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Biomedical subjects

F Paolini

Publications and source records attributed to F Paolini.

17 recordsLinked to original sources
PubMed2001

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.

Agriculture↗
PubMed1999

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.

Artificial Organs↗
PubMed1998

Blood volume regulation during hemodialysis.

Hemodialysis (HD)-induced hypotension may be precipitated by severe hypovolemia. To avoid the appearance of destabilizing hypovolemias, we have developed a biofeedback control system for intradialytic blood volume (BV)-changes modeling. The system, incorporated in a dialysis machine, is based on a multivariable closed-loop control with a dependent output variable, the BV changes, and two independent control variables, the ultrafiltration rate (Qf) and dialysate conductivity (DC). The relative BV changes occurring during HD are measured by an optical device. The Qf and DC are continuously adjusted by the control model during the treatment to minimize any discrepancies between the ideal targets for the BV, the patient's body weight reductions, and the experimentally obtained results. The system manages three kinds of errors: in BV changes, the total weight loss, and the sodium balance. The latter is controlled by a dedicated kinetic model that continuously calculates the equivalent DC and, by the end of the session, tends to make the sodium balance the same as the one obtained in conventional HD with constant DC. This system's capacity to improve intradialytic hemodynamic tolerance has been assessed in a crossover study of eight highly symptomatic patients. Conventional HD (CHD; period A) was compared with blood volume-controlled dialysis sessions (BV-CHD; period B) following a protocol with an A1-B-A2 sequence, with each period lasting 1 month. A lower decrease in BV (-10.6%) was obtained during BV-CHD (period B) compared with CHD (-12.3% in period A1 and -12.5% in period A2). The predialysis to postdialysis systolic arterial pressure changes were lower in period B (-12.4%) than in period A (-20% in A1 and -17.5% in A2; P < 0.05) despite similar total Qf and mean treatment times. A significant reduction in the number of severe hypotensive episodes (three in period B v 26 in period A1 and 16 in period A2; P < 0.05) and the overall incidence of complaints, especially of muscular cramps, was found in BV-CHD. These results were reflected in a reduced need for therapeutically administered isotonic saline in each session (60 mL in B v160 mL in A1 and 95 mL in A2; P < 0.05). In conclusion, the proposed biofeedback system for intradialytic BV control may be useful to avoid severe hypovolemic states, to stabilize BV by modeling its trend, and to avoid reaching individual critical BV thresholds in hypotension-prone patients.

Blood Pressure↗
PubMed1998

A new biosensor for continuous monitoring of the spent dialysate urea level in standard hemodialysis.

This study gives the results in terms of precision and repeatability of a new on-line urea monitoring system (Ureascan P2 Hospal) capable of measuring the urea concentrations in the spent dialysate. The Ureascan P2 Hospal (UP2H), fitted on single-pass dialysis machines (Integra-Hospal), functions by the presence of a disposable mini-reactor containing urease. The passage through the reactor of a minimum quantity of spent dialysate from the filter diluted with a pH 7 buffer solution (1 ml/min) increases its ionic strength, which is detected by a differential measurement of conductivity in proportion to the urea concentration in the dialysis liquid. We studied 13 dialysis sessions, with bicarbonate buffer, in 8 anuric patients. From 4 to 7 dialysate samples were taken during each treatment to determine the urea and 65 samples were analysed overall. Urea values from the UP2H were compared with those measured on the Dimension Du Pont analyser. Simple linear regression analysis showed an excellent correlation between the 2 measuring methods (r=0.987; p<0.001). The Bland-Altman test gave an average difference between the urea values measured with the UP2H and in the laboratory of 1.3+/-1.2 mg/dl. The agreement limits between 2 SD were -1.2 mg/dl and +3.8 mg/dl respectively. In conclusion, the UP2H we have developed has proved to be a reliable and very useful instrument for adapting, through the urea kinetic mathematical models, the dialysis dose for individual patients.

Anuria↗
PubMed1998

Model-based dialysis adequacy prediction by continuous dialysate urea monitoring.

A modeling approach for on-line estimation of urea kinetics from continuous measurement of urea concentration in the effluent dialysate stream (DUN) is presented. On-line identification of urea kinetics response parameters is used to predict and update dialysis adequacy during the treatment. Dialysis adequacy can be quantified in several ways, but its strict dependence on final urea concentration is a major fact. For this reason, a good predictive skill on the time course of DUN may enable better performances in the control of dialysis outcome by treatment parameters adjustment. A post-filter enzymatic sensor performs continuous measurement of DUN on patients undergoing standard haemodialysis. To get an early prediction of the end dialysis urea level, the solution of a variable volume double-pool (VVDP) model is used, whose parameters are identified at each time on the basis of the past DUN history Unlike the variable volume single-pool (VVSP) model, this enables a prompt and accurate estimation of the final DUN. In fact, after 75 min the estimates always differ by less than 10% from the values measured by the sensor at the end of the treatment. Moreover, values predicted by the model in the last hour always lie within 1% of measured final values. Real-time knowledge of an analytic expression for whole DUN time course also enables the accurate prediction of total removed urea, with no need of cumbersome dialysate collection techniques.

Aged↗
PubMed1995

Hemoscan: a dialysis machine-integrated blood volume monitor.

We describe an opto-electronic device capable of measuring the hemoglobin concentration (Hgb) non-invasively and continuously, hence the percentage changes in blood volume (BV) during dialysis treatment by means of the optical absorption of monochromatic light by the blood in the arterial line. This method has been validated during several in vitro and in vivo tests, during which the system has shown a low sensitivity to all the common intra-dialytic interference factors, such as oxygen saturation (max. err. = 1.6%), blood flow (max. err. = 1.8%), osmotic pressure (max. err. = 0.7%) and hydraulic pressure (max. err. = 0.6%), a high precision (std. err. < 0.1 g/dl) and a good accordance (Hgb mean err. = 0.1 g/dl; std. err. = 0.38 g/dl; BV mean err. = 0.1%; std. err. = 1.6%) with the corresponding values derived from standard laboratory tests.

Absorption↗
PubMed1995

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.

Biofeedback, Psychology↗
PubMed1995

Autonomic nervous function and blood volume monitoring during hemodialysis.

We studied the autonomic reflex response to hypovolemia during HD by means of spectral analysis of heart rate variability (SAHRV) in 10 hypotension prone (group A) and 10 hemodynamically stable patients (group B). UF rate normalized per total body water and blood volume fall were similar in the two groups. The sympatho-vagal balance index, calculated as the ratio between the integrals of the spectrum in the low (0.02-0.15 Hz) and in the high frequency range (0.2-0.35 Hz) rose in group B progressively from the beginning of the treatments, reaching a top at the 90th minute and remained subsequently high until the end. On the contrary this index did not show remarkable increases in group A. The differences between the two groups were statistically significant at 0 (4.6 +/- 2.9 vs 1.5 +/- 1.3), 60th (8.3 +/- 7.8 vs 2.2 +/- 2.6), 90th (17.9 +/- 13.4 vs 3.7 +/- 2.8), 150th (8.8 +/- 3.7 vs 2.7 +/- 2.8) and 210th minute (8.6 +/- 5.0 vs 2.9 +/- 2.5). In conclusion SAHRV shows an impairment of autonomic reflex response to hypovolemia in hypotension-prone patients.

Adult↗
PubMed1993

Continuous on-line optical absorbance recording of blood volume changes during hemodialysis.

Conventional techniques that measure blood volume changes during hemodialysis are invasive, hard to reproduce, and provide only intermittent evaluations. To overcome these drawbacks, we have developed an optoelectronic instrument that estimates intradialytic blood volume percentage changes by the optical absorbance of blood. This device is based on the absorption of light transmitted through blood, which is directly related to the hemoglobin concentration. A personal computer interfaced to the device provides a continuous on-line graphic display of the hemoglobin levels and the percentage changes in blood volume. The noninvasive measurement of dialysis blood volume changes by an optical method may be helpful in detecting the appearance of severe hypovolemia that can be dangerous in critically ill patients.

Absorption↗
PubMed1990

A haemodynamic study of hypotension during haemodialysis using electrical bioimpedance cardiography.

Continuous recording of beat-to-beat changes in haemodynamic parameters such as arterial pressure, heart rate, stroke volume, cardiac output, and total peripheral resistance, was done in 52 uraemic patients. The study was performed during the haemodialysis session, using a system combining a personal computer, an arterial pressure recorder, and an electrical bioimpedance cardiography monitor. Forty-six episodes of dialysis-induced hypotension occurred in 26 patients. Systolic arterial pressure and total peripheral resistance decreased by -39.3 +/- 2% and -36.3 +/- 4% respectively during acute hypotension; in contrast, there was an increase in cardiac output (+13.9 +/- 6.7%), while heart rate and stroke volume did not change significantly. It was possible to distinguish two types of collapse on the basis of heart rate behaviour: the classic 'tachycardiac' collapse with heart rate increase and stroke volume decrease, and the so-called 'bradycardiac' collapse with a paradoxical reduction in heart rate and an increase in stroke volume. 'Bradycardiac' collapses were observed in 54% of the cases. The administration of atropine in one patient resulted in an immediate increase in heart rate. The development of bradycardia and hypotension during haemodialysis seems to be related to a sudden parasympathetic vagal overactivity and could be attributed to the Bezold-Jarish reflex.

Adult↗
PubMed1977

[Methods for the sampling and tracing of caprolactam monomer dispersed in the air].

The problem of hygiene in the production of epsilon-caprolactam is very important; pollution of work room air is possible when the substance is stored, transported or packed in bags. In this work toxic and irritant properties of epsilon-caprolactam are described. Infrared spectroscopic, gas chromatrographic and spectrophotometric methods used by us, for the determination of epsilon-caprolactam traces, are also described.

Air Pollutants↗
PubMedDate not supplied

Automatic control of blood volume trends during hemodialysis.

Dialysis induced hypovolemia plays an important role in triggering intradialytic hypotension. The authors developed an automatic system (BVAC) with feedback changes in the ultrafiltration rate (UFR) and dialysate conductivity (DC) to match blood volume (BV) intradialytic profiles with the desired trajectories. The system consists of three subunits: (1) an optical probe to continuously detect the BV changes derived from hemoglobin changes, and (2) a dialysis machine interfaced with (3), a personal computer in which a time-dependent model is implemented. The model is based on a dynamic regulator that can set the actual BV changes against the corresponding desired values. Any discrepancy is offset by changes in UFR and DC. To verify the efficacy of the BVAC system in reducing intradialytic cardiovascular instability, five hypotension-prone patients were studied during a three period protocol (A1-B-A2) that lasted six sessions per period per patient. During periods A1 and A2, the dialysis procedure was conventional hemodialysis (HD) with linear UFR and constant DC. During period B, both UFR and DC were automatically regulated by the BVAC system. Mean BV reduction and its variability were lower during period B than during periods A1 and A2 (-10.2%, -11.3%, and -11.5, respectively). Episodes of hypotension were significantly (P < 0.05) fewer during period B (n = 1) than during periods A1 (n = 8) and A2 (n = 5). The therapeutic interventions defined as infused milliliters of isotonic and hypertonic solution were fewer during period B compared with periods A1 and A2. Total UF and end-dialysis plasma sodium concentrations did not differ in the three study periods. BVAC was effective in improving cardiovascular tolerance to treatment.

Aged↗
PubMedDate not supplied

Seasonal variability of non-specific bronchial responsiveness in asthmatic patients with allergy to house dust mites.

The aim of the study was to assess the seasonal variability of non-specific bronchial responsiveness to methacholine in allergic asthma. One hundred sixty-five patients (83 male and 82 female) entered the study: 86 subjects (group A) with allergy exclusively to mites and 79 (group B) with concomitant allergy to pollens, e.g., "Graminae" and "Parietaria." Inclusion criteria were the absence of sensitization to other allergens, no smoking habit, withdrawal from steroids, bronchodilators, sodium cromoglycate, and antihistamines for at least four weeks before enrollment, FEV1 > 70% of the predicted value, and absence of other respiratory diseases and of upper and lower respiratory tract infections for at least one month before the methacholine challenge. None of the patients had been previously treated with specific immunotherapy. Subjects of each group (A and B) underwent methacholine challenge at first visit and were divided into four subgroups according to the period when the challenge was performed. Subgroups A1 and B1 performed the challenge in December, January, and February; subgroups A2 and B2 in March, April, and May; subgroups A3 and B3 in June, July, and August; subgroups A4 and B4 in September, October, and November. PD20 values were expressed as the natural logs of the cumulative dose of methacholine causing at least a 20% fall in FEV1. Statistical analysis was carried out using multiple group analysis and Student's t-test. Results showed that the highest non-specific bronchial responsiveness was observed in autumn (ln PC20 = 4.54 +/- 1.51) in patients allergic to mites only (group A), and in summer (ln PC20 = 4.72 +/- 2.11) in those of group B. Multiple group analysis showed statistical significant differences between subgroups within each group (group A, p = 0.039; group B, p < 0.001). In patients allergic exclusively to house dust mites (group A), multiple comparisons and Student's t-test showed statistically significant differences between non-specific bronchial responsiveness (NSBR) assessed in autumn and those of other seasons (winter, p = 0.002; spring, p < 0.001; summer, p = 0.082). These results confirm that the level of allergen exposure may influence NSBR. Mite-allergic patients showed an increase of NSBR in autumn, possibly as a consequence of higher indoor mite concentration. However, mite- and grass-allergic patients had wider variations of NSBR, possibly reflecting changes in seasonal pollen concentration.

Adolescent↗
PubMedDate not supplied

Epidural pressure measurement in the rat.

An original device for the epidural pressure measurement in the rat is presented. The reliability of epidural pressure as an index of intracranial pressure is discussed and several possible causes of error are examined. The device has been tested under conditions both of transient and prolonged cerebral blood volume increase, obtained by venous outflow obstruction.

Animals↗