Humidifier Reservoirs Research Articles

Can humidifier reservoir bacteria colonize the circuit during mechanical ventilation: An in vitro study.

Although the circuit condensate, an ideal bacterial reservoir during mechanical ventilation, may flow into the humidifier reservoir, no studies have investigated if humidifier reservoir colonized bacteria colonize other circuit locations with airflow. We aimed to prove whether the humidifier reservoir colonized bacteria colonize other circuit locations with airflow and provide some advice on the disposal of condensate in the clinical setting. An in vitro experiment was conducted. Mechanical ventilation simulators (n = 90) were divided into sterile water group (n = 30) and broth group (n = 60). In the sterile water group, sterile water was used for humidification, either Acinetobacter baumannii or Pseudomonas aeruginosa were inoculated to humidifier water in the humidifier reservoir, each accounted for 50% of the simulators. The broth group was performed the same as the sterile water group except for the addition of broth into the humidified water. After 24, 72, and 168 h of continuous ventilation, the humidifier water and different locations of the circuits were sampled for bacterial culture. All bacterial culture results of the sterile water group were negative. Bacteria in the humidifier water continued to proliferate in the broth group. With prolonged ventilation, the bacteria at the humidifier reservoir outlet increased. The bacteria at the humidifier reservoir outlet were much more in the Pseudomonas aeruginosa subgroup than in the Acinetobacter baumannii subgroup and the difference was statistically significant (p < .05). During continuous ventilation, no bacterial growth occurred at 10 cm from the humidifier reservoir outlet and the Y-piece of the ventilator circuits. Sterile water in the humidifier reservoir was not conducive to bacterial growth. Even if bacteria grew in the humidifier reservoir and could reach the humidifier reservoir outlet, colonization of further circuit locations with the airflow was unlikely. During a certain mechanical ventilation time, the amount of bacteria reaching the outlet of the humidifier reservoir varied due to different mobility of bacteria. In a clinical setting, nurses should not worry about a small amount of condensate backflow into the humidifier reservoir. Draining condensate into the humidifier reservoir can be used as a low risk and convenient method in clinical practice.

Emission of iron and aluminum oxide particles from ultrasonic humidifiers and potential for inhalation

Ultrasonic humidifier use is a potential source of human exposure to inhalable particulates. This research evaluated the behavior of insoluble iron oxide and aluminum oxide particles in water used to fill room-sized ultrasonic humidifiers. Solutions of 10 mg/L Fe, as iron oxide particles, or 5 mg/L Al, as aluminum oxide suspension, were added into tap water used to fill ultrasonic humidifiers. The humidifiers were operated for 14 h; samples were obtained over time and monitored for soluble and particulate Fe and Al, as well as particle sizes in the humidifier reservoir and emitted in aerosols. Denser, settleable particles of approximately 1.5 μm diameter of iron or aluminum oxides accumulated at the bottom of the humidifier reservoir. Smaller, suspended metal oxide particles of 0.22–0.57 μm diameter were emitted as aerosols from the humidifier. Soluble anions and cations in tap water were also present in the aerosols emitted from humidifiers. The results indicate that a typical 1.6 MHz ultrasonic humidifier can emit 0.22–0.57 μm particles and dissolved minerals from fill water into breathable air.

Outbreak investigation of Pseudomonas aeruginosa infections in a neonatal intensive care unit

A Pseudomonas aeruginosa outbreak was investigated in a neonatal intensive care unit that had experienced a prior similar outbreak. The 8 cases identified included 2 deaths. An investigation found the cause of the outbreak: tap water from contaminated hospital plumbing which was used for humidifier reservoirs, neonatal bathing, and nutritional preparation. Our findings reinforce a recent Centers for Medicare & Medicaid Services memo recommending increased attention to water management to improve awareness, identification, mitigation, and prevention of water-associated, health care-associated infections.

Emission of Inhalable Dissolved Drinking Water Constituents by Ultrasonic Humidifiers

Abstract This research investigated air–water quality interactions during single room humidification to increase indoor relative humidity. Ultrasonic humidifiers were filled with five different water quality types ranging from low to high total dissolved solids (TDS), hardness, and iron content. Aerosols emitted were evaluated for particle size distribution and dissolved metal and nonmetal constituents with inductively coupled plasma–mass spectroscopy. Emitted aerosols were in the inhalable range; the 90th percentile aerosol concentrations occur between 0.020 and 0.040 μm. Findings indicated that humidifier aerosols contained 85–90% of constituents present in the source water for low TDS, hardness, and iron tap waters. Deviations from this pattern were found in high hardness and high iron well waters due to precipitation of some constituents within the humidifier reservoir during operation. Deviation were seen only in the constituents that were precipitating as determined by comparison of filtered and unf...

Polymicrobial Bacteremia Involving Comamonas testosteroni.

Comamonas spp. are uncommon isolates in microbiology laboratories and have been rarely observed as an infectious agent in clinical practice. They have widespread environmental distribution and have been isolated from water, soil, and plants as well as from some hospital devices such as intravenous catheters and water contained in humidifier reservoirs used in respiratory treatment. The genus Comamonas originally contained the following species: acidovorans, testosteroni, kerstersii, terrigena, denitrificans, and nitrativorans. It now contains 17 species, while acidovorans spp. have been reclassified as Delftia acidovorans. In spite of its uncommon human pathogenesis, there are few reports on the aggressive manner of it as an opportunistic pathogen, mostly related to testosteroni spp. We present a case of polymicrobial bacteremia involving Comamonas testosteroni. The aim of this case report is to alert clinicians to the potential diagnosis of bloodstream infections caused by uncommon pathogens.

Estimation of endotoxin inhalation from shower and humidifier exposure reveals potential risk to human health

This paper investigates potential exposure to endotoxin in drinking water through the inhalation of aerosols generated by showers and humidifiers. Adverse health effects attributable to the inhalation of airborne endotoxin in various occupational settings are summarized, as are controlled laboratory inhalation studies. Data from investigations estimating aerosolization of particulate matter by showers and humidifiers provide a basis for similar analyses with endotoxin, which like minerals in water, is nonvolatile. A theoretical assessment of the inhalation of aerosolized endotoxin showed that while the likelihood of an acute response while showering is minimal, the same is not true for humidifiers. Ultrasonic and impeller (cool mist) humidifiers efficiently produce large numbers of respirable particles. It is predicted that airway inflammation can occur if humidifier reservoirs are filled with tap water, sometimes even at typical drinking-water distribution-system endotoxin concentrations. Higher endotoxin levels occasionally found in drinking water (>1,000 EU/ml) are very likely to induce symptoms such as chills and fever if used as humidifier feed water. While it is unlikely that treated drinking water would contain extremely high endotoxin levels occasionally observed in cyanobacterial blooms (>35,000 EU/ml), the potential for serious acute health consequences exist if used in humidifiers.

Evaluation of the contaminant organisms of humidifier reservoir water and investigation of the source of contamination in a university hospital in Turkey

This report describes the distribution of different contaminants (fungi, free-living amoebae, bacteria including Legionella) in the water of in-use oxygen humidifier reservoirs. We investigated reasons of contamination and also gave recommendations that may decrease the incidence of pneumonia related to use of contaminated humidifiers. The water of humidifiers is the major environmentassociated reservoir for nosocomial pneumonia pathogenes such as Pseudomonas aeruginosa, Legionella, and Aspergillus. 1 Inhalation of contaminated aerosols leads todirectinoculation of these pathogenes tothe airway, 2 and some free-living amoebae (FLA) serve as natural hosts for legionellae in the environments. 3 At particular risk for acquiring fungal infections are individuals who are immunocompromised. 4 Although many studies have been published on the contamination of humidifier’s water with bacteria, few highlighted fungal and amoebal contamination.

Sterile water used for humidification in low-flow oxygen therapy: Is it necessary?

Currently it is standard practice in many acute care hospitals to use only sterile water in humidifier reservoirs for the delivery of low-flow oxygen therapy. This practice is based primarily on the Centers for Disease Control's 1982 “Guideline for the Prevention of Nosocomial Pneumonia.” The present study was designed to investigate and compare the bacterial contamination of tap water and sterile water used to fill clean (nonsterile) disposable oxygen humidifier reservoirs. Disposable oxygen humidification reservoirs were assembled weekly according to standard protocol and regulated to deliver oxygen, 4 to 6 L/min, continuously for 5 consecutive days. Each of 48 reservoirs was filled with either tap water (24) or sterile water (24) and cultured daily. All disposable equipment was discarded after the final culture on the fifth day. An aliquot of water was obtained daily from each reservoir and plated to trypticase soy agar pour plates and to a matched trypticase soy broth. Bacterial growth was observed on trypticase soy agar pour plates from 54 (45.0%) of 120 sterile water reservoir cultures and from 38 (31.7%) of 120 tap water reservoir cultures ( p > 0.05). Bacterial growth from the matched trypticase soy broth cultures was observed only from two sterile water reservoirs. The microorganisms identified from the sterile water reservoirs included Enterobacter agglomerans and Serratia and Bacillus spp. The use of tap water for low-flow oxygen humidification was determined to be safe at our hospital by the infection control committee. This procedural change contributed approximately $9000 to the cost reduction efforts of the respiratory therapy department.

Bacterial colonization in humidifying cascade reservoirs after 24 and 48 hours of continuous mechanical ventilation.

We evaluated levels of bacterial colonization in the humidifying cascade reservoirs of 466 mechanical ventilators; 326 reservoirs were cultured after 24 hours and 140 were cultured after 48 hours of continuous mechanical ventilation. Bacterial colonization was absent in 284 (87.1%) of the humidifier reservoirs sampled at 24 hours and 125 (89.3%) of the reservoirs cultured at 48 hours. Levels of bacterial colonization in the remaining humidifiers were low (less than 100 organisms/mL). The median temperature recorded in the reservoir fluid of 30 different ventilators was 50 degrees C (range 40 degrees to 60 degrees C). In vitro seeding of reservoir fluid at 50 degrees C with 10(6) organisms/mL of four different species of nosocomial gram-negative bacilli and Staphylococcus aureus demonstrated rapid killing of all five strains over a 6-hour incubation period, and no significant bacterial aerosols were detected. Rates and levels of bacteria in heated humidifier reservoirs are low and nosocomial pathogens survive poorly at the median reservoir temperature of 50 degrees C. We conclude that the heated humidifier reservoir on a mechanical ventilator is an unlikely source of colonization or bacterial aerosols, and therefore it can be changed every 48 hours with the ventilator tubing.

Bacterial contamination of ambulance oxygen humidifer water reservoirs: A potential source of pulmonary infection

The risk and benefit of oxygen humidification during ambulance transport is unknown. We cultured the water in plastic multiple-use bottles of humidifiers on 30 randomly selected area ambulances during November 1985. There were 22 positive cultures. Potentially pathogenic bacteria (four Pseudomonas maltophilia, three Pseudomonas aeruginosa, one Klebsiella pneumoniae, and one Staphylococcus epidermidis) were found in nine samples. Assuming that the water in ambulance humidifiers should have been sterile, the findings are statistically significant (P less than .01). Because there is no evidence that humidification is of benefit for nonintubated patients receiving oxygen at flow rates of 4 L/min or less when environmental humidity is adequate, we suggest that such patients should receive oxygen without humidification during ambulance transport. All other patients requiring oxygen during ambulance transport should continue to receive humidified oxygen. If a multiple-use humidifier reservoir is to be used, a written policy for its use must be developed and there must be appropriate documentation of compliance with the policy. An alternative is to replace the multiple-use humidifier reservoir with single-use sterile disposable devices, which cost approximately $2.00 per unit.

Bubbling humidifiers produce microaerosols which can carry bacteria.

It is widely held that bubbling humidifiers do not produce microaerosols, although prior studies have resulted in conflicting evidence. We have studied this phenomenon in a clean room using an airborne particle counter and samplers for airborne bacteria. At gas flow rates between 10 and 80 L/min, a Cascade 1 humidifier produced between 460 and 999 water droplets/L humidified gas. Total water volume aerosolized was approximately 10(-8) ml/L humidified gas. Seventy-three percent of the particles had diameters between 1 and 5 microns. With the reservoir containing 6.4 X 10(6) P. aeruginosa/ml, it produced between 2 and 9 P. aeruginosa/L humidified gas. Most of the bacteria were in particles of a size likely to be deposited in the lung. This bacterial carry-over was between 20 and 150 times the amount predicted by multiplication of the water volume aerosolized times the concentration of bacteria in the humidifier reservoir. An Air Life humidifier produced fewer particles which were also of a size likely to be deposited in the lung and, when the reservoir contained P. aeruginosa, it aerosolized bacteria. Wick-type humidifiers did not produce detectable aerosol or bacterial carry-over. Although the clinical significance of these findings has not been established, they provide a rationale for the CDC recommendations for procedures designed to keep bubbling humidifier reservoir water uncontaminated.

The sources of pneumonia in ITU patients.

Much attention has been given to ventilators, respiratory tubing and humidifiers as sources of bacteria causing pneumonias in intensive therapy unit (ITU) patients. However, efficient decontamination and safe storage of ventilators and humidifiers between patients, with frequent changing of respiratory tubing and the use of Chlorhexidine in humidifier reservoirs, are now undertaken in most ITUs. In addition, chest aspiration, which is an important route for bacterial entry to the chest, is performed by trained ITU staff, who are well aware of this danger and wear gloves and use meticulous techniques. As a result, it can be argued that infection of the lungs in ITU patients from these sources and routes has reached an “irreducible minimum.”Unfortunately, many patients in ITUs continue to develop pneumonias. In my own experience patients yielded Pseudomonas in tracheal aspirates as frequently after the introduction of these techniques, together with the insertion of efficient bacterial filters, between the patient and the ventilator in both the inspiratory and expiratory lines, as before their adoption. What other sources and routes of infection of the lungs should be considered?

Humidification of incubators.

The effect of increasing the humidity in incubators was examined in 62 infants of less than 30 weeks' gestation. Thirty three infants nursed in high humidity for two weeks were compared retrospectively with 29 infants from an earlier study who were nursed under plastic bubble blankets or with topical paraffin but without raised humidity. Humidification reduced skin water loss and improved maintenance of body temperature from birth, but did not delay the normal postnatal maturation of the skin. Infants nursed without humidity frequently became hypothermic in spite of a high incubator air temperature. These advantages must be weighed against the finding that overheating was more common and Pseudomonas was more commonly isolated from the infants. It is recommended that incubator humidity is raised for babies under 30 weeks' gestation in the first days of life but meticulous attention should be paid to fluid balance, avoiding overheating, and cleansing of the humidifier reservoir.

Colonisation of the trachea in ventilated patients: What is the bacterial pathway?

It is well known that the trachea of patients undergoing assisted ventilation in intensive therapy units (ITUs) rapidly becomes colonized with bacteria. This is undesirable since bacteria are then advantageously placed to invade the lung parenchyma. In addition, the results of culture of lung aspirates, which are inevitably contaminated with tracheal organisms, are made more difficult to interpret. The bacteria involved have been shown to originate from several different sources; (Gaya, 1974; Stoddart, 1975) e.g. respiratory equipment, nasogastric feeds, other patients and endogenous sources such as faeces and other colonized sites in the patient. Bacteria from these sources have been found on the hands of staff and other vehicles of spread, but the route of entry into the trachea is less clear. There are two potential ‘final common pathways’ by which bacteria may enter the trachea, (1) through the airway of the endotracheal or tracheostomy tube via the inhaled air or during lung suction, (2) via contaminated oropharyngeal or gastric secretions passing between an endotracheal tube and the wall of the trachea. Bacterial passage through a tracheostomy wound is probably unimportant, since endotracheal tubes are more commonly used and wounds receive protection from infection. This article examines the two ‘final common pathways’ in an attempt to demonstrate the potential importance and consequences of the second route for tracheal colonization in patients undergoing assisted ventilation. The air delivered to the patient may carry bacteria entrapped from a contaminated part of the respiratory equipment or from the air of the unit itself. However, much emphasis is placed on preventing bacterial contamination of respiratory equipment and ventilators are generally decontaminated after use by efficient processes (Lumley, 1976). Humidifier reservoirs are usually filled with a disinfectant at an appropriate concentration and are stored dry between patients. Respiratory tubing is changed frequently (Gaya, 1974). Less work has been done on the bacterial contamination of the air of ITUs, but common experience and the available evidence (Lowbury et al., 1969; Teres, 1973) tends to indicate that it is of little importance. In any case, in cross-infection episodes, the pattern of spread of tracheal isolates between patients is typical of contact spread. Contamination of inspired air from retrograde movement of tracheal secretion into the inspiratory line could only occur after tracheal colonization. The relative unimportance of the air and respiratory equipment as a pathway