Microvascular permeability of the non-heart-beating rabbit lung after warm ischemia and reperfusion: role of neutrophil elastase

STUDY OBJECTIVES: Criteria used to define the respective roles of pulmonary mechanics and cardiovascular disease in limiting exercise performance are usually obtained at peak exercise, but are dependent on maximal patient effort. To differentiate heart from lung disease during a less effort-dependent domain of exercise, the predictive value of the breathing reserve index (BRI=minute ventilation [VE]/maximal voluntary ventilation [MVV]) at the lactate threshold (LT) was evaluated. DESIGN: Thirty-two patients with COPD and a pulmonary mechanical limit (PML) to exercise defined by classic criteria at maximum oxygen uptake (VO2max) were compared with 29 patients with a cardiovascular limit (CVL) and 12 normal control subjects. Expired gases and VE were measured breath by breath using a commercially available metabolic cart (Model 2001; MedGraphics Corp; St. Paul, Minn). Arterial blood gases, pH, and lactate were sampled each minute during exercise, and cardiac output (Q) was measured by first-pass radionuclide ventriculography (System 77; Baird Corp; Bedford, Mass) at rest and peak exercise. RESULTS: For all patients, the BRI at lactate threshold (BRILT) correlated with the BRI at VO2max (BRIMAX) (r=0.85, p<0.0001). The BRILT was higher for PML (0.73+/-0.03, mean+/-SEM) vs CVL (0.27+/-0.02, p<0.0001), and vs control subjects (0.24+/-0.03, p<0.0001). A BRILT > or = 0.42 predicted a PML at maximum exercise, with a sensitivity of 96.9%, a specificity of 95.1%, a positive predictive value of 93.9%, and a negative predictive value of 97.5%. CONCLUSIONS: The BRILT, a variable measured during the submaximal realm of exercise, can distinguish a PML from CVL.     

Invasive exercise testing in the evaluation of patients at high-risk for lung resection

The aim of this study was to investigate whether invasive exercise testing with gas exchange and pulmonary haemodynamic measurements could contribute to the preoperative assessment of patients with lung cancer at a high-risk for lung resection. Sixty-five patients scheduled for thoracotomy (aged 66+/-8 yrs (mean+/-SD), 64 males, forced expiratory volume in one second (FEV1) 54+/-13% predicted) were studied prospectively. High risk was defined on the basis of predicted postpneumonectomy (PPN) FEV1 and/or carbon monoxide diffusing capacity of the lung (DL,CO) <40% pred. Arterial blood gas measurements were performed in all patients at rest and during exercise. In 46 patients, pulmonary haemodynamic measurements were also performed at rest and during exercise. Predicted postoperative (PPO) values for FEV1 and DL,CO were calculated according to quantitative lung scanning and the amount of resected parenchyma. There were four postoperative deaths (6.2% mortality rate) and postoperative cardiorespiratory complications developed in 31 (47.7%) patients. Patients with respiratory complications only differed from patients without or with minimal (arrhythmia) complications in FEV1,PPO. Peak O2 uptake and haemodynamic variables were similar in both groups. The four patients who died had a lower FEV1,PPO, a lower DL,CO,PPO and a greater decrease in arterial oxygen tension during exercise, compared with the remaining patients. In conclusion, the forced expiratory volume in one second, together with the extent of parenchymal resection and perfusion of the affected lung, are useful parameters to identify patients at greatest risk of postoperative complications among those at a high-risk for lung resection. In these patients, pulmonary haemodynamic measurements appear to have no discriminatory value, whereas gas exchange measurements during exercise may help to identify patients with higher mortality risk.     

Effect of acute bicarbonate administration on exercise responses of COPD patients

Patients with severe chronic obstructive pulmonary disease (COPD) are limited in their exercise tolerance by the level of ventilation (VE) they can sustain. We determined whether acutely increasing blood bicarbonate levels decreased acid stimulation to the respiratory chemoreceptors during exercise, thereby improving exercise tolerance. Responses were compared with those obtained during 100% O2 breathing (known to reduce VE in these patients) and to the responses of healthy young subjects. Participants were six patients with severe COPD (forced expired volume in 1 s = 31 +/- 11% predicted) but without chronic CO2 retention and 5 healthy young subjects. Each subject performed three incremental cycle ergometer exercise tests: 1) control, 2) after ingestion of 0.3 g.kg-1 of sodium bicarbonate and 3) while breathing 100% O2. During these tests VE was measured continuously and arterialized venous blood (patients) or arterial blood (healthy subjects) was sampled serially to assess acid base variables. Bicarbonate loading increased standard bicarbonate by 4-6 mmol.L-1 and this elevation persisted during exercise. In both groups, bicarbonate loading resulted in a substantially higher arterial pH; arterial PCO2 was either unchanged (healthy subjects) or mildly (averaging 5 torr) higher (COPD patients). However, in neither group did bicarbonate loading result in an altered VE response to exercise or an increase in exercise tolerance. In contrast, superimposing hyperoxia on bicarbonate ingestion yielded, on average, 24% reduction in VE and 50% increase in peak work rate in the patients (but not in the healthy young subjects). We conclude that acute bicarbonate loading is not an ergogenic aid in patients with severe COPD.     

Ventilation and respiratory mechanics during exercise in younger subjects breathing CO2 or HeO2

To determine if ventilation (VE) during maximal exercise would be increased as much by 3% CO2 loading as by resistive unloading of the airways, we studied seven subjects (39 +/- 5 years; mean +/- S.D.) during graded-cycle ergometry to exhaustion while breathing: (1) room air (RA); (2) 3% CO2, 21% O2, and 76% N2; or (3) 79% He and 21% O2). VE and respiratory mechanics were measured during each 1-min increment (20 or 30 W) in work rate. VE during maximal exercise was increased 21 +/- 17% when breathing 3% CO2 and 23 +/- 16% when breathing HeO2 (P < 0.01). Further, the ventilatory response to exercise above ventilatory threshold (VTh) was increased (P < 0.05) when breathing HeO2 (0.89 +/- 0.26 L/min/W) as compared with breathing RA (0.65 +/- 0.12). When breathing HeO2, end-expiratory lung volume (% total lung capacity, TLC) was lower during maximal exercise (46 +/- 7) when compared with RA (53 +/- 6, P < 0.01). In conclusion, VE during maximal exercise can be augmented equally by 3% CO2 loading as by resistive unloading of the airways in younger subjects. This suggests that in younger subjects with normal lung function there are minimal mechanical ventilatory constraints on VE during maximal exercise.     

A case of meningioma appearing as a cyst with solid parietal nodule. Evaluation using computerized tomography and magnetic resonance

Bilateral sequential lung transplantation was complicated by pulmonary artery anastomotic stenosis and bilateral pulmonary thromboemboli. Pulmonary artery thrombus was eliminated by intrathrombotic but not by systemic administration of urokinase. The pulmonary emboli resulted in localized pulmonary infarctions, supporting the need for thrombolytic intervention to restore pulmonary perfusion in the absence of collateral bronchial blood flow after lung transplantation. Pulmonary artery stenosis was relieved by endovascular stenting, avoiding an early reoperative procedure. This case suggests that direct administration of thrombolytic agent may be superior to intravenous administration in the treatment of pulmonary thromboemboli. Pulmonary arterial anastomotic stenoses after lung transplantation can be relieved by endovascular procedures.     

Evaluation of pulmonary vascular anatomy and blood flow by magnetic resonance

Rapidly evolving magnetic resonance (MR) imaging techniques provide noninvasive approaches to evaluating morphology and quantitative physiologic information about blood flow in the pulmonary circulation. Important clinical applications currently include the preoperative and postoperative evaluation of congenital abnormalities, assessment of vascular involvement by extrinsic and intrinsic tumors, identification of central thromboemboli, and diagnosis of vascular lung lesions. Ongoing refinements in pulmonary MR angiography may make it possible to use the technique for the noninvasive detection of acute pulmonary emboli in the near future. Quantitative measurements based upon MR flow-encoding sequences are promising for the evaluation of patients with abnormal degrees or distributions of pulmonary blood flow, for example, those with unilateral lung transplants or pulmonary arterial stenoses. MR contrast agents currently under development also show promise for quantitative measurements of regional pulmonary ventilation and perfusion. The coupling of high-resolution anatomic and functional images renders MR a uniquely attractive and powerful method for evaluating the pulmonary vasculature.     

Relevance of width measurements of the right pulmonary artery descending branch for detection of pulmonary hypertension in chronic obstructive lung diseases (author's transl)

363 patients with chronic obstructive lung diseases were examined regarding the relation between pulmonary hypertension and width of the right descending branch of the pulmonary artery (RDB). There was found a high significant correlation between mean pulmonary artery pressure at rest and diameter of the RDB. The width of RDB was not so close correlated with pulmonary artery pressure during exercise. If the diameter of the RDB was 19 mm and more, a manifest pulmonary hypertension was stated nearly always. Missing this radiological sign doesn't exclude pulmonary hypertension. The method will be useful for screening a risk group "pulmonary hypertension". All cases selected by this method aught to be examined by means of right heart catheterization with the floating technic.     

Involvement of spinal NMDA receptors in capsaicin-induced nociception

On poststress images with 99mTc-sestamibi (MIBI), increased lung uptake of the radiotracer may reflect severe or multivessel coronary artery disease. METHODS: We measured pulmonary/myocardial ratios of MIBI at standardized times on immediate poststress acquisitions and on delayed tomographic acquisitions. In 1500 sequential patients referred for rest and stress myocardial tomography, ancillary planar images were obtained 4 min postinjection at peak stress with exercise, either alone (exercise, n = 674), or after intravenous dipyridamole (dipyridamole, n = 826). RESULTS: Based on 95% confidence limits in the angiographic normals, high values for immediate acquisitions were found in 17% of dipyridamole studies and 15% of exercise studies. High values for delayed acquisitions were found in 10% of dipyridamole studies and 9% of exercise studies. For both stress modes, increased values were related (p < 0.001) to ischemic perfusion defects for immediate images, to fixed defects for delayed images, and to ventricular dilation in both cases. By logistic regression analysis, body weight and history of infarction were also minor independent determinants (p < 0.01) of delayed acquisitions. In a subset of 250 cases with angiographic correlation (163 with dipyridamole; 87 with exercise), immediate lung uptake was highly correlated with ventricular dysfunction and with coronary stenoses (p < 0.0001). Relationships were similar to those in a historic control series imaged with 201TI. Values for delayed poststress images, and for corresponding rest images, showed strong relationships to ventricular dysfunction but not to stenosis severity. CONCLUSION: The relationships of immediate lung uptake to scintigraphic and angiographic disease patterns suggest its possible diagnostic use as an indicator of stress-induced ventricular decompensation.     

Assessment of cold stress in outdoor work

This study was performed to determine the efficacy of balloon-expandable stents in the treatment of branch pulmonary artery-stenoses and conduit stenosis in children. A total of eight stainless steel stents were implanted in seven patients. Three patients had tetralogy of Fallot with pulmonary artery stenosis following total correction, one patient had conduit stenosis following correction of transposition of the great arteries, one patient had intra-cardiac conduit stenosis after septation for single left ventricle, and two patients had pulmonary artery stenosis after Fontan operation. Six stents were placed in the branch pulmonary arteries, one in the extracardiac conduit, and one in the intracardiac conduit. The mean age at implantation was 13 +/- 3 years and the mean weight 37 +/- 12 kg. Follow-up time ranged from 0.3-2 years. The diameter of pulmonary arteries with stenoses increased from 5.6 +/- 2.2 mm to 10.6 +/- 1.8 mm (n = 7). The systolic pressure gradient decreased from 56 +/- 26 mmHg to 22 +/- 16 mmHg (n = 5). No embolization or thrombotic event has been noted. One stent placed in the intracardiac conduit was compressed and fractured. These data indicate that balloon-expandable stents are useful in the treatment of pulmonary artery branch stenoses and extracardiac conduit stenosis in children. The use of stents for intracardiac stenosis may result in stent fracture.     

Effect of acetazolamide on sodium and potassium absorption in the sheep forestomach

The purpose of the present study was to determine whether the linear relationship between CO2 output (VCO2) and pulmonary ventilation (VE) is altered during incremental cycling performed after exercise-induced metabolic acidosis. Ten untrained, female subjects performed two incremental cycling tests (15 W x min(-1) up to 165 W) on separate days. One incremental exercise test was conducted without prior exercise, whereas the other test was preceded by a 1-min bout of maximal cycling. The ventilatory equivalent for O2 (VE/VO2) was only elevated above control values at 15-60 W during incremental cycling performed after high-intensity exercise. In contrast, the ventilatory equivalent for CO2 (VE/VCO2) was significantly increased above control levels at nearly every work stage of incremental work (all except 165 W). Hyperventilation relative to VCO2 was confirmed by the significantly lower end-tidal CO2 tension (P(ET)CO2) obtained throughout the incremental cycling that was performed after high-intensity exercise (except at 165 W). VE and VCO2 were significantly correlated under both treatment conditions (r > 0.99; P < 0.001). Moreover, both the slope and y-intercept of the linear regression were found to be significantly elevated during the incremental cycling performed after high-intensity cycling compared to control conditions (P < 0.01). The increase in the slope of the VE-VCO2 relationship during incremental exercise performed under these conditions does not represent an uncoupling of VE from VCO2, but could be accounted for by the significantly lower P(ET)CO2 observed during exercise.     

Smaller lungs in women affect exercise hyperpnea

We subjected 29 healthy young women (age: 27 +/- 1 yr) with a wide range of fitness levels [maximal oxygen uptake (VO2 max): 57 +/- 6 ml . kg-1 . min-1; 35-70 ml . kg-1 . min-1] to a progressive treadmill running test. Our subjects had significantly smaller lung volumes and lower maximal expiratory flow rates, irrespective of fitness level, compared with predicted values for age- and height-matched men. The higher maximal workload in highly fit (VO2 max > 57 ml . kg-1 . min-1, n = 14) vs. less-fit (VO2 max < 56 ml . kg-1 . min-1, n = 15) women caused a higher maximal ventilation (VE) with increased tidal volume (VT) and breathing frequency (fb) at comparable maximal VT/vital capacity (VC). More expiratory flow limitation (EFL; 22 +/- 4% of VT) was also observed during heavy exercise in highly fit vs. less-fit women, causing higher end-expiratory and end-inspiratory lung volumes and greater usage of their maximum available ventilatory reserves. HeO2 (79% He-21% O2) vs. room air exercise trials were compared (with screens added to equalize external apparatus resistance). HeO2 increased maximal expiratory flow rates (20-38%) throughout the range of VC, which significantly reduced EFL during heavy exercise. When EFL was reduced with HeO2, VT, fb, and VE (+16 +/- 2 l/min) were significantly increased during maximal exercise. However, in the absence of EFL (during room air exercise), HeO2 had no effect on VE. We conclude that smaller lung volumes and maximal flow rates for women in general, and especially highly fit women, caused increased prevalence of EFL during heavy exercise, a relative hyperinflation, an increased reliance on fb, and a greater encroachment on the ventilatory "reserve." Consequently, VT and VE are mechanically constrained during maximal exercise in many fit women because the demand for high expiratory flow rates encroaches on the airways' maximum flow-volume envelope.     

Assessment of ventilatory neuromuscular drive in patients with obstructive sleep apnea

The presence of abnormalities of the respiratory center in obstructive sleep apnea (OSA) patients and their correlation with polysomnographic data are still a matter of controversy. Moderately obese, sleep-deprived OSA patients presenting daytime hypersomnolence, with normocapnia and no clinical or spirometric evidence of pulmonary disease, were selected. We assessed the ventilatory control and correlated it with polysomnographic data. Ventilatory neuromuscular drive was evaluated in these patients by measuring the ventilatory response (VE), the inspiratory occlusion pressure (P.1) and the ventilatory pattern (VT/TI, TI/TTOT) at rest and during submaximal exercise, breathing room air. These analyses were also performed after inhalation of a hypercapnic mixture of CO2 (delta P.1/delta PETCO2, delta VE/delta PETCO2). Average rest and exercise ventilatory response (VE: 12.2 and 32.6 l/min, respectively), inspiratory occlusion pressure (P.1: 1.5 and 4.7 cmH2O, respectively), and ventilatory pattern (VT/TI: 0.42 and 1.09 l/s; TI/TTOT: 0.47 and 0.46 l/s, respectively) were within the normal range. In response to hypercapnia, the values of ventilatory response (delta VE/delta PETCO2: 1.51 l min-1 mmHg-1) and inspiratory occlusion pressure (delta P.1/delta PETCO2: 0.22 cmH2O) were normal or slightly reduced in the normocapnic OSA patients. No association or correlation between ventilatory neuromuscular drive and ventilatory pattern, hypersomnolence score and polysomnographic data was found; however a significant positive correlation was observed between P.1 and weight. Our results indicate the existence of a group of normocapnic OSA patients who have a normal awake neuromuscular ventilatory drive at rest or during exercise that is partially influenced by obesity.     

Doppler stress echocardiography of the left and right ventricle: a new echo device to quantify left ventricular backward failure

OBJECTIVES: A novel non-invasive procedure which evaluates left-right ventricular interaction is introduced. This procedure is suitable for the classification of congestive heart failure. METHODS: In 48 patients showing mild, moderate or advanced stage congestive heart failure (NYHA I-III) Doppler echocardiography was performed at rest, during and after submaximal bicycle exercise. Mitral (m) and tricuspid (t) filling parameters were determined: early diastolic (VEm, VEt) and atrial maximal velocities (VAm, VAt), the velocity integrals (Em, Et, Am, At) and the corresponding ratios (VE/VAm, VE/VAt, E/Am, E/At). Group 1 (n = 29) was composed of those patients presenting with a VE/VAm < 1 at rest. Four individuals (group 2) were found to have a VE/VAm ratio < 1 during exercise only. Six other patients showing a dilated left ventricle or an ejection fraction of less than 40% produced false negative results in left ventricular Doppler examination (VE/VAm > 1) at rest and during exercise (group 3). In 9 cases (group 4) systolic function, size and Doppler echocardiographic parameters of the left ventricle were proven to be normal. RESULTS: The VE/VAt-ratio decreased notably during exercise (p < 0.05) but increased again after exercise in group 3. In the groups 1 and 2 similar changes occurred as well, however not to a significant degree. In group 4, exercise VE/VAt ratio did not differ from values seen at rest or during recovery (variability 4%). CONCLUSION: The results of this study indicate, that high sensitivity towards left ventricular backward failure can be achieved for Doppler stress echocardiography by extending the examination to right-sided diastolic parameters.     

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.     

Stretching

BACKGROUND: It has recently been reported that total daily energy expenditure (TDE) is increased in patients with chronic obstructive pulmonary disease (COPD) and it was hypothesised that these patients may have a decreased mechanical efficiency during activities. The purpose of the present study was to measure the mechanical efficiency of submaximal leg exercise, and to characterise patients with a potentially low efficiency in terms of body composition, resting energy expenditure, lung function, and symptom limited exercise performance. METHODS: Metabolic and ventilatory variables were measured breath by breath during submaximal cycle ergometry exercise performed at 50% of symptom limited achieved maximal load in 33 clinically stable patients with COPD (23 men) with forced expiratory volume in one second (FEV1) of 40 (12)% predicted. Net mechanical efficiency was calculated adjusting for resting energy expenditure (REE). RESULTS: Median mechanical efficiency was 15.5% and ranged from 8.5% to 22.7%. Patients with an extremely low mechanical efficiency (< 17%, n = 21) demonstrated an increased VO2/VE compared with those with a normal efficiency (median difference 4.7 ml/l, p = 0.005) during submaximal exercise. There was no difference between the groups differentiated by mechanical efficiency in blood gas tensions at rest, airflow obstruction, respiratory muscle strength, hyperinflation at rest, resting energy expenditure or body composition. There was a significant difference in total airways resistance (92% predicted, p = 0.03) between the groups differentiated by mechanical efficiency. CONCLUSIONS: It is concluded that many patients with severe COPD have decreased mechanical efficiency. Furthermore, based on the results of this study it is hypothesised that an increased oxygen cost of breathing during exercise contributes to the decreased mechanical efficiency.     

Estimation of shunt flow in coronary-pulmonary fistula by lung perfusion scintigraphy with technetium-99m macroaggregated albumin

The shunt flow from the coronary artery to pulmonary arteries was evaluated in 6 patients with coronary-pulmonary fistula by lung perfusion scintigraphy with technetium-99m macroaggregated albumin. In 2 patients, whose degree of visualization of pulmonary arteries by coronary angiography was relatively high, lung perfusion scintigrams demonstrated the defects at the distal of coronary-pulmonary fistulas.     

G1 accumulation caused by iron deprivation with deferoxamine does not accompany change of pRB status in ML-1 cells

In hypertension, several factors disturb coronary circulation and the metabolic reserve of the heart. This study was undertaken to test whether in hypertensive patients global and regional left ventricular (LV) function is related during exercise to the presence of significant coronary stenosis and whether lowering of coronary perfusion pressure through rapid normalization of the diastolic pressure may modify the dynamics of the left ventricle. Thirty-five patients with mild to moderate hypertension undergoing coronary angiography for the evaluation of chest pain were included in the study; upright bicycle exercise echocardiography tests were performed without therapy and 1 day later 1 h after sublingual administration of nifedipine. LV ejection fraction and regional wall motion scores were evaluated and compared at baseline, peak exercise, immediate postexercise, and recovery phases in each test through digital on-line storing of echocardiographic images. Twenty-one patients had normal coronary arteries (group 1) and 14 significant coronary stenoses (group 2); age, gender, heart rate, blood pressure, left ventricular diameter and mass index, and ejection fraction were similar in the two groups. At peak exercise LV ejection fraction slightly increased in group 1, whereas it slightly decreased in group 2 (both during the test without therapy and after nifedipine administration). All patients in group 1 had normal left ventricular wall motion during exercise; 13 of 14 patients in group 2 had LV wall motion abnormalities at peak exercise. Nifedipine did not produce any effect on LV regional wall motion in group 1, but it induced significant changes in LV regional wall motion in seven patients in group 2. Changes in LV wall motion between the two test groups were related to the number of the stenotic coronary vessels: the normal exercise test before and after therapy and the two normalized tests after nifedipine administration were in fact observed in patients with one-vessel disease, whereas worsening or changes in the site of ischemia were observed only in patients with multivessel disease. Regional and global left ventricular dynamics during exercise is mainly dependent on the existence of significant coronary artery disease. Rapid decrease of blood pressure does not alter the regional dynamics of the left ventricle during exercise in patients without coronary artery disease, but it may induce normalization, worsening, or changes in the site of wall motion abnormalities in hypertensives with significant coronary stenoses.     

Prediction of exercise capacity after lung resection in patients with chronic airflow limitation

To assess the usefulness of a method for predicting postoperative peak oxygen uptake based on lost lung function after lung resection (VO2peak-PPO) and to establish the underlying physiological foundation for the relation between VO2peak-PPO and the measured postoperative value VO2peak-PO), we studied 29 patients (26 men) [age 60 (SD9)] with chronic airflow limitation [FEV1 = 66 (SD13)%] undergoing lobectomy or major pulmonary resection to treat lung cancer. The patients were assigned to groups according to whether postoperative exercise tolerance was considered to be limited by exhaustion of ventilatory reserve (LV) or not (NLV). Data to estimate postoperative pulmonary function was obtained one week before surgery: patients performed pulmonary function tests and exercise tests on a treadmill; dyspnea was also evaluated and perfusion scintigraphs were obtained. Pulmonary function, exercise tolerance and dyspnea were evaluated again approximately five months after surgery. The mean difference between VO2peak-PPO and VO2peak-PO was -0.034 (CI 0.293 to -0.348) l.min-1 and the between-group correlation coefficient was 0.76. The correlation between VO2peak-PPO and VO2peak-PO was 0.86 (SE 0.1) [0.89 (SE 0.13) for LV (n = 14) patients and 0.85 (SE 0.16) for NLV (n = 15) patients]. The correlations after adjusting for preoperative VO2peak-PPO were 0.73 (SE 0.2) and 0.35 (SE 0.27) for LV and NLV patients, respectively. We conclude that VO2peak-PPO provides a valid but only moderately precise estimate of VO2peak-PO. Only in LV patients is there a true relation between a decrease in VO2peak and loss of lung function.     

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.     

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.