The Science Journal of the American Association for Respiratory Care

2005 OPEN FORUM Abstracts

GRAM NEGATIVE BACTERIAL CONTAMINATION IN THE CIRCUIT OF PROCESSED VAPOTHERM SYSTEMS.

Julianne Perretta BS, RRT-NPS, Betty Blake BS, RRT-NPS, Amy Winkler RN, MPH, Lisa Maragakis MD, Lee Woods MD, PhD, The Johns Hopkins Hospital, Baltimore, Maryland

Background: Gram-negative bacteria, specifically Ralstonia pickettii and Pseudomonas aeruginosa, have been detected as contaminates of several solutions used in the respiratory field. These solutions include saline, distilled water, deionized water, and waters that have undergone a sterilization process. These solutions have been linked to nosocomial outbreaks associated with contaminated solutions used for patient care. R. pickettii and P. aeruginosa can proliferate over a wide range of temperatures (15-42 C), making it ideal for growth in heated, and humidified circuitry. P. aeruginosa is measured at 0.5 micron, and R. pickettii has also been shown to be small enough to pass through sterilization filters as small as 0.2micron.

Method: Random surveillance cultures of the water side of 3 Vapotherm machines in patient use in the Neonatal Intensive Care Unit (NICU) found the presence of P. aeruginosa and other non-speciated gram (-) rods that were neither P. aeruginosa or Serratia marcescens. Clinical staff members were re-educated on the proper Vapotherm cleaning procedure, all machines were cleaned, per manufacturer's recommendation, and their vapor transfer cartridges replaced. NICU equipment change policy was modified to change Vapotherm water bags every 24 hours. Follow up cultures on 2 machines (1 in patient use, 1 immediately after cleaning) detected R. pickettii in both machines. All Vapotherm machines were removed from NICU patient use. A representative from Vapotherm was brought to the NICU to demonstrate and monitor cleaning procedures. Repeat cultures from all 8 NICU Vapotherm machines were negative for gram (-) bacteria, although the Vapotherm representative observed no discrepancy between staff cleaning techniques and current recommended guidelines. Two machines were set up in the NICU and left to run for one week of continuous use (not on patients). Cultures of the vapor from these two delivery tubes and the machines were negative for any gram (-) bacterial growth.

Cultures of Vapotherm Machines in NICU

  Initial Follow up Cultures Cultures after Monitored Cleaning Cultures on Vapotherm running
Number of machines cultured 2 2 8 2
Number of machines positive 2 2 0 0

Results: The Vapotherm's vapor transfer cartridge humidifies gas in the molecular vapor phase, by transpiration through micro-porous membrane material with pore sizes < 0.01micron. This technology creates a vapor phase humidification that prevents direct contact between the water source and breathing gas, thus preventing the need for sterile water. Use of non-sterile water allowed for the entrainment of R. pickettii and P. aeruginosa through the Vapotherm system and contaminated machines in use, although there were no patient infections identified as associated with Vapotherm use. The recurrence of positive cultures despite proper cleaning and increased equipment change frequency suggests possible breach in cleaning technique or contamination of the distilled water used for cleaning and machine use. All cleaning solution and distilled water cultures were negative for gram-negative organisms.

Conclusions: Using distilled or deionized water in conjunction with reusable equipment can increase the risk of introducing bacterial contaminate into a heated, humidified breathing system. A system that utilizes single patient use equipment wherever in contact with water could decrease the risk of continued contamination of equipment, and use of sterile, non-refillable water systems could reduce the risk of water contamination.

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