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L Brochard

Publications and source records attributed to L Brochard.

At least 19 recordsLinked to original sources
PubMed2007

CO2 elimination at varying inspiratory pause in acute lung injury.

Previous studies have indicated that, during mechanical ventilation, an inspiratory pause enhances gas exchange. This has been attributed to prolonged time during which fresh gas of the tidal volume is present in the respiratory zone and is available for distribution in the lung periphery. The mean distribution time of inspired gas (MDT) is the mean time during which fractions of fresh gas are present in the respiratory zone. All ventilators allow setting of pause time, T(P), which is a determinant of MDT. The objective of the present study was to test in patients the hypothesis that the volume of CO(2) eliminated per breath, V(T)CO(2), is correlated to the logarithm of MDT as previously found in animal models. Eleven patients with acute lung injury were studied. When T(P) increased from 0% to 30%, MDT increased fourfold. A change of T(P) from 10% to 0% reduced V(T)CO(2) by 14%, while a change to 30% increased V(T)CO(2) by 19%. The relationship between V(T)CO(2) and MDT was in accordance with the logarithmic hypothesis. The change in V(T)CO(2) reflected to equal extent changes in airway dead space and alveolar PCO(2) read from the alveolar plateau of the single breath test for CO(2). By varying T(P), effects are observed on V(T)CO(2), airway dead space and alveolar PCO(2). These effects depend on perfusion, gas distribution and diffusion in the lung periphery, which need to be further elucidated.

Aged↗
PubMed2006

B-type natriuretic peptide to assess haemodynamic status after cardiac surgery.

BACKGROUND: B-type natriuretic peptide (BNP) is the most powerful hormonal marker of left ventricular dysfunction and could be considered as an indicator of ventricular preload. The aim of this prospective study was to compare the respective value of BNP and cardiac filling pressures to assess the response to volume load after cardiac surgery. METHODS: Thirty-seven mechanically ventilated patients suffering from acute circulatory failure immediately after cardiac surgery, and equipped with a pulmonary-artery catheter were included. All haemodynamic measurements were taken before and after volume expansion using 500 ml of 4% modified fluid gelatin. RESULTS: Fifteen patients were volume responders (CI increase>or=15%) and 22 were non-responders. Right atrial pressure, pulmonary-artery occlusion pressure and BNP before volume loading were not significantly different between the responders and non-responders. BNP concentration before volume infusion significantly correlated to preoperative left ventricular ejection fraction, aortic cross-clamping time, serum creatinine, mean pulmonary arterial pressure and intensive care unit duration whereas no correlation was found with pulmonary-artery occlusion pressure or cardiac index. CONCLUSION: BNP level after cardiac surgery was influenced by many perioperative variables, limiting its usefulness as an indicator of cardiac preload or a predictor of volume responsiveness in this population.

Aged↗
PubMed2005

Origin of ICU acquired paresis determined by direct muscle stimulation.

BACKGROUND: Acquired diffuse paresis in an intensive care unit (ICU) can result from critical illness myopathy or polyneuropathy. Clinical examination and conventional neurophysiological techniques may not distinguish between these entities. OBJECTIVE: To assess the value of direct muscle stimulation (DMS) to differentiate myopathic from neuropathic process in critically ill patients with diffuse severe muscle weakness. METHODS: 30 consecutive patients with ICU acquired diffuse motor weakness were studied. Responses of the right deltoid and tibialis anterior muscles to DMS and to motor nerve stimulation (MNS) were studied and compared with results of conventional nerve conduction studies and concentric needle electromyography (EMG). An original algorithm was used for differential diagnosis, taking into account first the amplitude of the responses to DMS, then the MNS to DMS amplitude ratio, and finally the amplitude of the sensory nerve action potentials recorded at the lower limbs. RESULTS: Evidence of neuropathy and myopathy was found in 57% and 83% of the patients, respectively. Pure or predominant myopathy was found in 19 patients. Other results were consistent with neuromyopathy (n = 5) and pure or predominant neuropathy (n = 2). Four patients had normal results with stimulation techniques, but spontaneous EMG activity and raised plasma creatine kinase suggesting necrotic myopathy. CONCLUSIONS: A neurophysiological approach combining DMS and conventional techniques revealed myopathic processes in a majority of ICU patients. Reduced muscle fibre excitability may be a leading cause for this. The diagnosis of myopathy in ICU acquired paralysis can be established by a combination of DMS, needle EMG, and plasma creatine kinase.

Adolescent↗
PubMed2003

What has been learnt from P/V curves in patients with acute lung injury/acute respiratory distress syndrome.

Mechanical impairment of the respiratory system was recognised soon after the description of acute respiratory distress syndrome. The analysis of the pressure/volume (P/V) curve of the respiratory system contributed a lot to the understanding of the pathophysiology of acute lung injury and formed the basis for lung protection. The lower and upper inflection points were regarded as points of interest to avoid cyclic derecruitment and overdistension and to optimise ventilatory settings. However, because of the heterogeneity of lung injury, reducing the mechanical properties of the whole respiratory system to a single curve is a schematic approach, which makes interpretation difficult. New data suggest that alveolar re-inflation occurs along the whole P/V curve that can, therefore, be considered as a recruitment curve. The lower inflection point has no relationship with alveolar opening and closure and does not indicate the positive end-expiratory pressure needed to prevent alveolar collapse. The shape of the P/V curve gives information about the extension and the homogeneity of lung injury, indicating the possibility of lung recruitment. The upper inflection point, classically seen as the beginning of overdistension, may also indicate the end of recruitment. The pressure/volume curve offers the unique opportunity of evaluating alveolar recruitment/derecruitment at the bedside that can be helpful for the identification of optimal ventilatory settings and makes the curve a valuable tool for the ventilatory management of acute lung injury.

Acute Disease↗
PubMed2003

Mechanical ventilation: invasive versus noninvasive.

Mechanical ventilation is the most widely used supportive technique in intensive care units. Several forms of external support for respiration have long been described to assist the failing ventilatory pump, and access to lower airways through tracheostomy or endotracheal tubes had constituted a major advance in the management of patients with respiratory distress. More recently, however, new "noninvasive" ventilation (NIV) techniques, using patient/ventilator interfaces in the form of facial masks, have been designed. The reasons for promoting NIV include a better understanding of the role of ventilatory pump failure in the indications for mechanical ventilation, the development of ventilatory modalities able to work in synchrony with the patient, and the extensive recognition of complications associated with endotracheal intubation and standard mechanical ventilation. NIV has been used primarily for patients with acute hypercapnic ventilatory failure, and especially for acute exacerbation of chronic obstructive pulmonary disease. In this population, the use of NIV is associated with a marked reduction in the need for endotracheal intubation, a decrease in complication rate, a reduced duration of hospital stay and a substantial reduction in hospital mortality. Similar benefits have also been demonstrated in patients with asphyxic forms of acute cardiogenic pulmonary oedema. In patients with primarily hypoxemic forms of respiratory failure, the level of success of NIV is more variable, but major benefits have also been demonstrated in selected populations with no contraindications such as multiple organ failure, loss of consciousness or haemodynamic instability. One important factor in success seems to be the early delivery of noninvasive ventilation during the course of respiratory failure. Noninvasive ventilation allows many of the complications associated with mechanical ventilation to be avoided, especially the occurrence of nosocomial infections. The current use of noninvasive ventilation is growing up, and is becoming a major therapeutic tool in the intensive care unit.

Acute Disease↗
PubMed2003

Induction of type-IIA secretory phospholipase A2 in animal models of acute lung injury.

The aim of this study was to evaluate the presence of type-II secretory phospholipase A2 (sPLA2-IIA) in alveolar space and its possible role in the destruction of surfactant in three rat models of acute lung injury. Alveolar instillation of either lipopolysaccaride or live Pseudomonas aeruginosa resulted in a significant increase in lung oedema and in a decrease in static compliance of the respiratory system together with alveolar-neutrophil influx as compared with healthy control rats. The upregulation of messenger ribonucleic acid and sPLA2-IIA by the lung was evident. This was associated with surfactant degradation and a decrease in large:small ratio of surfactant aggregates in bacteria-instilled rats. A negative correlation between compliance and sPLA2-IIA activity in bronchoalveolar lavage fluid was shown. By contrast, during alpha naphthylthiourea-induced injury, neither alveolar-neutrophil influx nor increase in sPLA2-IIA activity was observed. Additional experiments in rats treated with a specific inhibitor of type-II secretory phospholipase A2 activity (3 acetamine-1-benzyl-2 ethylindolyl-5 oxy; propane phosphonic acid (LY311727)) demonstrated no improvement in physiological parameters despite a biochemical effect, suggesting that its activity is only one of the multiple factors involved in the pathophysiology of lung injury.

Animals↗
PubMed2002

Bench testing of pressure support ventilation with three different generations of ventilators.

OBJECTIVE: The new generations of intensive care ventilators tend to be more innovative and sophisticated than previous ones, but little is known about their respective performance for delivering pressure support ventilation (PSV) and how they compare to previous generations. DESIGN: Active lung model bench test. APPARATUS: Twenty-two commercially available ventilators classified into three categories: new generation ventilators (after 1993, n=7), previous generation (before 1993, n=6), and recent piston or turbine-based ventilators ( n=9). MEASUREMENTS AND RESULTS: During PSV, the unloading efficacy of the assistance depends on the ventilator's ability to meet inspiratory flow demand. Three levels of flow (0.1 l/s, 0.6 l/s, and 1.2 l/s) were used to simulate inspiratory demand and the net area of the inspiratory airway pressure-time trace was calculated over the first 0.3 s, 0.5 s, and 1 s (Area (0.3), Area (0.5), and Area (tot)) with three levels of PSV (5 cmH(2)O, 10 cmH(2)O, and 15 cmH(2)O). To assess the respective role of pressure support delivery and triggering function, triggering sensitivity was assessed independently by measuring the time delay ( TD (tg)) and the pressure fall (Delta Paw (tg)) with two levels of inspiratory drive. All the new generation ventilators exhibited significantly better results than most of the previous generation ventilators regarding Area (0.3) and TD (tg), indicating large improvements in terms of triggering and pressurisation. CONCLUSION: Regarding PSV and trigger performance, the new generation ventilators - but also some piston and turbine-based ventilators - outperform most of previous generation ventilators.

Benchmarking↗
PubMed2002

[Main points in intensive care medicine].

PURPOSE: Progresses in intensive care medicine have concerned major syndromes associated with life threatening organ dysfunction, like the acute respiratory distress syndrome (ARDS) or septic shock. CURRENT KNOWLEDGE AND KEY POINTS: A better understanding of interactions between mechanical ventilation and the underlying lung lesions, has lead to define a so-called "lung protective ventilation", which resulted in an improved prognosis of ARDS. In numerous situations of acute respiratory failure, including acute exacerbation of chronic obstructive pulmonary disorder or immunosuppressed patients, endotracheal intubation can be avoided by the use of face mask ventilation, also called noninvasive ventilation. This approach results in a reduction of complications associated with mechanical ventilation or with the entire intensive care unit stay, including nosocomial infections. As a result, survival is increased when this kind of ventilation is feasible. In septic shock, pharmacological improvements have concerned effects of sepsis on coagulation, and the unexpectedly high frequency of relative adrenal insufficiency. Lastly, improvements have been made regarding the prevention and management of ventilator-associated pneumonia.

Adult↗
PubMed2002

Noninvasive ventilation for acute respiratory failure.

Noninvasive ventilation (NIV) has emerged as a significant advance in the management of respiratory failure. There is now a wide body of prospective randomized-controlled trial data to support its use, particularly in the management of patients with acute or respiratory failure due to exacerbations of chronic obstructive pulmonary disease (COPD). Its successful application results in a more rapid resolution of the physiological derangements, reduces the need for intubation and, in larger studies, improves survival. A reduction in the number of infectious complications is a particular advantage. In patients with acute exacerbations of COPD there is evidence of benefit when NIV is introduced earlier in the course of the illness than would be the case for invasive ventilation and it should now be considered even with mild acidosis (pH<7.35) and tachypnoea (respiratory rate >23 breaths x min(-1)) after initial medical therapy. There is less clinical-trial data in patients with hypoxaemic respiratory failure, but again as with COPD those with less severe physiological disturbance are more likely to benefit. By contrast noninvasive continuous positive airways pressure, while being widely used has not been shown to reduce the need for intubation or to improve survival in patients with hypoxaemic respiratory failure, with the exception of acute cardiogenic pulmonary oedema. Noninvasive ventilation has been a real advance in the treatment of the critically ill. Most of the studies published to date, have excluded patients needing immediate intubation and it should be viewed as a complimentary technique rather than an alternative to invasive ventilation. It is best viewed as a means of preventing the need for endotracheal intubation and as a result should be introduced earlier than would be the case for invasive ventilation.

Acute Disease↗
PubMed2001

Alveolar derecruitment at decremental positive end-expiratory pressure levels in acute lung injury: comparison with the lower inflection point, oxygenation, and compliance.

We examined the hypothesis that recording multiple elastic pressure-volume (Pel/V) curves and calculating alveolar derecruitment (V(DER)) induced by decreasing positive end-expiratory pressure (PEEP) may allow determination of alveolar closing pressures, thus helping to select the optimal PEEP level. V(DER) measured in 16 patients with acute lung injury (ALI) was compared with the lower inflection point (LIP) and oxygenation changes. A modified automated method was used to record multiple Pel/V curves at low constant flow. PEEP was decreased in 5-cm H(2)O steps, from 20 or 15 cm H(2)O to 0 cm H(2)O (ZEEP). V(DER) was the volume loss between the curves recorded from PEEP and from ZEEP at the same Pel. Derecruitment occurred at each PEEP decrement, being spread almost uniformly over the 20/15 to 0 cm H(2)O range. V(DER) was not correlated with LIP. V(DER) changes correlated with Pa(O(2))/FI(O(2)) changes (rho = 0.6, p = 0.02). Linear compliance at ZEEP was correlated to V(DER) at PEEP 15 cm H(2)O (rho = 0.9, p = 0.001), suggesting that compliance above LIP may reflect the amount of recruitable lung. Thus, alveolar closure in ALI occurs over a wide range of pressures, and LIP is a poor predictor of alveolar closure.

Adult↗
PubMed2001

Helium-oxygen in the postextubation period decreases inspiratory effort.

After tracheal extubation, upper and total airway resistances may frequently be increased resulting in an increase in inspiratory effort to breathe. We tested whether breathing a helium-oxygen mixture (HeO(2)) would reduce inspiratory effort in the period after extubation. Eighteen consecutive patients with no chronic obstructive pulmonary disease who had received mechanical ventilation (> 48 h) were successively studied immediately after extubation (N(2)O(2)), 15 min after breathing HeO(2), and after return to N(2)O(2). Effort to breathe, assessed by the transdiaphragmatic pressure swings (DeltaPdi) and the pressure-time index of the diaphragm (PTI), comfort, and gas exchange, were the main end points. The mean reduction of the transdiaphragmatic pressure under HeO(2) was 19 +/- 5%. All but three patients presented a decrease in transdiaphragmatic pressure under HeO(2), ranging from - 4 to - 55%, and a significant reduction in DeltaPdi was observed between HeO(2) and N(2)O(2) (10.2 +/- 0.7 versus 8.6 +/- 1.1 versus 10.0 +/- 0.8 cm H(2)O for the three consecutive periods; p < 0.05). PTI also differed significantly between HeO(2) and N(2)O(2) (197 +/- 19 versus 166 +/- 22 versus 201 +/- 23 cm H(2)O/s/min for the three periods; p < 0.05). Breathing HeO(2) significantly improved comfort, whereas gas exchange was not modified. We conclude that the use of HeO(2) in the immediate postextubation period decreases inspiratory effort and improves comfort.

Administration, Inhalation↗
PubMed2001

Effects of hydroxyethylstarch and gelatin on renal function in severe sepsis: a multicentre randomised study.

BACKGROUND: Hydroxyethylstarch used for volume restoration in brain-dead kidney donors has been associated with impaired kidney function in the transplant recipients. We undertook a multicentre randomised study to assess the frequency of acute renal failure (ARF) in patients with severe sepsis or septic shock treated with hydroxyethylstarch or gelatin. METHODS: Adults with severe sepsis or septic shock were enrolled prospectively in three intensive-care units in France. They were randomly assigned 6% hydroxyethylstarch (200 kDa, 0.60-0.66 substitution) or 3% fluid-modified gelatin. The primary endpoint was ARF (a two-fold increase in serum creatinine from baseline or need for renal replacement therapy). Analyses were by intention to treat. FINDINGS: 129 patients were enrolled over 18 months. Severity of illness and serum creatinine (median 143 [IQR 88-203] vs 114 [91-175] micromol/L) were similar at baseline in the hydroxyethylstarch and gelatin groups. The frequencies of ARF (27/65 [42%] vs 15/64 [23%], p=0.028) and oliguria (35/62 [56%] vs 23/63 [37%], p=0.025) and the peak serum creatinine concentration (225 [130-339] vs 169 [106-273] micromol/L, p=0.04) were significantly higher in the hydroxyethylstarch group than in the gelatin group. In a multivariate analysis, risk factors for acute renal failure included mechanical ventilation (odds ratio 4.02 [95% CI 1.37-11.8], p=0.013) and use of hydroxyethylstarch (2.57 [1.13-5.83], p=0.026). INTERPRETATIONS: The use of this preparation of hydroxyethylstarch as a plasma-volume expander is an independent risk factor for ARF in patients with severe sepsis or septic shock.

Acute Kidney Injury↗
PubMed2001

Accuracy of pulse oximetry in the intensive care unit.

OBJECTIVE: Pulse oximetry (SpO2) is a standard monitoring device in intensive care units (ICUs), currently used to guide therapeutic interventions. Few studies have evaluated the accuracy of SpO2 in critically ill patients. Our objective was to compare pulse oximetry with arterial oxygen saturation (SaO2) in such patients, and to examine the effect of several factors on this relationship. DESIGN: Observational prospective study. SETTING: A 26-bed medical ICU in a university hospital. PATIENTS: One hundred two consecutive patients admitted to the ICU in whom one or serial arterial blood gas analyses (ABGs) were performed and a reliable pulse oximeter signal was present. INTERVENTIONS: For each ABG, we collected SaO2, SpO2, the type of pulse oximeter, the mode of ventilation and requirement for vasoactive drugs. MEASUREMENTS AND RESULTS: Three hundred twenty-three data points were collected. The mean difference between SpO2 and SaO2 was -0.02% and standard deviation of the differences was 2.1%. From one sample to another, the fluctuations in SpO2 to arterial saturation difference indicated that SaO2 could not be reliably predicted from SpO2 after a single ABG. Subgroup analysis showed that the accuracy of SpO2 appeared to be influenced by the type of oximeter, the presence of hypoxemia and the requirement for vasoactive drugs. Finally, high SpO2 thresholds were necessary to detect significant hypoxemia with good sensitivity. CONCLUSION: Large SpO2 to SaO2 differences may occur in critically ill patients with poor reproducibility of SpO2. A SpO2 above 94% appears necessary to ensure a SaO2 of 90%.

Bias↗
PubMed2001

Knowledge-based systems for automatic ventilatory management.

In intensive care and anesthesia, the demand for computerized medical assistants is potentially considerable, to filter and synthesize the growing mass of clinical parameters and information available. The authors detail how knowledge-based computerized assistants can be constructed for automatic ventilation management and report clinical results obtained with such a system for closed-loop control of pressure support ventilation and decision for extubation.

Algorithms↗
PubMed2001

Improved survival in cancer patients requiring mechanical ventilatory support: impact of noninvasive mechanical ventilatory support.

OBJECTIVE: When a cancer patient becomes critically ill, mechanical ventilation (MV) is often considered futile. However, recent studies have found that outcomes of critically ill cancer patients have been improving over the years and that classic predictors of high mortality have lost their relevance. DESIGN: We retrospectively determined outcomes and predictors of 30-day mortality in 237 mechanically-ventilated cancer patients admitted to the intensive care unit (ICU). PATIENTS: The 132 (55.7%) patients who were admitted between 1990 and 1995 were compared with 105 (44.3%) patients who were admitted between 1996 and 1998. The malignancy was leukemia/lymphoma in 119 (50.3%) patients, myeloma in 50 (21%), and a solid tumor in 68 (28.7%). Forty-two (17.7%) patients had bone marrow transplantation, and 91 (38.4%) were neutropenic. Median Simplified Acute Physiology Score II (SAPS II) was 58 (range, 40-75). Reasons for MV were acute hypoxemic respiratory failure in 148 (62.5%) patients, coma in 54 (22.8%), and cardiogenic pulmonary edema in 35 (14.7%). Conventional MV was used first in 189 (79.8%) patients, and noninvasive MV (NIMV) was used in 48 (20.2%). Overall mortality rate was 72.5% (172 deaths). RESULTS: Logistic regression identified three variables associated with mortality: ICU admission between 1996 and 1998 (odds ratio [OR], 0.24; 95% confidence interval [CI], 0.12-0.50) and the use of NIMV (OR, 0.34; 95% CI, 0.16-0.73) were protective, and the SAPS II was aggravating (OR, 1.04 per point; 95% CI, 1.02-1.06). To better define the impact of NIMV, we performed a pairwise-matched exposed-unexposed analysis. Forty-eight patients who did and 48 who did not receive NIMV as the first ventilation method were matched for SAPS II, type of malignancy, and period of ICU admission. Crude ICU mortality rates from exposed patients and controls were 43.7% and 70.8%, respectively. NIMV remained protective from mortality after adjustment for matching variables (OR, 0.31; 95% CI, 0.12-0.82). CONCLUSION: Our results confirm that mortality has improved over the past decade in critically ill cancer patients, even those who require MV, and suggest that this may be, in part, because of a protective effect of NIMV.

APACHE↗