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L Brochard

Publications and source records attributed to L Brochard.

At least 19 recordsLinked to original sources
PubMed1999

Changes in the work of breathing induced by tracheotomy in ventilator-dependent patients.

Tracheotomy is widely performed on ventilator-dependent patients, but its effects on respiratory mechanics have not been studied. We measured the work of breathing (WOB) in eight patients before and after tracheotomy during breathing at three identical levels of pressure support (PS): baseline level (PS-B), PS + 5 cm H2O (PS+5), and PS - 5 cm H2O (PS-5). After the procedure, we also compared the resistive work induced by the patients' endotracheal tubes (ETTs) and by a new tracheotomy cannula in an in vitro bench study. A significant reduction in the WOB was observed after tracheotomy for PS-B (from 0.9 +/- 0.4 to 0.4 +/- 0.2 J/L, p < 0.05), and for PS-5 (1.4 +/- 0.6 to 0.6 +/- 0.3 J/L, p < 0.05), with a near-significant reduction for PS+5 (0.5 +/- 0.5 to 0.2 +/- 0.1 J/L, p = 0.05). A significant reduction was also observed in the pressure-time index of the respiratory muscles (181 +/- 92 to 80 +/- 56 cm H2O. s/min for PS-B, p < 0.05). Resistive and elastic work computed from transpulmonary pressure measurements decreased significantly at PS-B and PS-5. A significant reduction in occlusion pressure and intrinsic positive end-expiratory pressure (PEEP) was also observed for all conditions, with no significant change in breathing pattern. Three patients had ineffective breathing efforts before tracheotomy, and all had improved synchrony with the ventilator after the procedure. In vitro measurements made with ETTs removed from the patients, with new ETTs, and with the tracheotomy cannula showed that the cannula reduced the resistive work induced by the artificial airway. Part of these results was explained by a slight, subtle reduction of the inner diameter of used ETTs. We conclude that tracheotomy can substantially reduce the mechanical workload of ventilator-dependent patients.

Adult↗
PubMed1998

[Use of non-invasive positive pressure ventilation for cardiogenic pulmonary edema in emergency care units].

The work reported by L'Her et al. in this issue of La Presse Médicale demonstrates the feasibility of applying simple intensive care techniques in situations frequently encountered in emergency care units. These authors used a face mask for continuous positive pressure ventilation in patients over 70 years of age admitted for respiratory distress related to cardiogenic pulmonary edema. In these elderly patients, the authors noted an improvement in blood gases, respiratory rate and heart rate and did not observe any secondary effect. Acute respiratory failure was cured in 90% of the cases without referral to the intensive care unit. The mechanism of action of continuous positive airway pressure, or spontaneous ventilation with positive expiratory pressure, is different from simple oxygen therapy. Two mechanisms are intimately related. The main effect is ventilatory assistance resulting from a "re-aeration" of the pulmonary parenchyma which increases compliance and reduces work required to overcome elastic retraction forces. Likewise the increased pulmonary volume reduces pulmonary resistance. Positive airway pressure also has an effect on left ventricular function. Indeed, after-load is reduced by the reduction in the large negative intrathoracic pressure swing. Lower energy expenditure required for respiration also greatly reduces total oxygen consumption and improved blood gases favor oxygen supply to the myocardium. The contraindications of continuous positive airway pressure are related to abnormal control of the upper airways and major hemodynamic disorders. Prudence is also required in case of shock due to the risk of major respiratory muscle fatigue. The question could also be raised as to the risk in elderly patients where cardiogenic pulmonary edema is often associated with a certain degree of chronic bronchitis. It is now known that these patients have an intrinsic positive expiratory pressure which considerably increases respiratory work. Symptomatic treatment in this type of disorder is mechanical and continuous positive airway pressure diminishes this work. Cardiogenic pulmonary edema in the elderly is thus an excellent indication for spontaneous ventilation with positive expiratory pressure. Improvement in these simple techniques, their widespread use and a better understanding of their limitations remain important challenges for the future.

Aged↗
PubMed1998

Influence of airway management on ventilator-associated pneumonia: evidence from randomized trials.

OBJECTIVE: Ventilator-associated pneumonia (VAP) is a serious complication of critical illness, conferring increased morbidity and mortality. Many interventions have been studied to reduce the risk of VAP. We systematically reviewed the influence of airway management on VAP in critically ill patients. DATA SOURCES: Studies were identified through searching MEDLINE and EMBASE from 1980 through July 1997 and by searching SCISEARCH, the Cochrane Library, bibliographies of primary and review articles, personal files, and contact with authors of the randomized trials. STUDY SELECTION: We selected randomized trials evaluating ventilator circuit and secretion management strategies on the rate of VAP. DATA EXTRACTION: Two investigators independently abstracted key data on design features, the population, intervention, and outcome of the studies. DATA SYNTHESIS: The frequency of ventilator circuit changes and the type of endotracheal suction system do not appear to influence VAP rates (3 trials, none with significant difference; range of relative risks [RRs], 0.84-0.91). However, lower VAP rates may be associated with avoidance of heated humidifiers and use of heat and moisture exchangers (5 trials, only 1 showing a significant difference; range of RRs, 0.34-0.86), use of oral vs nasal intubation (1 trial; RR, 0.52; 95% confidence interval, 0.24-1.13), subglottic secretion drainage vs standard endotracheal tubes (2 trials, 1 showing a significant difference; range of RRs, 0.46-0.57), and kinetic vs conventional beds (5 trials, only 1 showing a significant difference; range of RRs, 0.35-0.78). CONCLUSIONS: Some ventilator circuit and secretion management strategies may influence VAP rates in critically ill patients. Whether these strategies are adopted in practice depends on several factors such as the magnitude and precision of estimates of benefit and harm, as well as access, availability, and costs.

Critical Illness↗
PubMed1998

Continuous tracheal gas insufflation enables a volume reduction strategy in hyaline membrane disease: technical aspects and clinical results.

OBJECTIVE: Instrumental dead space wash-out can be used to improve carbon dioxide clearance. The aim of this study was to define, using a bench test, an optimal protocol for long-term use, and to assess the efficacy of this technique in neonates. DESIGN: A bench test with an artificial lung model, and an observational prospective study. Dead space wash-out was performed by continuous tracheal gas insufflation (CTGI), via six capillaries molded in the wall of a specially designed endotracheal tube, in 30 preterm neonates with hyaline membrane disease. SETTING: Neonatal intensive care unit of a regional hospital. RESULTS: The bench test study showed that a CTGI flow of 0.5 l/ min had the optimal efficacy-to-side-effect ratio, resulting in a maximal or submaximal efficacy (93 to 100%) without a marked increase in tracheal and CTGI circuit pressures. In the 30 newborns, 15 min of CTGI induced a significant fall in arterial carbon dioxide tension (PaCO2), from 45 +/- 7 to 35 +/- 5 mmHg (p = 0.0001), and in 14 patients allowed a reduction in the gradient between Peack inspirating pressure and positive end-expiratory pressure from 20.8 +/- 4.6 to 14.4 +/- 3.7 cmH2O (p < 0.0001) while keeping the transcutaneous partial pressure of carbon dioxide constant. As predicted by the bench test, the decrease in PaCO2 induced by CTGI correlated well with PaCO2 values before CTGI (r = 0.58, p < 0.002) and with instrumental dead space-to-tidal volume ratio (r = 0.54, p < 0.005). CONCLUSION: CTGI may be a useful adjunct to conventional ventilation in preterm neonates with respiratory disease, enabling an increase in CO2 clearance or a reduction in ventilatory pressure.

Artificial Organs↗
PubMed1998

Nonchemical influence of inspiratory pressure support on inspiratory activity in humans.

To determine whether nonchemical inhibition of respiratory activity occurs during inspiratory pressure support (IPS) ventilation (IPSV), respiratory motor output (in 9 subjects), obtained by calculating transdiaphragmatic pressure-time products, and central respiratory output (in 5 subjects), obtained by integrating the electromyographic activity of the diaphragm (EMGdi) during mechanical inspiratory time, EMGdi per minute, and electrical inspiratory time, as determined from onset to peak EMGdi, were compared during spontaneous ventilation (control) and IPSV with (IPS+CO2) and without (IPS) correction of hypocapnia. Both IPS and IPS+CO2 induced significant decreases in transdiaphragmatic pressure-time products (46 +/- 31 and 53 +/- 23%, respectively), EMGdi during mechanical inspiratory time (49 +/- 12 and 57 +/- 14%, respectively), EMGdi per minute (65 +/- 22 and 69 +/- 15%, respectively), and electrical inspiratory time (73 +/- 8 and 65 +/- 6%, respectively). Because correction of hypocapnia failed to eliminate the marked inhibition of both respiratory and central motor output seen with IPS, we conclude that nonchemical inhibition of respiratory activity occurs during IPSV.

Adult↗
PubMed1998

Contribution of the endotracheal tube and the upper airway to breathing workload.

The influence of the endotracheal tube (ETT) during a T-piece trial remains controversial. Our aim was to compare the work of breathing of 14 successfully extubated patients at the end of a 2-h trial (T) and after extubation (E) of the trachea, and to assess, using the acoustic reflection method, the resistance of the endotracheal tube and of the supraglottic airway as well as their related work. We found that the work of breathing of the patients was identical between T and E (1.72 +/- 0.59 versus 1.63 +/- 0.45 J/L; p = 0.50 and 23.5 +/- 10.6 versus 22.6 +/- 9.7 J/min; p = 0.70). There was no significant difference between the beginning and the end of the T-piece trial (1.57 +/- 0.53 versus 1.72 +/- 0.59 J/ L, p = 0.10). The work caused by the ETT amounted to 11.0 +/- 3.9% of the total work of breathing. The supraglottic airway resistance was in the normal range and was significantly smaller than the endotracheal tube resistance (0.79 +/- 0.4 versus 1.43 +/- 0.31 cm H2O x s/L; p = 0.008, flow = 0.25 L/s). We conclude that a 2-h trial of spontaneous breathing through an endotracheal tube well mimics the work of breathing performed after extubation, in patients who pass a weaning trial and do not require reintubation.

Acoustics↗
PubMed1998

Effects of flow triggering on breathing effort during partial ventilatory support.

The effects of flow triggering (FT) as compared with pressure triggering (PT) on breathing effort have been the focus of several studies, and discrepant results have been reported. In the initial part of our study, a lung model was used to quantify triggering effort (airway pressure-time product, PTPaw) for a range of sensitivity settings in nine new-generation ventilators. A ventilator providing both FT and PT was then used to compare these systems during pressure-support (PSV) and volume-targeted assist-control ventilation (ACV) in eight ventilator-dependent patients, using sensitivity settings (2 L/min for FT and -2 cm H2O for PT) that had proven significantly different in the initial bench study. Indexes of effort included the esophageal and transdiaphragmatic pressure-time products and inspiratory work of breathing per minute (PTPes/min, PTPdi/min, and Wi/min, respectively). The experimental study revealed significant differences between ventilators in PTPaw at commonly used settings. In two of three ventilators featuring both systems, PTPaw was significantly lower with FT than PT (p < 0.001). In the clinical study, FT as compared with PT, was associated with reductions in all indexes of breathing effort during PSV: 16 +/- 6% (p < 0.001), 13 +/- 10% (p < 0.01), and 14 +/- 12% (p < 0.05) for PTPdi/min, PTPes/min, and Wi/min, respectively. By contrast, no differences were found when FT was used during ACV. Although FT reduced triggering effort in both modes (p < 0.001), the effects observed during the post-trigger phase differed, and explained the discrepant results between the two modes. We conclude that FT more effectively reduces breathing effort when used in conjunction with a pressure-targeted mode than with a volume-targeted mode, especially when flow delivery is close to or below demand.

Aged↗
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↗