The ventilator circuit and ventilator-associated pneumonia
- Dean Hess, RRT, PhD
Dean Hess, RRT, PhD
- Teaching Associate
- Harvard Medical School
Ventilator-associated pneumonia (VAP) refers to pneumonia that develops at least 48 hours after the initiation of mechanical ventilation [1,2]. It is probably caused by aerodigestive tract colonization, followed by aspiration of contaminated secretions into the lower airways (figure 1). Many of the risk factors for VAP increase the risk of pharyngeal colonization and aspiration (table 1), while most of the interventions to prevent VAP reduce colonization and aspiration (figure 2) [3-8].
The role of the ventilator circuit in VAP is reviewed here. The pathogenesis, risk factors, clinical presentation, diagnosis, prevention, and treatment of VAP are discussed separately. (See "Clinical presentation and diagnosis of ventilator-associated pneumonia" and "Epidemiology, pathogenesis, microbiology, and diagnosis of hospital-acquired and ventilator-associated pneumonia in adults" and "Risk factors and prevention of hospital-acquired and ventilator-associated pneumonia in adults" and "Treatment of hospital-acquired and ventilator-associated pneumonia in adults".)
ROLE OF THE VENTILATOR CIRCUIT IN VAP
The ventilator circuit refers to the tubing that connects the ventilator to a patient, as well as any device that is connected to the tubing. The most common devices include humidifiers, filters, suction catheters, and nebulizers.
The ventilator circuit appears to have only a small effect on the development of ventilator-associated pneumonia (VAP), assuming that reasonable infection control practices are followed. This view is supported by several pieces of evidence:
●Aspiration of contaminated pharyngeal secretions is the predominant cause of nosocomial pneumonia, not inhalation of aerosols containing bacteria [4,6,9].
- Kollef MH. What is ventilator-associated pneumonia and why is it important? Respir Care 2005; 50:714.
- Rello J, Diaz E. Pneumonia in the intensive care unit. Crit Care Med 2003; 31:2544.
- Kalil AC, Metersky ML, Klompas M, et al. Management of Adults With Hospital-acquired and Ventilator-associated Pneumonia: 2016 Clinical Practice Guidelines by the Infectious Diseases Society of America and the American Thoracic Society. Clin Infect Dis 2016; 63:e61.
- Coffin SE, Klompas M, Classen D, et al. Strategies to prevent ventilator-associated pneumonia in acute care hospitals. Infect Control Hosp Epidemiol 2008; 29 Suppl 1:S31.
- Craven DE. Preventing ventilator-associated pneumonia in adults: sowing seeds of change. Chest 2006; 130:251.
- Dodek P, Keenan S, Cook D, et al. Evidence-based clinical practice guideline for the prevention of ventilator-associated pneumonia. Ann Intern Med 2004; 141:305.
- Hess DR, Kallstrom TJ, Mottram CD, et al. Care of the ventilator circuit and its relation to ventilator-associated pneumonia. Respir Care 2003; 48:869.
- Tablan OC, Anderson LJ, Besser R, et al. Guidelines for preventing health-care--associated pneumonia, 2003: recommendations of CDC and the Healthcare Infection Control Practices Advisory Committee. MMWR Recomm Rep 2004; 53:1.
- Kollef MH. Prevention of hospital-associated pneumonia and ventilator-associated pneumonia. Crit Care Med 2004; 32:1396.
- Craven DE, Connolly MG Jr, Lichtenberg DA, et al. Contamination of mechanical ventilators with tubing changes every 24 or 48 hours. N Engl J Med 1982; 306:1505.
- Lareau SC, Ryan KJ, Diener CF. The relationship between frequency of ventilator circuit changes and infectious hazard. Am Rev Respir Dis 1978; 118:493.
- Craven DE, Kunches LM, Kilinsky V, et al. Risk factors for pneumonia and fatality in patients receiving continuous mechanical ventilation. Am Rev Respir Dis 1986; 133:792.
- Dreyfuss D, Djedaini K, Weber P, et al. Prospective study of nosocomial pneumonia and of patient and circuit colonization during mechanical ventilation with circuit changes every 48 hours versus no change. Am Rev Respir Dis 1991; 143:738.
- Hess D, Burns E, Romagnoli D, Kacmarek RM. Weekly ventilator circuit changes. A strategy to reduce costs without affecting pneumonia rates. Anesthesiology 1995; 82:903.
- Thompson, RE. Incidence of ventilator-associated pneumonia (VAP) with 14-day circuit change in a subacute environment. Respir Care 1996; 41:601.
- Kotilainen HR, Keroack MA. Cost analysis and clinical impact of weekly ventilator circuit changes in patients in intensive care unit. Am J Infect Control 1997; 25:117.
- Fink JB, Krause SA, Barrett L, et al. Extending ventilator circuit change interval beyond 2 days reduces the likelihood of ventilator-associated pneumonia. Chest 1998; 113:405.
- Han JN, Liu YP, Ma S, et al. Effects of decreasing the frequency of ventilator circuit changes to every 7 days on the rate of ventilator-associated pneumonia in a Beijing hospital. Respir Care 2001; 46:891.
- Kollef MH, Shapiro SD, Fraser VJ, et al. Mechanical ventilation with or without 7-day circuit changes. A randomized controlled trial. Ann Intern Med 1995; 123:168.
- Branson RD. The ventilator circuit and ventilator-associated pneumonia. Respir Care 2005; 50:774.
- Kelly M, Gillies D, Todd DA, Lockwood C. Heated humidification versus heat and moisture exchangers for ventilated adults and children. Cochrane Database Syst Rev 2010; :CD004711.
- Le Bourdellès G, Mier L, Fiquet B, et al. Comparison of the effects of heat and moisture exchangers and heated humidifiers on ventilation and gas exchange during weaning trials from mechanical ventilation. Chest 1996; 110:1294.
- Pelosi P, Solca M, Ravagnan I, et al. Effects of heat and moisture exchangers on minute ventilation, ventilatory drive, and work of breathing during pressure-support ventilation in acute respiratory failure. Crit Care Med 1996; 24:1184.
- Prin S, Chergui K, Augarde R, et al. Ability and safety of a heated humidifier to control hypercapnic acidosis in severe ARDS. Intensive Care Med 2002; 28:1756.
- Hinkson CR, Benson MS, Stephens LM, Deem S. The effects of apparatus dead space on P(aCO2) in patients receiving lung-protective ventilation. Respir Care 2006; 51:1140.
- Craven DE, Goularte TA, Make BJ. Contaminated condensate in mechanical ventilator circuits. A risk factor for nosocomial pneumonia? Am Rev Respir Dis 1984; 129:625.
- Gilmour IJ, Boyle MJ, Rozenberg A, Palahniuk RJ. The effect of heated wire circuits on humidification of inspired gases. Anesth Analg 1994; 79:160.
- Miyao H, Hirokawa T, Miyasaka K, Kawazoe T. Relative humidity, not absolute humidity, is of great importance when using a humidifier with a heating wire. Crit Care Med 1992; 20:674.
- Branson, RD, Davis, K, Brown, R, et al. Comparison of three humidification techniques during mechanical ventilation: Patient selection, cost, and infection considerations. Respir Care 1996; 41:809.
- Siempos II, Vardakas KZ, Falagas ME. Closed tracheal suction systems for prevention of ventilator-associated pneumonia. Br J Anaesth 2008; 100:299.
- Cobley M, Atkins M, Jones PL. Environmental contamination during tracheal suction. A comparison of disposable conventional catheters with a multiple-use closed system device. Anaesthesia 1991; 46:957.
- Stoller JK, Orens DK, Fatica C, et al. Weekly versus daily changes of in-line suction catheters: impact on rates of ventilator-associated pneumonia and associated costs. Respir Care 2003; 48:494.
- Kollef MH, Prentice D, Shapiro SD, et al. Mechanical ventilation with or without daily changes of in-line suction catheters. Am J Respir Crit Care Med 1997; 156:466.
- Craven DE, Lichtenberg DA, Goularte TA, et al. Contaminated medication nebulizers in mechanical ventilator circuits. Source of bacterial aerosols. Am J Med 1984; 77:834.
- Kollef MH, Von Harz B, Prentice D, et al. Patient transport from intensive care increases the risk of developing ventilator-associated pneumonia. Chest 1997; 112:765.
- Thompson AC, Wilder BJ, Powner DJ. Bedside resuscitation bags: a source of bacterial contamination. Infect Control 1985; 6:231.
- Weber DJ, Wilson MB, Rutala WA, Thomann CA. Manual ventilation bags as a source for bacterial colonization of intubated patients. Am Rev Respir Dis 1990; 142:892.
- Shi Z, Xie H, Wang P, et al. Oral hygiene care for critically ill patients to prevent ventilator-associated pneumonia. Cochrane Database Syst Rev 2013; :CD008367.
- Deem S, Treggiari MM. New endotracheal tubes designed to prevent ventilator-associated pneumonia: do they make a difference? Respir Care 2010; 55:1046.
- Mietto C, Pinciroli R, Patel N, Berra L. Ventilator associated pneumonia: evolving definitions and preventive strategies. Respir Care 2013; 58:990.
- Bowton DL, Hite RD, Martin RS, Sherertz R. The impact of hospital-wide use of a tapered-cuff endotracheal tube on the incidence of ventilator-associated pneumonia. Respir Care 2013; 58:1582.
- Philippart F, Gaudry S, Quinquis L, et al. Randomized intubation with polyurethane or conical cuffs to prevent pneumonia in ventilated patients. Am J Respir Crit Care Med 2015; 191:637.
- Bercault N, Wolf M, Runge I, et al. Intrahospital transport of critically ill ventilated patients: a risk factor for ventilator-associated pneumonia--a matched cohort study. Crit Care Med 2005; 33:2471.
- Manzano F, Fernández-Mondéjar E, Colmenero M, et al. Positive-end expiratory pressure reduces incidence of ventilator-associated pneumonia in nonhypoxemic patients. Crit Care Med 2008; 36:2225.
- Lucangelo U, Zin WA, Antonaglia V, et al. Effect of positive expiratory pressure and type of tracheal cuff on the incidence of aspiration in mechanically ventilated patients in an intensive care unit. Crit Care Med 2008; 36:409.
- MacIntyre NR, Cook DJ, Ely EW Jr, et al. Evidence-based guidelines for weaning and discontinuing ventilatory support: a collective task force facilitated by the American College of Chest Physicians; the American Association for Respiratory Care; and the American College of Critical Care Medicine. Chest 2001; 120:375S.
- Dries DJ, McGonigal MD, Malian MS, et al. Protocol-driven ventilator weaning reduces use of mechanical ventilation, rate of early reintubation, and ventilator-associated pneumonia. J Trauma 2004; 56:943.
- Klompas M. Complications of mechanical ventilation--the CDC's new surveillance paradigm. N Engl J Med 2013; 368:1472.
- Magill SS, Klompas M, Balk R, et al. Developing a new, national approach to surveillance for ventilator-associated events*. Crit Care Med 2013; 41:2467.
- ROLE OF THE VENTILATOR CIRCUIT IN VAP
- FREQUENCY OF VENTILATOR CIRCUIT CHANGE
- COMPONENTS OF THE VENTILATOR CIRCUIT
- Passive versus active humidification
- Heated versus unheated circuit
- Closed versus open suction
- Nebulizer versus inhaler
- Bag-valve resuscitator
- OTHER ASPECTS OF MECHANICAL VENTILATION AND VAP
- VENTILATOR ASSOCIATED EVENTS
- SOCIETY GUIDELINE LINKS
- SUMMARY AND RECOMMENDATIONS