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Intensive Care Med (2006) 32:1329–1335 DOI 10.1007/s00134-006-0241-3

Ralf-Peter Vonberg Tim Eckmanns Tobias Welte Petra Gastmeier

Received: 16 December 2005 Accepted: 17 May 2006 Published online: 21 June 2006 © Springer-Verlag 2006 R.-P. Vonberg (u) · P. Gastmeier Medical School of Hannover, Institute for Medical Microbiology and Hospital Epidemiology, Carl-Neuberg-Straße 1, 30625 Hannover, Germany e-mail: Vonberg.Ralf@MH-Hannover.de Tel.: +49-511-5324431 Fax: +49-511-5328174 T. Eckmanns Charité University Medicine, Institute of Hygiene and Environmental Medicine, Berlin, Germany T. Welte Medical School of Hannover, Department for Pneumology, Carl-Neuberg-Straße 1, 30625 Hannover, Germany

ORIGINAL

Impact of the suctioning system (open vs. closed) on the incidence of ventilation-associated pneumonia: meta-analysis of randomized controlled trials

Abstract Objective: Ventilationassociated pneumonia (VAP) is a serious complication of patients in intensive care units (ICU) who require mechanical ventilation. The choice of suctioning system (open vs. closed) remains unresolved in evidence-based guidelines. This meta-analysis was carried out to analyze the effect of the type of suctioning system on the incidence of VAP. Design: A search of the literature was used to identify randomized controlled trials addressing this question. A meta-analysis was then performed to calculate the relative risk of ventilation-associated pneumonia acquisition with the two suctioning systems. Results: Nine trials were included, with 648 patients in the open suctioning group and 644 in the closed suctioning group. VAP occurred in 128 (20%) of the

Introduction Pneumonia is the most common nosocomial infection on intensive care units (ICUs) [1], and mechanical ventilation is a well known risk factor for acquiring nosocomial pneumonia [2]. Consequences of ventilation-associated nosocomial pneumonia are an increased length of ICU stay for more than 6 days, increased cost for health care systems by U.S.$10,000 per case, and a doubled risk of mortality of affected patients [3]. Two general types of suctioning systems are available: (a) open tracheal suctioning systems that need to become disconnected. These systems require single-use catheters and a sterile suctioning technique for the prevention of ventilation-associated pneumonia (VAP). (b) Closed tracheal suctioning systems

open suctioning group and in 120 (19%) in the closed suctioning group (relative risk 0.95). Conclusions: At a given pneumonia prevalence of 20% in ICU patients there was no significant advantage for the use of either suctioning system in this meta-analysis. The choice of suctioning system should therefore be based on handling, cost, and individual patient’s disease until more data are available. Keywords Suctioning systems · Meta-analysis · Nosocomial pneumonia

that do not become disconnected but rather involve use of multiuse catheters. Evidence-based guidelines for preventing nosocomial pneumonia have been published by the Centers of Disease Control and Prevention, but so far the relationship between VAP and the type of endotracheal suctioning system remains unresolved [4]. During use open systems may allow external pathogens to enter the patient’s airways, but frequent reuse of contaminated closed systems may also present some risk of infection. The effect of endotracheal suction system (open vs. closed) on the rate of VAP has been reviewed by several authors [5, 6, 7, 8], who have analyzed, however, only few randomized controlled trials (RCTs) among those available at present. These authors failed to ascertain any significant difference in the development of nosocomial pneu-


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monia with the two suctioning systems. Meanwhile additional RCTs addressing this question have been published. This meta-analysis was carried out to analyze the effect of the type of suctioning system on the incidence of VAP, including all the RCTs performed in adults available at present.

patient’s suctioning system was not changed at all unless it presented mechanical failure, or soiling, or the patient needed reintubation. In all other studies the closed suctioning system was exchanged every 24 h. The number of suctioning procedures as described by the authors often covers the routine suctioning management only. Additional procedures might have been performed by the discretion of the health care worker. No significant differences in the severity of the underlying disease were Materials and methods reported in either study. Definitions used for pneumoData acquisition nia determination in most studies were similar to the definitions as proposed by Centers of Disease Control Studies eligible for inclusion were found by a PubMed and Prevention. No patients became excluded after the search (from 1966 to 10 April 2006) using the fol- randomization process. lowing terms: (a) “randomized” or “randomised,” (b) “prospective,” (c) “open,” (d) “closed,” (e) “suctioning” or “suction,” (f) “tracheal” or “endotracheal”, and (g) “pneumonia.” All studies were then screened whether all Results of the following criteria were fulfilled: (a) reporting of the Risk of ventilation-associated pneumonia number of patients with open and with closed suctioning systems, (b) reporting of the number of VAP cases that A total of 648 patients were treated with open suctioning occurred in each group, (c) published as full manuscript. systems, 20% of whom acquired VAP, and 644 with Reference lists of all of these articles were searched for a closed system, 19% of whom acquired VAP. No study additional RCTs. Using the key words (a) “open,” (b) reported significant differences between the groups with “closed,” and (c) “suctioning” or “suction” the Cochrane respect to histamine-2 receptor antagonists, gastric acid Central Register of Controlled Trials was also searched to secretion inhibitors, patient’s tobacco use, or prevalence detect additional RCTs. of chronic obstructive lung disease. The pooled relative risk for closed suctioning systems is 0.95 (95% CI 0.76–1.18). The study by Adams et al. [14] is excluded Data analysis in this calculation as neither arm of the study contains any events. The test for statistical heterogenicity is not Data were extracted independently by all authors. The significant (p = 0.46), which means that there is only fixed-effects method was used to derive a summary very little heterogenicity between the studies. Figure 1 estimation as implemented in STATA 7 software (STATA shows the corresponding Forrest plot. Studies with smaller Statistics/Data Analysis 7.0, Stata, Texas, USA). Pro- population sizes have a relative risk less than 1 while tective effects with the 95% confidence interval were the study with the greatest number of patients shows one calculated, and testing for heterogenicity was performed. greater than 1. The overall relative risk is slightly below 1. Study characteristics A total of 12 citations were found by the PubMed search using the key words as described. One of these hits was of only preliminary data [9]. This study was published in full article form 2 years later. Two other references were excluded because they either failed to report data on pneumonia but concentrated on other cardiorespiratory parameters instead [10] or were conducted in premature infants [11]. The remaining nine studies [12, 13, 14, 15, 16, 17, 18, 19, 20] were included in this meta-analysis. The Cochrane Central Register of Controlled Trials revealed a protocol for this subject only, but no Cochrane review on this issue has been published yet [21]. Table 1 shows the characteristics of all studies included. In two studies [14, 18] no exact use interval of the closed Fig. 1 Forrest plot of meta-analysis (study by Adams et al. [14] is suctioning system was reported. In one study [20] the excluded)


Trauma (35)

Liver Trach transCare plant (20)

Johnson USA et al. [13]

Adams UK et al. [14]

Trach Care

Trach Care

Surgical (41), medical (43)

Deppe USA et al. [12]

Type of closed suctioning system

Type of ICU (no. of patients)

Country

ND

24

24

Hours of closed system use

Yes

Yes

Yes

Pneumonia at admission excluded

o: 10.0, c: 16.6

o: 16, c: 16

o: 12.4, c: 16.6

All of the following criteria must apply within 24 h: purulent sputum, temperature: ≥ 38.1◦ C or ≤ 35.9◦ C, new or progressive infiltrate in radiograph, leukocytes: > 12,000/mm3 or < 3,000/mm3 , time after admission > 48 h New or progressive pulmonary infiltrate in radiograph and at least two of the following criteria must apply: purulent sputum, temperature: ≥ 38.1◦ C without any known extrapulmonary source, leukocytes: > 12,000/mm3 Clinical pulmonary infection criteria (point score): temperature: 36.5–38.4◦ C (0 points), temperature: 38.5–39.0◦ C (1 point), temperature: < 36.0◦ C or > 39.0◦ C (2 points), leukocytes: 4,000–11,000/mm3 (0 points), leukocytes: 11,000–17,000/mm3 (1 point), leukocytes: > 17,000/mm3 (2 points), secretions: ± (0 points), secretions: + (1 point), secretions: ++ (2 points), PaO2 y/FIO2 Y inkPa: > 33 (0 points), PaO2 y/FIO2 Y inkPa: < 33 (2 points), PaO2 y/FIO2 Y inkPa: < 33 with ARDS (0 points), chest radiograph infiltrates: clear (0 points), chest radiograph infiltrates: patchy (1 point), chest radiograph infiltrates: localized (2 points), a sum score of at least 6 points and at least two of the following criteria must apply or alternatively a sum score of at least 8 points and at least one of the following criteria must apply: clinical course on/off antibiotics consistent with pneumonia, lack of evidence of alternative source of sepsis, lung biopsy or postmortem histology demonstrating pneumonia

No. of open Criteria for diagnosis nosocomial of ventilationand closed associated pneumonia suctioning procedures per day

Child-Pugh score (no. of patients): o: A (2), B (7), C (1), c: A (3), B (7), C (0)

Average APACHE score: o: 12, c: 12

Medical ICU: average APACHE II score of all patients: 25.1; surgical ICU: ND

Severity of illness

ND

ND

ND

Average no. of days of mechanical ventilation

Table 1 Characteristics of included studies of endotracheal suctioning (open vs. closed) (o open, c closed CFU colony forming units, APACHE Acute Physiology and Chronic Health Evaluation, SAPS Simplified Acute Physiology Score, ND no data)

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Medical- ND surgical (47)

Zeitoun Brazil et al. [16]

Trach Care

SteriCath

Rabitsch Austria Medical et al. [17] (24)

Medical (78)

Medical- Hisurgical Care (443)

Topeli Turkey et al. [18]

Lorente Spain et al. [19]

SteriCath

Neurosurgical (104)

Combes France et al. 2000 [15]

Type of closed suctioning system

Type of ICU (no. of patients)

Country

Table 1 Continued

24

ND

24

24

24

Hours of closed system use

Yes

Yes

Yes

Yes

Yes

o: 8.3, c: 8.1

ND

o: ≥ 6, c: ≥ 6

ND

o: 12, c: 12

All of the following criteria must apply: purulent endotracheal secretions, temperature: ≥ 38◦ C without any known extrapulmonary source, new and persistent infiltrate in radiograph leukocytes: > 10,000/mm3 or < 4,000/mm3 , time after beginning of ventilation > 48 h All of the following criteria must apply: purulent tracheobronchial secretions or changes in characteristics, temperature: ≥ 37.8◦ C, new or progressive infiltrate in radiograph, leukocytes: > 10,000/mm3 New or progressive pulmonary infiltrate in radiograph and at least one of thefollowing criteria must apply: radiographic evidence of cavitation, histological evidence of pneumonia, positive blood culture without another source evidence of infection, purulent tracheal aspirate (> 25 leukocytes per field), positive pleural fluid culture finding and one of the following criteria: (a) temperature: > 38.0◦ C, (b) leukocytes: > 10,0000/mm3 or < 3,000/mm3 New and persistent pulmonary infiltrate in radiograph and at least two of the following criteria must apply: temperature: > 38◦ C or < 35.5◦ C, leukocytes: > 10,000/mm3 or < 3,000/mm3 , purulent enodotracheal aspirate (≥ 10 leukocytes per field), time after beginning of ventilation > 48 h All of the following criteria must apply: new onset of purulent bronchial sputum, temperature: > 38◦ C or < 35.5◦ C, leukocytes: > 10,000/mm3 or < 4,000/mm3 , new and persistent infiltrate in radiograph, time after beginning of ventilation > 24 h, one of following “significant respiratory secretions”: tracheal aspirate: > 106 CFU/ml, bronchoalveolar aspirate: > 104 CFU/ml, protected brush catheter: > 103 CFU/ml, (if the CFU count was too low, a positive blood culture coinciding was required to fulfill this criterion)

Pneumonia No. of open Criteria for diagnosis nosocomial of ventilationat admisand closed associated pneumonia sion exsuctioning cluded procedures per day o: 14.1, c: 12.8

Average no. of days of mechanical ventilation

ND

Average APACHE II o: 12.7, score: c: 12.5 o: 15.8, c: 15.4

Average APACHE II o: 7.5, score: c: 8.2 o: 23.8, c: 25.6

APACHE II score did not differ between groups

Median APACHE II ND scores (no significant difference): o: 24, c: 22

Average SAPS I score: o: 6.91, c: 7.88

Severity of illness

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Medical- Hisurgical Care (457)

No routine change

Yes

o: 7.9, c: 8.1

All of the following criteria must apply: new onset of purulent bronchial sputum, temperature: > 38◦ C or < 35.5◦ C, leukocytes: > 10,000/mm3 or < 4,000/mm3 , new or progressive infiltrate in radiograph, onset of symptoms associated with mechanical ventilation; one of following “significant respiratory secretions”: tracheal aspirate: > 106 CFU/ml, bronchoalveolar aspirate: > 104 CFU/ml, protected brush catheter: > 103 CFU/ml, (if the CFU count was too low, a positive blood culture coinciding was required to fulfill this criterion)

Average APACHE II score: o: 13.7, c: 13.8

o: 9.9, c: 9.5

Discussion

Lorente Spain et al. [20]

Country

Table 1 Continued

Type of ICU (no. of patients)

Type of closed suctioning system

Hours of closed system use

Pneumonia at admission excluded

No. of open Criteria for diagnosis nosocomial of ventilationand closed associated pneumonia suctioning procedures per day

Severity of illness

Average no. of days of mechanical ventilation

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Closed suctioning systems encompass some advantages in handling compared to open systems. When closed systems are in use, mechanical ventilation may be continued without interruption, positive end-expiratory pressure may be maintained [22, 23], and the risk of infection for medical staff (e.g., by Mycobacterium tuberculosis positive patients) is reduced [24]. In addition, the risk of introducing new pathogens from external sources into the patient’s respiratory system is minimized with closed systems because the system is disconnected only once a day or less. On the other hand, open suctioning systems use a new and sterile catheter each time while the catheter of the closed system is reused several times within the 24-h period of use. One may speculate that contaminating bacteria from previous suction procedures would multiply on contaminated catheters of closed suctioning systems over time. The question of whether prolonged use of closed suctioning systems leads to significant growth of bacteria on the catheter over longer periods that are introduced in the patient’s respiratory system at later suctioning procedures is controversial; hence the importance of contamination of closed suctioning system remains unclear. We found evidence that bacterial growth on the catheter surface occurs [25] while others studies have not reported increased numbers of pathogens [26]. To our knowledge there is as yet only a single RCT that has compared different use periods of closed suctioning systems with respect to the outcome of VAP [27]. Unfortunately, only two of the studies included in this meta-analysis stated explicitly that the specimens for microbiological testing were taken by a new and sterile closed suction system to exclude a possible bias for subsequent diagnosis of pneumonia [12, 14]. Therefore it remains unknown how many false-positive respiratory tract infections were diagnosed among patients with closed suctioning systems in the other studies due to heavy tracheal secrete contamination from reused catheters. Nine studies were included in our analysis, and only one of these reported a significant result (in favor of the closed suctioning system) [17]. In this study the endotracheal tube inserted initially was replaced after 12 h of use by a different kind of endotracheal tube to determine microbiological cross-contamination due to previous incorrect tube placement or lack of maintenance of tube positioning. However, tubes were replaced in both patient groups (open and closed suctioning) and therefore is unlikely to have had an impact on this outcome of VAP [17]. None of the patients included in this meta-analysis had symptoms of respiratory tract infection at the time of admission, and criteria for the definition of later pneumonia differed only marginal between the studies. The exact number of suctioning procedures cannot be evaluated because this was performed when “needed clinically” in addition to a designated regime in most


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Table 2 Relative risk (RR) of ventilation-associated pneumonia in different suctioning systems: total no./no. with pneumonia (%)

Deppe et al. [12] Johnson et al. [13] Adams et al. [14] Combes et al. [15] Zeitoun et al. [16] Rabitsch et al. [17] Topeli et al. [18] Lorente et al. [19] Lorente et al. [20] Total a DerSimoniand–Laird

Open

Close

RR

95% CI

11/38 (29%) 10/19 (53%) 0/10 (0%) 9/54 (17%) 11/24 (46%) 5/12 (42%) 9/37 (24%) 42/233 (18%) 31/221 (14%) 128/648 (20%)

12/46 (26%) 8/16 (50%) 0/10 (0%) 4/50 (8%) 7/23 (30%) 0/12 (0%) 13/41 (32%) 43/210 (20%) 33/236 (14%) 120/644 (19%)

0.90 0.95 (Undefined) 0.48 0.66 0.09 1.30 1.14 1.00 0.95a

0.45–1.81 0.50–1.82 – 0.16–1.46 0.31–1.41 0.006–1.48 0.63–2.69 0.78–1.66 0.64–1.58 0.76–1.18

method for pooled relative risks ([14] is excluded)

studies. As shown in Table 1, the patients included in different studies were cared for in different kinds of ICUs such as medical, surgical, trauma, or neurosurgical. This may contribute to the range of infection rates that has been reported, for example, from the German Nosocomial Infections Surveillance Systems (for reference data see http://www.nrz-hygiene.de/dwnld/referenz_its_.pdf). In addition, there is also wide variance in VAP rates even within the single kinds of ICU. Because the majority of studies did not show significant results by themselves, we believe that major publication bias seems less likely in our analysis, although the funnel plot revealed publication bias to some extent (data not shown). As with most single observation studies, this meta-analysis also failed to ascertain a significant advantage of either suctioning system. However, one must bear in mind that these results are based on 1,292 patients. At a VAP incidence of 20% we would only have been able to detect a significant reduction in the relative risk of at least 27%, but the true potential of pneumonia prevention by one specific system may be less than this and could become evident if data on more patients become available. Until then the choice of suctioning system should be based on convenience in handling, cost-effectiveness, and the individual patient’s disease. Further studies with greater numbers of patients are needed to determine whether the choice of suctioning system affects the rate of nosocomial pneumonia at a relative risk reduction of less than 27%. Whether ecological (waste) and economical (cost) evaluation favors one system or the other depends principally upon the frequency of suctioning processes of

open systems and length of periods that closed systems are used [7, 11, 13, 19, 28, 29]. The maximum period that closed systems can be used safely is not yet known, although there is accumulating evidence that they may not need to be changed routinely [7]. Kollef et al. [27] reported that there was no increased risk of pneumonia (relative risk 0.99, 95% CI 0.66–1.50) in ventilated patients if closed suctioning systems are not changed at all during patient’s ICU stay unless clinically indicated. This reduced the cost of the closed suctioning system from U.S.$11,016 (routine changes in the in-line suctioning system; 263 patients) to U.S.$837 (no routine changes; 258 patients) [27]. Recent cost calculations by Lorente et al. [20] reveal cost-effectiveness for closed suctioning systems that are not changed regularly as soon as the time of the patient’s mechanical ventilation exceeds 4 days. One major benefit of closed suction catheters may be a decreased bacterial contamination of caregivers. This factor cannot be investigated in a RCT design. This is why additional trials should be carried out using closed suctioning systems only and comparing the rate of nosocomial pneumonia before and after. This would exclude possible contamination of health care worker’s hands due to intermittent open suctioning of other patients. Although there is little benefit for the individual patient, there might be some potential to reduce the burden of bacterial transmission by using closed suctioning systems. This could be of importance particularly if there is a high prevalence of multidrug resistant pathogens such as methicillin-resistant Staphylococcus aureus and other multiresistant Gram-negative bacteria.

References 1. Centers for Disease Control and Prevention (2004) National Nosocomial Infections Surveillance (NNIS) System Report, data summary from January 1992 through June 2004, issued October 2004. Am J Infect Control 32:470–485

2. Tejada AA, Bello DS, Chacon VE, Munoz MJ, Villuendas Uson MC, Figueras P, Suarez FJ, Hernandez A (2001) Risk factors for nosocomial pneumonia in critically ill trauma patients. Crit Care Med 29:304–309

3. Safdar N, Dezfulian C, Collard HR, Saint S (2005) Clinical and economic consequences of ventilator-associated pneumonia: a systematic review. Crit Care Med 33:2184–2193


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4. Tablan OC, Anderson LJ, Besser R, Bridges C, Hajjeh R (2004) Guidelines for preventing health-care-associated pneumonia, 2003: recommendations of CDC and the Healthcare Infection Control Practices Advisory Committee. MMWR Recomm Rep 53:1–36 5. Cook D, De Jonghe B, Brochard L, Brun-Buisson C (1998) Influence of airway management on ventilatorassociated pneumonia: evidence from randomized trials. JAMA 279:781–787 6. Dodek P, Keenan S, Cook D, Heyland D, Jacka M, Hand L, Muscedere J, Foster D, Mehta N, Hall R, BrunBuisson C (2004) Evidence-based clinical practice guideline for the prevention of ventilator-associated pneumonia. Ann Intern Med 141:305–313 7. Hess DR, Kallstrom TJ, Mottram CD, Myers TR, Sorenson HM, Vines DL (2003) Care of the ventilator circuit and its relation to ventilator-associated pneumonia. Respir Care 48:869–879 8. Branson RD (2005) The ventilator circuit and ventilator-associated pneumonia. Respir Care 50:774–785 9. Zeitoun SS, de Barros AL, Diccini S, Juliano Y (2001) Incidence of ventilator-associated pneumonia in patients using open-suction systems and closed-suction systems: a prospective study—preliminary data. Rev Lat Am Enfermagem 9:46–52 10. Lee CK, Ng KS, Tan SG, Ang R (2001) Effect of different endotracheal suctioning systems on cardiorespiratory parameters of ventilated patients. Ann Acad Med Singapore 30:239–244 11. Cordero L, Sananes M, Ayers LW (2000) Comparison of a closed (Trach Care MAC) with an open endotracheal suction system in small premature infants. J Perinatol 20:151–156 12. Deppe SA, Kelly JW, Thoi LL, Chudy JH, Longfield RN, Ducey JP, Truwit CL, Antopol MR (1990) Incidence of colonization, nosocomial pneumonia, and mortality in critically ill patients using a Trach Care closedsuction system versus an open-suction system: prospective, randomized study. Crit Care Med 18:1389–1393

13. Johnson KL, Kearney PA, Johnson SB, Niblett JB, MacMillan NL, McClain RE (1994) Closed versus open endotracheal suctioning: costs and physiologic consequences. Crit Care Med 22:658–666 14. Adams DH, Hughes M, Elliott TS (1997) Microbial colonization of closed-system suction catheters used in liver transplant patients. Intensive Crit Care Nurs 13:72–76 15. Combes P, Fauvage B, Oleyer C (2000) Nosocomial pneumonia in mechanically ventilated patients, a prospective randomised evaluation of the Stericath closed suctioning system. Intensive Care Med 26:878–882 16. Zeitoun SS, de Barros AL, Diccini S (2003) A prospective, randomized study of ventilator-associated pneumonia in patients using a closed vs. open suction system. J Clin Nurs 12:484–489 17. Rabitsch W, Kostler WJ, Fiebiger W, Dielacher C, Losert H, Sherif C, Staudinger T, Seper E, Koller W, Daxbock F, Schuster E, Knobl P, Burgmann H, Frass M (2004) Closed suctioning system reduces crosscontamination between bronchial system and gastric juices. Anesth Analg 99:886–892 18. Topeli A, Harmanci A, Cetinkaya Y, Akdeniz S, Unal S (2004) Comparison of the effect of closed versus open endotracheal suction systems on the development of ventilator-associated pneumonia. J Hosp Infect 58:14–19 19. Lorente L, Lecuona M, Martin MM, Garcia C, Mora ML, Sierra A (2005) Ventilator-associated pneumonia using a closed versus an open tracheal suction system. Crit Care Med 33:115–119 20. Lorente L, Lecuona M, Jimenez A, Mora ML, Sierra A (2006) Tracheal suction by closed system without daily change versus open system. Intensive Care Med 32:538–544 21. Subirana M, Sola I, Garcia JM, Laffaire E, Benito S (2003) Closed tracheal suction systems versus open tracheal systems for mechanically ventilated adult patients. The Cochrane Database of Systematic Reviews: protocols 2003 3

22. Cereda M, Villa F, Colombo E, Greco G, Nacoti M, Pesenti A (2001) Closed system endotracheal suctioning maintains lung volume during volumecontrolled mechanical ventilation. Intensive Care Med 27:648–654 23. Maggiore SM, Lellouche F, Pigeot J, Taille S, Deye N, Durrmeyer X, Richard JC, Mancebo J, Lemaire F, Brochard L (2003) Prevention of endotracheal suctioning-induced alveolar derecruitment in acute lung injury. Am J Respir Crit Care Med 167:1215–1224 24. Cobley M, Atkins M, Jones PL (1991) Environmental contamination during tracheal suction. A comparison of disposable conventional catheters with a multiple-use closed system device. Anaesthesia 46:957–961 25. Freytag CC, Thies FL, Konig W, Welte T (2003) Prolonged application of closed in-line suction catheters increases microbial colonization of the lower respiratory tract and bacterial growth on catheter surface. Infection 31:31–37 26. Ritz R, Scott LR, Coyle MB, Pierson DJ (1986) Contamination of a multiple-use suction catheter in a closed-circuit system compared to contamination of a disposable, single-use suction catheter. Respir Care 31:1086–1091 27. Kollef MH, Prentice D, Shapiro SD, Fraser VJ, Silver P, Trovillion E, Weilitz P, Von Harz B, St John R (1997) Mechanical ventilation with or without daily changes of in-line suction catheters. Am J Respir Crit Care Med 156:466–472 28. DePew CL, Moseley MJ, Clark EG, Morales CC (1994) Open vs closedsystem endotracheal suctioning: a cost comparison. Crit Care Nurs 14:94–100 29. Maggiore SM (2006) Endotracheal suctioning, ventilator-associated pneumonia, and costs: open or closed issue? Intensive Care Med 32:485–487

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