Infection Control Considerations for Ventilator Systems
Michael McPeck RRT, Director
Respiratory Care & Biomedical Engineering University Medical Center State University of New York at Stony Brook
Our goal for today
Respiratory Failure Ventilator
Circuits
Systems
Humidifiers
Closed-System
Suction Research Practice Changes
Acute Respiratory Failure (ARF)
A
condition in which the lungs, and frequently the heart and lungs, are not able to sufficiently and normally oxygenate the blood and body tissue. Often, the ability to excrete CO2 is also impaired.
ARF may develop ...
As
an acute lung injury in patients with normal lungs
or
As
an acute illness, superimposed on a chronic lung disease
ARF is diagnosed and managed with arterial blood gases ...
PaO2 < 50 mm Hg and / or PaCO2 > 50 - 60 mm Hg
Causes of respiratory failure
Respiratory
Center in Brain Neuromuscular Connections Thoracic Bellows Airways (upper & lower) Lung parenchyma (alveoli)
It only requires one disrupted “link” to cause respiratory failure!
Brain
Nerves
Bellows
Alveoli Airways
Effects of Major Surgery and General Anesthesia
drugs Paralyzing agents Chest or abdominal incision Dry, irritating gases Pain, splinting, and ineffective cough
Alveoli
Narcotic
Brain
Nerves
Bellows
Airways
Temporary ventilatory support
Lung injury and respiratory failure is treated with mechanical ventilation as a temporizing measure until such time as the lung heals and the patient can resume responsibility for adequate respiratory function.
A ventilator is a life support device -- a system of essential elements designed to augment or totally support cardiorespiratory function (i.e., ventilation, oxygenation, and CO2 excretion) in a predetermined manner for an indeterminate amount of time.
Typical Vent Patients by Unit
SICU - Trauma, ARDS and post-ops MICU - ARDS, severe pneumonias CCU - ARDS, cardiovascular failure RCU - COPD and ventilator dependence
PICU - Severe asthma, near-drowning, pneumonias NICU - HMD due to prematurity Burn - ARDS CVICU - post-op CABG ER & Shock/Trauma trauma, COPD, heart disease, poisonings, etc.
UH Ventilator Statistics
YEAR 1992 1993 1994 1995 1996 1997 VENT DAYS 12,363 14,001 13,585 15,562 13,551 14,729
Typical ventilator setup
Artificial Airway
HEPA Filter
Ventilator Circuit
Heated Humidifier
Heated humidification
The early days ...
The potential role of inhalation therapy equipment in nosocomial pulmonary infection. Reinarz, et al. J Clin Invest 1965; 44:831-839. A hospital outbreak of Serratia marcesens associated with ultrasonic nebulizers. Ringrose, et al. Ann Intern Med 1968; 69: 719-729. Long-term evaluation of decontamination of inhalation therapy equipment and the occurrence of necrotizing pneumonia. Pierce, et al. N Engl J med 1970; 282:518-530. Bacterial contamination of aerosols. Pierce, et al. Arch Intern Med 1973; 131:156-159.
Cascade® Humidifier
Humidifier evolution
In the “early days,” both pneumatic and ultrasonic nebulizers (large volume particle generators) were used to provide humidification during mechanical ventilation. The Cascade® Humidifier was the first “vapor phase” humidifier but it inadvertently produced aerosols.
Ref: Bubbling humidifiers produce microaerosols which can carry bacteria. Rhame, et al. Infection Control 1986; 7: 403-406.
Humidifier evolution
Contemporary humidifiers produce water vapor only and are incapable, by design, of producing particles or conducting particles in the gas stream, even at flowrates as high as 120 L/min. Contemporary humidifiers heat water to such a high temperature that they may be at least bacteriostatic, if not bacteriocidal.
Ref: Humidifiers kill bacteria. Gilmour, et al. Anesthesiology 1991; 75(3A): a498.
Wick type heated humidifier
Wick type heated humidifier
Typical ventilator setup
Artificial Airway
HEPA Filter
Ventilator Circuit
Heated Humidifier
The old standard of care
circuit cultures were done, they were uniformly positive with high concentrations of organisms identical to those in the patient’s sputum. Change the circuit and the humidifier every 24 hours.
When
Craven, 1982 - 1984
contemporary heated molecular humidifiers as source of circuit contamination. Focused on the circuit condensate. 33%, 64% and 80% of a sample of 30 circuits used on 27 different patients were colonized after periods of 2 hours, 12 hours and 24 hours respectively.
Exonerated
Craven, 1982 - 1984
24 hours, 80% of condensate samples were contaminated at a median level of 2 X 105 organisms/ml were observed. Cultures revealed Pseudomonas, Acinetobacter, Klebsiella, Serratia, Staph aureus & epidermis, Streptococci and yeasts. Other investigators found concentrations of 2.7 X 104 and 1 X 109 cfu/ml
At
Craven, 1982 - 1984
humidifier doesn’t contaminate the circuit or the patient. The patient contaminates the circuit almost immediately after a clean circuit is installed. Quantitative determinations of total colonization in vent circuit tubing showed no significant difference between 24 and 48 hours.
The
Condensate References
Contamination of mechanical ventilators with tubing changes every 24 or 48 hours. Craven, et al. N Eng J Med 1982; 306:1505-1509. Contaminated condensate in mechanical ventilator circuits: A risk factor for nosocomial pneumonia. Craven, et al. Am Rev Respir Dis 1984; 129:625-628. Results of a survey of ventilator circuit practices in the United States. Craven, et al. Infect Control 1984; 5:353-355. Bacterial colonization in humidifying Cascade reservoirs after 24 and 48 hours of continuous mechanical ventilation. Goularte, et al. Infect Control 1987; 8:200-203. Craven, at al. Pathogenesis and prevention of nosocomial pneumonia in the mechanically ventilated patient. Craven DE and Steger KA. Respir Care 1989; 34:85-97.
Craven, 1982 - 1984
changing ventilator circuits at 48 hour intervals. Suggested $30,000 annual savings in supplies and personnel time at Boston City Hospital. Called attention to the role of the infectious condensate that forms in the vent circuit tubing.
Recommends
Ventilator Circuit (Craven)
NovaVentrx Drain Modules
UH ventilator setup
“BUG” BOTTLE
Contemporary practice:
Ventilator circuit change frequency
20 US and Canadian hospital RC departments surveyed via RC-World internet discussion group, July 1997:
No routine changes 30 day changes 3, 7 or 14 day changes No reply
5 (25%) 7 (35%) 7 (35%) 1 (5%)
Kollef MH, Shapiro SD, Fraser VJ, Silver P, Murphy DM, Trovillion E, Hearns ML, Richards RD, Cracchilo L, Hossin L. Mechanical ventilation with or without 7-day circuit changes. A randomized controlled trial. Annals of Internal Medicine 1995; 123:168-174.
Closed system suction catheters
Closed
system suction (CSS) catheters, which have been in use in our intensive care units, were being changed at 24 h intervals in accord with the manufacturer’s recommendations. Because our ongoing surveillance has determined that ventilator circuit change intervals of 168 h (7 days) has not been associated with adverse outcomes, we proposed changing CSS catheters at 48 h intervals while measuring outcomes.
UH CSS Study Results
There were 98 admissions requiring 72 h of mechanical ventilation and the SICs were distributed thusly: 12.2% of patients were SIC 3 65.5% were SIC 4 22.3% were SIC 5 Results (figure) were stratified for patient acuity based on the SIC scores for each period.
Incidence Densities of VAP were reduced in all three SIC categories.
Ref: Srinivasan S, Singh F, Wojnar M, McPeck M. Greene W. Closed system suction catheters: The effect of decreased frequency of changes in mechanically ventilated patients. Respiratory Care 42:1081, 1997.
Contemporary practice:
Closed system suction catheter change frequency
20 US and Canadian hospital RC departments surveyed via RC-World internet discussion group, July 1997:
1 day intervals 2 day intervals 3 day or > intervals No reply
5 (25%) 5 (25%) 3 (15%) 7 (35%)
Kollef et al, Study design
Purpose: determine safety & costeffectiveness of not routinely changing CSS in mechanicallyMechanical ventilation ventilated patients Random assignment:
no routine CSS changes, n=258 every 24 hour CSS changes, n=263
with or without daily changes of in-line suction catheters.
Kollef M, Prentice D, Shapiro SD, Fraser VJ, Silver P, Trovillion E, Weilitz P, Von Harz B, St. John R. Am J Respir Crit Care Med 1997; 156:466-472.
Outcome measures:
incidence of VAP hospital mortality acquired organ system derangements LOSvent, LOSICU & LOShospital cost for in-line suction catheters
Kollef et al, Study results
Incidence of VAP:
38 patients (14.8%) receiving no in-line suction catheter changes 39 patients (14.7%) receiving Q 24 hour suction catheter changes hospital mortality LOS number of acquired organ system derangements death in patients with VAP No routine changes: 93 catheters @ $837. Q 24 hour changes: 1,224 catheters @ $11,016.
No significant difference for:
Cost:
Conclusion: Elimination of routine in-line suction catheter changes is safe and can reduce costs associated with providing mechanical ventilation.
Conclusions
The data from our preliminary study, as well as the Kollef study, supports the prediction that CSS catheters in our hospital can be safely changed at 48 h intervals without adverse outcomes. Savings in direct costs and labor are advantages. Based on our 1995 actual purchase data, we project direct cost savings of ~$25,000 per year by changing clinical practice such that CSS catheters are changed at 48 h intervals rather than 24 h. The study continues in the Medical and Surgical intensive care units.