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Biomedical subjects

G Coates

Publications and source records attributed to G Coates.

At least 73 records · Page 4Linked to original sources
PubMed1988

Pulmonary embolism in outpatients with pleuritic chest pain.

Pleuritic chest pain is a frequent complaint in patients coming to the emergency room, but the proportion of such patients with pulmonary embolism is uncertain. In a prospective study, we evaluated the diagnostic outcomes in 173 consecutive patients who came to the emergency room with pleuritic chest pain. Pulmonary embolism, as demonstrated by angiography or autopsy, was present in 36 (21%). The need for objective testing is clearly indicated by our finding that the sensitivity (85%) and specificity (37%) of predetermined clinical variables for pulmonary embolism were insufficient to allow a definitive treatment decision. Optimal sensitivity and specificity are obtained by using pulmonary angiography in combination with lung scanning. The proportion of patients requiring angiography is substantially reduced, from 43% to 26%, without significant loss of accuracy, if ventilation imaging and impedance plethysmography are used together with perfusion scanning.

Adult↗
PubMed1987

Pulmonary haemodynamics during exercise after low and high doses of acetylsalicylic acid in sheep.

Despite comparable increases in cardiac output there is a greater reduction in pulmonary vascular resistance (PVR) in sheep during exercise than in dog or man. The mechanism for this marked reduction in PVR in sheep is unknown. To assess the role of arachidonic acid metabolites in producing this low PVR we measured the effect of intravenous acetylsalicylic acid (ASA, 10 mg/kg) on PVR at rest and during exercise in sheep. ASA caused a slight rise in resting PVR (p less than 0.05), but did not affect the exercise-induced decrease in PVR. High-dose ASA (100 mg/kg), presumably sufficient to block the lipoxygenase pathway produced the same responses as low-dose ASA which should only block the cyclo-oxygenase pathway. Products of the cyclo-oxygenase and lipoxygenase pathways which include vasodilator prostaglandins, have only a minor role in maintaining low pulmonary vascular resistance at rest and have no demonstrable role in the reduced PVR that occurs during exercise in sheep.

Animals↗
PubMed1987

Mechanisms of changes in nitrogen washout and lung volumes after saline infusion in humans.

This study was performed to determine the roles of increased intrathoracic blood volume and increased vagal tone in the changes in lung volume and nitrogen washout produced by saline infusion. In the first study, measurements of TLC, VC, FRC, ERV, and slope of phase III nitrogen washout (delta N2) were made on 8 subjects before, during, and after inflation of the leg compartments of medical anti-shock trousers (MAST). In the second study, 13 volunteers were infused intravenously with warm saline (30 ml/kg) for 30 min. Repeat measurements were made approximately 20 and 40 min after infusion. Each subject then received intravenously 0.03 mg/kg atropine, and measurements were repeated. In 7 of these subjects, a third study was performed in which the atropine was injected before saline infusion. Inflation of the MAST (see figures 5 and 6) caused a 1.9% decrease in VC, 5.3% decrease in FRC, and no change in delta N2. Saline infusion caused decreases in TLC, VC, and FRC (4.0, 3.1, and 10.1%, respectively) and a 15.0% increase in delta N2. Atropine reversed the change in delta N2 after saline infusion and prevented these changes when given prior to saline. Atropine had no effect on lung volumes whether given before or after saline infusion. We speculate from our data that saline infusion has 2 effects on the lung. One is a simple displacement of air by increased intravascular volume producing the reduction in lung volumes. The second is an increase in small airways resistance that is mediated by vagal reflex and blocked with atropine.

Adult↗
PubMed1987

111In-oxine platelet survivals in thrombocytopenic infants.

Thrombocytopenia is a common occurrence (20%) in sick neonates, but the causes have not been well studied. In this report we demonstrate that thrombocytopenia in the neonate is characterized by increased platelet destruction as shown by shortened homologous 111In-oxine-labeled platelet life spans. Thirty-one prospectively studied thrombocytopenic neonates were investigated by measuring the 111In-labeled platelet life span, platelet-associated IgG (PAIgG), and coagulation screening tests. In every infant, the thrombocytopenia was shown to have a destructive component since the mean platelet life span was significantly shortened to 65 +/- 6 (mean +/- SEM) hours with a range of one to 128 hours compared with adult values (212 +/- 8; range, 140 to 260; gamma function analysis). The platelet survival was directly related to the lowest platelet count and inversely related to both the highest mean platelet volume and duration of the thrombocytopenia. In 22 infants the percent recovery of the radiolabeled platelets was less than 50%, which suggested that increased sequestration also contributed to the thrombocytopenia. Infants with laboratory evidence of disseminated intravascular coagulation (n = 8) or immune platelet destruction evidenced by elevated levels of PAIgG (n = 13) had even shorter platelet survivals and a more severe thrombocytopenia compared with the ten infants in whom an underlying cause for the thrombocytopenia was not apparent. Full-body scintigraphic images obtained in 11 infants showed an increased uptake in the spleen and liver, with a spleen-to-liver ratio of 3:1. This study indicates that thrombocytopenia in sick neonates is primarily destructive, with a subgroup having evidence of increased platelet sequestration.

Blood Platelets↗
PubMed1987

Reversibility of increased intestinal permeability to 51Cr-EDTA in patients with gastrointestinal inflammatory diseases.

Intestinal permeability in adults with inflammatory gastrointestinal diseases was investigated by measuring the 24-h urinary excretion of orally administered 51Cr-EDTA. Eighty controls along with 100 patients with Crohn's disease, 46 patients with ulcerative colitis, 20 patients with gluten-sensitive enteropathy, and 18 patients with other diseases were studied. In controls, the median 24-h excretion was 1.34%/24 h of the oral dose. Patients with Crohn's disease (median 2.96%/24 h), ulcerative colitis (median 2.12%/24 h), and untreated gluten-sensitive enteropathy (median 3.56%/24 h) had significantly elevated urinary excretion of the probe compared to controls (p less than 0.0001). Increased 24-h urinary excretion of 51Cr-EDTA had a high association with intestinal inflammation (p less than 0.0001). Test specificity and sensitivity were 96% and 57%, respectively. A positive test has a 96% probability of correctly diagnosing the presence of intestinal inflammation, whereas a negative test has a 50% probability of predicting the absence of disease.

Adult↗
PubMed1987

Extrapulmonary radioactivity in lung permeability measurements.

The pulmonary clearance rate of aerosolized and deposited [99mTc]DTPA is used to assess pulmonary epithelial permeability to solutes. To evaluate whether it is necessary to correct these measurements for radioactivity in the chest wall and pulmonary vasculature five patients with no ventilation to one hemithorax were studied. After inhaling a submicronic aerosol of [99mTc]DTPA a gamma camera measured count rates over both hemithoraces for 20 min. The observed T1/2 for clearance from the normal hemithorax was 56 min (range 18-115 min), and when this was corrected for chest wall contribution (derived from the abnormal hemithorax) the average T1/2 was 52 min (range 17-107 min). To simulate infinitely permeable lungs we measured thoracic radioactivity in two adults and six children who were injected i.v. with a known amount of [99mTc]DTPA. The count rate over the thorax was only 8.1% (range 2.7%-11%) of that obtained when a similar amount of aerosolized [99mTc]DTPA was deposited in the lungs during a subsequent study. We conclude that it is not necessary to correct for nonpulmonary epithelial radioactivity during the measurement of [99mTc]DTPA clearance rate from the lungs.

Adult↗
PubMed1987

Ventilation scintigraphy with submicronic radioaerosol as an adjunct in the diagnosis of congenital lobar emphysema.

When clinical examination and routine chest x-ray do not adequately explain neonatal respiratory distress, lung scintigraphy using a submicronic aerosol particle may be most helpful. Three cases illustrating this point are presented. Discussion centers around the diagnosis of an atypical case of congenital lobar emphysema (CLE), and differentiating between CLE, foreign body aspiration and compensatory hyperinflation in neonates with respiratory distress. Conservative and surgical treatment options for CLE are also illustrated.

Administration, Inhalation↗
PubMed1986

Measurement of pulmonary epithelial permeability with 99mTc-DTPA aerosol.

The rate at which inhaled aerosol of 99mTc-diethylenetriamine pentaacetate (DTPA) leaves the lung by diffusion into the vascular space can be measured with a gamma camera or simple probe. In normal humans, 99mTc-DTPA clears from the lung with a half time of about 80 minutes. Many acute and chronic conditions that alter the integrity of the pulmonary epithelium cause an increased clearance rate. Thus cigarette smoking, alveolitis from a variety of causes, adult respiratory distress syndrome (ARDS), and hyaline membrane disease (HMD) in the infant have all been shown to be associated with rapid pulmonary clearance of 99mTc-DTPA. Rapid clearance is also promoted by increased lung volume and decreased surfactant activity. Although the mechanism of increased clearance in pathological states is not known, the 99mTc-DTPA lung-clearance technique has great potential clinically, particularly in patients at risk from ARDS and HMD and in the diagnosis and follow-up of alveolitis.

Aerosols↗
PubMed1986

111Indium-labelled polymorphonuclear leucocyte scans in rheumatoid arthritis--an important clinical cause of false positive results.

The presence of rheumatoid arthritis in patients undergoing 111indium-labelled polymorphonuclear leucocyte scanning represents a source of possible diagnostic confusion. In such patients, the labelled cells frequently accumulate over the caecum and ascending colon, despite the absence of obvious pathology of the large bowel. The aetiology of this effect is unknown.

Abdomen↗
PubMed1986

Effect of isoproterenol or exercise on pulmonary lymph flow and hemodynamics.

Experiments were performed to determine whether different methods of increasing cardiac output would have similar effects on lung lymph flow, and to assess the contribution of the microvasculature (fluid-exchanging vessels) to the total calculated pulmonary vascular resistance. Yearling unanesthetized sheep with chronic vascular catheters and lung lymph fistulas underwent intravenous infusions of isoproterenol at 0.2 micrograms X kg-1. min-1 (n = 8) or were exercised on a treadmill (n = 16). Both isoproterenol and exercise increased cardiac output, lowered calculated total pulmonary and systemic vascular resistances, and had no effect on the calculated pulmonary microvascular pressure. Isoproterenol infusions did not affect lung lymph flow, whereas exercise increased lung lymph flow in proportion to the increase in cardiac output. We conclude that 1) the sheep has a different pulmonary hemodynamic response to exercise than dogs and man, 2) the microvasculature is recruited during exercise-induced but not isoproterenol-induced increases in cardiac output, and 3) the microvasculature represents only a small proportion of the total calculated pulmonary vascular resistance.

Animals↗
PubMed1986

Effect of inspiratory resistance and PEEP on 99mTc-DTPA clearance.

Experiments were performed to determine the effect of markedly negative pleural pressure (Ppl) or positive end-expiratory pressure (PEEP) on the pulmonary clearance (k) of technetium-99m-labeled diethylenetriaminepentaacetic acid (99mTc-DTPA). A submicronic aerosol containing 99mTc-DTPA was insufflated into the lungs of anesthetized intubated sheep. In six experiments k was 0.44 +/- 0.46% (SD)/min during the initial 30 min and was unchanged during the subsequent 30-min interval [k = 0.21 +/- 12%/min] when there was markedly increased inspiratory resistance. A 3-mm-diam orifice in the inspiratory tubing created the resistance. It resulted on average in a 13-cmH2O decrease in inspiratory Ppl. In eight additional experiments sheep were exposed to 2, 10, and 15 cmH2O PEEP (20 min at each level). During 2 cmH2O PEEP k = 0.47 +/- 0.15%/min, and clearance increased slightly at 10 cmH2O PEEP [0.76 +/- 0.28%/min, P less than 0.01]. When PEEP was increased to 15 cmH2O a marked increase in clearance occurred [k = 1.95 +/- 1.08%/min, P less than 0.001]. The experiments demonstrate that markedly negative inspiratory pressures do not accelerate the clearance of 99mTc-DTPA from normal lungs. The effect of PEEP on k is nonlinear, with large effects being seen only with very large increases in PEEP.

Airway Resistance↗
PubMed1986

Effect of exercise on lung lymph flow in unanesthetized sheep with increased pulmonary vascular permeability.

To investigate the effect of increased cardiac output on lung water and solute movement in abnormally permeable lungs, experiments were performed in sheep with chronic vascular catheters and lung lymph fistulas. Pulmonary permeability was increased by infusing air microemboli intravenously for 3 h. Once stable lymph flow was observed after stopping the air embolization sheep were either exercised on a treadmill to increase cardiac output (n = 10) or merely continuously monitored (control experiments, n = 6). In control experiments, lung lymph flow remained at markedly elevated but stable values. Sheep exercised for a median time of 45 min. Cardiac output increased 85%, whereas lung lymph flow, in terms of baseline flow rates, increased 296%. The lymph to plasma concentration ratio for total protein was unchanged, and left atrial pressure remained stable and normal during exercise. During exercise, pulmonary arterial pressure increased by 3 mm Hg. The data, when compared with previous observations in normal sheep, demonstrate that exercise-induced increases in cardiac output result in disproportionate increases in lung lymph flow when pulmonary vascular permeability is increased.

Animals↗
PubMed1986

Pulmonary deposition sites of an inhaled radiolabeled submicronic aerosol.

The clearance rate of aerosolized and deposited 99mtechnetium diethylenetriamine pentacetate provides an index of lung epithelial permeability. However, the location of the epithelium being assessed is uncertain. We determined the percentage of submicronic aerosol deposited on ciliated and nonciliated airways in healthy and damaged lungs using 99mTc-sulphur (99mTc-S) colloid. Colloidal particles can be cleared by mucociliary transport but not through the epithelium. Piglets aged 12-72 h, weighing 0.7-3.3 kg (average 1.6 kg) were anesthetized and underwent endotracheal intubation. 99mTc-S labeled submicronic aerosol (Syntevent II) was collected in anesthetic bags and either inhaled spontaneously (n = 4), or insufflated by hand (n = 5) at 30 breaths per min and a peak airway pressure of 15 cm H2O. Piglets were immediately extubated and scanned on a gamma camera. Twenty-four h later a repeat scan was performed. The residual radioactivity represents the amount of aerosol deposited on nonciliated airways. In six other piglets pulmonary damage was produced by an intravenous infusion of air microemboli for 2 to 3 h (0.14 to 0.38 ml/min). The maximal decrease in PaO2 while breathing room air ranged from 24-59 mm Hg. During the last 15 min of infusion they were intubated, insufflated by hand with the 99mTc-S aerosol, and scanned as above. The results demonstrate that approximately three-fourths of the submicronic aerosol is deposited distally to ciliated airways in both healthy and damaged newborn piglet lungs. This suggests that the clearance rate of 99mtechnetium diethylenetriamine pentacetate predominantly reflects epithelial permeability of terminal lung units when a submicronic aerosol is used for delivery to the lung.

Aerosols↗
PubMed1986

The contribution of lymphatic drainage to the clearance of inhaled 99mTc-DTPA from the lungs.

When inhaled as an aerosol, 99mTc labelled diethylene triamine pentacetate (99mTc-DTPA) moves rapidly from the airspace to the vascular space. The rate at which it leaves the lungs is being used to measure the integrity of the pulmonary epithelium. In order to determine what part the lymphatic system plays in the clearance of 99mTc-DTPA from the lungs, we measured the rate of appearance in plasma and lymph of inhaled 99mTc-DTPA and intravenously injected Indium-113m labelled (113mIn-DTPA) in 5 sheep with chronic lung lymph fistalae. Inhaled 99mTc-DTPA was detected in the plasma and lymph after 1 minute. This suggests that the inhaled sub-micronic aerosol of 99mTc-DTPA was deposited predominately in a region of the lung with a large vascular surface area, ie. the terminal lung units. The lymph/plasma concentration (1/p) ratio for injected 113mIn-DTPA became greater than 1 by 4 minutes whereas the 1/p ratio for inhaled 99mTc-DTPA did not reach 1 until 25 minutes. This suggests that lymph drainage has very little part to play in the clearance of inhaled 99mTc-DTPA from the lungs.

Aerosols↗
PubMed1986

The la-z-boy position and muscle blood flow in the lower limbs.

Patients are encouraged to sit upright in bed after surgery in order to reduce the risk of pulmonary complications. Adjusting the hospital bed to place the patient in the la-z-boy position minimizes the work of nursing staff in maintaining the patient in an upright position. This study was designed to answer concerns that the la-z-boy position might impair muscle blood flow in the lower limbs and thereby predispose patients to venous thrombosis. In 11 healthy volunteers the authors measured and compared blood flow from the gastrocnemius muscle in the la-z-boy position and in the more conventional straight-leg position. There was no clinically or statistically significant difference in blood flow in the two positions.

Adult↗