 | 0.0004 | Random |
| Ethnicity | |||||||||
| White | 5 | 730 | WMD 0.73 | 0.12 | 1.34 | 0.02 | 14 | 0.33 | Random |
| Drainage threshold of removal | |||||||||
| 4 | 630 | WMD 0.73 | 0.02 | 1.44 | 0.04 | 28 | 0.24 | Random | |
| Duration of air leak | 4 | 607 | WMD 0.81 | −0.21 | 1.81 | 0.12 | 81 | 0.001 | Random |
| Ethnicity | |||||||||
| White | 3 | 539 | WMD 0.37 | −0.26 | 1.01 | 0.25 | 0 | 0.79 | Random |
| Length of hospital stay | 5 | 504 | WMD 1.57 | −0.83 | 3.98 | 0.2 | 92 | Random | |
| Ethnicity | |||||||||
| White | 4 | 436 | WMD 0.62 | −0.27 | 1.51 | 0.17 | 27 | 0.25 | Random |
| Drainage threshold of removal | |||||||||
| 200 ml/day | 3 | 336 | WMD 1.02 | 0.41 | 1.62 | 0.001 | 0 | 0.72 | Random |
| Effusion volume in the first 24 h | 2 | 354 | WMD 43.62 | −34.47 | 121.72 | 0.27 | 88 | 0.003 | Random |
| Effusion volume in the first 48 h | 3 | 499 | WMD 10.42 | −124.77 | 145.61 | 0.88 | 80 | 0.007 | Random |
| Air leak days/cm of the staple line | 2 | 213 | WMD 0.07 | 0.01 | 0.13 | 0.03 | 85 | 0.01 | Random |
| Chest tube days/cm of the staple line | 2 | 213 | WMD 0.09 | −0.02 | 0.20 | 0.11 | 93 | Random | |
| Cardiopulmonary complications | 3 | 745 | RR 0.65 | 0.48 | 0.89 | 0.008 | 0 | 0.68 | Random |
| Pneumonia | 3 | 736 | RR 0.64 | 0.34 | 1.22 | 0.17 | 0 | 0.58 | Random |
| Empyema | 2 | 591 | RR 1.44 | 0.24 | 8.74 | 0.69 | 0 | 0.68 | Random |
| Atelectasis | 2 | 591 | RR 0.57 | 0.24 | 1.35 | 0.20 | 0 | 0.45 | Random |
| Arrhythmia | 3 | 736 | RR 0.93 | 0.47 | 1.86 | 0.84 | 43 | 0.18 | Random |
| Bleeding | 2 | 591 | RR 0.98 | 0.37 | 2.57 | 0.96 | 0 | 0.65 | Random |
CI: confidence interval; PAL: prolonged air leak; PH: P-value of heterogeneity; RR: risk ratio; WMD: weighted mean difference.
Main results of our analysis
| Outcomes . | No. of studies . | No. of participants . | Results . | Heterogeneity . | |||||
|---|---|---|---|---|---|---|---|---|---|
| RR/WMD . | 95% CI . | P-value . | I 2 (%) . | PH . | Model . | ||||
| Occurrence of PAL | 10 | 1601 | RR 1.23 | 0.79 | 1.92 | 0.36 | 52 | 0.03 | Random |
| Ethnicity | |||||||||
| White | 8 | 1500 | RR 0.98 | 0.67 | 1.43 | 0.90 | 27 | 0.21 | Random |
| Mixed | 2 | 101 | RR 2.81 | 1.46 | 5.39 | 0.002 | 0 | 0.97 | Random |
| Drainage threshold of removal | |||||||||
| 200 ml/day | 5 | 869 | RR 1.26 | 0.64 | 2.50 | 0.50 | 49 | 0.10 | Random |
| The definition of PAL | |||||||||
| >7 days | 6 | 729 | RR 1.10 | 0.73 | 1.64 | 0.65 | 0 | 0.47 | Random |
| >6 days or 5 days | 4 | 872 | RR 1.42 | 0.59 | 3.43 | 0.43 | 79 | 0.002 | Random |
| Occurrence of postoperative pneumothorax | 5 | 531 | RR 0.35 | 0.13 | 0.93 | 0.04 | 24 | 0.26 | Random |
| Ethnicity | |||||||||
| White | 3 | 430 | RR 0.46 | 0.15 | 1.47 | 0.19 | 33 | 0.23 | Random |
| Drainage threshold of removal | |||||||||
| 3 | 430 | RR 0.46 | 0.15 | 1.47 | 0.19 | 33 | 0.23 | Random | |
| Duration of chest tube | 6 | 798 | WMD 0.92 | 0.04 | 1.81 | 0.04 | 78 | 0.0004 | Random |
| Ethnicity | |||||||||
| White | 5 | 730 | WMD 0.73 | 0.12 | 1.34 | 0.02 | 14 | 0.33 | Random |
| Drainage threshold of removal | |||||||||
| 4 | 630 | WMD 0.73 | 0.02 | 1.44 | 0.04 | 28 | 0.24 | Random | |
| Duration of air leak | 4 | 607 | WMD 0.81 | −0.21 | 1.81 | 0.12 | 81 | 0.001 | Random |
| Ethnicity | |||||||||
| White | 3 | 539 | WMD 0.37 | −0.26 | 1.01 | 0.25 | 0 | 0.79 | Random |
| Length of hospital stay | 5 | 504 | WMD 1.57 | −0.83 | 3.98 | 0.2 | 92 | Random | |
| Ethnicity | |||||||||
| White | 4 | 436 | WMD 0.62 | −0.27 | 1.51 | 0.17 | 27 | 0.25 | Random |
| Drainage threshold of removal | |||||||||
| 200 ml/day | 3 | 336 | WMD 1.02 | 0.41 | 1.62 | 0.001 | 0 | 0.72 | Random |
| Effusion volume in the first 24 h | 2 | 354 | WMD 43.62 | −34.47 | 121.72 | 0.27 | 88 | 0.003 | Random |
| Effusion volume in the first 48 h | 3 | 499 | WMD 10.42 | −124.77 | 145.61 | 0.88 | 80 | 0.007 | Random |
| Air leak days/cm of the staple line | 2 | 213 | WMD 0.07 | 0.01 | 0.13 | 0.03 | 85 | 0.01 | Random |
| Chest tube days/cm of the staple line | 2 | 213 | WMD 0.09 | −0.02 | 0.20 | 0.11 | 93 | Random | |
| Cardiopulmonary complications | 3 | 745 | RR 0.65 | 0.48 | 0.89 | 0.008 | 0 | 0.68 | Random |
| Pneumonia | 3 | 736 | RR 0.64 | 0.34 | 1.22 | 0.17 | 0 | 0.58 | Random |
| Empyema | 2 | 591 | RR 1.44 | 0.24 | 8.74 | 0.69 | 0 | 0.68 | Random |
| Atelectasis | 2 | 591 | RR 0.57 | 0.24 | 1.35 | 0.20 | 0 | 0.45 | Random |
| Arrhythmia | 3 | 736 | RR 0.93 | 0.47 | 1.86 | 0.84 | 43 | 0.18 | Random |
| Bleeding | 2 | 591 | RR 0.98 | 0.37 | 2.57 | 0.96 | 0 | 0.65 | Random |
| Outcomes . | No. of studies . | No. of participants . | Results . | Heterogeneity . | |||||
|---|---|---|---|---|---|---|---|---|---|
| RR/WMD . | 95% CI . | P-value . | I 2 (%) . | PH . | Model . | ||||
| Occurrence of PAL | 10 | 1601 | RR 1.23 | 0.79 | 1.92 | 0.36 | 52 | 0.03 | Random |
| Ethnicity | |||||||||
| White | 8 | 1500 | RR 0.98 | 0.67 | 1.43 | 0.90 | 27 | 0.21 | Random |
| Mixed | 2 | 101 | RR 2.81 | 1.46 | 5.39 | 0.002 | 0 | 0.97 | Random |
| Drainage threshold of removal | |||||||||
| 200 ml/day | 5 | 869 | RR 1.26 | 0.64 | 2.50 | 0.50 | 49 | 0.10 | Random |
| The definition of PAL | |||||||||
| >7 days | 6 | 729 | RR 1.10 | 0.73 | 1.64 | 0.65 | 0 | 0.47 | Random |
| >6 days or 5 days | 4 | 872 | RR 1.42 | 0.59 | 3.43 | 0.43 | 79 | 0.002 | Random |
| Occurrence of postoperative pneumothorax | 5 | 531 | RR 0.35 | 0.13 | 0.93 | 0.04 | 24 | 0.26 | Random |
| Ethnicity | |||||||||
| White | 3 | 430 | RR 0.46 | 0.15 | 1.47 | 0.19 | 33 | 0.23 | Random |
| Drainage threshold of removal | |||||||||
| 3 | 430 | RR 0.46 | 0.15 | 1.47 | 0.19 | 33 | 0.23 | Random | |
| Duration of chest tube | 6 | 798 | WMD 0.92 | 0.04 | 1.81 | 0.04 | 78 | 0.0004 | Random |
| Ethnicity | |||||||||
| White | 5 | 730 | WMD 0.73 | 0.12 | 1.34 | 0.02 | 14 | 0.33 | Random |
| Drainage threshold of removal | |||||||||
| 4 | 630 | WMD 0.73 | 0.02 | 1.44 | 0.04 | 28 | 0.24 | Random | |
| Duration of air leak | 4 | 607 | WMD 0.81 | −0.21 | 1.81 | 0.12 | 81 | 0.001 | Random |
| Ethnicity | |||||||||
| White | 3 | 539 | WMD 0.37 | −0.26 | 1.01 | 0.25 | 0 | 0.79 | Random |
| Length of hospital stay | 5 | 504 | WMD 1.57 | −0.83 | 3.98 | 0.2 | 92 | Random | |
| Ethnicity | |||||||||
| White | 4 | 436 | WMD 0.62 | −0.27 | 1.51 | 0.17 | 27 | 0.25 | Random |
| Drainage threshold of removal | |||||||||
| 200 ml/day | 3 | 336 | WMD 1.02 | 0.41 | 1.62 | 0.001 | 0 | 0.72 | Random |
| Effusion volume in the first 24 h | 2 | 354 | WMD 43.62 | −34.47 | 121.72 | 0.27 | 88 | 0.003 | Random |
| Effusion volume in the first 48 h | 3 | 499 | WMD 10.42 | −124.77 | 145.61 | 0.88 | 80 | 0.007 | Random |
| Air leak days/cm of the staple line | 2 | 213 | WMD 0.07 | 0.01 | 0.13 | 0.03 | 85 | 0.01 | Random |
| Chest tube days/cm of the staple line | 2 | 213 | WMD 0.09 | −0.02 | 0.20 | 0.11 | 93 | Random | |
| Cardiopulmonary complications | 3 | 745 | RR 0.65 | 0.48 | 0.89 | 0.008 | 0 | 0.68 | Random |
| Pneumonia | 3 | 736 | RR 0.64 | 0.34 | 1.22 | 0.17 | 0 | 0.58 | Random |
| Empyema | 2 | 591 | RR 1.44 | 0.24 | 8.74 | 0.69 | 0 | 0.68 | Random |
| Atelectasis | 2 | 591 | RR 0.57 | 0.24 | 1.35 | 0.20 | 0 | 0.45 | Random |
| Arrhythmia | 3 | 736 | RR 0.93 | 0.47 | 1.86 | 0.84 | 43 | 0.18 | Random |
| Bleeding | 2 | 591 | RR 0.98 | 0.37 | 2.57 | 0.96 | 0 | 0.65 | Random |
CI: confidence interval; PAL: prolonged air leak; PH: P-value of heterogeneity; RR: risk ratio; WMD: weighted mean difference.
From derived forest plots, we found that none of the displayed outcomes were outside of the estimated range. Also, no significant discoveries were identified in sensitivity analyses. Furthermore, we found no significant publication bias by visual inspection of the funnel plot and Begg’s test (P = 1.00).
Compared with simple water-seal, the addition of external suction increased the duration of chest tube drainage, decreased the occurrence of postoperative pneumothorax and other cardiopulmonary complications and increased ‘air leak days/cm of the staple line’. However, between simple water-seal and external suction, no significant differences were found regarding air leak duration, length of hospital stay and the occurrence of prolonged air leak. The differences between the 2 groups, including the criteria for chest tubes removal (especially the drainage volume threshold for chest tube removal), the definition of prolonged air leak, the onset time of suction drainage, the disease type (lung cancer, pneumothorax and other lung disease) and whether discharged home on device, may affect the results. However, the lack of sufficient data prevented us from performing a further analysis of these differences.
The duration of chest tube drainage was an important issue that might affect postoperative success [ 15]. We found that the addition of suction increased the duration of chest tube drainage compared with simple water-seal, and this was in accordance with the study by Ayed et al. [ 8] and Marshall et al. [ 13]. However, Brunelli et al. [ 9] found no significant differences between the effects of the 2 groups. The drainage device was digital, which was not the same with other research studies. Miller et al. [ 16] and our previous study [ 17] showed that the use of a digital drainage system may change the duration of chest tube drainage.
The occurrence of postoperative pneumothorax was associated with the surgical lesions and the quality of the operation [ 18]. We found that suction drainage was beneficial in reducing the incidence of postoperative pneumothorax compared with simple water-seal. Meanwhile, some previous meta-analyses arrived at the same conclusion [ 19, 20]. However, Ayed et al. [ 8] drew a different conclusion. They recruited 100 consecutive participants who underwent video-assisted thoracic surgery for PSP, equally assigned into external suction and simple water-seal in a 1:1 ratio and found no significant difference between the 2 groups. Although Ayed et al. [ 8] only included PSP patients, the previous presence of air leak may have influence on the incidence of postoperative pneumothorax [ 21]. Furthermore, they removed the chest tubes according to the removal criteria ‘lung was fully recovered with no air leak and less than 100-ml pleural fluid drainage for 24 h’. This lower drainage volume (compared to other studies) was rational as the PSP patients have less pleural fluid than lung patients in other studies.
There was no widely accepted definition of prolonged air leak in the included studies. Most researchers considered ‘prolonged air leak’ to be a persistent air leak longer than 7 days, whereas other authors regarded ‘prolonged air leak’ as a persistent air leak longer than 8, 6 or 5 days. Initially, we thought that the difference in definitions among the included studies may impact the incidence of prolonged air leak. However, no significant difference was identified in subgroup analyses. Based on the recent literature, several authors have recommended defining a prolonged air leak as a postoperative air leak lasting >5 days, and this definition is consistent with the Society of Thoracic Surgeons (STS) database definition for a prolonged air leak as an air leak exceeding the otherwise necessary length of stay [ 22, 23].
We found patients with chest tubes placed to the addition of suction had a lower incidence of postoperative pneumothorax compared with simple water-seal. Herein, we propose 2 possible reasons for how suction drainage could have decreased the occurrence of postoperative pneumothorax. First, applying chest tubes to suction might accelerate the elimination of excessive air and drainage in the pleural cavity directly. Second, chest tubes connected to suction could be more stable to ensure the drainage function and avoid complications.
Staples are widely used to close stumps during operations such as sleeve gastrostomy and are considered to be a main cause of staple-line bleeding, staple-line leaks and dehiscence [ 24]. Some researchers pointed out that buttressing the staple lines could decrease the air leak duration after pulmonary surgery [ 25, 26]. The length of the staple line reflects the extent of the resection, which, of course, impacts on the incidence of postoperative air leakage. To help control for this, we assessed the ratio of air leak duration and the length of the staple line between the 2 groups. Our results indicated that suction drainage is associated with higher air leak days/cm of the staple line. That meant that in the condition where the length of the staple line is same between the 2 groups, the suction group would have longer air leak days.
In China, thoracic surgeons do not apply suction drainage systems routinely. There are several possible reasons for this. First, the lack of guidelines for when and how to use suction drainage. Second, it may be inconvenient to use. Third, the clinical effect of the addition of suction drainage is not definite. The higher cost of suction drainage (compared to simple water-seal) is also a possible reason. Our meta-analysis may help promote evidence-based medicine in this field in China.
Compared with previous published meta-analyses, the strengths of this analysis included (i) updating published articles and recruiting more studies; (ii) further discussion on more postoperative outcome parameters such as the occurrence of cardiopulmonary complications and (iii) clear inclusion and exclusion criteria, careful screening of studies, independent collection of data, complete assessment of studies quality and reliable tests to identify heterogeneity. However, we also had some limitations. (i) Heterogeneity among included studies. We assessed the risk of bias of each eligible studies and found 3 studies that had a high risk of bias due to randomization based on clinical experience. The heterogeneity test for each analysis was well accepted. In addition, we conducted a subgroup analysis and a sensitivity analysis to explain heterogeneity based on some potential source of heterogeneity; (ii) lack of standard procedure for chest tube management. For example, there was still no universally accepted definition of prolonged air leak; (iii) insufficient sample size for some data items. For example, when we analysed the occurrence of arrhythmia and bleeding, only 2 studies were homogeneous and used in the final analysis. The low number of studies for this data item might unfairly affect our results. Therefore, more large-sample randomized controlled trials are needed.
The addition of suction to simple water-seal made no difference to air leak duration, hospital stay or the occurrence of prolonged air leak following pulmonary surgery. In patients where there is concern about a residual or increasing pneumothorax, the addition of suction may be applied selectively.
The authors thank Hong Xie, from the international office of the West China School of Medicine, for her help on the English language editing of this article.
This work was supported by the National Natural Science Foundation of China [81172236 and 81372505] and the Key Science and Technology Program of Sichuan Province, China [2013SZ0005, 2014SZ0148 and 2016FZ0118 to L.L.].
Conflict of interest: none declared.
