for patients with non - small cell lung cancer ( nsclc ) , physicians have long been puzzled by the task of identifying candidates who may suffer major postoperative cardiopulmonary complications if they were to undergo lung resection surgery . among the few available tests , the cardiopulmonary exercise test ( cpet ) is a standard tool to assess the surgical risk of patients with nsclc [ 13 ] . specifically , maximal oxygen uptake ( vo2max ) during symptom - limited exercise was found to be a more reliable than other parameters of spirometry , such as forced expiratory volume in 1 second ( fev1 ) or the ratio of fev1 against forced vital capacity ( fvc ) , to predict postoperative morbidity and mortality among nsclc patients . as an alternative to cpet , excise - based diagnostic tests , such as stair - climbing test ( sct ) , have been reported to be a safe , economical way to assess risk - associated factors of patients [ 47 ] . interestingly , for patients with nsclc , since sct requires patients to ride cycles , it is more stressful than cardiopulmonary exercise and can be considered as valid tool to detect any abnormalities in the oxygen transport system . thus , it is plausible that sct may be helpful in predicting cardiopulmonary complications after lung resection . however , definitive evidence is lacking to determine whether sct is superior to cpet to predict postoperative cardiopulmonary complications for patients with nsclc . in this study , we used statistical methods to assess whether the key parameters of sct , including exercise oxygen desaturation ( eod ) , may be independent and proficient prognostic factors predicting postoperative cardiopulmonary complications among patients with nsclc who received various extents of lung resection . in this study , all protocols were reviewed and approved by the ethics committee at the cancer hospital ( institute ) , chinese academy of medical sciences in beijing , china . a total of 413 patients with non - small cell lung cancer ( nsclc ) performer the stair - climbing test between january 2010 and july 2015 . we excluded 74 patients due to lack of complete clinical data , 53 patients were excluded because they failed to correctly perform the pulmonary function test , 12 patients were excluded as they received lung resection and esophagectomy at the same time , and 103 patients were excluded because they did not receive surgery afterwards . thus , 171 eligible nsclc patients were enrolled in this study , including 41 females and 130 males . none of the patients had received any antineoplastic therapy such as radiotherapy and/or chemotherapy in the 6 months prior to surgery . all patients in the study participated in the symptom - limited stair - climbing test preoperatively by climbing 5 floors from the 1 floor to the 6 floor in our surgical building . there are 20 steps and 1 intermediate landing between each floor , and each step is 0.153 m in height . the patients were instructed before the stair - climbing test and encouraged to climb the stairs as fast as they could without stopping to rest until they reached the highest floor possible . the maximum height ( to the 6 floor ) was 18.4 m. the test was complete when patients reached either the 6 floor or the patients presented an apparent symptom such as severe dyspnea with oxygen desaturation , severe leg fatigue , or chest pain , which indicated exhaustion and they could not climb any more . all patients were accompanied by 2 physicians all the time during the test , who would monitor their symptoms and recorded test results simultaneously . heart rate and capillary oxygen saturation were recorded before the test , at each floor during the test , and after resting for 15 min after completing the test , using a portable pulse - oxy meter with finger probe , called the autobox ( newtech , shenzhen , china ) . the resting oxygen saturation ( osat ) and lowest osat during the test were recorded and used to calculate the desaturation level . for air leak management , single thoracic drainage in the chest was induced into the 2 intercostal space , midclavicular line ( pneumonectomy ) , and the 7 intercostal axillary line ( wedge resection and lobectomy ) . with the exception of pneumonectomy , all the drainage tubes were put into the chest with the front - most end reaching the top of the chest . at the end of the operation , residual lung tissues were carefully examined , and then air - leak tissue was stitched by prolene thread until there was no air leak from the residual lung tissue . spirometry , flow - volume curves , and absolute lung volumes were measured using a pulmonary function test apparatus . the diffusion capacity for carbon monoxide ( dlco ) was determined using a standard single - breath technique . best results were selected in 2 acceptable measuring results at intervals of at least 510 min between 2 measurements . all patients underwent surgical resection for lung cancer by either thoracotomy ( n=129 ) or video - assisted thoracoscopic surgery ( vats , n=42 ) . procedures included pneumonectomy in 22 cases , lobectomy in 122 cases , and pulmonary wedge resection in 27 cases . postoperative treatment was focused on early mobilization , chest physiotherapy and physical rehabilitation , pain control , and antibiotic and anti - thrombotic prophylaxis . postoperative complications and deaths were defined as those occurring 030 days postoperatively , according to the guideline reported by bolliger et al . , smith et al . , and brutsche et al . . statistical analyses were performed using sas software ( sas institute , cary , nc ) . categorical variables of clinical characteristics are shown as percentages and were compared using the chi - square test . continuous variables are presented as means  standard deviations and compared by use of the t test . the utility of the complication as a predictive marker for drainage tube length of postoperative stay and hospital stay was investigated using kaplan - meier analysis . logistic regression analysis was used to determine the association of preoperative factors with postoperative complications . factors with a significant difference in univariate analysis ( p value < 0.05 ) were measured again by multivariate analysis to determine their independence . a p value in this study , all protocols were reviewed and approved by the ethics committee at the cancer hospital ( institute ) , chinese academy of medical sciences in beijing , china . a total of 413 patients with non - small cell lung cancer ( nsclc ) performer the stair - climbing test between january 2010 and july 2015 . we excluded 74 patients due to lack of complete clinical data , 53 patients were excluded because they failed to correctly perform the pulmonary function test , 12 patients were excluded as they received lung resection and esophagectomy at the same time , and 103 patients were excluded because they did not receive surgery afterwards . thus , 171 eligible nsclc patients were enrolled in this study , including 41 females and 130 males . none of the patients had received any antineoplastic therapy such as radiotherapy and/or chemotherapy in the 6 months prior to surgery . all patients in the study participated in the symptom - limited stair - climbing test preoperatively by climbing 5 floors from the 1 floor to the 6 floor in our surgical building . there are 20 steps and 1 intermediate landing between each floor , and each step is 0.153 m in height . the patients were instructed before the stair - climbing test and encouraged to climb the stairs as fast as they could without stopping to rest until they reached the highest floor possible . the maximum height ( to the 6 floor ) was 18.4 m. the test was complete when patients reached either the 6 floor or the patients presented an apparent symptom such as severe dyspnea with oxygen desaturation , severe leg fatigue , or chest pain , which indicated exhaustion and they could not climb any more . all patients were accompanied by 2 physicians all the time during the test , who would monitor their symptoms and recorded test results simultaneously . heart rate and capillary oxygen saturation were recorded before the test , at each floor during the test , and after resting for 15 min after completing the test , using a portable pulse - oxy meter with finger probe , called the autobox ( newtech , shenzhen , china ) . the resting oxygen saturation ( osat ) and lowest osat during the test were recorded and used to calculate the desaturation level . for air leak management , single thoracic drainage in the chest was induced into the 2 intercostal space , midclavicular line ( pneumonectomy ) , and the 7 intercostal axillary line ( wedge resection and lobectomy ) . with the exception of pneumonectomy , all the drainage tubes were put into the chest with the front - most end reaching the top of the chest . at the end of the operation , residual lung tissues were carefully examined , and then air - leak tissue was stitched by prolene thread until there was no air leak from the residual lung tissue . spirometry , flow - volume curves , and absolute lung volumes were measured using a pulmonary function test apparatus . the diffusion capacity for carbon monoxide ( dlco ) was determined using a standard single - breath technique . best results were selected in 2 acceptable measuring results at intervals of at least 510 min between 2 measurements . all patients underwent surgical resection for lung cancer by either thoracotomy ( n=129 ) or video - assisted thoracoscopic surgery ( vats , n=42 ) . procedures included pneumonectomy in 22 cases , lobectomy in 122 cases , and pulmonary wedge resection in 27 cases . postoperative treatment was focused on early mobilization , chest physiotherapy and physical rehabilitation , pain control , and antibiotic and anti - thrombotic prophylaxis . postoperative complications and deaths were defined as those occurring 030 days postoperatively , according to the guideline reported by bolliger et al . , statistical analyses were performed using sas software ( sas institute , cary , nc ) . categorical variables of clinical characteristics are shown as percentages and were compared using the chi - square test . continuous variables are presented as means  standard deviations and compared by use of the t test . the utility of the complication as a predictive marker for drainage tube length of postoperative stay and hospital stay was investigated using kaplan - meier analysis . logistic regression analysis was used to determine the association of preoperative factors with postoperative complications . factors with a significant difference in univariate analysis ( p value < 0.05 ) were measured again by multivariate analysis to determine their independence . a total of 171 non - small cell lung cancer patients were included in the study . one of these deaths was a 75-year - old male and another was a 59-year - old female , whose exercise oxygen desaturation ( eod ) were both greater than 5 , and both died from respiratory failure 1 and 80.5 , respectively , days postoperatively despite being supported by mechanical ventilation . the third patient was a 64-year - old male who died from postoperative bleeding in the chest after a lobectomy . there was no air leak from the chest of patients for more than 2 days before closing the chest , and no patient had empyema . baseline information and the comparison between the complication group and the complication - free group are shown in table 2 . there were no significant differences in sex ratio , bmi , smoking , lung resection , spirometry measurements ( fev1 , mvv% , dlco and dlco% ) , or stair - climbing test results ( pre - climb sao2 , climbing - end sao2 , and climbing - end heart rate ) between the groups . while comparing those parameters between the complication group and the complication - free group , there were significant differences in age , fev1% , mvv , height of climbing , eod , and heart rate change between the 2 groups . finally , logistic regression analysis showed that eod and heart rate change were independent predictors of complications ( table 3 ) . a model for predicting the probability of postoperative complications based on logistic regression was hypothesized as : probability = e/(1+e ) , =1.136 + ( 0.114eod ) + ( 0.040heart rate change ) , in which e represented the base of natural logarithms and the  was the regression coefficient in the logistic regression . the accuracy of the model was evaluated by use of the roc curve , which showed that the area under the roc curve ( auc ) was 0.750 ( 95% ci : 0.6680.831 ) ( figure 1 ) . if the cutoff probability value was larger than 0.193 , the patient was considered to have high risk of suffering from postoperative cardiopulmonary complications , and vice versa . patients without a postoperative cardiopulmonary complication had a median length of drainage time of 4.3 days ( 95% ci , 3.44.5 ) and a median length of hospital stay of 9.4 days ( 95% ci , 8.99.8 ) , as compared to 5.9 days ( 95% ci , 5.36.4 ) ( figure 2 , p<0.001 ) , and 13.1 days ( 95% ci , 10.915.3 ) ( figure 3 , p<0.001 ) for patients with postoperative complications . complications such as chronic obstructive pulmonary disease ( copd ) and coronary artery disease are very common among those patients , with high risk of surgical morbidity and mortality . thus , it is critical to perform preoperative assessment on cardiopulmonary function to predict the risk of postoperative complications and death . use of vital capacity for the prediction of surgical risk was first reported as early as 1955 . since then , lung functional testing has been used to predict the risk of postoperative complications and even mortality . the 2 most commonly used parameters of conventional pulmonary function test are fev1 and dlco , which were confirmed by univariate analysis in our study . however , multivariate analysis showed that fev1% was not an independent predictor of postoperative complications for patients with nsclc . before this study , poor exercise capacity has long been used as the major predictor of postoperative cardiopulmonary complications after lung resection in patients with nsclc . however , nsclc patients with poor exercise capacity not only have high risk of postoperative cardiopulmonary complications , but also have longer hospital stay . in the present study , our results showed that eod and heart rate change were independent predictors of postoperative cardiopulmonary complications for patients with nsclc , confirming the predictions from other studies . brunelli reported that complication rates in patients with and without eod > 4% and < 4% were 36% and 22% , respectively . in addition , a previous study by our team found the rate of postoperative cardiopulmonary complications was significantly higher in patients with eod 5% and heart rate change < 55 beats / min than that in the group with eod < 5% and heart rate change 55 beats / min . therefore , in the present study , we successfully established a model to predict the risk of postoperative cardiopulmonary complication using scts parameters of eod and heart rate change . it is worth noting that , in the present study , the patients without postoperative cardiopulmonary complication had a shorter hospital stay than those with postoperative cardiopulmonary complications . also , the patients without postoperative cardiopulmonary complication had a shorter drainage time than those with postoperative cardiopulmonary complications . the possible explanation is that a patient who has postoperative cardiopulmonary complications creates more pleural effusion than one does not , further confirming that sct may be an effective method to predict postoperative cardiopulmonary complications in nsclc patients . however , well - established formal cardiopulmonary exercise testing ( cpet ) is still be recommended for precise assessment of these patients with high eod or low heart beat change during the stair - climbing test . we provided definitive evidence that eod and heart rate change in sct are independent predictors for postoperative cardiopulmonary complications in nsclc patients . a follow - up study with a much larger patient pool however , based on the information of our study , it is highly recommended for all lung resection candidates with poor conventional function test results to perform a stair - climbing test .
backgroundthere is currently no reliable method to predict major postoperative cardiopulmonary complications for patients with non - small cell lung cancer ( nsclc ) . in this study 
 , we hypothesized that exercise oxygen desaturation ( eod ) and heart rate change results in a stair - climbing test ( sct ) would predict postoperative cardiopulmonary complications for patients with nsclc.material/methodswe examined 171 patients ( 41 females and 130 males ) with nsclc by preoperative sct from january 2010 to july 2015 . among them , 27 underwent wedge resection , 122 underwent lobectomy , and 22 underwent pneumonectomy . 
 the correlation between postoperative cardiopulmonary complications and parameters of sct and pulmonary function test ( pft ) parameters were analyzed retrospectively.resultsthe overall 30-day postoperative morbidity of the patients was 46/171 ( 26.9% ) , with death occurring in 3/171(1.8% ) . 
 the age , fev1% , mvv , height of climbing , eod , and heart rate change were found to be significantly different between the group with postoperative cardiopulmonary complications and those without . 
 binary logistic regression analysis showed that eod and heart rate change were independently correlated with postoperative cardiopulmonary complications . 
 in addition , a model predicting the probability of postoperative cardiopulmonary complication based on logistic regression for multivariable analysis was used to confirm our findings.conclusionsa symptom - limited sct with oxygen saturation monitoring is a safe , simple , and low - cost method to evaluate cardiopulmonary function preoperatively .