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Utility of Objective Chest Tube Management After Pulmonary Resection Using a Digital Drainage System
Utility of Objective Chest Tube Management After Pulmonary Resection Using a Digital Drainage System Kazuya Takamochi, MD, Kota Imashimizu, MD, Mariko Fukui, MD, Tatsuo Maeyashiki, MD, Mikiko Suzuki, MD, Takuya Ueda, MD, Hironori Matsuzawa, MD, Shunki Hirayama, MD, Takeshi Matsunaga, MD, Shiaki Oh, MD, and Kenji Suzuki, MD Department of General Thoracic Surgery, Juntendo University School of Medicine, Tokyo, Japan
Background. We sought to evaluate the clinical utility of chest tube management after pulmonary resection based on objective digital monitoring of pleural pressure and digital surveillance for air leaks. Methods. We prospectively recorded the perioperative data of 308 patients who underwent pulmonary resection between December 2013 and January 2016. We used information from a digital monitoring thoracic drainage system to measure peak air leakage during the first 24 hours after the operation, patterns of air leakage over the first 72 hours, and patterns of pleural pressure changes until the chest tubes were removed. Results. There were 240 patients with lung cancer and 68 patients with other diseases. The operations included 49 wedge resections, 58 segmentectomies, and 201 lobectomies. A postoperative air leak was observed in 61 patients (20%). A prolonged air leak exceeding 20 mL/ min lasting 5 days or more was observed in 18 patients
(5.8%). Multivariate analysis of various perioperative factors showed forced expiratory volume in 1 second below 70%, patterns of air leakage, defined as exacerbating and remitting or without a trend toward improvement, and peak air leakage of 100 mL/min or more were significant positive predictors of prolonged air leak. Fluctuations in pleural pressure occurred just after the air leakage rate decreased to less than 20 mL/min. Conclusions. Digital monitoring of peak air leakage and patterns of air leakage were useful for predicting prolonged air leak after pulmonary resection. Information on the disappearance of air leak could be derived from the change in the rate of air leakage and from the increase in fluctuation of pleural pressure.
P
In response, the Thopaz digitally monitored thoracic drainage system (Medela Healthcare, Baar, Switzerland) has been designed to provide objective measurements of air leakage and pleural pressure [5]. With this system, air leakage and pleural pressure can be accurately measured in mL/min and mm H2O, respectively. The rate of air leakage can be seen on a display in real time. Furthermore, the serial digital data for air leakage and pleural pressure during the presence of the chest tube can be retrospectively analyzed by exporting them to a personal computer with ThopEasy software (Medela Healthcare). Digital surveillance for air leakage is reported to reduce interobserver disagreement in decision making in the management of patients with chest tubes [6, 7], and the system obviates the empiric need to clamp the chest tube before removal to rule out the existence of occult small air leaks, which can lead to delayed pneumothorax formation.
rolonged air leak (PAL) is one of the major factors that delay early hospital discharge after pulmonary resection. The incidence of PAL after pulmonary lobectomy is reported to be 10% to 15% [1]. PAL sometimes results in serious complications such as empyema; therefore, early prediction and intervention for PAL is crucial. Risk factors for PAL include gender, smoking history, body mass index, preoperative steroid use, emphysema, decreased pulmonary function, pleural adhesions, type of lung resection, and location of the resection [2–4]. However, no commonly accepted criteria for the prediction of PAL in clinical practice have yet appeared. Because the traditional thoracic drainage system measures and grades air leaks in a subjective manner, interobserver disagreement on the presence of an air leak is frequent [5, 6], even among experienced surgeons.
Accepted for publication Jan 12, 2017. Address correspondence to Dr Takamochi, Department of General Thoracic Surgery, Juntendo University School of Medicine, 1-3, Hongo 3-chome, Bunkyo-ku, Tokyo 1130-8431, Japan; email: ktakamo@ juntendo.ac.jp.
Ó 2017 by The Society of Thoracic Surgeons Published by Elsevier Inc.
(Ann Thorac Surg 2017;-:-–-) Ó 2017 by The Society of Thoracic Surgeons
The Supplemental Table can be viewed in the online version of this article [http://dx.doi.org/10.1016/ j.athoracsur.2017.01.061] on http://www.annalsthoracic surgery.org.
0003-4975/$36.00 http://dx.doi.org/10.1016/j.athoracsur.2017.01.061
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Table 1. Patient Characteristics Variable Gender, No. Male Female Age, mean SD, y Smoking, No. Smoker Nonsmoker Smoking index, median (range) Primary disease, No. Lung cancer Metastatic lung tumor Pneumothorax Others Comorbidities, No. (%) Emphysema Interstitial pneumonia Diabetes mellitus Cardiac disease Medication use, No. (%) Steroid Anticoagulant or antiplatelet
Patients (N ¼ 308) 195 113 68 33 201 107 455 (0–4,410) 240 32 2 34 81 31 47 36
(26) (10) (15) (12)
5 (2) 40 (13)
Compared with the clinical utility of digital surveillance for air leakage, however, there is little evidence to support the digital monitoring of pleural pressure using a digital thoracic drainage system. Our goal in this study was to establish reliable criteria for the prediction of PAL based on the findings of digital monitoring of air leakage and to elucidate the clinical utility of the digital monitoring of pleural pressure.
Material and Methods This study was a retrospective analysis based on an electronic database and was performed under a waiver of authorization approved by the Juntendo University School of Medicine Institutional Review Board.
Patient Data We prospectively collected the postoperative data of 308 patients who were digitally monitored with the Thopaz system after undergoing pulmonary resection between December 2013 and January 2016. The Thopaz system was used for patients after pulmonary resection unselectively. We could not use it for all patients because only 5 Thopaz systems were available at our institute; thus, 578 patients Table 3. Postoperative Findings
Findings
Table 2. Intraoperative Findings Variable Grade of adhesions None Mild Moderate Severe Surgical procedure Wedge resection Segmentectomy Lobectomy Chest tubes, No. 1 2 3 Size of chest tubes 24F 28F Grade of air leak 0 1 2 3 Sealant use Yes No
No. (%) (N ¼ 308) 187 73 37 11
(61) (24) (12) (4)
49 (16) 58 (19) 201 (65) 303 (98) 4 (1.7) 1 (0.3) 302 (98) 6 (2) 153 81 60 14
(50) (26) (19) (5)
242 (79) 66 (21)
Postoperative air leak Present Absent Duration of air leak, days Duration of chest tube placement, days All patients Patients with postoperative air leaks Patients without postoperative air leaks Prolonged air leak (5 days) Duration of prolonged air leak, d Air leak at the time of chest tube removal 0 mL/min 0–10 mL/min 0–20 mL/min Fluid volume drained over the 24 hours before chest tube removal 200 mL 201–300 mL 301–400 mL Pleurodesis Abnormal findings on chest roentgenogram Subcutaneous emphysema Atelectasis Collapse Postoperative hospital length of stay, d All patients Patients with postoperative air leaks Patients without postoperative air leaks
No. (%) or Mean SD (N ¼ 308) 61 (20) 247 (80) 3.6 2.8 3.1 1.8 5.2 2.5 2.6 1.2 18 (5.8) 7.0 2.4 296 8 4
218 (71) 84 6 12 (3.9) 31 (10) 8 (3) 0 6.2 4.2 7.8 2.8 5.8 4.4
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were managed by the conventional drainage system during the same period of this study. Each surgical procedure was performed under the supervision of one of the attending thoracic surgeons with some residents. Segmentectomy and lobectomy was
TAKAMOCHI ET AL UTILITY OF A DIGITAL DRAINAGE SYSTEM
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performed by posterolateral, anterolateral, or axial open thoracotomy in all patients. Wedge resection was performed under minithoracotomy (<5 cm incision) or video-assisted thoracic surgery. Robotic surgery is not performed at our institution.
Fig 1. Patterns of air leakage. The blue line indicates the rate of air leakage. (A) Type A, no air leak (air leak <20 mL/min) was observed until the removal of the chest tube. (B) Type B, air leak gradually decreased. (C) Type C, although no air leak was observed immediately after the operation, delayed air leak occurred postoperatively. (D) Type D, repeated exacerbation and remission of air leak was observed. (E) Type E, air leak was observed without a trend toward improvement.
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thickness and firmness of lung parenchyma. A buttressed stapler (Endo GIA Tri-Staple Reinforce; Covidien Inc, Tokyo, Japan) was used for dividing severely emphysematous lung parenchyma. The operative technique was standardized for all surgeons.
We used conventional automatic surgical staplers for wedge resection of lung parenchyma, developing the intersegmental plane at segmentectomy, dividing incomplete fissures at lobectomy, and closing the bronchus. The size of cartridges was selected according to the
100
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90
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80
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5cmH2O
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0 0
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Postoperative period
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Pressure (cmH2O)
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Air flow (mL/min)
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Postoperative period
C
Presence of air leak
Absence of air leak
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200
Pressure (cmH2O)
160 140
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100 80
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Air flow (mL/min)
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60 40
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48
52
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(hr)
Postoperative period
Fig 2. Patterns of pleural pressure. The blue line indicates the rate of air leakage, and the red line indicates pleural pressure. The green arrow indicates the time of air leak resolution. (A) Type I, fluctuations of pleural pressure 5 cm H2O were continuously observed. (B) Type II, fluctuations of pleural pressure <5 cm H2O were continuously observed. (C) Type III, increased fluctuations in pleural pressure appeared just after the air leak level decreased to <20 mL/min.
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TAKAMOCHI ET AL UTILITY OF A DIGITAL DRAINAGE SYSTEM
An intraoperative air leak test (applied pressure 20 cm H2O) was performed using a sterile saline solution. The amount of intraoperative air leak was evaluated according to the following scoring system: grade 0 ¼ no detectable air bubbles; 1 ¼ countable air bubbles; 2 ¼ stream of bubbles; 3 ¼ coalesced bubbles (air bubbles join to form one continuous stream of air) [8]. Additional suture repair was applied when an air leak was detected. Sealant materials, such as fibrin glues, synthetic sealants, and collagen patches coated with fibrinogen and thrombin, were used if an air leak persisted. Further air leak testing was not performed after the sealant materials were used. The incidence of intraoperative air leak at the first air leak test just after pulmonary resection and that of postoperative air leak at entering an intensive care unit or a recovery room was recorded. The digitally monitored thoracic drainage system was set at a regulated pressure level of –10 cm H2O immediately after the operation until chest tube removal. The chest tubes were removed when the air leakage rate was less than 20 mL/min for more than 12 hours and the amount of pleural effusion drainage was 300 mL/day or less. Among patients with air leaks continuing for 5 or more days, pleurodesis by intrathoracic administration of the sclerosing agent OK432, with or without 50 mL of autologous blood through the chest tube, was performed according to the clinical judgment of the attending doctor for each patient [9].
Data Collection Table 1 reports patient characteristics, Table 2 reports intraoperative findings, and Table 3 reports postoperative findings. The digital data for air leakage and pleural pressure during the presence of the chest tube were exported to a personal computer with the ThopEasy software and analyzed. Peak air leakage levels over the first 24 hours after operation were examined. Figure 1 illustrates the different patterns of air leakage during the first 72 hours after the operation, defined as type A, no air leakage; type B, gradually decreasing air leakage; type C, a postoperative de novo air leak; type D, an exacerbating and remitting air leak; and type E, an air leak without a
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trend toward improvement. Figure 2 demonstrates patterns of pleural pressure until chest tube removal, defined as type I stable fluctuations in pleural pressure of 5 cm H2O or more; type II, stable fluctuations in pleural pressure of less than 5 cm H2O; and type III, an abrupt fluctuation in pleural pressure just after the air leakage rate decreased to less than 20 mL/min.
Statistical Analysis Numeric variables between the groups were compared by the unpaired t test. Categoric variables between the groups were compared by the c2 test or the Fisher exact test. In patients with postoperative air leak, univariate and multivariate analyses were performed using a forward stepwise logistic regression model to determine the relationship between the incidence of PAL and the following clinical factors: gender; age; smoking status; presence of comorbidities such as emphysema, interstitial pneumonia, diabetes mellitus, steroid use, and anticoagulant or antiplatelet treatment; presence of adhesions; forced expiratory volume in 1 second (FEV1); vital capacity; diffusion capacity of the lung for carbon monoxide; type of surgical procedure (wedge resection vs segmentectomy or lobectomy); grade of air leak; sealant use; pattern of air leakage in the first 72 postoperative hours; and peak air leakage rate in the first 24 postoperative hours. To eliminate confounding variables, we calculated the Pearson productmoment correlation coefficient (r). Among the significant predictive factors of PAL in univariate analyses, factors proving the absence of strong correlation (jrj < 0.7) were entered into multivariate analysis. A p value of less than 0.05 was considered to be statistically significant. Statistical analyses were performed using SPSS 20.0 software (IBM Corp, Armonk, NY).
Results The cohort comprised 195 men and 113 women, 201 smokers and 107 never smokers, and 240 patients with lung cancer and 68 with other diseases. The operations included 49 wedge resections, 58 segmentectomies, and
Table 4. Duration of Air Leaks and the Incidence of Prolonged Air Leak According to Pattern of Air Leak and Peak Air Leak
Variable Patterns of air leakage Type B Type C Type D Type E At peak air leakage <100 mL/min 100 mL/min 200 mL/min 300 mL/min 400 mL/min PAL ¼ prolonged air leak 5 days.
No.
Duration of Air Leak
Duration of Chest Tube Placement
Incidence of PAL
Mean SD, d
Mean SD, d
No. (%)
23 15 11 12
2.5 1.7 3.3 6.6
2.2 2.2 2.4 3.5
4.3 4.4 5.5 7.8
1.7 2.3 1.9 2.8
4 1 4 9
(17) (7) (36) (75)
34 27 16 11 9
2.3 4.5 5.4 6.3 6.7
2.2 3.5 3.6 3.8 4.1
4.6 5.9 6.6 7.2 7.6
2.0 2.9 3.1 3.3 3.5
5 13 10 8 7
(15) (48) (63) (73) (78)
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Table 5. Univariate and Multivariate Analyses of Predictors of Prolonged Air Leak in Patients With Postoperative Air Leak (n ¼ 61)
Variable Gender Female Male Age <70 y 70 y Smoking (pack-year) 5 >5 Emphysema No Yes Interstitial pneumonia No Yes Diabetes mellitus No Yes Steroid use No Yes Anticoagulant or antiplatelet use No Yes Adhesions No Yes FEV1 (%) 70% <70% Vital capacity (%) 80% <80% DLCO (%) 40% <40% Surgical procedures Wedge resection Seg or Lob Grade of air leak 0 or 1 2 or 3 Sealant use No Yes Patterns of air leak Type B or C Type D or E
Patients
PAL
Univariate Analysis
No.
No.
Odds Ratio (95% CI)
20 41
2 16
1.00 (reference) 5.76 (1.40–39.4)
23 38
6 12
1.00 (reference) 1.31 (0.42–4.37)
18 43
6 12
1.00 (reference) 0.67 (0.24–2.64)
43 18
11 7
1.00 (reference) 1.85 (0.56–5.98)
55 6
18 0
a
1.00 (reference) 0.67 (0.56–0.81)a
47 14
16 2
1.00 (reference) 0.32 (0.05–1.38)
57 4
17 1
1.00 (reference) 0.78 (0.04–6.63)
52 9
16 2
1.00 (reference) 0.60 (0.09–3.02)
30 31
5 13
1.00 (reference) 3.61 (1.14–13.0)
36 25
6 12
1.00 (reference) 4.62 (1.47–15.9)
58 3
18 0
a
1.00 (reference) 0.69 (0.58–0.82)a
47 9
13 3
1.00 (reference) 1.31 (0.25–5.77)
2 59
0 18
1.00 (reference)a 1.44 (1.22–1.70)a
36 25
6 12
1.00 (reference) 4.62 (1.47–15.9)
7 54
0 18
a
1.00 (reference) 1.50 (1.24–1.81)a
38 23
5 13
1.00 (reference) 8.58 (2.59–32.6)
Multivariate Analysis p
Odds Ratio (95% CI)
0.013
p 0.367
0.647
0.674
0.305
0.110a
0.134
0.836
0.595
0.028
0.251
0.008
0.009 1.00 (reference) 10.2 (1.80–58.1)
0.343a
0.733
0.493a
0.008
0.351
0.074a
<0.001
0.002 1.00 (reference) 16.4 (2.87–93.2) (Continued)
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Table 5. Continued
Variable Peak air leak <100 mL/min 100 mL/min
Patients
PAL
Univariate Analysis
No.
No.
Odds Ratio (95% CI)
34 27
5 13
1.00 (reference) 5.39 (1.68–19.7)
Multivariate Analysis p
Odds Ratio (95% CI)
p
0.004
0.035 1.00 (reference) 4.97 (1.12–22.0)
a
The odds ratio and p value could not be analyzed by the logistic regression model because 0 was one of the numbers in the columns. Therefore, odds ratio and p value analyzed by the c2 test are shown. However, these factors were not entered to the multivariate logistic regression model.
CI ¼ confidence interval; DLCO ¼ diffusion capacity of the lung for carbon monoxide; lobectomy; PAL ¼ prolonged air leak 5 days; Seg ¼ segmentectomy.
201 lobectomies. A buttressed stapler was used in 9 patients in this study: 6 for dividing incomplete fissures at lobectomy, 2 for developing the intersegmental plane at segmentectomy, and 1 for wedge resection of lung parenchyma. No patient required ventilator management postoperatively. No patient needed additional chest tube placement because of drainage failure by the Thopaz system resulting in postoperative pneumothorax and progressive severe subcutaneous emphysema during chest tube placement. After chest tube removal, no pneumothorax or progressive severe subcutaneous emphysema was observed. Slight subcutaneous emphysema was depicted on the chest roentgenogram just after the operation in 32 of 308 patients (10%) but spontaneously resolved in all patients during hospitalization. Air leakage patterns in patients with subcutaneous emphysema were type A in 18 (7%), type B in 5 (2%), type C in 1 (7%), type D in 2 (18%), and type E in 5 (42%). The regulated pressure level of –10 cm H2O on the digitally monitored thoracic drainage system was not changed until chest tube removal for all patients regardless of the status of postoperative air leak. Intraoperative air leak, postoperative air leak, and PAL were observed in 155 (50%), 61 (20%), and 18 of 308 patients (5.8%), respectively. The mean postoperative hospital length of stay was longer in patients with postoperative air leaks. Pleurodesis was performed for 12 patients (3.9%). Air leakage patterns in patients who ultimately received pleurodesis were type B in 2, type C in 1, type D in 2, and type E in 7. Table 4 reveals the frequency of PAL according to air leakage pattern. The
FEV1 ¼ forced expiratory volume in 1 second;
Lob ¼
risk of PAL was higher in patients showing type D or E air leakage patterns than in those showing type B or C (p < 0.001). The risk of PAL was higher in patients with a peak air leak of 100 mL/min or more compared with those with less than 100 mL/min (p ¼ 0.004). Significant predictors of PAL on univariate analyses were gender, presence of adhesions, FEV1 of less than 70%, grade of air leak, pattern of air leakage in the first 72 postoperative hours, and peak air leakage rate in the first 24 postoperative hours (Table 5). Among them, FEV1 of less than 70%, pattern of air leakage, and peak air leakage rate were significant predictors of PAL on multivariate analysis (Table 5), and jrj was less than 0.7 between each factor (Supplemental Table 1). There were 134 type I (44%), 113 type II (37%), and 61 type III (20%) pleural pressure patterns in the 308 study patients. All of the type A patients with no air leaks showed pleural pressure pattern type I or II. In contrast, all of the type B to D patients showed type III. Although pleural pressure was maintained at the preset value (–10 cm H2O) until the air leak resolved, a fluctuation in pleural pressure appeared just after the air leakage rate decreased to less than 20 mL/min, suggesting that information on the disappearance of an air leak is not solely derivable from the rate of air leakage but also from the pattern of pleural pressure. Table 6 summarizes the correlation between type I and type II pleural pressure patterns and the types of surgical procedures. The prevalence of lobectomy was significantly higher in type I than in type II patients (73% vs 43%, p < 0.001). In addition, the prevalence of right middle lobectomy was significantly higher in type II than in type I
Table 6. Relationships Between Pattern of Pleural Pressure and Pattern of Air Leak and Surgical Procedures Type I (n ¼ 134)
Type II (n ¼ 113)
Type III (n ¼ 61)
Variable
No. (%)
No. (%)
No. (%)
Pattern of air leak Surgical procedure Wedge resection Segmentectomy Lobectomy RML
Type A
Type A
Type B, C, D, or E
16 (12) 20 (15) 98 (73) 3
31 (27) 28 (25) 54 (48) 15
2 (3) 10 (16) 49 (80) 2
RML ¼ right middle lobectomy.
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patients who underwent lobectomy (15 of 54 [28%] vs 3 of 98 [3%], p ¼ 0.001). These findings indicate that the fluctuations in pleural pressure positively correlated with the size of the postoperative pleural space (Table 6).
Comment In this study we clarified the clinical utility of three aspects of objective chest tube management after pulmonary resection based on digital monitoring of pleural pressure and digital surveillance for air leakage. Although there is no standard definition of PAL in the literature, we defined PAL as an air leak exceeding 20 mL/ min persisting for 5 days or more after operation, based on the mean duration of postoperative hospital stay of 5.8 days in patients without postoperative air leaks (Table 3). First, we found that PALs can be predicted based on FEV1, peak air leakage rate during the first 24 hours after the operation, and the pattern of air leakage over the first 72 hours after the operation. Although several investigators have reported other predictors of PAL [2–4], no commonly accepted practical system for predicting PAL has yet been established. We found that accurately predicting PAL in patients with postoperative air leaks based solely on patient characteristics or intraoperative findings is difficult and that postoperative findings are more relevant. Here, we evaluated the role of the digital surveillance for air leaks for predicting PAL only in patients with postoperative air leaks. Brunelli and colleagues [10] reported that air leakage and the difference between maximum and minimum pleural pressures digitally monitored through the chest tube using a microelectronic medical sensor technology (Digivent; Millicore AB, Danderyd, Sweden) during postoperative hour 6 were reliable predictors of PAL for patients managed by conventional chest drainage after lobectomy. We found that the patterns as well as the rate of air leakage after the operation were also significant in predicting PAL.
Fig 3. The treatment strategy for patients with postoperative air leak based on the Thopaz system’s (Medela Healthcare, Baar, Switzerland) estimation of the rate of peak air leakage during the first 24 hours after the operation and the pattern of air leakage over the first 72 hours after the operation. (FEV1 ¼ forced expiratory volume in 1 second.)
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Second, we found that digital monitoring of pleural pressure and digital surveillance for air leaks make it possible to evaluate the point of air leak resolution. In principle, the digitally monitored thoracic drainage system acts to maintain the preset pleural pressure value during the air leak and stops working after the air leak seals, unless the pleural pressure significantly changes. As a result, pleural pressure is maintained at the preset value until the air leak has resolved. We noted a wider fluctuation of pleural pressure within the physiologic range in each patient appearing just after the air leak disappeared. This finding reiterates the concept that the patterns of air leakage rate and of pleural pressure are both important in detecting air leak disappearance. Third, we showed that the amplitude of pleural pressure is positively correlated with the size of the postoperative pleural space. Little is known about the mechanics of the pleural space and the physiology of pleural pressure after pulmonary resection. Refai and colleagues [11] showed that mean postoperative pleural pressures were similar after different types of lobectomies and ranged from –11 to –13 cm H2O, with the exception of right upper bilobectomy (–20 cm H2O). Based on these findings, a prospective randomized trial that compared regulated tailored suction (–11 to –20 cm H2O according to lobectomy type) with regulated seal (–2 cm H2O) using the digitally monitored thoracic drainage system was conducted in 100 consecutive patients who underwent lobectomy. The primary end point, the duration of air leakage, did not differ between groups [5], however, and an appropriate preset value for pleural pressure on the digitally monitored thoracic drainage system could not be established. We have shown that the amplitude of pleural pressure positively correlates with the size of the pleural space according to the extent of the surgical procedure (sublobar resections vs lobectomy). A further prospective comparative study to elucidate the appropriate preset pressure may be worthwhile, taking into consideration these differences in amplitude.
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The present study has some limitations. The main limitation is its retrospective nature, albeit that it was performed using prospectively collected data. The predictors of PAL and the clinical utility of the digital surveillance for air leaks and monitoring of pleural pressure shown in this study need to be validated in larger populations. The other limitation is that we cannot apply our findings directly to clinical practice using the existing digitally monitored thoracic drainage system (Thopaz). Although the digitally monitored thoracic drainage system used in this study does display real-time data for air leakage in 24-hour trends, air leakage patterns in 72-hour trends and pleural pressure patterns cannot be shared without exporting the data to a computer with commercial software. However, the next generation of this digital chest drainage system (Thopazþ, Medela Healthcare) provides not only continuous digital monitoring of pleural pressure and digital surveillance for air leaks but also a realtime readout of 72-hour trends, allowing clinical use at the bedside. The last limitation is that we could not perform a financial analysis because the precise data for the total cost of postoperative treatment and hospitalization, among other costs, was not available. It will be important to determine the effect of Thopaz on the medical financial system based on a well-planned prospective evaluation of the total cost. In summary, we elucidated two advantages of digital surveillance of air leakage and pleural pressure for decision making in chest drainage after pulmonary resection. First, the rate of peak air leakage during the first 24 hours after the operation and the pattern of air leakage during the first 72 hours after the operation were more useful for predicting PAL than previously reported predictive factors. If a peak air leak of 100 mL/min or more or type D or E air leakage patterns, or both, are observed 72 hours after the operation, aggressive management, such as pleurodesis or reoperation, or both, should be considered, especially in patients with FEV1 of less than 70% (Fig 3). Second, information on the disappearance of air leak was derivable not only from the change in the rate of air leakage but also from the increase in fluctuation of pleural pressure. The timing of chest tube removal can be determined objectively by a combination of these
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findings. Chest tube removal can be safely performed when the air leakage rate is less than 20 mL/min for more than 12 hours and fluctuation of pleural pressure appears. This work was partly supported by a Grant-in-Aid for Cancer Research from the Ministry of Health, Labour and Welfare of Japan and the Smoking Research Foundation.
References 1. Brunelli A, Cassivi SD, Halgren L. Risk factors for prolonged air leak after pulmonary resection. Thorac Surg Clin 2010;20: 359–64. 2. Brunelli A, Monteverde M, Borri A, Salati M, Marasco RD, Fianchini A. Predictors of prolonged air leak after pulmonary lobectomy. Ann Thorac Surg 2004;77:1205–10; discussion 1210. 3. Brunelli A, Varela G, Refai M, et al. A scoring system to predict the risk of prolonged air leak after lobectomy. Ann Thorac Surg 2010;90:204–9. 4. Cerfolio RJ, Bass CS, Pask AH, Katholi CR. Predictors and treatment of persistent air leaks. Ann Thorac Surg 2002;73: 1727–30; discussion 1730–1. 5. Brunelli A, Salati M, Pompili C, Refai M, Sabbatini A. Regulated tailored suction vs regulated seal: a prospective randomized trial on air leak duration. Eur J Cardiothorac Surg 2013;43:899–904. 6. McGuire AL, Petrcich W, Maziak DE, et al. Digital versus analogue pleural drainage phase 1: prospective evaluation of interobserver reliability in the assessment of pulmonary air leaks. Interact Cardiovasc Thorac Surg 2015;21:403–7. 7. Varela G, Jimenez MF, Novoa NM, Aranda JL. Postoperative chest tube management: measuring air leak using an electronic device decreases variability in the clinical practice. Eur J Cardiothorac Surg 2009;35:28–31. 8. Takamochi K, Oh S, Miyasaka Y, et al. Prospective randomized trial comparing buttressed versus nonbuttressed stapling in patients undergoing pulmonary lobectomy. Thorac Cardiovasc Surg 2014;62:696–704. 9. Yokomise H, Satoh K, Ohno N, Tamura K. Autoblood plus OK432 pleurodesis with open drainage for persistent air leak after lobectomy. Ann Thorac Surg 1998;65:563–5. 10. Brunelli A, Cassivi SD, Salati M, et al. Digital measurements of air leak flow and intrapleural pressures in the immediate postoperative period predict risk of prolonged air leak after pulmonary lobectomy. Eur J Cardiothorac Surg 2011;39: 584–8. 11. Refai M, Brunelli A, Varela G, et al. The values of intrapleural pressure before the removal of chest tube in noncomplicated pulmonary lobectomies. Eur J Cardiothorac Surg 2012;41:831–3.
Background. We sought to evaluate the clinical utility of chest tube management after pulmonary resection based on objective digital monitoring of pleural pressure and digital surveillance for air leaks. Methods. We prospectively recorded the perioperative data of 308 patients who underwent pulmonary resection between December 2013 and January 2016. We used information from a digital monitoring thoracic drainage system to measure peak air leakage during the first 24 hours after the operation, patterns of air leakage over the first 72 hours, and patterns of pleural pressure changes until the chest tubes were removed. Results. There were 240 patients with lung cancer and 68 patients with other diseases. The operations included 49 wedge resections, 58 segmentectomies, and 201 lobectomies. A postoperative air leak was observed in 61 patients (20%). A prolonged air leak exceeding 20 mL/ min lasting 5 days or more was observed in 18 patients
(5.8%). Multivariate analysis of various perioperative factors showed forced expiratory volume in 1 second below 70%, patterns of air leakage, defined as exacerbating and remitting or without a trend toward improvement, and peak air leakage of 100 mL/min or more were significant positive predictors of prolonged air leak. Fluctuations in pleural pressure occurred just after the air leakage rate decreased to less than 20 mL/min. Conclusions. Digital monitoring of peak air leakage and patterns of air leakage were useful for predicting prolonged air leak after pulmonary resection. Information on the disappearance of air leak could be derived from the change in the rate of air leakage and from the increase in fluctuation of pleural pressure.
P
In response, the Thopaz digitally monitored thoracic drainage system (Medela Healthcare, Baar, Switzerland) has been designed to provide objective measurements of air leakage and pleural pressure [5]. With this system, air leakage and pleural pressure can be accurately measured in mL/min and mm H2O, respectively. The rate of air leakage can be seen on a display in real time. Furthermore, the serial digital data for air leakage and pleural pressure during the presence of the chest tube can be retrospectively analyzed by exporting them to a personal computer with ThopEasy software (Medela Healthcare). Digital surveillance for air leakage is reported to reduce interobserver disagreement in decision making in the management of patients with chest tubes [6, 7], and the system obviates the empiric need to clamp the chest tube before removal to rule out the existence of occult small air leaks, which can lead to delayed pneumothorax formation.
rolonged air leak (PAL) is one of the major factors that delay early hospital discharge after pulmonary resection. The incidence of PAL after pulmonary lobectomy is reported to be 10% to 15% [1]. PAL sometimes results in serious complications such as empyema; therefore, early prediction and intervention for PAL is crucial. Risk factors for PAL include gender, smoking history, body mass index, preoperative steroid use, emphysema, decreased pulmonary function, pleural adhesions, type of lung resection, and location of the resection [2–4]. However, no commonly accepted criteria for the prediction of PAL in clinical practice have yet appeared. Because the traditional thoracic drainage system measures and grades air leaks in a subjective manner, interobserver disagreement on the presence of an air leak is frequent [5, 6], even among experienced surgeons.
Accepted for publication Jan 12, 2017. Address correspondence to Dr Takamochi, Department of General Thoracic Surgery, Juntendo University School of Medicine, 1-3, Hongo 3-chome, Bunkyo-ku, Tokyo 1130-8431, Japan; email: ktakamo@ juntendo.ac.jp.
Ó 2017 by The Society of Thoracic Surgeons Published by Elsevier Inc.
(Ann Thorac Surg 2017;-:-–-) Ó 2017 by The Society of Thoracic Surgeons
The Supplemental Table can be viewed in the online version of this article [http://dx.doi.org/10.1016/ j.athoracsur.2017.01.061] on http://www.annalsthoracic surgery.org.
0003-4975/$36.00 http://dx.doi.org/10.1016/j.athoracsur.2017.01.061
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Table 1. Patient Characteristics Variable Gender, No. Male Female Age, mean SD, y Smoking, No. Smoker Nonsmoker Smoking index, median (range) Primary disease, No. Lung cancer Metastatic lung tumor Pneumothorax Others Comorbidities, No. (%) Emphysema Interstitial pneumonia Diabetes mellitus Cardiac disease Medication use, No. (%) Steroid Anticoagulant or antiplatelet
Patients (N ¼ 308) 195 113 68 33 201 107 455 (0–4,410) 240 32 2 34 81 31 47 36
(26) (10) (15) (12)
5 (2) 40 (13)
Compared with the clinical utility of digital surveillance for air leakage, however, there is little evidence to support the digital monitoring of pleural pressure using a digital thoracic drainage system. Our goal in this study was to establish reliable criteria for the prediction of PAL based on the findings of digital monitoring of air leakage and to elucidate the clinical utility of the digital monitoring of pleural pressure.
Material and Methods This study was a retrospective analysis based on an electronic database and was performed under a waiver of authorization approved by the Juntendo University School of Medicine Institutional Review Board.
Patient Data We prospectively collected the postoperative data of 308 patients who were digitally monitored with the Thopaz system after undergoing pulmonary resection between December 2013 and January 2016. The Thopaz system was used for patients after pulmonary resection unselectively. We could not use it for all patients because only 5 Thopaz systems were available at our institute; thus, 578 patients Table 3. Postoperative Findings
Findings
Table 2. Intraoperative Findings Variable Grade of adhesions None Mild Moderate Severe Surgical procedure Wedge resection Segmentectomy Lobectomy Chest tubes, No. 1 2 3 Size of chest tubes 24F 28F Grade of air leak 0 1 2 3 Sealant use Yes No
No. (%) (N ¼ 308) 187 73 37 11
(61) (24) (12) (4)
49 (16) 58 (19) 201 (65) 303 (98) 4 (1.7) 1 (0.3) 302 (98) 6 (2) 153 81 60 14
(50) (26) (19) (5)
242 (79) 66 (21)
Postoperative air leak Present Absent Duration of air leak, days Duration of chest tube placement, days All patients Patients with postoperative air leaks Patients without postoperative air leaks Prolonged air leak (5 days) Duration of prolonged air leak, d Air leak at the time of chest tube removal 0 mL/min 0–10 mL/min 0–20 mL/min Fluid volume drained over the 24 hours before chest tube removal 200 mL 201–300 mL 301–400 mL Pleurodesis Abnormal findings on chest roentgenogram Subcutaneous emphysema Atelectasis Collapse Postoperative hospital length of stay, d All patients Patients with postoperative air leaks Patients without postoperative air leaks
No. (%) or Mean SD (N ¼ 308) 61 (20) 247 (80) 3.6 2.8 3.1 1.8 5.2 2.5 2.6 1.2 18 (5.8) 7.0 2.4 296 8 4
218 (71) 84 6 12 (3.9) 31 (10) 8 (3) 0 6.2 4.2 7.8 2.8 5.8 4.4
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were managed by the conventional drainage system during the same period of this study. Each surgical procedure was performed under the supervision of one of the attending thoracic surgeons with some residents. Segmentectomy and lobectomy was
TAKAMOCHI ET AL UTILITY OF A DIGITAL DRAINAGE SYSTEM
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performed by posterolateral, anterolateral, or axial open thoracotomy in all patients. Wedge resection was performed under minithoracotomy (<5 cm incision) or video-assisted thoracic surgery. Robotic surgery is not performed at our institution.
Fig 1. Patterns of air leakage. The blue line indicates the rate of air leakage. (A) Type A, no air leak (air leak <20 mL/min) was observed until the removal of the chest tube. (B) Type B, air leak gradually decreased. (C) Type C, although no air leak was observed immediately after the operation, delayed air leak occurred postoperatively. (D) Type D, repeated exacerbation and remission of air leak was observed. (E) Type E, air leak was observed without a trend toward improvement.
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thickness and firmness of lung parenchyma. A buttressed stapler (Endo GIA Tri-Staple Reinforce; Covidien Inc, Tokyo, Japan) was used for dividing severely emphysematous lung parenchyma. The operative technique was standardized for all surgeons.
We used conventional automatic surgical staplers for wedge resection of lung parenchyma, developing the intersegmental plane at segmentectomy, dividing incomplete fissures at lobectomy, and closing the bronchus. The size of cartridges was selected according to the
100
18
90
16
80
14
70
5cmH2O
12
60
10
50
8
40
6
30
4
20
2
10 0
0 0
4
8
12
16
20
24
28
32
36
40
44
48
52
56
60
64 (hr)
Postoperative period
B
100
18
90
16
80
Pressure (cmH2O)
20
14
70
5cmH2O
12
60
10
50
8
40
6
30
4
20
2
10
0
0
0
4
8
12
16
20
24
28
32
36
40
44
48
52
56
60
(hr)
Air flow (mL/min)
Pressure (cmH2O)
20
Air flow (mL/min)
A
Postoperative period
C
Presence of air leak
Absence of air leak
30
200
Pressure (cmH2O)
160 140
20
120
15
100 80
10
Air flow (mL/min)
180 25
60 40
5
20 0
0 0
4
8
12
16
20
24
28
32
36
40
44
48
52
56
60
64
(hr)
Postoperative period
Fig 2. Patterns of pleural pressure. The blue line indicates the rate of air leakage, and the red line indicates pleural pressure. The green arrow indicates the time of air leak resolution. (A) Type I, fluctuations of pleural pressure 5 cm H2O were continuously observed. (B) Type II, fluctuations of pleural pressure <5 cm H2O were continuously observed. (C) Type III, increased fluctuations in pleural pressure appeared just after the air leak level decreased to <20 mL/min.
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TAKAMOCHI ET AL UTILITY OF A DIGITAL DRAINAGE SYSTEM
An intraoperative air leak test (applied pressure 20 cm H2O) was performed using a sterile saline solution. The amount of intraoperative air leak was evaluated according to the following scoring system: grade 0 ¼ no detectable air bubbles; 1 ¼ countable air bubbles; 2 ¼ stream of bubbles; 3 ¼ coalesced bubbles (air bubbles join to form one continuous stream of air) [8]. Additional suture repair was applied when an air leak was detected. Sealant materials, such as fibrin glues, synthetic sealants, and collagen patches coated with fibrinogen and thrombin, were used if an air leak persisted. Further air leak testing was not performed after the sealant materials were used. The incidence of intraoperative air leak at the first air leak test just after pulmonary resection and that of postoperative air leak at entering an intensive care unit or a recovery room was recorded. The digitally monitored thoracic drainage system was set at a regulated pressure level of –10 cm H2O immediately after the operation until chest tube removal. The chest tubes were removed when the air leakage rate was less than 20 mL/min for more than 12 hours and the amount of pleural effusion drainage was 300 mL/day or less. Among patients with air leaks continuing for 5 or more days, pleurodesis by intrathoracic administration of the sclerosing agent OK432, with or without 50 mL of autologous blood through the chest tube, was performed according to the clinical judgment of the attending doctor for each patient [9].
Data Collection Table 1 reports patient characteristics, Table 2 reports intraoperative findings, and Table 3 reports postoperative findings. The digital data for air leakage and pleural pressure during the presence of the chest tube were exported to a personal computer with the ThopEasy software and analyzed. Peak air leakage levels over the first 24 hours after operation were examined. Figure 1 illustrates the different patterns of air leakage during the first 72 hours after the operation, defined as type A, no air leakage; type B, gradually decreasing air leakage; type C, a postoperative de novo air leak; type D, an exacerbating and remitting air leak; and type E, an air leak without a
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trend toward improvement. Figure 2 demonstrates patterns of pleural pressure until chest tube removal, defined as type I stable fluctuations in pleural pressure of 5 cm H2O or more; type II, stable fluctuations in pleural pressure of less than 5 cm H2O; and type III, an abrupt fluctuation in pleural pressure just after the air leakage rate decreased to less than 20 mL/min.
Statistical Analysis Numeric variables between the groups were compared by the unpaired t test. Categoric variables between the groups were compared by the c2 test or the Fisher exact test. In patients with postoperative air leak, univariate and multivariate analyses were performed using a forward stepwise logistic regression model to determine the relationship between the incidence of PAL and the following clinical factors: gender; age; smoking status; presence of comorbidities such as emphysema, interstitial pneumonia, diabetes mellitus, steroid use, and anticoagulant or antiplatelet treatment; presence of adhesions; forced expiratory volume in 1 second (FEV1); vital capacity; diffusion capacity of the lung for carbon monoxide; type of surgical procedure (wedge resection vs segmentectomy or lobectomy); grade of air leak; sealant use; pattern of air leakage in the first 72 postoperative hours; and peak air leakage rate in the first 24 postoperative hours. To eliminate confounding variables, we calculated the Pearson productmoment correlation coefficient (r). Among the significant predictive factors of PAL in univariate analyses, factors proving the absence of strong correlation (jrj < 0.7) were entered into multivariate analysis. A p value of less than 0.05 was considered to be statistically significant. Statistical analyses were performed using SPSS 20.0 software (IBM Corp, Armonk, NY).
Results The cohort comprised 195 men and 113 women, 201 smokers and 107 never smokers, and 240 patients with lung cancer and 68 with other diseases. The operations included 49 wedge resections, 58 segmentectomies, and
Table 4. Duration of Air Leaks and the Incidence of Prolonged Air Leak According to Pattern of Air Leak and Peak Air Leak
Variable Patterns of air leakage Type B Type C Type D Type E At peak air leakage <100 mL/min 100 mL/min 200 mL/min 300 mL/min 400 mL/min PAL ¼ prolonged air leak 5 days.
No.
Duration of Air Leak
Duration of Chest Tube Placement
Incidence of PAL
Mean SD, d
Mean SD, d
No. (%)
23 15 11 12
2.5 1.7 3.3 6.6
2.2 2.2 2.4 3.5
4.3 4.4 5.5 7.8
1.7 2.3 1.9 2.8
4 1 4 9
(17) (7) (36) (75)
34 27 16 11 9
2.3 4.5 5.4 6.3 6.7
2.2 3.5 3.6 3.8 4.1
4.6 5.9 6.6 7.2 7.6
2.0 2.9 3.1 3.3 3.5
5 13 10 8 7
(15) (48) (63) (73) (78)
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Table 5. Univariate and Multivariate Analyses of Predictors of Prolonged Air Leak in Patients With Postoperative Air Leak (n ¼ 61)
Variable Gender Female Male Age <70 y 70 y Smoking (pack-year) 5 >5 Emphysema No Yes Interstitial pneumonia No Yes Diabetes mellitus No Yes Steroid use No Yes Anticoagulant or antiplatelet use No Yes Adhesions No Yes FEV1 (%) 70% <70% Vital capacity (%) 80% <80% DLCO (%) 40% <40% Surgical procedures Wedge resection Seg or Lob Grade of air leak 0 or 1 2 or 3 Sealant use No Yes Patterns of air leak Type B or C Type D or E
Patients
PAL
Univariate Analysis
No.
No.
Odds Ratio (95% CI)
20 41
2 16
1.00 (reference) 5.76 (1.40–39.4)
23 38
6 12
1.00 (reference) 1.31 (0.42–4.37)
18 43
6 12
1.00 (reference) 0.67 (0.24–2.64)
43 18
11 7
1.00 (reference) 1.85 (0.56–5.98)
55 6
18 0
a
1.00 (reference) 0.67 (0.56–0.81)a
47 14
16 2
1.00 (reference) 0.32 (0.05–1.38)
57 4
17 1
1.00 (reference) 0.78 (0.04–6.63)
52 9
16 2
1.00 (reference) 0.60 (0.09–3.02)
30 31
5 13
1.00 (reference) 3.61 (1.14–13.0)
36 25
6 12
1.00 (reference) 4.62 (1.47–15.9)
58 3
18 0
a
1.00 (reference) 0.69 (0.58–0.82)a
47 9
13 3
1.00 (reference) 1.31 (0.25–5.77)
2 59
0 18
1.00 (reference)a 1.44 (1.22–1.70)a
36 25
6 12
1.00 (reference) 4.62 (1.47–15.9)
7 54
0 18
a
1.00 (reference) 1.50 (1.24–1.81)a
38 23
5 13
1.00 (reference) 8.58 (2.59–32.6)
Multivariate Analysis p
Odds Ratio (95% CI)
0.013
p 0.367
0.647
0.674
0.305
0.110a
0.134
0.836
0.595
0.028
0.251
0.008
0.009 1.00 (reference) 10.2 (1.80–58.1)
0.343a
0.733
0.493a
0.008
0.351
0.074a
<0.001
0.002 1.00 (reference) 16.4 (2.87–93.2) (Continued)
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Table 5. Continued
Variable Peak air leak <100 mL/min 100 mL/min
Patients
PAL
Univariate Analysis
No.
No.
Odds Ratio (95% CI)
34 27
5 13
1.00 (reference) 5.39 (1.68–19.7)
Multivariate Analysis p
Odds Ratio (95% CI)
p
0.004
0.035 1.00 (reference) 4.97 (1.12–22.0)
a
The odds ratio and p value could not be analyzed by the logistic regression model because 0 was one of the numbers in the columns. Therefore, odds ratio and p value analyzed by the c2 test are shown. However, these factors were not entered to the multivariate logistic regression model.
CI ¼ confidence interval; DLCO ¼ diffusion capacity of the lung for carbon monoxide; lobectomy; PAL ¼ prolonged air leak 5 days; Seg ¼ segmentectomy.
201 lobectomies. A buttressed stapler was used in 9 patients in this study: 6 for dividing incomplete fissures at lobectomy, 2 for developing the intersegmental plane at segmentectomy, and 1 for wedge resection of lung parenchyma. No patient required ventilator management postoperatively. No patient needed additional chest tube placement because of drainage failure by the Thopaz system resulting in postoperative pneumothorax and progressive severe subcutaneous emphysema during chest tube placement. After chest tube removal, no pneumothorax or progressive severe subcutaneous emphysema was observed. Slight subcutaneous emphysema was depicted on the chest roentgenogram just after the operation in 32 of 308 patients (10%) but spontaneously resolved in all patients during hospitalization. Air leakage patterns in patients with subcutaneous emphysema were type A in 18 (7%), type B in 5 (2%), type C in 1 (7%), type D in 2 (18%), and type E in 5 (42%). The regulated pressure level of –10 cm H2O on the digitally monitored thoracic drainage system was not changed until chest tube removal for all patients regardless of the status of postoperative air leak. Intraoperative air leak, postoperative air leak, and PAL were observed in 155 (50%), 61 (20%), and 18 of 308 patients (5.8%), respectively. The mean postoperative hospital length of stay was longer in patients with postoperative air leaks. Pleurodesis was performed for 12 patients (3.9%). Air leakage patterns in patients who ultimately received pleurodesis were type B in 2, type C in 1, type D in 2, and type E in 7. Table 4 reveals the frequency of PAL according to air leakage pattern. The
FEV1 ¼ forced expiratory volume in 1 second;
Lob ¼
risk of PAL was higher in patients showing type D or E air leakage patterns than in those showing type B or C (p < 0.001). The risk of PAL was higher in patients with a peak air leak of 100 mL/min or more compared with those with less than 100 mL/min (p ¼ 0.004). Significant predictors of PAL on univariate analyses were gender, presence of adhesions, FEV1 of less than 70%, grade of air leak, pattern of air leakage in the first 72 postoperative hours, and peak air leakage rate in the first 24 postoperative hours (Table 5). Among them, FEV1 of less than 70%, pattern of air leakage, and peak air leakage rate were significant predictors of PAL on multivariate analysis (Table 5), and jrj was less than 0.7 between each factor (Supplemental Table 1). There were 134 type I (44%), 113 type II (37%), and 61 type III (20%) pleural pressure patterns in the 308 study patients. All of the type A patients with no air leaks showed pleural pressure pattern type I or II. In contrast, all of the type B to D patients showed type III. Although pleural pressure was maintained at the preset value (–10 cm H2O) until the air leak resolved, a fluctuation in pleural pressure appeared just after the air leakage rate decreased to less than 20 mL/min, suggesting that information on the disappearance of an air leak is not solely derivable from the rate of air leakage but also from the pattern of pleural pressure. Table 6 summarizes the correlation between type I and type II pleural pressure patterns and the types of surgical procedures. The prevalence of lobectomy was significantly higher in type I than in type II patients (73% vs 43%, p < 0.001). In addition, the prevalence of right middle lobectomy was significantly higher in type II than in type I
Table 6. Relationships Between Pattern of Pleural Pressure and Pattern of Air Leak and Surgical Procedures Type I (n ¼ 134)
Type II (n ¼ 113)
Type III (n ¼ 61)
Variable
No. (%)
No. (%)
No. (%)
Pattern of air leak Surgical procedure Wedge resection Segmentectomy Lobectomy RML
Type A
Type A
Type B, C, D, or E
16 (12) 20 (15) 98 (73) 3
31 (27) 28 (25) 54 (48) 15
2 (3) 10 (16) 49 (80) 2
RML ¼ right middle lobectomy.
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patients who underwent lobectomy (15 of 54 [28%] vs 3 of 98 [3%], p ¼ 0.001). These findings indicate that the fluctuations in pleural pressure positively correlated with the size of the postoperative pleural space (Table 6).
Comment In this study we clarified the clinical utility of three aspects of objective chest tube management after pulmonary resection based on digital monitoring of pleural pressure and digital surveillance for air leakage. Although there is no standard definition of PAL in the literature, we defined PAL as an air leak exceeding 20 mL/ min persisting for 5 days or more after operation, based on the mean duration of postoperative hospital stay of 5.8 days in patients without postoperative air leaks (Table 3). First, we found that PALs can be predicted based on FEV1, peak air leakage rate during the first 24 hours after the operation, and the pattern of air leakage over the first 72 hours after the operation. Although several investigators have reported other predictors of PAL [2–4], no commonly accepted practical system for predicting PAL has yet been established. We found that accurately predicting PAL in patients with postoperative air leaks based solely on patient characteristics or intraoperative findings is difficult and that postoperative findings are more relevant. Here, we evaluated the role of the digital surveillance for air leaks for predicting PAL only in patients with postoperative air leaks. Brunelli and colleagues [10] reported that air leakage and the difference between maximum and minimum pleural pressures digitally monitored through the chest tube using a microelectronic medical sensor technology (Digivent; Millicore AB, Danderyd, Sweden) during postoperative hour 6 were reliable predictors of PAL for patients managed by conventional chest drainage after lobectomy. We found that the patterns as well as the rate of air leakage after the operation were also significant in predicting PAL.
Fig 3. The treatment strategy for patients with postoperative air leak based on the Thopaz system’s (Medela Healthcare, Baar, Switzerland) estimation of the rate of peak air leakage during the first 24 hours after the operation and the pattern of air leakage over the first 72 hours after the operation. (FEV1 ¼ forced expiratory volume in 1 second.)
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Second, we found that digital monitoring of pleural pressure and digital surveillance for air leaks make it possible to evaluate the point of air leak resolution. In principle, the digitally monitored thoracic drainage system acts to maintain the preset pleural pressure value during the air leak and stops working after the air leak seals, unless the pleural pressure significantly changes. As a result, pleural pressure is maintained at the preset value until the air leak has resolved. We noted a wider fluctuation of pleural pressure within the physiologic range in each patient appearing just after the air leak disappeared. This finding reiterates the concept that the patterns of air leakage rate and of pleural pressure are both important in detecting air leak disappearance. Third, we showed that the amplitude of pleural pressure is positively correlated with the size of the postoperative pleural space. Little is known about the mechanics of the pleural space and the physiology of pleural pressure after pulmonary resection. Refai and colleagues [11] showed that mean postoperative pleural pressures were similar after different types of lobectomies and ranged from –11 to –13 cm H2O, with the exception of right upper bilobectomy (–20 cm H2O). Based on these findings, a prospective randomized trial that compared regulated tailored suction (–11 to –20 cm H2O according to lobectomy type) with regulated seal (–2 cm H2O) using the digitally monitored thoracic drainage system was conducted in 100 consecutive patients who underwent lobectomy. The primary end point, the duration of air leakage, did not differ between groups [5], however, and an appropriate preset value for pleural pressure on the digitally monitored thoracic drainage system could not be established. We have shown that the amplitude of pleural pressure positively correlates with the size of the pleural space according to the extent of the surgical procedure (sublobar resections vs lobectomy). A further prospective comparative study to elucidate the appropriate preset pressure may be worthwhile, taking into consideration these differences in amplitude.
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The present study has some limitations. The main limitation is its retrospective nature, albeit that it was performed using prospectively collected data. The predictors of PAL and the clinical utility of the digital surveillance for air leaks and monitoring of pleural pressure shown in this study need to be validated in larger populations. The other limitation is that we cannot apply our findings directly to clinical practice using the existing digitally monitored thoracic drainage system (Thopaz). Although the digitally monitored thoracic drainage system used in this study does display real-time data for air leakage in 24-hour trends, air leakage patterns in 72-hour trends and pleural pressure patterns cannot be shared without exporting the data to a computer with commercial software. However, the next generation of this digital chest drainage system (Thopazþ, Medela Healthcare) provides not only continuous digital monitoring of pleural pressure and digital surveillance for air leaks but also a realtime readout of 72-hour trends, allowing clinical use at the bedside. The last limitation is that we could not perform a financial analysis because the precise data for the total cost of postoperative treatment and hospitalization, among other costs, was not available. It will be important to determine the effect of Thopaz on the medical financial system based on a well-planned prospective evaluation of the total cost. In summary, we elucidated two advantages of digital surveillance of air leakage and pleural pressure for decision making in chest drainage after pulmonary resection. First, the rate of peak air leakage during the first 24 hours after the operation and the pattern of air leakage during the first 72 hours after the operation were more useful for predicting PAL than previously reported predictive factors. If a peak air leak of 100 mL/min or more or type D or E air leakage patterns, or both, are observed 72 hours after the operation, aggressive management, such as pleurodesis or reoperation, or both, should be considered, especially in patients with FEV1 of less than 70% (Fig 3). Second, information on the disappearance of air leak was derivable not only from the change in the rate of air leakage but also from the increase in fluctuation of pleural pressure. The timing of chest tube removal can be determined objectively by a combination of these
TAKAMOCHI ET AL UTILITY OF A DIGITAL DRAINAGE SYSTEM
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findings. Chest tube removal can be safely performed when the air leakage rate is less than 20 mL/min for more than 12 hours and fluctuation of pleural pressure appears. This work was partly supported by a Grant-in-Aid for Cancer Research from the Ministry of Health, Labour and Welfare of Japan and the Smoking Research Foundation.
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