Biomedical subjects

A Peratoner

Publications and source records attributed to A Peratoner.

9 recordsLinked to original sources

PubMed2006

Mechanical loads modulate tidal volume and lung washout during high-frequency percussive ventilation.

High-frequency percussive ventilation (HFPV) has been proved useful in patients with acute respiratory distress syndrome. However, its physiological mechanisms are still poorly understood. The aim of this work is to evaluate the effects of mechanical loading on the tidal volume and lung washout during HFPV. For this purpose a single-compartment mechanical lung simulator, which allows the combination of three elastic and four resistive loads (E and R, respectively), underwent HFPV with constant ventilator settings. With increasing E and decreasing R the tidal volume/cumulative oscillated gas volume ratio fell, while the duration of end-inspiratory plateau/inspiratory time increased. Indeed, an inverse linear relationship was found between these two ratios. Peak and mean pressure in the model decreased linearly with increasing pulsatile volume, the latter to a lesser extent. In conclusion, elastic or resistive loading modulates the mechanical characteristics of the HFPV device but in such a way that washout volume and time allowed for diffusive ventilation vary agonistically.

Airway Resistance↗

PubMed2005

Sepsis and organ dysfunction: an ongoing challenge.

In recent years the problem of infection has become increasingly significant, especially in intensive care hospital wards such as Intensive Care Units (ICU), emergency medicine, surgery and critically ill patient care departments. Sepsis is a complex, multifactorial syndrome that can develop into conditions of different severity, described as severe sepsis or septic shock. In these conditions the triggering event may coincide with the functional impairment of one or more vital organs or systems, thus leading to poorer prognosis in patients with overt signs of sepsis or systemic inflammation syndromes. The available data are quite alarming, as most prevention and treatment is performed empirically and requires considerable human and technological resources. Clinical signs are often misleading and, in some circumstances, it may be difficult or even impossible to identify the source of the infection which might otherwise be removed relatively simply, using proper antimicrobial treatment or a less invasive surgical removal of the area from which the infection originates based on needle-guided radiology. In addition, the complex pathophysiological mechanisms involved can be an obstacle to gaining a full understanding of the various biohumoral interactions or mediators action mechanisms. It may not be easy to enroll patients belonging to homogeneous groups in terms of age, underlining disease, immune profile or genetic predisposition, although the use of specific severity indexes has proved helpful also to establish the prognosis. Although the interpretation of generalised inflammation as a warning sign also in the absence of clear signs of infection or a state of overt inflammation has to rely largely on simple intuition, it has helped to drive experimental and clinical research work towards the investigation of interaction between different factors such as infection and sepsis, or inflammation and coagulation. An additional useful tool is the possibility of modulating the endothelial response which may support the process of disseminated thrombosis typical of sepsis evolution. In this context the improvement of standards of care can shed light on the efficacy of different treatments.

Blood Coagulation↗

PubMed2005

Systemic and organ dysfunction response during infusion of recombinant human activated protein C (rhAPC) in severe sepsis and septic shock.

AIM: The aim of this study was the assessment of the efficacy of recombinant human activated protein C (rhAPC) in septic patients. METHODS: A continuous observational prospective study on ICU patients with severe sepsis and septic shock was carried out. Applying the inclusion criteria of a national trial on the use of rhAPC, 15 patients (12 males and 3 females) were enrolled, mean age was 65.9 (SD 9.6), APACHE II score was > or =25. The following variables were assessed on 7 time-points (T1-T7): overall SOFA score; organ-specific SOFA score; APACHE II score; PCR, APTT, INR, fibrinogen, platelet count. Wilcoxon's statistical test and Spearman's correlation test (rho coefficient) between the SOFA and APACHE II scores were used. Test results with a P value below 0.05 were deemed significant. RESULTS: A significant correlation was identified between the APACHE II and SOFA scores. No significant change was found in Friedman's test and the respiratory, haematological and hepatic SOFA score, whereas cardiovascular, renal and neurological SOFA scores showed a significant trend between the ranks at the 7 time-points (chi2=14; df=6; P=0.029). During rhAPC treatment Friedman's test showed significant changes of PCR values over the 7 time-points (chi2=19.2; df=6; P=0.02). Wilcoxon's test indicated a significant decrease in the values recorded during the T2-T6 period. On day 28, 12 of the 15 patients originally enrolled were still alive. Mortality rate was therefore 20% (CI 95%). CONCLUSIONS: RhAPC is the first biological agent approved for the treatment of severe sepsis and septic shock. Our experience is confined to patients with severe sepsis and septic shock, and some severity indexes showed a modulation of the inflammatory processes and haemostatic balance, 2 factors which play a key role in the evolution of sepsis and organ dysfunction.

APACHE↗

PubMed2004

Effects of mechanical load on flow, volume and pressure delivered by high-frequency percussive ventilation.

High-frequency percussive ventilation (HFPV) has proved its unique efficacy in the treatment of acute respiratory distress, when conventional mechanical ventilation (CMV) has demonstrated a limited response. We analysed flow (V(dot)), volume (V) and airway pressure (Paw) during ventilation of a single-compartment mechanical lung simulator, in which resistance (R) and elastance (E) values were modified, while maintaining the selected ventilatory settings of the HFPV device. These signals reveal the physical effect of the imposed loads on the output of the ventilatory device, secondary to constant (millisecond by millisecond) alterations in pulmonary dynamics. V(dot), V and Paw values depended fundamentally on the value of R, but their shapes were modified by R and E. Although peak Paw increased 70.3% in relation to control value, mean Paw augmented solely 36.5% under the same circumstances (maximum of 9.4 cm H2O). Finally, a mechanism for washing gas out of the lung was suggested.

Airway Resistance↗

PubMed2004

Effects of propofol on respiratory mechanic and lung histology in normal rats.

BACKGROUND: Propofol is able to reduce airway resistance in lungs with previous airway constriction. The aim of this study was to evaluate the effects of propofol on respiratory mechanics in normal rats and to correlate these parameters with lung histology, to define the sites of action of propofol. METHODS: Sixteen Wistar rats were divided into two groups of eight animals. Rats were sedated (diazepam) and anaesthetized with pentobarbital sodium (C) or propofol (P), and paralysed. Respiratory system, lung, and chest wall resistive, elastic, and viscoelastic/inhomogeneous pressures were computed using the end-inflation occlusion method. RESULTS: Lung resistive pressure was smaller in group P (0.29 kPa (0.05)) than group C (0.37 kPa (0.04)) (P=0.007). The internal diameter of the central airways was greater in group P than C (P=0.01). CONCLUSION: Propofol acts at the airway level decreasing respiratory system and lung impedances as a result of central airway dilation.

Airway Resistance↗

PubMed2000

Bedside assessment of respiratory viscoelastic properties in ventilated patients.

Viscoelasticity represents an important component of respiratory mechanics, being responsible, in some cases, for most of the pressure dissipated during breathing. Hitherto the methods available for determining the viscoelastic properties have been simplified, but are still time-demanding and depend on a great deal of calculation. In this study, a simple means of determining respiratory viscoelastic properties during mechanical ventilation was introduced. The viscoelastic constants of the respiratory system, modelled as a Maxwell body, were studied in 17 normal subjects and seven patients with acute lung injury (ALI) using two end-inspiratory occlusions; one with a short inspiratory time (tI) to determine the elastic component of viscoelasticity and the other with a long tI to assess the resistive component of viscoelasticity. The results were reproducible and similar to those provided by the previously described multiple-breath method (MB). The mean+/-SD viscoelastic resistance was 5.31+/-1.50 cm H2O x L(-1) x s with the proposed method and 5.71+/-1.87 cm H2O x L(-1) x s with the MB method in normal subjects, and 8.93+/-2.82 cm H2O x L(-1) x s and 10.36+/-3.13 cm H2O x L(-1), respectively in ALI patients. The mean+/-SD viscoelastic elastance was 3.92+/-0.84 cm H2O x L(-1) and 4.94+/-1.01 cm H2O x L(-1) in normal subjects and 7.08+/-2.01 cm H2O x L(-1) and 8.21+/-1.16 cm H2O x L(-1) in ALI patients, respectively. The mean+/-SD viscoelastic time constant was 1.36+/-0.24 s and 1.17+/-0.34 s in normal subjects and 1.26+/-0.35 s and 1.24+/-0.23 in ALI patients, respectively. The method was easy to perform and applicable at the bedside in clinical routine.

Adult↗

PubMed1998

Single-breath method for assessing the viscoelastic properties of the respiratory system.

In order to explain the time dependency of resistance and elastance of the respiratory system, a linear viscoelastic model (Maxwell body) has been proposed. In this model the maximal viscoelastic pressure (Pvisc.max) developed within the tissues of the lung and chest wall at the end of a constant-flow (V') inflation of a given time (tI) is given by: Pvisc,max = R2V'(1-e(-tI/tau2), where R2 and tau2 are, respectively, the resistance and time constant of the Maxwell body. After rapid airway occlusion at t1, tracheal pressure (Ptr) decays according to the following function: Ptr(t) = Pvisc(t) + Prs,st = Pvisc,max(etocc/tau2)+ Prs,st, where tocc/is time after occlusion and Prs,st is static re-coil pressure of the respiratory system. By fitting Ptr after occlusion to this equation, tau2 and Pvisc,max are obtained. Using these values, together with the V' and tI pertaining to the constant-flow inflation preceding the occlusion, R2 can be calculated from the former equation. Thus, from a single breath, the constants tau2, R2 and E2 (R2/tau2) can be obtained. This method was used in 10 normal anaesthetized, paralysed, mechanically ventilated subjects and six patients with acute lung injury. The results were reproducible in repeated tests and similar to those obtained from the same subjects and patients with the time-consuming isoflow, multiple-breath method described previously.

Adult↗

PubMed1997

Near fatal asthma and psychopathological characteristics: a group-control study.

Psychological factors may play a role in asthma. In particular, emotional upsets have been correlated with fatal asthma attacks, and an abnormal personality attitude is considered to be a risk factor in fatal asthma. Moreover, some authors have recently reported favourable asthma outcome in patients with severe asthma and psychiatric abnormalities, when psychoactive treatment was initiated. On the understanding that people with fatal and "near fatal asthma" (NFA) are components of the same subset of the asthmatic population, we undertook a study aimed at assessing the importance of personality and psychiatric factors in asthma mortality. Between June 1991 and December 1993, a sample of 17 patients with asthma who had experienced one or more near fatal asthma attacks (respiratory arrest, or need for respiratory assistance, or altered conscious state, or arterial carbon dioxide tension (Pa,CO2) > 6.7 kPa (50 mmHg)), and 17 control patients with asthma who had never experienced such an attack (control group) were enrolled. All patients underwent: 1) an interview concerning their personal and family psychiatric history; 2) a psychodiagnostic investigation by a battery of four of the most widely used psychiatric tools: Hamilton scales for anxiety and depression; Zung scales for anxiety and depression; and Minnesota Multiphasic Personality Inventory. No statistical difference was found in psychodiagnostic tests between study and control groups. The psychiatric history was similar in the two groups. Our results suggest that personality characteristics and psychiatric history are not related to asthma outcome, and that the psychiatric approach is not expected to be useful in preventing mortality in asthma.

Adult↗

PubMed1992

Long-term treatment with sodium cromoglycate, nedocromil sodium and beclomethasone dipropionate reduces bronchial hyperresponsiveness in asthmatic subjects.

165 patients (106 males, 59 females) entered an open group comparative study of a 12-week test treatment on bronchial hyperresponsiveness (BHR) determined by methacholine challenge. Patients were randomly allocated to receive nedocromil sodium (4 mg q.i.d.), sodium cromoglycate (10 micrograms q.i.d.) and beclomethasone dipropionate (500 micrograms t.i.d.). At the end of the study, an 2.25-fold increase of the PD20FEV1 was noted in all the treated patients. No significant difference was noted among the treatments.

Adult↗