Neutron Activation Analysis of Nitrogen in Feedstuffs

The application of neutron activation analysis to the determination of nitrogen in various feeds and feedstuffs has been investigated. Samples were bombarded with fast neutrons to induce the 14N(n, 2n)13N reaction. 13N is a positron emitter with a 10 min half-life. The positrons annihilate in or near the sample to produce 0.51 MeV gamma rays, which are then counted in a detector system. Phosphorus and silicon interfere and are compensated for in the technique. A total of 419 individual runs were made on 53 samples covering 16 different types of materials. Total analysis time was 15 min per sample with a production rate of 12 samples per hr. The coefficient of variation of runs by the automated method typically ranged from 0.90 to 1.73 on the different sample groups. A good correlation between protein determined by the Kjeldahl technique and that determined by the automated method was demonstrated.

Biomechanical approaches applied to the lower and upper limb for the measurement of spasticity: A systematic review of the literature

PURPOSE

To review and characterise biomechanical approaches for the measurement of spasticity as one component of the upper motor neurone syndrome.

METHOD

Systematic literature searches based on defined constructs and a four-step review process of approaches used or described to measure spasticity, its association with function or associated phenomena. Most approaches were limited to individual joints and therefore, to reflect this trend, references were grouped according to which body joint(s) were investigated or whether it addressed a functional activity. For each joint, references were further sub-divided into the types of measurement method described.

RESULTS

A database of 335 references was established for the review process. The knee, ankle and elbow joints were the most popular, perhaps reflecting the assumption that they are mono-planar in movement and therefore simpler to assess. Seven measurement methods were identified: five involving passive movement (manual, controlled displacement, controlled torque, gravitational and tendon tap) and two involving active movement (voluntary and functional). Generally, the equipment described was in an experimental stage and there was a lack of information on system properties, such as accuracy or reliability. Patient testing was either by cohort or case studies. The review also conveyed the myriad of interpretations of the concept of spasticity.

CONCLUSIONS

Though biomechanical approaches provide quantitative data, the review highlighted several limitations that have prevented them being established as an appropriate method for clinical application to measure spasticity.

A microcontroller system for investigating the catch effect: functional electrical stimulation of the common peroneal nerve

Correction of drop foot in hemiplegic gait is achieved by electrical stimulation of the common peroneal nerve with a series of pulses at a fixed frequency. However, during normal gait, the electromyographic signals from the tibialis anterior muscle indicate that muscle force is not constant but varies during the swing phase. The application of double pulses for the correction of drop foot may enhance the gait by generating greater torque at the ankle and thereby increase the efficiency of the stimulation with reduced fatigue. A flexible controller has been designed around the Odstock Drop Foot Stimulator to deliver different profiles of pulses implementing doublets and optimum series. A peripheral interface controller (PIC) microcontroller with some external circuits has been designed and tested to accommodate six profiles. Preliminary results of the measurements from a normal subject seated in a multi-moment chair (an isometric torque measurement device) indicate that profiles containing doublets and optimum spaced pulses look favourable for clinical use.

Theoretical and methodological considerations in the measurement of spasticity

PURPOSE

To discuss the measurement of spasticity in the clinical and research environments, make recommendations based on the SPASM reviews of biomechanical, neurophysiological and clinical methods of measuring spasticity and indicate future developments of measurement tools.

METHOD

Using the results of the systematic reviews of the biomechanical, neurophysiological and clinical approaches, methods were evaluated across three dimensions: (1) validity, reliability and sensitivity to change; (2) practical quality such as ease of use and (3) qualities specific to the measurement of spasticity, for example ability to be applied to different muscle groups. Methods were considered in terms of applicability to research and clinical applications.

RESULTS

A hierarchy of measurement approaches was identified from highly controlled and more objective (but unrelated to function) to ecologically valid, but less objective and subject to contamination from other variables. The lack of a precise definition of spasticity may account for the problem of developing a valid, reliable and sensitive method of measurement. The reviews have identified that some tests measure spasticity per se, some phenomena associated with spasticity or consequential to it and others the effect of spasticity on activity and participation and independence.

CONCLUSIONS

Methods appropriate for use in research, particularly into the mechanism of spasticity did not satisfy the needs of the clinician and the need for an objective but clinically applicable tool was identified. A clinical assessment may need to generate more than one 'value' and should include evaluation of other components of the upper motor neurone syndrome. There is therefore a need for standardized protocols for 'best practice' in application of spasticity measurement tools and scales.

Recruitment by motor nerve root stimulators: significance for implant design

Three paraplegics have been implanted with stimulators of the lumbar anterior roots. Twelve roots were trapped in slots, each with three electrodes, a central cathode and two anodes, but the anodes in all the slots were connected together to reduce the number of wires. Cross-talk between roots was observed at lower levels than expected. Cross-talk was assessed from the ratio of the root's threshold to the threshold of the contralateral response (expected ratio: 72). Two hypothetical reasons for this low ratio were: that the cathode current was not equally shared by the anodes; or that the contralateral responses were reflex. Experiments showed that neither explanation was valid. The ratio of the contralateral to ipsilateral threshold for individual slots (K(1)) was sometimes low because the ipsilateral threshold was high. By taking the ratio of the lowest contralateral response to lowest ipsilateral response, for all roots in each subject (K(2)), the ratio should approach the theoretical value. However, for the two subjects with small slots, it was 7.9 and 15.3, much less than 72, suggesting that the original theory was incorrect. Approximate calculations of the activation function suggest that the reason may be that roots which run close to a slot, but not through it, may pass through a virtual anode region outside the ends of the slots, and that anodal break stimulation in those regions causes the cross-talk. Our estimate is that this cross-talk would be expected to occur at intensities above 5.3 times the cathodal threshold. If the roots are stimulated in pairs, below the levels of cross-talk, experimental results show that the moments obtained in response are additive to within 5%.

Reversible left ventricular dysfunction simulating a myocardial infarction after pericardiectomy

A 39 year old man with postoperative constrictive pericarditis after pericardiectomy developed major left ventricular systolic dysfunction with an anterior wall infarct pattern on ECG but no regional wall motion abnormalities by echocardiography or serum enzymatic evidence of a myocardial infarction. The left ventricular dysfunction resolved over two weeks with supportive treatment. It is postulated that this patient's transient left ventricular dysfunction and ECG changes were caused by myocardial inflammation and oedema induced by operative trauma during pericardiectomy.

Bronchoscopic preparation for airway resection

In patients being considered for tracheobronchial resection and reconstruction, therapeutic bronchoscopy provides a necessary and complementary role to airway resection. Surgeons involved in tracheobronchial reconstruction need to be adept at airway interventions with the flexible and the rigid bronchoscopes. Bronchoscopy is an important part of the evaluation, stabilization, and preparation of the airway before tracheobronchial resection. Therapeutic bronchoscopy also provides the most common alternative to airway resection so that familiarity with the techniques of therapeutic bronchoscopy is important as the surgeon considers the advantages of definitive versus palliative airway management. Furthermore, postoperative complications of tracheobronchial surgery may require therapeutic endoscopic interventions to optimize outcomes after tracheobronchial resection and reconstruction. In patients being considered for airway resection, bronchoscopy provides the most direct assessment for a tissue diagnosis and measurement of the extent of the lesion and its relation to airway landmarks and an assessment of the quality of the airway being considered for anastomosis. Patients who have critical airway stenosis and impending obstruction can be temporized by bronchoscopic dilatation or core out of endoluminal tumor. Bronchoscopic dilatation or core out allows stabilization of the patient, completion of the assessment for surgical resectability, and performance of an elective rather than an emergent surgical resection. By relieving airway obstruction, therapeutic bronchoscopy also can improve the assessment of tumor margins and allow for clearing of an obstructive pneumonia so that postoperative pulmonary and anastomotic complications are minimized. Airway resection remains the preferred definitive approach for benign and malignant airway pathologies, but therapeutic bronchoscopy provides a useful adjunct to surgery in assessing the patient for surgical resection, preparing the patient for surgery, and optimizing postoperative results.

Airway stenting

Various airway pathologies may result in central airway obstruction. For patients who have benign and malignant disease, definitive surgical correction by tracheobronchial resection and reconstruction is preferred. Numerous patients, however, have unresectable airway lesions owing to the extent of disease or to medical or surgical contraindications. These patients can be palliated by several endoscopic strategies, including dilatation, core out of tumor, laser resection, endobronchial brachytherapy, or photodynamic therapy. Airway stenting with silicone or expandable metal stents provides reliable and durable palliation in 80% to 95% of properly selected patients. The major advantages of silicone stents are the ease of customization, repositioning, and removal, with the major drawbacks being stent migration or stent obstruction. Expandable metal stents have the advantage of ease of insertion, conformation to the airway, low inner-to-outer diameter ratio, and stent stability. These advantages, however, are offset by (1) the development of tumor ingrowth or of granulation at the end of the stent or through the interstices of the stent and (2) the difficulty or impossibility of stent repositioning or removal once it has been seated completely within the airway. Management of the patient who has central airway obstruction requires a thorough knowledge and consideration of the surgical and endoscopic management options and, usually, a multidisciplinary approach, with experienced thoracic surgical consultation to evaluate the potential for definitive surgical correction. The interventional bronchoscopist must consider the spectrum of endoscopic therapeutics fully. Most patients benefit from combining strategies in a flexible algorithm directed at optimizing patient outcomes. The benefits and risks of airway stenting must be considered in comparison with the other options for airway palliation. In refractory strictures, rapidly recurrent tumor, or extrinsic compression, endobronchial stenting likely will be necessary to achieve durable palliation of airway obstruction. The short- and long-term implications of airway stenting, including the complications of silicone versus expandable metal stents, should be considered thoroughly, while the physician bases treatment or procedure decisions on individual patient anatomy and expected natural history.

Indices to describe different muscle activation patterns, identified during treadmill walking, in people with spastic drop-foot

This study was concerned with individuals who were unable to effectively dorsiflex their ankle when walking, as a result of a lesion of the central nervous system (CNS). Indices that categorise and quantify different patterns of calf and anterior tibial muscle activation patterns during treadmill walking have been derived from a sample of fifteen individuals with established hemiplegia following stroke and twelve age-matched individuals without impairment. As subjects walked on a treadmill, force sensitive foot-switches under the heel and first metatarsal head allowed EMG signals from the calf and anterior tibial muscles to be related to phases of the gait cycle. Normal activation periods for each muscle group were identified as percentiles of the gait cycle and indices for muscle activation periods were derived using ratios of integrated EMG during selected periods. Indices were derived that identified statistically significant differences, between normal and hemiplegic subjects, in calf activation during both push-off phase (P<0.001) and early stance phase (P<001), but not activation of tibialis anterior during swing (P=0.325) Observation suggested that integrated tibialis anterior activity during swing phase in hemiplegic subjects was not dissimilar to normal subjects, but the profile in hemiplegic subjects tended to lack the normal second peak of activity at initial foot contact. The reasons for drop-foot were shown to be varied and complex. The indices defined may be useful for directing therapy and measuring outcome.

Total esophageal reconstruction using a tubed parascapular free flap

A method for total esophageal reconstruction when intestinal options are no longer available is presented. The technique described utilizes the parascapular microsurgical free flap, which is tubed and interposed between the cervical esophagus and the gastric remnant in the abdomen. The technique involves a well-recognized microsurgical flap and may be added to the armamentarium for total esophageal reconstruction.

Underestimation of mortality following lung volume reduction surgery resulting from incomplete follow-up

STUDY OBJECTIVES

Incomplete follow-up can bias interpretation of data that are collected in longitudinal studies. We noted that many patients failed to return for follow-up in a study of effect of lung volume reduction surgery (LVRS) on quality of life (QOL). Accordingly, we designed this investigation to determine the reasons patients dropped out, and to assess differences between those who continued in the study (attendees) and those who did not (nonattendees).

DESIGN

Telephone survey.

SUBJECTS

Patients with advanced emphysema who had undergone LVRS and had previously agreed to participate in a longitudinal QOL study.

RESULTS

No differences were found with regard to age, gender, preoperative pulmonary function, or oxygen use between attendees and nonattendees. Long-term mortality in nonattendees (27%) was considerably greater than that seen in attendees (3%, p < 0.05). Distance from the hospital, financial burden, and living out of the region were the most common reasons cited by surviving nonattendees for their failure to return for follow-up.

CONCLUSIONS

Studies reporting the long-term mortality after LVRS can be biased in the direction of underestimating the true value if they are compromised by incomplete follow-up.

Economic analysis of lung volume reduction surgery as part of the National Emphysema Treatment Trial. NETT Research Group

BACKGROUND

In today's cost-conscious health care environment, obtaining timely and accurate economic information regarding new medical technologies has become extremely important. The National Emphysema Treatment Trial, a multicenter, randomized controlled trial of lung volume reduction surgery (LVRS) plus medical therapy, versus medical therapy for patients with severe emphysema, includes a parallel cost-effectiveness analysis.

METHODS

The analysis is designed to determine the cost-effectiveness of LVRS versus medical therapy for those who are eligible for the procedure. After describing theoretical foundations of cost-effectiveness analysis as they apply to this study, we describe the economic and quality of life data that are being collected alongside the clinical trial, methods of analysis, and approach to presenting the results.

RESULTS

The cost-effectiveness of LVRS relative to medical therapy will be presented as costs per quality-adjusted life years gained.

CONCLUSIONS

This analysis will provide timely economic data that can be considered alongside the clinical results of the National Emphysema Treatment Trial. As one of the largest clinical trials to include a parallel, prospective cost-effectiveness analyses, this study will also provide valuable practical information about conducting an economic analysis alongside a multicenter clinical trial.

XAFS studies of the formation of cobalt silicide on (square root of 3 x square root of 3) SiC(0001)

Thin Co films (1-8 nm) were directly, sequentially, and co-deposited with Si (3.6-29.2 nm) on the (square root of 3 x square root of 3)-R30 degrees reconstruction of 6H-SiC(0001). The films were annealed over a temperature range of 823-1373K and investigated with XAFS, XPS, AES and AFM. After annealing up to 1373K directly deposited Co films do not transform entirely to cobalt disilicide and C segregation is observed on the surface of the films. On the other hand, sequentially and co-deposited films do form cobalt disilicide after annealing at 823K, but also show islanding after annealing at 923K.

Results from bone mineral density scans in twenty-two complete lesion paraplegics

STUDY DESIGN

The bone mineral density (BMD) in 22 male subjects with complete lesion paraplegia sustained 1.8 to 27 years previously was measured. The measurements were used in screening each subject for a research programme investigating the restoration of standing using functional electrical stimulation (FES).

OBJECTIVES

To assess the extent of bone loss in this group of subjects and correlation to age, time post-injury and level of lesion.

SETTING

District General Hospital in the UK.

METHODS

BMD was measured by dual energy X-ray absorptiometry (DEXA) in the lumbar spine and femoral neck and expressed as an indirect index to an age matched 'normal' population. Fracture risk was described from this score using published data indicating that the risk increased with each standard deviation difference from the 'normal' mean.

RESULTS

The bone density in the lumbar spine was better preserved than in the femoral neck. BMD in the lumbar spine was found to be greater than the mean from the age matched population in 57.1% of subjects. Bone loss at the femoral neck suggested that 81.8% of the subjects were at increased risk of fracture, but only 22.7% were at a high risk. No correlation was found between BMD at the lumbar spine or the femoral neck and age, lesion level or time post-injury.

CONCLUSION

The study indicates that further investigation into baseline BMD values for the SCI population is required to improve information provided to patients and assessment of fracture risk on an individual basis.

Projection neurons with shared cotransmitters elicit different motor patterns from the same neural circuit

Specificity in the actions of different modulatory neurons is often attributed to their having distinct cotransmitter complements. We are assessing the validity of this hypothesis with the stomatogastric nervous system of the crab Cancer borealis. In this nervous system, the stomatogastric ganglion (STG) contains a multifunctional network that generates the gastric mill and pyloric rhythms. Two identified projection neurons [modulatory proctolin neuron (MPN) and modulatory commissural neuron 1 (MCN1)] that innervate the STG and modulate these rhythms contain GABA and the pentapeptide proctolin, but only MCN1 contains Cancer borealis tachykinin-related peptide (CabTRP Ia). Selective activation of each projection neuron elicits different rhythms from the STG. MPN elicits only a pyloric rhythm, whereas MCN1 elicits a distinct pyloric rhythm as well as a gastric mill rhythm. We tested the degree to which CabTRP Ia distinguishes the actions of MCN1 and MPN. To this end, we used the tachykinin receptor antagonist Spantide I to eliminate the actions of CabTRP Ia. With Spantide I present, MCN1 no longer elicited the gastric mill rhythm and the resulting pyloric rhythm was changed. Although this rhythm was more similar to the MPN-elicited pyloric rhythm, these rhythms remained different. Thus, CabTRP Ia partially confers the differences in rhythm generation resulting from MPN versus MCN1 activation. This result suggests that different projection neurons may use the same cotransmitters differently to elicit distinct pyloric rhythms. It also supports the hypothesis that different projection neurons use a combination of strategies, including using distinct cotransmitter complements, to elicit different outputs from the same neuronal network.

FES cycling may promote recovery of leg function after incomplete spinal cord injury

STUDY DESIGN

Single subject pilot.

OBJECTIVES

(i) To see whether strength and endurance for recreational cycling by functional electrical stimulation (FES) are possible following spinal cord injury (SCI). (ii) To develop the equipment for FES-cycling.

SETTING

England.

METHODS

Near-isometric or cycling exercise was performed by the incomplete SCI subject at home.

RESULTS

After training for an average of 21 min per day for 16 months, the stimulated muscles increased in size and the subject was able to cycle for 12 km on the level. Surprisingly, there was a substantial increase in the measured voluntary strength of the knee extensors and the subject reports improved leg function.

CONCLUSION

FES-cycling may promote recovery after incomplete spinal cord injury. If so, it offers the possibility of being a convenient method for widespread use.

Lymphoproliferative disorders presenting as mediastinal neoplasms

Lymphoproliferative disorders may present in any organ of the body. The mediastinum is an uncommon location for presentation of these heterogeneous disorders, but involvement of the mediastinum may be the sole site of disease for several aggressive lymphomas. Both Hodgkin's disease and non-Hodgkin's lymphoma may present in the mediastinum. The most common types of non-Hodgkin's lymphoma involving the mediastinum include lymphoblastic lymphoma and mediastinal large cell lymphoma. These lymphomas most commonly develop in the anterior mediastinum but may be seen in the middle and posterior mediastinum. Symptoms associated with a mediastinal presentation of a lymphoproliferative disorder are often attributable to compression of mediastinal structures (eg, superior vena cava syndrome) or invasion of thoracic structures such as the pericardium or pleura. Although staging can be performed with routine imaging studies, surgical intervention is often required to ensure accurate histologic diagnosis of these lymphomas. Once a diagnosis has been established, therapeutic modalities usually include chemotherapy and/or radiotherapy.

Mediastinal germ cell tumors

Mediastinal germ cell tumors are uncommon tumors that occur predominantly within the anterior mediastinum and frequently present as a very large mass with local compression. Symptoms are typically vague and represent the local mass effects of the tumor. Chest computed tomography and examination of serum tumor markers provide the critical workup before a tissue diagnosis is obtained. Seminomas are extremely sensitive to both chemotherapy and radiation and are primarily treated nonsurgically. Benign teratomas without malignant elements are extremely resistant to both chemotherapy and radiation and are treated exclusively with surgical resection with excellent outcomes. Malignant nonseminomatous germ cell tumors are primarily treated with chemotherapy, with adjuvant surgery reserved for patients with residual mediastinal masses after systemic therapy.

Lung cancer proliferation correlates with [F-18]fluorodeoxyglucose uptake by positron emission tomography

Tumor proliferation has prognostic value in resected early-stage non-small cell lung cancer (NSCLC). We evaluated whether [F-18]fluorodeoxyglucose (FDG) uptake of NSCLC correlates with tumor proliferation and, thus, could noninvasively grade NSCLCs (refining patient prognosis and therapy). Thirty-nine patients with potentially resectable NSCLC underwent whole-body FDG positron emission tomography (PET) 45 min after i.v. injection of 10 mCi of FDG. Tumor FDG uptake was quantitated with the maximum pixel standardized uptake value (maxSUV). The lesion diameter from computed tomography was used to correct the maxSUV for partial volume effects using recovery coefficients determined for the General Electric Advance PET scanner. Thirty-eight patients underwent complete surgical staging (bronchoscopy and mediastinoscopy, with or without thoracotomy). One stage IV patient by PET underwent bronchoscopic biopsy only. Immunohistochemistry for Ki-67 (proliferation index marker) was performed on all of the 39 NSCLC specimens (35 resections, 1 percutaneous, and 3 surgical biopsies). The specimens were reviewed for cellular differentiation (poor, moderate, well) and tumor type. Lesions ranged from 0.7 to 6.1 cm. The correlation found between uncorrected maxSUV and lesion size (Rho, 0.56; P = 0.0006) disappeared when applying the recovery coefficients (Rho, -0.035; P = 0.83). Ki-67 expression (percentage of positive cells) correlated strongly with FDG uptake (corrected maxSUV: Rho, 0.73; P < 0.0001). The correlation was stronger for stage I lesions (11 stage IA, 15 stage IB): Rho, 0.79; P < 0.0001) and strongest in stage IB (Rho, 0.83; P = 0.0019). A significant association (P < 0.0001) between tumor differentiation and corrected SUV was noted. FDG PET may be used to noninvasively assess NSCLC proliferation in vivo, identifying rapidly growing NSCLCs with poor prognosis that could benefit from preoperative chemotherapy.

Cleavage of Bax enhances its cell death function

Members of the Bcl-2 family of proteins are key regulators of apoptosis. Some of these proteins undergo posttranslational modification, such as phosphorylation or proteolysis, that serves to alter their function. Caspases are known to cleave Bid, a proapoptotic family member, as well as Bcl-2 and Bcl-X(L), two prosurvival family members, which activate their cytotoxic activity resulting in the release of cytochrome c from mitochondria. Previously we showed that Bax was cleaved by calpain rather than by caspases from full-length 21 kDa to generate a cleavage fragment of 18 kDa. Since cleavage of Bid serves to activate its cytotoxic activity, we wanted to determine if the p18 form of Bax exhibited increased cytotoxicity compared to p21 Bax. Using a transient transfection system in human embryonic kidney 293T cells we show that the p18 form of Bax displays a more potent ability to induce cell death. The pancaspase inhibitor Z-VAD-fmk completely blocked apoptosis induced by p21 Bax but only partially inhibited apoptosis induced by p18 Bax. Cyclosporin A, an inhibitor of the mitochondrial permeability transition (PT) pore, had no effect on Bax-mediated apoptosis of 293T cells suggesting that apoptosis was independent of the PT. Thus cleavage of p21 Bax during apoptosis to the p18 form may serve to increase the intrinsic cytotoxic properties of this proapoptotic molecule and enhance its cell death function at the mitochondria.

Bronchoscopic management of central airway obstruction

OBJECTIVES

Patients with central airway obstruction are critically ill, with impending suffocation. They are seen with diverse anatomic and functional deficits caused by both benign and malignant obstructions. Such cases were reviewed to examine the indications, techniques, and outcomes of an algorithm approach to bronchoscopic management.

METHODS

Between July 1992 and April 1996, 97 patients underwent bronchoscopic procedures for the management of central airway obstruction, and their cases were used for a retrospective review of the airway management.

RESULTS

There were 48 male and 49 female patients, aged 13 to 85 years. There were 48 benign and 49 malignant pathologic conditions that gave rise to 108 stenoses. These were treated with 199 endoscopic procedures with an average of 1.7 interventions per endoscopy, including mechanical core-out (62), dilation (135), laser ablation (44), placement of brachytherapy catheters (9), and stent placement (88). Diagnoses included lung cancer, primary tracheobronchial tumors, tumors metastatic to the airway or mediastinum, and a variety of benign obstructions. In the group of 97 patients there were 2 (2%) perioperative deaths and 34 (34%) late deaths, 29 in the malignant group and 5 in the benign group. Median survival was 7.6 months (range 1 week-31 months). There were 7 (7%) complications among the group of 97, 4 in the malignant group, and 3 in the benign group.

CONCLUSIONS

Endobronchial surgical techniques can be used safely and systematically for the relief of benign and malignant central airway obstructions; a diversity of approaches and interventions are required to produce and maintain palliation of airway symptoms.

Descending necrotizing mediastinitis: An analysis of the effects of serial surgical debridement on patient mortality

OBJECTIVES

Descending necrotizing mediastinitis is a polymicrobial infection originating in the oropharynx with previously reported mortality rates of 25% to 40%. This investigation reviews the effects of serial surgical drainage and debridement on the survival of patients with descending necrotizing mediastinitis.

METHODS

A retrospective review of patients from 1980 through 1998 with a diagnosis of descending necrotizing mediastinitis was performed. Their records were abstracted for personal demographics, hospital course, morbidity, and mortality. Also abstracted were all reports of patients with descending necrotizing mediastinitis published in English between 1970 and 1999.

RESULTS

We treated 10 patients in whom descending necrotizing mediastinitis was identified. The mean age of the patients was 38 years. They underwent a mean of 6 +/- 4 computed tomographic imaging studies, 4 +/- 1 transcervical drainage procedures, and 2 +/- 1 transthoracic drainage procedures. Three patients required abdominal exploration and 4 underwent tracheostomy. No deaths occurred. In contrast, 96 patients with descending necrotizing mediastinitis were identified from the literature with a mean age of 38 years. They underwent a mean of 2 +/- 1 computed tomographic imaging studies, 2 +/- 1 transcervical drainage procedures, and 0.7 + 0.3 transthoracic drainage procedures. Sixteen (17%) patients required abdominal exploration and 34 (35%) underwent tracheostomy. Twenty-eight (29%) patients from the literature cohort died during their treatment.

CONCLUSION

Descending necrotizing mediastinitis remains a life-threatening infection. On the basis of experience accrued in treating these patients, an algorithm incorporating computed tomographic imaging for diagnosis and surveillance and serial transcervical and transthoracic operative drainage is outlined in the hope of reducing the excessive mortality of descending necrotizing mediastinitis.

Clinical use of the Odstock dropped foot stimulator: its effect on the speed and effort of walking

OBJECTIVE

To assess the clinical effectiveness of the Odstock dropped foot stimulator by analysis of its effect on physiological cost index (PCI) and speed of walking. This functional electrical stimulation (FES) device stimulates the common peroneal nerve during the swing phase of gait.

DESIGN

A retrospective study of patients who had used the device for 4 1/2 months.

SUBJECTS

One hundred fifty-one patients with a dropped foot resulting from an upper motor neuron lesion.

SETTING

A medical physics and biomedical engineering department of a district general hospital specializing in the clinical application of FES and a neurophysiotherapy department at a separate hospital.

MAIN OUTCOME MEASURES

Changes in walking speed and effort of walking, as measured by PCI over a 10-meter course.

RESULTS

There was a 92.7% compliance with treatment. Stroke patients showed a mean increase in walking speed of 27% (p<.01) and reduction in PCI of 31% (p<.01) with stimulation, and changes of 14% (p<.01) and 19% (p<.01), respectively, while not using the stimulator. Multiple sclerosis patients gained similar orthotic benefit but no "carry-over."

CONCLUSIONS

The measured differences in walking with and without stimulation were statistically significant in the stroke and multiple sclerosis groups. In this study use of the stimulator improved walking. Those with stroke demonstrated a short-term "carry-over" effect.

The accuracy of the clinical diagnosis of new-onset idiopathic pulmonary fibrosis and other interstitial lung disease: A prospective study

STUDY OBJECTIVES

Presently, surgical (open or thoracoscopic) lung biopsy (SLB) is the gold standard for the diagnosis of new-onset idiopathic pulmonary fibrosis (IPF) and other interstitial lung diseases (ILDs). The accuracy of a clinical diagnosis of IPF and other subsets of ILD has never been established in prospective studies. We investigated the accuracy and validity of a clinical diagnosis of IPF and ILD other than IPF.

DESIGN

Prospective, independent evaluation of patients and clinical data by an ILD expert, of chest radiographic and high-resolution computed tomography (HRCT) features by a chest radiologist, and of histologic features of lung biopsy by a pulmonary pathologist in consecutive patients referred for a diagnostic evaluation of ILD.

SETTING

Tertiary university medical center with recognized expertise in management of ILD.

PATIENTS

Community patients referred for further definitive diagnostic evaluation of new-onset, untreated nonspecific ILD.

INTERVENTION

By comparing the histologic features of SLB in 59 patients consecutively referred for further diagnostic evaluation of new-onset ILD with the clinical and radiologic diagnoses, we determined the sensitivity and specificity of clinical diagnosis and radiologic diagnosis (based on chest radiograph and HRCT features alone) of IPF and ILD other than IPF. A specific clinical diagnosis was independently made by the ILD expert after a thorough clinical assessment that included evaluation of an HRCT scan and bronchoscopic findings. The chest radiographs and HRCT scans were separately reviewed by the chest radiologist, who made a radiologic diagnosis independently. All patients underwent SLB within a month of preoperative "clinical" diagnosis. The clinician's and radiologist's diagnoses were then compared with the gold standard of histologic diagnosis.

MEASUREMENTS AND RESULTS

Prior to the clinical evaluation at our center, 85% of patients who underwent SLB had nondiagnostic transbronchial biopsy. The diagnosis of IPF and ILD other than IPF was accurately made by clinical features alone in 62% of cases. The correct radiographic diagnosis of non-IPF ILD was made in 58% of the cases. The sensitivity and specificity of the clinical diagnosis of ILD other than IPF were 88.8% and 40%, respectively. The sensitivity and specificity of the radiographic diagnosis of ILD other than IPF were 59% and 40%, respectively. However, the sensitivity and specificity of the diagnosis of IPF on clinical grounds were 62% and 97%, respectively. The sensitivity and specificity of the radiologic diagnosis of IPF were 78.5% and 90%, respectively.

CONCLUSIONS

In a center with recognized expertise in the management of ILD, the specificity of diagnosis of new-onset IPF based on a thorough clinical assessment or HRCT features alone is very high (97% and 90%, respectively), but the sensitivity is low (62% and 78.5%, respectively). Thus, not all patients with new-onset IPF require SLB for diagnosis, but a diagnosis of IPF will be missed in nearly one third of new-onset IPF cases despite evaluation by experts. The relatively low sensitivity and specificity of the diagnosis of ILD other than IPF also emphasizes that an SLB is indicated in patients with ILD in whom the diagnosis is unclear.

Patients' perceptions of the Odstock Dropped Foot Stimulator (ODFS)

OBJECTIVE

To determine the perceived benefit, pattern and problems of use of the Odstock Dropped Foot Stimulator (ODFS) and the users' opinion of the service provided.

DESIGN

Questionnaire sent in a single mailshot to current and past users of the ODFS. Returns were sent anonymously.

SETTING

Outpatient-based clinical service.

SUBJECTS

One hundred and sixty-eight current and 123 past users with diagnoses of stroke (CVA), multiple sclerosis (MS), incomplete spinal cord injury (SCI), traumatic brain injury (TBI) and cerebral palsy (CP).

INTERVENTION

Functional electrical stimulation (FES) to correct dropped foot in subjects with an upper motor neuron lesion, using the ODFS.

MAIN OUTCOME MEASURES

Purpose-designed questionnaire.

RESULTS

Return rate 64% current users (mean duration of use 19.5 months) and 43% past users (mean duration of use 10.7 months). Principal reason cited for using equipment was a reduction in the effort of walking. Principal reasons identified for discontinuing were an improvement in mobility, electrode positioning difficulties and deteriorating mobility. There were some problems with reliability of equipment. Level of service provided was thought to be good.

CONCLUSION

The ODFS was perceived by the users to be of considerable benefit. A comprehensive clinical follow-up service is essential to achieve the maximum continuing benefit from FES-based orthoses.

Early complications. Chylothorax

Postpneumonectomy chylothorax is a very common but serious complication. Drainage of the pneumonectomy space, metabolic and nutritional support with TPN, and absolute enteral rest may lead to control of the leak. Failure of these measures to obtain a rapid resolution of the chyle losses should be followed by early surgical intervention in most instances in an effort to alleviate the chronic metabolic, nutritional, and immunological consequences of prolonged chyle losses.

Cytokines increase neonatal cardiac myocyte calcium concentrations: the involvement of nitric oxide and cyclic nucleotides

Neonatal rat cardiac myocytes were treated with cytokines, with or without the nitric oxide synthase (NOS) inhibitors N-monomethyl-L-arginine (LNMMA) and N-nitro-L-arginine methyl ester (LNAME), and systolic and diastolic calcium levels were measured by fluorescence spectrophotometry and confocal microscopy. Time-dependent changes following interferon-gamma (IFN-gamma) treatment revealed a continuing increase in intracellular calcium, which was reduced with LNMMA, but not with LNAME. Increases in calcium also occurred with interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha), but not to the extent seen with IFN-gamma. Increased cyclic guanosine monophosphate (cGMP) was involved in the results described with short-term (2 hr) TNF-alpha and long-term (18 hr) IFN-gamma treatments. Short-term exposure to IFN-gamma produced an increase in cyclic adenosine monophosphate (cAMP) and also an initial increase in the myocyte-bearing rate, with calcium levels either (i) subsequently returning to control levels while maintaining a fast beating rate or (ii), retaining a high systolic calcium level, but beating at control rates. Treatment with both IL-1beta and IFN-gamma stabilized the beating rate of the cells on some occasions. Shortening of myocytes increased with isoproterenol and following treatment with IFN-gamma, while isoproterenol stimulation of IFN-gamma-treated cells revealed increased contractile activity after short, but not long, treatment. LNMMA, but not reduced the increased contractile response with short-term IFN-gamma treatment. Our findings suggest that TNF-alpha acts via a cGMP-dependent pathway, whereas the actions of IFN-gamma involve adenylate cyclase, and possibly a NO-forming mechanism and cGMP pathway as well. It is also apparent that the two NO inhibitors function via different mechanisms or that LNMMA has a direct effect on the calcium-signaling pathway.

LPTP's (Laboratory Proficiency Testing Program) educational assistance program (EAP)--a review

The Educational Assistance Program (EAP) of the Laboratory Proficiency Testing Program (LPTP) in Ontario, Canada, provides at-the-bench in-service education to the technological staff in smaller, remote or rural hospital laboratories. This service is provided to laboratories which have either been identified by LPTP as experiencing problems or on direct request. The tutorials are conducted by experienced volunteer technologists. LPTP carries out mandatory testing and proficiency evaluation in Ontario. Funded by the Ministry of Health of Ontario, EAP is offered voluntarily and without charge as part of LPTP's educational component of external quality assessment. Preliminary post-tutorial proficiency testing results show improved performance and recipient evaluation forms express an enthusiastic response. Both support continuation of this unique program.

The new lung cancer staging system: what does it mean?

Staging now provides the basis for any cancer treatment, determining prognosis and treatment and allowing for comparison of clinical outcomes. Changes in the lung cancer staging system have been implemented to represent our evolving knowledge and expanding diagnostic and therapeutic modalities. Current changes are designed to be minimally disruptive to historical staging systems, but new methods of treatment and better understanding of tumor biology may revolutionize our current staging classification in the future.

Caspase-dependent activation of calpain during drug-induced apoptosis

We have previously demonstrated that calpain is responsible for the cleavage of Bax, a proapoptotic protein, during drug-induced apoptosis of HL-60 cells (Wood, D. E., Thomas, A., Devi, L. A., Berman, Y., Beavis, R. C., Reed, J. C., and Newcomb, E. W. (1998) Oncogene 17, 1069-1078). Here we show the sequential activation of caspases and calpain during drug-induced apoptosis of HL-60 cells. Time course experiments using the topoisomerase I inhibitor 9-amino-20(S)-camptothecin revealed that cleavage of caspase-3 substrates poly(ADP-ribose) polymerase (PARP) and the retinoblastoma protein as well as DNA fragmentation occurred several hours before calpain activation and Bax cleavage. Pretreatment with the calpain inhibitor calpeptin blocked calpain activation and Bax cleavage but did not inhibit PARP cleavage, DNA fragmentation, or 9-amino-20(S)-camptothecin-induced morphological changes and cell death. Pretreatment with the pan-caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (Z-VAD-fmk) inhibited PARP cleavage, DNA fragmentation, calpain activation, and Bax cleavage and increased cell survival by 40%. Interestingly, Z-VAD-fmk-treated cells died in a caspase- and calpain-independent manner that appeared morphologically distinct from apoptosis. Our results suggest that excessive or uncontrolled calpain activity may play a role downstream of and distinct from caspases in the degradation phase of apoptosis.

Apparatus to measure simultaneously 14 isometric leg joint moments. Part 1: Design and calibration of six-axis transducers for the forces and moments at the ankle

An apparatus has been developed for making isometric measurements of the joint moments corresponding to the 14 degrees of freedom of the legs, in postures ranging between sitting and near full extension. The apparatus is called the multi-moment chair system (MMCS) and is described in the companion paper. This paper describes the most critical components of the MMCS, which are the six-axis transducers for measuring the force and moment components on the plantar-flexion axis of each ankle while the feet are laced into fixed shoes. The transducers are made of steel bars, on which strain gauges are mounted, joined by clamps. The design of the transducer and methods of calibration and error estimation are described. The RMS errors are less than 2 N for the forces and 1 Nm for the moments, but these may be correlated. A method for error reduction that compensates for the finite compliance of the transducer does not reduce the measured errors.

Apparatus to measure simultaneously 14 isometric leg joint moments. Part 2: Multi-moment chair system

An apparatus has been developed that measures isometrically the 14 lower limb joint moments corresponding to the degrees of freedom of the hips, knees and ankles. This is the second of two papers describing the development of the multi-moment chair system (MMCS). It presents the overall design and changes that were implemented to compensate for problems. These were primarily to improve the accuracy of hip joint moments; a compromise between accuracy and practicalities, because of force-moment responses being measured at the ankles. All joint moment errors have been calculated to be of the order of a few newton metres. Since these represent errors of less than 10% when considering peak joint moment responses, this is considered sufficiently accurate for the proposed application. The MMCS is being used in a programme to investigate the restoration of lower limb functions, principally standing, in paraplegics by electrical stimulation of the lumbosacral anterior roots.

Bronchial-atrial fistula after lung transplant resulting in fatal air embolism

We describe a rare case of fatal air embolism in a patient in whom a left atrial-bronchial fistula developed 1 month after single lung transplant. The cause was a combination of mediastinal infection and bronchial necrosis.

Bax cleavage is mediated by calpain during drug-induced apoptosis

The anti-apoptotic molecule Bcl-2 is located in the mitochondrial and endoplasmic reticulum membranes as well as the nuclear envelope. Although its location has not been as rigorously defined, the pro-apoptotic molecule Bax appears to be mainly a cytosolic protein which translocates to the mitochondria upon induction of apoptosis. Here we identify a protease activity in mitochondria-enriched membrane fractions from HL-60 cells capable of cleaving Bax which is absent from the cytosolic fraction. Bax protease activity is blocked in vitro by cysteine protease inhibitors including E-64 which distinguishes it from all known caspases and granzyme B, both of which are involved in apoptosis. Protease activity is also blocked by inhibitors against the calcium-activated neutral cysteine endopeptidase calpain. Partial purification of the Bax protease activity from HL-60 cell membrane fractions by column chromatography revealed that a calpain-like activity was the protease responsible for Bax cleavage. In addition, purified calpain enzymes cleaved Bax in a calcium-dependent manner. Pretreatment of HL-60 cells with the specific calpain inhibitor calpeptin effectively blocked both drug-induced Bax cleavage and calpain activation, but not PARP cleavage or cell death. These results suggest that calpains and caspases are activated during drug-induced apoptosis and that calpains, along with caspases, may be involved in modulating cell death by acting selectively on cellular substrates.

Lung volume reduction surgery has variable effects on blood gases in patients with emphysema

Most studies of bilateral lung volume reduction surgery (LVRS) report increases in arterial oxygenation (PaO2). Some suggest this results from an increased alveolar ventilation, but others imply that ventilation-perfusion heterogeneity is reduced. We measured arterial blood gases (ABGs) on air before and 3 mo following LVRS in 46 patients (61% of eligible patients), estimate the difference between alveolar and arterial O2 (AaPO2), and correlated the changes observed with preoperative ABGs, and with pre-and postoperative pulmonary function. The mean +/- SD change in PaO2 and AaPO2 was +3 +/- 10 mm Hg (p = 0.058) and +1 +/- 11 mm Hg (p = NS), respectively, and the range of change was large (-17 to +29 mm Hg and -24 to +23 mm Hg, respectively). The mean change in PaCO2 was -3 +/- 5 mm Hg (p < 0.05) and ranged from -11 to +5 mm Hg. Changes in PaO2 and AaPO2 were poorly correlated with changes in PaCO2 or with pre- or postoperative pulmonary function. Although some patients had a marked improvement in ABGs following LVRS, almost as many deteriorated. On average, only minimal effects were seen. Although mean alveolar ventilation improved somewhat, the effect of LVRS on PaO2 primarily resulted from alterations in ventilation-perfusion heterogeneity.

Interferon-inducible T cell alpha chemoattractant (I-TAC): a novel non-ELR CXC chemokine with potent activity on activated T cells through selective high affinity binding to CXCR3

Chemokines are essential mediators of normal leukocyte trafficking as well as of leukocyte recruitment during inflammation. We describe here a novel non-ELR CXC chemokine identified through sequence analysis of cDNAs derived from cytokine-activated primary human astrocytes. This novel chemokine, referred to as I-TAC (interferon-inducible T cell alpha chemoattractant), is regulated by interferon (IFN) and has potent chemoattractant activity for interleukin (IL)-2-activated T cells, but not for freshly isolated unstimulated T cells, neutrophils, or monocytes. I-TAC interacts selectively with CXCR3, which is the receptor for two other IFN-inducible chemokines, the IFN-gamma-inducible 10-kD protein (IP-10) and IFN-gamma- induced human monokine (HuMig), but with a significantly higher affinity. In addition, higher potency and efficacy of I-TAC over IP-10 and HuMig is demonstrated by transient mobilization of intracellular calcium as well as chemotactic migration in both activated T cells and transfected cell lines expressing CXCR3. Stimulation of astrocytes with IFN-gamma and IL-1 together results in an approximately 400,000-fold increase in I-TAC mRNA expression, whereas stimulating monocytes with either of the cytokines alone or in combination results in only a 100-fold increase in the level of I-TAC transcript. Moderate expression is also observed in pancreas, lung, thymus, and spleen. The high level of expression in IFN- and IL-1-stimulated astrocytes suggests that I-TAC could be a major chemoattractant for effector T cells involved in the pathophysiology of neuroinflammatory disorders, although I-TAC may also play a role in the migration of activated T cells during IFN-dominated immune responses.

Randomized, placebo-controlled, multicenter trial of granulocyte-macrophage colony-stimulating factor as infection prophylaxis in oncologic surgery. Leukine Surgical Prophylaxis Research Group

PURPOSE

Postoperative infections are a frequent source of preventable morbidity and mortality in the oncologic population. Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a potent modulator of immune effector cells in vitro and in vivo. This study was conducted to determine whether GM-CSF, when administered perioperatively, could reduce the incidence of surgical infections in cancer patients.

METHODS

This was a prospective, randomized, placebo-controlled, multicenter study. Cancer patients at high risk of infectious surgical morbidity were randomized to receive GM-CSF 125 microg/m2 per day or placebo subcutaneously for 8 days beginning 3 days preoperatively. Routine antibiotic prophylaxis was administered to all patients.

RESULTS

Three hundred ninety-nine patients were enrolled, with 198 randomized to receive GM-CSF. Twenty-one percent of patients experienced infections during the first 2 weeks postoperatively, and there was no difference in infection rate between the study groups. The most common sites of infection were respiratory tract (53%) and surgical wound (25%). The duration of operation and American Society of Anesthesiology (ASA) physical status classification were the most significant predictors of infection in multivariate analysis. GM-CSF was well tolerated and was not associated with fever.

CONCLUSION

The eligibility criteria for this study were successful at defining a patient subgroup at high risk for postoperative infections. At an immunomodulatory dose of 125 microg/m2 per day, GM-CSF was safe and well tolerated, but did not reduce the incidence of postoperative infections in this high-risk oncologic population. Infectious morbidity in surgical oncology remains an important subject for continued clinical investigation.

Percutaneous placement of tracheal T tube

Tracheal T tubes provide effective palliation of unresectable benign and malignant tracheal obstruction, but placement may be difficult when previous operation, radiation, or tumor limits surgical exposure of the cervical trachea. Percutaneous placement using commercially available percutaneous tracheostomy kits may provide an alternative approach in these cases.

Lung-volume reduction surgery for diffuse emphysema: radiologic assessment of changes in thoracic dimensions

Patients with severe, diffuse emphysema may be candidates for pneumectomy (lung-volume reduction surgery, LVRS) to improve lung and respiratory muscle function. To identify candidates who might benefit from this surgery, it is necessary to understand how lung volumes and respiratory function are effected. In this article, the authors demonstrate a significant difference in lung size on chest radiographs obtained before and after surgery. Thirty-five of 71 consecutive patients undergoing LVRS had both preoperative and postoperative chest radiographs and pulmonary function tests available for retrospective review. Preoperative and postoperative measurements of lung height, transthoracic diameters, mediastinal width, heart size, diaphragmatic arc, and intercostal spaces were compared using paired t-tests. Radiographic measurements where also correlated with changes in lung volumes as measured by pulmonary function tests. Lung heights (right, left, mean lateral) and coronal diameter at the aortic arch were reduced after surgery (all p < 0.05). Forced vital capacity, forced expiratory volume in 1 second (FEV1), and vital capacity increased, and total lung capacity and residual volume decreased after surgery (all p < 0.05). Left lung height showed a significant correlation (p = 0.025) with FEV1; all other correlations between radiographic changes and pulmonary function test changes were not significant. The explanation for improved lung function in patients after LVRS is not completely clear and is probably multifactorial. Radiologic alterations reflect anatomic changes caused by surgery and support the theory that modifications of chest wall configuration occur and are likely responsible, in part, for improved symptomatology and respiratory function.

Successful lung transplantation in spite of cystic fibrosis-associated liver disease: a case series

Lung transplantation has recently offered hope for prolonged survival in patients with cystic fibrosis. Patients with cystic fibrosis have a 7% prevalence of associated liver disease and portal hypertension. These patients have been previously excluded from consideration for lung transplantation. The natural history of cystic fibrosis-associated liver disease suggests a benign and protracted course in most cases. At the University of Washington, 14 of 53 patients (26%) have undergone lung transplantation for cystic fibrosis-related respiratory failure. We report the outcome of double lung transplantation in four of these 14 patients who also had cystic fibrosis-associated liver disease and portal hypertension, all of whom were symptom free from their liver disease. All four patients are alive and well without complications 4 to 31 months after transplantation. We conclude that the presence of cystic fibrosis-associated liver disease with portal hypertension, in the setting of good synthetic function (albumin > 3.0 gm/L and normal prothrombin time), normal serum bilirubin, minimal varices, without ascites or encephalopathy, should not be an absolute contraindication to lung transplantation. We recommend that other transplantation centers also include this patient population in consideration for lung transplantation.

The effects of common peroneal stimulation on the effort and speed of walking: a randomized controlled trial with chronic hemiplegic patients

OBJECTIVE

To measure the effect of the Odstock Dropped Foot Stimulator (ODFS), a common peroneal stimulator, on the effort and speed of walking.

DESIGN

A randomized controlled trial.

SUBJECTS

Hemiplegic patients who had suffered a single stroke at least six months prior to the start of the trial whose walking was impaired by a drop-foot.

INTERVENTIONS

The treatment, functional electrical stimulation (FES) group, used the stimulator and received a course of physiotherapy; the control group received physiotherapy alone.

MAIN OUTCOME MEASURES

Changes in walking speed measured over 10 m and the effort of walking measured by physiological cost index (PCI).

RESULTS

Thirty-two subjects completed the trial, 16 in the FES group and 16 in the control group. Mean increase in walking speed between the beginning and end of the trial was 20.5% in the FES group (when the stimulator was used), and 5.2% in the control group. Improvement was also measured in PCI with a reduction of 24.9% in the FES group (when the stimulator was used) and 1% in the control group. No improvement in these parameters was measured in the FES group when the stimulator was not used.

CONCLUSION

Walking was statistically significantly improved when the ODFS was worn but no 'carry-over' was measured. Physiotherapy alone, in this group of subjects with established stroke, did not improve walking.

Lung volume reduction surgery improves maximal O2 consumption, maximal minute ventilation, O2 pulse, and dead space-to-tidal volume ratio during leg cycle ergometry

Early experience suggests that lung volume reduction surgery improves exercise tolerance as measured by the 6-min walk distance in patients with emphysema. To identify the physiologic mechanism(s) by which lung volume reduction surgery improved exercise, we performed progressive cardiopulmonary exercise testing, including rest and peak exercise blood gas determinations, on 21 consecutive patients before and 3 mo after lung volume reduction surgery. Maximal work (median, range, % change) increased 17.5 watts (-13 to +44 watts, 46%, p < 0.05), maximal oxygen consumption increased 0.16 L/min (-0.17 to +0.48, 25%, p < 0.05), maximal ventilation increased 6.6 L/min (-7 to +26 L/min, 27%, p < 0.05), and the dead space/tidal volume ratio at peak exercise decreased 0.07 (-0.22 to +0.09, 12%, p < 0.05), exclusively as a result of an increase in the tidal volume. After lung volume reduction surgery heart rate decreased at the point of isowatt exercise, from 115 to 111 beats/min (p < 0.05). No difference was observed in the other physiologic variables measured at isowatt exercise. In 13 patients exercised while breathing room air, the alveolar-to-arterial O2 difference increased, and the arterial O2 tension decreased from rest to peak exercise both before and after the operation, but significant changes in this response were not observed after surgery. The primary problem limiting exercise performance in these patients was the limited ventilatory capacity as 16 and 13 of the 21 subjects developed acute respiratory acidemia at peak exercise before and after surgery, respectively. Lung volume reduction surgery in patients with severe emphysema improved maximal ventilation, thereby improving maximal exercise performance.

Tracheobronchial resection and reconstruction

OBJECTIVE

To assess the indications and results of airway resection and how frequently airway reconstructive options changed proposed therapy.

DESIGN

A retrospective survey of patients undergoing major airway resection.

SETTING

University of Washington-affiliated hospitals, Seattle, May 1992 through December 1996.

PATIENTS

Fifty consecutive patients with resectable benign and malignant tracheal or main bronchial disease undergoing tracheobronchial resections.

INTERVENTIONS

Patients underwent major airway resection as follows: tracheal or laryngotracheal resection, 23 patients; carinal resection, 6; and bronchial sleeve resection with or without pulmonary resection, 21. Indications for surgery were non-small cell lung cancer in 19 patients, primary airway tumor in 12, thyroid carcinoma in 1, and tracheal or bronchial stenosis in 18.

MAIN OUTCOME MEASURES

Change in prereferral planned therapy from palliative to definitive or to pulmonary-sparing procedure, morbidity and mortality, relief of symptoms, and survival.

RESULTS

Mortality was 0%, and morbidity, 32% (15/50). Airway reconstruction changed the proposed therapy in 42 patients (84%). Functional results were good to excellent in 17 (94%) of 18 patients with benign disease. Patients with malignant disease had a 1-year survival of 93% (27/29) and a 2-year survival of 67% (12/18).

CONCLUSIONS

Airway resection and reconstruction provide reliable relief of benign and malignant tracheobronchial disease with minimal morbidity and mortality. Airway reconstruction frequently changed prereferral planned therapy and provided definitive and parenchymal-sparing procedures to patients with complex airway lesions.