Leif Bjermer

Perfusion abnormalities in pulmonary embolism studied with perfusion MRI and ventilation-perfusion scintigraphy: an intra-modality and inter-modality agreement study

To compare perfusion magnetic resonance imaging (MRI) and ventilation‐perfusion scintigraphy (V‐P scan) in the study of perfusion abnormalities in pulmonary embolism (PE) and to compare the PE results to the findings previously reported for pneumonia and chronic obstructive pulmonary disease (COPD), in terms of perfusion abnormalities.

Perfusion magnetic resonance imaging of the lung: characterization of pneumonia and chronic obstructive pulmonary disease. A feasibility study

Perfusion magnetic resonance (MR) imaging is a promising new method for detection of perfusion defects in the diagnosis of pulmonary embolism. In the present study we evaluated the first‐pass characteristics of perfusion MR imaging in patients with pneumonia or chronic obstructive pulmonary disease (COPD), frequent differential diagnoses to pulmonary embolism. Dynamic contrast‐enhanced MR images of 12 patients with acute pneumonia and 13 patients with exacerbation of COPD were acquired in both the coronal and transaxial planes (an inversion recovery prepared gradient‐echo sequence using 0.05 mmol/kg gadodiamide/injection). The MR images and the signal intensity (SI) versus time curves were characterized for each disease entity and compared with normal lung and the findings in pulmonary embolism from our previous study. The perfusion MR images of pneumonia showed distinct regions of increased contrast enhancement; in COPD with signs of emphysema (11 of the 13 COPD patients), the images showed a coarse pattern of reduced contrast enhancement. The SI versus time curves of pneumonia, COPD with signs of emphysema, and normal lung were statistically different, the respective pooled SI values (±95% CI) being as follows: mean baseline SI, 20.7 (1.1), 7.4 (0.4), and 8.5 (0.3); mean peak SI, no peak, 12.9 (1.5), and 27 (4.6); and mean max change of SI in percent, 110 (27), 79 (22), and 205 (52). Perfusion MR imaging of pneumonia and COPD with signs of emphysema showed first‐pass that were characteristics promising for diagnostic use. Both the MR images and the SI versus time curves were different from the perfusion characteristics in normal lung and pulmonary embolism shown previously. J. Magn. Reson. Imaging 2000;12:224–231.

Salmeterol and physical performance at ‐15°C in hghly trained nonasthmatic cross‐country skiers

The aim of this double‐blind. placebo‐controlled, cross‐over study was to investigate possible improvement in physical performance at an ambient temperature of −15°C by an inhaled dose of 50 μg salmeterol in 8 highly trained nonasthmatic cross‐country skiers. FEV1 was measured before, during and after the treadmill exercise protocol, which consisted of a warm‐up run. runs of 10 min at 90%, and 5 min at 80%VO2max, followed by a timed run to exhaustion. Despite a significant improvement in FEV1, salmeterol did not have a beneficial effect on heart rate, blood lactate concentration, respiratory exchange ratio, oxygen uptake or minute ventilation during the exercise protocol. Running time to exhaustion was not significantly different from placebo. This lack of enhancement of exercise performance in healthy endurance athletes further supports the recent approval of salmeterol for prophylactic use by asthmatic athletes during training and competition.

A study of the association between exercise-induced wheeze and exercise versus methacholine-induced bronchoconstriction in adolescents

Among asthmatics, exercise‐induced wheeze (EIW) is a frequent symptom, and 40–77% of asthmatics demonstrate exercise‐induced bronchoconstriction (EIB). In the North‐Trøndelag population‐based survey of 8,571 adolescents (YOUNG‐HUNT), 26% reported wheeze during the previous 12u2003months (current wheeze). Of those subjects, 50% reported EIW. The aim of the present study was to investigate the association between EIW and EIB in randomly selected adolescents with EIW as the only or predominant asthma‐like symptom, and to relate our findings to results from methacholine bronchoprovocation tests (MT) and measurements of exhaled nitric oxide (ENO). Sixty‐three subjects with current wheeze induced by exercise, but not by allergen exposure, were investigated using a treadmill exercise test (ET) and measurements of ENO. Fifty‐eight subjects completed a MT on a separate study day. EIB was defined as a fall of ≥u200a10% in the forced expiratory volume in 1u2003second (FEV1) after exercise (ΔFEV1%ex). Twenty‐one subjects (33%) had EIB and 33 (57%) had a positive MT. The degree of reported dyspnea during the ET was not correlated to the ΔFEV1%ex. The correlation between EIB and methacholine‐induced bronchoconstriction (MIB) was poor, and the ΔFEV1%ex was more pronounced in smokers than in non‐smokers. Moreover, ENO was not increased in subjects with positive vs. negative ET. Hence, EIW, when reported as the only or predominant asthma‐like symptom, was linked to EIB in only one‐third of the patients. We conclude that EIW is a poor predictor of EIB in epidemiological studies. The poor correlation between EIB and MIB indicates that these two tests measure different mechanisms of bronchial hyper‐responsiveness.

A closed-chest pulmonary artery occlusion/reperfusion model in the pig: detection of experimental pulmonary embolism with MR angiography and perfusion MR imaging.

RATIONALE AND OBJECTIVESnTo establish a pig model suitable for imitating pulmonary emboli to facilitate research in the diagnosis of pulmonary embolism.nnnMETHODSnThirteen animals were anesthetized, mechanically ventilated, and subjected to pulmonary artery catheterization initiated from the right external jugular vein. With the use of a Swan-Ganz catheter, repetitive occlusion/reperfusion maneuvers were done at different locations of the pulmonary arterial tree. Conventional pulmonary angiography, MR angiography, and perfusion MR imaging were performed.nnnRESULTSnThe model remained hemodynamically stable throughout the 13 experiments, without any significant difference between the blood pressure measurements at the start and at the end of the right-heart and pulmonary artery catheterizations. In each of the nine animal experiments that investigated MR imaging, four of four using perfusion MR imaging (proximal and distal occlusions) and five of five using MR angiography (larger pulmonary artery occlusions), all repeated pulmonary artery occlusions were successfully performed (reproducibility of 100%).nnnCONCLUSIONSnThe closed-chest pulmonary artery occlusion/reperfusion model in the pig allowed repetitive, controlled imitations of pulmonary emboli at different levels of the pulmonary artery in the same experiment. MR angiography and perfusion MR imaging were adequate to detect the pulmonary artery occlusions and the nonperfused lung regions, respectively. The model may be a helpful tool for future research in this field.