Eur J Cardiothorac Surg 1999;15:7-10
© 1999 Elsevier Science NL
The threshold for air leak: stapled versus sutured human bronchi, an experimental study
A. El-Gamela,
G.M.K. Tsangb,
D.C.T. Watsonc
a Department of Cardiothoracic Surgery, Wythenshawe Hospital, Southmoor Road, Manchester M23 LT, UK
b Department of Thoracic Surgery, Heartland Hospital, Birmingham, UK
c Department of Thoracic Surgery, Norfolk and Norwich Hospital, Norwich, UK
Received 13 May 1998;
received in revised form 28 September 1998;
accepted 11 November 1998.
Corresponding author. Tel.: +44-61-998-7070; fax: +44-61-291-2091.
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Abstract
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Background: Little is known about the integrity of staple-closure of the bronchus and its tolerance to normal mechanical stresses (cough, sneezing, etc.) in the immediate early post-operative period. There are few studies which tested the mechanical strength of stapled bronchial closure compared with manually closed bronchi using the threshold for fluid leak across the bronchial suture line which differs from air. Material and methods: Intact cadaveric tracheobronchial tree (n=40) were selected, age range from 55 to 70, of which 60% were males. They were divided into two groups: group A, 20 left bronchi were closed with RLV 30 Ethicon® 4.8 mm bronchial stapler; group B, 20 were closed with 4 0 Prolene® simple interrupted sutures. All specimens were intubated with endotracheal tube and submerged under water before testing the immediate air leak with the standard 40 mm Hg inflation pressure. Inflation pressure was increased until air leak was detected. The stapled closures were resected and subjected to radiological examination. Results: No air leak was detected in any bronchus at 40 mmHg regardless of the closure technique. The median leakage pressure was significantly higher in the hand sutured bronchi compared to the stapled group (200 vs. 105 mmHg, respectively) and 50% (n=10) leaked from multiple sites in the stapled group compared with leakage from one site only in group B, this difference was statistically significant P<0.001. The radiological appearance of the staples maintained the B configuration, recommended by the manufacturer as a sign of sound application. Conclusion: Hand sutured bronchi tolerated higher inflation pressure compared with the stapled ones before leaking air. Air leak at high pressure occurs in the presence of intact staples.
Key Words: Bronchial fistula • Bronchial closure • Suture versus staples • mechanical factors
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Introduction
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Bronchopleural fistula (BPF) following pneumonectomy is associated with high mortality
[1]
[2]
[3]. Its development is multifactorial
[4], but of paramount importance are the techniques used in bronchial stump closure and in particular its resistance to air leaks early post-operatively which could be a source of contamination to the pneumonectomy space
[5]
[6]
[7]. Despite this there is no consensus as to the best technique. Since the introduction of mechanical staplers by Amosov
[8], approximately 50% of bronchial stumps are closed by staplers
[9]. Yet there has been no prospective randomized clinical trial comparing this relatively new technique to traditional hand sewn method of closing the bronchial stump
[10].
There are several clinical series reporting comparable incidence of bronchopleural fistulae regardless of the closure technique
[9]
[10]
[11]
[12]. Mechanical stability of the bronchial closure may contribute to its early post-operative tolerance to abnormal stress before sound healing is well established following pneumonectomy. Little is known about the integrity of staple-closure of the bronchus and its tolerance to normal mechanical stresses (cough, sneezing etc.) in comparison to suture closure. This study compares the integrity of the bronchial stump following hand sewn with stapled closure by comparing the immediate air leakage pressures in fresh human cadaveric bronchi in the age range when pulmonary resection is most frequent. Cadavers were selected to exclude the effect of dynamic factors on bronchial stump integrity (blood supply, healing). Staple closures were compared with suture closures.
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Materials and methods
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Forty human cadavers, 
50-years old (average age, 56 years; range, 50 to 70 years) that were examined in the pathology department (30 at Birmingham Heartland Hospital, 10 at Wythenshawe Hospital) within 24–48 h of death, served as the study group. There were 18 men and 12 women all of who died of non-respiratory causes. All specimens were dissected so that the intact tongue, larynx, trachea and main bronchi with surrounding tissues remained en bloc without perforation. All bronchi were cleaned of areolar tissue and washed to remove any remaining blood and clots. They were then randomized into either group A or B.
Group A consisted of 20 specimens. A RLV 30 Ethicon stapling device (Ethicon, Edinburgh, UK) was used to close the left main bronchus flushed to the carina with a staggered, parallel double row of 4.8 mm of staples placed transversely to the long axis of the bronchus with the posterior jaw in contact with the membranous part of the bronchus. The first stapler line was resected and X-rayed, then a second application was performed. A bronchial clamp was applied to the right main bronchus. Group B consisted of 20 specimens with the left main bronchi closed by hand suturing with 4/0 simple interrupted Prolene placed at 2–3 mm apart and tied six knots (four sliding followed by two surgical) to ensure secure approximation of the cut edges.
Determination of air leakage pressures was performed by intubating the specimens with a size eight endotracheal tube followed by inflation of the cuff. The distal end of the endotracheal tube was sited by palpation at approximately 2 cm above the carina. The proximal end was connected to a sphygmomanometer (
Fig. 1 ) so that the intraluminal pressure can be increased by inflation and monitored by the mercury column. The specimens were submerged in water and the intrabronchial pressures gradually increased until leakage was observed. The bronchial stumps were then excised. Group A was X-rayed and group B visually examined for the disruption of the suture line.
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Statistical analysis
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Bronchial leakage pressures were non-parametric. Wilcoxon signed rank test was used to test for differences between group A and B and was accepted as significant if P<0.05.
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Results
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Bronchial leakage pressures are shown graphically in
Fig. 2
. The median leakage pressures for hand sewn closure and stapled closure were 200 mmHg (range 150 to 300 mmHg) and 105 mmHg (range 45 to 300 mmHg), respectively (Wilcoxon signed rank test P<0.001). Leakage occurred at the end of the bronchial stumps following hand-sewn closure and from multiple sites at the staple puncture holes on the membranous portion of bronchus following stapled closure. Radiological appearance of the staples maintained the B configuration, as recommended by the manufacturers as a sign of sound application, and visual examination did not reveal disruption in the hand sewn bronchial stumps.
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Discussion
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These results show that following hand sewn closure of the bronchus with simple interrupted Prolene, the bronchial stump can withstand significantly higher pressures when compared with stapled closure. It was also evident that the radiological appearance of an intact staple line or a visually intact hand sewn bronchial stump does not exclude a bronchial leak.
Incidence of post pneumonectomy BPF has been reported as high as 15.2%
[13] with an expected mortality of approximately 30%
[5]
[14]
[15]. An increase in incidence has been associated with advanced age, the presence of endobronchitis, preoperative radiotherapy and underlying malignant disease
[16]
[17]. However it is believed that the operative technique used in bronchial closure is of paramount importance
[9]
[10]
[11]
[12]
[18]. Therefore, various technical measures have been devised to reduce the incidence of BPF. These measures have included preservation of the peribronchial tissue and vascular supply and the avoidance of long bronchial stumps
[4]
[19], the use of non-crushing clamps and the creation of a membranous flap sutured to the cartilaginous ring and covering the stump with mediastinal tissue
[13]
[15]
[18], the inversion of membranous margins following removal of the cartilaginous ring, and the use of monofilament non-absorbable sutures including staples
[20]. There is no consensus as to the best technique but there has been a consistent trend towards the use of non-reactive and non-absorptive suture material to reduce inflammatory response at the closure line
[21]. Hence the use of Prolene for hand suturing and stainless steel and subsequently, titanium staples are gaining in popularity.
Although series using staple closures have reported a low incidence of BPF, there appears to be high overall variability
[2]
[13]
[15]
[22]. Mechanical staple failure, however, may result in disastrous high incidence of BPF
[13] and many believe that thickened bronchi seen in chronic inflammation and proximally sited tumours may be contraindications to stapling
[23]. Nevertheless experimental differences do exist which may have clinical implications. For instance Huer
[24] has shown that the endobronchial pressures may be as high as 200 mmHg during coughing, suggesting that there may be a difference in the air leakage rate between hand sewn and staple closed bronchial stumps during early post-operative recovery, it is possible that early contamination of the pneumonectomy space may be the cause for later space infection and the development of late BPF. Early mechanical integrity is also important maintaining an air tight and water tight barrier between resection space and the remnant lung to avoid aspiration and mediastinal shifts following resection.
Differences between our results and those reported by Scott
[7] may be due to different experimental materials and design. In particular we have measured immediate leakage pressures and therefore, cannot be compared with situations where some degree of healing had been established.
The clinical implication of the difference demonstrated by this study can only be determined by examining the relevant clinical outcomes (incidence of bronchopleural fistula) in a prospective randomized trial comparing different techniques of bronchial closure. It was evident from our experiment that the radiological appearance of an intact staple line does not exclude a bronchial leak.
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Acknowledgments
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We thank Ethicon (Edinburgh, UK), for providing the stapling devices and the cartridges used in this study. We also thank Dr. H. Doran for laboratory assistance, Mr. G. Whitehurst for photography, Mr. P. Somerset for the illustrations, and the department of statistics Manchester University.
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Abstract
Introduction
