Environmental radioactivity at Stromboli (Aeolian Islands).

HPGe gamma spectrometry, thermoluminescence dosimetry, X-ray diffractometry and fluorescence techniques have been used to analyze the natural radionuclides content of soil and rock samples, air kerma and geochemical features on the island of Stromboli, belonging to the Aeolian Islands, in the Mediterranean Sea. The 214Bi, 238Ac, and 40K contents obtained are in agreement with the magmatic evolution of the rock formation, as shown by the correlations between radionuclide and chemical elements abundacies, depending on the various magmatic differentiation mechanisms. Correlations between radiometric, lithological and geochemical data have been assessed in order to obtain some hints on the geochronology of the magmatic products.

Seasonal variation of air kerma in the "Vulcano Porto" area (Aeolian Islands, Italy).

Air kerma was measured in the "Vulcano Porto" area of the Vulcano Island, belonging to the Aeolian Islands, in the Mediterranean Sea. Measurements were carried out using thermoluminescence dosimeters. The relationship between observed dose values and source lithology has been assessed. Data show a seasonal variation due to weather conditions but also probably related to features of the soils, making the variation more evident.

Patient-ventilator asynchrony during noninvasive ventilation: the role of expiratory trigger.

OBJECTIVE: Air leaks around the mask are very likely to occur during noninvasive ventilation, in particular when prolonged ventilatory treatment is required. It has been suggested that leaks from the mask may impair the expiratory trigger cycling mechanism when inspiratory pressure support ventilation (PSV) is used. The aim of this study was to compare the short-term effect of two different expiratory cycling mechanisms (time-cycled vs flow-cycled) during noninvasive inspiratory pressure support ventilation (NIPSV) on patient-ventilator synchronisation in severe hypoxemic respiratory failure. STUDY POPULATION: Six patients with acute lung injury (ALI) due to acquired immunodeficiency syndrome (AIDS)-related opportunistic pneumonia were enrolled in the protocol. INTERVENTION: Each subject was first studied during spontaneous breathing with a Venturi oxygen mask (SB) and successively submitted to a randomly assigned 20' conventional flow-cycling (NIPSVfc) or time-cycling inspiratory pressure support ventilation (NIPSVtc). The pre-set parameters were: inspiratory pressure of 10 cm H2O, PEEP of 5 cm H2O for the same inspired oxygen fraction as during SB. A tight fit of the mask was avoided in order to facilitate air leaks around the mask. The esophageal pressure time product (PTPes) and tidal swings (delta Pes) were measured to evaluate the patient's respiratory effort. A subjective "comfort score" and the difference between patient and machine respiratory rate [delta RR(p-v)], calculated on esophageal and airway pressure curves, were used as indices of patient-machine interaction. RESULTS: Air leaks through the mask occurred in five out of six patients. The values of PEEPi (< 1.9 cm H2O) excluded significant expiratory muscle activity. NIPSVtc significantly reduced PTPes, delta Pes, and delta RR(p-v) when compared to NIPS-Vfc [230 +/- 41 (SE) vs 376 +/- 72 cm H2O.s.min-1; 8 +/- 2 vs 13 +/- 2 cm H2O; 1 +/- 1 vs 9 +/- 2 br.min-1; respectively] with a concomitant significant improvement of the "comfort score". CONCLUSIONS: In the presence of air leaks a time-cycled expiratory trigger provides a better patient-machine interaction than a flow-cycled expiratory trigger during NIPSV.

Lung and chest wall mechanics in patients with acquired immunodeficiency syndrome and severe Pneumocystis carinii pneumonia.

The aim of this study was to assess the mechanical characteristics of the respiratory system in patients with acquired immune deficiency syndrome (AIDS) and acute respiratory distress syndrome (ARDS) caused by Pneumocystis carinii pneumonia (PCP). In 12 mechanically ventilated patients, total respiratory system mechanics was assessed using the technique of rapid airway occlusion during constant flow inflation, and was partitioned into lung and chest wall components using the oesophageal balloon technique. We measured interrupter resistance (Rint), which mainly reflects airway resistance, additional resistance (deltaR) due to viscoelastic behaviour and time constant inequalities, and static elastance (Est). In addition, the static inflation volume-pressure (V-P) curve was assessed. In eight patients, computed tomography scans were performed within 2 days of the assessment of respiratory mechanics. Compared to values reported in the literature for normal subjects, Est and deltaR were markedly increased in AIDS patients with PCP, whilst Rint exhibited a relatively smaller increase. These changes, which involved only the lung and airways, were mainly due to the reduction of ventilated lung units, but additional factors were involved to cause independent modifications of lung stiffness, airway calibre, and viscoelastic properties. The changes in Rint, deltaR, and Est were similar to those observed in other studies on patients with ARDS of different aetiologies. At variance with common observations in the latter patients, none of the AIDS patients with PCP exhibited an inflection point on the static inflation V-P curve, suggesting little or no alveolar recruitment during lung inflation. This finding could be related to the distinctive histopathology of Pneumocystis carinii pneumonia. Indeed, computed tomography revealed homogeneous diffuse interstitial and alveolar infiltration rather than the dense, dependent opacities observed in other studies on acute respiratory distress syndrome of different aetiologies.

The response behaviour of LiF:Mg,Cu,P thermoluminescence dosimeters to high-energy electron beams used in radiotherapy.

To ensure the effectiveness of radiation-therapy treatments, both in-phantom and in-patient reliable dose measurements are required. Thermoluminescence dosimeters are used commonly for both applications. Among the various available materials, the relatively new LiF:Mg,Cu,P phosphor is a suitable candidate for quality control of in vivo dosimetry in electron-beam therapy. The response behaviour of LiF:Mg,Cu,P chips to 6-21 MeV electron beams used in radiotherapy was studied. Batch homogeneity, dose linearity, sensitivity change after use, dose and dose-rate response, energy dependence and fading characteristics were investigated. The contribution from each factor to the overall uncertainty in dose measurement was evaluated. The results of this work show that the LiF:Mg,Cu,P chips are comparable to the commonly used LiF:Mg,Ti ones, and support their use for in vivo electron-beam dosimetry to an accuracy within +/- 10%.

Environmental gamma radiation measurements on the island of Pantelleria.

The population exposure to those living on the island of Pantelleria, Italy, was estimated by measuring the natural gamma background. Gamma spectra of natural rocks and measurements of absorbed dose in air were taken. A correlation was found between the mean gamma exposure rate and the mean values of natural radionuclide concentrations in the investigated rocks.