耐多药肺结核133例外科治疗效果探讨

目的 探讨肺切除术在耐多药肺结核治疗中的重要性.方法 回顾性分析北京胸科医院1980年1月至2007年12月行肺切除术治疗的133例耐多药肺结核患者的临床资料.手术方式包括全肺切除(45例)、肺叶切除(73例,包括支气管袖式成型5例)、胸膜全肺切除(13例)、肺段切除(1例)、楔形切除(1例),术前均进行6个月以上的抗结核治疗,术后继续抗结核治疗6～18个月.结果 133例中围手术期死于呼吸衰竭的2例,内出血1例,死亡3例(2.3%);并发症发生率为17.3%(23/133),其中支气管残端瘘9例.术后随访6个月至15年,平均52个月,用药时间为6～18个月,痰MTB阴转率为90.2%(101/112).结论 对持续痰MTB阳性,且病灶局限或痰MTB转阴、病灶局限,继续抗结核治疗3个月以上病变无好转或加重的耐多药肺结核患者,应积极采取手术治疗,肺切除术能有效提高患者的治愈率.应用吻合器缝合残端可明显降低瘘的发生率.     

Results of surgical treatment of 107 patients with complications of pulmonary tuberculosis

Abstract The objective of this study was to evaluate the results of surgical intervention performed on 107 patients with pulmonary tuberculosis complications. Between September 1988 and December 1995, 107 patients underwent a total of 126 operations for major complications of pulmonary tuberculosis. One hundred and twenty-six operations consisted of lobectomies only or plus other lung resections performed in 55 cases, pneumonectomies in 20 cases, segmentectomies in 18 cases, wedge resections in two cases, tracheobronchoplasties in four cases, decortications in two cases, cavernostomies with concomitant muscle transpositions in seven cases, thoracoplasties reserved for the previously failed operations or to be a supplement for pulmonary resections in 18 cases. The operative mortality rate was of 1.8%, and the major complication rate was of 16.8%. Twenty-eight (26.1%) patients with tuberculosis bacilli in sputum before operation have converted except one diabetic patient. In conclusion, surgery is indicated in pulmonary tuberculosis complications that are life-threatening or unresponsive to chemotherapy. Pulmonary resection is the procedure of choice for most cases that require surgery.     

长期排菌肺结核的外科治疗

目的 探讨肺结核化疗时代外科治疗长期排菌病例的重要性。方法 对６５例患者进行不同术式肺切除术和（或）胸廓改型术并进行抗结核治疗。结果 ６３例痰菌阴转；１例痰菌转阳，经再手术好转。１例术后因呼吸衰竭死亡；３例并发脓胸，经再手术好转，结论 外科治疗是治疗长期排菌等难治性肺结核的重要方法。     

手术联合化疗治疗耐多药肺结核结果分析

目的临床上耐多药肺结核患者治疗效果往往不佳。探讨手术联合化疗治疗耐多药肺结核患者的疗效。方法对1995年4月—2005年3月住院的48例采用外科手术治疗+化疗的耐多药肺结核患者进行分析。肺部有空洞病变36例(75%),双侧肺均有病变16例(33.3%)。手术方式包括肺叶切除28例,全肺切除15例,胸膜全肺切除3例,肺段切除1例,楔形切除1例。结果术后死亡率2.1%(n=1)。并发症发生率16.7%(n=8)。术后随访6～90个月。痰菌阴转率83.3%。结论耐多药肺结核患者若有良好的心肺功能储备,手术治疗安全有效,配合化疗能提高患者的治愈率。     

Active pulmonary tuberculosis: experience with resection in 106 cases

The surgical management of pulmonary tuberculosis has evolved since collapse therapy was the mainstay of treatment. Despite this, resection for active tuberculosis is viewed with circumspection. Details of 106 patients with pathologically proven active pulmonary tuberculosis, who were operated on from January 1997 to January 2005, were reviewed retrospectively. Demographic data, radiographic profiles, indications for surgery, sputum status, and preoperative drug therapy were analyzed in relation to outcomes. The indications for surgery included multidrug-resistant tuberculosis in 27 patients, hemoptysis in 44, bronchiectasis in 27, and diagnostic dilemmas where a tumor could not be excluded in 8. All patients were operated on while receiving antituberculous therapy, and 17 were sputum positive at the time of surgery. Two (1.9%) patients died postoperatively. Morbidity was 16.9%, including 6 cases of postpneumonectomy empyema and one of bronchopleural fistula. Surgery for active tuberculosis may be undertaken with acceptable morbidity and mortality.     

Lung resection for multidrug-resistant tuberculosis

The emergence of multidrug-resistant tuberculosis poses a serious challenge to traditional drug therapy. In view of the relapse rate of up to 50% following medical management, there has been renewed interest in the role of surgery for this problem. We report our experience with lung resection for this condition. Over a 5-year period, resection was performed in 23 patients who were diagnosed with multidrug resistance after completing a course of standard chemotherapy and at least 3 months of second-line therapy. Pneumonectomy was performed in 17 patients and lobectomy in 6. There was no operative or postoperative mortality. Major complications developed in 4 patients (17.4%): 2 had post-pneumonectomy empyema and 2 underwent rethoracotomy for bleeding. Ten patients were sputum positive preoperatively, and only 1 remained positive after surgery. The patients were put on appropriate chemotherapy and followed up for 18 months. The cure rate was 95.6%. Pulmonary resection can be considered as an important adjunct to medical therapy in carefully selected patients: those who have localized disease with adequate pulmonary reserve, or who have multiple previous relapses, or whose sputum remains positive after 4 to 6 months of appropriate medical treatment. Surgery offers high cure rates with acceptable morbidity and mortality.     

结核性支气管狭窄的诊断及外科治疗

目的探讨药物治疗不愈的结核性支气管狭窄患者的诊断及外科治疗。方法对４６例外科诊断明确的结核性支气管狭窄采用肺切除和支气管成型术。支气管成型术包括肺叶状成型术，总支气管楔形切除术及总支气管袖状切除术。结果４６例结核性支气管狭窄患者得到治愈，无残端和吻合口瘘；痰菌全部转阴；无狭窄复发。结论治疗结核性支气管狭窄肺切除是常规的治疗方法，支气管成形术是理想的手术方法     

耐多药肺结核188例的外科治疗

目的总结耐多药肺结核（MDR—PTB）的外科治疗经验。方法上海市肺科医院胸外科自1990年1月至2005年11月共行肺结核手术906例，其中MDR—PTB188例（20．8％），手术200例次，2次手术12例；肺叶切除85例次，肺叶切除并袖式及气管、支气管成形16例次，全肺切除48例次，余肺切除术3例次，支气管胸膜瘘（BPF）瘘管修补术5例次，胸廓成形并BPF修补22例次，脓胸剥脱并BPF修补6例次，开窗引流9例次，肋床引流5例次，右总支气管节段切除1例次。术前均行有效个体化抗结核治疗2—3个月。结果术中死亡率为0．5％（1／200）。术后1年内死亡率为3．2％（6／187），其中呼吸衰竭和心肌梗死各2例，肾衰竭和大咯血各1例。并发症率为13．9％（26／187），BPF11例，占并发症的42．3％（12／26）。所有患者术前痰菌均为阳性，术后阳性2例。随访时间6．7年（3个月至15年）。术后继续术前的抗结核方案治疗3—18个月。结论对持续痰菌阳性、病灶已局限的耐多药肺结核患者，应在有效抗结核治疗的基础上手术治疗。     

Surgical resection of persistent pulmonary fungus nodules and secondary prophylaxis are effective in preventing fungal relapse in patients receiving chemotherapy or bone marrow transplantation for leukemia

Antifungal therapy may be unable to eradicate invasive mycosis in leukemia patients. The presence of persisting pulmonary nodules owing to mycosis seems to increase the risk of fungal relapse after chemotherapy and transplant procedures. Between 1997 and 2004, 10 acute leukemia patients underwent pulmonary surgery for invasive mycosis. The median time from diagnosis of mycosis to surgery was 135 days (range 21-147). Three patients underwent emergency surgery, owing to hemoptysis. In the other seven patients with nodule/cavitation remaining after antifungal treatment, surgery (three wedge resections, four lobectomies) was scheduled before transplant. Pathologic examination confirmed two aspergillosis and three zygomycosis. The only side effect was pneumothorax in one case. Nine patients were considered cured. Six patients underwent bone marrow transplantation (three allogeneic, three autologous) with antifungal prophylaxis without relapse during the transplant procedure. In selected patients scheduled for bone marrow transplantation, surgical resection of localized pulmonary fungus nodules combined with antifungal prophylaxis seem to be an effective treatment for preventing mycotic relapse.     

Efficacy and safety of kanamycin, ethionamide, PAS and cycloserine in multidrug-resistant pulmonary tuberculosis patients

BACKGROUND: We carried out this study to determine the efficacy and safety of a regimen containing kanamycin, ethionamide, isoniazid, para-aminosalicylic acid (PAS) and cycloserine in the treatment of multidrug-resistant tuberculosis (MDR-TB). METHODS: A prospective, uncontrolled study of 39 pulmonary tuberculosis patients, who had received adequate first-line antituberculosis treatment including supervised category II retreatment regimen, and were still sputum smear positive for acid-fast bacilli (AFB) in whom sputum culture revealed isolates of M. tuberculosis resistant to rifampicin and isoniazid with and without resistance to other antituberculosis drugs. They received kanamycin (initial 4-6 months), ethionamide, isoniazid, PAS and cycloserine for a minimum period of two years. RESULTS: Out of 39 patients, 29 (74.3%) achieved sputum conversion within six months and remained so at the end of two years. Two (5.1%) patients died, six (20.6%) patients were lost to follow up, and two (5.1%) patients remained sputum smear-positive for AFB through out the period of study. Twenty-nine patients, declared cured, were followed for an average period of 16 months (3-48 months), during which two (6.9%) patients relapsed, four (13.8%) patients were lost to follow-up and remaining 23 remained sputum smear-negative. Eight (21.1%) patients developed major side effects which required stoppage/change of drugs. CONCLUSION: In MDR-TB patients, regimen consisting of ethionamide, isoniazid, PAS and cycloserine and kanamycin appears to be effective and safe.     

Induced sputum improves the diagnosis of pulmonary tuberculosis in hospitalized patients in Gaborone, Botswana

SETTING: Low sensitivity of acid-fast bacilli (AFB) sputum smears and absence of productive cough are obstacles to the diagnosis of pulmonary tuberculosis (PTB) in hospitals that lack access to bronchoscopy. OBJECTIVES: To evaluate induced sputum, gastric content, blood and urine specimens to improve PTB diagnosis in patients not diagnosed by expectorated sputum AFB smears. DESIGN: Patients admitted to the medical wards of a large public hospital in Gaborone, Botswana, were prospectively enrolled if they had symptoms consistent with PTB, an abnormal chest radiograph, were treated empirically with anti-tuberculosis chemotherapy or had no improvement on antibiotics, and had a non-productive cough or AFB smear-negative sputum. Induced sputum was stained for AFB and Mycobacterium tuberculosis cultures were performed on induced sputum, gastric contents, urine and blood. RESULTS: Of 140 patients meeting the enrollment criteria, 113 (81%) were human immunodeficiency virus (HIV) positive. Fifty-seven (41%) had PTB based on positive cultures from one or more sites, including 48 (84%) from induced sputum, 17 (30%) urine, 13 (23%) gastric contents and 7 (12%) blood. AFB smears were positive in only 18 (32%) culture-proven PTB cases. CONCLUSION: Induced sputum cultures greatly enhanced M. tuberculosis detection in patients with a high prevalence of HIV/AIDS in a hospital without access to bronchoscopy.     

Surgery for pulmonary tuberculosis

PURPOSE OF REVIEW: The role of thoracic surgery in pulmonary tuberculosis, in either a diagnostic or a therapeutic role, is well established. This review aims to underline the current indications for lung resection, surgical strategy and outcomes associated with surgery. RECENT FINDINGS: There has been a renewed interest in surgery, mainly in the multidrug-resistant tuberculosis (MDRTB) group as an adjunct to medical therapy. Lung resection in this group of patients has been undertaken with acceptable morbidity and mortality, and with cure rates of over 90%. The current strategy favours early surgical intervention for patients with multidrug-resistant tuberculosis to prevent the development of bilateral disease. Early surgery for haemoptysis is advocated, for sometimes it is necessary to operate on these patients without a full course of antituberculous therapy. Medical stabilization and early inpatient surgery is favoured in view of the excessive mortality associated with emergency surgery. There is still no consensus on the management of the bronchial stump at the time of lung resection, although the current trend favours closure, either sutured or stapled, without muscle reinforcement. SUMMARY: Lung resection for pulmonary tuberculosis, in carefully selected and prepared patients, is safe with acceptable morbidity and mortality.     

Role and outcome of surgery for pulmonary tuberculosis

The need and outcome of surgical intervention in patients with pulmonary tuberculosis were assessed retrospectively. Between 1993 and 2003, 72 major surgical procedures were performed in 57 patients with pulmonary tuberculosis. There were 44 males and 13 females with a mean age of 34 years. Indications for surgery were: trapped lung in 18 (31.6%), multidrug-resistant tuberculosis in 10 (17.5%), aspergilloma in 10 (17.5%), destroyed lung in 5 (8.8%), massive hemoptysis in 4 (7%), bronchopleural fistula in 3 (5.3%), persistent cavity in 2 (3.5%), and undiagnosed nodule in 5 (8.8%) patients. The most common procedure was lobectomy (31.9%). Other procedures included decortication, wedge resection, pneumonectomy, segmentectomy, and myoplasty. There were 28 complications in 18 patients, including prolonged air leak in 12 (21.1%), residual space in 7 (12.3%), empyema in 5 (8.8%), hematoma in 2 (3.5%), chylothorax and bronchopleural fistula in 1 (1.8%) each. There was no operative death, but one patient died from sepsis late in the follow-up period (mortality, 1.8%). As morbidity and mortality rates are acceptable, surgical intervention can be considered safe and effective in patients with pulmonary tuberculosis.     

643例老年肺结核病的临床分析

目的 探讨近年来老年肺结核病的临床特点,以期提高老年肺结核病的诊治水平。方法 回顾性分析解放军第三○九医院收治的643例老年肺结核患者的肺结核分型、合并疾病、痰或支气管肺泡灌洗液(BALF)中抗酸杆菌(AFB)、临床表现、影像特点、治疗结果及抗结核化疗的不良反应情况。 结果 643例患者中,继发性肺结核占93.9%（604/643）,血行播散性肺结核占6.1%（39/643）,原发性肺结核0例;总AFB阳性率为31.9%（205/643）。症状以咳嗽（514/643,79.9%）、发热（369/643,57.4%）为主,AFB阳性者咳嗽率（87.8%,180/205）高于AFB阴性者(76.3%,334/438)（χ²=11.614,P=0.001）,AFB阴性者盗汗率（32.9%,144/438）高于AFB阳性者（24.4%,50/205）（χ²=4.774,P=0.029)。所有患者中89.6%（576/643）的患者合并其他内科疾病,其中78.1%（450/576）合并2种及2种以上疾病,所有患者中以肺部感染最为常见,达51.2%（329/643）;菌阳者肺部感染率（57.1%,117/205）高于菌阴者（48.4%,212/438）（χ²=4.202,P=0.040）,女性患者（19.7％,37/188）较男性更多合并高血压（13.2％,60/455）（χ²=4.380,P=0.036）。604例继发性肺结核患者肺部病灶以浸润、坏死为主,无空洞患者病灶分布以多肺区为主(41.4％,250/604)。AFB阳性者住院期间痰菌阴转率为59.5％(122/205),治疗总有效率为87.1%（560/643）,住院病死率5.1%（33/643）。抗结核治疗不良反应以肝损害为主,占6.4％（41/643）。结论 643例老年肺结核症状以咳嗽、发热为主;病灶以多肺区为主;合并其他内科疾病几率高,并以肺部感染为首;老年肺结核的治疗应个体化。     

Clinical characteristics and treatment response among patients with multidrug-resistant tuberculosis: a retrospective study

BACKGROUND: This retrospective study was conducted to evaluate the characteristics and therapeutic response among patients with multidrug-resistant tuberculosis (MDR TB). METHODS: One hundred subjects with isolates resistant to isoniazid and rifampicin were included over a three-year period (1997-1999). There were 82% males with a mean age of 36 years, mean duration of symptoms of 29 months, and a previous history of tuberculosis in 85% (pulmonary 96% and extrapulmonary 4%). RESULTS: HIV ELISA test was positive in two out of 28 (7%) patients while diabetes was diagnosed in 16 percent. Mean time to diagnose MDR TB was 5.5 months. Subjects had received a mean of 3.2 anti-TB drugs before the diagnosis of MDR TB was made. Forty-five patients were lost to follow-up. The rest had a median follow-up of 13.5 months (range 1-37 months). Follow-up AFB smear and culture results were available in 49 out of 55 and 26 out of 55 patients, respectively. Sputum smear became negative for AFB in 26 out of 49 (53%) and culture converison occurred in 16 out of 26 (61.5%) patients. Clinical and radiological response was noted in 31 (56%) and 13 (32.5%) out of 40 patients respectively. A mean of 5.5 drugs was used in those who achieved sputum conversion. Combination therapy containing ofloxacin in the regimen was noted to have a favourable response. CONCLUSION: Only a limited number of patients with MDR tuberculosis have a favourable response.     

In vitro antituberculous activity of ofloxacin and levofloxacin against multidrug-resistant tuberculosis and clinical outcomes

OBJECTIVE: To investigate in vitro antituberculous activity of ofloxacin (OFLX) and levofloxacin (LVFX) against multidrug-resistant tuberculosis and to study the clinical outcomes. SUBJECTS AND METHODS: In vitro antituberculous activity of OFLX and LVFX against multidrug-resistant strains of Mycobacterium tuberculosis isolated from 46 patients with pulmonary tuberculosis and a retropective clinical analysis of 45 patients were investigated. RESULTS: In susceptibility testing, resistance rates to OFLX or LVFX were higher in intractable cases (7/20: 35%) and in cases with prior chemotherapy using new quinolones (5/12: 42 %). Sputum culture conversion was observed in 34 patients (76%), however 9 among them later reverted to positive culture. In a single variate proportional hazards model, risk factors related to poor outcomes (treatment failure or relapse) were resistance to OFLX or LVFX, advanced disease on chest radiograph, and the number of susceptible drugs four or less. In a multiple variate proportional hazards model, a risk factor was resistance to OFLX or LVFX. Eighteen patients (40%) died, and among them, 10 died of tuberculosis. Survival time of treatment failure patients was significantly shorter than patients with sputum culture conversion. CONCLUSION: Resistance to OFLX or LVFX was considered to be a risk factor related to treatment failure and relapse in multidrug-resistant tuberculosis.     

Pulmonary resection in the treatment of patients with pulmonary multidrug-resistant tuberculosis in Taiwan.

SETTING: Chronic Disease Control Bureau, Department of Health, Taiwan. OBJECTIVE: To evaluate the role of pulmonary resection in the treatment of pulmonary tuberculosis resistant to isoniazid and rifampin (MDR-TB). DESIGN: In a retrospective cohort study, 27 MDR-TB patients who underwent pulmonary resection between December 1990 and March 1999 were reviewed. Individually-tailored treatment regimens were selected at a once-weekly staff conference following review of the patient's case history and drug susceptibility results. Surgery was performed for selected patients, essentially those: 1) whose medical treatment had failed, or for whom treatment failure seemed highly likely, or for whom post-treatment relapse seemed likely, 2) with predominantly localised disease, 3) with adequate cardiopulmonary reserve, and 4) whose treatment regimen had been composed of at least two effective drugs to diminish the mycobacterial burden. RESULTS: There was no surgical mortality apart from one peri-operative death (4%). Three patients (11%) developed complications, and 24 (92%) patients demonstrated sputum conversion and/or remained negative after surgery. Twenty-three patients have already completed treatment, and during a mean of 42 +/- 18 follow-up months (range 15-80 months), one patient relapsed. This patient was disease-free after another course of treatment. CONCLUSION: For selected patients, pulmonary resection may improve the outcome of pulmonary MDR-TB.     

耐多药肺结核患者合并呼吸道感染的菌种分布及药敏分析

目的 了解耐多药肺结核患者合并呼吸道感染病原菌分布及耐药情况,指导临床合理用药。 方法 选取上海市肺科医院2007年1月-2009年12月住院耐多药肺结核合并呼吸道感染痰菌培养阳性病例127例及同期住院初治肺结核合并呼吸道感染痰菌培养阳性病例432例进行痰培养细菌鉴定及药敏试验,并进行分析。 结果 127例耐多药肺结核合并下呼吸道感染病例共分离出菌株151株,其中,以革兰阴性杆菌居首位,占67.5%,其次为真菌占30.5%,革兰阳性球菌占2%。与初治肺结核合并下呼吸道感染菌群比较,耐多药组肺炎克雷伯菌、大肠埃希菌、阴沟肠杆菌、不动杆菌等耐药程度较高的机会致病菌比率明显高于初治组,而较为常见、耐药程度较低的致病菌副流感嗜血杆菌则明显低于初治组,2组差异有统计学意义（P<0.05）。耐多药组真菌感染率(30.5%)高于初治肺结核组(20.6%)（P<0.05）,革兰阳性球菌感染比率低于初治肺结核组,2组差异有统计学意义（P<0.05）,混合感染率增高（P<0.05）。药敏显示革兰阴性杆菌对第三代以上头孢菌素、碳青霉烯类、喹诺酮类抗生素较敏感,细菌耐药程度增加,两组间比较有统计学意义（P<0.05）。革兰阳性球菌对青霉素、克林霉素耐药率高,对万古霉素较敏感。 结论 耐多药肺结核患者合并呼吸道感染病原菌以革兰阴性机会致病菌为主,且耐药现象严重,真菌混合感染增加。临床应重视细菌培养及药敏试验,减少不合理用药,积极治疗合并症,减少混合感染。     

New recommendations for duration of respiratory isolation based on time to detect Mycobacterium tuberculosis in liquid culture.

It was hypothesised that the time to detect Mycobacterium tuberculosis in liquid culture of sputum from patients with pulmonary tuberculosis may be a better indicator for the duration of respiratory isolation than sputum smear status. Pre-treatment and during-treatment sputum acid-fast bacilli (AFB) smear and culture results were reviewed in 284 patients with pulmonary tuberculosis. The time to detect M. tuberculosis in liquid culture (TTD-TB) was the number of days from inoculation of the Mycobacterial Growth Indicator Tube to culture detection and visualisation of AFB. The median (interquartile range) TTD-TB for smear group 0 (no bacilli seen) was 14 (12-20) days. This value was used as the standard at which release from isolation could be permitted. In smear group 4 (>9 AFB per high-power field (hpf) in sputum specimens before treatment) patients, the TTD-TB exceeded 14 days after a median of 25 days of treatment. The current authors recommend that patients in smear groups 1 and 2 (1-9 AFB per 100 hpf and 1-9 AFB per 10 hpf in sputum specimens before treatment, respectively) receive treatment in respiratory isolation for 7 days, provided the risk of drug resistance is low. Smear group 3 (1-9 AFB per hpf) and 4 patients should receive treatment in respiratory isolation for 14 and 25 days, respectively. These criteria would have reduced the duration of respiratory isolation by 1,516 days in the 143 study participants with sputum smear-positive pulmonary tuberculosis. Provided clinical and radiographical criteria are satisfactory, use of the time to detect Mycobacterium tuberculosis in liquid culture could enable the duration of respiratory isolation to be predicted from the pre-treatment sputum smear grade. The recommendations enable isolation to end well before sputum becomes smear negative, with considerable benefits to patients and healthcare providers.     

Mechanical injuries to the ipsilateral non-diseased lobes(s) during pulmonary resection--another factor causing postoperative complications

BACKGROUND: The occurrence of complications after major pulmonary resection is known to be related to various factors. However, peri-surgical injuries to the ipsilateral non-diseased lobes(s) occurring during resection have never been mentioned in the literature. This study aimed to verify the injury in cases after lobectomy and wedge resection. METHODS: Data from eighteen patients who underwent lobectomy or wedge resection for malignant tumor between January 2003 and January 2004 were collected. All patients had pre- and postoperative examinations of alveolar-capillary membrane (A/C) permeability using 99m TC-DPTA radioaerosol. RESULTS: Ten lobectomies and eight wedge resection were performed. Using the paired t-test with each patient's pre-operative A/C permeability as his own control data, the postoperative A/C permeability of the ipsilateral non-diseased lobe(s) was found to be significantly increased. The degree of increase in the lobectomy group was the same as that in the wedge resection group. However, no significant change was found on the contralateral side in both groups. CONCLUSION: The degree of increase of permeability was the same in both groups, indicating that the effects of stretch on the surviving lung are not a contributing factor to the change in A/C permeability. The mechanical injuries during the pulmonary surgical procedure alter the permeability, which could be a possible factor causing postoperative pulmonary complications.