Isotope lung imaging

The contribution of isotope imaging to the investigation of respiratory disease has been primarily limited to the detection of ventilation and perfusion abnormalities and the investigation of inflammation or cancer. In recent years, there has been a growing interest in the metabolic function of the lung and in measurements of alveolar capillary permeability in a variety of conditions. This review will deal with these newer applications of isotope techniques in the lung in addition to developments in ventilation-perfusion imaging.

Ventilation-perfusion lung scanning and the diagnosis of pulmonary embolism: improvement of observer agreement by the use of a lung segment reference chart

OBJECTIVE

To test the hypothesis that the systematic use of a lung segment reference chart can improve the inter- and intra-observer agreement for the interpretation of ventilation-perfusion lung scans.

DESIGN

A randomized trial.

STUDY POPULATION

Ventilation-perfusion lung scans were obtained in a series of 220 consecutive patients with clinically suspected pulmonary embolism.

INTERVENTION

Ventilation-perfusion scans were randomly allocated to one of two series each consisting of 110 ventilation-perfusion lung scans. The first series of lung scans was interpreted according to the routine diagnostic approach, and the second series was interpreted with the mandatory use of a lung segment reference chart on which observed ventilation and perfusion defects were drawn. The two nuclear medicine physicians agreed a priori on the diagnostic criteria of the classification scheme.

MEASUREMENTS

Lung scans were classified as normal, non-high probability, or high probability for pulmonary embolism. The extent of disagreement between the nuclear medicine physicians (inter-observer disagreement) and the lack of internal consistency of each nuclear medicine physician (intra-observer disagreement) was assessed by the percentage disagreement and by kappa statistic.

RESULTS

Inter-observer disagreement which was 20% in the first series, decreased significantly in the second series to 7%; P = 0.003. Intra-observer disagreement for the first series was 10% and 22% for the nuclear medicine physicians, respectively. Intra-observer disagreement for the second series of lung scans decreased significantly for one nuclear medicine physician (intra-observer disagreement, 0%; P less than 0.01), whereas intra-observer disagreement was reduced to 10% for the other nuclear medicine physician (P = 0.09).

CONCLUSION

Inter- and intra-observer disagreement were significantly reduced when two nuclear medicine specialists interpreted ventilation-perfusion lung scans according to the routine diagnostic approach plus the use of a lung segment reference chart. The use of the lung segment reference chart for the interpretation of lung scans is likely to improve the management of patients with clinically suspected pulmonary embolism.

Physiological effects of tapering in highly trained athletes

This study examined some of the physiological and performance effects of three different tapers in highly trained athletes. After 8 wk of training, nine male middle-distance runners were randomly assigned to one of three different 7-day tapers: a high-intensity low-volume taper (HIT), a low-intensity moderate-volume taper (LIT), or a rest-only taper (ROT). After the first taper, subjects resumed training for 4 wk and performed a second taper and then resumed training for 4 wk and completed the remaining taper, so that each subject underwent all three tapers. Performance was measured before and after each taper by a treadmill run to fatigue at a velocity equivalent each subject's best 1,500-m time. Voluntary isometric strength and evoked contractile properties of the quadriceps were measured before and after each taper, as were muscle glycogen concentration and citrate synthase activity (from needle biopsies) and total blood and red cell volume by 125I and 51Cr tagging. Maximal O2 consumption was unaffected by all three tapers, but running time to fatigue increased significantly after HIT (+22%). It was unaffected by LIT (+6%) and ROT (-3%) procedure. Citrate synthase activity increased significantly with HIT and decreased significantly with ROT. Muscle glycogen concentration increased significantly after ROT and HIT, and strength increased after all three tapers. Total blood volume increased significantly after HIT and decreased after ROT.(ABSTRACT TRUNCATED AT 250 WORDS)

Operation Everest II: structural adaptations in skeletal muscle in response to extreme simulated altitude

Alterations in skeletal muscle structure were investigated in 6 male subjects who underwent 40 days of progressive decompression in a hypobaric chamber simulating an ascent to the summit of Mount Everest. Needle biopsies were obtained from vastus lateralis of 5 subjects before and immediately after confinement in the chamber, and were examined for various structural and ultrastructural parameters. In addition, total muscle area was calculated in 6 subjects from CT scans of the thighs and upper arms. Muscle area at these sites was found to decrease significantly (by 13 and 15%) as a result of the hypobaric confinement. This was substantiated by significant (25%) decreases in cross sectional fibre areas of the Type I fibres and 26% decreases (non significant) in Type II fibre area. Capillary to fibre ratios remained unchanged following hypoxia as did capillary density although there was a trend (non significant) towards an increase in capillary density. There were no significant increases in mitochondrial volume density or other morphometric parameters. These data indicate that chronic, severe hypoxia on its own does not result in an increase in absolute muscle capillary number or a de novo synthesis of mitochondria. The trends toward an increase in capillary density and mitochondrial volume density were interpreted as being secondary occurrences in response to the pronounced muscle atrophy which occurred.

Recurrent nerve palsy due to parathyroid cyst

Cysts of the parathyroid gland are uncommon neck masses and difficult to diagnose. They can cause symptoms by endocrinological function or by pressure on surrounding structures. A case of recurrent nerve palsy due to a parathyroid cyst is presented. Aspiration of parathyroid cysts can be diagnostic and therapeutic in some cases.

Response of red cell and plasma volume to prolonged training in humans

To clarify the role of progressive heavy training on vascular volumes and hematologic status, seven untrained males [maximal O2 uptake (VO2max) = 45.1 +/- 1.1 (SE) ml.kg-1.min-1] cycled 2 h/day at an estimated 62% of VO2max. Training was conducted five to six times per week for approximately 8 wk. During this time, VO2max increased (P less than 0.05) by 17.2%. Plasma volume (PV) measured by 125I increased (P less than 0.05) from 3,068 +/- 104 ml at 0 wk to 3,490 +/- 126 ml at 4 wk and then plateaued during the remaining four wk (3,362 +/- 113 ml). Red cell (RBC) mass (RCM) measured by 51Cr-labeled RBC did not change during the initial 4 wk of training (2,247 +/- 66 vs. 2,309 +/- 128 ml). As well, no apparent change occurred in RCM during the final 4 wk of training when RCM was estimated using PV and hematocrit (Hct). Collectively, PV plus RCM, expressed as total blood volume (TBV), increased (P less than 0.05) by 10% at 4 wk and then stabilized for the final 4 wk. During the initial phase of training, reductions (P less than 0.05) were also noted in Hct (4.6%), hemoglobin (Hb, 4.0%), and RBC count (6.3%). In contrast, an increase in mean cell volume (MCV, 1.7%) and mean cell Hb (2.3%) was observed (P less than 0.05). From 4 to 8 wk, no further changes (P greater than 0.05) in Hb, RBC, and MCV were found, whereas both mean cell Hb and Hct returned to pretraining levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Noninvasive measurement of lung carbon-11-serotonin extraction in man

The fraction of serotonin extracted on a single passage through the lungs is being used as an early indicator of lung endothelial damage but the existing techniques require multiple arterial blood samples. We have developed a noninvasive technique to measure lung serotonin uptake in man. We utilized the double indicator diffusion principle, a positron camera, 11C-serotonin as the substrate, and 11CO-erythrocytes as the vascular marker. From regions of interest around each lung, we recorded time-activity curves in 0.5-sec frames for 30 sec after a bolus injection of first the vascular marker 11CO-erythrocytes and 10 min later 11C-serotonin. A second uptake measurement was made after imipramine 25-35 mg was infused intravenously. In three normal volunteers, the single-pass uptake of 11C-serotonin was 63.9% +/- 3.6%. This decreased in all subjects to a mean of 53.6% +/- 1.4% after imipramine. The rate of lung washout of 11C was also significantly prolonged after imipramine. This noninvasive technique can be used to measure lung serotonin uptake to detect early changes in a variety of conditions that alter the integrity of the pulmonary endothelium.

Cardiopulmonary function during long-term central venous catheterization

A prospective study was performed in an ambulatory group of infants, children, and young adults with neoplastic disorders to determine the prevalence of significant cardiopulmonary complications during long-term central venous catheterization. A cohort of 20 consecutive patients who had central venous catheters in situ for a mean of 13.5 months underwent pulmonary function testing, chest radiography, ventilation perfusion lung scintigraphy, electrocardiography, and echocardiography. No significant complications were seen. Specifically, there was no evidence of localized thrombus formation or pulmonary emboli, and no indirect evidence of pulmonary hypertension. In addition, we reviewed retrospectively the autopsy reports of 15 patients who died with central venous catheters in place. Three of these patients had superficial endocardial reactions. One patient had a right atrial mural thrombus related to the catheter, but two other patients were noted to have left atrial mural thrombi. This study demonstrates that central venous catheters can be used safely on a long-term basis in ambulatory patients requiring frequent venous access for treatment of their neoplastic disorders.

Early adaptations in gas exchange, cardiac function and haematology to prolonged exercise training in man

In order to determine the effect of short-term training on central adaptations, gas exchange and cardiac function were measured during a prolonged submaximal exercise challenge prior to and following 10-12 consecutive days of exercise. In addition, vascular volumes and selected haematological properties were also examined. The subjects, healthy males between the ages of 19 and 30 years of age, cycled for 2 h per day at approximately 59% of pre-training peak oxygen consumption (VO2) i.e., maximal oxygen consumption (VO2max). Following the training, VO2max (l.min-1) increased (P less than 0.05) by 4.3% (3.94, 0.11 vs 4.11, 0.11; mean, SE) whereas maximal exercise ventilation (VE,max) and maximal heart rate (fc,max) were unchanged. During submaximal exercise, VO2 was unaltered by the training whereas carbon dioxide production (VE) and respiratory exchange ratio were all reduced (P less than 0.05). The altered activity pattern failed to elicit adaptations in either submaximal exercise cardiac output or arteriovenous O2 difference. fc was reduced (P less than 0.05). Plasma volume (PV) as measured by 125I human serum albumin increased by 365 ml or 11.8%, while red cell volume (RCV) as measured by 51chromium-labelled red blood cells (RBC) was unaltered. The increase in PV was accompanied by reductions (P less than 0.05) in haematocrit, haemoglobin concentration (g.100 ml-1), and RBCs (10(6) mm-3). Collectively these changes suggest only minimal adaptations in maximal oxygen transport during the early period of prolonged exercise training. However, as evidenced by the changes during submaximal exercise, both the ventilatory and the cardiodynamic response were altered.(ABSTRACT TRUNCATED AT 250 WORDS)

Heparin effect on bone density

In order to provide estimates of the risks of symptomatic osteoporosis and reduced bone density in premenopausal women treated with long-term (greater than 1 month) heparin therapy, we evaluated a cohort of 61 consecutive premenopausal women previously treated with long-term heparin (cases) and a group of controls matched for age, parity and duration between the last pregnancy and evaluation. All patients underwent dual photon absorptiometry of the lumbar spine and single photon absorptiometry of the wrist and most cases underwent plain lateral radiography of the thoracolumbar spine in order to exclude silent fractures. Although none of the cases suffered symptomatic fractures (0 of 61, 95% confidence intervals 0.0 to 5.9%), there was a significantly greater proportion of cases than controls with bone density below our pre-defined levels. The long-term implications of our findings are uncertain but because it is possible that the reduction in bone density predisposes women to fractures, this potential risk should be considered when treating women with long-term heparin.

Clinical validity of a normal perfusion lung scan in patients with suspected pulmonary embolism

The objective of this study was to test the safety of withholding anticoagulant therapy in patients with clinically suspected pulmonary embolism who have normal perfusion lung scans, regardless of the clinical manifestations. Anticoagulant therapy was withheld or withdrawn in 515 consecutive patients except in patients in whom deep-vein thrombosis was detected. Only three of the 515 patients had symptomatic venous thromboembolism on follow-up. The frequency of symptomatic pulmonary embolism on follow-up was one of 515 patients. With knowledge of the normal findings by perfusion scanning, an alternative diagnosis was established in 367 of the 515 patients. Cause of symptoms remained uncertain in 148 patients. It is safe to withhold anticoagulant therapy in patients with suspected pulmonary embolism and normal perfusion scans, regardless of the clinical manifestations. The finding of a normal perfusion scan excludes the presence of clinically important pulmonary embolism and makes pulmonary angiography unnecessary.

A new noninvasive management strategy for patients with suspected pulmonary embolism

Pulmonary embolism is associated strongly with proximal-vein thrombosis. We tested the hypothesis that recurrent venous thromboembolism is unlikely in the absence of proximal-vein thrombosis. We performed a prospective cohort study in 874 patients with suspected pulmonary embolism. On long-term follow-up of 371 patients with the following characteristics: (1) abnormal, non-high-probability lung scans, (2) off anticoagulant therapy, and (3) serial noninvasive test results negative for proximal-vein thrombosis, only 10 (2.7%; 95% confidence limits, 1.3% to 4.9%) had venous thromboembolism. By comparison, venous thromboembolism on follow-up occurred in 3 (1%) of 315 patients (95% confidence limits, 0.2% to 2.8%) with normal lung scans, and in 5 (7%) of 66 patients (95% confidence limits, 2.5% to 16.8%) with high-probability lung scans. Patients whose serial noninvasive test results were negative for proximal-vein thrombosis have a good prognosis without anticoagulant therapy.

The use of indium-111 oxine platelet scintigraphy and survival studies in pediatric patients with thrombocytopenia

We have utilized 111In-labeled heterologous platelets to investigate the mechanism of thrombocytopenia in ten children. From the scintigraphic findings, platelet survival times, and clinical information, thrombocytopenia was ascribed to decreased production or to increased destruction. Two patients were found to have bone marrow production defects. Two patients with hemangiomas were studied. In one, the hemangioma was shown not to be the cause of thrombocytopenia. In the second, the hemangioma was proven the source of platelet destruction, but was much more extensive than clinically evident. In both, surgical manipulation of the hemangioma was avoided. Six additional patients had thrombocytopenia due to accelerated destruction. In four, the spleen was shown responsible. In two, however, the spleen was shown not to be responsible for the low platelet counts, and splenectomy was avoided. Thus, 111In-platelet scintigraphy and survival studies are valuable in the classification and management of childhood thrombocytopenia. We believe that this study should be performed, when possible, in any child with thrombocytopenia where the mechanism is unclear or the therapeutic intervention involves splenectomy or resection of a hemangioma.

Simultaneous measurement of lung clearance rates for Tc- and In-DTPA in normal and damaged lungs

We investigated the relative clearance rates for 99mTc-labeled diethylenetriamine-pentaacetate (Tc-DTPA) and 113mIn-labeled DTPA (In-DTPA) when they were inhaled and deposited together within the lungs of same animal. Submicronic aerosols containing Tc-DTPA and In-DTPA were simultaneously generated by different nebulizers and collected within the same anesthetic bag. The combined aerosols were insufflated into piglets. Clearances for both compounds were measured simultaneously in normal lungs and when the lungs were damaged by intravenous oleic acid or by a presumed oxidant agent, intravenous or intratracheal phorbol myristate acetate (PMA). A medium-energy collimator and a computer-assisted gamma camera were used to calculate clearances. Correction was made for downscatter from the In photopeak into the Tc window. Marked lung injury occurred as evidenced by increases in lung water content and decreases in arterial PO2. The clearance of In-DTPA was slightly but significantly slower than for Tc-DTPA in each group of animals. The correlation (r = 0.93) between clearances for Tc-DTPA and In-DTPA was good, even though in vitro studies demonstrated that Tc-DTPA, but not In-DTPA, slowly dissociated at room and body temperatures. Oleic acid increased, but surprisingly, PMA had no effect on clearance rates for both In-DTPA and Tc-DTPA. We recommend continued use of Tc-DTPA for these measurements in view of its lower cost, requirement for only low-energy collimation, better imaging characteristics, and widespread availability. The overlap between control and injured lungs and the lack of increased clearance rates after PMA suggest this technique does not always detect acute lung injury.

Risks to the fetus of radiologic procedures used in the diagnosis of maternal venous thromboembolic disease

The diagnosis of suspected venous thromboembolic disease during pregnancy is problematic because of the fear of fetal irradiation with routine diagnostic procedures. In order to develop rational guidelines, we have calculated levels of radiation exposure to the fetus for the common diagnostic procedures and conducted a literature review to examine the fetal risks associated with these levels of radiation. A small increase in the relative risk of childhood cancer is suggested by a literature review of outcomes following low dose (less than 5 rads), in utero radiation exposure. With careful use of the available procedures, a diagnosis of venous thrombosis is possible with fetal radiation exposure of less than 0.50 rads and a diagnosis of pulmonary embolism is possible with fetal radiation exposure of less than 0.05 rads. The risk of such exposure is small, both in relative and absolute terms.

The response of the pulmonary circulation to exercise during normoxia and hypoxia following pneumonectomy in the adult sheep

Pneumonectomy approximately halves the available pulmonary vascular bed. It is unknown whether the remaining lung has sufficient vascular reserve to cope with increased blood flow under stressful conditions without demonstrating abnormal pulmonary hemodynamics. To investigate this question, unanesthetized ewes with vascular catheters had hemodynamics assessed before and after a left pneumonectomy. Subsequently, on different days, the sheep were exercised on a treadmill under normoxic and hypobaric hypoxic (430 mmHg) (1 mmHg = 133.3 Pa) conditions. Pneumonectomy itself increased mean pulmonary arterial pressure by 4 mmHg. During normoxic or hypoxic exercise, the pneumonectomized sheep demonstrated a pulmonary hemodynamic response similar to normal sheep with two lungs. The pressure-flow relation for the right lung suggested the vascular reserve of the lung was not exceeded during exercise in the pneumonectomized sheep. Eighteen to 70 days after pneumonectomy there was no evidence of right ventricular hypertrophy, but there were small increases in the number of muscularized vessels less than 50 microns diameter and in the amount of muscle in normally muscularized pulmonary arteries. This study demonstrates that pneumonectomy slightly increases mean pulmonary arterial pressure. However, there is sufficient vascular reserve in the remaining lung to permit a normal hemodynamic response to exercise-induced increased blood flow even under hypoxic conditions.

Operation Everest. II: Nutrition and body composition

Progressive body weight loss occurs during high mountain expeditions, but whether it is due to hypoxia, inadequate diet, malabsorption, or the multiple stresses of the harsh environment is unknown. To determine whether hypoxia due to decompression causes weight loss, six men, provided with a palatable ad libitum diet, were studied during progressive decompression to 240 Torr over 40 days in a hypobaric chamber where hypoxia was the major environmental variable. Caloric intake decreased 43.0% from 3,136 to 1,789 kcal/day (P less than 0.001). The percent carbohydrate in the diet decreased from 62.1 to 53.2% (P less than 0.001). Over the 40 days of the study the subjects lost 7.4 +/- 2.2 (SD) kg and 1.6% (2.5 kg) of the total body weight as fat. Computerized tomographic scans indicated that most of the weight loss was derived from fat-free weight. The data indicated that prolonged exposure to the increasing hypoxia was associated with a reduction in carbohydrate preference and body weight despite access to ample varieties and quantities of food. This study suggested that hypoxia can be sufficient cause for the weight loss and decreased food consumption reported by mountain expeditions at high altitude.

Lung clearance of 99mTc-DTPA in patients with acute lung injury and pulmonary edema

Several acute and chronic conditions that alter the integrity of the pulmonary epithelium increased the rate of absorption or clearance into the circulation of small solutes deposited in the alveoli. Technetium 99m diethylenetriamine pentaacetic acid can be deposited in the lungs as a submicronic aerosol and its rate of clearance measured with a gamma camera or simple probe. This clearance technique is currently being used to evaluate patients who have developed pulmonary edema and also to detect those patients from a high risk group who are likely to develop adult respiratory distress syndrome (ARDS). Its role in the evaluation of patients with pulmonary edema is still under active investigation. It is clear that a single measurement in patients who smoke is not useful, but repeated measurements may provide important information. The lung clearance measurement is very sensitive to changes in epithelial integrity but is not specific for ARDS. It may be most useful in combination with other predictive tests or when the clearance rate is normal.

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.

The effect of hypoxia on platelet survival and site of sequestration in the newborn rabbit

Thrombocytopenia occurs frequently in sick neonates that have experienced perinatal asphyxia. This study investigated the effect of one component of asphyxia, hypoxia, on platelet lifespan and site of sequestration. 111Indium oxine platelet survivals with scintigraphic imaging were performed in newborn and adult rabbits exposed to room air (normoxia) or following exposure to a 15 minute, severe hypoxic insult (FIO2 = 0.05). Platelet survivals in normoxic adults (n = 27) and newborn rabbits (n = 11) were similar (60 +/- 3.9 hr vs 64 +/- 8.0 hr, m +/- SEM). Inhalation of 5% oxygen for 15 minutes was not associated with an acidemia and did not produce thrombocytopenia but significantly shortened the platelet survival to 34 +/- 3 hr in the adult (n = 18) and 38 +/- 3 hr in the newborn rabbit (n = 7). Postmortem measurement of the sites of 111In-platelet accumulation showed that under normoxic conditions the platelets accumulated in the liver and spleen (23 +/- 4.3% and 8 +/- 1.0% of the total body counts) in the adult with even greater accumulation in the liver (58 +/- 6.8%) and spleen (19 +/- 4.9%) of the newborn (p less than 0.001). The latter observation was likely due to the relatively increased size of the liver and spleen in the newborn compared to the adult. Hypoxia did not alter the site of platelet sequestration in adults or newborns. Our results suggest that the newborn has the same platelet survival as the adult and that acute, severe hypoxia significantly shortens the survival of platelets in both groups. Although the sites of sequestration are qualitatively the same in the newborn, there is greater sequestration in the liver and spleen when compared to the adult.

Nigrostriatal dopaminergic activity is increased during exhaustive exercise stress in rats

Exercise capacity is influenced by both increases and decreases in central dopaminergic activity. To investigate the effects of exercise stress on intracerebral dopamine metabolism, rats were run on a motor driven treadmill at 37 m/min for varying times up to exhaustion at 19.6 +/- 0.6 min. Dopamine, DOPAC, and HVA concentrations in striatum, brain stem, and hypothalamus increased towards exhaustion. 5-HIAA concentrations increased in striatum whereas norepinephrine concentrations decreased in hypothalamus. The results indicate that delayed increases in dopaminergic activity occurs during exercise. These, and other observations indicate that central dopaminergic activity modulates exercise performance.

Pulmonary clearance of 99mTc-DTPA in infants who subsequently develop bronchopulmonary dysplasia

The lung clearance of inhaled and deposited 99mTc-DTPA is biphasic, with a very rapid initial clearance in premature infants with acute hyaline membrane disease (HMD). Infants who rapidly recover from HMD revert to a monophasic slower clearance rate prior to successful extubation. This raises the possibility that a persistently fast clearance might identify infants who will not recover and in whom bronchopulmonary dysplasia (BPD) will subsequently be diagnosed. To examine this possibility, we reviewed our experience using this technique and identified infants who had subsequently developed BPD. These 8 intubated, ventilator-dependent, premature infants inhaled a submicronic aerosol containing 99mTc-DTPA on 14 occasions during the second, third, and fourth weeks of life. Clearance was biphasic, with very rapid initial lung clearance (T1/2 less than 2 min) on 5 occasions in 4 infants during their second or third week of life. The other infants had monophasic clearances that were much slower (T1/2 = 52 +/- 26 SD min). At Day 28 of life, all infants with BPD were ventilator-and/or oxygen-dependent. We conclude that lung clearance of 99Tc-DTPA is very rapid during acute HMD, but that it can normalize before 28 days of life in infants in whom BPD is subsequently diagnosed.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Aerosol delivery to the rabbit lung with an infant ventilator

Little is known about delivery of aerosolized medications to infants undergoing assisted positive pressure ventilation. To assess delivery of medications to the lung with an infant ventilator (Bournes LS104), 27 experiments were performed on anesthetized adult rabbits. Lung deposition was determined by using aerosol radiolabeled with 99m technetium sulfur colloid. Initially a traditional nebulizer was studied and very inefficient delivery to the lung was observed (0.19 +/- 0.10 SD% of the initial nebulizer dose). Subsequent experiments using a nebulizer that generates submicronic aerosol particles, at equivalent aerosol output, achieved a highly significant increase in delivery (1.96 +/- 1.19 SD%, P less than 0.001). Our experiments demonstrated that modifications to to traditional nebulizer systems can enhance delivery of aerosolized medication to the lungs of rabbits.

Ventilation scanning with technetium labeled aerosols. DTPA or sulfur colloid?

We have compared the distribution in the lungs of submicronic aerosols of either Tc-99m sulfur colloid or Tc-99m DTPA immediately after inhalation with the distribution 20 minutes later in 83 patients. Thirty-two of the 83 patients were active smokers. Of the 28 smokers who received Tc-99m DTPA aerosol, the total lung count fell by a mean of 27 +/- 14% between the 0 and 20 minute image. Eleven of these patients also had a major change in distribution of isotope during this time. In the nonsmoking patients total lung counts from Tc-99m DTPA fell by only 16 +/- 8% and none had a major change in distribution pattern. None of the smoking or non-smoking patients who received Tc-99m sulfur colloid had a significant change in count rate or distribution pattern over 20 minutes. The effects on the ventilation images of these rapid changes in count rate and distribution pattern after Tc-99m DTPA aerosol can be minimized by completing the ventilation study as quickly as possible after inhaling Tc-99m DTPA or by using a nondiffusible agent such as Tc-99m sulfur colloid.

Hypoxia-induced vasopressin release and coagulopathy in a normal subject

Humans exposed to hypoxia usually increase their plasma procoagulant VIII activity (VIII:C) with no change in the concentration of VIII related antigen (VIIIR:Ag). This case report describes an apparently normal subject who developed marked qualitative and quantitative changes in all components of the factor VIII complex while inhaling an 11% oxygen/balance nitrogen gas mixture for 2 h. Blood from fresh venepunctures was drawn at baseline, during and after exposure to hypoxia for the following: a partial thromboplastin time, a prothrombin time, fibrin monomer, factor VIII:C, VIII procoagulant antigen (VIII:CAg); ristocetin cofactor activity (VIIIR:Co); VIII von Willebrand factor (VIII:vWF) multimer pattern; and arginine vasopressin. During hypoxia VIII:C, VIII:CAg, VIIIR:Ag and VIIIR:Co increased 4 to 5 fold; the VIII:vWF multimer pattern showed increasing low molecular weight complexes, fibrin monomer appeared and arginine vasopressin (AVP) levels increased from 5.5 pg . ml-1 to 73.8 pg . ml-1. These changes are compatible with both the release of the VIIIR:Ag by AVP and protease induced fragmentation of the VIII complex.

Diagnostic value of ventilation-perfusion lung scanning in patients with suspected pulmonary embolism

Differing opinions about the value of ventilation-perfusion lung scanning have created controversy concerning the correct approach to the diagnosis of pulmonary embolism. In a prospective study of 305 consecutive patients with clinically suspected pulmonary embolism and abnormal perfusion lung scans, we evaluated the role of ventilation-perfusion lung scanning, pulmonary angiography, and objective testing for venous thrombosis in the diagnostic process. Segmental or greater perfusion defects with ventilation mismatch have a high probability (86 percent) of pulmonary embolism. Contrary to current clinical practice, however, the approach of ruling against pulmonary embolism by a "low probability" scan pattern is incorrect, even with an improved technique for ventilation imaging; the frequency of pulmonary embolism in these patients ranged from 25 to 40 percent. Objective testing for venous thrombosis provides a practical alternative to performing pulmonary angiography in the diagnostic work-up; by providing an endpoint for commencing anticoagulant therapy, a positive result obviates the need for further testing in 20 to 30 percent of patients.

Bradykinin is degraded in hypoxic lungs and does not affect epithelial permeability

To investigate the effect of intravenous infusions of bradykinin (BK) on the permeability of the hypoxic pulmonary epithelium to small solutes, experiments (n = 7) were performed in yearling sheep with chronic vascular catheters. Sheep were anesthetized, intubated, paralyzed, and ventilated. After establishing stable and normal base-line pulmonary hemodynamics and blood gas tensions, the lungs were insufflated with a submicronic aerosol of technetium-99m-labeled diethylenetriaminepentaacetate (99mTc-DTPA, mol wt = 492). Radioactivity arising from the right hemithorax was measured by an NaI probe with a parallel-holed collimator. The base-line pulmonary clearance rate (k) for 99mTc-DTPA was 0.51 +/- 0.09% (SE)/min, while the sheep were ventilated with a fractional concentration of inspired O2 (FIO2) of 0.5 [arterial partial pressure of O2 (PaO2) = 196 +/- 11.4 (SE) Torr]. Clearance of 99mTc-DTPA was unaffected by hypoxia alone or BK infusions in nonhypoxic lungs. The combination of an intravenous infusion of BK at either 1.2 (n = 3) or 2.4 micrograms . kg-1 . min-1 (n = 4) and alveolar hypoxia [FIO2 = 0.11, PaO2 = 28 +/- 1.6 (SE) Torr] did not affect pulmonary clearance of 99mTc-DTPA [k = 0.43 +/- 0.08% (SE)/min]. In contrast, a 0.05-ml/kg intravenous infusion of oleic acid increased clearance 10-fold in one sheep. During combined hypoxia and BK infusion the pulmonary arterial BK concentration (radioimmunoassay) increased from 0.82 +/- 0.16 (SE) to 7.05 +/- 1.86 ng/ml (P less than 0.001), but the systemic arterial concentrations were unchanged [0.67 +/- 0.19 (SE) to 0.66 +/- 0.09 ng/ml].(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary thromboemboli after neonatal asphyxia

Two surviving neonates with pulmonary thromboembolism, diagnosed by ventilation-perfusion lung scan, are described. Both infants had respiratory distress, and one had features consistent with persistent pulmonary hypertension of the neonate. These reports demonstrate that substantive pulmonary emboli can occur in neonates and may not be recognized without an appropriate level of clinical suspicion.

Central dopaminergic activity influences rats ability to exercise

Rats were run to exhaustion on a motor driven treadmill. Apomorphine given to intact rats prolonged the time to exhaustion. Apomorphine given to 6-hydroxydopamine lesioned rats also prolonged the time to exhaustion. Intracerebroventricular 6-hydroxydopamine alone reduced the time to exhaustion. Clonidine given to these animals had no effect. We suggest that central dopaminergic activity influences rats ability to exercise.

Management of cancer pain. A practical approach

One in five deaths in Australia is due to cancer. Pain is an important symptom in many of these patients, but it is often either unrelieved or poorly controlled. Misconceptions about the nature of cancer pain and its control are detailed, and the practical management of these patients is discussed in the light of personal experience. Proper use of older therapeutic methods is still important, as recent advances allow better results only in a minority of cases. Special attention is given to the use of regular oral doses of morphine. Many of the interacting factors affecting pain perception are considered, so that the sense of impotence in those faced with the management of a progressive incurable disease may be reduced through an understanding of the causes of pain and its correct management.

Measurement of pulmonary clearance of radioaerosol using a portable sodium iodide probe

To determine whether a portable sodium iodide (NaI) probe could provide a valid measure of the pulmonary half-life (T1/2) of aerosolized technetium-99m-diethylenetriaminepentaacetate (99mTc-DTPA, mol wt = 492) in small chests, we measured pulmonary clearance in rabbits using a gamma-scintillation camera and the portable probe. In 10 experiments the lungs of New Zealand White rabbits were insufflated with aerosolized 99mTc-DTPA (0.6 mum aerodynamic mass median diameter) and then simultaneously imaged with the gamma-camera and the probe positioned over the upper right lung. In an additional 12 experiments, alveolar-capillary membrane permeability was increased by either intratracheal instillation of 0.1 N hydrochloric acid (HCl) or intravenous injection of 100 mg/kg of oleic acid. All animals tolerated the procedure. There was a significant decrease in pulmonary T1/2 in both the HCl group (53.4 +/- 10.4 min, mean +/- SE) and the oleic acid group (14.7 +/- 2.3 min) when compared with control (127.5 +/- 18.1 min). When we compared the T 1/2 of the right lung determined by the gamma-camera with that measured by the probe, the correlation coefficient was 0.95. Potential nonpulmonary contributions to thoracic radioactivity were not significant. We conclude that a portable NaI probe is a valid means of determining T 1/2 of 99mTc-DTPA in small chests when compared with a gamma-camera and can detect increases in the permeability of the alveolar-capillary membrane to small solutes.