Determination of subcarinal angle of trachea using computed tomography

Background: Change in tracheal bifurcation angle (subcarinal angle) is an indirect marker of various cardiac, pulmonary and mediastinal pathologies. Helical computed tomography (CT) allows acquisition of volumetric set of data of the chest and can be used for accurate measurements of subcarinal angle using reconstructed images on a workstation using minimum intensity projection (MinIP).The objective of this study was to estimate normal subcarinal angle (SCA) of trachea by computed tomography and to assess its relationship with gender.Methods: This was an observational study comprising a study cohort of 552 patients comprising of 312 males and 240 females who were subjected to CT chest for various indications in our department. Patients with no underlying cardiac, mediastinal or pulmonary disease were included in the study. Spiral CT scan of chest was performed on 64-slice seimens CT SOMATOM and images were reconstructed with thickness of 1.5mm and the images were viewed in coronal reformatted minimum intensity projection (MinIP) for determination of subcarinal angle using the angle measuring tool provided in the workstationResults: The mean subcarinal angle (SCA) in males was (67.60±14.55). The mean subcarinal angle (SCA) in females was (78.90±11.04). Females had a higher mean SCA compared to males with a statistically significant difference (p-value <0.05).Conclusions: The mean SCA in females was higher compared to males with a statistically significant difference between the two. This study holds practical relevance with regard to the performance of invasive trachea-bronchial procedures like bronchoscopy and tracheal/bronchial intubation.

Implantation of inverted Y-type metal airway stent with modified guide wire insertion technique under local anesthesia for malignant carina stenosis: initial experience in 10 patients / 介入放射学杂志

Objective To assess the technical feasibility and effectiveness of X-ray-guided implantation of inverted Y-type metal airway stent under local anesthesia by using a modified technique of exchanging guide wire in order to shorten operation time.Methods The clinical data of a total of 16 patients,who received inverted Y-type metal airway stent implantation under local anesthesia,were retrospectively analyzed.Routine gradual guide wire exchange method with a harder one was used in 6 patients (routine group),while in 10 patients (modification group) a modified technique of exchanging guide wire,i.e.inserting two hard wires at one time,was employed.Technical success rate and operation time were used as the main observation indexes.Results Under local anesthesia,the implantation of inverted Y-type metal airway stent was successfully accomplished in all 16 patients.The mean operation time of the routine group and the modification group was 15.6 minutes and 11.1 minutes respectively,the difference between the two groups was statistically significant (P＜0.05).Conclusion For the performance of implantation of inverted Ytype metal airway stent under local anesthesia to treat malignant carina stenosis,the use of modified technique of guide wire insertion,i.e.inserting two hard wires at one time,can effectively shorten the operation time.

Y-shaped silicone airway stent placement for complex airway diseases / 中国内镜杂志

Objective To investigate the feasibility and therapeutic efficacy of inverted Y-shaped silicone airway stent for complex airway diseases (stenosis or fistula). Methods According to the particular anatomic structure and the pathological changes of complex airway diseases, the inverted Y-shaped silicone airway stents were designed. 7 stents were implanted in 7 cases of airway complex diseases with the guidance of interventional rigid bronchoscope under general anesthesia. Results The Y-shaped silicone stents were placed successfully followed with the result of immediate relieves of the symptoms. Dyspnea grade was improved significantly from Ⅲ~Ⅳ to 0 ~Ⅱ , and oxygen saturation elevated from ( 84.1 ± 4.5 ) % in inspiring high concentration oxygen to ( 94.1 ± 2.9 ) % in breathing ambient air (P = 0.000). The main complications were cough, foreign body sensation, chest pain, granulation, sputum retention, et al. Conclusion Placement of Y-shaped silicone airway stent is a feasible and safe treatment for complex airway disease, the recent curative effect is reliable, it is worth further promoting.

Otologic Active Middle Ear Implants / 대한이비인후과학회지

Implantable devices for aural rehabilitation are widely developed worldwide. In the manuscript, we review the implantable middle ear hearing devices currently in use, such as the Vibrant Soundbridge system (Med-El Corporation), the MAXUM system (Ototronix LLC), the fourth-generation of Carina prosthesis (Otologics LLC), and the Esteem device. Implantable hearing aids will unquestionably be the major drivers of advancement in otologic practice in early future, improving the quality of life of an increasingly aged population, which will consequently require increased levels of hearing support.

Clinical analysis of bleeding during transbronchial needle aspiration / 第二军医大学学报

Objective To retrospectively analyze the incidence of bleeding during transbronchial needle aspiration (TBNA) procedures, so as to provide evidence for prevention and treatment of the condition. Methods TBNA procedures were performed in 178 patients with enlarged mediastinal and/or hilar lymph nodes, who were treated in the People's Hospital of Linyi. A total of 248 lymph node sites were punctured, including 100 for the groups of pretracheal and post-superior vena cava lymph nodes (4R), 10 for the groups of left paratracheal (aorta-pulmonary artery windows) lymph nodes (4L), 13 for the groups of pre-carinal lymph nodes (7),90 for the groups of sub-carinal lymph nodes (7), 12 for the groups of sub-subcarinal lymph nodes (7), 12 for the groups of right lung hilar lymph nodes (11R), and 11 for the groups of left lung hilar lymph nodes (11L).TBNA procedures were performed according to WANG's TBNA positioning and punctured method. The sites and incidence rates of bleeding sites during the procedures were analyzed. Results The highest incidence rate of bleeding (20%) was found during TBNA procedures in the sub-carinal lymph node groups (7), and the lowest incidence rate was found (2%) in the pretracheal and post-superior vena cava lymph node groups (4R).The incidence rates of bleeding were significantly different between different puncture sites as demonstrated by chi-square test (χ2=17.035,P=0.009). Conclusion Pretracheal and post-superior vena cava lymph nodes (4R) and sub-carinal lymph nodes (7) are the most common TBNA puncture position in the airway. TBNA procedure at sub-carinal lymph nodes (7) has the highest risk of bleeding. The massive bleeding during TBNA procedures can be avoided by prior enhanced CT and/or endobronchial ultrasound (EBUS)-TBNA of the lung.

Dispositivo auditivo totalmente implantable Carina®: revisión sistemática / Fully implantable hearing device Carina®: systematic review / Fully implantable hearing device Carina®: systematic review

Objetivos: Revisar/resumir indicaciones, resultados audiológicos y de calidad de vida del dispositivo totalmente implantable Carina®. Diseño: Revisión sistemática. Métodos: Se realizó una búsqueda sistemática de la literatura entre junio/2011 y enero/2012 en bases de datos: Medline, OVID, Embase, Pro Quest, Biblioteca Cochrane. También se revisó literatura gris (Sigle) en búsqueda de información no publicada. No hubo restricción de lenguaje o límite temporal, y se incluyeron estudios en humanos con mediciones antes/después de la intervención. Se excluyeron reportes de un caso y estudios con pacientes prelinguales. Se evaluó heterogeneidad estadística (prueba Der Simonian-Laird), y la ganancia funcional combinada (GFC) se estimó con un modelo de efectos aleatorios. Se evaluó sesgo de publicación (gráfica de embudo y prueba Eggs). Resultados: Se identificaron 155 publicaciones, 43 enfocadas en el tema de investigación; ocho cumplieron criterios de inclusión/exclusión, que reportan 110 pacientes. La GFC fue 27,24 dB [IC 95% = 21,66-32,83 dB], I2 = 85%. El reconocimiento de palabras (65 dB-SPL) se incrementó con Carina® entre 35 y 70%, y hubo mejoría en calidad de vida (escala Aphab). La complicación más frecuente fue extrusión (2,7%). Se encontró sesgo de publicación (Eggs = 0,0011). Conclusiones: Se encontró heterogeneidad clínica y bajo nivel de evidencia publicada. La GFC fue considerable con el implante…

Objectives: To review and summarize indications, audiological and quality of life (QOL) outcomes of Carina® fully implantable device. Design: Systematic review. Methods: We conducted a systematic search of literature between June/2011 and January/2012 in: Medline, OVID, Embase, ProQuest, Cochrane Library. The unpublished information gray literature databases (Sigle) were also reviewed. No language or time limit restriction. Study eligibility criteria were: human studies with measures before and after the intervention. One patient case report and prelingual patients studies were excluded. Statistical heterogeneity was assessed (Der Simonian- Laird test), random effects model as a method of synthesis of functional gain was used. Publication bias was assessed (funnel plot and Eggs test). Results: 155 publications were identified, 43 of them were focused on the research topic, eight met the inclusion/exclusion criteria and report 110 patients. The pooled functional gain was 27.24 dB [95% CI = 21.66-32.83 dB], I2 = 85%. The word recognition (65 dB-SPL) was increased between 35%-70% with Carina®. A QOL improvement was observed (APHAB scale). The most frequent complication was device extrusion (3.6%). Publication bias was found (Eggs = 0.0011). Conclusions: Clinical heterogeneity and low evidence level were found in the published literature. The pooled functional gain was considerable with the implant. …

An Endobronchial Inflammatory Myofibroblastic Tumor Treated by Modified Left One-stoma-type Carinoplasty

Endobronchial inflammatory myofibroblastic tumor is a rare primary lung disease. A 39-year-old woman with dyspnea and a productive cough underwent complete surgical resection of a small-sized inflammatory myofibroblastic tumor that invaded the left main bronchus and the carina with lung-saving modified left one-stoma-type carinoplasty. We report this case with a review of literature.

Comparison of two topographical airway length measurements in adults / 대한마취과학회지

BACKGROUND: A correct estimate of the tracheal tube insertion depth can prevent complications, including endobronchial intubation and vocal cord trauma. We evaluated a new topographical method for endotracheal tube positioning relative to the carina, using a well-known prior topographical method for comparison. METHODS: One hundred adult (male 50, female 50) patients were studied. The comparison topographic length (in cm) was measured by adding the distance between the right mouth corner and the right mandibular angle to the distance between the right mandibular angle and the center of the sternal manubrium. The new endotracheal tube insertion depth (in cm) was determined by adding the distance between the right mouth corner and the vocal cords, measured with the endotracheal tube itself, to the distance between the thyroid prominence and the manubriosternal joint, and then subtracting 4 cm. After intubation, the endotracheal tube was positioned properly at the right mouth corner and the endotracheal tube tip was evaluated using a fiberoptic bronchoscope at the carina. RESULTS: The distances from the tip of the endotracheal tube to the carina were not significantly different between the methods in the same gender. However, our method allowed endotracheal tube tip placement between 3 cm and 5 cm, above the carina more frequently than the prior method in males. CONCLUSIONS: The new topographical method can be used as a guide to positioning the endotracheal tubes.

The placement of Y-shaped titanium-nickel memory alloy stent in the carina: a fundamental study in experimental canines / 介入放射学杂志

Objective To investigate the pathological changes of local airway tissue after inserting Y-shaped titanium-nickel memory alloy stent in carina, and to evaluate CT three-dimensional reconstruction technique in postoperative and follow-up observation. Methods Twelve healthy adult canines were enrolled in this study. Based on the information of the carina obtained from CT three-dimensional reconstruction images, the preparation of Y-shape netlike stent was made by knitting method with single Ni-Ti memory alloy wire. The stent was then inserted in canine's carina with the help of a releasing system. After the operation fiberbronchoscopy and CT three-dimensional reconstruction were performed. The animals were sacrificed 12 weeks after the procedure and the bronchus of the stenting segment was removed and sent for histopathologic examination. Results Technical success was achieved in all canines with the stent fight in the carina. The airway remained unobstructed 12 weeks after the procedure. Histopathologic examination revealed that the stent became partial epithelialization. Conclusion The Y-shaped titanium-nickel memory alloy stent has good histecompatibility and physicochemical stability and no re-stenosis of the airway develops in the follow-up period of three months. The stent-releasing technique is easy and simple. As a non-invasive and convenient exam, CT three-dimensional reconstruction technique is of great value in postoperative follow-up observation.

Carinal Resection and Reconstruction for Carinal Tumor / 대한흉부외과학회지

Carinal resection is technically demanding and the surgical risk is relatively high. When tumor is confined around the carina, then lung parenchymal sparing surgery is technically feasible in selected cases. We performed carinal resection and reconstruction without pulmonary resection for a patient suffering with squamous cell carcinoma that involved the carina and this patient had undergone right upper lobectomy 19 months previously due to lung cancer.

The Carina as a Landmark for Evaluation of Adequate Central Catheter Tip Position with Computerized Tomography / 대한구급학회지

BACKGROUND: The aim of this study was to determine whether the carina can be used as a landmark for evaluation of adequate central catheter tip position, and to examine the relationship between easily measurable body size and variable anatomical parameter. METHODS: The SVC dimensions and relationship to radiographic landmarks were retrospectively determined from computerized tomography (CT) scans of 200 patients. The CT findings were assessed in terms of SVC length (SVCL), the distance between the carina and the right atrium inlet (CAL), and the sternal length (STL). Pearson's correlation and a regression test for height versus SVCL, STL versus SVCL and CAL were performed. RESULTS: The median length of the SVC was 4.2 cm (range; 1.6 to 7.2 cm) and the distance between the carina and the right atrium inlet was 2.4 cm (range; 0.8 to 5.6 cm). With the regression test, height was correlated with SVCL (r(2)=0.09), and STL was correlated with both SVCL (r(2)=0.12) and STL (r(2)=0.04). CONCLUSIONS: The carina was located always above the right atrium inlet. The carina was a reliable, simple anatomical landmark for the determination of correct placement with computerized tomography.

Slide tracheoplasty with pericardial patch augmentation for reconstruction of severe congenital tracheal stenosis involving carina : A case report.

Objective: Slide tracheoplasty seems to be the most efficient surgical procedure for correcting long-segment funnel-shaped congenital tracheal stenosis. However, in cases of extremely long-segment or those involve carina, slide tracheoplasty when operated alone has certain degree of limitations which often need additional operative procedure. The authors report a technique of slide tracheoplasty in combination with pericardial patch augmentation in a child with congenital tracheal stenosis involving the carina. Methods: A 3-month-old girl, previously diagnosed with Tetralogy of Fallot and congenital tracheal stenosis, presented with severe cyanosis and serious major airway obstruction after a few days of upper respiratory tract infection (URI). Because of the failure to maintain her ventilation with a high positive pressure ventilator, an emergency slide tracheoplasty with a modified right Blalock’s Taussig shunt was performed under a cardiopulmonary bypass. The intraoperative finding revealed a complete tracheal ring stenosis involving the lower half of the trachea and carina. It was transected at the middle and a vertical incision was made at the posterior wall of the upper trachea and anterior wall of the lower and extended into orifices of the main bronchus. The upper and lower tracheal flaps were slid together and sutured with interrupted Proline 5-0. Consequently, she still had significant obstruction of the main bronchi postoperatively and needed a re-operation two days later. Under cardiopulmonary bypass support, the lower anastomotic sutures were removed and an additional bronchial incision was made into the main bronchus. The anterior upper tracheal flap was separated into two, and each equal flap was pulled down and sutured to the main bronchus. Then an autologous pericardial patch was used to cover all the airway defects. Intraoperative fiberoptic bronchoscopy demonstrated adequate tracheo-bronchial lumen. Results: The child had postoperative hyperactive airway reaction and needed prolonged ventilator support and tracheostomy for tracheal toileting. Repeated postoperative bronchoscopy found moderated granulation tissue which was easily removed by catheter suction. Unfortunately, the patient expired six months after the surgery due to uncontrolled sepsis. However, a bronchoscopic finding before the patient’s death revealed adequate major airway patency. Conclusion: Combined slide tracheoplasty with pericardial patch augmentation made reconstruction of the complex congenital tracheal stenosis involving carina or tracheal bronchus possible and minimized the result of unflavoric excessive granulation tissue forming caused by pericardial tracheoplasty alone.

The Effect of Lithotomy-Trendelenburg Position and Carbon Dioxide Insufflation on the Distance from the Upper Incisor to the Carina / 대한마취과학회지

BACKGROUND: The carbon dioxide (CO2) insufflation and lithotomy-Trendelenburg position are required in the laparoscopic gynecologic surgery. However, they can change the distance from the upper incisor to the carina. This may increase the risk of endobronchial intubation. METHODS: Nineteen patients, aged 29-50 yr, who were undergoing laparoscopic surgery were enrolled. We measured the distance from the upper incisor to the carina of them with fiberoptic bronchoscope. Measurements were taken in the each point of lithotomy position, lithotomy-Trendelenburg position, and lithotomy-Trendelenburg position after CO2 insufflation. RESULTS: The average distance from the upper incisor to the carina was 23.1 +/- 1.4 cm in the lithotomy position (0 degree) and was significantly decreased to 22.6 +/- 1.4 cm in the lithotomy-Trendelenburg position (15 degrees) (P<0.05). After CO2 insufflation into the abdominal cavity, the mean distance in the lithotomy-Trendelenburg position (15 degrees) was significantly decreased to 22.1 +/- 1.4 cm (P<0.05). CONCLUSIONS: The lithotomy-Trendelenburg position and CO2 insufflation decrease the distance from the upper incisor to the carina.

Study of Distance from the Upper Incisor to the Carina in Children Using X-ray / 대한마취과학회지

BACKGROUND: There was a difference between the past and the present in distance from the upper incisor to the carina in children. This study was performed to evaluate the distance from the upper incisor to the carina and correlation of it with age, the weight and height in korean children from 2 to 8 years old. METHODS: Two hundred twenty two children from 2 to 8 years old scheduled for receiving tonsillectomy or adenoidectomy were evaluated for the study by age groups (every 6 months from 2 to 8 years old). The X-ray was used for evaluation of distance from the incisor to the carina. The distance from the upper incisor to C7 was calculated on neck lateral view and distance from C7 to the carina was calculated on chest PA. Both distance were added and served as the distance from upper incisor to the carina. RESULTS: The coefficient of determination of the distance from the upper incisor to the carina was highest according to height. The regression equation of the distance from the upper incisor to the carina using height was Y (cm) = 0.15 X (cm) and R2 = 0.70 (Y: the upper incisor to the carina, X: the height). CONCLUSIONS: We found that the distance from the upper incisor to the carina in children correlated with both the weight and height in children and the height was the highest correlation with distance.

Femoro-femoral Cardiopulmonary Bypass during Tracheal Reconstruction Surgery: A case report / 대한마취과학회지

A 45 year-old-women with tracheal stenosis due to an endotracheal tumor was scheduled for tracheal reconstruction surgery. The stenotic lesion was located 1 cm above the carina, and was length of 4 cm and had a narrowest internal diameter of 0.4 cm. The length of such a stenotic segment and its narrowest internal diameter may pose lung ventilation problems before or during tumor resection, which may preclude a successful outcome. Thus, during tracheal reconstruction surgery a femoro-femoral partial cardiopulmonary bypass, self respiration, and pulmonary artery ligation were used. These measures improved oxygenation and cardiovascular stability, and tracheal reconstruction was successfully performed without complication.

Survey of Central Venous Catheter Depth Using the Carina as a Radiologic Landmark in ICU Patients / 대한마취과학회지

BACKGROUND: There is no unique guideline as to how to determine the depth of a central venous catheter (CVC). In this study, we inspected the current practice of CVC placement and evaluated insertion depth using the carina as a radiologic landmark in intensive care unit (ICU) patients. METHODS: In 138 ICU patients with a CVC in the right subclavian (SCV group) or internal jugular vein (IJV group), a chest X ray was taken, and the radiographic vertical distance between the catheter tip and the carina level (D-CC) was measured in Picture Archiving and Communication System (PACS) view. The distance between the skin puncture site and the carina level (D-SC) was calculated by adding/subtracting D-CC to/from the actual CVC insertion length. In addition, we surveyed physicians using a questionnaire about the methods they used to determine CVC depth. RESULTS: Mean D-SC was 13.80 +/- 1.69 cm in the SCV group, 14.42 +/- 1.34 cm in the IJV group, but no correlation was found with any measured physical dimension. In males, D-SC was greater, but this difference was not statistically significant. Physicians determined required insertion depths using many different methods (e.g., height, sex......). CONCLUSIONS: Patient height, weight, body mass index (BMI), and sex were not found to be reliable for predicting a safe CVC length. We recommend that after CVC insertion, a chest X ray should be taken and the catheter tip repositioned if necessary to reduce catheter related fatal complications (e.g., cardiac tamponade).

Extended operation for non-small lung cancer invading left atrium and great vessels and trachea carina / 中国癌症杂志

Purpose:To evaluate the clinical effects and indications of surgical treatment of non small lung cancer invading the left atrium and great vessels and trachea carina. Methods:From August 1998 to Auguest 2003, we performed operations on patients with non-small lung cancer invading the left atrium in 3 cases, invading the descending aorta in 1 case, invading trachea carina in 3 cases; all the patients have been examined to exclude distant metastasis, including nuclear bone scan to exclude bone metastasis; there were 2 cases of left pneumonectomy and one of right pneumonectomy invading the left atrium, there were 3 cases of right sleeve pneumonectomy invading the trachea carina. For the cases invading the descending aorta, we performed the operation with atrium-aorta bypass, Pathology examination: all of the cases were squamous lung cancer, staging of T 4N 0M 0 for 6 cases,T 4N 2M o for 1 case. Results:No complication, follow up: 6 cases survived more than 1 year,1 case survived more than 9 months;4 cases were alive for more than 3 years, 1 case invading the atrium died in 30 months because of brain metastasis,1 case invading the carina died in 15 months because of pulmonary infection. Conclusions:For localized advanced non-small lung cancer invading the aorta and invading the carina and the atrium, if we selected the patient correctly and with a good surgical technique with complete radical resection of the tumor ,we can acquire good results.

Study of Lengths from the Upper Incisor to Left and Right Mainstem Bronchial Carina in Korean Adults Using a Fibroptic Bronchoscope / 대한마취과학회지

BACKGROUND: Accurate knowledge of mainstem bronchial lengths are required to prevent malpositioning of double lumen endobronchial tubes (DLT). Therefore we evaluated the length of the mainstem bronchus in Korean adults who had no abnormalities in both mainstem bronchus. METHODS: Two-hundred Thirty-seven patients were composed of One-hundred one males and One- hundred Thirty-six females who underwent elective surgery. After an endotracheal tube was placed, we measured the length from the upper incisor to the tracheal carina, the right mainstem bronchial carina, and the left mainstem bronchial carina using a fiberoptic bronchoscope. RESULTS: The lengths from the upper incisor to the carina of a male and female were 26.8 +/- 1.8 cm and 23.6 +/- 1.9 cm respectively, and the correlations between their length and height are significant for male and female (r = 0.32, P < 0.01 and r = 0.56, p < 0.0001). The lengths from the upper incisor to the right mainstem bronchial carina of male and female were 29.0 2.0 cm and 25.3 2.2 cm respectively, and the correlations between their length and height are significant for male and female (r = 0.39, P < 0.0001 and r = 0.59, P < 0.0001). The lengths from the upper incisor to the left mainstem bronchial carina of male and female were 32.0 2.1 cm and 28.5 2.1 cm respectively, and the correlations between their length and height are significant for male and female (r = 0.45, P < 0.0001 and r = 0.60, P < 0.0001). CONCLUSIONS: We found that as the height of patients increased, the length from the upper incisor to the carina, the right mainstem bronchial carina, and the left mainstem bronchial carina increased. Nevertheless,it should be understood that the length of DLT insertion at any given height is still normally distributed, and correct DLT positioning should always be confirmed fiberoptically after the initial placement.

Assessment of the Endotracheal Tube Size and Distance from Incisor to the Carina with Chest X - Ray / 대한마취과학회지

Post-intubation croup and tidal volme leak during ventilator support may occur when unsuitable size of endotracheal tube is used. Malposition of endotracheal tubes(ETT) are particularly common in pediatric ICU patients, and may lead to serious complications such as inadvertent endobronchial intubation and accidental extubation. Due to the inaccuracy of physical examination for ETT placement and although there is additional time consumption and expense, the chest X-ray is still considered the gold standard for ETT position evaluation. We assessed the predetermined endotracheal tube size and the distance from the incisor to the carina according to the patient's age, weight and height. The chest X-ray was used for evaluation of these patients who were admitted to the intensive care unit of Severance Hospital Yonsei Medical Center from March to August, 1990. We divided the 430 intubated patients into two groups. Group 1 included 163 patents who were intubated by a endotracheal tube without a cuff. Group 2 included 237 patients who were intubated by a endotracheal tube with a cuff. The conclusion from our results were as follows: 1) The coefficient of determination of the endotracheal tube size, R(2), was highest according to weight, 0.40 and 0.50 in Group 1 and 2. The regression equation of endotracheal tube size using weight was Y=0.11X+3.42 and Y=0.04X+5.46 in Group 1 and Group 2. 2) The coefficient of determination of the distance from the incisor to the carina was highest according to weight 0.57 and 0.33 in Group I and 2. The regression equation of the distance from the incisor to the carina using weight was Y=0.47+10.74 and Y=0.11X+20.17.