Eric Roupie

Effects of Positive End-expiratory Pressure and Different Tidal Volumes on Alveolar Recruitment and Hyperinflation

BackgroundThe 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 hav

Association between timing of intensive care unit admission and outcomes for emergency department patients with community-acquired pneumonia*

Objective:To compare the 28-day mortality and hospital length of stay of patients with community-acquired pneumonia who were transferred to an intensive care unit on the same day of emergency department presentation (direct-transfer patients) with those subsequently transferred within 3 days of presentation (delayed-transfer patients). Design:Secondary analysis of the original data from two North American and two European prospective, multicenter, cohort studies of adult patients with community-acquired pneumonia. Patients:In all, 453 non-institutionalized patients transferred within 3 days of emergency department presentation to an intensive care unit were included in the analysis. Supplementary analysis was restricted to patients without an obvious indication for immediate transfer to an intensive care unit. Interventions:None. Measurements and Main Results:The sample consisted of 138 delayed-transfer and 315 direct-transfer patients, among whom 150 (33.1%) were considered to have an obvious indication for immediate intensive care unit admission. After adjusting for the quintile of propensity score, delayed intensive care unit transfer was associated with an increased odds ratio for 28-day mortality (2.07; 95% confidence interval, 1.12–3.85) and a decreased odds ratio for discharge from hospital for survivors (0.53; 95% confidence interval, 0.39–0.71). In a propensity-matched analysis, delayed-transfer patients had a higher 28-day mortality rate (23.4% vs. 11.7%; p = 0.02) and a longer median hospital length of stay (13 days vs. 7 days; p < .001) than direct-transfer patients. Similar results were found after excluding the 150 patients with an obvious indication for immediate intensive care unit admission. Conclusions:Our findings suggest that some patients without major criteria for severe community-acquired pneumonia, according to the recent Infectious Diseases Society of America/American Thoracic Society consensus guideline, may benefit from direct transfer to the intensive care unit. Further studies are needed to prospectively identify patients who may benefit from direct intensive care unit admission despite a lack of major severity criteria for community-acquired pneumonia based on the current guidelines.

Frequency of bacteremia associated with transesophageal echocardiography in intensive care unit patients: a prospective study of 139 patients.

OBJECTIVE To determine the occurrence rate of bacteremia associated with transesophageal echocardiography in intensive care unit (ICU) patients. DESIGN A prospective study of 139 patients undergoing transesophageal echocardiography. SETTING The medical ICU of a tertiary referral teaching hospital. PATIENTS One hundred thirty-nine ICU patients (mean age 58 yrs) who underwent transesophageal echocardiography. INTERVENTIONS Blood samples were systematically drawn for aerobic and anaerobic culture at the following times: before (blood culture 1), at the end of (blood culture 2), and 30 mins after (blood culture 3) transesophageal echocardiography examinations. MEASUREMENTS AND MAIN RESULTS The mean duration of transesophageal echocardiography was 35 mins (range 7 to 120). One hundred thirty-four patients received mechanical ventilation; 125 patients had a nasogastric tube. Fifty-one patients had one or more underlying conditions that usually justify antimicrobial prophylaxis of bacterial endocarditis before high-risk procedures. Fifty-six patients did not receive any antibiotic treatment at the time of transesophageal echocardiography. In 114 patients, the three blood cultures were negative. In six patients, transesophageal echocardiography was performed during a preexisting bacteremia. A contamination (only one positive blood culture of the three sampling times) with coagulase-negative staphylococci occurred in four patients at blood culture 1, five patients at blood culture 2, and six patients at blood culture 3. Contamination with Corynebacterium species occurred in two patients at blood culture 2. In one patient receiving cefotaxime and netilmicin, blood culture 1 was sterile and blood cultures 2 and 3 yielded coagulase-negative staphylococci. In one patient receiving no antibiotic treatment, blood culture 1 was sterile and blood cultures 2 and 3 yielded Enterococcus faecalis. None of these two patients received a specific antibiotic treatment or developed any secondary septic focus. CONCLUSIONS The overall frequency of bacteremia induced by transesophageal echocardiography in ICU patients was 1.4% (two of 139 patients) (95% confidence interval 0.2% to 5.1%). The frequency did not differ whether patients received antibiotics before transesophageal echocardiography (one [1.2%] of 83 patients) or not (one [1.8%] of 56 patients) (p = .96). Therefore, routine antimicrobial prophylaxis does not appear justified before transesophageal echocardiography in ICU patients.

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 end-expiratory pressure promotes alveolar recruitment; increasing Vt above the UIP seems to predominantly increase hyperinflation.

Has Prognosis of ARDS Improved

Recently, Milberg et al. 1 reported that, in their institution (five ICUs at Harborview Medical Center, Seattle), mortality of acute respiratory distress syndrome (ARDS) patients had steadily declined from 67% in 1983 to 40% in 1993, and even less in the following year. This information was well received, since many other studies supported such a trend, for a syndrome in which mortality is usually reported as high as 70 or 80%. Indeed, mortality was 54% in a paper by Sloane et al. 2, 53% by Suchyta et al. 3, or, even lower, 12% by Stocker 4 and 20% by Lewandowski 5. However, when Kraft et al. 6 plotted mortality over time of published series of ARDS selected after a comprehensive search, between 1967 and 1994, they could not find a trend toward improvement (Figure 1). The reasons for such opposed views rely in fact on the heterogeneity of published series, in terms of case mix, ICU structure, definition of ARDS, scoring, cutoffs, end points, etc. Open image in new window Figure 1. Percent survival of the various etiologie of 583 ARDS patients after 60 days. A, aspiration; B, extraabdominal infection; C, intraabdominal infection; D, miscellaneous; E, opportunistic pneumonia; F , pneumonia; G, trauma. *p < 0.0001.

Mechanical Ventilation for Ards: Should we Reduce Tidal Volume?

For the last ten years, barotrauma has been proposed as a major cause for our failure in salvaging patiens having the Acute Respiratory Distress Syndrome (ARDS). After the first descriptions1,2 of cysts, bullae and emphysematous-like lesions supposedly caused by mechanical ventilation, many authors related the incidence and severity of barotrauma -not only overdistension of airspaces, but also pneumothoraces- to the usual modalities of mechanical ventilation: large tidal volumes (Vt), equal or higher than 12 mL/kg of body weight, and/or high levels of positive end expiratory pressure (PEEP)3,4. Dreyfuss and Saumon in a series of elegant studies, showed that the main determinant of alveolar damage — measured as capillary permeability increase- was in fact the end inspiratory lung volume 5. In the clinical arena, end inspiratory volume can only be approximated as the airway pressure measured at the end of an end inspiratory plateau, during a zero flow period.