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  • 1
    ISSN: 1432-1238
    Schlagwort(e): Mechanical ventilation ; Endotracheal tube ; Respiratory system resistance ; Airway resistance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Objective To investigate the role played by the endotracheal tube (ETT) in the correct evaluation of respiratory system mechanics with the end inflation occlusion method during constant flow controlled mechanical ventilation. Setting General ICU, university of Rome “La Sapienza”. Patients 12 consecutive patients undergoing controlled mechanical ventilation. Methods We compared the values of minimal resistance of the respiratory system (i.e. airway resistance) (RRS min) obtained: i) subtracting the theoretical value of ETT resistance from the difference between P max and P1, measured on airway pressure tracings obtained from the distal end of the ETT; ii) directly measuring airway pressure 2 cm below the ETT, thus automatically excluding ETT resistance from the data. Results The values of RRS min obtained by measuring airway pressure below the ETT were significantly lower than those obtained by measuring airway pressure at the distal end of the ETT and subtracting the theoretical ETT resistance (4.5±2.8 versus 2.5±1.6 cm H2O/l/s,p〈0.01). Conclusion When precise measurements of ohmic resistances are required in mechanically ventilated patients, the measurements must be obtained from airways pressure data obtained at tracheal level. The “in vivo” positioning of ETT significantly increases the airflow resistance of the ETT.
    Materialart: Digitale Medien
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  • 2
    ISSN: 1432-1238
    Schlagwort(e): Muscle relaxants ; Sedation ; Respiratory system mechanics ; Chest wall mechanics ; Mechanical ventilation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Objective To evaluate the separate effects of sedation and paralysis on chest wall and respiratory system mechanics of mechanically ventilated, critically ill patients.Setting: ICU of the University “La Sapienza” Hospital, Rome. Patients and participants 13 critically ill patients were enrolled in this study. All were affected by disease involving both lungs and chest wall mechanics (ARDS in 4 patients, closed chest trauma without flail chest in 4 patients, cardiogenic pulmonary oedema with fluidic overload in 5 patients). Measurements and results Respiratory system and chest wall mechanics were evaluated during constant flow controlled mechanical ventilation in basal conditions (i. e. with the patients under apnoic sedation) and after paralysis with pancuronium bromide. In details, we simultaneously recorded airflow, tracheal pressure, esophageal pressure and tidal volume; with the end-inspiratory and end-expiratory airway occlusion technique we could evaluate respiratory system and chest wall elastance and resistances. Lung mechanics was evaluated by subtracting chest wall from respiratory system data. All data obtained in basal conditions (with the patients sedated with thiopental or propofol) and after muscle paralysis were compared using the Student'st test for paired data. The administration of pancuronium bromide to sedated patients induced a complete muscle paralysis without producing significant modification both to the viscoelastic and to the resistive parameters of chest wall and respiratory system. Conclusions This study demonstrates the lack of additive effects of muscle paralysis in mechanically ventilated, sedated patients. Also in view of the possible side effects of muscle paralysis, our results question the usefulness of generalyzed administration of neuromuscular blocking drugs in mechanically ventilated patients.
    Materialart: Digitale Medien
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  • 3
    ISSN: 1432-1238
    Schlagwort(e): Mechanical ventilation ; Endotracheal tubes ; Obstruction ; Acute respiratory failure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Objective To evaluate the efficiency of a new device developed to remove obstructions from endotracheal tubes (ETT) in mechanically ventilated patients. Design Open study in mechanically ventilated sedated and paralyzed ICU patients. Setting General ICU and Laboratory of Respiratory Mechanics of the University of Rome “La Sapienza”. Patients 8 consecutive unselected mechanically ventilated, critically ill patients in which a partial obstruction of ETT was suspected on the basis of an increase of the peak inspiratory pressure (〉20%) plus the difficult introduction of a standard suction catheter. Interventions Obstructions to ETT were removed with an experimental “obstruction remover” (OR) Measurements “In vivo” ETT airflow resistance (0.25; 0.5; 0.75; 1l/s) was evaluated before and after use of the OR; the work of breathing necessary to overcome ETT resistance (WOBett) was also evaluated before and after OR use. Results The use of OR significantly reduced in all patients the ETT “in vivo” resistance (From 5.5±2.3 to 2.9±0.5 cmH2O/l/s at 0.25l/s,p〈0.05; from 9±2.4 to 3.8±0.8 cmH2O/l/s at 0.51l/s; from 12.2±3.5 to 5.7±1.2 cmH2O/l/s at 0.75l/s; from 16.9±6 to 9.3±3.8 cmH2O/l/s at 1l/s,p〈0.01 respectively). Also the WOBett was significantly reduced after use of the OR (from 0.66±0.19 to 0.34±0.08 J/l;p〈0.05) Conclusion This experimental device can be safely and successfully used to remove obstructions from the ETT lumen, without suspending mechanical ventilation, reducing the need for rapid ETT substitution in emergency and life-threatening situations.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1432-1238
    Schlagwort(e): Key words Acute respiratory failure ; Leukemia ; Noninvasive ventilation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Objective: To evaluate treatment with noninvasive ventilation (NIV) by nasal mask as an alternative to endotracheal intubation and conventional mechanical ventilation in patients with hematologic malignancies complicated by acute respiratory failure to decrease the risk of hemorrhagic complications and increase clinical tolerance. Design: Prospective clinical study. Setting: Hematologic and general intensive care unit (ICU), University of Rome “La Sapienza”. Patients: 16 consecutive patients with acute respiratory failure complicating hematologic malignancies. Interventions: NIV was delivered via nasal mask by means of a BiPAP ventilator (Respironics, USA); we evaluated the effects on blood gases, respiratory rate, and hemodynamics along with tolerance, complications, and outcome. Measurements and results: 15 of the 16 patients showed a significant improvement in blood gases and respiratory rate within the first 24 h of treatment. Arterial oxygen tension (PaO2), PaO2/FIO2 (fractional inspired oxygen) ratio, and arterial oxygen saturation significantly improved after 1 h of treatment (43 ± 10 vs 88 ± 37 mmHg; 87 ± 22 vs 175 ± 64; 81 ± 9 vs 95 ± 4 %, respectively) and continued to improve in the following 24 h (p 〈 0.01). Five patients died in the ICU following complications independent of the respiratory failure, while 11 were discharged from the ICU in stable condition after a mean stay of 4.3 ± 2.4 days and were discharged in good condition from the hospital. Conclusions: NIV by nasal mask proved to be feasible and appropriate for the treatment of respiratory failure in hematologic patients who were at high risk of intubation – related complications.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1432-1238
    Schlagwort(e): Key words Kyphoscoliosis ; Mechanical ventilation ; Respiratory mechanics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Objective: To evaluate respiratory mechanics in the early phase of decompensation in a group of seven patients with severe kyphoscoliosis (KS) (Cobb angle 〉 90 °) requiring mechanical ventilatory support. Design: Prospective clinical study with a control group. Setting: General intensive care unit at University of Rome “La Sapienza”. Patients: Seven consecutive patients affected by severe KS in the early phase of acute decompensation and a control group of six ASA (American Society of Anesthesiology) 1 subjects who were mechanically ventilated during minor surgery. Measurements and results: Respiratory mechanics were evaluated during constant flow-controlled mechanical ventilation at zero end-expiratory pressure with the end-inspiratory and end-expiratory occlusion technique. In five patients who showed increased ohmic resistance (RRSmin), we evaluated the possibility of reversing this increase with a charge dose of 6 mg/kg doxophylline i. v. In four KS patients, in whom a reliable esophageal pressure was confirmed by a positive occlusion test, we separated respiratory system data into lung and chest wall component. All KS patients showed reduced values of respiratory compliance (CRS) and increased respiratory resistance (RRS). The average basal values of CRS were 36 ± 10 vs 58 ± 8.5 cmH2O in control patients; RRSmax was 20 ± 3.1 vs. 4.5 ± 1.2 cmH2O/l per s; RRSmin 6.2 ± 1.2 vs. 2 ± 0.5 cmH2O/l per s: ΔRRS 14 ± 2.6 cmH2O vs 2.4 ± 0.7 cmH2O/l per s. All KS patients showed low values of intrinsic positive end-expiratory pressure (PEEPi) (1.8 ± 1.5 cmH2O). Separation of lung and chest-wall mechanics, performed only in four patients, showed a reduction in both lung (66.7 ± 7.2 ml/cmH2O) and chest wall values (84 ± 8.2 ml/cmH2O), while both RmaxL and RmaxCW were increased (16.6 ± 2 and 2.8 ± 0.4 cmH2O/l per s, respectively). Infusion of doxophylline did not significantly change respiratory mechanics when evaluated 15, 30, and 45 min after the infusion. Conclusions: During acute decompensation, both lung and chest-wall compliance are severely reduced in KS patients: conversely, and, contrary to that in patients with chronic obstructive pulmonary disease, increases in airway resistance and PEEPi seem to play only a secondary role.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Intensive care medicine 19 (1993), S. 305-305 
    ISSN: 1432-1238
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Radiation and environmental biophysics 32 (1993), S. 1-19 
    ISSN: 1432-2099
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Physik
    Notizen: Abstract A code for calculations of electron, ion and photon radiation action on tissue-equivalent matter (water vapor) by the Monte Carlo technique is presented. The new “fluctuation detector” method is efficient in evaluating of probability distributions and moments of absorbed energy and number of ionizations in small sites. Spatial and energy distributions of particles fluences and fluctuation characteristics of radiation action on spherical and thread-like sites of nanometer diameter are compared with various experimental and theoretical data and discussed. Non-equivalence of energy absorption and ionization events and consequences of that non-equivalence are numerically analysed. As an example of radiobiological application the yield of single- and double-strand breaks of DNA is calculated in a threshold model.
    Materialart: Digitale Medien
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  • 8
    ISSN: 1573-9228
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Russian physics journal 27 (1984), S. 725-729 
    ISSN: 1573-9228
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Closed representations are obtained for the density of the distribution and the moments of the absorbed energy in an isolated region of an irradiated absorber. It is shown that, for a broad class of problems (mainly microdosimetric), these quantities are expressed in terms of the differential flux densities of charged particles integrated over the angles and defined energy functions depending on the dimensions of the region and the material present there. The method of calculation deriving from the given representations is discussed.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Russian physics journal 31 (1988), S. 149-153 
    ISSN: 1573-9228
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The results of a calculation of the characteristics of fluctuations in the absorption of energy of electrons and gamma rays in small sensitive volumes of a material in electronic equilibrium are presented. The calculations were performed by the method developed in [1]. The efficiency and accuracy of the method are demonstrated by comparisons with the experimental results and direct numerical simulation. The experience gained in using the method is analyzed. The main numerical result of this work is a table of coefficients enabling the calculation of the probability of the absorption of energy and the first two moments of the energy absorbed in spherical regions with radii of 1, 2, 4, and 8 μm, starting only from the electronic spectrum in these regions, for water absorbers with arbitrary shape and arbitrary electronic or photonic sources with energies up to 1 MeV.
    Materialart: Digitale Medien
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