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An air flow transducer for controlling heated humidifiers used in neonatal artificial ventilation, suitable for in-line application in monopatient breathing circuits, is described here. The sensor is built with two nominally identical bipolar junction transistors, with different packages, as hot elements operated at a regulated constant voltage. The operation principle is based on the differential convective heat power exchanged with the fluid stream due to the different thermal conductivities of the transistors' packages. The underlying theory is described in mathematical terms and the theoretical model is validated with experimental data in the mass flow rate range from 4 to 215 mg s(-1). The nonlinear behavior allows sensitivities from -5 mV/(mg s(-1)) at flow rates in the range of 4-130 mg s(-1) to -2 mV/(mg s(-1)) at higher flow rates up to 215 mg s(-1). The linear range extends from 40 to 130 mg s(-1), with constant sensitivity equal to -5 mV/(mg s(-1)). The differential nature of the output allows to obtain repeatabilities in the order of 2% for fluid temperatures between 20 and 25 degrees C and of about 6% if the fluid temperature lies in the range of 15-35 degrees C. The relatively long time constant, in the order of 20+/-5 s, makes the sensor suitable for average flow rate measurements. Using the sensor's output as a control variable of a heated humidifier for artificial ventilation, the relative humidity of gases varies by only 20% in the flow rate range of the sensor (from 95% to 75%), whereas the same parameter shows a variation of about 40% (from 100% to 60%) with the same humidifier without flow control.

The toxicity of pertussis toxin is mediated by the ADP-ribosyltransferase activity of subunit S1. To understand the structure-function relationship of subunit S1 and guide the construction of nontoxic molecules suitable for vaccines, we constructed and expressed in Escherichia coli a series of amino-terminal and carboxyl-terminal deletion mutants as well as a number of molecules containing amino acid substitutions. The shortest peptide still retaining enzymatic activity contains amino acids 2-179. Within this region we identified three mutants in which amino acid substitutions abolish the enzymatic activity. Mutation of amino acids 8 and 9 or 50 and 53, located within the region of the S1 subunit of pertussis toxin homologous to cholera toxin, causes loss of enzymatic activity. Outside this homology region, substitution of Glu-129 with glycine or aspartic acid also eliminates the enzymatic activity of the S1 subunit. In this respect, Glu-129 resembles the glutamic acid that is crucial for the catalytic activity of diphtheria and Pseudomonas toxins. Once introduced into the Bordetella pertussis chromosome, the above mutations should lead to the synthesis of nontoxic pertussis toxin molecules suitable for vaccine production.

Eighty tissue biopsies from 73 women suspected of having papillomavirus (HPV) infection of the lower genital tract were examined by in situ hybridization with biotinylated DNA probes derived from the complete genomes of four HPV types (6, 11, 16, and 18) and restriction analysis of the extracted DNA on Southern blots. In a subset of 52 samples, the in situ test had a 90.4% sensitivity (47 of 52) in detecting the presence or absence of virus, whereas Southern blot analysis detected HPV with a sensitivity of 98.1% (51 of 52). For 51 samples, in which the viral type was determined by restriction analysis, comparison of the signals separately generated by the four probes after in situ hybridization allowed a correct identification of the infecting HPV type in 86.2% (44 of 51) of cases.

A theoretical analysis of the forces acting on the laryngoscope during the lifting of the epiglottis is carried out by applying the basic principles of statics. The static model of a laryngoscope equipped with a straight and a curved blade and the forces variation, as a function of the introduction angle and of tissue reaction application point, are described. The pharyngeal tissues and epiglottis pressure distribution on the blade is obtained, with a 1mm(2) resolution, by measurements performed in-vitro on a simulation mannequin, using straight and curved blades. The straight blade requires more effort than the curved one to obtain the same visualization of vocal cords, however forces exerted by using a laryngoscope with a curved blade do not vary linearly with the application point of tissue reaction. Average intensity of the tissue reaction has been found in the order of 32+/-11 N. Pressure distribution is maximally concentrated on the tip of curved blades (0.5 MPa on 5mm axial length), whereas it is more dispersed on straight blades (0.2 MPa on 10mm axial length). The inclination of the handle also influences the effort of the operator: for both blades, from 0 rad to 1.57 rad, the lifting force shows a total variation of about 13% of the top value, the transversal forces vary less than 6% of the top value.

The influence of some therapy-relevant parameters on Laser Induced Interstitial Thermotherapy (LITT) outcomes on pancreas is assessed. The aim is to execute a sensitivity analysis for an optimal treatment strategy on in vivo pancreas. A numerical model based on Bioheat Equation has been implemented to assess the influence of laser settings (power P and energy E), applicator radius (r(f)) and optical properties (effective attenuation coefficient, μ(eff)) on temperature (T) distribution. Effects on pancreas undergoing LITT have been evaluated with a twofold approach: 1) T rise and maximum T (T(max)) in tissue; 2) injured volumes (vaporized and coagulated ones). We consider parameters range in typical LITT values (P from 1.5 W to 6 W, E from 500 J to 1500 J, r(f) from 150 µm to 600 µm) and optical values reported in literature. Our analysis shows that, among others, P and μ(eff) are the principal influencing factors of thermal effects on pancreas undergoing LITT: P should be carefully chosen by operator to obtain the desired injured volumes, while the accurate measurement of tissue optical properties is crucial to carry out a safe and controlled thermal therapy on pancreas.

A procedure to assist the switching from volume controlled to pressure controlled ventilation assuring tidal volume is proposed. The method, based on a linear model of the dynamical behavior of the ventilatory system, identifies the main mechanical parameters of the system and is able to evaluate the pressure support value to set in pressure controlled ventilation in order to guarantee the necessary tidal volume to the patient. Extensive in vitro tests showed that the method reliably calculate the appropriate pressure support value leading to percent difference on tidal volume delivered equal to (1.3 /spl plusmn/ 0.6)%, i.e. less than 7 ml on a tidal volume of 500 ml. A low sensitivity to respiratory rate value was also observed. In consideration of the low error values obtained, it is possible to consider the proposed method as a valuable support to the physician during anesthesia delivery.

This study aims to develop and verify a theoretical model to reproduce the thermal response of pancreatic tissue undergone Laser Induced Interstitial Thermotherapy (LITT). The model provides the evaluation of: a) ablated volumes induced by thermal ablation; b) tissue response time to irradiation; and c) heat extinction time. Theoretical volume values were compared with ex vivo healthy tissue and in vivo healthy and neoplastic tissue volume values. The theoretical model takes into account the differences between healthy and neoplastic tissue due to blood perfusion. Mathematical model shows that ablated volume of ex vivo healthy tissue is greater than in vivo one after the same treatment. Moreover, ablated neoplastic in vivo tissue volume is greater than healthy in vivo one, because of tumour angiogenesis. Ablated volume values were compared with experimental data obtained by laser treatment of 30 ex vivo porcine pancreases. Experimental ablated volume values show a good agreement with theoretical values, with an estimated increase of 61% when power increases from 3 W to 6 W, versus 46% of experimental data, and an estimated increase of 14% from 6 W to 10 W, versus 21% of experimental values. LITT could be an alternative or a neo-adjuvant treatment to surgical resection for pancreas cancer removal, and the proposed model could be the basis to supervising the evolution of ablated volumes during tumor treatment.

The aim of present work is to test an optoelectronic system as diagnostic device to preliminary assess the efficacy of asymmetric respiratory rehabilitation. The respiratory rehabilitation efficacy, in terms of tidal volume variations, has been assessed for 14 patients undergone left or right superior lobectomy. Tidal volume variations of six torso compartments have been measured in pre-surgery, post-surgery and post-rehabilitation phases. Significant difference of total chest wall tidal volume has not been observed between the three phases. Tidal volume differences have been observed between paretic and healthy side. Significant tidal volume increase has been observed for non-operated side between pre-surgery and postrehabilitation phases during quiet breathing, mean tidal volume increases of about 32%. Measurement results indicate that respiratory rehabilitation is more effective on non-operated side which, in turn, compensates the operated one. The optoelectronic plethysmograph appears to be a suitable instrument for evaluation of respiratory rehabilitation in case of respiratory volumes asymmetry.

This paper describes an intensity-modulated fiber optic sensor for strain measurements. The sensing element is a polydimetilsiloxane (PDMS) micro-diffraction grating, 15 mm long, 2 mm thick, with channels 150 µm wide, spaced apart 200 µm. The working principle of the sensor can be summarized as follows: when the sensing element is strained perpendicularly to the grating plane, light passing through the grating undergoes a modulation caused by the phenomenon of diffraction. Since the grating is interposed between a laser source and a fiber optic, the coupled radiation intensity between these two optical elements can be considered as an indirect measure of strain. A static calibration of the measuring system has been performed, showing that the device, with measuring range of about 0.04, is capable to discriminate strain of 0.005 and it presents a sensitivity increase with strain in the whole range of measurements.

A non-invasive method to estimate cardiac output (CO) in mechanically ventilated patients, based on prolonged expiration, has been previously described. With the aim to assess its performances, we prospectively enrolled fifteen cardiac surgery patients, and compared the results obtained with the non-invasive method with the ones obtained using two invasive approaches based on thermodilution. The correlations between the prolonged expiration method with both the thermodilution-based ones show high values (ρ(2)0.77 and ρ(2)0.89). This encouraging agreement is also confirmed by the closeness between the measured values of CO: the mean differences considering all patients and the two reference invasive techniques are -0.8 % and -7.5 %. These values show the slight underestimation of CO by the proposed non-invasive method with respect to the gold standard. On the other hand the described method could represent a good compromise between accuracy and non-invasiveness, which fosters the implementation of a new monitoring tool suitable for a semi-continuous CO assessment.

Forces applied on oropharyngeal soft tissues by direct laryngoscopy may cause damage to the patients. The aim of this study was to measure the forces applied during the manoeuvres to achieve glottis visualization and tracheal intubation, comparing direct laryngoscopy and videolaryngoscopy in vivo.Thirty adult patients (ASA physical status 1 or 2, BMI between 18 and 30 kg/m2, no difficulty to intubate) were randomly and blindly assigned to one of two groups. Forces and pressure distribution applied during glottis visualization and intubation were measured using film pressure transducers, comparing Macintosh direct laryngoscope and GlideScope videolaryngoscope.Fifteen patients from each group, all with Cormack-Lehane grade 1 view, were analyzed. Forces applied during the intubation with the GlideScope were significantly lower than forces applied with the Macintosh (8+4 N vs. 40+14 N, respectively, P0.001). Considering the Macintosh laryngoscope, the minimal force applied for glottis visualization was significantly lower than the one applied for intubation (16+6 N vs. 40+14 N, respectively, P0.005). When using the Macintosh laryngoscope, forces were concentrated mostly on the tip, whereas with the GlideScope forces' concentration in a particular area was not observed.Our study shows that in patients with normal airways the GlideScope allows a view of glottis and permits a successful tracheal intubation applying lower force (significantly in intubation) as compared to the Macintosh laryngoscope. Also, the GlideScope probe distributes the forces more homogeneously to the tissue thus further reducing the potential for tissue damage.

A non invasive methodology to evaluate the viscoelastic behavior of the brachial artery by oscillometric repeated blood pressure measurements is proposed. The methodology is based on the quantitative evaluation of the curve representing the arterial cross sectional area vs. transmural pressure function: repeated loading and unloading of the brachial artery produces modifications of the shape of the curve which have been quantitatively evaluated. The procedure was tested on a homogeneous sample of subjects in order to evaluate its sensitivity to effect of the viscoelasticity. Two different viscoelastic behaviors and two significant parameters have been identified in the majority of the subjects whereas the method failed on 9% of the subjects examined. In addition two consecutive measurements have been found adequate to estimate the variations of the main parameters of the curve which allow an evaluation of the viscoelastic properties of the brachial artery.

Recently many different groups show that environmental temperature and relative humidity affects the outcomes of refractive surgery performed by excimer lasers in an unpredictable fashion. A theoretical model of the water vapor absorption at 193 nm wavelength is presented and discussed in order to quantitatively assess the influence of environmental parameters on the laser energy that actually reaches the corneal surface. Model simulations show that laser energy absorption (up to 7% of the available energy) occurs along the path of laser beam, into the existent space between the laser beam source and the patient's eye, and is caused by environmental temperature and relative humidity (respectively 35 degrees C and 95%). Our findings suggest that this energy loss reduces the ablation rate, producing a significant under-correction of the treated corneas. A cost effective device which keeps thermo hygrometric parameters constant along the laser beam path, is also provided.