a 40-year - old woman , 169 cm , 57 kg , underwent laparoscopic right adrenalectomy due to an adrenal pheochromocytoma . a 7.5 fr 3-lumen catheter was inserted under ultrasonographic guidance ( linear probe : ust-5546 , 5 - 10 mhz , machine : prosound ssd-4400 , aloka medical , co. , ltd . , tokyo , japan ) into the right internal jugular vein , and lung sliding was confirmed in both thoraces . next , the patient was placed into the left lateral decubitus position . before incision , etco2 , pmax , and peripheral oxygen saturation ( spo2 ) pneumoperitoneum was established using co2 , intraabdominal pressure was maintained < 15 mmhg , and pmax was 23 cmh2o at the time . thirty minutes after inducing pneumoperitoneum , the etco2 and pmax levels gradually increased to 43 mmhg and 30 cmh2o , respectively . however , the right side of the chest demonstrated no sounds . immediately , the fraction of inspired oxygen ( fio2 ) increased from 0.5 to 0.8 , and the endotracheal tube was withdrawn back to 2 cm in order to rule out endobronchial intubation . because the depth of the endotracheal tube was 18 cm at the incisor teeth and confirmed the depth of endotracheal tube by cuff palpation at the sternal notch , we supposed that it was enough to rule out one - lung intubation without using bronchoscope . spo2 was maintained at between 98 - 100% , though the right thorax was still silent . 1a ) , however there was no sliding with barcode sign in the right lung ( fig . 1b ) . although the surgeon simultaneously inspected the diaphragm in detail , no apparent injuries or defects were found . because the vital signs were stable and spo2 and etco2 were normal , as indicated by an increased fio2 and respiratory rate , the operation was laparoscopically completed . when the operation was concluded , a positive end - expiratory pressure ( peep ) of 5 cmh2o was applied to inflate the collapsed lung . the patient was examined using ultrasonography whilst in the supine position , and at the same time , portable chest radiography was called to assess a pneumothroax . the ultrasonographic probe was placed on the right lower lateral chest wall between anterior and mid axillary line ( fig . 2 ) , and we identified the " lung point " sign , which can be used to diagnose pneumothorax . also , chest radiography indicated a < 30% collapse of the right lung ( fig . auscultation of the right lung improved , as well as the appearance of lung sliding sign and the disappearance of the lung point sign in whole right hemithorax within about 30 minutes after the end of the operation . no hemodynamic instability was noted , and spo2 was maintained at 100% using only medical air . hence , pneumthorax was considered to be capnothorax , and the patient was extubated without the insertion of a chest tube . the patient was transferred to the postanesthetic care unit ( pacu ) and did not complain about any respiratory disturbance . a 39-year - old man , 165 cm , 63 kg , was scheduled for living right donor nephrectomy via hand - assisted laparoscopic surgery ( hals ) . the induction of anesthesia with thiopental sodium , fentanyl , vecuronium and desflurane was uneventful . after co2-pneumoperitoneum was induced , the intraabdominal pressure was maintained < 14 mmhg , and etco2 , pmax , and spo2 were 33 mmhg , 23 cmh2o and 100% , respectively . when the upper pole of the kidney was approached , the diaphragm was injured by the dissector , which was immediately repaired . the surgeon inquired about the status of the right lung because the right hemidiaphragm was bulging . the lung sounds in the right chest were decreased on auscultation , and etco2 and pmax were increased to 42 mmhg and 30 cmh2o , respectively . , we evaluated the right thorax using ultrasonography ( linear probe : l25x , 6 - 12 mhz , machine : m - turbo system , sonosite inc . , bothell , wa , usa ) in the operative field , and the " lung point " sign was found at the right lower anterior axillary line ( fig . , a small amount of pneumothorax was expected . however , because the hemodynamic parameters were maintained in a normal range , the operation was continued via hals and a peep of 5 cmh2o was applied . at the end of the surgery , the surgeon requested a portable chest radiography and we concurrently examined the patient using ultrasonography in the supine position . 3b ) , and the range of the pneumothorax which was indicated by the lung point sign was gradually diminished . because signs of cardiopulmonary instability were not found and spo2 was maintained without an increase in fio2 , the insertion of a chest tube was not necessary and we safely extubated the endotracheal tube . the patient was transferred to the pacu and did not complain of any respiratory discomfort . a 40-year - old woman , 169 cm , 57 kg , underwent laparoscopic right adrenalectomy due to an adrenal pheochromocytoma . a 7.5 fr 3-lumen catheter was inserted under ultrasonographic guidance ( linear probe : ust-5546 , 5 - 10 mhz , machine : prosound ssd-4400 , aloka medical , co. , ltd . , tokyo , japan ) into the right internal jugular vein , and lung sliding was confirmed in both thoraces . next , the patient was placed into the left lateral decubitus position . before incision , etco2 , pmax , and peripheral oxygen saturation ( spo2 ) pneumoperitoneum was established using co2 , intraabdominal pressure was maintained < 15 mmhg , and pmax was 23 cmh2o at the time . thirty minutes after inducing pneumoperitoneum , the etco2 and pmax levels gradually increased to 43 mmhg and 30 cmh2o , respectively . however , the right side of the chest demonstrated no sounds . immediately , the fraction of inspired oxygen ( fio2 ) increased from 0.5 to 0.8 , and the endotracheal tube was withdrawn back to 2 cm in order to rule out endobronchial intubation . because the depth of the endotracheal tube was 18 cm at the incisor teeth and confirmed the depth of endotracheal tube by cuff palpation at the sternal notch , we supposed that it was enough to rule out one - lung intubation without using bronchoscope . spo2 was maintained at between 98 - 100% , though the right thorax was still silent . 1a ) , however there was no sliding with barcode sign in the right lung ( fig . 1b ) . although the surgeon simultaneously inspected the diaphragm in detail , no apparent injuries or defects were found . because the vital signs were stable and spo2 and etco2 were normal , as indicated by an increased fio2 and respiratory rate , the operation was laparoscopically completed . when the operation was concluded , a positive end - expiratory pressure ( peep ) of 5 cmh2o was applied to inflate the collapsed lung . the patient was examined using ultrasonography whilst in the supine position , and at the same time , portable chest radiography was called to assess a pneumothroax . the ultrasonographic probe was placed on the right lower lateral chest wall between anterior and mid axillary line ( fig . 2 ) , and we identified the " lung point " sign , which can be used to diagnose pneumothorax . also , chest radiography indicated a < 30% collapse of the right lung ( fig . auscultation of the right lung improved , as well as the appearance of lung sliding sign and the disappearance of the lung point sign in whole right hemithorax within about 30 minutes after the end of the operation . no hemodynamic instability was noted , and spo2 was maintained at 100% using only medical air . hence , pneumthorax was considered to be capnothorax , and the patient was extubated without the insertion of a chest tube . the patient was transferred to the postanesthetic care unit ( pacu ) and did not complain about any respiratory disturbance . a 39-year - old man , 165 cm , 63 kg , was scheduled for living right donor nephrectomy via hand - assisted laparoscopic surgery ( hals ) . the induction of anesthesia with thiopental sodium , fentanyl , vecuronium and desflurane was uneventful . after co2-pneumoperitoneum was induced , the intraabdominal pressure was maintained < 14 mmhg , and etco2 , pmax , and spo2 were 33 mmhg , 23 cmh2o and 100% , respectively . when the upper pole of the kidney was approached , the diaphragm was injured by the dissector , which was immediately repaired . the surgeon inquired about the status of the right lung because the right hemidiaphragm was bulging . the lung sounds in the right chest were decreased on auscultation , and etco2 and pmax were increased to 42 mmhg and 30 cmh2o , respectively . , we evaluated the right thorax using ultrasonography ( linear probe : l25x , 6 - 12 mhz , machine : m - turbo system , sonosite inc . , bothell , wa , usa ) in the operative field , and the " lung point " sign was found at the right lower anterior axillary line ( fig . however , because the hemodynamic parameters were maintained in a normal range , the operation was continued via hals and a peep of 5 cmh2o was applied . at the end of the surgery , the surgeon requested a portable chest radiography and we concurrently examined the patient using ultrasonography in the supine position . 3b ) , and the range of the pneumothorax which was indicated by the lung point sign was gradually diminished . because signs of cardiopulmonary instability were not found and spo2 was maintained without an increase in fio2 , the insertion of a chest tube was not necessary and we safely extubated the endotracheal tube . the patient was transferred to the pacu and did not complain of any respiratory discomfort . patients under general anesthesia may develop pneumothorax due to a variety of reasons , such as barotraumas , rupture of the lung bullae or needle insertion into the pleural cavity . capnothorax due to co2 during laparoscopic surgery is rare , but , it has been described as a complication of almost every type of laparoscopic surgery [ 1 - 3,6 - 8 ] . it has been speculated that an abnormal diaphragm caused by congenital failure of fusion ( e.g. , sternal , costal , and lumbar portions ) , weak point ( e.g. , around the aorta , vena cava , and esophagus ) , congenital defects or iatrogenic injuries by the instrument can lead to capnothorax [ 1 - 3,6 ] . because the creation of pneumoperitoneum and positional changes can demonstrate several potential physiological alterations , the accurate diagnosis of pneumothorax is more difficult during laparoscopic surgery than other surgical procedure . when pneumothorax is suspected , it is traditionally diagnosed by portable chest radiography in the operating room . however , chest radiography may take a considerable amount of time and demonstrates a sensitivity of 31.8 - 75.5% for the diagnosis of pneumothorax [ 10 - 12 ] . in many different fields , lung ultrasonography is often used to diagnose pathological conditions of the lung . in particular , ultrasonography has received attention as a very effective method for confirming pneumothorax at the bedside in the operating room . in numerous studies , ultrasonography has been reported as superior to conventional portable chest radiography for the detection of pneumothorax [ 4,10 - 13 ] . the presence or absence of characteristic ultrasonographic signs are key to a correct diagnosis , i.e. , lung sliding , lung pulse , comet - tail artifact , barcode sign ( stratosphere sign ) , seashore sign and lung point sign . among these signs , however , the absence of lung sliding does not always indicate pneumothorax due to several mechanical factors ( e.g. , poor technique , inappropriate ultrasound probe frequency , the presence of dynamic noise filters ) and the patient 's affliction ( e.g. , main bronchial intubation , emphysema , atelectasis , pleural calcification , pleural adhesion , lung fibrosis ) . for these reasons , more specific ultrasonographic methods are needed to confirm pneumothorax . in a particular area of the thorax , the ultrasonographic patterns of pneumothorax and the normal lung alternatively appear depending on the respiratory cycle . this can be explained by a slight increase in pulmonary volume during inspiration and can be observed in two ultrasonographic modes : real - time ( b - mode ) and time - motion ( m - mode ) . in b - mode , the lung point sign can be found by observing lung - sliding and absent of lung - sliding alternately at a same pleural line . analogous patterns also can be found in m - mode . seashore sign and barcode sign can be observed in turn , and these signs demonstrate the specificity of 100% for the diagnosis of pneumothorax . furthermore , by serially observing the location of the sign , the extension of pneumothorax may be identified . despite this wide spread practice , there are few studies about the relationship between the lung point sign and the extension of pneumothorax . when it moves to the lower lateral chest wall , the volume of pneumothorax expands and the patient may need to have a chest tube immediately inserted . on the other hand , movement of the sign from the lower lateral chest to the anterior chest indicates an improvement in pneumothorax ( fig . 3 ) . if capnothorax is highly suspected and cardiopulmonary instability is not severe , alteration of the " lung point " sign can be used to identify improvements in pneumothorax . in addition , for faster recovery of capnothorax , application of peep is supportive method to absorb co2 more readily from the pleural cavity . therefore , a chest tube insertion , which can cause injury to other structures in the thorax , may not be necessary in these cases . in conclusion , the lung point sign may predict the range and amount of pneumothorax during laparoscopic surgery . ultrasonography can not only help to diagnose pneumothorax , but can also be used to decide treatment of pneumothorax . most notably , in the case of capnothorax which resolves spontaneously as time goes on , the unnecessary insertion of a chest tube may be avoided by observing alterations in the lung point sign .
pneumothorax during general anesthesia is more difficult to diagnose compared with that of non - anesthetized patient . 
 furthermore , the early diagnosis of pneumothorax is to some extent difficult due to co2-pneumoperitoneum during laparoscopic surgery . 
 the use of ultrasonography to diagnose pneumothorax has increased in a variety of situations , demonstrating a better diagnostic rate than conventional chest radiography . here , 
 we report two cases of intraoperative capnothorax that were confirmed using the m - mode " lung point " sign . 
 however , the insertion of a chest tube could have been avoided because the spontaneous resolution of capnothorax was quickly identified using bedside lung ultrasonography .