Care of the Ventilator Circuit & Ventilator-Associated Pneumonia PDF (2003)

AARC Evidence-Based Clinical Practice Guidelines Care of the Ventilator Circuit and Its Relation to Ventilator-Associated Pneumonia Summary of Recommendations • Ventilator circuits should not be changed routinely for infection control purposes. The maximum duration of time that circuits can be used...

AARC Evidence-Based Clinical Practice Guidelines Care of the Ventilator Circuit and Its Relation to Ventilator-Associated Pneumonia Summary of Recommendations • Ventilator circuits should not be changed routinely for infection control purposes. The maximum duration of time that circuits can be used safely is unknown. • Evidence is lacking related to ventilator-associated pneumonia (VAP) and issues of heated versus unheated circuits, type of heated humidifier, method for filling the humidifier, and technique for clearing condensate from the ventilator circuit. • Although the available evidence suggests a lower VAP rate with passive humidification than with active humidification, other issues related to the use of passive humidifiers (resistance, dead space volume, airway occlusion risk) preclude a recommendation for the general use of passive humidifiers. • Passive humidifiers do not need to be changed daily for reasons of infection control or technical performance. They can be safely used for at least 48 hours, and with some patient populations some devices may be able to be used for periods of up to 1 week. • The use of closed suction catheters should be considered part of a VAP prevention strategy, and they do not need to be changed daily for infection control purposes. The maximum duration of time that closed suction catheters can be used safely is unknown. • Clinicians caring for mechanically ventilated patients should be aware of risk factors for VAP (eg, nebulizer therapy, manual ventilation, and patient transport). [Respir Care 2003;48(9):869 – 879. © 2003 Daedalus Enterprises] Introduction A concern related to the care of the mechanically ventilated patient is the development of VAP. For many years this concern focused on the ventilator circuit and humidifier. Accordingly, the circuit and humidifier have been changed on a regular basis in an attempt to decrease the VAP rate. However, as the evidence evolved, it became apparent that the origin of VAP is more likely from sites other than the ventilator circuit,1,2 and thus the prevailing practice has become one of changing circuits less frequently.3 If this practice is safe, it will offer substantial cost savings. Other issues related to the components of the circuit and VAP have also become more important recently. For example, humidification systems can be either Principal author: Dean R Hess PhD RRT FAARC. Writing committee: Thomas J Kallstrom RRT FAARC, Carl D Mottram RRT FAARC, Timothy R Myers RRT-NPS, Helen M Sorenson MA RRT FAARC, and David L Vines MHS RRT. Correspondence: Dean R Hess PhD RRT FAARC, Respiratory Care, Ellison 401, Massachusetts General Hospital, 55 Fruit Street, Boston MA 02114. E-mail: [email protected]. RESPIRATORY CARE • SEPTEMBER 2003 VOL 48 NO 9 active or passive. Increasingly, inline suction is used, and this becomes part of the ventilator circuit. A systematic review of the literature was conducted with the intention of making recommendations for change frequency of the ventilator circuit and additional components of the circuit. Specifically, the Writing Committee wrote these evidence-based clinical practice guidelines to address the following questions: 1. Do ventilator circuits need to be changed at regular intervals: a. For infection control purposes? b. Because of deterioration in performance? 2. What is the economic impact of decreasing the frequency of ventilator circuit changes? 3. What are the issues related to circuit type? a. Disposable versus reusable b. Cleaning techniques c. Site of care (acute care, long-term care, home care) 4. Does the choice of active versus passive humidification affect ventilator circuit change frequency? 5. Do passive humidifiers need to be changed at regular intervals: a. For infection control purposes? b. Because of deterioration in performance? 869 EVIDENCE-BASED GUIDELINE: CARE 6. Do in-line suction catheters need to be changed at regular intervals: a. For infection control purposes? b. Because of deterioration in performance? 7. Are there specific populations for which the recommendations should be altered? a. Differences for age groups (neonatal, pediatric, adult) b. Differences for site of care (acute care, long-term care, home care) c. Differences for categories of patients (immunocompromised, burn) Methods OF THE VENTILATOR CIRCUIT Level 4: Observational study with a historical control group Level 5: Bench study, animal study, case series The critique forms were submitted to the principal author of the guideline (DRH), who transferred the information into evidence tables and conducted appropriate statistical analysis. Quantitative analysis consisted of meta-analysis and petograms. Statistical analysis was conducted using RevMan software (RevMan Analyses, Version 1.0 for Windows, in Review Manager [RevMan] 4.2, Oxford, England: The Cochrane Collaboration, 2003). Relative risk was calculated using a random effect model. P ⬍ 0.05 was considered statistically significant. Following a systematic review of the literature, recommendations were drafted by the Writing Committee and assigned one of the following grades, based on the strength of the evidence: Grade A: Scientific evidence provided by randomized, well-designed, well-conducted, controlled trials with statistically significant results that consistently support the guideline recommendation; supported by Level 1 or 2 evidence Grade B: Scientific evidence provided by well-designed, well-conducted observational studies with statistically significant results that consistently support the guideline recommendation; supported by Level 3 or 4 evidence Grade C: Scientific evidence from bench studies, animal studies, case studies; supported by Level 5 evidence Grade D: Expert opinion provides the basis for the guideline recommendation, but scientific evidence either provided inconsistent results or was lacking The draft document was then reviewed by experts on ventilator circuit care. Each of the reviewer’s comments was carefully assessed and the document was further revised as appropriate. To identify the evidence for addressing these questions, a PubMed (MEDLINE) search was conducted using the following search terms: pneumonia AND mechanical ventilation, humidifier, ventilator circuit, heated circuit, suction catheter, endotracheal suction, closed suction catheter, respiratory therapy equipment, endotracheal intubation, heat and moisture exchanger, tracheostomy, respiratory care, equipment contamination, equipment disinfection, artificial ventilation. The search was confined to human studies published in the English language. References and abstracts were retrieved into reference management software (EndNote, ISI, Berkeley, California). By inspection of these titles, references having no relevance to the study questions were eliminated. For the titles that remained, the abstracts were assessed for relevance and additional references were eliminated as appropriate. This process was conducted independently by 2 individuals, after which their reference lists were merged to provide the reference base for further analysis. Throughout the process of developing these guidelines, members of the Writing Committee surveyed cross-references to identify additional references to be added to the reference base for analysis. Data were extracted from selected references using a standardized critique form. To validate this form and to establish the reliability of the review process, several references were evaluated by the entire committee during a face-to-face meeting. All references were then independently examined by at least 2 members of the Writing Committee. The critiques were compared and differences were resolved using an iterative process. All references were graded according to the following scheme: Level 1: Randomized, controlled trial with statistically significant results Level 2: Randomized, controlled trial with significant threats to validity (eg, small sample size, inappropriate blinding, weak methodology) Level 3: Observational study with a concurrent control group Based on studies published in the 1960s that showed an association between respiratory equipment and nosocomial pneumonia,4,5 the practice of changing ventilator circuits at least daily was established. In fact, circuits were changed every 8 hours in some hospitals, in an attempt to reduce the incidence of VAP. This practice was challenged in a landmark study published by Craven et al in 1982.6 In that study 240 cultures of inspiratory-phase gas were obtained from 95 patients. There was no significant difference in the frequency of positive cultures in circuits changed 870 RESPIRATORY CARE • SEPTEMBER 2003 VOL 48 NO 9 Do Ventilator Circuits Need to Be Changed at Regular Intervals? EVIDENCE-BASED GUIDELINE: CARE OF THE VENTILATOR CIRCUIT Fig. 1. Randomized, controlled trials of the relationship between ventilator circuit change frequency and the risk of ventilator-associated pneumonia. RR ⫽ relative risk. CI ⫽ confidence interval. every 24 hours (30%) and in circuits changed every 48 hours (32%). Moreover, no significant increase in circuit colonization occurred between 24 and 48 hours. Based on that study, most hospitals in the United States adopted the practice of changing ventilator circuits at 48-hour intervals. Craven et al estimated that $300,000 (in 1982 dolTable 1. lars) would be saved at 20 Boston teaching hospitals by adopting this practice. Interestingly, Craven et al did not report VAP rates in their study. The effect of ventilator circuit change interval on VAP rate was assessed in 4 prospective randomized, controlled trials (Table 1 and Fig. 1).7–10 Although each of these Summary of Randomized Controlled Trials Investigating the Relationship Between Ventilator Circuit Change Frequency and the Risk of Ventilator-Associated Pneumonia Control Group Citation Craven 19867 Dreyfuss 19918 Kollef 19959 Long 199610 Study Population Adult patients requiring mechanical ventilation ⬎ 48 h Adult patients requiring mechanical ventilation ⬎ 48 h Adult patients requiring mechanical ventilation ⬎ 5 d Neonatal and adult mechanically ventilated patients Blinding VAP Diagnosis Control Group Treatment Group Treatment Group Level Relative Risk (95% CI) n Pneumonia (%) n Pneumonia (%) 106 29.2 127 14.2 1 0.48 (0.29, 0.82) VAP assessors Clinical Circuit changes every 24 h Circuit changes every 48 h VAP assessors Quantitative cultures Circuit changes every 48 h No circuit changes 35 31.4 28 28.5 1 0.91 (0.42, 1.95) VAP assessors Clinical Circuit changes every 7 d No circuit changes 153 28.8 147 24.5 1 0.85 (0.58, 1.24) None Clinical Circuit changes 3 times/wk Circuit change 1/wk 213 12.7 234 11.1 2 0.88 (0.53, 1.45) 507 22.3 536 16.4 TOTAL 0.76 (0.57, 1.00) VAP ⫽ ventilator-associated pneumonia. CI ⫽ confidence interval. RESPIRATORY CARE • SEPTEMBER 2003 VOL 48 NO 9 871 EVIDENCE-BASED GUIDELINE: CARE OF THE VENTILATOR CIRCUIT Fig. 2. Observational studies of the relationship between ventilator circuit change frequency and the risk of ventilator-associated pneumonia. RR ⫽ relative risk. CI ⫽ confidence interval. studies evaluated different circuit change intervals, the combined effect supports the practice of less frequent circuit changes (relative risk 0.76, 95% confidence interval [CI] 0.57 to 1.00, p ⫽ 0.05). In each of these studies, the risk of VAP was decreased when circuits were changed less frequently. Ventilator circuit change interval was also assessed in 7 studies with historical control groups (Table 2 and Fig. 2).11–17 Again, the combined effect supports the practice of less frequent circuit changes (relative risk 0.87, 95% CI 0.63 to 1.18, p ⫽ 0.37). Two well-designed randomized, controlled trials evaluated the practice of “no changes” of ventilator circuits.8,9 However, the maximum duration of time that the circuit can be used safely is unknown. In one of those studies, the maximum duration of use of a circuit was 29 days.8 The other study did not report the maximum duration of use of a circuit but did report that 35% of patients were ventilated for ⬎ 14 days.9 The costs associated with ventilator circuit changes were calculated in 8 studies.6,8,9,12–15,17 Because these studies were conducted over a span of 20 years and in different countries, direct cost comparisons are difficult. Not surprisingly, each of these studies suggests considerable savings in personnel and materials costs with less frequent ventilator circuit changes. One study evaluated equipment failure (circuit leaks) related to ventilator circuit change frequency.9 In that study there was no significant difference in equipment failures when circuits were changed at Most studies used heated passover humidifiers, although several used bursting-bubble cascade-type humidifiers.8,12,17 There is concern related to the use of bursting-bubble humidifiers because these have shown the potential to generate aerosols capable of carrying microorganisms.18,19 However, this is not a consideration in the present day, as these devices are no longer 872 RESPIRATORY CARE • SEPTEMBER 2003 VOL 48 NO 9 weekly intervals and when circuits were not changed at regular intervals. The majority of the studies were in adult patients in acute care units. One study was conducted in a subacute care unit.13 Two studies included neonatal and pediatric mechanically ventilated patients.10,11 Although ventilator circuit change interval has been studied less in patient groups other than adult patients in acute care units, the available evidence suggests no increased risk for VAP associated with infrequent circuit changes in these populations. There have been no studies that separately addressed special populations such as immunocompromised or burned patients. Recommendation #1. Ventilator circuits should not be changed routinely for infection control purposes. The available evidence suggests no patient harm and considerable cost savings associated with extended ventilator circuit change intervals. The maximum duration of time that circuits can be used safely is unknown. (Grade A) EVIDENCE-BASED GUIDELINE: CARE Table 2. OF THE VENTILATOR CIRCUIT Summary of Observational Studies Investigating the Relationship Between Ventilator Circuit Change Frequency and the Risk of Ventilator-Associated Pneumonia Control Group Citation Study Population VAP Diagnosis Control Group Treatment Group n Pneumonia (%) Treatment Group n Pneumonia (%) Level Relative Risk (95% CI) Lareau 197811 Adult, pediatric, and neonatal mechanically ventilated patients Clinical Circuit changes at 8-h intervals Circuit changes at 24-h intervals 213 7.5 271 11.8 4 1.57 (0.89, 2.79) Hess 199512 Adult mechanically ventilated patients Clinical Circuit changes at 2-d intervals Circuit changes at 7-d intervals 1,708 5.6 1,715 4.6 4 0.83 (0.62, 1.11) Thompson 199613 Adult mechanically ventilated patients in a subacute care facility Clinical Circuit changes at 7-d intervals Circuit changes at 14-d intervals 31 9.7 18 11.1 4 1.15 (0.21, 6.24) Kotilainen 199714 Adult mechanically ventilated patients Clinical Circuit changes at 3-d intervals Circuit changes at 7-d intervals 88 9.1 146 6.2 4 0.68 (0.27, 1.69) Fink 199815 Adult mechanically ventilated patients Clinical Circuit changes at 2-d intervals Circuit changes at 30-d intervals 336 10.7 157 6.4 4 0.59 (0.30, 1.17) Han 200116 Adult mechanically ventilated patients Clinical Circuit changes at 2-d intervals Circuit changes at 7-d intervals 413 9.2 231 3.5 4 0.38 (0.18, 0.79) Lien 200117 Adult mechanically ventilated patients Clinical Circuit changes at 2-d intervals Circuit changes at 7-d intervals 6,213 2.9 7,068 3.2 4 1.14 (0.94, 1.38) 9,002 4.1 9,606 3.8 Total 0.87 (0.63, 1.18) VAP ⫽ ventilator-associated pneumonia. CI ⫽ confidence interval. commercially available. Moreover, bacterial levels in heated humidifiers are low and nosocomial pathogens survive poorly in this environment.20 Although a few studies used reusable circuits,11,17 most used disposable circuits. In several studies, heated-wire circuits were used.10,14 –16 One small study21 compared heated-wire circuits and nonheated-wire circuits and found no difference in VAP rate (relative risk 1.57 in favor of nonheated-wire circuits, 95% CI 0.55 to 4.45). The condensate that accumulates in the ventilator circuit is contaminated,22 and care should be taken to avoid its cross-contamination of other patients. Although it makes sense that care should be taken to avoid breaking the circuit—which could contaminate the interior of the ventilator circuit—this has not been studied. One observational study compared daily with biweekly circuit changes with the use of a passive humidifier and reported no change in VAP rate with the longer circuit change interval.23 Another study compared disposable and reusable humidifiers during mechanical ventilation, and reported no difference in VAP.24 It is fair to say that the risk of VAP is not increased by less frequent circuit changes, despite a variety of practices related to the type of circuit used and the care of the circuit. Standard practice calls for use of sterile water in the humidifier of the ventilator circuit. Because water is an important reservoir for nosocomial pathogens and there has been no published study of this topic using modern humidification systems, the practice of filling humidifiers with sterile water appears appropriate. RESPIRATORY CARE • SEPTEMBER 2003 VOL 48 NO 9 873 Recommendation #2. Evidence is lacking related to VAP and issues of heated versus unheated circuits, type of heated humidifier, method for filling the humidifier, and technique for clearing condensate from the ventilator circuit. It is prudent to avoid excessive accumulation of condensate in the circuit. Care should be taken to avoid accidental drainage of condensate into the patient’s airway and to avoid contamination of caregivers during ventilator disconnection or during disposal of condensate. Care should be taken to avoid breaking the ventilator circuit, which could contaminate the interior of the circuit. (Grade D) Is Ventilator-Associated Pneumonia Rate Affected By the Choice of Active Versus Passive Humidification in Mechanically Ventilated Patients? Humidification of the inspired gas is a standard practice in the care of mechanically ventilated patients. Humidifiers can be active or passive. Active humidifiers pass the inspired gas either through (bubble) or over (passover, EVIDENCE-BASED GUIDELINE: CARE wick) a heated water bath. Passive humidifiers (artificial nose, heat-and-moisture exchanger) trap heat and humidity from the patient’s exhaled gas and return some of that to the patient on the subsequent inhalation. By its nature the ventilator circuit remains dry with the use of a passive humidifier. Passive humidifiers also have filtering characteristics, and some are constructed specifically to function as filters as well as humidifiers. The performance of humidification systems has been described in detail elsewhere.25 Because passive humidifiers maintain a dry circuit and have filtering properties, there has been much interest in their potential to decrease the incidence of VAP. Indeed, several studies have reported that circuit contamination is reduced with the use of passive humidifiers.26 –31 One study reported similar tracheal colonization rates with active and passive humidifiers.32 The VAP rate with passive versus active humidification was addressed in 6 studies (Table 3).21,33–37 The combined results of these studies (Fig. 3) indicate a lower risk of VAP with the use of passive humidification (relative risk 0.65, 95% CI 0.44 to 0.96, p ⫽ 0.03). Although the combined effect from this meta-analysis shows a statistically lower VAP for the use of passive humidifiers, it is of interest to note that only one of the studies36 reported a significant reduction in VAP with the use of passive humidifiers. These studies used various brands of passive humidifier, all were conducted with adult patients, and all were conducted in the acute care setting. Two studies reported no significant differ- Table 3. Citation OF THE VENTILATOR CIRCUIT ence in the VAP rate when comparing designs of passive humidifiers (different components, hydrophobic vs hygroscopic).38,39 In addition to VAP, there are other important issues that must be considered when a passive humidifier is used. These include the dead space of the device, the resistive load of the device, the difficulty in delivery of aerosolized medications, and the potential for airway occlusion. An increased work-of-breathing attributable to the use of a passive humidifier has been reported.40 The use of a passive humidifier has been associated with higher PaCO2 and higher minute ventilation requirement.41 Another study reported significant reduction in PaCO2 with removal of the passive humidifier in patients receiving lung-protective ventilation.42 Of considerable concern is the increased risk of airway occlusion when a passive humidifier is used. In one study33 the use of passive humidifiers was interrupted because of a fatal occlusion of the airway. Other studies have also reported greater risk of airway occlusion with the use of a passive humidifier.34,43,44 A meta-analysis of airway occlusion associated with the use of passive humidifier reported a relative risk of 3.84 (95% CI 1.92 to 7.69, p ⫽ 0.0001), favoring the use of active humidification (ie, indicating a significantly greater risk of airway occlusion with a passive humidifier).45 When a passive humidifier is used, it is important that one be selected that has an adequate moisture output, to minimize the risk of airway occlusion. Summary of Randomized Controlled Trials Investigating the Relationship Between Type of Humidification and the Risk of VentilatorAssociated Pneumonia Study Population VAP Diagnosis Martin 199033 Roustan 199234 Dreyfuss 199535 Branson 199621 Adult mechanically ventilated patients Adult mechanically ventilated patients Adult mechanically ventilated patients Adult mechanically ventilated patients Clinical Kirton 199736 Kollef 199837 Adult mechanically ventilated patients Adult mechanically ventilated patients Clinical Total Clinical Quantitative cultures Clinical Clinical Active Humidifier Passive humidifier Passive Humidifier Level Relative Risk (95% CI) n Pneumonia (%) n Pneumonia (%) Pall Ultipor breathing circuit filter Pall BB 2215 42 19.0 31 6.5 2 0.34 (0.08, 1.49) 61 14.8 55 9.1 1 0.62 (0.22, 1.73) DAR Hygrobac II 70 11.4 61 9.8 1 0.86 (0.32, 2.34) Baxter nonfiltered hygroscopic condenser humidifier Pall BB-100 54 5.6 49 6.1 2 1.10 (0.23, 5.21) 140 15.7 140 6.4 2 0.41 (0.20, 0.86) 147 10.2 163 9.2 1 0.90 (0.46, 1.78) 514 12.6 499 8.0 Nellcor-Puritan-Bennett hygroscopic condenser humidifier 0.65 (0.44, 0.96) VAP ⫽ ventilator-associated pneumonia. CI ⫽ confidence interval. 874 RESPIRATORY CARE • SEPTEMBER 2003 VOL 48 NO 9 EVIDENCE-BASED GUIDELINE: CARE OF THE VENTILATOR CIRCUIT Fig. 3. Randomized, controlled trials of the relationship between type of humidification and the risk of ventilator-associated pneumonia. RR ⫽ relative risk. CI ⫽ confidence interval. Recommendation #3. Although the available evidence suggests a lower VAP rate with passive humidification than with active humidification, other issues related to the use of passive humidifiers (resistance, dead space volume, airway occlusion risk) preclude a recommendation for the general use of these devices. The decision to use a passive humidifier should not be based solely on infection control considerations. (Grade A) Do Passive Humidifiers Need to Be Changed at Regular Intervals? nary disease).56 Based on the available evidence, it seems prudent to closely monitor the technical performance of these devices if used longer than 48 hours. Recommendation #4. Passive humidifiers do not need to be changed daily for reasons of infection control or technical performance. They can be safely used for at least 48 hours, and with some patient populations some devices may be able to be used for up to 1 week. (Grade A) Do In-Line Suction Catheters Need to Be Changed at Regular Intervals? The manufacturers of passive humidifiers typically recommend that they be changed at daily intervals. There has been interest in the safety of changing these devices less frequently, both in terms of VAP rate and device performance. Two randomized, controlled trials46,47 and 2 observational studies compared daily versus less frequent changes of passive humidifiers (Table 4).48,49 In 2 studies passive humidifiers were changed at 48-hour intervals,48,49 in a separate study they were changed at 5-day intervals,46 and in another study they were changed at 7-day intervals.47 For the pooled results (Fig. 4), no significant difference in VAP rate was found with less frequent changes of passive humidifiers, in either the randomized, controlled studies (relative risk 0.58, 95% CI 0.24 to 1.41, p ⫽ 0.14) or the observational studies (relative risk 1.13, 95% CI 0.73 to 1.76, p ⫽ 0.9). Other studies have evaluated the technical performance of passive humidifiers used for durations up to 48 hours,50 –52 96 hours,53–55 and 7 days.56 However, caution has been suggested related to prolonged use of passive humidifiers with some devices52,57 and in some patient populations (eg, chronic obstructive pulmo- In-line closed suction systems allow mechanically ventilated patients to be suctioned without removal of ventilator support. This may decrease the complications associated with suctioning58 and might prevent alveolar derecruitment during suctioning.59,60 One study reported significantly less environmental contamination with closed suctioning than with open suctioning.61 Observational studies report high levels of contamination in closed suction catheters that are in use.62,63 However, this contamination usually arises from the endotracheal tube and the patient’s lower respiratory tract. Accordingly, the patient usually contaminates the catheter, rather than vice versa. Use of closed suctioning has been recommended as part of a VAPprevention program.64 Two prospective, randomized, controlled trials reported similar VAP rates with closed suctioning and open suctioning.58,65 Another study, however, reported a 3.5 times greater risk of VAP in patients randomized to receive open suctioning than those receiving closed suctioning.66 Although the available evidence is not conclusive that closed suctioning decreases the risk of VAP, RESPIRATORY CARE • SEPTEMBER 2003 VOL 48 NO 9 875 EVIDENCE-BASED GUIDELINE: CARE OF THE VENTILATOR CIRCUIT Fig. 4. Studies of the relationship between passive humidifier change frequency and the risk of ventilator-associated pneumonia. RR ⫽ relative risk. CI ⫽ confidence interval. Table 4. Summary of Studies Investigating the Relationship Between Change Frequency for Passive Humidifiers and the Risk of VentilatorAssociated Pneumonia Control Group Citation Study Population Randomized Controlled Trials Davis 200046 Adult mechanically ventilated patients Thomachot Adult mechanically 200247 ventilated patients Total Observational Studies Djedaini Adult mechanically 199548 ventilated patients Daumal Adult mechanically 199949 ventilated patients VAP Diagnosis Clinical Clinical Quantitative cultures Quantitative cultures Control Group Treatment Group HME changed every 24 h HME changed every 24 h HME changed every 120 h HME changed every 7 d HME changed every 24 h HME changed every 24 h HME changed every 48 h HME changed every 48 h Total Treatment Group Level n Pneumonia (%) Relative Risk (95% CI) 8.0 120 7.5 1 0.94 (0.38, 2.34) 84 26.2 71 9.9 1 0.38 (0.17, 0.83) 184 16.3 191 8.4 61 9.8 68 11.8 4 1.20 (0.44, 3.25) 174 14.4 187 16.0 4 1.12 (0.68, 1.82) 235 13.2 255 14.9 n Pneumonia (%) 100 0.58 (0.24, 1.41) 1.13 (0.73, 1.76) VAP ⫽ ventilator-associated pneumonia. CI ⫽ confidence interval. HME ⫽ heat and moisture exchanger. there is no high-level evidence that use of closed suction catheters increases the risk of VAP. The in-line closed suction catheter might be considered an extension of the ventilator circuit. Because ventilator circuits do not need to be changed at regular intervals for infection control purposes, this might suggest that in-line suction catheters also do not need to be changed at regular intervals for infection control purposes. Although the manufacturers of in-line suction catheters recommend that these devices be changed at regular intervals, there is accumulating evidence that they might not need to be changed routinely. One observational study reported no change in VAP rate when in-line suction catheters were changed on a weekly rather than daily basis.67 Another study reported no significant difference in VAP rate between patients randomized to receive daily changes of the in-line suction catheter and those with whom there were no routine changes of the in-line catheter 876 RESPIRATORY CARE • SEPTEMBER 2003 VOL 48 NO 9 EVIDENCE-BASED GUIDELINE: CARE (relative risk 0.99, 95% CI 0.66 to 1.50).68 The maximum duration of use of a closed suction catheter in that study was 67 days. There were few device malfunctions when in-line catheters were changed less frequently than daily, and there were important cost savings associated with this practice.67,68 As with ventilator circuits, the maximum duration that closed suction catheters can be used safely is not known. Recommendation #5. The use of closed suction catheters should be considered part of a VAP prevention strategy. When closed suction catheters are used, they do not need to be changed daily for infection control purposes. The maximum duration of time that closed suction catheters can be used safely is unknown. (Grade A) Other Issues Other issues related to the technical aspects of mechanical ventilation may be important in relation to VAP. Medication nebulizers can be a source of contamination that could lead to VAP.69 Accordingly, with nebulizers care must be taken to avoid contamination of the ventilator circuit and the patient’s respiratory tract. It is commonly believed by respiratory therapists that the risk of ventilator circuit contamination is reduced with the use of metered-dose inhalers, but this has not been reported. Manual ventilator devices that are commonly kept at the bedside of mechanically ventilated patients have been shown to be a source of airway contamination, so care should be taken to minimize the potential infection risks associated with manual ventilator devices.70,71 One study reported a significantly greater likelihood of VAP among patients who underwent transport out of the intensive care unit for diagnostic, surgical, or miscellaneous interventions (odds ratio 3.8, 95% CI 2.6 to 5.5, p ⬍ 0.001).72 Because a VAP risk education program for respiratory therapists and critical care nurses decreased the incidence of VAP,73 VAP risk education should be widely implemented. Recommendation # 6. Clinicians (respiratory therapists, nurses, and physicians) caring for mechanically ventilated patients should be aware of risk factors for VAP (eg, nebulizer therapy, manual ventilation, and patient transport). (Grade B) Discussion Substantial evidence now exists to make recommendations related to the technical practices of mechanical ventilation and the risk of VAP. However, important gaps also exist in this evidence base. For example, most of the published evidence comes from studies of adult patients. Few RESPIRATORY CARE • SEPTEMBER 2003 VOL 48 NO 9 OF THE VENTILATOR CIRCUIT data have been published for neonatal and pediatric populations. In addition most studies come from the acute care setting. Finally, there has been little research done on important subgroups of patients, such as immunocompromised patients. Accordingly, much remains to be learned about important relationships between the technical aspects of mechanical ventilation and the risk of VAP. Thus, these evidence-based guidelines provide not only a basis for current practice but are also a framework for further investigation. REFERENCES 1. Cook D, De Jonghe B, Brochard L, Brun-Buisson C. Influence of airway management on ventilator-associated pneumonia: evidence from randomized trials. JAMA 1998;279(10):781–787. Erratum in: JAMA 1999;281(22):2089 2. Cook DJ, Walter SD, Cook RJ, Griffith LE, Guyatt GH, Leasa D, et al. Incidence of and risk factors for ventilator-associated pneumonia in critically ill patients. Ann Intern Med 1998;129(6):433–440. 3. Cook D, Ricard JD, Reeve B, Randall J, Wigg M, Brochard L, Dreyfuss D. Ventilator circuit and secretion management strategies: a Franco-Canadian survey. Crit Care Med 2000;28(10):3547–3554. 4. Reinarz JA, Pierce AK, Mays BB, Sanford JP. The potential role of inhalation therapy equipment in nosocomial pulmonary infection. J Clin Invest 1965;44:831–839. 5. Edmondson EB, Reinarz JA, Pierce AK, Sanford JP. Nebulization equipment: a potential source of infection in gram-negative pneumonias. Am J Dis Child 1966;111(4):357–360. 6. Craven DE, Connolly MG Jr, Lichtenberg DA, Primeau PJ, McCabe WR. 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Zack JE, Garrison T, Trovillion E, Clinkscale D, Coopersmith CM, Fraser VJ, Kollef MH. Effect of an education program aimed at reducing the occurrence of ventilator-associated pneumonia. Crit Care Med 2002;30(11):2407–2412. Interested persons may photocopy these Guidelines for noncommercial purposes of scientific or educational advancement. Please credit AARC and RESPIRATORY CARE Journal. All of the AARC CPGs may be downloaded at no charge from http://www.rcjournal.com/online/ RESPIRATORY CARE • SEPTEMBER 2003 VOL 48 NO 9 879