since the first pneumonectomy performed by graham and singer in 1933 , the mortality of this procedure has decreased progressively . although parallel declines in the incidence of bronchopleural fistula ( bpf ) have been reported , this complication remains a major concern for the thoracic surgeon with associated high morbidity and mortality rates . one of the promising but clinically challenging areas of therapeutic advances involves the topical application of growth factors to enhance normal healing . a new strategy to better support and promote the wound - healing cascade is to prepare an autologous platelet concentrate suspended in plasma ( platelet - rich plasma ( prp ) ) for application to wound sites in a wide variety of surgeries . the therapeutic effects of prp are believed to result from the elevated levels of growth factors , for example , platelet - derived growth factor ( pdgf ) . using a porcine model , this study evaluated the feasibility of generating prp with gravitational platelet separation and investigated the granulation process after application on the bronchial stump . for our animal study we used a porcine model ( sus scrofus domesticus ) since the porcine lung is large enough to more accurately simulate the human lung . the porcine lung has become an excellent model for the normal human lung , for abnormalities in diseases and for therapeutics [ 510 ] . the pig lung has the dorsal , ventral , medial , and lateral bronchiole systems on either side . in addition , a tracheal bronchus arises from the right side of the trachea (  pig bronchus  ) . according to the bronchial ramification , the right lung consists of the cranial , middle , caudal , and accessory lobes , while the left lung consists of the bilobed middle and caudal lobes . the presence of a right tracheal bronchus suggested that left pneumonectomy would be more accurate as part of a human simulation experimental protocol . ten male pigs with an average weight of 26  kg were divided and randomized into two groups : the control group or non - prp group or group a ( pneumonectomy ) and the prp group or group b ( pneumonectomy and prp application ) . approval from the animal research ethics board of the prefecture of athens was obtained before commencement of this experimental protocol . all animals received humane care in compliance with the european convention on animal care and in accordance with the national research council 's criteria ( nih publication number . study was approved by the institutional ethics committee of the national and kapodistrian university of athens medical school . the animals were sacrificed following euthanasia guidelines adapted from the american veterinary medical association panel on euthanasia . prp was easy to produce with minimal effort and prepared as needed at the point of study . it was obtained by spinning down the animal 's own blood ( 23cc ) and collecting the buffy coat containing platelets and white blood cells . in a two - step process , whole blood from the animal first centrifuged to separate the plasma from packed red blood cells and then further centrifuged to separate prp from platelet - poor plasma . this concentrate was then activated with the addition of cacl , resulting in a gelatinous platelet gel . twenty - three milliliters of venous blood were withdrawn from the ear vein before administration of anesthesia . blood was collected in 5  ml tubes containing 3.8% trisodium citrate and then centrifuged at 1800  rpm for 8  min . the 1  ml fractions located immediately above the erythrocytes were collected from each tube and transferred to sterile tubes . fifty microliters of cacl at 10% ( w / v ) were added per 1  ml fraction of platelet - enriched plasma , and the tubes were put to heat until cylindrical clots were obtained in a few minutes . lesser concentrations can not be relied on to enhance wound healing , and greater concentrations have not been shown to increase wound healing [ 14 , 15 ] . induction to anesthesia was managed by administration of pentothal 8  mg / kg , pancuronium 0.15  mg / kg , and fentanyl 17.5  g / kg . under general anesthesia the animals were placed in the supine position , intubated with a double - lumen endotracheal tube , and mechanically ventilated . maintenance to anesthesia was managed by administering of pentothal at 3.5  mg / kg / h , pancuronium at 0.07  mg / kg every 20 minutes , and fentanyl at 15  g / kg / hr iv . a standard posterolateral thoracotomy via muscle - sparing incision was performed and the chest entered through the fifth intercostal space . a vascular clamp was placed on the proximal pulmonary artery and the artery was divided and closed with a running silk suture . the inferior pulmonary vein was approached from the anterior aspect of the hilum , clamped , and divided . the bronchus was retracted laterally , being pulled upward toward the incision to facilitate the dissection and the placement of the endo - atg45 stapler on the proximal bronchus . proved that granulation tissue formation at the bronchial stump is reduced after stapler closure comparison to suture closure . in order to investigate the role of prp during the healing process of the bronchial stump after the bronchial suture line had been dried with a sponge , it was covered with a cylindrical clot of prp ( figure 1 ) , applied vertically to the bronchial stump . they were all sacrificed 4 weeks after the operation ( table 1 ) . during necropsy , the bronchial stump , the operative field , and the entire thoracic cavities then , the trachea with the right lung were harvested , routinely cut , and fixed in 10% buffered formalin solution . transverse sections of the bronchial stumps vertical to the line of the closure were made . two sections per stump were taken . before section preparation staples were carefully removed in all samples . these sections were stained with eosin and haematoxylin for morphological examinations . using the optical microscope , the presence of granulation tissue was assessed in each sample and was quantified as the percentage of the total tissue area . histological assessment of the slides was performed by two independent , blinded to the treatment modalities , pathologists . data are shown as percentages of the presence of granulation tissue per transverse section taken . the percentages in each group of animals were compared using mann - whitney u test . all results with a two - sided p level  0.05 were considered statistically significant . the granulation tissue in all cases consisted of chronic inflammatory cells , including foreign body giant cells forming granulomas ( figure 3 ) . the bronchial cartilages at the stump were satisfactory aligned and the luminal side of the bronchial stump was lined by bronchial epithelium in all groups . the percentage of granulation tissue formed at the stumps was significantly higher in the prp group of animals ( figure 4 ) . this observation was confirmed when statistical analysis using mann - whitney u test was performed ( p = 0.0268 ) . a considerable number of retrospective studies have been performed on bronchial closure techniques in human medicine , and a few experimental studies have been carried out on the basis of these retrospective studies . however , bronchial stump closure techniques , their histological healing patterns , and possible bronchial stump complications after pneumonectomy need further experimental and clinical investigation . a new strategy to promote the healing cascade is to prepare a substance for application to the bronchial stump . the ideal substance in pulmonary surgery is one that possesses several properties such as the ability to adhere to the tissue . it should have a good biocompatibility , without provoking any tissular lesion or affecting the healing process . it should be biodegradable , with no risk of infectious transmission , and should not stimulate adhesion formation , which makes any reoperation difficult . most of these adhesive substances are only mechanical occluders , and they do not have any positive biological effects . they are also applied usually through postoperative procedures like , for example , the bronchoscopic occlusion of a fistula with a collagen screw plug . on the other hand , autologous prp is a safe , feasible , and reliable new healing promoter with important therapeutic effects that is used intraoperatively [ 1315 ] . it is easily produced with minimal basic equipment and may be useful in certain types of acute and chronic wounds , although the timing and optimum number of applications requires further study . prp functions as a tissue sealant and drug delivery system , with the platelets initiating wound repair by releasing locally acting growth factors via -granules degranulation . the secretory proteins contained in the -granules of platelets include platelet - derived growth factor ( pdgf - aa , bb , and ab isomers ) and many others [ 2024 ] , which aid healing by attracting undifferentiated cells in the newly formed matrix and triggering cell division . prp may suppress cytokine release and limit inflammation , interacting with macrophages to improve tissue healing and regeneration , promote new capillary growth , and accelerate epithelialization in chronic wounds . when platelets are activated , they release their growth factors almost immediately and continue to synthesize additional growth factors for several days , after which they lose vitality . the cytokine response generated by prp fulfills the requirements for appropriate healing : it promotes immediate onset but does not persist to cause chronic inflammation . the main findings of this study are as follows : prp application is a feasible and reliable technique not associated with any negative local or systemic effect . in thoracic surgery and especially lung resection operations , the application of prp triggers the granulation process and promotes healing through an earlier initiation of the inflammatory response .
objectives . recent advances in perioperative management , antibiotics , and surgical materials , including mechanical staplers , have decreased the operative risk of pulmonary resection . 
 however , bronchopleural fistula can still occur in some instances , the occurrence often being lethal . 
 this study investigated whether platelet - rich plasma ( prp ) promotes granulation of the bronchial stump after pneumonectomy . 
 methods . 
 ten pigs were randomized into two groups : ( a ) control or non - prp group ( pneumonectomy ) and ( b ) prp group ( pneumonectomy and prp application ) . 
 prp was obtained by spinning down the animal 's own blood and collecting the buffy coat containing platelets and white blood cells . 
 results . increased platelet concentration triggered the healing process . 
 the percentage of granulation tissue formed at the stumps was significantly higher in the prp group of animals . 
 this observation was confirmed when statistical analysis using mann - whitney u test was performed ( p = 0.0268 ) . 
 conclusions . 
 prp is easily produced with minimal basic equipment and is useful in accelerating granulation of the bronchial stump , although the timing and optimum number of applications in humans require further study . 
 autologous prp is a safe , feasible , and reliable new healing promoter with potential therapeutic effects .