Effect of natural allergen exposure on non-specific bronchial reactivity in asthmatic farmers.

The aim of the study was to assess the seasonal variability of non-specific bronchial reactivity (NSBR) evaluated with methacholine in asthmatic farmers allergic to pollens. Twenty farmers (16 male and four female) with allergy to pollens, e.g. 'Graminae' and 'Parietaria', entered the study. None of the patients had been previously treated with specific immunotherapy. Patients underwent a methacholine challenge at the first visit and then in the subsequent seasons. Four groups of tests were obtained according to the period when the challenge was performed. Group 1: challenges performed in December, January and February; group 2 in March, April and May; group 3 in June, July and August; group 4 in September, October and November. PD20 values were expressed as the natural logarithm of the cumulative dose of methacholine causing at least a 20% fall in FEV1. Bronchial hyperreactivity was highest in summer, followed by spring and autumn; in winter it was much lower. Multiple group analysis (ANOVA) showed statistically significant differences between the groups (P < 0.01). When the groups were compared individually, statistically significant differences existed only between group 1 (winter) and each of the other groups, respectively 2 (spring) (P = 0.02), 3 (summer) (P = 0.004) and 4 (autumn) (P = 0.02). The results underlined the importance of allergic inflammation in determining changes in NSBR. In the region where the study was carried out (central Italy), the grass and Paretaria pollination lasts from March to November. Therefore, farmers had a progressive increase in NSBR from spring to summer and a decrease in fall as a consequence of the varying pollen concentration in different seasons. The level of allergen exposure is, in fact, the main factor that determines the severity of bronchial inflammation, thus affecting NSBR.

Biofeedback systems architecture.

The capability for a dialysis machine to use a measurement of the patient's status to automatically tune the dialysis session on-line is commonly addressed by physicians and bioengineers working in the hemodialysis field as "biofeedback." This paper presents the basics of mathematical modeling and control theory normally used in bioengineering, together with some advanced techniques, such as adaptive and multi-input/multi-output control systems. The architectural requirements for implementing biofeedback techniques in renal replacement therapy are then discussed, with due attention paid to the safety aspects, which play a central role in machines hosting such new techniques as well as their therapeutic mission. Finally, the blood volume tracking system, which is aimed at performing the intradialytic water removal, while maintaining a balance inside the body fluids compartments and thus preserving cardiovascular stability, is used as a paradigmatic example of such a class of advanced techniques. The significant results shown by the blood-volume-controlled treatments during a multicenter study focused on its clinical application (30% reduction of intradialysis collapses, 13% reduction of interdialysis symptoms) indicate the technical feasibility and the remarkable benefits of such systems, which get closer to a structurally complete artificial kidney.

Effects of automatic blood volume control over intradialytic hemodynamic stability.

Due to the crucial role of hypovolemia in the genesis of dialysis-induced hypotension, we have evaluated whether the automatic control of the intradialytic blood volume (BV) decrease along a preset trajectory might be beneficial to the hemodynamic stability during treatment. Five frequently hypotensive HD patients were studied and a 3-period-protocol (A1-B-A2) was adopted, each period lasting 6 sessions per patient. During the B periods the patient BV decrease was kept along a predefined profile, thanks to an automatic system with a retroactive control of both the ultrafiltration rate (UFR) and dialysate conductivity (DC); instead, during the A periods, conventional HD was performed, with linear UFR and constant DC, inducing a spontaneous decrease in BV. The intradialytic BV behaviour was much more stable during the B-periods (-10.2 +/- 1.4% by the end of the treatment) than during the A1 (-11.2 +/- 3%) and A2 periods (-11.5 +/- 2.5%). Only one dialysis-hypotension episode was observed during the B periods, compared to 8 and 5 during the A1 and A2 periods, respectively (p < 0.05). The automatic control of the BV changes during dialysis could improve the intra-treatment cardiovascular stability in critically-ill patients.