Prevalence of acute pulmonary embolism in central and subsegmental pulmonary arteries and relation to probability interpretation of ventilation/perfusion lung scans

PURPOSE: The purpose of this investigation is to determine the prevalence of acute pulmonary embolism (PE) limited to subsegmental pulmonary arteries. BACKGROUND: Contrast-enhanced helical (spiral) and electron-beam CT, in the hands of experienced radiologists who are skillful with this modality, are sensitive for the detection of acute PE in central pulmonary arteries, but have a low sensitivity for the detection of PE limited to subsegmental pulmonary arteries. The potential for CT to diagnose PE, therefore, is partially dependent on the prevalence of PE limited to subsegmental pulmonary arteries. METHODS: Data are from the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED). The largest pulmonary arteries that showed PE, as interpreted by the PIOPED angiographic readers, were identified in 375 patients in PIOPED with angiographically diagnosed PE. RESULTS: Among all patients with PE, 6% (95% confidence interval [CI], 4 to 9%) had PE limited to subsegmental branches of the pulmonary artery. Patients with high-probability ventilation/ perfusion (V/Q) scans had PE limited to subsegmental branches in only 1% (95% CI, 0 to 4%). Among patients with low-probability V/Q lung scans, 17% (95% CI, 8 to 29%) had PE limited to the subsegmental branches. Patients with low-probability V/Q scans and no prior cardiopulmonary disease had PE limited to the subsegmental pulmonary arteries in 30% (95% CI, 13 to 53%), whereas patients with low-probability V/Q scans who had prior cardiopulmonary disease had PE limited to subsegmental pulmonary arteries in 8% (95% CI, 2 to 22%) (p < 0.05). CONCLUSION: Based on data from all patients with PE in PIOPED, the prevalence of PE limited to subsegmental pulmonary arteries is low, 6%. PE limited to subsegmental pulmonary arteries was most prevalent among patients with low-probability V/Q scans, particularly if they had no prior cardiopulmonary disease.     

DTPA aerosol in ventilation/perfusion scintigraphy for diagnosing pulmonary embolism

The use of lung scintigraphy in evaluating suspected pulmonary embolism (PE) is controversial. Several diagnostic methods have been described for lung scans, of which the most widely applied uses 99mTc-MAA for perfusion, 133Xe for ventilation and PIOPED diagnostic criteria. This study evaluates the accuracy of lung scintigraphy using an alternative ventilation agent, 99mTc-diethylenetriamine pentacetic acid (DTPA) aerosol, and specific criteria. METHODS: Diagnostic criteria for DTPA aerosol ventilation were prospectively applied to 5017 patients over a 9-yr period. Lung scan interpretations were analyzed for frequency of occurrence, and results were compared to those of angiography in 455 patients. RESULTS: Scans were interpreted as normal, low or high probability in 79% of patients and as either indeterminate or medium probability in 21% of patients. Three patients had normal scans and negative angiography. In patients with low-probability scans, 111 angiograms were performed: 103 (93%) were negative, and 8 (7%) were positive. In patients with indeterminate scans, 114 angiograms were performed: 85 (75%) were negative, and 29 (25%) were positive. In patients with medium-probability scans, 149 angiograms were performed: 86 (58%) were negative, and 63 (42%) were positive. In patients with high-probability scans, 78 angiograms were performed: 6 (8%) were negative, and 72 (92%) were positive. CONCLUSION: These results indicate that lung scintigraphy using DTPA aerosol and our criteria is accurate in diagnosing and stratifying risk of pulmonary embolic disease. Compared with 133Xe and PIOPED criteria, DTPA ventilation and our criteria reduced the false-negative rate in low-probability scans (7% versus 16%, p < 0.005) and decreased the fraction of intermediate-probability scans (21 % versus 39%, p < 0.01).     

Value of perfusion lung scan in the diagnosis of pulmonary embolism: results of the Prospective Investigative Study of Acute Pulmonary Embolism Diagnosis (PISA-PED)

To assess the value of perfusion lung scan in the diagnosis of pulmonary embolism, we prospectively evaluated 890 consecutive patients with suspected pulmonary embolism. Prior to lung scanning, each patient was assigned a clinical probability of pulmonary embolism (very likely, possible, unlikely). Perfusion scans were independently classified as follows: (1) normal, (2) near-normal, (3) abnormal compatible with pulmonary embolism (PE+: single or multiple wedge-shaped perfusion defects), or (4) abnormal not compatible with pulmonary embolism (PE-: perfusion defects other than wedge-shaped). The study design required pulmonary angiography and clinical and scintigraphic follow-up in all patients with abnormal scans. Of 890 scans, 220 were classified as normal/or near-normal and 670 as abnormal. A definitive diagnosis was established in 563 (84%) patients with abnormal scans. The overall prevalence of pulmonary embolism was 39%. Most patients with angiographically proven pulmonary embolism had PE+ scans (sensitivity: 92%). Conversely, most patients without emboli on angiography had PE- scans (specificity: 87%). A PE+ scan associated with a very likely or possible clinical presentation of pulmonary embolism had positive predictive values of 99 and 92%, respectively. A PE- scan paired with an unlikely clinical presentation had a negative predictive value of 97%. Clinical assessment combined with perfusion-scan evaluation established or excluded pulmonary embolism in the majority of patients with abnormal scans. Our data indicate that accurate diagnosis of pulmonary embolism is possible by perfusion scanning alone, without ventilation imaging. Combining perfusion scanning with clinical assessment helps to restrict the need for angiography to a minority of patients with suspected pulmonary embolism.     

A comparison of SPECT and planar ventilation perfusion lung scanning

In order to define the role of Single Photon Emission Computed Tomography (SPECT) in the diagnosis of pulmonary embolus; SPECT and Planar ventilation and perfusion lung studies were performed consecutively on eleven patients referred with suspected embolus. Three patients were shown to have 'high probability' ventilation perfusion mismatches. SPECT imaging allowed segmental localisation of the perfusion defect and revealed additional defects not seen on planar scans. SPECT lung study was performed with minimal technical difficulty and was well tolerated by all patients studied. SPECT is likely to become the method of choice for investigating patients referred with suspected pulmonary embolus.     

Ventilation-perfusion lung scanning and spiral computed tomography of the lungs: competing or complementary modalities?

The recently developed technique of spiral computed tomographic angiography (CTA) is being used for the detection of pulmonary emboli (PE), and several studies have assessed its accuracy using pulmonary angiography as the gold standard. CTA shows a high level of accuracy in the detection of pulmonary emboli in segmental or larger central vessels. The specificity is high enough to eliminate the requirement for angiography if a positive CTA result is found. The main factor limiting the sensitivity of CTA is the frequency of peripheral emboli in the vessels outside the central chest field covered by CTA. The incidence of such peripheral emboli varies in different reports from 0% to 36%, and their significance remains arguable. Interpretative criteria for V./Q.- lung scintigraphy have been refined as a result of the lessons learned from the PIOPED study. Using these modified criteria, and taking into account the prior probability of PE based on the presence or absence of clinical risk factors, treatment decisions can be reasonably made in patients in the following categories: those with normal lung scans, those with high probability scans and high prior probability of PE, and those with low probability scans and low clinical suspicion. Patients with intermediate probability or indeterminate scans, and those in whom the scan results conflict with the clinical expectation, will need further tests. Ultrasound examination of the leg veins, if positive, will select a further subgroup of patients for active treatment. Patients with a negative or inconclusive ultrasound result, who previously have been candidates for pulmonary angiography, can now go on to CTA. The advantages in specificity which CTA offers will make it an important part of the diagnostic workup for selected patients, but in view of its increased cost and high radiation dose compared with V./Q. scintigraphy, the argument that CTA should completely replace lung scintigraphy is currently unsupportable.     

Effects of insulin therapy on non-insulin-dependent diabetics with secondary oral hypoglycemic agent failure

A recent trend among physicians is the categorisation of lung scans as normal [excludes pulmonary embolism (PE)], high probability (confirms PE) and non-diagnostic (no judgement on PE risk). The low probability scan is therefore being eliminated as a functional category. This occasional survey contends that such an approach is misguided. Correction of the original PIOPED data with certain assumptions provides a more reproducible, albeit restricted, low probability scan category which excludes PE in 97% of cases in the low pre-test clinical category. Patients with a low probability scan with risk factors for PE (i.e. medium clinical risk) will require further investigation. More important, the very low probability scan category excludes PE in 98% of patients with low and more than 92% of patients with medium pre-test clinical likelihood. The demise of "low probability" is premature.     

Experimentally induced nasal hypersecretion does not reduce the efficacy of intranasal levocabastine

Pulmonary tumor embolism is an often missed antemortem diagnosis in patients with cancer and respiratory failure. Although rare, this complication is an important cause of additional morbidity. Referred for radionuclide pulmonary perfusion and ventilation scintigraphy, a typical pattern of multiple subsegmental peripheral defects on perfusion lung scanning without matching ventilation defects, suggesting a high probability of pulmonary thromboembolism, often leads to false conclusions. We present a case of bilateral multiple subsegmental mismatched defects in lung ventilation perfusion scintigraphy, where autopsy confirmed the diagnosis of pulmonary tumor embolism, secondary to an undifferentiated ductal type adenocarcinoma of the pancreas. Pulmonary tumor embolism is an entity to keep in mind in patients treated for carcinoma presenting with (sub) acute dyspnea.     

Hyperlucent lung secondary to homocystinuria

At 23 months of age, one of a pair of monozygotic twins with radiographic unilateral hyperlucent lung was evaluated by radionuclide ventilation/perfusion pulmonary studies, which revealed a ventilation/perfusion mismatch of an entire lung. This twin died, and autopsy revealed pulmonary arterial thrombosis and histological changes compatible with homocystinuria, which was subsequently shown to be present in the surviving twin as well. A ventilation/perfusion lung scan of the surviving twin revealed multiple ventilation/perfusion mismatched defects, suggestive of pulmonary embolism. The presenting manifestation of homocystinuria in these patients was the pulmonary thrombotic disease. Neither twin had any other stigmata of homocystinuria at the time of initial presentation.     

Experimental study of the reaction pp-->pp pi 0 in the energy range 600-900 MeV

To compare regional thallium-201 SPECT redistribution patterns with rubidium-82 PET, we studied 81 patients with both imaging modalities. Sixty patients had significant coronary artery disease. All patients underwent PET imaging after dipyridamole infusion, while SPECT imaging was performed after exercise stress (38 patients) and dipyridamole (43 patients). Sixty-eight percent of patients with prior infarct had fixed defects on SPECT, compared to 39% with PET. Sixty-one percent of patients with prior infarct had PET perfusion defects which exhibited 'reflow' or normal rubidium-82 tracer uptake (p < 0.05 vs. SPECT). Similar results were seen in patients without prior infarct (26% fixed defects on SPECT vs. 12% for PET, p < 0.05). Regional analysis showed that 57% of fixed SPECT defects corresponded to PET defects with reflow or normal rubidium-82 uptake, while 78% of 'fixed' PET defects corresponded to fixed SPECT defects. PET reflow and normal rubidium-82 uptake in sites of fixed thallium-201 SPECT perfusion defects suggest that imaging modalities employing separate tracer injections at rest and after stress, such as rubidium-82 PET, may be more specific in the assessment of myocardial viability, especially in patients with prior myocardial infarction.     

Asymmetry of the calves in the assessment of patients with suspected acute pulmonary embolism

PURPOSE: The purpose of this investigation was to evaluate measured asymmetry of the calves in the assessment of patients with suspected pulmonary embolism (PE). METHODS: Patients randomized for pulmonary angiography in the collaborative study of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) were evaluated. Only patients in whom the circumference of the calves was measured were included in this evaluation of PIOPED data. Among these, 232 had angiographically diagnosed PE and 446 had no PE by angiography. For purposes of comparison, measurements of the calves also were made in a nonrandomized current cohort of 101 healthy subjects. All calf measurements were made 10 cm below the tibial tuberosity. RESULTS: Asymmetry in the circumference of the calves of 1 cm or more was measured in 101 of 232 or 44% (95% confidence interval [CI], 37 to 51%) with PE, 176 of 446 or 39% (95% CI, 34 to 44%) without PE, and in 6 of 101 or 6% (95% CI, 1 to 11%) control subjects (PE vs control subjects, p < 0.001; subjects without PE vs control subjects, p < 0.001; PE vs no PE, p = NS). Among patients with PE, the addition of calf asymmetry of 1 cm or more to qualitative signs of deep venous thrombosis increased the prevalence of a detectable abnormality of the lower extremities from 62 of 232 or 27% (95% CI, 21 to 33%) to 129 of 232 or 56% (95% CI, 49 to 63% [p < 0.001]). CONCLUSION: Asymmetry of the calves of 1 cm or more is abnormal. Such asymmetry of the calves did not distinguish between patients with PE and those with no PE. When considered in proper perspective with other nonspecific signs and symptoms in patients with suspected acute PE, however, subtle calf asymmetry may call attention to the possibility of thromboembolic disease. The observation of subtle asymmetry may indicate a need for noninvasive diagnostic tests of the lower extremities to determine whether deep venous thrombosis is present.     

On the incidence of renal vein thrombosis in the nephrotic syndrome

Forty-eight patients with nephrotic syndrome were evaluated prospectively; the studies included inferior venacavagrams and ventilation perfusion lung scans. Eleven patients were found to have renal vein thrombosis (RVT). Eight of 21 patients with membranous glomerulonephritis (MGN) or membranoproliferative glomerulonephritis (MPGN) has RVT (38%). Clinical, laboratory, and pathological findings were not different among those patients with MGN and MPGN whether RVT was present or not. Patients with diabetic nephropathy or lupus nephritis did not have RVT. There was a high incidence of other thromboembolic phenomena as well as asymptomatic perfusion defects demonstrated by the lung scan, especially in patients with MGN or MPGN. These data suggest the disease process underlying the nephrotic syndrome may play a paramount role in the genesis of RVT or thromboembolic phenomena.     

Bilateral pulmonary artery aneurysms in a patient with Behcet syndrome: evaluation with radionuclide angiography and V/Q lung scanning

The case of a 14-year-old girl with Behcet syndrome is described. Besides painful and recurrent oral ulcerations, the patient had a cough and intermittent hemoptysis. The initial chest roentgenogram revealed bilateral parahilar opacities. CT and MRI scans of the thorax showed bilateral thrombosing aneurysms of the pulmonary arteries. Pulmonary blood flow imaging was performed after technegas ventilation lung scanning and Tc-99m MAA injection using a first-pass radionuclide angiography procedure. Altered blood flow in the left pulmonary artery was shown. Bilateral and well-defined ventilation/perfusion mismatched areas suggested a high probability of pulmonary embolism. Little additional information was obtained on subsequent contrast pulmonary angiography. The high incidence of pulmonary artery hypertension and associated vascular injury risk makes pulmonary angiography an unsafe procedure in patients with pulmonary Behcet syndrome. The need for pulmonary angiography could be obviated in such cases with the use of high-precision MRI and ventilation/perfusion lung scanning, including radionuclide pulmonary angiography.     

Efficacy of a low molecular weight heparin administered intravenously or subcutaneously in comparison with intravenous unfractionated heparin in the treatment of deep venous thrombosis. Certoparin-Study Group

BACKGROUND: The main objective of the study presented was to test if thrombus regression can be improved by treatment with an intravenously or subcutaneously administered low molecular weight heparin (LMWH). Patients with acute deep vein thrombosis were randomly assigned to receive either intravenous UFH (131 patients), intravenous (i.v.) LMWH (128 patients), or 8000 IU of the same LMWH bid subcutaneously (s.c.) (128 patients). All patients were treated with heparin for 14 to 16 days. Vitamin-K-antagonist prophylaxis was started between Day 12 and Day 14 after enrollment into the study. METHODS: Phlebographies and perfusion/ventilation lung scans were performed at baseline and on Days 12 to 16. Primary endpoint of the study was a reduction of the phlebographic Marder score. Secondary endpoints were recurrent thrombosis and pulmonary embolism (PE), major and minor bleedings and the rate of PE at inclusion and at the end of the study assessed by ventilation/perfusion scans. RESULTS: The Marder score improved by at least 30% in 32.4% (95% CI: 22.6 ... 42.2) of the patients receiving UFH, in 34.0% (95% CI: 24.9 ... 44.0) receiving LMWH i.v. and in 42.6% (95% CI: 32.8 ... 52.8) treated with the low molecular weight heparin s.c. The difference between LMWH s.c. and UFH was 10.2% (95% CI: -3.7% ... +24.5%) (p = 0.11). PE with clinical signs confirmed by objective methods occurred in three patients of the UFH group, one of whom died and was not observed in patients of the i.v. or s.c. LMWH-groups. During the first 15 days no patient receiving UFH or i.v. LMWH, and one patient on s.c. LMWH had a recurrent thrombosis. Major bleedings were observed in four patients receiving i.v. UFH compared to nine patients on i.v. LMWH (one of these patients died) and one patient on s.c. LMWH. Perfusion ventilation lung scans were obtained from 287 patients at baseline and from 246 patients on Days 12-16. PE, defined according to PIOPED-criteria as intermediate or high probability scans, was observed in 38.0% of the patients entering the study and in 18.3% on Days 12 to 16. New asymptomatic PE occurred less frequently in the groups on LMWH (7.1%, 7.5%, respectively) than in the UFH-group (12.6%) (not significant). CONCLUSIONS: S.c. treatment with a LMWH (certoparin) (b.i.d.) is at least as effective as UFH i.v. The hypothesis of increased efficacy of subcutaneous LMWH in resolving venous thrombi will have to be confirmed by an independent study comparing s.c. LMWH with UFH. The i.v. continuous infusion of the LMWH for 12 to 16 days does not result in a higher venous re-opening rate than intravenous standard heparin.     

Rest or redistribution thallium myocardial imaging for resting myocardial perfusion: a detailed comparison with regional wall motion

Redistribution thallium-201 (201T1) imaging is the most common method of assessing resting myocardial perfusion. However, the equivalence of a redistribution image and a separate rest injection is unclear. Although the presence of a defect on rest imaging has normally been equated with the presence of a myocardial infarction, it has recently been shown that a significant proportion of fixed defects on exercise-redistribution 201T1 actually represent areas of viable myocardium. This study was a detailed comparison of rest and redistribution imaging in 30 patients undergoing routine exercise 201T1 scanning for the assessment of coronary artery disease. A small dose (15 MBq) of 201T1 was administered at rest following the imaging in three standard planar views. Similar stress images were acquired using a further 50-55 MBq of 201T1 administered at peak effort. Redistribution images were acquired 3-4 h later and equilibrium blood pool ventriculography performed using in vivo labelling with 600 MBq 99Tcm-pertechnetate. Of 150 abnormal segments on the exercise scans, 74 (49%) were identified as being reversible on the redistribution scans and 58 (39%) on the rest images. Only 39 (53%) of these reversible defects were identified on both the redistribution and rest scans. Only 41% of the fixed defects on the redistribution images (32% of fixed defects on the rest images) had abnormal wall motion. Therefore, rest and redistribution images are not equivalent. Both rest and redistribution images significantly overestimate myocardial infarction. This may have significant effects on patient selection for revascularization procedures and therefore all patients having perfusion scintigraphy should also have additional assessment of regional wall motion to allow accurate classification of the functional status of myocardial segments.     

Prediction of outcome of patients with life-threatening ventricular arrhythmias treated with automatic implantable cardioverter-defibrillators using SPECT perfusion imaging

BACKGROUND: In the present study, we examined the predictors of outcome of 103 patients with coronary artery disease and left ventricular dysfunction who had life-threatening ventricular arrhythmias and were treated with implantable cardioverter-defibrillators with the use of single-photon emission computed tomography (SPECT). METHODS AND RESULTS: During a mean follow-up of 29 months, there were 29 cardiac deaths. In comparison with patients who died, survivors had less diabetes mellitus (45% versus 19%, P < .007), higher left ventricular ejection fraction (23 +/- 9% versus 27 +/- 11%, P = .04), and fewer perfusion defects as determined with stress SPECT (15 +/- 5 versus 12 +/- 5, P < .004). Most of the perfusion defects were fixed, indicative of scarring; the extent of reversible defects did not differ (2 +/- 3 in survivors and 3 +/- 4 in nonsurvivors). Multivariate Cox survival analysis identified the number of fixed defects as the only independent predictor of death (chi 2 = 10, P = .002). There were six deaths among 42 patients (14%) with < 8 fixed defects compared with 23 deaths among 61 patients (38%) with > or = 8 defects (P = .005). The 4-year survival was better in patients with < 8 segmental fixed defects than in those with > or = 8 fixed defects (80% versus 36%) (chi 2 = 8, P = .005). CONCLUSIONS: The myocardial perfusion pattern is an important determinant of outcome in patients with life-threatening ventricular arrhythmias who are treated with a implantable cardioverter-defibrillator. The extent of scarring separates patients into high- and low-risk groups with a 2.7-fold difference in death rate.     

The prognostic factors for early mortality and for total or partial gammagraphic resolution in venous thromboembolic disease

Our objective was to investigate possible factors implicated in either early death from or scintigraphic resolution of pulmonary embolism. To that end we conducted a retrospective study of 116 patients with either a high likelihood of pulmonary thromboembolism (PTE) diagnosed by scintiscan or with a fair probability of PTE by scintiscan accompanied by a positive phlebograph. The images were taken upon admission, at 7 days, 10 days and 6 months. The factors analyzed were age, sex, trauma, immobility, surgery, obesity, hemiplegia, venous insufficiency, cardiopulmonary disease, neoplasia, chest X-ray and ECG alterations, D(A-a)O2 and size of perfusion defects upon admission and 7 to 10 days later. We performed single-variable analyses and multiple logical regression analyses using perfusion defect at 6 months as the dependent variable. The early mortality rate (13%) was higher in patients with neoplasms, a larger alveolar-arterial index and greater perfusion defects upon admission. Scintiscans became normal in 28%. Multivariate analysis to predict total or partial resolution at 6 months showed that size of perfusion defects at 7 to 10 days was the best predictive factor. A cutoff point was calculated by analyzing the ROC for this factor. Thus, when the defect at 7 to 10 days was equal to or greater than 1 segment, the probability of residual defects remaining after 6 months was twice as great (sensitivity 83%, specificity 57%). In conclusion, early death was more likely in PTE patients with neoplasms, larger defects upon admission and greater alveolar-arterial difference. Scintigrams showed resolution 6 months after admission in 28%. The size of perfusion defects 7 to 10 days after admission was the factor that best predicted total of partial resolution at 6 months.     

Outcome of patients with total colonic ischemia

PURPOSE: In this study, we sought to determine the outcome of patients with ischemic colitis, comparing patients with segmental disease with those with total colonic ischemia. METHODS: Patients with the diagnosis of ischemic colitis over the past six years were selected and reviewed for demographics, presenting symptoms, diagnosis, and treatment. RESULTS: Forty-three consecutive patients with ischemic colitis were identified and were grouped into those with segmental ischemic colitis and total colonic ischemia. Mean age was 68.8 years; 28 of 43 patients (65 percent) were males. Diagnosis was established by colonoscopy in 31 of 43 patients (72 percent), whereas in the remainder, diagnosis was made in the operating room. Ischemic colitis developed in the hospital in 17 of 43 patients (40 percent) during admission for an unrelated illness. In 6 of 43 (14 percent) of these patients, ischemic colitis developed following surgery. Thirty-one of 43 patients (72 percent) were found to have segmental colitis; 11 of 31 patients (35 percent) were successfully managed nonoperatively. Segmental colitis was present in 31 of 43 patients (72 percent), and 12 of 31 (35 percent) of these patients were successfully managed nonoperatively. In the patients with segmental colitis who required surgery, the 30-day mortality rate was 22 percent. Among 12 of 17 patients (71 percent) with segmental ischemia treated by resection and stoma, 9 of 12 (75 percent) underwent eventual stoma closure. All 12 patients with total colonic ischemia required surgery, and 9 of 12 patients (75 percent) died. CONCLUSION: Ischemic colitis occurs commonly during an unrelated hospital admission and following previous surgery. Most patients treated by resection and stoma undergo stoma closure. Total colonic ischemia carries a worse prognosis than segmental colonic ischemia.     

A comparative analysis of pulmonary perfusion scans with pulmonary angiograms

Pulmonary angiograms and pulmonary lung perfusion scans on 162 patients with pulmonary embolism were comparatively analyzed. Among the expert angiographic panel members who independently evaluated the studies there was consistent agreement on the diagnosis, size of the emboli, and severity. Consistency of agreement among the expert pulmonary lung perfusion scan panelists was considerably less. These data demonstrate that, in addition to the lack of specificity of the lung perfusion scan for the diagnosis of pulmonary thromboemboli, there is a considerable problem of interpretation in this patient population.     

Role of radionuclide venography in the detection of proximal deep vein thrombosis: a prospective comparative study

The role of radionuclide techniques in the investigation of thromboembolic disease has been re-evaluated. Forty-eight patients suspected of having embolic lung disease (PE) or deep venous thrombosis (DVT) were studied prospectively and investigated with radionuclide venography and ventilation/perfusion lung scintigraphy. Thirty-two also underwent contrast venography and peripheral 99Tcm-labelled red blood cell scintigraphy. Both radionuclide techniques were compared to each other and against the 'gold-standard'. The overall agreement and disagreement rates were 89 and 11% for radionuclide venography and 88 and 12% for radionuclide blood pool venography. The overall sensitivity and specificity were 90 and 73% for radionuclide venography and 88 and 82% for radionuclide blood pool venography. The blood pool technique did not perform better than radionuclide venography which was valuable in the detection of DVT and confirmation of PE. Radionuclide venography appears useful especially in patients suspected of having PE and DVT.     

A comparison of noninvasive positive-pressure ventilation and conventional mechanical ventilation in patients with acute respiratory failure

BACKGROUND AND METHODS: The role of noninvasive positive-pressure ventilation delivered through a face mask in patients with acute respiratory failure is uncertain. We conducted a prospective, randomized trial of noninvasive positive-pressure ventilation as compared with endotracheal intubation with conventional mechanical ventilation in 64 patients with hypoxemic acute respiratory failure who required mechanical ventilation. RESULTS: Within the first hour of ventilation, 20 of 32 patients (62 percent) in the noninvasive-ventilation group and 15 of 32 (47 percent) in the conventional-ventilation group had an improved ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen (PaO2:FiO2) (P=0.21). Ten patients in the noninvasive-ventilation group subsequently required endotracheal intubation. Seventeen patients in the conventional-ventilation group (53 percent) and 23 in the noninvasive-ventilation group (72 percent) survived their stay in the intensive care unit (odds ratio, 0.4; 95 percent confidence interval, 0.1 to 1.4; P=0.19); 16 patients in the conventional-ventilation group and 22 patients in the noninvasive-ventilation group were discharged from the hospital. More patients in the conventional-ventilation group had serious complications (66 percent vs. 38 percent, P=0.02) and had pneumonia or sinusitis related to the endotracheal tube (31 percent vs. 3 percent, P=0.003). Among the survivors, patients in the noninvasive-ventilation group had shorter periods of ventilation (P=0.006) and shorter stays in the intensive care unit (P=0.002). CONCLUSIONS: In patients with acute respiratory failure, noninvasive ventilation was as effective as conventional ventilation in improving gas exchange and was associated with fewer serious complications and shorter stays in the intensive care unit.