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J D Ricard

Publications and source records attributed to J D Ricard.

12 recordsLinked to original sources
PubMed2001

Significance of the changes in the respiratory system pressure-volume curve during acute lung injury in rats.

UNLABELLED: The hypothesis that the changes in the respiratory system pressure- volume (PV) curve during pulmonary edema mainly reflect distal airway obstruction was investigated in rats. Normal rats had a well-defined upper inflection point (UIP) at low airway pressure. Airway occlusion by liquid instillation decreased compliance (Crs) and the volume (Vuip) of the UIP, and increased end-inspiratory pressure. The same changes were observed during the progression of edema produced by high volume ventilation (HV). Changes in Vuip and in Crs produced by HV were correlated with edema severity in normal rats or rats with lungs preinjured with alpha-naphthylthiourea. Vuip and Crs changes were proportional, reflecting compression of the PV curve on the volume axis and suggesting reduction of the amount of ventilatable lung at low airway pressure. In keeping with this explanation, the lower Vuip and Crs were before HV, the more severe HV-induced edema was in alpha-naphthylthiourea-injected rats. When edema was profuse, PV curves displayed a marked lower inflection point (LIP), the UIP at low pressure disappeared but another was seen at high volume above the LIP, and the correlation between Vuip changes and edema severity was lost. These observations may have clinical relevance in the context of the "open lung" strategy. KEYWORDS: ventilator-induced lung injury; respiratory mechanics; acute respiratory distress syndrome

Airway Resistance↗
PubMed2001

Liquid ventilation.

Partial liquid ventilation (PLV) developed considerably in the clinical and experimental fields during the past few years. In addition to improved oxygenation and lung mechanics by perfluorocarbon (PFC) administration, recent animal studies have tried to optimize PLV by evaluating the most appropriate ventilatory mode to use during PLV and by adjusting the best level of positive end-expiratory pressure (PEEP). Other pathophysiological aspects of acute lung injury that may be positively affected by liquid ventilation have been studied, including regional blood flow redistribution, reduction in ventilator-induced lung injury, and antiinflammatory properties of PFC. Although the precise dosing of PFC is debated, evidence from several experimental studies supports the use of smaller doses of PFC because larger doses increase the occurrence of baro- and volutrauma. In the clinical field, after promising data from preliminary studies, an international randomized controlled trial is on the verge of completion.

Fluorocarbons↗
PubMed2001

Production of inflammatory cytokines in ventilator-induced lung injury: a reappraisal.

We investigated the production of proinflammatory cytokines by the lung during high mechanical stretch in vivo. To do this, we subjected rats to high-volume (42 ml/kg tidal volume [VT]) ventilation for 2 h. The animals developed severe pulmonary edema and alveolar flooding, with a high protein concentration in bronchoalveolar lavage fluid (BALF). The animals' BALF contained no tumor necrosis factor (TNF)-alpha, negligible amounts of interleukin (IL)-1beta, and less than 300 pg/ml of the chemokine macrophage inflammatory protein (MIP)-2, an amount similar to that found in rats ventilated with 7 ml/kg VT. Systemic cytokine levels were below the detection threshold. Because isolated lungs have been shown to produce high levels of proinflammatory cytokines when ventilated with a similarly high VT for the same duration (Tremblay, et al. J Clin Invest 1997;99:944-952), we reconsidered this specific issue. We ventilated isolated, unperfused rat lungs for 2 h with 7 ml/kg or 42 ml/kg VT, or maintained them in a statically inflated state. Negligible amounts of TNF-alpha were found in the BALF whatever the ventilatory condition applied. The BALF IL-1beta concentration was slightly elevated and higher in lungs ventilated with 42 ml/kg VT than in those ventilated with 7 ml/kg VT or in statically inflated lungs (p < 0.05). The BALF MIP-2 concentration was moderately elevated in all isolated lungs (200 to 300 pg/ml), and was slightly higher (p < 0.05) in lungs ventilated with 42 ml/kg VT. After lipopolysaccharide (LPS) challenge, high levels of TNF-alpha, IL-1beta, and MIP-2 were found in the animals' plasma before the lungs were removed. Negligible amounts of TNF-alpha and IL-1beta were retrieved from the BALF of statically inflated lungs. The concentrations of TNF-alpha and IL-1beta were higher in the BALF of ventilated lungs (p < 0.001). The TNF-alpha level did not differ with the magnitude of VT, whereas the level of IL-1beta was significantly higher in BALF of lungs ventilated with 42 ml/kg VT (p < 0.01). The MIP-2 concentrations were similar for the two ventilatory conditions. These results suggest that ventilation that severely injures lungs does not lead to the release of significant amounts of TNF-alpha or IL-1beta by the lung in the absence of LPS challenge but may increase lung MIP-2 production.

Analysis of Variance↗
PubMed2001

[Prevention of nosocomial pneumonia in patients treated with invasive ventilation].

Nosocomial pneumonia is one of the primary causes of nosocomial infection in intensive care patients, leading to high mortality and prolonged hospitalization. Mechanical ventilation and its duration are major risk factors. When invasive ventilation is indispensable, preventive measures should aim at optimizing patient care by carefully applying basic rules of hygiene and recommended procedures for use of ventilation equipment. Different preventive measures have been proposed and should be considered in light of several criteria: the cost/benefit ratio, the level of proof (size of the study population, quality and pertinence of judgement criteria), feasibility, routine cost, and absence of secondary collateral adverse effects.

Antibiotic Prophylaxis↗
PubMed2000

Safety, efficacy, and cost-effectiveness of mechanical ventilation with humidifying filters changed every 48 hours: a prospective, randomized study.

OBJECTIVE: To determine whether three hydrophobic and hygroscopic heat and moisture exchangers (HMEs) retain their heating and humidifying properties (assessed by psychrometric measurements of absolute humidity, relative humidity, and tracheal temperature) for 48 hrs without any drop in their bacteriologic efficiency. DESIGN: Prospective randomized clinical trial. PATIENTS: Sixty-one consecutive unselected mechanically ventilated intensive care unit patients. INTERVENTIONS: Patients were randomly allocated to one of the three HMEs studied (Hygrobac-Dar from Mallinckrodt, n = 21; Humid-Vent from Gibeck, n = 20; and Clear-Thermal from Intersurgical, n = 20). MEASUREMENTS AND MAIN RESULTS: Hygrometric parameters were measured by psychrometry after 3, 24, and 48 hrs of use. Peak airway pressure was recorded every 6 hrs and averaged over 24 hrs. Bacterial colonization of both patients and circuits was studied. Patients in all three groups were similar in terms of age, indications for, and overall duration of mechanical ventilation. Tracheal tube occlusion never occurred. Hygrometric data included 371 measurements whereas bacteriologic data included >700 samples and cultures. The Hygrobac-Dar HMEs gave a significantly higher absolute humidity whatever the time of measurement (3, 24, or 48 hrs) than the other two HMEs (p < .001). The Clear-Thermal HMEs gave the poorest hygrometric parameters (p < .01); five of them were replaced prematurely (24 hrs) because the absolute humidity was <25 mg H2O/L. This did not occur for the other HMEs. Mean peak airway pressures were identical in the three groups. The bacterial colonizations of both patient and circuit were similar (and negligible for circuits) for all three groups. CONCLUSION: Some HMEs may be used safely for 48 hrs without change. However, this does not pertain to every brand of HME. Objective in vivo evaluation of their humidifying performances is decisive before extending their duration of use.

Acute Disease↗
PubMed2000

Ventilator circuit and secretion management strategies: a Franco-Canadian survey.

OBJECTIVE: To determine the use of ventilator circuit and secretion management strategies in France and Canada. DESIGN: Binational cross-sectional survey. POPULATION: Intensive care unit (ICU) directors in French and Canadian university hospitals. MEASUREMENTS: We compared responses between countries regarding the use of seven circuit and secretion strategies, the rationales against their use, decisional responsibility for these strategies, whether ventilator-associated pneumonia (VAP) practice was audited, and whether VAP prevention guidelines addressing these strategies were used. RESULTS: The response rate was 72/84 (85.7%) for French and 31/32 (96.9%) for Canadian ICUs. Endotracheal intubation was predominantly oral in both countries. Changing the ventilator circuits only for every new patient was more frequent in France than in Canada (p < .0001). Heated humidifiers were used more in Canada than France (p = .0003). Closed endotracheal suctioning was used more frequently in Canada (p < .0001). In both countries, subglottic secretion drainage and kinetic beds were rarely used. Semirecumbent positioning was reported more often by French than Canadian ICUs (p = .003). Reasons for nonuse of these strategies included adverse effects (heat and moisture exchangers), cost (kinetic beds), lack of convincing benefit (subglottic secretion drainage), and nurse inconvenience (semirecumbency). Decisional responsibility for each strategy differed among institutions. VAP prevention practice was periodically reviewed in 53% of French and 68% of Canadian ICUs (p = .20). VAP prevention guidelines were used in 64% and 30% of these ICUs, respectively (p = .002). CONCLUSIONS: Our study does not support the notion that published recommendations substantially impact reported use of several ventilator circuit and secretion management strategies. Based on the use of more frequent ventilator circuit changes, closed suctioning systems, heated humidifiers, and respiratory therapists, ventilator circuit and secretion management practice appears more costly in Canada than in France.

Canada↗
PubMed2000

Alveolar permeability and liquid absorption during partial liquid ventilation of rats with perflubron.

We examined the effect of instilled perflubron (LiquiVent) on the transport properties of alveolar epithelium in anesthetized rats. Krebs-Ringer bicarbonate (1 to 4 ml) containing (125)I-albumin, [(3)H]mannitol and [(14)C] sucrose was instilled into airspaces either alone (n = 29), or with 1 (n = 21) or 2 (n = 12) ml perflubron and sampled 30 min later. Absorption was deduced from the changes in (125)I-albumin activity per unit volume in the airspace instillate, and changes in [(3)H]mannitol and [(14)C]sucrose activity per unit volume were used to evaluate the passive permeability of the alveolar-airway barrier. The rate of Ringer absorption depended on the volume instilled [0.38 (ml/h)/ml Ringer]. Perflubron (1 or 2 ml) increased Ringer absorption by 0.26 (p < 0. 001) and 0.19 ml/h (p < 0.05), respectively. However, 2 ml perflubron increased absorption less than did the same additional volume of Ringer (p < 0.001). The passive permeability of the alveolar-airway barrier increased exponentially with instilled Ringer volume. Sucrose/mannitol size selectivity was lost when Ringer volume was > 2 ml and albumin leaked from airspaces when it was 4 ml. Instillation of 2 ml perflubron prevented this increase in permeability, but 1 ml did not. No albumin leaked with perflubron even when the total volume of liquid in airspaces (Ringer + perflubron) was > 4 ml. These results suggest that perflubron can be beneficial in pulmonary edema by redistributing the alveolar liquid over a larger surface area, thus accelerating resorption. In addition, larger doses of perflubron may better preserve epithelial permeability during alveolar flooding.

Absorption↗
PubMed2000

Efficiency and safety of mechanical ventilation with a heat and moisture exchanger changed only once a week.

The cost of mechanical ventilation (MV) is high. Efforts to reduce this cost, as long as they are not detrimental for the patients, are needed. MV with heat and moisture exchangers (HME) changed every 48 h is safe, efficient, and cost-effective. Preliminary reports suggest that the life span of these filters may be prolonged. We determined prospectively whether a hygroscopic and hydrophobic HME (Hygrobac-Dar; Mallinckrodt) provided safe and efficient heating and humidification of the inspired gases when changed only once a week. Patients who were considered to require mechanical ventilation for more than 48 h were included in the study. HMEs were initially set for 7 d. Efficient airway heating and humidification were assessed by clinical parameters (number of tracheal suctionings and instillations required, peak airway pressures) and hygrometric measurements performed by psychrometry. Resistance was measured from Day 0 to Day 7. Bacterial colonization of circuits and HMEs was studied. A total of 377 days of mechanical ventilation with 60 HMEs was studied. Clinical parameters and hygrometric measurements did not change between Day 0 and Day 7. Mean absolute humidity was 30.3 +/- 1.3 mg H(2)O/L on Day 0 and 30.8 +/- 1.5 mg H(2)O/L on Day 7 (p = 0.7). Endotracheal tube occlusion never occurred. Three HMEs were replaced prematurely because of insufficient absolute humidity. This rare event occurred only in patients with COPD and after the third day of use. In addition, the absolute humidity delivered by the HMEs was significantly lower in patients with COPD than in the rest of the population. Resistance did not change from Day 0 to Day 7 (2.4 +/- 0.3 versus 2.7 +/- 0.3 cm H(2)O/L/s; p = 0.4). Bacterial samples of both circuits and ventilator sides of HMEs were sterile in most cases. We conclude that mechanical ventilation can be safely conducted in non-COPD patients using an HME changed only once a week, leading to substantial cost savings (about $110,000 per year if these findings were applied to the university-affiliated hospitals in Paris).

Adult↗
PubMed1999

Bedside evaluation of efficient airway humidification during mechanical ventilation of the critically ill.

STUDY OBJECTIVE: To determine the correlation between simple rating of condensation seen in the flex-tube connecting the heating and humidifying device used with the endotracheal tube and hygrometric parameters (absolute and relative humidity and tracheal temperature) measured by psychrometry. DESIGN: Prospective randomized clinical trial. SETTING: Medical ICU of Louis Mourier Hospital, Colombes, France, a university-affiliated teaching hospital. PATIENTS: Forty-five consecutive mechanically ventilated critically ill patients. INTERVENTIONS: Patients undergoing mechanical ventilation were randomly assigned to receive humidification with one of the four heat and moisture exchangers (HMEs) tested or with a conventional heated humidifier. MEASUREMENTS: The hygrometric performances of four HMEs (BB2215, BB50, and BB100 from Pall Biomedical, Saint-Germaine-en-Laye, France; and Hygrobac-Dar from Mallinckrodt, Mirandola, Italy) and a heated humidifier (Fisher & Paykel; Auckland, New Zealand) were studied after 3 h and also after 48 h of use for the Hygrobac-Dar and correlated to a clinical visual inspection rating the amount of condensation in the flex-tube of the endotracheal tube. RESULTS: A total of 95 measurements in 45 patients were performed. The best hygrometric parameters were obtained with the heated humidifier (p < 0.001). The Hygrobac-Dar yielded significantly higher values for both humidities and tracheal temperature than the other three HMEs (p < 0.001). The performance of Hygrobac-Dar was unchanged after 48 h of use. There was a significant correlation between the condensation seen in the flex-tube and the hygrometric parameters measured by psychrometry (absolute humidity, rho = 0.7; relative humidity, rho = 0.7; tracheal temperature, rho = 0.5, p < 0.0001). CONCLUSION: In mechanically ventilated ICU patients, visual evaluation of the condensation in the flex-tube provides an estimation of the heating and humidifying efficacy of the heating and humidifying device used, thus allowing the clinician bedside monitoring of airway humidification.

Acute Disease↗