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Biomedical subjects

L Brochard

Publications and source records attributed to L Brochard.

At least 73 records · Page 4Linked to original sources
PubMed1998

Tidal volume reduction for prevention of ventilator-induced lung injury in acute respiratory distress syndrome. The Multicenter Trail Group on Tidal Volume reduction in ARDS.

Because animal studies have demonstrated that mechanical ventilation at high volume and pressure can be deleterious to the lungs, limitation of airway pressure, allowing hypercapnia if necessary, is already used for ventilation of acute respiratory distress syndrome (ARDS). Whether a systematic and more drastic reduction is necessary is debatable. A multicenter randomized study was undertaken to compare a strategy aimed at limiting the end-inspiratory plateau pressure to 25 cm H2O, using tidal volume (VT) below 10 ml/kg of body weight, versus a more conventional ventilatory approach (with regard to current practice) using VT at 10 ml/kg or above and close to normal PaCO2. Both arms used a similar level of positive end-expiratory pressure. A total of 116 patients with ARDS and no organ failure other than the lung were enrolled over 32 mo in 25 centers. The two groups were similar at inclusion. Patients in the two arms were ventilated with different VT (7.1 +/- 1.3 versus 10.3 +/- 1.7 ml/kg at Day 1, p < 0.001) and plateau pressures (25.7 +/- 5. 0 versus 31.7 +/- 6.6 cm H2O at Day 1, p < 0.001), resulting in different PaCO2 (59.5 +/- 15.0 versus 41.3 +/- 7.6 mm Hg, p < 0.001) and pH (7.28 +/- 0.09 versus 7.4 +/- 0.09, p < 0.001), but a similar level of oxygenation. The new approach did not reduce mortality at Day 60 (46.6% versus 37.9% in control subjects, p = 0.38), the duration of mechanical ventilation (23.1 +/- 20.2 versus 21.4 +/- 16. 3 d, p = 0.85), the incidence of pneumothorax (14% versus 12%, p = 0. 78), or the secondary occurrence of multiple organ failure (41% versus 41%, p = 1). We conclude that no benefit could be observed with reduced VT titrated to reach plateau pressures around 25 cm H2O compared with a more conventional approach in which normocapnia was achieved with plateau pressures already below 35 cm H2O.

Adolescent↗
PubMed1998

Expiratory valves used for home devices: experimental and clinical comparison.

A bench study followed by a clinical trial were performed to evaluate the mechanical characteristics of five (commercially available) expiratory valves used for home ventilators, as well as the potential clinical impact of differences between these valves. In the in vitro study, expiratory valve resistance was evaluated under unvarying conditions, whereas dynamic behaviour was evaluated by calculating the imposed expiratory work of breathing during a simulated breath generated by a lung model. Differences in resistance and imposed expiratory work of up to twofold and 150%, respectively, were found across valves. We then conducted a randomized crossover clinical study to compare the effects of the least resistive (Bennett) and most resistive expiratory valves (Peters) in 10 intubated patients receiving pressure support ventilation. There were no significant differences regarding blood gases or respiratory parameters except for the oesophageal pressure-time product (PTPoes), which was significantly increased by the Peters valve (236+/-113 cmH2O x s x min(-1) versus 194+/-90 cmH2O x s x min(-1)). An analysis of individual responses found that the Peters valve induced substantial increases in intrinsic positive end-expiratory pressure (PEEP), PTPoes, and expiratory activity in those patients with the greatest ventilatory demand. In conclusion, differences between home expiratory valve resistances may have a clinically relevant impact on the respiratory effort of patients with a high ventilatory demand.

Adult↗
PubMed1997

Effects of ventilation in ventral decubitus position on respiratory mechanics in adult respiratory distress syndrome.

OBJECTIVE: To assess the potential benefits of a period of ventilation in ventral decubitus (VD) on oxygenation and respiratory mechanics in the adult respiratory distress syndrome (ARDS). DESIGN: In a stable condition during baseline ventilation in dorsal decubitus (DD), after 15 min of ventilation in VD and after 10 min of restored DD, the following parameters were studied: arterial blood gas tension, haemodynamics and static respiratory compliance (Crs), evaluated with the rapid airway occlusion technique. SETTING: The study was completed in the intensive care units of university hospitals as part of the management of the patients studied. PATIENTS: Twelve patients (7 males, 5 females, mean age 51.8 +/- 16.6 years) suffering from ARDS of different aetiologies. INTERVENTIONS: Before and during each evaluation, the patients were kept under stable haemodynamic and metabolic conditions. The ventilatory setting was kept constant. All the patients were sedated, paralysed and mechanically ventilated. RESULTS: A statistically significant increase in the ratio between the arterial partial pressure of oxygen and fractional inspired oxygen (p < 0.01) was observed between the baseline conditions (mean 123.9 +/- 22.6) and VD (mean 153.0 +/- 16.9), while no statistical significant was noted between baseline conditions and after 10 min of restored DD (mean 141.1 +/- 19.7). A significant increase in Crs (p < 0.001) was observed between baseline conditions (mean 42 +/- 10.1) and VD (mean 48.8 +/- 9.6) and between baseline conditions and restored DD (mean 44.7 +/- 10.6). Two patients were considered nonresponders. All the patients were haemodynamically stable. No side effects were noted. CONCLUSIONS: We observed an increase in oxygenation and Crs when the patients were turned from the supine to the prone position with the upper thorax and pelvis supported.

Adult↗
PubMed1997

NéoGanesh: a working system for the automated control of assisted ventilation in ICUs.

Automating the control of therapy administered to a patient requires systems which integrate the knowledge of experienced physicians. This paper describes NéoGanesh, a knowledge-based system which controls, in closed-loop, the mechanical assistance provided to patients hospitalized in intensive care units. We report on how new advances in knowledge representation techniques have been used to model medical expertise. The clinical evaluation shows that such a system relieves the medical staff of routine tasks, improves patient care, and efficiently supports medical decisions regarding weaning. To be able to work in closed-loop and to be tested in real medical situations, NéoGanesh deals with a voluntarily limited problem. However, embedded in a powerful distributed environment, it is intended to support future extensions and refinements and to support reuse of knowledge bases.

Artificial Intelligence↗
PubMed1997

Effects of positive end-expiratory pressure and different tidal volumes on alveolar recruitment and hyperinflation.

BACKGROUND: The morphologic effect of positive end-expiratory pressure (PEEP) and of two tidal volumes were studied by computed tomography to determine whether setting the tidal volume (Vt) at the upper inflection point (UIP) of the pressure-volume (P-V) curve of the respiratory system or 10 ml/kg have different effects on hyperinflation and alveolar recruitment. METHODS: Alveolar recruitment and hyperinflation were quantified by computed tomography in nine patients with the acute respiratory distress syndrome (ARDS). First, end expiration was compared without PEEP and with PEEP set at the lower inflection point of the P-V curve; second, at end inspiration above PEEP, a reduced Vt set at the UIP (rVt) and a standard 10 ml/kg Vt (Vt) ending above the UIP were compared. Three lung zones were defined from computed tomographic densities: hyperdense, normal, and hyperinflated zones. RESULTS: Positive end-expiratory pressure induced a significant decrease in hyperdensities (from 46.8 +/- 18% to 38 +/- 15.1% of zero end-expiratory pressure (ZEEP) area; P < 0.02) with a concomitant increase in normal zones (from 47.3 +/- 20.9% to 56.5 +/- 13.2% of the ZEEP area; P < 0.05), and a significant increase in hyperinflation (from 8.1 +/- 5.9% to 17.8 +/- 12.7% of ZEEP area; P < 0.01). At end inspiration, a significant increase in hyperinflated areas was observed with Vt compared with rVt (33.4 +/- 17.8 vs. 26.8 +/- 17.3% of ZEEP area; P < 0.05), whereas no significant difference was observed for both normal and hyperdense zones. CONCLUSIONS: Positive end-expiratory pressure promotes alveolar recruitment; increasing Vt above the UIP seems to predominantly increase hyperinflation.

Adolescent↗
PubMed1997

Gelatinases in epithelial lining fluid of patients with adult respiratory distress syndrome.

Gelatinases A and B are matrix metalloproteinases secreted as inactive pro forms and are capable of degrading basement membrane components after activation in the extracellular environment. To determine whether the presence of gelatinases A (noninflammatory cells) and B (inflammatory cells) in epithelial lining fluid (ELF) is associated with the adult respiratory distress syndrome (ARDS), we studied 28 patients divided into four groups based on the presence of ARDS and/or multiple organ failure (MOF). Gelatinase activities were quantified in ELF using zymography. ARDS patients had larger ELF volumes than non-ARDS patients: 9.2 +/- 8.5 ml/100 ml recovered lavage fluid (n = 18) vs. 1.9 +/- 1.7 ml/100 ml (n = 11), respectively (P < 0.001). The presence of activated gelatinase A in ELF was a sensitive (16 out of 18 ARDS patients, 89%) and specific (0 out of 11 non-ARDS patients with or without MOF) marker for ARDS. Activated gelatinase (A + B) activities per microliter ELF were correlated with albumin concentrations in ELF (P < 0.01), and activated gelatinase activities in ELF were correlated with the volume of ELF (P < 0.0005). This could suggest an involvement of these gelatinases in alveolar-capillary permeability increase.

Adult↗
PubMed1997

Ventilatory and hemodynamic effects of continuous positive airway pressure in left heart failure.

The ventilatory and hemodynamic effects of continuous positive airway pressure (CPAP) delivered via a face mask (at 0, 5, and 10 cm H2O, and after a return to 0 cm H2O) were studied in nine patients with acute left heart failure (pulmonary artery occlusion pressure [PAOP] > or = 18 mm Hg, and cardiac index [CI] < or = 2.8 L/min/m2). CPAP at 10 cm H2O induced an improvement in lung compliance (60 +/- 10 ml/cm H2O to 87 +/- 20 ml/cm H2O, p < 0.05) and in lung and airway resistance (5.7 +/- 1.0 cm H2O/L/s to 3.4 +/- 1.0 cm H2O/L/s, p < 0.05), a reduction in work of breathing (18 +/- 3 J/min to 12 +/- 2 J/min, p < 0.05), and in the pressure-time index of the respiratory muscles (279 +/- 22 cm H2O/s/min to 174 +/- 25 cm H2O/s/min, p < 0.05), without significant changes in breathing pattern. Despite a significant reduction in the negative swings in intrathoracic pressure (15.2 +/- 1.9 cm H2O to 10.8 +/- 1.8 cm H2O, p < 0.001), no significant change was observed in CI or stroke volume during CPAP. However, mean transmural filling pressures decreased significantly with CPAP, suggesting a better cardiac performance. Neither the level of stroke volume nor of PAOP, was predictive of changes in CI or in stroke volume. In patients with respiratory insufficiency caused by congestive heart failure (CHF), CPAP reduces respiratory muscle effort without altering cardiac output. The slight decrease in mean transmural left and right atrial pressures suggests an improvement in cardiac performance.

Adult↗
PubMed1997

Pressure-volume curves in acute respiratory failure: automated low flow inflation versus occlusion.

Pressure-volume (P-V) curves of the respiratory system allow determination of compliance and lower and upper inflection points (LIP and UIP, respectively). To minimize lung trauma in mechanical ventilation the tidal volume should be limited to the P-V range between LIP and UIP. An automated low flow inflation (ALFI) technique, using a computer-controlled Servo Ventilator 900C, was compared with a more conventional technique using a series of about 20 different inflated volumes (Pst-V curve). The pressure in the distal lung (Pdist) was calculated by subtraction of resistive pressure drop in connecting tubes and airways. Compliance (Cdist), Pdist(LIP), and Pdist(UIP) were derived from the Pdist-V curve and compared with Cst, Pst(LIP), and Pst(UIP) derived from the Pst-V curve. Nineteen sedated, paralyzed patients (10 with ARDS and 9 with ARF) were studied. We found: Cdist = 2.3 + 0.98 x Cst ml/cm H2O (r = 0.98); Pdist(LIP) = 0.013 + 1.09 x Pst(LIP) cm H2O (r = 0.96). In patients with ARDS: Pdist(UIP) = 4.71 + 0.84 x Pst(UIP) cm H2O (r = 0.94). In ARF, we found differences in UIP between the methods, but discrepancies occurred above tidal volumes and had little practical importance. They may reflect that Pdist comprises dynamic phenomena contributing to pressure in the distal lung at large volumes. Compliance, but not LIP and UIP, could be accurately determined without subtraction of resistive pressure from the pressure measured in the ventilator. We conclude that ALFI, which is fully automated and needing no ventilator disconnection, gives useful clinical information.

Acute Disease↗
PubMed1997

Lower respiratory tract colonization and infection during severe acute respiratory distress syndrome: incidence and diagnosis.

Ventilator-associated pneumonia (VAP) is difficult to detect and is often unsuspected during adult respiratory distress syndrome (ARDS). We prospectively evaluated lower respiratory tract (LRT) colonization and infection in 30 patients with severe ARDS (PaO2/FIO2 ratio < 150 mm Hg), using repeated quantitative cultures of plugged telescopic catheter (PTC) specimens taken blindly via the endotracheal tube every 48 to 72 h after onset of ARDS. All patients except one were receiving antibiotics. When VAP was suspected on the presence of clinical criteria for infection, a repeated PTC and, when possible, a bronchoalveolar lavage (BAL) were obtained before any new antimicrobials were administered; samples growing > or = 10(3) cfu/ml (PTC) or > or = 10(4) cfu/ml (BAL) were considered diagnostic of infection. Twenty-four VAP episodes were diagnosed in 18 patients (60% of patients or 4.2/100 ventilator-days) a mean of 9.8+/-5.7 d after onset of ARDS. Eighteen LRT colonization episodes were recorded; 16 of 24 (66%) VAP episodes were preceded (by 2 to 6 d) by LRT colonization with the same organism(s), and only two episodes of colonization were not followed by VAP. We conclude that although VAP is of relatively late-onset during severe ARDS, its incidence is much higher than in other conditions and can be underestimated. Lower airways colonization is consistently followed by infection with the same organisms and precedes VAP in two thirds of episodes. Repeated protected specimens taken blindly may provide a useful means to predict infection and therefore allow early antimicrobial therapy in high-risk patients with diffuse lung injury.

Acute Disease↗
PubMed1997

Noninvasive pressure support ventilation: physiological and clinical results in patients with COPD and acute respiratory failure.

Noninvasive ventilation may bring considerable benefits in the treatment of acute respiratory failure, especially in patients with chronic obstructive pulmonary disease. Reduction in the need for endotracheal intubation has been well-documented. In selected groups a reduction in morbidity, mortality, and length of hospital stay have been demonstrated. The efficacy of the technique is very dependent on the skill and motivation of the team.

Acute Disease↗
PubMed1996

[Non-invasive modalities of mechanical ventilation].

When first developed in the fifties and sixties during the major polio epidemics, artificial ventilation was a major advance in medical care. The negative pressure perithoracic "iron lungs" had however many disadvantages and were widely replaced by positive pressure ventilation with intubation. This invasive technique allows normalization of gas exchange but has the disadvantage of requiring artificial sedation of the respiratory muscles in many cases in addition to the risk of secondary complications. Several authors have recently shown that in many cases, intubation may not be necessary since nasal mask positive pressure ventilation can provide satisfactory results in selected patients. Basically, indications involve patients suffering from acute decompensation of chronic obstructive respiratory failure. Prospective studies have demonstrated beneficial effects in terms of dyspnea and patient discomfort. A clear improvement over the classical medical care (oxygen, bronchodilators, antibiotics) has been observed. Other indications include certain cases of acute neuromuscular diseases, cardiogenic pulmonary edema or severe acute pneumonia. The technique can rarely be used 24 hours a day, at least during the first days of therapy and cannot provide total respiratory support in case of acute respiratory failure. Other inconveniences include leaks around the mask and the need for careful surveillance by the health care workers. Today, there are several arguments based on prospective clinical studies showing that intubation may be avoided in certain patients by using non-invasive positive pressure ventilation with a nasal mask. Careful patient selection is however essential in addition to knowledge of the limitations of the technique.

Humans↗
PubMed1996

Clinical evaluation of a continuous intra-arterial blood gas system in critically ill patients.

OBJECTIVE: To evaluate the clinical performance of a new, continuous intra-arterial blood gas monitoring system (CIABG) in abnormal ranges of blood gases, and during episodes of low blood pressure, in critically ill patients. DESIGN: Prospective study. SETTINGS: Medical ICU, University Hospital. METHODS: The CIABG system, based on fluorescent dyes, consists of a fiber-optic sensor introduced through an arterial catheter. Twenty-one sensors were evaluated in 15 acutely ill patients. A high failure rate (6/21) was found, due to the brittleness of the fibers. The bias, between CIABG and standard method, and precision were determined for each fiber and for the overall values. Analysis focused on the data collected in patients with arterial oxygen tension (PaO2) values below 75 mmHg, pH lower than 7.35 and arterial carbon dioxide partial pressure (PaCO2) values exceeding 50 mmHg and during episodes of low blood pressure. The accuracy of the CIABG to follow sequential changes in blood gases was studied among the abnormal values. RESULTS: Measurements with CIABG among the abnormal values showed biases of +2mmHg, +0.1mmHg and +0.005 for PaO2, PaCO2 and pH, respectively, and precisions of 9.0mmHg, 3.5mmHg and 0.027, respectively. Bias and precision were not influenced by hemodynamic instability. A substantial difference in the performance of individual CIABG was observed for PaO2 analysis, with 30% of the fibers having a much poorer performance than the others. The sensors were kept in place for 5 +/- 2 days and the drift rate per day was 0.005 for pH, 0.6mmHg for PaCO2 and -1.2mmHg for PaO2. CONCLUSION: In situations of severe hypoxemia, hypercapnia and acidosis, the agreement between CIABG and arterial blood sampling (ABS) is better for PaCO2 and pH than for PaO2, and is not influenced by episodes of low blood pressure.

Adult↗
PubMed1996

Intrapleural administration of streptokinase in complicated purulent pleural effusion: a CT-guided strategy.

OBJECTIVE: To determine the usefulness and the results of a strategy using intrapleural streptokinase (SK) instillation guided by repeated computed tomography (CT) scan examinations in pleural empyemas unresponsive to chest tube drainage. DESIGN: A retrospective chart review. SETTING: The medical Intensive Care Unit and Department of Radiology, in a university hospital. PATIENTS: Sixteen patients with empyema who had a persistent pleural effusion despite drainage, among 37 patients with infectious pleural effusion. INTERVENTIONS: In the 16 patients, CT examination was performed before and at least once after SK. Intrapleural SK was instilled, either through the chest tube or via a needle puncture, according to the CT scan results. RESULTS: The first CT scan confirmed a persistent effusion in all, showing a multiloculated effusion in 13 patients, and an ectopic loculus in one. The first SK instillation resulted in a dramatic increase of fluid drained per day (from 68 +/- 28 ml to 567 +/- 262 ml; p < 0.001), leading to complete resolution in 11 patients, while the others required a second CT scan-guided procedure. In one, the chest tube was misplaced, while in two, transparietal injection was needed. Finally, a complete resolution was observed in 14 (87.5%) of the patients. Two patients had a poor initial response to SK and were eventually scheduled for video-thoracoscopy. A single episode of chills and fever was observed among 32 SK instillations. CONCLUSION: CT-guided SK instillation in pleural empyema appears to be safe, and allowed complete resolution in 87.5% of our patients.

Adult↗
PubMed1996

Noninvasive estimate of work of breathing due to the endotracheal tube.

BACKGROUND: Although evidence suggests that secretions lining the inner wall of the endotracheal tube (ETT) often reduce its cross-sectional area, no data are available on the work of breathing as affected by the ETT. A noninvasive method is proposed for estimating the additional work of breathing necessitated by the ETT in patients whose lungs are mechanically ventilated. This method (the acoustic-Blasius method) involves (1) determining the inner geometry of the ETT using the acoustic reflection method and (2) using these geometric data to solve the Blasius equation that characterizes the ETT pressure drop-flow relation. METHODS: To evaluate the acoustic-Blasius method in vivo, the authors computed the work of breathing due to the ETT in four healthy persons breathing through an ETT connected to a pressure-support device and in five tracheally intubated patients receiving mechanical assistance in the pressure-support mode. For the tracheally intubated patients, the reference value was the work calculated from the ETT pressure drop measured between the two ends of the ETT using a pressure catheter. RESULTS: In the healthy participants and the tracheally intubated patients, there was close agreement between inspiratory work per cycle values estimated by directly measuring the ETT pressure drop and calculated using the acoustic-Blasius method: The difference was consistently less than 0.08 joules (< 10% of the reference value). CONCLUSIONS: The data show that the acoustic-Blasius method allows noninvasive quantification of the ETT-related work of breathing in situ.

Humans↗
PubMed1996

Gradual reduction of endotracheal tube diameter during mechanical ventilation via different humidification devices.

BACKGROUND: Limited data suggest that increased resistance to flow within endotracheal tubes (ETT) may occur in patients whose lungs are mechanically ventilated for more than 48 h, especially when airway humidification is inadequate. This could lead to sudden ETT obstruction or induce excessive loading during spontaneous breathing. METHODS: Twenty-three such patients were randomly assigned to three types of airway humidifier based on three different working principles: a Fisher Paykell hot water system (n = 7), a Pall BB2215 heat and moisture exchanger (HME) hydrophobic filter (n = 8), and a Dar Hygrobac 35254111 HME hygroscopic filter (n = 8). The decrease in internal pressure along the ETT and the flow rate were measured in each patient every 2 days. An "effective inner diameter" was derived from these measurements and allowed the inner ETT configuration to be monitored. RESULTS: On the first day of intubation, the mean diameter was similar in the three groups, and was slightly smaller than the in vitro diameter (mean +/- SD: 7.6 +/- 0.6 mm for Fisher-Paykell, 7.7 +/- 0.4 for Pall, and 7.5 +/- 0.4 for Dar). The mean diameter tended to decrease from day to day. At the end of the study, the overall reduction in mean diameter was significantly greater with the hydrophobic HME (Pall) than with the two other systems (Pall: -6.5 +/- 4% vs. 2.5 +/- 2.5% for Dar and 1.5 +/- 3% for Fisher-Paykell; P < 0.01 with analysis of variance). The same was true of the mean reduction in effective inner ETT diameter expressed per day of ventilation (-1.6 +/- 1.5% per day for Pall vs. -0.5 +/- 0.4% for Dar and -0.2 +/- 0.4% for Fisher-Paykell; P < 0.01). In four patients, the ETT became obstructed and emergency repeated tracheal intubation was required. The Pall HME and the Fisher-Paykell system were being used in three and one patient, respectively. Before obstruction, the reduction in ETT diameter was significantly greater for these four patients than for the remaining 23 patients (7.8 +/- 1.4% vs. 3.1 +/- 4.1%; P < 0.01). CONCLUSIONS: During prolonged mechanical ventilation, significant alterations in inner ETT configuration occur frequently and are influenced by the type of humidification device used. In vivo monitoring of ETT mechanical properties might be clinically useful.

Aged↗