Biomedical subjects
Publications and source records attributed to E Stranden.
Theoretical calculations are reported of the mean respiratory dose from inhalation of short-lived radon daughters under different ventilation condtions. These calculations are related to the variations in ventilation practice over different periods of time.
Measurements of the radioactivity in some common building materials in Norway are reported, together with calculations of the gamma-ray exposure from walls of different materials. Model rooms are used in calculations of the mean exposure inside concrete, brick and light-weight expanded clay aggregate buildings. These calculations give very good agreement with previous experimental results. The radiological implications of using building materials with high concentrations of radioactivity are also discussed.
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The microcirculation in the skin was assessed in 31 patients with sequelae from local cold injuries (LCI) in the extremities. All patients reported cold intolerance 3-4 years after the primary cold injury, which they sustained during military service. The used methods were laser Doppler fluxmetry, transcutaneous oxygen tension (TCpO2) and vital capillaroscopy. Neurovascular reflexes were stimulated by deep inspiration, digital cuff occlusion of venous and arterial circulation, neck cooling with an ice bag and water immersion at 5 and 15 degrees C. Unaffected lower or upper extremities were also investigated as part of a search for generalized effects of LCI. During immersion in ice water the cold-induced vasodilation (CIVD or Lewis' 'hunting' reaction) was profoundly delayed or abolished in the affected limbs. These also showed the lowest skin temperatures after 15-20 min of immersion. Additionally, a delayed CIVD was found in the unaffected feet of patients with a previous hand injury. TCpO2 resting values were decreased in the patients, but oxygen reappearance time, oxygen recovery index, postocclusive reactive hyperemia and the venoarterial reflex were normal. No capillary abnormalities were found. In conclusion, LCI induces disturbances in the CIVD, impairs cold tolerance and increases the risk of future cold injuries. These data demonstrate disturbances of reflex mechanisms mediated by the central nervous system. Neurophysiologic factors seem to be more important than ischemic mechanisms in the pathophysiology of late sequelae from LCI.
Computed tomography was used in 12 patients to investigate the distribution of oedema in the soft tissue compartments of lower limbs with deep venous thrombosis. Oedema was evenly distributed throughout the subcutis and the muscular compartments in tomograms obtained 25 cm proximal to the ankle. Significantly less swelling in the muscular compartments was found 10 cm proximal to the ankle. Interstitial fluid hydrostatic pressure was measured in the subcutis, and in anterior and posterior muscular compartments, and was significantly increased in all cases. Except for one case, the recorded pressures were well below 30 mmHg, which is considered the limit above which compartment syndromes occur. Tissue compliance was significantly lower in muscular compartments than in the subcutis.
Laser Doppler flowmetry (LDF) was used to evaluate skin post-ischaemic reactive hyperaemia. Four groups of subjects were examined: healthy young and elderly controls (groups A and B) and patients with intermittent claudication or critical ischaemia (groups C and D). The occlusion tourniquet was placed just proximal to the patella, and measurements were performed on the toe pulp (study 1) and leg skin (study 2). The hyperaemic response on both pulp and leg skin was delayed, diminished and prolonged in claudicators compared with controls. On the toe pulp most patients with critical ischaemia had no hyperaemic response at all, indicating that the local vasodilatory capacity was exhausted at rest. The time from tourniquet deflation to pulp peak hyperaemia was the parameter that most clearly separated between the groups [Group A: 21.5 secs (median), group B: 17 secs, group C: 73 secs and group D: greater than 300 secs]. The time from tourniquet deflation to the first increase in flux is probably dependent on hemodynamic factors in the large extremity vessels, and it is possible that this parameter could be used to define levels of hemodynamic significant stenosis in patients with lower limb atherosclerosis. The results also indicate that laser Doppler flowmetry performed during stress testing may be of value in determining appropriate amputation levels.
Measurements of ankle pressure index (API) and arterial flow velocity including calculation of pulsatility index (PI) from the common femoral and pedal arteries were performed in 89 limbs of 75 patients before and after percutaneous transluminal angioplasty (PTA) (63 iliac and 26 femoropopliteal). A pulsed wave Doppler ultrasound flowmeter was used. An increase of API at rest of at least 0.15 or the absence of pressure drop after exercise following PTA was used as criteria for a hemodynamically successful angioplasty. In patients with hemodynamically successful PTA of an iliac obstruction PI increased from 4.2 to 8.6 (p less than 0.001); 91 per cent of these patients improved clinically. When iliac angioplasty was hemodynamically unsuccessful, PI remained unchanged; 11 per cent of these patients improved clinically. All limbs with hemodynamically successful PTA of a femoropopliteal obstruction improved clinically and PI increased from 3.1 to 8.7 (p less than 0.001). After hemodynamically unsuccessful femoropopliteal PTA, PI remained unchanged though 25 per cent of these patients improved clinically. These results illustrate that measurement of arterial flow velocity with calculation of PI may be a useful supplement for the functional evaluation of the effect of PTA, since symptomatic response alone may be unreliable.
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