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Biomedical subjects

A B Nichols

Publications and source records attributed to A B Nichols.

At least 37 records · Page 2Linked to original sources
PubMed1981

Percutaneous intraaortic balloon insertion in patients with aortoiliac disease.

A new technique for percutaneous insertion of intraaortic balloon catheters in patients with tortuous or narrowed external iliac arteries is described. This method uses a long (45 cm) 12F sheath, which extends up to the descending aorta and protects the iliac artery and aorta from injury during insertion of the balloon catheter. Insertion of intraaortic balloon catheters was not possible by conventional percutaneous technique in six patients with severe acute myocardial ischemia. Use of the long sheath approach permitted rapid and successful institution of circulatory support in these patients.

Adult↗
PubMed1980

Percutaneous intraaortic balloon insertion.

A new single chambered percutaneous intraaortic balloon has been constructed around a central guidewire. The balloon can be wrapped around the guidewire, enabling its insertion into the femoral artery through a 12F sheath inserted with the conventional Seldinger technique. Percutaneous intraaortic balloon insertion has been performed in 27 patients (mean age 58 years) for a variety of medical and surgical indications. Percutaneous balloons could not be advanced into the aorta in two patients (7.4 percent) with severe bilateral aortoiliac occlusive disease. In all 25 patients undergoing intraaortic balloon pumping satisfactory circulatory support was achieved, and 21 (84 percent) of the patients survived to be discharged from the hospital. The mean duration of intraaortic balloon pumping was 3.5 days. Percutaneous intraaortic balloon insertion requires less than 5 minutes and has been successfully performed in the cardiac catheterization laboratory, coronary care unit, operating room and recovery room. After direct balloon removal, external pressure was applied for 30 minutes. No patient experienced hematoma of the groin, aortic dissection, compromised distal pulses or late wound complications. Percutaneous balloon insertion permits the rapid institution of circulatory support and broadens the medical and surgical applications of intraaortic balloon pumping.

Adult↗
PubMed1980

Detection of pulmonary emboli by positron imaging of inhaled 15O-labeled carbon dioxide.

A new radionuclide approach to the scintigraphic detection of pulmonary emboli is described. This method utilizes cyclotron-produced C15O2, administered by inhalation, for rapid labeling of pulmonary blood. Following clearance of oxygen-15 from the lungs by pulmonary blood flow, focal retention of activity results from stasis of blood distal to emboli. On serial positron imaging, focally retained activity delineates embolized pulmonary segments and identifies the location and extent of pulmonary emboli. In animal studies this positron scintigraphic method detected emboli as small as 2 mm in diameter. In patients with suspected pulmonary emboli, this approach appears to be both sensitive and specific. Clinically, C15O2 inhalation imaging is most useful for the detection of pulmonary emboli in patients with chronic lung disease or congestive heart failure. It is rapid and safe and can be easily repeated, with minimal radiation exposure, for determining resolution rates of emboli and for assessing residual blood flow distal to emboli.

Animals↗
PubMed1980

Quantification of myocardial infarction by computer-assisted positron emission tomography.

The accuracy of three-dimensional transverse section positron emission imaging for quantification of myocardial infarction size was validated and compared with the accuracy of two dimensional planar positron imaging. After induction of acute anterior myocardial infarction in anaesthetised dogs, gallium-68 albumin microspheres were injected into the left atrium. Planar and transverse section images of the thorax were obtained with a multicrystal positron camera. After staining with tetrazolium tetrachloride injected intravenously, the hearts were excised, sectioned manually, and planar imaging repeated. Each myocardial infarction was clearly delineated by transverse section imaging with high contrast ratios (mean 0.68 +/- 0.02 SEM); planar imaging identified seven of nine infarcts but with lower contrast ratios (0.24 +/- 0.04; P < 0.001). The volume of infarcted myocardium determined from transverse section images correlated well with true infarct volume (r = 0.94); whereas planar images poorly predicted infarct size (r = 0.63). Thus, computer-assisted transverse section positron imaging provides in vivo localisation of microsphere distribution for improved radioisotopic quantification of myocardial infarction.

Animals↗
PubMed1979

Resolution rates of pulmonary embolism assessed by serial positron imaging with inhaled O-15-labeled carbon dioxide.

Embolic obstruction of pulmonary blood flow results in delayed regional clearance of inhaled C15O2. Focally retained C15O2 appears as zones of increased O-15 activity on serial positron scintigrams, which show the locations of occluded pulmonary segments. Inhalation of C15O2, with serial imaging by a multicrystal positron camera, was used to locate and assess the magnitude of occluded pulmonary segments in eight patients with arteriographically documented pulmonary emboli. The imaging with C15O2 inhalation was repeated after 1 wk of i.v. heparin therapy to evaluate the ability of this technique to determine resolution rates of pulmonary emboli during anticoagulant therapy. In all patients, zones of increased C15O2 activity corresponded with sites of emboli identified arteriographically. After 1 wk of continuous heparin therapy, zones of focally retained C15O2 were totally resolved in three patients, diminished in four, and unchanged in one. The regional pulmonary clearance rate of C15O2 was delayed over embolized pulmonary segments in all patients (men clearance half-time = 42.2 sec +/- 11.2 s.e.m.) and improved after heparin therapy (13.9 +/- 3.9 sec; p less than 0.05). Serial C15O2 inhalation imaging is a rapid noninvasive radionuclide technique for detection of pulmonary emboli. It can be repeated at frequent intervals to assess the resolution of emboli during anticoagulant therapy.

Adult↗
PubMed1978

Scintigraphic detection of pulmonary emboli by serial positron imaging of inhaled 15O-labeled carbon dioxide.

Inhaled radioactive carbon dioxide is retained in pulmonary blood distal to embolic obstruction and appears as an area of increased radioactivity that delineates the site and magnitude of the affected zone. The scintigraphic detection of pulmonary emboli by serial imaging of inhaled carbon dioxide labeled with cyclotron-produced 15O2 was evaluated in 27 patients undergoing conventional pulmonary ventilation/perfusion imaging and pulmonary arteriography. Fifteen patients proved to have pulmonary emboli on arteriography. Sensitivity (87%) and specificity (92%) rates for inhalation imaging were superior to those of conventional ventilation/perfusion imaging (P less than 0.05). Clearance of 15O2 activity was markedly delayed over embolized pulmonary segments (mean half time of 47.0 +/- 11.1 seconds [S.E.M.]) in comparison to normal segments (mean of 3.6 +/- 0.08 seconds; P less than 0.001). Pulmonary imaging by this method provides an approach to the detection of pulmonary emboli that is relatively sensitive and specific and permits analysis of persisting perfusion in embolized pulmonary segments. A major practical limitation, however, is the necessity of a nearby cyclotron.

Adult↗
PubMed1978

Detection of experimental pulmonary emboli in dogs by sequential positron imaging after inhalation of 15O-carbon dioxide.

After inhalation, C15O2 (T1/2 = 2 minutes) rapidly diffuses into pulmonary blood and is cleared from the lungs within 10 seconds. The purpose of this study was to determine whether impaired clearance of inhaled C15O2 from oligemic zones, distal to areas of obstructed pulmonary blood flow, could be detected by serial pulmonary imaging with a positron camera. Experimental obstruction of branches of the pulmonary artery was induced in 19 anesthetized dogs by inflation of balloon-tipped catheters (8-12 mm in diameter), injection of radiopaque silicone spheres (0.5-4.0 mm), and embolization with barium-impregnated autologous blood clots (1-5 mm) via the right external jugular vein. After a single bolus injection of 2 mCi of C15O2 into the endotracheal tube, serial lung images of 15O activity were obtained over 60-180 seconds. Obstruction of pulmonary arterial branches resulted in visualization of discrete zones of impaired 15O clearance which varied in area with catheter diameter. Location and size of these zones were confirmed by repeat imaging after direct injection of 15O-labeled blood through the distal catheter lumen. In dogs receiving autologous clots (n = 8), similar zones of impaired 15O clearance were consistently imaged, and single emboli as small as 2 mm in diameter produced regions of retained 15O activity. Zones of retained 15O activity corresponded to the location of radiopaque emboli on chest radiographs. This study introduces a new technique of radionuclide imaging for detection of pulmonary emboli that is noninvasive, safe, sensitive, and repeatable at short intervals.

Animals↗
PubMed1978

Left ventricular function during intra-aortic balloon pumping assessed by multigated cardiac blood pool imaging.

The effectiveness of intra-aortic balloon pumping in augmenting ventricular performance during acute myocardial ischemic syndromes was determined by noninvasive multigated cardiac blood pool imaging. Nine patients with unstable angina refractory to medical therapy and nine patients with acute myocardial infarction complicated by congestive heart failure were studied on and off intra-aortic balloon pumping (IABP). End-diastolic and end-systolic volumes were significantly reduced by IABP in both unstable angina and myocardial infarction. Analysis of ventricular wall motion demonstrated improved segmental contraction during IABP in all seven unstable angina patients with regional wall motion abnormalities. No significant improvement in regional contraction was observed in the nine patients with acute myocardial infarction. During IABP, percent ventricular asynergy decreased significantly (28.2%; P < 0.01) among patients with unstable angina but demonstrated no significant fall (4.4%; P = NS) for patients with myocardial infarction. Thus, IABP enhances contraction of ischemic but not infarcted myocardium and effectively improves ventricular function by reducing end-diastolic and end-systolic volumes.

Adult↗
PubMed1976

Independence of serum lipid levels and dietary habits. The Tecumseh study.

Serum cholesterol and triglyceride levels were correlated with dietary habits of 4,057 adult participants in a prospective epidemiologic survey of cardiovascular disease in Tecumseh, Mich. Frequency of consumption of 110 different food items was determined for each participant and average weekly consumption rates of foods high in fat, sugar, starch, and alcohol content were calculated. Frequency of consumption of these nutrients was then correlated with serum cholesterol and triglyceride levels of individual subjects. Serum cholesterol and triglyceride values were not positively correlated with selection of dietary constituents. Positive correlations between serum lipid levels and adiposity were statistically significant. These findings suggest that serum cholesterol and triglyceride levels among Americans are more dependent on degree of adiposity than on frequency of consumption of fat, sugar, starch, or alcohol.

Adult↗
PubMed1976

Daily nutritional intake and serum lipid levels. The Tecumseh study.

To determine the influence of diet on serum cholesterol and triglyceride levels among adults, 24-hr dietary recall interviews were conducted among 957 men and 1,082 women resident in the community of Tecumseh, Michigan. Trained interviewers obtained detailed description of all foods consumed during 24 hr before venipuncture for lipid determination. Using a list of nutritional composition of 2,706 foods prepared from standard references, nutritionists determined quantities of all nutrients common to the American diet which were consumed by each participant according to a 24-hr diet record. For analysis, men and women were grouped into lower middle, and upper tertiles according to serum cholesterol and triglyceride levels. The mean daily consumption of each dietary component was virtually identical in all tertiles for men and women but differed between sexes. Cholesterol and triglyceride levels were unrelated to quality, quantity, or proportions of fat, carbohydrate, or protein consumed in the 24-hr recall period.

Adult↗