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Biomedical subjects

G Foti

Publications and source records attributed to G Foti.

At least 19 recordsLinked to original sources
PubMed2000

Effects of periodic lung recruitment maneuvers on gas exchange and respiratory mechanics in mechanically ventilated acute respiratory distress syndrome (ARDS) patients.

OBJECTIVE: We wished to investigate whether volume recruitment maneuvers (VRMs) could improve alveolar recruitment and oxygenation in acute respiratory distress syndrome (ARDS) patients, ventilated at relatively low positive end-expiratory pressure (PEEP). SETTING: General intensive care unit (ICU) located in a teaching hospital. PATIENTS: 15 PEEP responder ARDS patients undergoing continuous positive pressure ventilation (CPPV) with sedation and muscle paralysis. INTERVENTIONS: We identified a low (9.4 +/- 3 cmH2O) and a high (16.0 +/- 2 cmH2O) level of PEEP associated with target oxygenation values. Using a custom modified mechanical ventilator, we applied in random order three steps lasting 30 min: (1) CPPV at the low PEEP level (CPPV(LO)); (2) CPPV at the high PEEP level (CPPV(HI)); (3) CPPV at low PEEP with the superimposition of periodic VRMs (CPPV(VRM)). VRMs were performed twice a minute by increasing PEEP to the high level for two breaths. Each brace of two breaths was spaced 30 seconds from the preceding one. MEASUREMENTS AND RESULTS: We measured gas exchange, hemodynamics, respiratory mechanics, and the end expiratory lung volume (EELV). Compared to CPPV(LO), CPPV(VRM) resulted in higher PaO2 (117.9 +/- 40.6 vs 79.4 +/- 13.6 mmHg, P < 0.01) and EELV (1.50 +/- 0.62 vs 1.26 +/- 0.50 l, P < 0.05), and in lower venous admixture (Q(VA)/Q(T)) (0.42 +/- 0.07 vs 0.48 +/- 0.07, P < 0.01). During CPPV(HI), we observed significantly higher PaO2 (139.3 +/- 32.5 mmHg) and lower Q(VA)/Q(T) (0.37 +/- 0.08) compared to CPPV(LO) (P < 0.01) and to CPPV(VRM) (P < 0.05). CONCLUSIONS: VRMs can improve oxygenation and alveolar recruitment during CPPV at relatively low PEEP, but are relatively less effective than a continuous high PEEP level.

Adult↗
PubMed2000

Pressure support ventilation in patients with acute lung injury.

OBJECTIVES: To assess the success rate of pressure support ventilation (PSV) in acute lung injury patients undergoing continuous positive pressure ventilation (CPPV), to study physiologic changes after the transition from CPPV to PSV, and to investigate differences between patients who succeed and patients who fail PSV according to predetermined criteria. DESIGN: Observational study. SETTING: General intensive care unit in a teaching hospital. SUBJECTS: We studied 48 patients having acute lung injury, as defined by a PaO2/F(IO2) <300 mm Hg and the presence of bilateral infiltrates on chest radiograph, and ventilated with CPPV. We included patients with PaO2 >80 mm Hg, at positive end-expiratory pressure of <15 cm H2O and with F(IO2) up to 1.0. INTERVENTIONS: After enrollment, PSV was instituted and patients were strictly monitored during the following 48 hrs. Subjects who met any of the predefined PSV failure criteria during this period were returned to CPPV (Group F). PSV was continued in the remaining patients (Group S). MEASUREMENTS AND MAIN RESULTS: Gas exchange, respiratory mechanics, and hemodynamics measurements were collected before switching from CPPV to PSV and were repeated at 24 hrs after beginning PSV, or immediately before return to CPPV in Group F patients. The physiologic deadspace volume to tidal volume ratio (V(D)/V(T)) was obtained by the Enghoff's equation from the measurement of the mixed expired CO2 fraction. PSV resulted in a significant PaCO2 decrease (49.2+/-10.9 mm Hg to 44.4+/-7.2 mm Hg) and significant increases in minute volume (V(E))(9.0+/-2.3 L/min to 12.0+/-4.0 L/min) and arterial blood pH (7.405+/-0.054 to 7.435+/-0.064), with stable oxygenation and hemodynamics. In patients who were hypercapnic (PaCO2 >50 mm Hg) during CPPV, the V(E) increase was higher than in normocapnic patients. In the latter patients, PaCO2 and pH did not change significantly going from CPPV to PSV. A total of 38 patients (79%) were allocated to Group S and the remaining 10 patients were included in Group F. In Group S, positive endexpiratory pressure of 9.4+/-2.9 cm H2O (range, 3-14 cm H2O) and a PSV level of 14.9+/-3.8 cm H2O (range, 9-22 cm H2O) were applied. In Group F, positive end-expiratory pressure of 8.9+/-3.1 cm H2O (range, 5-15 cm H2O) and a PSV level of 21.6+/-4.6 cm H2O (range, 16-31 cm H2O) were adopted. Compared with Group S, Group F had a longer duration of intubation (20.2+/-19.2 days vs. 9.2+/-13.5 days), a lower static compliance of the respiratory system (30.4+/-16.5 mL/cm H2O vs. 41.7+/-15.0 mL/cm H2O), and a higher V(D)/V(T) (0.70+/-0.09 vs. 0.52+/-0.10), but similar oxygenation and positive end-expiratory pressure. V(E) was higher in Group F during both CPPV and PSV. CONCLUSIONS: In a relatively high proportion of the investigated patients, PSV was successful. The institution of PSV led to no major changes in oxygenation or in hemodynamics. PSV was associated with increases in V(E) and respiratory frequency. In patients who had been hypercapnic during CPPV, PaCO2 decreased despite a compensated pH. Compared with PSV success patients, patients who failed PSV appeared to be sicker, as shown by the higher duration of respiratory support, increased ventilatory needs, and decreased respiratory system compliance, despite similar arterial oxygenation and positive end-expiratory pressure.

Acid-Base Equilibrium↗
PubMed1998

Effects of continuous negative extrathoracic pressure versus positive end-expiratory pressure in acute lung injury patients.

OBJECTIVE: To compare the effects of continuous negative extrathoracic pressure (CNEP) and positive end-expiratory pressure (PEEP) at the same level of transpulmonary pressure. DESIGN: Prospective analysis. SETTING: Medical intensive care unit of a university hospital. PATIENTS: Nine consecutive acute lung injury patients. Patients with cardiac failure and patients with chronic lung disease were excluded from the investigation. INTERVENTIONS: The patients were sedated and paralyzed while receiving mechanical ventilation and were studied in three different conditions: a) using a PEEP of 0 cm H2O (zero end-expiratory pressure); b) using a PEEP of 15 cm H2O; c) using CNEP. CNEP was applied to the thorax and the upper abdomen and its level was chosen to obtain a transpulmonary pressure similar to the one observed at a PEEP of 15 cm H2O. All patients had an arterial catheter, a pulmonary artery catheter, and a thermistor-tip fiberoptic catheter for thermo-dye-dilution in the femoral artery. These catheters were connected to an integrated monitoring system. We also placed an esophageal catheter in each patient to detect esophageal pressure. MEASUREMENTS AND MAIN RESULTS: For each step, we assessed the hemodynamic variations by measuring intravascular pressures (via a pulmonary artery catheter), transmural pressures (computed by subtracting esophageal pressure from intravascular pressure), and blood volumes (derived from the technique of double indicator). The application of CNEP of -20+/-0.7 cm H2O produced a venous admixture and PaO2/FO2 improvement similar to that obtained with a PEEP of 15 cm H2O. This procedure is associated with a higher cardiac index (5.5+/-1.5 vs. 4.6+/-1.2 L/min/m2; p < .05) coupled with lower central venous pressure, pulmonary artery occlusion pressure, and higher transmural pressures and blood volume parameters. CONCLUSIONS: In acute lung injury patients, a CNEP of -20 cm H2O has the capability to obtain transpulmonary pressure and lung function improvement similar to a PEEP of 15 cm H2O. CNEP differs from the positive pressure by increasing the venous return and the preload of the heart, and has no negative effects on cardiac performance.

APACHE↗
PubMed1997

End-inspiratory airway occlusion: a method to assess the pressure developed by inspiratory muscles in patients with acute lung injury undergoing pressure support.

We evaluated the end-inspiratory occlusion maneuver as a means to estimate the inspiratory effort during pressure support ventilation (PS). In nine nonobstructed acute lung injury (ALI) patients, we applied four levels of PS (0, 5, 10, 15 cm H2O) to modify the inspiratory effort. End inspiratory occlusions (2 to 3 s) were performed at the end of each experimental period by pushing the inspiratory hold button of the ventilator (Servo 900 C; Siemens, Berlin, Germany). We took the difference between the end-inspiratory occlusion plateau pressure and the airway pressure before the occlusion (PEEP + PS) as an estimate of the inspiratory effort and called it PMI (Pmusc,index). From the esophageal pressure tracing we obtained a reference measurement of the pressure developed by the inspiratory muscles at end inspiration (Pmusc,ei) and of the pressure-time product per breath (PTP/b) and per minute (PTP/min). In each patient, PMI was correlated with Pmusc,ei (p < 0.01) and PTP/b (p < 0.01). A PMI threshold of 6 cm H2O detected PTP/min < 125 cm H2O s/min with a sensitivity of 0.89 and a specificity of 0.89. We conclude that PMI is a good estimate of the pressure developed by the inspiratory muscles in ALI patients and may be used to titrate PS level. The major advantage of PMI is that it can be obtained from the ventilator display without any additional equipment.

Acute Disease↗
PubMed1997

Lung and chest wall mechanics in normal anaesthetized subjects and in patients with COPD at different PEEP levels.

In order to assess the relative contribution of the lung and the chest wall to the derangements of respiratory mechanics in chronic obstructive pulmonary disease (COPD) patients with acute ventilatory failure (AVF), we studied eight COPD patients undergoing controlled mechanical ventilation for AVF and nine normal subjects anaesthetized for surgery as a control group. With the use of the interrupter technique together with the oesophageal balloon technique we measured: static lung and chest wall elastances (E[st,L] and E[st,w], respectively), maximum (R[L,max]), minimum (R[L,min]) and additional (deltaR[L]) lung resistances, additional chest wall resistance (deltaRw) and, in the COPD group, total intrinsic positive end-expiratory pressure (PEEPtot). Measurements were repeated at 0, 5, 10 and 15 cmH2O of applied positive end-expiratory pressure (PEEP). We found that, in the COPD group: 1) both E(st,w) and deltaRw were higher than in the normal group; 2) R(L,max) was markedly increased due to an increase of both R(L,min) and deltaRL; 3) even low levels of PEEP increased PEEPtot; 4) PEEP did not reduce elastance or total resistance of either the lung or the chest wall. We conclude that chest wall mechanics are abnormal in chronic obstructive pulmonary disease patients with acute ventilatory failure undergoing controlled mechanical ventilation and that positive end-expiratory pressure does not seem to be effective in reducing either elastance or resistance of the lung or chest wall.

Anesthesia, General↗
PubMed1997

Doppler-broadening of positron annihilation in a biological environment.

The aim of this study was to investigate the Doppler effect of the 511 keV gamma peak from positron annihilation in biological matter. The broadening of the annihilation peak is due to positron annihilation with electrons that have high momentum. In aqueous solutions annihilation depends on the temperature and it is linked positronium formation. Measurements in vivo, on human brain, were taken during the diagnosis of positron emission tomography (PET) on healthy patients by injecting them with the beta emitter of short lifetime 18F. The Doppler-broadening in biological tissues rich in water content decreased significantly compared to biological solutions and water.

Body Water↗
PubMed1997

[A peculiar form of anemia in patients operated on for cancer of the oral cavity].

The authors related about a peculiar form of anemia found in some patients operated on oral cancer; these patients had an almost normal hematic situation before their operation. 63 patients, operated in the course of a year for oral cancer, have been studied by the authors; they have found in 14 cases (22.2%) a light anemia which regressed after a self blood transfusion, during the first week after the operation; in other 8 cases (12.7%) the anemia, which was more serious, persisted beyond the 7th day after the operation. Those 8 patients, suffering from more serious and persistent anemia, were treated from 7th to 21st day after the operation with iron, vitamin B12 and folic acid without any improvement. The hematic situation improved about 10 days after the end of treatment, probably as a result of spontaneous renewal of medullar haemopoietic activity. This anemia, is characterized by normochromia, normocytosis, reduced response of reticulocytes, sideropenia and hyperferritinaemia. The authors think that the pathogenesis of anemia after operation in neoplastic patients is caused by medullary insufficiency existing before the operation, connected with reduced erythropoietin production and emphasized by an operation that sometimes cause bleeding. Consequently the authors hypothesis the use of erythropoietin in the therapy of most severe anemia in neoplastic operated patients.

Anemia↗
PubMed1996

Skeletal myogenesis: the preferred pathway of chick embryo epiblast cells in vitro.

The epiblast layer of the chick embryo gives rise to all embryonic tissues. In vitro analyses were carried out to determine whether epiblast cells could form skeletal muscle prior to entry into the primitive streak. Epiblasts were separated from the mesoderm, hypoblast, and primitive streak, dissociated to produce a single cell suspension, and plated at high density. Myogenesis began on the first day in culture, and by the fifth day most cells had differentiated into skeletal muscle. Some cells differentiated without replicating. MyoD messenger RNA was present in epiblast tissue and translated in practically all cells in culture. Cells from regions of the epiblast which do not form muscle later in the embryo did so in vitro. Epiblasts cultured for 2 days as an intact epithelium, or in the presence of the mesoderm and hypoblast, did not undergo myogenesis. These findings demonstrate that myogenic potential is wide-spread within the primitive streak stage epiblast, and that muscle differentiation, which occurs relatively autonomously in culture, can be prevented by cell and tissue interactions.

Animals↗
PubMed1996

Effects of carbon dioxide insufflation for laparoscopic cholecystectomy on the respiratory system.

The changes occurring in total respiratory system, lung and chest wall mechanics, lung volume and gas-exchange during abdominal insufflation with carbon dioxide for laparoscopic cholecystectomy were studied. Using the technique of rapid airway occlusion during constant flow inflation together with an oesophageal balloon, we computed compliance and maximum resistance of the respiratory system, subsequently apportioning it into its lung and chest wall components. Maximum resistance of the respiratory system was further divided into airway resistance and the viscoelastic properties of the lung and the chest wall. In 10 patients (group 1), we measured respiratory system, lung and chest wall mechanics (compliance and resistance), functional residual capacity, end-tidal carbon dioxide tension and oxygen saturation. In addition, arterial blood gas analysis and end-tidal carbon dioxide tension were measured in a second group of 10 patients (group 2). Measurements, in both groups, were obtained in the reverse Trendelenburg position, at 15 min after the induction of anaesthesia, 5 min and 45 min after abdominal insufflation and at 15 min after abdominal deflation. Tidal volume, respiratory rate, inspiratory flow and the fraction of inspired oxygen were similar in both groups and maintained constant during the procedure. We found that abdominal carbon dioxide insufflation caused: a reduction in compliance of the respiratory system (both lung and chest wall components) and of functional residual capacity; a marked increase in the maximum resistance of the respiratory system (mainly due to increases in the viscoelastic properties of the lung and chest wall); no change in oxygenation, but an increase in the end-tidal carbon dioxide tension (which was correlated closely with the arterial carbon dioxide tension). These changes were not affected by the duration of anaesthesia.

Abdomen↗
PubMed1996

Positive end-expiratory pressure prevents the loss of respiratory compliance during low tidal volume ventilation in acute lung injury patients.

STUDY OBJECTIVE: To study the effect of positive end-expiratory pressure (PEEP) on the decay of respiratory system compliance (Cpl,rs) due to low tidal volume (VT) ventilation in acute lung injury (ALI) patients. SETTING: General ICU in a university hospital. PARTICIPANTS: Eight ALI patients with a lung injury score greater than 2.5. INTERVENTION: Pressure-controlled ventilation (PCV) and volume-controlled ventilation (VCV), with an average VT of 8.5 +/- 0.4 mL/kg, were applied at three levels of PEEP (5, 10, and 15 cm H2O). Before each PCV and VCV period, lung volume history was standardized by manual hyperinflation maneuvers. MEASUREMENTS: We measured Cpl,rs at time 0 (start), 10, 20, and 30 (end) min from the beginning of each PCV and VCV period. Gas exchange and hemodynamic data were collected at end. RESULTS: At PEEP 5 and 10 cm H2O, we observed a progressive Cpl,rs decay with both PCV and VCV modes. At PEEP 5 cm H2O, we detected a higher Cpl,rs decrease during PCV, due to a higher Cpl,rs at start, compared with VCV. At PEEP 15 cm H2O, Cpl,rs did not decrease significantly. Cpl,rs values measured at end as well as oxygenation and hemodynamic data did not differ between PCV and VCV. At PEEP 15 cm H2O, PCV provided lower PaCO2 than VCV. CONCLUSIONS: A PEEP of at least 15 cm H2O was needed to prevent Cpl,rs decay. The progressive Cpl,rs loss we observed at lower PEEP probably reflects alveolar instability.

Adult↗
PubMed1995

Pressure control ventilation and minitracheotomy in treating severe flail chest trauma.

OBJECTIVE: To evaluate pressure control ventilation (PCV) delivered through a minitracheotomy in treating severe flail chest trauma. DESIGN: Case report. SETTING: Intensive care unit of a trauma center. PATIENT: A 34-year-old woman affected by flail chest trauma and acute respiratory failure, who was initially treated with tracheal intubation to obtain internal pneumatic stabilization. The patient failed extubation and noninvasive mask treatment (pressure support ventilation plus PEEP) due to poor chestwall mechanics. INTERVENTIONS: Minitracheotomy was performed and ventilation was achieved with high levels of inspiratory pressure (PCV or assisted PCV) to overcome the resistance of the cannula (Mini-Trach II, Portex, ID 4 mm). Esophageal and carinal pressures were monitored. Ventilatory treatment was always performed with the full cooperation of the patient; the patient's glottic function was always intact. The patient was successfully treated with pressure control ventilation delivered through the Mini-Trach. After 7 days of PCV, the patient was switched to assisted PCV. On the 20th day after admission, she was weaned from mechanical ventilation. CONCLUSIONS: We conclude that a suitable gas exchange and pneumatic stabilization in a flail chest condition can be achieved using minitracheostomic ventilation. At the same time, this treatment could reduce some side effects of traditional tracheal intubation.

Adult↗
PubMed1995

Alterations of lung and chest wall mechanics in patients with acute lung injury: effects of positive end-expiratory pressure.

In 16 mechanically ventilated patients with acute lung injury (ALI) (eight patients with moderate ALI [moderate group], eight patients with severe ALI [adult respiratory distress syndrome, ARDS group]) and in eight normal anesthetized-paralyzed subjects (control group), we partitioned the total respiratory system mechanics into the lung (L) and chest wall (w) mechanics using the esophageal balloon technique together with the airway occlusion technique during constant flow inflation. We measured lung elastance (Est,L), chest wall elastance (Est,w), and total lung (Rmax, L) and chest wall (Rmax,w) resistance. Rmax,L includes airway (Rmin,L) and "additional" lung resistance (DR,L). DR,L represents the "additional" component due to the viscoelastic phenomena of the lung tissues and time-constant inequalities (pendelluft). Measurements were repeated at 0, 5, and 10 cm H2O of positive end-expiratory pressure (PEEP) in the control group and at 0, 5, 10, and 15 cm H2O PEEP in patients with ALI. The end-expiratory lung volume (EELV) was measured at each level of PEEP. Specific total lung (sRmax,L), airway (sRmin,L), and "additional" lung (sDR,L) resistances were obtained as Rmax,L x EELV, Rmin,L x EELV, and DR,L x EELV, respectively. At PEEP 0 cm H2O, we found that both Est,L (23.7 +/- 5.5 and 13.8 +/- 3.3 versus 9.3 +/- 1.7 cm H2O/L; p < 0.01) and Est,w (13.2 +/- 5.4 and 9.9 +/- 2.1 versus 5.6 +/- 2.3 cm H2O/L; p < 0.01) were markedly increased in patients with ARDS and moderate ALI compared with control subjects, with a significant (p < 0.01) effect of the severity of the disease on Est,L (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗
PubMed1994

[Aortic valve replacement in old age. The results and follow-up echo-Doppler study of the prostheses].

BACKGROUND: To analyze the results of aortic valve replacement in elderly patients and to evaluate the hemodynamic performance of valvular prostheses, we have retrospectively studied the patients 70 years of age or older, who consecutively underwent aortic valve replacement in our Center. METHODS: From January 1988 to December 1992, a series of 112 patients aged 70 to 88 years (mean 74.8 +/- 3.8 years) underwent aortic valve replacement; 49.1% of patients were male; aortic valvular lesion was: stenosis in 65.2%, insufficiency in 9.8% and mixed stenosis and insufficiency in 25.0%. In 73.2% isolated valve disease was present; in 25.0% coronary artery disease was associated. Preoperatively 58.9% were in New York Heart Association class III, and 29.5% were in class IV. Concomitant extracardiac diseases were present in 73.2%. The types of valve prostheses employed were: mechanical tilting disc (28 cases), mechanical bileaflet (40 cases), bioprosthesis (44 cases). A significantly favourable relationship between body surface area and size of prostheses was evident. RESULTS: Overall hospital mortality was 8.9% (5.4% for elective isolated aortic valve replacement) with significant difference (p = 0.006) related to criteria for surgical indication (elective 6.4%, urgent 10.0%, emergency 37.5%). Valvular lesion, age, sex, associated coronary artery bypass surgery, the values of peak and mean aortic valve gradient, the relative wall thickness and the presence of extracardiac disease have not been identified as risk factors for hospital mortality. The mean follow-up of the 102 discharged patients is 27.1 +/- 16.5 months (range 2 to 64 months). Eight late deaths (7.8%) occurred; the overall actuarial freedom from all deaths (excluding hospital mortality) was 95.6 +/- 2.2% at 1 year and 88.6 +/- 4.0% at 3 and 5 years. Five non fatal valve related complications occurred: hemorrhage in 4 cases (1.8% pt/yr) and hemolysis in 1 case (0.4% pt/yr). Ninety-seven percent of patients were found to be in NYHA functional class I or II. Comparative echocardiographic evaluation of the prostheses showed significant differences in mean gradient: regarding 21 mm size lower in bileaflet than in tilting disc and regarding 23 mm size lower in bileaflet than in tilting disc or bioprostheses. CONCLUSIONS: Aortic valve replacement has proved to be safe and effective in the elderly population and is considered the procedure of choice for aortic valve disease. Although we consider mandatory to choose the valve substitute matching different physiopathological and psychological attitudes of individual patient, mechanical prostheses and particularly bileaflet type for size < or = 21 mm should be preferred.

Aged↗
PubMed1993

Effects of short-term oxygenation changes on acute lung injury patients undergoing pressure support ventilation.

We investigated the effects of short-term oxygenation changes upon the neuromuscular respiratory drive (airway occlusion pressure [P0.1]), minute ventilation (VE), and respiratory rate (RR) in 12 acute lung injury patients undergoing pressure support ventilation. We ventilated the patients first at a high level (H1) of oxygenation, then at intermediate (I), at low, and again at the high (H2) level. The H1 and H2 periods showed no differences. In the H1, I, and L periods, PaO2 was 158 +/- 68, 75 +/- 12, and 55 +/- 6 mm Hg, respectively. Decreasing oxygenation caused very significant increases in VE, RR, and P0.1. Differences in RR, VE, and rapid shallow breathing index were significant at step H1 versus I. Changes in P0.1 appeared to be higher when the H1 value was higher than normal. An arterial oxygenation target higher than the generally accepted 60 mm Hg level may decrease both RR and VE.

Humans↗