Motion-activated prevention of clogging and maintenance of patency of indwelling chest tubes Jamshid H. Karimova, Raymond Dessoffya, Mariko Kobayashia, David T. Dudzinskib, Ryan S. Klatteb, Jacqueline Kattarc, Nader Moazamia,d and Kiyotaka Fukamachia,* a b c d
Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA Medical Device Solutions, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA Atrial Fibrillation Innovation Center, Global Cardiovascular Innovation Center, Cleveland, OH, USA Department of Thoracic and Cardiovascular Surgery, Kaufman Center for Heart Failure, Miller Family Heart and Vascular Institute, Cleveland Clinic, Cleveland, OH, USA
* Corresponding author. Department of Biomedical Engineering/ND20, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195. Tel: +1-216-4459344; fax: +1-216-4449198; e-mail: [email protected] (K. Fukamachi). Received 25 November 2013; received in revised form 31 January 2014; accepted 18 February 2014
Abstract OBJECTIVES: We designed a device that applies motion-activated energy (vibration) to prevent chest-tube clogging and maintain tube patency. We evaluated the efficacy of this device in vitro and in vivo. METHODS: The motion-activated system (MAS) device assembly comprises a direct current motor with an eccentric mass (3.2 g, centroid radius of 4.53 mm) affixed to its motor shaft. The device was tested in vitro using a model of an obstructed chest tube, with clots of bovine blood and human thrombin. The in vivo study (in nine healthy pigs, 46.0 ± 3.3 kg) involved a bilateral minithoracotomy and placement of 32-Fr chest tubes (with and without the device). Whole autologous blood (120 ml) was injected every 15 min into the right and left chest each over 120 min total. RESULTS: Chest-tube drainage over these 2 h using the MAS was significantly higher than that without the device (369 ± 113 ml vs 209 ± 115 ml; P = 0.027). CONCLUSIONS: Our results suggest that the motion-activation of the chest tubes may be an effective tool to maintain chest tubes patent. Further optimization of this technology is required to obtain more consistent prevention of clot deposition within or outside the chest tubes. Keywords: Haemothorax • Pleural space (drainage • management) • Pneumothorax • Surgery • Complications • Chest
INTRODUCTION It is common for patients undergoing cardiothoracic surgery to have clinical conditions that require the placement of chest tubes to drain blood, air or fluids. The functionality of chest-tube drainage must be properly maintained postoperatively [1]. However, occlusion of these chest tubes is not rare [2], and it is not uncommon for caregivers to think that the chest tube is completely patent, when in fact, the tube can be partially or completely occluded [3]. When blood encounters the chest-tube surface, despite the biocompatibility of the tube material itself, a coagulation cascade is initiated that can lead to partial or complete chest-tube clogging. Chest-tube clogging with blood and other fibrinous material can contribute to retained haemothorax, pleural effusion and haemodynamic compromise [4]. To date, there is no reliable method of preventing chest-tube clogging. Most chest tubes are made of polyvinyl chloride or silicone and have different diameters and shapes [5]. A negative suction remains the only actively reliable component to assist with the removal of blood, clots and fluids from the chest [6, 7].
To address the issue of chest-tube clogging, we have designed a device which applies motion-activated energy (vibration) primarily to prevent the adhesion of clots within the chest tube lumen (as well as to the outer surface) and thus maintain patency and proper function. We report the initial in vitro and in vivo evaluation outcomes with the motion-activated system (MAS).
MATERIALS AND METHODS The MAS device (Fig. 1) applies vibrational motion to cylindrical standard chest tubes to prevent their clogging and to maintain patency and proper functioning postoperatively. The SOLIDWORKS® solid modelling (three-dimensional (SD) computer-aided design) software (Dassault Systèmes, Vélizy-Villacoublay, France) for design and an Objet350 Connex 3-D printer (Stratasys, Minneapolis, MN, USA) were used for rapid prototyping. The prototype consisted of a modified direct current (DC) motor (UC-2803S-19160, Sinotech, Portland, OR) with an eccentric mass (3.2 g, centroid radius of 4.53 mm) affixed to the motor shaft (spinning axis parallel with chest tube centreline). The device is fabricated with two openings
© The Author 2014. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
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NEW IDEAS – THORACIC
Interactive CardioVascular and Thoracic Surgery 19 (2014) 1–5 doi:10.1093/icvts/ivu089 Advance Access publication 7 April 2014
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Figure 1: Diagram of the motion-activated system. (A) 3D images of the motion-activated chest-tube clogging prevention device. Drainage flow direction through the tube is indicated (red arrow). (B) Artistic rendering of the device in clinical use (each device unit is externally coupled with a chest tube). CT: chest tube; PC: power cable.
(parallel and perpendicular to DC axial orientation) (Fig. 2). Chesttube fixation and motion transmission were tested in both openings, but we did not try to obtain any evidence for what direction with respect to the device would be a better option versus another. For this reason, we have empirically chosen the parallel opening, which was used in all cases. Motion forces were varied by adjusting the current. The MAS device body is tightly coupled (with no tube compression) to the extrathoracic portion of chest tubes that are inserted into the chest in a standard fashion. The external end of the chest tube is connected to a collection canister with a vacuum suction attached (set at −20 cm H2O). When the device is turned on, motion is conveyed to the functional portion (segment with holes and openings) of the chest tube (towards the internal portion of the tube and the tip). Being an external unit, the device does not compromise the internal sterility of chest-tubes. In addition, the MAS is the only device that prevents clot attachment to the tube’s outer surface as well, which in turn improves drainage through the tube’s holes, which are kept open. This vibrational motion and its unique ‘swirling’ effect on the fluid inside the cylindrical tube were specifically designed to enhance the functional characteristics of the chest tubes currently used in cardiothoracic surgical practice. Preliminary in vitro tests were set up to assess clotting inhibition within standard chest drainage tubes versus those coupled with an initial device prototype. Standard 32-Fr polyvinyl chloride chest tubes (Covidien®, Mansfield, MA, USA) were clamped at one end and filled with whole calf blood preserved with the anticoagulant mix of citrate-phosphate-dextrose-adenine. Test and Control tubes were suspended vertically; blood was injected with human thrombin (Gelfoam Plus®, Baxter, Deerfield, IL, USA) to induce clotting. The Test tube was fitted with a MAS prototype and subjected to vibration; the Control tube was not vibrated. The in vivo study protocol was approved by Cleveland Clinic’s Institutional Animal Care and Use Committee, and all the animals received humane care in compliance with the ‘Guide for the Care and Use of Laboratory Animals’ (Institute of Laboratory Animal Resources, Commission on Life Sciences, National Research Council, National Academy Press, Washington, DC, USA, 2011) and institutional guidelines. In nine healthy pigs (Yorkshire mix, 46.0 ± 3.3 kg [M. Fanning Farms, Howe, IN, USA]), acute haemothorax was modelled per our
Figure 2: The SOLIDWORKS® solid modelling of the device design in four projections is shown. The opening for the chest tube insertion is indicated with an asterisk. CE: cable exit site; DCM: direct current motor; EM: eccentric mass units.
previously established method to evaluate chest-tube drainage [8] (Fig. 3). Anaesthesia was induced with an intramuscular injection of ketamine (20 mg/kg) and xylazine (5 mg/kg) and inhaled 5% isoflurane. With the animals in the supine position, two arterial lines were placed in the left and right carotid arteries for blood withdrawal. A bilateral minithoracotomy (sixth intercostal space) was constructed to insert blood infusion catheters and place 0– polypropylene sutures (Ethicon, Somerville, NJ, USA) at the edge (lower lobe) of both lungs to create an injury after chest closure. Two regular 32-Fr chest tubes (Control and MAS) were inserted (seventh intercostal space) bilaterally, and the thoracotomy was closed in layers. To ensure that motion was effectively conveyed towards the tip of the tube, the acceleration data in three axes (x, y and z) were measured with three accelerometers mounted on the device and chest tube itself before the blood injection was started. A Base accelerometer was on the device at the extrathoracic portion, and other two were placed remotely at intrathoracic portion of the chest tube: Remote 1 placed midway between the tip and the insertion site and Remote 2 at the tip of the chest tube. Both tubes were connected to drainage canisters set at −20 cm H2O suction. The clamps on the chest tubes were released to allow drainage. At baseline (Time zero), a lung injury was induced by pulling the 0-polypropylene sutures, and 120 ml of withdrawn arterial blood was injected into each pleural space through the 8-Fr sheath preplaced through the minithoracotomy incision. Every 15 min thereafter, another 120 ml of blood was withdrawn from
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Figure 4: Results of initial in vitro testing. Control tube (left) is clogged and thrombus is visible in the tray. Both tubes with device assemblies attached (centre and right) were clot free.
Figure 3: Schematic illustration of an acute haemothorax model used to prove the efficacy of the new device concept versus Control (regular chest tube).
the arterial line and infused into each pleural cavity (a total of seven times) until 840 ml of blood was introduced into each pleural cavity. The mean arterial pressure was maintained above 60 mmHg. The amount of blood drainage from each thoracic cavity was recorded every 15 min for 2 h. Blood gas analysis, haematocrit levels, vibration amplitude, frequency and motor speed were observed throughout the experiment. The insertion sites (right and left) for the MAS device and Control tubes were alternated in each study. At the end of 2 h, the animals were euthanized. A median sternotomy was performed for careful examination of residual clots and blood inside the chest. The study data are reported as mean ± standard deviation (SD). Continuous variables were compared using Student’s paired t-test as appropriate in the Microsoft Excel statistical software program (Microsoft Office for Windows, Microsoft Corporation, Redmond, WA, USA).
RESULTS During in vitro testing, 10 min after the device had been turned on, the tube clamps were released and the movement of blood due to gravity was observed. In each of three trials, blood flowed freely from the Test tubes with no residual adhesions to the chesttube wall, but the Control tubes became obstructed by clot (Fig. 4). During in vivo testing, both Remote 1 and Remote 2 accelerometers ( placed from inside the chest at the mid-distance and at the tip of the chest tube) showed some attenuation of acceleration when compared with that registered by the Base accelerometer. However, vibration was successfully transmitted to the tip of the chest tube in all cases (Fig. 5). Total drainage volume was significantly (P = 0.027) higher when using the 32-Fr tubes coupled with the MAS device (369 ± 113 ml) versus the 32-Fr standard chest tube used as Control (209 ± 115 ml) (Fig. 6). The measured amount of residual blood and clotted
Figure 5: Plot shows the amplitude measured in a direction radial to spinning DC motor axis during the in vivo experimental testing. DC: direct current.
material in the chest cavity on the device side (401 ± 91 ml) was less than that observed on the Control side (501 ± 161 ml; P = 0.22) (Fig. 7). It is important to note that clots of a more solid character were observed with standard chest tubes. Clots were also found to be more fragile (easily broken up) in the chest on the device side. There were more visible luminal occlusions with standard tubes (Control) versus decreased clot formation in the tubes attached to the MAS device (Fig. 8). The MAS device maintained chest-tube patency even when some amount of clot was attached to the tube connectors or partially attached to the tube wall.
DISCUSSION This is the first report to demonstrate that vibration of chest tubes improved intrathoracic drainage. The MAS appears to prevent the initial deposition of blood and therefore clot formation. The use of chest tubes is routine after cardiothoracic surgery or chest trauma to avoid accumulation of blood, blood clot and air in the chest [9]; however, chest tubes often clog, and their occlusion
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can lead to life-threatening complications (e.g., haemothorax, acute tamponade and pericardial effusion) [2]. Adequate drainage is essential to avoid accumulation of blood in the pericardial and pleural spaces, and this requires patency of the chest-tube lumen until tube removal [10]. Despite improvements in intra- and postoperative patient management, chest-tube obstruction remains an important cause of complications and has adverse effects on patients’ recovery [6] and hospital outcomes. In the worst case of chest-tube clogging, the surgeon must bring the patient back into the operating theatre to remove clots around the heart to prevent pericardial tamponade and related complications. This scenario suggests that the detriment in outcomes associated with postoperative bleeding may be related to inefficient clearing of blood and clots retained in the chest due to chest-tube clogging [3]. The effects of makeshift strategies for establishing patency such as milking, tapping, fanfolding several layers of tubing and squeezing, hand-over-hand and/or hand-held or roller stripping
Figure 6: Blood drainage volume using 32-Fr chest tubes with motion-activated system device versus 32-Fr standard tubes as control.
manipulations can be effective only in selected cases; however, these techniques will carry the concern of bidirectional clot dislodgement [1, 11]. Therefore, new, more effective methods to prevent clot formation on both inner and outer surfaces of chest tubes and, most important, to maintain patency of drainage tubes are in high demand. These new methods will reduce clot accumulation within the chest and complications linked to that condition. Although the appearance of internal clot deposition inside the chest tubes was not similar among the studies, in selected cases the results were encouraging and need to be validated with more specific analysis of the clot formation per time and duration of bleeding. This will be helpful in obtaining a better understanding of the coagulation mechanisms under the effect of vibration motion. As the most desired we would consider the results similar to those shown in Figs. 7 and 8. Further improvements in design would be necessary to obtain more consistent data with the use of the device in a condition of excessive versus moderate amount of bleeding. To date, there is no reliable method of preventing chest-tube clogging. A negative suction is the only active component of the current chest-tube technology that assists the evacuation of blood, clots and fluids from the chest. A heparin coating that makes the
Figure 8: Although variable results with internal clot deposition inside the chest tubes were observed, in selected cases there was a notable difference between appearances of the device (A) and standard (B) chest tubes in post-extraction.
Figure 7: Intrathoracic appearance in one of the successful cases. Blood accumulation in the left pleural space with standard chest tube (A) versus minimal residual blood with the device (right side) (B).
J.H. Karimov et al. / Interactive CardioVascular and Thoracic Surgery
ACKNOWLEDGMENTS The authors thank the Medical Device Solutions group (in particular, Karl West) of Lerner Research Institute, Cleveland Clinic (Cleveland,
OH, USA), for providing valuable technical support throughout this project. Special thanks go to Nisha R. Vagadia for her valuable expertise and assistance.
Funding Jamshid H. Karimov, Kiyotaka Fukamachi and Raymond Dessoffy are inventors of the MAS technology. The project was funded by Cleveland Clinic Innovations (Cleveland Clinic, Cleveland, OH, USA). The authors had full control of the design of the study, methods used, outcome measurements and production of the written study report. Conflict of interest: The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the present manuscript.
REFERENCES [1] Teplitz L. Update: are milking and stripping chest tubes necessary? Focus Crit Care 1991;18:506–11. [2] Hunter S, Angelini GD. Phosphatidylcholine-coated chest tubes improve drainage after open heart operation. Ann Thorac Surg 1993;56:1339–42. [3] Karimov JH, Gillinov AM, Schenck L, Cook M, Kosty Sweeney D, Boyle EM et al. Incidence of chest tube clogging after cardiac surgery: A singlecentre prospective observational study. Eur J Cardiothorac Surg 2013;44: 1029–36. [4] Perrault LP, Pellerin M, Carrier M, Cartier R, Bouchard D, Demers P et al. The PleuraFlow active chest tube clearance system: initial clinical experience in adult cardiac surgery. Innovations (Phila) 2012;7:354–8. [5] Fujiki M, Shiose A, Fukamachi K. Recent advances and patents on chest drainage systems. Recent Patents Biomed Eng 2010;3:525–8. [6] Charnock Y, Evans D. Nursing management of chest drains: a systematic review. Aust Crit Care 2001;14:156–60. [7] Wallen M, Morrison A, Gillies D, O’Riordan E, Bridge C, Stoddart F. Mediastinal chest drain clearance for cardiac surgery. Cochrane Database Syst Rev 2004;4:CD003042. [8] Arakawa Y, Shiose A, Takaseya T, Fumoto H, Kim HI, Boyle EM et al. Superior chest drainage with an active tube clearance system: evaluation of a downsized chest tube. Ann Thorac Surg 2011;91:580–3. [9] Milas BL, Jobes DR, Gorman RC. Management of bleeding and coagulopathy after heart surgery. Semin Thorac Cardiovasc Surg 2000;12:326–36. [10] Smulders YM, Wiepking ME, Moulijn AC, Koolen JJ, van Wezel HB, Visser CA. How soon should drainage tubes be removed after cardiac operations? Ann Thorac Surg 1989;48:540–3. [11] Karimov JH, Gillinov AM, Boyle EM, Fukamachi K. Reply to Tavlasoglu et al. Eur J Cardiothorac Surg 2014;45:590.
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internal surface of the tube slippery (from a low coefficient of friction) is considered effective but has very limited time frames to maintain therapeutic efficacy [5]. The need for the prevention of tube clotting inside the chest tube and for effective maintenance of patency remains unmet [8]. If clots cannot stick to the chest-tube wall, the risk of tube occlusion can be significantly reduced. As cardiac surgery patients are becoming generally more complicated and bleeding represents a growing issue with the use of powerful antiplatelet agents, the problem of clogging may grow. Further efforts to understand how to prevent this are needed. Thus, it is important to recognize that clogged and dysfunctional chest tubes represent a real clinical issue [11]. It is important to mention that we aimed only to prove the device concept in this in vivo series; therefore, our studies were completed in 2 h. Larger animal models (adequate for prolonged exsanguination) and a chronic assessment of the drainage pattern will be necessary to explore sufficiently newer design optimizations. We would also consider a larger number of cases to obtain more consistent statistical significance in the next round of experiments. We acknowledge that our device is much larger than would be ultimately desirable, as it was constructed so for by rapid prototyping and to enable some hands-on versatility of the device during these development study series. Also, it is worth mentioning that the potential effects of vibration on thoracic structures are not completely characterized and the long-term safety and biocompatibility are yet to be explored in our forthcoming study series. Although we did not observe any significant heat generation, this factor should also be characterized and measured in our next experiments. The possible effect of vibration on wound healing, infection and pain perception other biological parameters were not defined as an end point of this study. This knowledge can be obtained only with long-term studies and would be evaluated in the future prior to clinical use approval. In conclusion, the use of the MAS system resulted in significantly higher drainage volume and maintained chest-tube patency throughout the experiments. These results suggest that a concept of motion application to the chest-tube wall may prevent postoperative clot deposition and subsequent build-up of critical occlusions inside chest tubes after cardiothoracic procedures.
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Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA Medical Device Solutions, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA Atrial Fibrillation Innovation Center, Global Cardiovascular Innovation Center, Cleveland, OH, USA Department of Thoracic and Cardiovascular Surgery, Kaufman Center for Heart Failure, Miller Family Heart and Vascular Institute, Cleveland Clinic, Cleveland, OH, USA
* Corresponding author. Department of Biomedical Engineering/ND20, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195. Tel: +1-216-4459344; fax: +1-216-4449198; e-mail: [email protected] (K. Fukamachi). Received 25 November 2013; received in revised form 31 January 2014; accepted 18 February 2014
Abstract OBJECTIVES: We designed a device that applies motion-activated energy (vibration) to prevent chest-tube clogging and maintain tube patency. We evaluated the efficacy of this device in vitro and in vivo. METHODS: The motion-activated system (MAS) device assembly comprises a direct current motor with an eccentric mass (3.2 g, centroid radius of 4.53 mm) affixed to its motor shaft. The device was tested in vitro using a model of an obstructed chest tube, with clots of bovine blood and human thrombin. The in vivo study (in nine healthy pigs, 46.0 ± 3.3 kg) involved a bilateral minithoracotomy and placement of 32-Fr chest tubes (with and without the device). Whole autologous blood (120 ml) was injected every 15 min into the right and left chest each over 120 min total. RESULTS: Chest-tube drainage over these 2 h using the MAS was significantly higher than that without the device (369 ± 113 ml vs 209 ± 115 ml; P = 0.027). CONCLUSIONS: Our results suggest that the motion-activation of the chest tubes may be an effective tool to maintain chest tubes patent. Further optimization of this technology is required to obtain more consistent prevention of clot deposition within or outside the chest tubes. Keywords: Haemothorax • Pleural space (drainage • management) • Pneumothorax • Surgery • Complications • Chest
INTRODUCTION It is common for patients undergoing cardiothoracic surgery to have clinical conditions that require the placement of chest tubes to drain blood, air or fluids. The functionality of chest-tube drainage must be properly maintained postoperatively [1]. However, occlusion of these chest tubes is not rare [2], and it is not uncommon for caregivers to think that the chest tube is completely patent, when in fact, the tube can be partially or completely occluded [3]. When blood encounters the chest-tube surface, despite the biocompatibility of the tube material itself, a coagulation cascade is initiated that can lead to partial or complete chest-tube clogging. Chest-tube clogging with blood and other fibrinous material can contribute to retained haemothorax, pleural effusion and haemodynamic compromise [4]. To date, there is no reliable method of preventing chest-tube clogging. Most chest tubes are made of polyvinyl chloride or silicone and have different diameters and shapes [5]. A negative suction remains the only actively reliable component to assist with the removal of blood, clots and fluids from the chest [6, 7].
To address the issue of chest-tube clogging, we have designed a device which applies motion-activated energy (vibration) primarily to prevent the adhesion of clots within the chest tube lumen (as well as to the outer surface) and thus maintain patency and proper function. We report the initial in vitro and in vivo evaluation outcomes with the motion-activated system (MAS).
MATERIALS AND METHODS The MAS device (Fig. 1) applies vibrational motion to cylindrical standard chest tubes to prevent their clogging and to maintain patency and proper functioning postoperatively. The SOLIDWORKS® solid modelling (three-dimensional (SD) computer-aided design) software (Dassault Systèmes, Vélizy-Villacoublay, France) for design and an Objet350 Connex 3-D printer (Stratasys, Minneapolis, MN, USA) were used for rapid prototyping. The prototype consisted of a modified direct current (DC) motor (UC-2803S-19160, Sinotech, Portland, OR) with an eccentric mass (3.2 g, centroid radius of 4.53 mm) affixed to the motor shaft (spinning axis parallel with chest tube centreline). The device is fabricated with two openings
© The Author 2014. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
NEW IDEAS
NEW IDEAS – THORACIC
Interactive CardioVascular and Thoracic Surgery 19 (2014) 1–5 doi:10.1093/icvts/ivu089 Advance Access publication 7 April 2014
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Figure 1: Diagram of the motion-activated system. (A) 3D images of the motion-activated chest-tube clogging prevention device. Drainage flow direction through the tube is indicated (red arrow). (B) Artistic rendering of the device in clinical use (each device unit is externally coupled with a chest tube). CT: chest tube; PC: power cable.
(parallel and perpendicular to DC axial orientation) (Fig. 2). Chesttube fixation and motion transmission were tested in both openings, but we did not try to obtain any evidence for what direction with respect to the device would be a better option versus another. For this reason, we have empirically chosen the parallel opening, which was used in all cases. Motion forces were varied by adjusting the current. The MAS device body is tightly coupled (with no tube compression) to the extrathoracic portion of chest tubes that are inserted into the chest in a standard fashion. The external end of the chest tube is connected to a collection canister with a vacuum suction attached (set at −20 cm H2O). When the device is turned on, motion is conveyed to the functional portion (segment with holes and openings) of the chest tube (towards the internal portion of the tube and the tip). Being an external unit, the device does not compromise the internal sterility of chest-tubes. In addition, the MAS is the only device that prevents clot attachment to the tube’s outer surface as well, which in turn improves drainage through the tube’s holes, which are kept open. This vibrational motion and its unique ‘swirling’ effect on the fluid inside the cylindrical tube were specifically designed to enhance the functional characteristics of the chest tubes currently used in cardiothoracic surgical practice. Preliminary in vitro tests were set up to assess clotting inhibition within standard chest drainage tubes versus those coupled with an initial device prototype. Standard 32-Fr polyvinyl chloride chest tubes (Covidien®, Mansfield, MA, USA) were clamped at one end and filled with whole calf blood preserved with the anticoagulant mix of citrate-phosphate-dextrose-adenine. Test and Control tubes were suspended vertically; blood was injected with human thrombin (Gelfoam Plus®, Baxter, Deerfield, IL, USA) to induce clotting. The Test tube was fitted with a MAS prototype and subjected to vibration; the Control tube was not vibrated. The in vivo study protocol was approved by Cleveland Clinic’s Institutional Animal Care and Use Committee, and all the animals received humane care in compliance with the ‘Guide for the Care and Use of Laboratory Animals’ (Institute of Laboratory Animal Resources, Commission on Life Sciences, National Research Council, National Academy Press, Washington, DC, USA, 2011) and institutional guidelines. In nine healthy pigs (Yorkshire mix, 46.0 ± 3.3 kg [M. Fanning Farms, Howe, IN, USA]), acute haemothorax was modelled per our
Figure 2: The SOLIDWORKS® solid modelling of the device design in four projections is shown. The opening for the chest tube insertion is indicated with an asterisk. CE: cable exit site; DCM: direct current motor; EM: eccentric mass units.
previously established method to evaluate chest-tube drainage [8] (Fig. 3). Anaesthesia was induced with an intramuscular injection of ketamine (20 mg/kg) and xylazine (5 mg/kg) and inhaled 5% isoflurane. With the animals in the supine position, two arterial lines were placed in the left and right carotid arteries for blood withdrawal. A bilateral minithoracotomy (sixth intercostal space) was constructed to insert blood infusion catheters and place 0– polypropylene sutures (Ethicon, Somerville, NJ, USA) at the edge (lower lobe) of both lungs to create an injury after chest closure. Two regular 32-Fr chest tubes (Control and MAS) were inserted (seventh intercostal space) bilaterally, and the thoracotomy was closed in layers. To ensure that motion was effectively conveyed towards the tip of the tube, the acceleration data in three axes (x, y and z) were measured with three accelerometers mounted on the device and chest tube itself before the blood injection was started. A Base accelerometer was on the device at the extrathoracic portion, and other two were placed remotely at intrathoracic portion of the chest tube: Remote 1 placed midway between the tip and the insertion site and Remote 2 at the tip of the chest tube. Both tubes were connected to drainage canisters set at −20 cm H2O suction. The clamps on the chest tubes were released to allow drainage. At baseline (Time zero), a lung injury was induced by pulling the 0-polypropylene sutures, and 120 ml of withdrawn arterial blood was injected into each pleural space through the 8-Fr sheath preplaced through the minithoracotomy incision. Every 15 min thereafter, another 120 ml of blood was withdrawn from
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Figure 4: Results of initial in vitro testing. Control tube (left) is clogged and thrombus is visible in the tray. Both tubes with device assemblies attached (centre and right) were clot free.
Figure 3: Schematic illustration of an acute haemothorax model used to prove the efficacy of the new device concept versus Control (regular chest tube).
the arterial line and infused into each pleural cavity (a total of seven times) until 840 ml of blood was introduced into each pleural cavity. The mean arterial pressure was maintained above 60 mmHg. The amount of blood drainage from each thoracic cavity was recorded every 15 min for 2 h. Blood gas analysis, haematocrit levels, vibration amplitude, frequency and motor speed were observed throughout the experiment. The insertion sites (right and left) for the MAS device and Control tubes were alternated in each study. At the end of 2 h, the animals were euthanized. A median sternotomy was performed for careful examination of residual clots and blood inside the chest. The study data are reported as mean ± standard deviation (SD). Continuous variables were compared using Student’s paired t-test as appropriate in the Microsoft Excel statistical software program (Microsoft Office for Windows, Microsoft Corporation, Redmond, WA, USA).
RESULTS During in vitro testing, 10 min after the device had been turned on, the tube clamps were released and the movement of blood due to gravity was observed. In each of three trials, blood flowed freely from the Test tubes with no residual adhesions to the chesttube wall, but the Control tubes became obstructed by clot (Fig. 4). During in vivo testing, both Remote 1 and Remote 2 accelerometers ( placed from inside the chest at the mid-distance and at the tip of the chest tube) showed some attenuation of acceleration when compared with that registered by the Base accelerometer. However, vibration was successfully transmitted to the tip of the chest tube in all cases (Fig. 5). Total drainage volume was significantly (P = 0.027) higher when using the 32-Fr tubes coupled with the MAS device (369 ± 113 ml) versus the 32-Fr standard chest tube used as Control (209 ± 115 ml) (Fig. 6). The measured amount of residual blood and clotted
Figure 5: Plot shows the amplitude measured in a direction radial to spinning DC motor axis during the in vivo experimental testing. DC: direct current.
material in the chest cavity on the device side (401 ± 91 ml) was less than that observed on the Control side (501 ± 161 ml; P = 0.22) (Fig. 7). It is important to note that clots of a more solid character were observed with standard chest tubes. Clots were also found to be more fragile (easily broken up) in the chest on the device side. There were more visible luminal occlusions with standard tubes (Control) versus decreased clot formation in the tubes attached to the MAS device (Fig. 8). The MAS device maintained chest-tube patency even when some amount of clot was attached to the tube connectors or partially attached to the tube wall.
DISCUSSION This is the first report to demonstrate that vibration of chest tubes improved intrathoracic drainage. The MAS appears to prevent the initial deposition of blood and therefore clot formation. The use of chest tubes is routine after cardiothoracic surgery or chest trauma to avoid accumulation of blood, blood clot and air in the chest [9]; however, chest tubes often clog, and their occlusion
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J.H. Karimov et al. / Interactive CardioVascular and Thoracic Surgery
can lead to life-threatening complications (e.g., haemothorax, acute tamponade and pericardial effusion) [2]. Adequate drainage is essential to avoid accumulation of blood in the pericardial and pleural spaces, and this requires patency of the chest-tube lumen until tube removal [10]. Despite improvements in intra- and postoperative patient management, chest-tube obstruction remains an important cause of complications and has adverse effects on patients’ recovery [6] and hospital outcomes. In the worst case of chest-tube clogging, the surgeon must bring the patient back into the operating theatre to remove clots around the heart to prevent pericardial tamponade and related complications. This scenario suggests that the detriment in outcomes associated with postoperative bleeding may be related to inefficient clearing of blood and clots retained in the chest due to chest-tube clogging [3]. The effects of makeshift strategies for establishing patency such as milking, tapping, fanfolding several layers of tubing and squeezing, hand-over-hand and/or hand-held or roller stripping
Figure 6: Blood drainage volume using 32-Fr chest tubes with motion-activated system device versus 32-Fr standard tubes as control.
manipulations can be effective only in selected cases; however, these techniques will carry the concern of bidirectional clot dislodgement [1, 11]. Therefore, new, more effective methods to prevent clot formation on both inner and outer surfaces of chest tubes and, most important, to maintain patency of drainage tubes are in high demand. These new methods will reduce clot accumulation within the chest and complications linked to that condition. Although the appearance of internal clot deposition inside the chest tubes was not similar among the studies, in selected cases the results were encouraging and need to be validated with more specific analysis of the clot formation per time and duration of bleeding. This will be helpful in obtaining a better understanding of the coagulation mechanisms under the effect of vibration motion. As the most desired we would consider the results similar to those shown in Figs. 7 and 8. Further improvements in design would be necessary to obtain more consistent data with the use of the device in a condition of excessive versus moderate amount of bleeding. To date, there is no reliable method of preventing chest-tube clogging. A negative suction is the only active component of the current chest-tube technology that assists the evacuation of blood, clots and fluids from the chest. A heparin coating that makes the
Figure 8: Although variable results with internal clot deposition inside the chest tubes were observed, in selected cases there was a notable difference between appearances of the device (A) and standard (B) chest tubes in post-extraction.
Figure 7: Intrathoracic appearance in one of the successful cases. Blood accumulation in the left pleural space with standard chest tube (A) versus minimal residual blood with the device (right side) (B).
J.H. Karimov et al. / Interactive CardioVascular and Thoracic Surgery
ACKNOWLEDGMENTS The authors thank the Medical Device Solutions group (in particular, Karl West) of Lerner Research Institute, Cleveland Clinic (Cleveland,
OH, USA), for providing valuable technical support throughout this project. Special thanks go to Nisha R. Vagadia for her valuable expertise and assistance.
Funding Jamshid H. Karimov, Kiyotaka Fukamachi and Raymond Dessoffy are inventors of the MAS technology. The project was funded by Cleveland Clinic Innovations (Cleveland Clinic, Cleveland, OH, USA). The authors had full control of the design of the study, methods used, outcome measurements and production of the written study report. Conflict of interest: The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the present manuscript.
REFERENCES [1] Teplitz L. Update: are milking and stripping chest tubes necessary? Focus Crit Care 1991;18:506–11. [2] Hunter S, Angelini GD. Phosphatidylcholine-coated chest tubes improve drainage after open heart operation. Ann Thorac Surg 1993;56:1339–42. [3] Karimov JH, Gillinov AM, Schenck L, Cook M, Kosty Sweeney D, Boyle EM et al. Incidence of chest tube clogging after cardiac surgery: A singlecentre prospective observational study. Eur J Cardiothorac Surg 2013;44: 1029–36. [4] Perrault LP, Pellerin M, Carrier M, Cartier R, Bouchard D, Demers P et al. The PleuraFlow active chest tube clearance system: initial clinical experience in adult cardiac surgery. Innovations (Phila) 2012;7:354–8. [5] Fujiki M, Shiose A, Fukamachi K. Recent advances and patents on chest drainage systems. Recent Patents Biomed Eng 2010;3:525–8. [6] Charnock Y, Evans D. Nursing management of chest drains: a systematic review. Aust Crit Care 2001;14:156–60. [7] Wallen M, Morrison A, Gillies D, O’Riordan E, Bridge C, Stoddart F. Mediastinal chest drain clearance for cardiac surgery. Cochrane Database Syst Rev 2004;4:CD003042. [8] Arakawa Y, Shiose A, Takaseya T, Fumoto H, Kim HI, Boyle EM et al. Superior chest drainage with an active tube clearance system: evaluation of a downsized chest tube. Ann Thorac Surg 2011;91:580–3. [9] Milas BL, Jobes DR, Gorman RC. Management of bleeding and coagulopathy after heart surgery. Semin Thorac Cardiovasc Surg 2000;12:326–36. [10] Smulders YM, Wiepking ME, Moulijn AC, Koolen JJ, van Wezel HB, Visser CA. How soon should drainage tubes be removed after cardiac operations? Ann Thorac Surg 1989;48:540–3. [11] Karimov JH, Gillinov AM, Boyle EM, Fukamachi K. Reply to Tavlasoglu et al. Eur J Cardiothorac Surg 2014;45:590.
NEW IDEAS
internal surface of the tube slippery (from a low coefficient of friction) is considered effective but has very limited time frames to maintain therapeutic efficacy [5]. The need for the prevention of tube clotting inside the chest tube and for effective maintenance of patency remains unmet [8]. If clots cannot stick to the chest-tube wall, the risk of tube occlusion can be significantly reduced. As cardiac surgery patients are becoming generally more complicated and bleeding represents a growing issue with the use of powerful antiplatelet agents, the problem of clogging may grow. Further efforts to understand how to prevent this are needed. Thus, it is important to recognize that clogged and dysfunctional chest tubes represent a real clinical issue [11]. It is important to mention that we aimed only to prove the device concept in this in vivo series; therefore, our studies were completed in 2 h. Larger animal models (adequate for prolonged exsanguination) and a chronic assessment of the drainage pattern will be necessary to explore sufficiently newer design optimizations. We would also consider a larger number of cases to obtain more consistent statistical significance in the next round of experiments. We acknowledge that our device is much larger than would be ultimately desirable, as it was constructed so for by rapid prototyping and to enable some hands-on versatility of the device during these development study series. Also, it is worth mentioning that the potential effects of vibration on thoracic structures are not completely characterized and the long-term safety and biocompatibility are yet to be explored in our forthcoming study series. Although we did not observe any significant heat generation, this factor should also be characterized and measured in our next experiments. The possible effect of vibration on wound healing, infection and pain perception other biological parameters were not defined as an end point of this study. This knowledge can be obtained only with long-term studies and would be evaluated in the future prior to clinical use approval. In conclusion, the use of the MAS system resulted in significantly higher drainage volume and maintained chest-tube patency throughout the experiments. These results suggest that a concept of motion application to the chest-tube wall may prevent postoperative clot deposition and subsequent build-up of critical occlusions inside chest tubes after cardiothoracic procedures.
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