Testing the competition-colonization trade-off with a 32-year study of a saxicolous lichen community.

Competition-colonization trade-offs are theorized to be a mechanism of coexistence in communities structured by environmental fluctuations. But many studies that have tested for the trade-off have failed to detect it, likely because a spatiotemporally structured environment and many species assemblages are needed to adequately test for a competition-colonization trade-off. Here, we present a unique 32-year study of rock-dwelling lichens in New Mexico, USA, in which photographs were used to quantify lichen life history traits and interactions through time. These data allowed us to determine whether there were any trade-offs between traits associated with colonization and competition, as well as the relationship between diversity and disturbance in the community. We did not find evidence for a trade-off between competitive ability and colonization rate or any related life history traits. Interestingly, we did find a peak in all measures of species diversity at intermediate levels of disturbance, consistent with the intermediate disturbance hypothesis pattern. We suggest that the coexistence of the dominant species in this system is regulated by differences in persistence and growth rate mediating overgrowth competition rather than a competition-colonization trade-off.

Size and albedo of Kuiper belt object 55636 from a stellar occultation.

The Kuiper belt is a collection of small bodies (Kuiper belt objects, KBOs) that lie beyond the orbit of Neptune and which are believed to have formed contemporaneously with the planets. Their small size and great distance make them difficult to study. KBO 55636 (2002 TX(300)) is a member of the water-ice-rich Haumea KBO collisional family. The Haumea family are among the most highly reflective objects in the Solar System. Dynamical calculations indicate that the collision that created KBO 55636 occurred at least 1 Gyr ago. Here we report observations of a multi-chord stellar occultation by KBO 55636, which occurred on 9 October 2009 ut. We find that it has a mean radius of 143 +/- 5 km (assuming a circular solution). Allowing for possible elliptical shapes, we find a geometric albedo of in the V photometric band, which establishes that KBO 55636 is smaller than previously thought and that, like its parent body, it is highly reflective. The dynamical age implies either that KBO 55636 has an active resurfacing mechanism, or that fresh water-ice in the outer Solar System can persist for gigayear timescales.

Predictors of operative time in multicenter port-access valve registry: institutional differences in learning.

BACKGROUND: The predictors of operative time and the effects of learning in isolated valve operations using port-access techniques have not been defined. METHODS: Analysis of covariance was used to examine the determinants of procedure time, pump time, and aortic clamp time. In the largest prospective, registry of patients undergoing isolated aortic valve replacement (AVR, N=199), mitral repair (MVP, N=307), or mitral replacement (MVR, N=232) using port-access techniques 1997-1999 at 27 institutions. RESULTS: Institutional case volume ranged from one to 214 (median 6). Operative time was longer in redo procedures (5.3 +/- 1.6 vs. 4.4 +/- 1.3 hr, p = 0.0001), longer with MVP or MVR vs. AVR (4.8 +/- 1.2 vs. 5.0 +/- 1.5 vs. 3.8 +/- 1.2 hr, p = 0.0001), and decreased with case number (mean decrease 1.00 +/- 0.19 min/case, p = 0.04). Operative time also varied between institutions (p = 0.001). Rate of learning (decrease in time per case) varied significantly between institutions only for MVP (p = 0.03). Similar analysis showed that pump time and clamp times did not significantly change over time (p > 0.17) but varied significantly between institutions. Institutional volume did not affect operative, pump, or clamp times or rate of learning (decrease in operative time/case). CONCLUSIONS: These prospective registry data demonstrate that, for port-access valve procedures, procedure times continue to improve (learning) even after 100 cases. Procedure time and learning are affected by institutional differences and by the type of procedure, but are little affected by institutional volume. This data provides a model to understand learning of new surgical procedures, and this data suggests that port-access valve procedures can be mastered by a variety of institutions.

Predictors of outcome in a multicenter port-access valve registry.

BACKGROUND: The aim of this study was to examine the predictors of outcome in patients undergoing isolated valve operation using port-access techniques. METHODS: Logistic regression analysis was performed in a prospective, multi-institutional registry of patients undergoing isolated aortic valve replacement (AVR, n = 252), mitral repair (MVP, n = 491), or mitral replacement (MVR, n = 568) using port-access techniques from 1997 to 1999. RESULTS: Endoaortic balloon occlusion was used in 2% (AVR), 93% (MVP), and 90% (MVR) of cases. Conversion to full sternotomy occurred in 3.8% of all cases. For all patients, early mortality was 50 of 1,311 (3.8%) and onset of new atrial fibrillation occurred in 140 of 1,311 (11%) patients. The determinants of 30-day mortality were redo, age, and MVR or AVR. The determinants of reoperation for bleeding were age, reoperation, and MVR. Age was a predictor for stroke, and age and low or medium volume center were predictors of new atrial fibrillation. CONCLUSIONS: Excellent short-term results can be obtained using port-access techniques in isolated mitral or aortic valve operations. Patient outcome is not related to institutional case volume, and the primary determinants of outcome after port-access valve procedures are generally patient-related factors.

Determinants of operative mortality in reoperative coronary artery bypass grafting.

Previously suggested risk factors for operative mortality in reoperative coronary artery bypass grafting are contradictory. Therefore, we analyzed our data of 622 patients who underwent reoperative bypass grafting from January 1986 through June 1993. Among these patients, 258 had saphenous vein grafts alone and 364 had internal mammary artery grafting, including unilateral (342 patients) and bilateral (22 patients) mammary artery grafting with or without additional saphenous vein grafting. Overall operative mortality was 11.4% for reoperation compared with only 3.6% for primary bypass grafting during the same time frame. To determine risk factors for mortality and the influence of internal mammary artery grafting on the outcome, we analyzed 82 variables (31 preoperative, 17 intraoperative, and 34 postoperative) by univariate analysis. Significant variables or the variables having a trend (p < 0.2) to be associated with the mortality were included in stepwise multiple logistic regression analyses. Two regression analyses were separately performed. Regression 1 only included preoperative and intraoperative variables whereas regression 2 included postoperative variables as well. The logistic regressions demonstrate that preoperative variables (low ejection fraction [p = 0.0002], old age [p = 0.003], female gender [p = 0.011], and history of arrhythmia [p = 0.023]), intraoperative variables (emergency operation [p = 0.0001] and long perfusion time [p = 0.0001]), and postoperative variables (complications) are independently associated with higher mortality. Unlike previously described results, aortic crossclamp time, route of cardioplegia, use of internal mammary artery, number of grafts, and year of operation are not associated with operative mortality. The identification of these risk factors may have important implications in further improvement of the results of reoperative coronary artery bypass grafting.

Functional comparison between the human inferior epigastric artery and internal mammary artery. Similarities and differences.

Although the inferior epigastric artery has been used as an alternative arterial graft for coronary artery bypass grafting, little is known about the contractile and relaxation characteristics of this artery. This study was designed to compare the pharmacologic reactivity of the two arterial conduits--the inferior epigastric artery and the internal mammary artery. Forty-one inferior epigastric artery ring segments from eight patients undergoing coronary grafting and 62 internal mammary artery ring segments were set up in organ baths under physiologic pressure. The contractility was determined from the contraction induced by the depolarizing agent potassium and receptor-mediated vasoconstrictor agents, norepinephrine, U46619, and endothelin-1. Endothelium-dependent relaxation was induced by the calcium ionophore A23187, a non-receptor agonist for endothelium-derived relaxing factor, and acetylcholine, a receptor agonist for endothelium-derived relaxing factor. Glyceryl trinitrate was used to study endothelium-independent relaxation. The maximal response (either contraction or relaxation) and the effective concentration causing 50% of the maximal response for these two arteries were compared. There was no difference (p > 0.05) either in the maximal contraction force (5.30 +/- 0.87 versus 4.76 +/- 0.89 gm for potassium, 5.13 +/- 0.67 versus 4.47 +/- 1.15 gm for norepinephrine, 8.04 +/- 1.23 versus 6.23 +/- 0.99 gm for U46619, and 4.88 +/- 0.69 versus 5.57 +/- 0.93 for endothelin-1 (n = 6 to 10 for each vasoconstrictor) or in the maximal relaxation induced by glyceryl trinitrate (86.46% versus 92.98%, n = 6) or by acetylcholine (20.72% versus 45.51%, n = 5) between the inferior epigastric artery and internal mammary artery. The effective concentration causing half maximal response to all vasoconstrictors and vasodilators was similar between the two arteries (p > 0.05). However, A23187 induced significantly less relaxation in the inferior epigastric artery (38.42 +/- 15.49%, n = 6) than in the internal mammary artery (71.89 +/- 7.17%, n = 9, p < 0.05). We conclude that contractility, endothelium-independent relaxation, and receptor-mediated endothelium-dependent relaxation are similar in the inferior epigastric artery and the internal mammary artery. However, the endothelium of this arterial graft has less ability to respond to the non-receptor-mediated endothelium-derived relaxing factor stimulant. The influence of this difference on the prevalence of atherosclerosis and long-term patency rate in the inferior epigastric artery remains to be studied.

Interaction between endothelin and vasodilators in the human internal mammary artery.

1. The internal mammary artery (IMA) is the primary choice as an arterial graft for coronary artery bypass surgery. Endothelin (ET) has been recently measured with an increased release after cardiopulmonary bypass for coronary artery bypass grafting. Threshold concentrations of ET-1 have been found to amplify specifically contractions induced by noradrenaline and serotonin. This study was designed to investigate the effect of glyceryl trinitrate (GTN) and calcium antagonists on ET-1 contraction in the human IMA. 2. Human IMA segments taken from 21 patients undergoing IMA-coronary artery bypass grafting were mounted in an organ bath under the physiological pressure determined from their own length-tension curves. Four ring segments were allocated into four groups. One served as a control and the others were treated with GTN (10, 100 nM, or 30 microM) for 5 min or nifedipine (20 or 200 nM, or 30 microM) for 25 min before concentration-contraction curves to ET-1 were established. In separate experiments, the concentration-relaxation curves to GTN or nifedipine were established in the IMA rings precontracted with ET-1 (10 nM). 3. Pretreatment of IMA with GTN for 5 min did not alter the ET-1-induced contraction. Pretreatment with 20 or 200 nM of nifedipine slightly but not significantly, altered the maximum contraction induced by ET-1. Higher concentrations (30 microM) significantly reduced the maximum contraction force (P = 0.008). On the other hand, GTN caused 76.44 +/- 6.35% relaxation in ET-1-precontracted IMA. In contrast, the nifedipine-induced relaxation was difficult to establish due to unsustained contraction to ET-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Middle and proximal sections of the human internal mammary artery are not "passive conduits".

Recent studies have shown that blood flow through the internal mammary artery graft is inadequate for maximal exercise and that hypoperfusion may be worsened by high-dose vasopressor therapy that could further reduce arterial graft flow. Histologic studies have suggested that the human internal mammary artery is an elastic "passive conduit" along the majority of its length. However, although the pharmacologic reactivity at the distal section of the internal mammary artery has been extensively studied, this evaluation has never been done at the middle and proximal sections. It is extremely important to understand the contractility at the midsection of the internal mammary artery because, in a critical situation, any contraction may further reduce the internal mammary artery flow. The present study was designed to investigate the following: (1) Is it true that the pharmacologic reactivity of the human internal mammary artery is different among various sections? and (2) Is the human internal mammary artery a nonreactive "passive conduit" at its most important area used as the graft--the middle and the proximal sections? One hundred six human internal mammary artery ring segments taken from patients who underwent internal mammary artery grafting procedures (29 from the proximal, 38 from the middle, and 39 from the distal sections) were studied in the organ bath under a physiologic pressure. Concentration-response curves were established for norepinephrine, endothelin-1, U46619, potassium, and glyceryl trinitrate (precontracted with 10 nmol/L U46619). Contraction forces were standardized (in grams per millimeter circumference) at a pressure of 100 mm Hg. The contraction force was greater in the distal section than in other sections for norepinephrine (p = 0.002) and endothelin-1 (p = 0.04). No differences were seen for potassium, U46619, or glyceryl trinitrate, whereas the effective concentration inducing 50% of maximal response for U46619 was 100-fold lower in the distal than in the middle section (9.06 +/- 0.34 versus 7.06 +/- 0.48 -log M; p = 0.01) indicating higher sensitivity in the distal section. This study for the first time shows various reactivity along the full length of the human internal mammary artery and shows that the distal section is the most reactive part of the graft. However, although the middle and the proximal sections are less reactive to some vasoconstrictors (norepinephrine and endothelin-1), it is not a "passive conduit" and it contracts with all four vasoconstrictors tested.(ABSTRACT TRUNCATED AT 400 WORDS)

Greater contractility of internal mammary artery bifurcation: possible cause of low patency rates.

Coronary artery bypass grafting using bifurcation of the internal mammary artery (IMA) has been reported to have a poor patency rate. To test the hypothesis that the contractility (tendency for spasm) is greater at the bifurcation than at the main IMA, segments of the bifurcation and the distal section of IMA taken from patients with coronary artery bypass grafts were studied in organ baths. The IMA rings were set up at a physiologic pressure. Concentration-response curves were established for norepinephrine, endothelin-1, U46619, potassium, and glyceryl trinitrate (precontracted with 10 nmol/L U46619). Contraction forces were standardized (gram per mm circumference) at a pressure of 100 mm Hg. The diameter was 1.50 +/- 0.08 mm (n = 38) for the bifurcation and 2.03 +/- 0.07 (n = 42) for the main IMA (p < 0.0001). The standardized contraction force was greater in the bifurcation than in the main IMA for norepinephrine (0.82 +/- 0.06 versus 0.54 +/- 0.1; p = 0.02) and endothelin-1 (1.07 +/- 0.11 versus 0.69 +/- 0.07; p = 0.02). No differences were seen for potassium, U46619, or glyceryl trinitrate, whereas the effective concentration that induced 50% of maximal effect for U46619 was 6.17-fold lower in the bifurcation than in the main IMA (9.14 +/- 0.28 versus 8.35 +/- 0.09 -log M; p = 0.003), indicating higher sensitivity in the bifurcation.(ABSTRACT TRUNCATED AT 250 WORDS)

Determinants of operative mortality in elderly patients undergoing coronary artery bypass grafting. Emphasis on the influence of internal mammary artery grafting on mortality and morbidity.

Coronary artery bypass grafting has been performed for elderly patients (> or = 70 years) with increasing frequency. From January 1986 through June 1993, 1399 elderly patients underwent isolated coronary bypass grafting. Of these patients, 823 had saphenous vein grafts alone and 576 had internal mammary artery grafting, including unilateral (n = 546) and bilateral (n = 28). Overall operative mortality was 8.86%. Operative mortality for unilateral internal mammary artery grafting (6.41%) was lower than for saphenous vein grafting only (9.96%, p = 0.021) and bilateral internal mammary artery grafting (21.43%, 6/28, p = 0.018). Fewer patients undergoing internal mammary artery grafting had postoperative complications (low cardiac output, intraaortic balloon pumping, and neurologic complications) than patients having saphenous vein grafting only. To determine risk factors for mortality and the influence of internal mammary artery grafting on the outcome, we analyzed 55 variables (27 preoperative, 15 intraoperative, and 13 postoperative) by univariate analysis. Significant variables (age, gender, height, weight, surface area, diabetes, obesity, body mass index, history of congestive heart failure, myocardial infarction, or arrhythmia, functional class, left ventricular ejection fraction, stenosis of the left anterior descending or right coronary artery, emergency operation, reoperation, number of grafts, perfusion time, and bilateral or right internal mammary artery grafting) were included in a stepwise multiple logistic regression analysis. The logistic regression demonstrates that those preoperative (history of congestive heart failure or myocardial infarction, low ejection fraction, female gender, and old age), intraoperative (long cardiopulmonary bypass time, emergency operation, reoperation, and use of right internal mammary artery grafting), and postoperative (postoperative complications) variables are independently associated with higher mortality. This study reveals the high-risk groups in elderly patients undergoing coronary bypass and suggests that a left internal mammary artery graft in combination with saphenous vein grafting may achieve a lower operative mortality and morbidity than other procedures in selected elderly patients undergoing coronary artery bypass grafting.

Risk factors for operative mortality in elderly patients undergoing internal mammary artery grafting.

From January 1986 through June 1992, 512 elderly patients (70 years and older) underwent internal mammary artery grafting (IMAG). The operative mortality in these patients was 7.62% (39 of 512), which was significantly higher than that (1.97% [60 of 3,047]; p < 0.0001) in younger patients (under 70 years old). To investigate the risk factors in the elderly, the data from the 512 patients were evaluated by univariate analysis and multiple logistic regression. Of 53 variables analyzed, nine preoperative variables (age, smoking history, congestive heart failure, myocardial infarction, New York Heart Association functional class, ejection fraction, left main artery disease, stenosis of the left anterior descending artery, and reoperation), three intraoperative variables (emergency operation, bilateral IMAG, and right IMAG), and nine postoperative variables were significantly associated with the higher mortality (p < 0.05). In particular, the operative mortality was significantly higher in the patients undergoing right IMAG (21.62% [8 of 37]) than that in patients only undergoing left IMAG (6.53% [31 of 475]; p < 0.004). The significant preoperative and intraoperative variables and the variables that have a tendency for correlation (p < 0.2) to mortality were included in a stepwise multiple logistic regression. The regression analysis demonstrated that right IMAG, reoperation, history of myocardial infarction, age, left main artery disease, history of smoking, and postoperative complications are the risk factors for the elderly undergoing IMAG. Therefore, particular care should be taken in those patients scheduled to undergo IMAG. The role of right IMAG in the elderly should be further clarified before universal acceptance of the technique in these patients.

Aortic valve replacement: determinants of operative mortality.

Contradictory results have been reported regarding risk factors for aortic valve replacement (AVR). This study was designed to investigate determinants of operative mortality for AVR with emphasis on concomitant coronary artery bypass grafting (CABG) and old age. Between January 1986 and June 1992, 371 patients with a mean age of 61.99 +/- 0.76 years underwent AVR. There were 256 men (69.0%) and 115 women (31.0%). Twenty-six patients (7.0%) were 80 years old or older, and 97 (26.1%) were between 70 and 80 years old. Of these patients, 210 (56.6%) had isolated AVR, 142 (38.3%) had concomitant CABG, and 31 (8.4%) had concomitant mitral valve operations. Twenty patients (5.4%) underwent emergency operation. There were 33 operative deaths (8.9%). Univariate analysis and stepwise multiple logistic regression analysis were used to determine the risk factors for operative mortality. In the univariate analysis, 13 preoperative variables (sex, age, history of congestive heart failure, myocardial infarction, arrhythmia, functional class, class I/II versus III/IV, four variables related to aortic valve pathology, ejection fraction, left ventricular function) and 20 perioperative variables (emergency operation, individual surgeon, myocardial protection by type and route of cardioplegia, type of prosthesis, size of prosthesis, mean size by survival, small versus large size, concomitant procedure, concomitant CABG (versus others or AVR alone), concomitant mitral valve operation (versus others or AVR alone), concomitant CABG and MV operation, aortic cross-clamp time, cardiopulmonary bypass time, use and time of insertion of intraaortic balloon pump, low cardiac output, postoperative complications) were examined.(ABSTRACT TRUNCATED AT 250 WORDS)

Simplified placement of a silicone tracheal Y stent.

Current methods of insertion of silicone tracheal Y stents can be technically challenging. A simplified method of carinal stent insertion is presented. This method is easy to learn and takes only a few seconds to accomplish.

Inhibitory effects of calcium antagonists on alpha-adrenoceptor-mediated contraction in the human internal mammary artery.

1. The internal mammary artery has become a preferred coronary bypass graft. Sympathomimetic amines are spasmogens for vasospasm and calcium antagonists are frequently administered drugs perioperatively. The effect of calcium antagonists on alpha-adrenoceptor-mediated contraction depends on the subtype of alpha-adrenoceptor and the type of origin of vascular smooth muscle. This study was designed to investigate the effect of calcium antagonists on alpha-adrenoceptor-mediated contraction in the IMA. 2. Human IMA segments taken from 22 patients undergoing IMA--coronary artery bypass grafting were mounted in an organ bath under the physiological pressure determined from their own length-tension curves. 3. Three ring segments were allocated into three groups. One served as a control and the others were treated with clinically related concentrations of nifedipine (20 or 200 nM) for 25 min before concentration-contraction curves to alpha 1-adrenoceptor agonist methoxamine (MO) or full alpha-adrenoceptor agonist noradrenaline (NA) were established. 4. In separate experiments, the concentration-relaxation curves to nifedipine were established in the IMA rings precontracted with MO (30 microM) or NA (10 microM). Glyceryl trinitrate (GTN, 3 microM) was added to further relax the vessels. 5. Pretreatment with nifedipine (200 nM) only slightly inhibited the MO- (1.74 +/- 0.32 vs 2.88 +/- 0.56 g) or NA- (2.43 +/- 0.66 vs 3.60 +/- 0.82 g) induced contraction without statistical significance (P > 0.05). 6. On the other hand, nifedipine only caused 34.49% relaxation in the MO-precontracted and 24.39% relaxation in the NA-precontracted IMAs. In contrast, GTN caused 76.16% (against MO, P < 0.05) or 92.22% (against NA, P < 0.0001) relaxation.(ABSTRACT TRUNCATED AT 250 WORDS)

Risk factors for operative mortality and sternal wound infection in bilateral internal mammary artery grafting.

To investigate risk factors for operative mortality and sternal infection in patients undergoing bilateral internal mammary artery grafting, we analyzed the data of 199 patients who underwent this procedure from January 1986 through June 1992. These patients were also compared with those who underwent only saphenous vein grafting (1664 cases) and those who underwent unilateral internal mammary artery grafting (3359 cases) during the same time frame. The operative mortality was 3.52% (7/199) in the patients having bilateral internal mammary artery grafting, 2.71% (91/3359) in those having unilateral internal mammary artery grafting, and 8.53% (142/1664) in the patients having saphenous vein grafting (p < 0.0001). The occurrence rate of sternal infections was 2.45% (5/199) for bilateral internal mammary artery grafting, 1.32% (13/1664) for saphenous vein grafting, and 1.19% (20/3359) for unilateral internal mammary artery grafting (p = 0.27). The univariate analysis revealed that age, history of congestive heart failure, emergency operation, ejection fraction, and aortic crossclamp time were significantly correlated with operative mortality and that obesity was correlated with sternal wound infection. Stepwise multiple logistic regression identified that old age (> or = 70 years) (p < 0.0001), long perfusion time (p < 0.0001), and emergency operation (p = 0.0004) are risk factors for operative mortality and that obesity (p = 0.0009) is the only significant risk factor for sternal wound infection. We conclude that bilateral internal mammary artery grafting does not increase operative mortality in properly selected patients. However, this procedure should be carefully chosen in elderly (> or = 70 years) patients and for emergency operation. Obese patients have a high risk for sternal infection after bilateral internal mammary artery grafting.

Implantable cardioverter defibrillator: the role of thoracoscopy.

Video techniques have been used in many centers to assist with pericardial patch placement for implantable defibrillators. Although there are some specific instances where this technique would be helpful, the success of the transvenous systems will limit the application of this approach.

Thoracoscopic transdiaphragmatic approach for adrenal biopsy.

The role of thoracoscopy for the management of intrathoracic diseases has expanded with advancement in endoscopic instrumentation and technology. We report a case of thoracoscopic transdiaphragmatic biopsy of an adrenal gland for metastatic carcinoma. The procedure was uncomplicated and the patient was discharged on the second postoperative day. The morbidity of traditional approaches for adrenal operation was avoided. Thoracoscopy may be a useful approach in selected patients for adrenal operation.

Present role of thoracoscopy in the diagnosis and treatment of diseases of the chest.

Since thoracoscopy was originally described in 1910, the application has been limited mainly to the diagnosis and treatment of pleural disease. Recent advancements in endoscopic equipment and refinement of surgical techniques have expanded the application of this procedure. Using video thoracoscopic techniques in 70 patients over the past 9 months, we have been able to perform a variety of procedures previously accomplished by "open" techniques. These procedures include (1) wedge resections of pulmonary nodules in 21 patients, using endoscopic mechanical stapling devices; (2) excision of the pericardium and drainage of the pericardial space in 6 patients; (3) dorsal thoracic sympathectomy in 6 patients; (4) apical blebectomy and pleurodesis in 6 patients; (5) lung biopsies for diagnosis of diffuse lung disease in 5 patients. Additional procedures performed include biopsy of hilar masses (3), biopsy of esophageal mass, excision of a mediastinal cyst, and the drainage of a spinal abscess. The remaining 20 procedures were performed for the diagnosis and treatment of pleural disease. There was no mortality associated with the procedure and morbidity was lessened, compared with standard thoracotomy procedures. The postoperative hospital stay after elective procedures performed in well patients averaged 3 days and was often as short as 1 day. Our experience indicates a markedly expanded role for thoracoscopy in the diagnosis and treatment of thoracic diseases with less postoperative morbidity.