Subsequent pulmonary embolism: risk after a negative helical CT pulmonary angiogram--prospective comparison with scintigraphy.

PURPOSE: To determine whether a helical computed tomographic (CT) scan that is negative for pulmonary embolism (PE) is a sufficiently reliable criterion to safely withhold anticoagulation therapy. MATERIALS AND METHODS: Patients with negative helical CT scans were prospectively compared with patients with negative or low-probability scintigrams. In a 460-bed university hospital and clinic, 1,015 adult patients underwent either scintigraphy or helical CT for possible PE for 25 months. Five hundred forty-eight patients who had negative images and were not receiving anticoagulation therapy were prospectively followed up for 3 months for clinical, new imaging, death certificate, or autopsy evidence of subsequent PE. Ninety-seven patients were lost to follow-up. RESULTS: Subsequent PE was found in two (1.0%) of 198 patients with negative CT scans, none of 188 patients with negative ventilation-perfusion (V-P) scans, and five (3.1%) of 162 patients with low-probability V-P scans (not statistically significant). Patients in the helical CT group were hospitalized more often, had more severe disease, had more substantial PE risk factors, and had a higher death rate. No deaths were attributed to PE in either group. CONCLUSION: The frequency of clinical diagnoses of PE after a negative CT scan was low and similar to that after a negative or low-probability V-P scan. Helical CT is a reliable imaging tool for excluding clinically important PE.

Spiral computed tomography in the evaluation of pulmonary embolism.

Determining the presence or absence of thromboembolic disease can often be problematic. Traditional diagnostic algorithms are reviewed and discussed. Spiral CT technology allows a relatively noninvasive visualization of the pulmonary vasculature and is a promising new diagnostic modality for acute and chronic thromboembolic disease. Its potential roles are discussed, and a new diagnostic algorithm is proposed.

Functional and oximetric assessment of patients after lung reduction surgery.

OBJECTIVE: The goal of this study was to clarify the issue of functional oxygen requirement by regimented exercise oximetry in patients undergoing lung reduction surgery. METHODS: Thirty-seven patients underwent lung reduction surgery and were followed up for at least 3 months. Patients routinely completed a 6-week program of cardiopulmonary rehabilitation. Preoperative and postoperative spirometry, dyspnea scores, 6-minute walk distances, respiratory mechanics, and exercise oximetry were recorded. RESULTS: After the operation, patients had a 37% increase in forced vital capacity and a 59% increase in forced expiratory volume in 1 second. Six-minute walk distance increased from 913 +/- 310 feet before the lung reduction operation to 1202 +/- 274 feet 6 months after the operation (p < 0.001). Maximal inspiratory and expiratory pressures were significantly increased in 16 patients after lung reduction surgery. Perceived dyspnea was significantly improved. Exercise pulse oximetry demonstrated that 83% of patients met American Thoracic Society criteria for supplemental oxygen use before lung reduction surgery. After the operation, 70% of patients continued to meet American Thoracic Society criteria for supplemental oxygen use. Notably, 10 patients with exertional desaturation while breathing room air discontinued supplemental oxygen use because of a reduction in dyspnea. CONCLUSIONS: These findings demonstrate significant subjective and functional improvements related to lung reduction surgery. Exercise-induced hypoxia was not reversed by lung reduction surgery. Discontinuance of supplemental oxygen use owing to reduction in dyspnea and improved physical performance may not be warranted in lieu of continued exertional desaturation.

Self-selected walking velocity for functional ambulation in patients with end-stage emphysema.

PURPOSE: Considerable attention has been given to ambulation and dyspnea in the population with chronic obstructive pulmonary disease; however, previous studies leave the question of what constitutes functional ambulation in this population unanswered. This article examines ambulation for functional independence in the community for patients with-end-stage emphysema based on their self-selected walking velocity (SSWV) during a 6-minute walk (6 MW) and a timed get up and go (GUG) test. METHODS: Fifty-nine patients (28 women, 31 men; mean age of 65.1 +/- 7.2 years) referred for lung transplantation or lung volume reduction surgery (mean forced expiratory volume in 1 second [FEV1] of 0.60 +/- 0.20 L; mean FEV1 as percent of predicted [FEV1%] of 22.7 +/- 8.7%) each had a 6 MW and GUG test performed on the same day. Calculations for SSWV and estimated energy expenditure were determined using the horizontal walking formula by the American College of Sports Medicine. RESULTS: No statistically significant gender differences were identified for distance walked (235.1 +/- 92.0 m), rest time taken (33.2 +/- 58.5 seconds), actual walk time (5.5 +/- 1.0 minutes), or SSWV (42.2 +/- 13.9 m/min or 1.6 +/- 0.5 miles per hour) during the 6 MW. Men tended to walk farther and faster but rested more. The SSWV during the GUG test was similar (mean 41.8 +/- 10.9 m/min or 1.6 +/- 0.4 miles per hour) to the SSWV during the 6 MW. Estimated energy expenditure was approximately 1.6 to 3.4 metabolic equivalents (METS; mean 2.3 +/- 0.5 METS). CONCLUSION: The literature defines independent community ambulation as the ability to walk at least 332 m at a near-normal velocity of approximately 80 m/min. This study population was significantly impaired for both distance and the velocity required to ambulate independently in the community. Documentation of both rest time and walk time taken during a 6 MW test will enable SSWV to be calculated and interpreted as it relates to independent community ambulation.

Pulmonary function changes in long-term survivors of bone marrow transplantation.

PURPOSE: This study was undertaken to evaluate long-term pulmonary function changes in patients undergoing bone marrow transplantation (BMT), to assess their clinical significance, and to identify factors influencing these changes. METHODS AND MATERIALS: Pulmonary function tests (PFT) were evaluated before and after BMT in 111 adult patients undergoing BMT between 1985 and 1991. Forced expiratory volume at 1 s (FEV1), forced vital capacity (FVC), diffusing capacity (DLCO), and total lung capacity (TLC) were evaluated. One hundred and three patients (92.8%) received total body irradiation (TBI) to a total dose of 14 Gy in nine equal fractions. The lung dose was restricted to < 6.5 Gy in 95% of patients with partial transmission lung shielding. Seventy-eight percent of patients had acute graft-versus-host disease (aGVHD), 69% chronic graft-vs.-host disease (cGVHD), and 63% posttransplant pulmonary infection. Effects of GVHD, TBI, radiation dose to the lungs, dose rate of TBI, posttransplant pulmonary infection, Busulfan use for conditioning, age, and history of smoking were evaluated for their influence on pulmonary function. RESULTS: Posttransplant FEV1, FVC, and TLC were lower than pretransplant values (p < 0.05) at 6 months and 1 year posttransplant with subsequent recovery. DLCO was significantly lower at all posttransplant intervals. FEV1 did not fall significantly in patients without acute or chronic GVHD and recovered earlier than in patients without posttransplant pulmonary infection. Recovery of FVC, TLC, and DLCO was also delayed in patients with acute and chronic GVHD and posttransplant pulmonary infection. Multiple regression analysis revealed an association between a higher radiation dose to the lungs, and decreased FVC at 2 years (p = 0.01). Progressive obstructive pulmonary disease was not observed. CONCLUSION: An initial decline in PFTs with subsequent recovery was observed. Factors associated with delayed recovery and incomplete recovery of PFTs were GVHD, posttransplant pulmonary infection, and higher radiation dose to the lungs. The conditioning regimen used at Medical College of Wisconsin, including relatively high TBI doses with partial transmission pulmonary shielding, appears to be well tolerated by the lungs in long-term survivors. No progressive decline in PFTs or symptomatic decline in pulmonary function was observed during the time interval studied.

Nosocomial pneumonia.

Nosocomial pneumonia continues to be a major problem plaguing hospitalized patients, especially those on ventilators. Gram-negative bacteria and S. aureus are the most common causitive organisms. Alteration of the normal oropharyngeal flora and contamination of the respiratory tract from the pharynx and stomach are now recognized to be important factors in its development. As there is no definitive diagnostic test, nosocomial pneumonia remains a clinical diagnosis; however bronchoscopy with protected specimen brush cultures and BAL are diagnostic methods under study. Noninvasive radiologic examinations and clinical criteria have poor specificity in diagnosis.

Detection of pulmonary embolism in patients with unresolved clinical and scintigraphic diagnosis: helical CT versus angiography.

OBJECTIVE: This study was designed to prospectively compare helical CT with pulmonary angiography in the detection of pulmonary embolism in patients with an unresolved clinical and scintigraphic diagnosis. SUBJECTS AND METHODS: Twenty patients with an unresolved suspicion of pulmonary embolism were evaluated with contrast-enhanced helical CT and with selective pulmonary angiography. An average of 11 hr separated the two studies. The CT scans were obtained during one 24-sec or two 12-sec breath-holds. CT scans were interpreted without knowledge of the results of scintigraphy or angiography. Selective pulmonary angiograms were obtained with knowledge of the findings on the ventilation/perfusion scan only. The sensitivity and specificity of CT were compared with those of angiography for central vessels (segmental and larger) only and for all vessels. RESULTS: Eleven of the 20 patients had proved pulmonary embolism (seven in central vessels and four in subsegmental vessels only). When only central vessels were analyzed, CT sensitivity was 86%, specificity was 92%, and the likelihood ratio was 10.7. However, when subsegmental vessels were included, CT results were 63%, 89%, and 5.7, respectively. CONCLUSION: In our subset of patients, helical CT was only 63% sensitive. Subsegmental emboli are difficult to diagnose. Pulmonary angiography remains the study of choice. CT has a limited role in the evaluation of acute pulmonary embolism.

Postcontrast CT in the diagnosis and assessment of response to thrombolysis in massive pulmonary embolism.

We present a case of massive acute pulmonary embolism where contrast enhanced helical CT was compared with standard angiography for diagnosis and for monitoring subsequent response to thrombolytic therapy. There was very close concordance of the findings on these modalities suggesting that contrast enhanced helical CT may be an easy and reliable alternative to standard angiography.

Arachidonate metabolism increases as rat alveolar type II cells differentiate in vitro.

Rat type II alveolar epithelial cells are known to undergo morphological and functional changes when maintained in culture for several days. Having previously demonstrated that these cells can deacylate free arachidonic acid (AA) and metabolize it to products of the cyclooxygenase pathway, the present study was undertaken to determine whether in vitro differentiation was accompanied by alterations in the availability and metabolism of AA. We assessed the constitutive and ionophore A23187-induced deacylation and metabolism of endogenous AA, as well as the metabolism of exogenously supplied AA, in primary cultures of rat type II cells at days 2, 4, and 7 after isolation. Levels of free endogenous AA were increased at day 4, whereas eicosanoid synthesis, predominantly prostaglandin E2 and prostacyclin, increased markedly only at day 7. A similar time course of augmentation of prostanoid release was seen in response to exogenous AA. Type II cells cultured on fibronectin, intended to hasten cell flattening and spreading, demonstrated accelerated increases in available free AA in response to A23187; cells cultured on basement membrane derived from Engelbreth-Holm-Swarm mouse sarcoma, known to maintain the type II phenotype, exhibited diminished levels of available free AA. From these findings, we conclude that alterations in arachidonate metabolism are linked to alterations in cellular phenotype. The potentiation of eicosanoid synthesis accompanying in vitro differentiation suggests a possible role for the alveolar epithelium in the modulation of inflammation and fibrosis in the distal lung.