Can Humidifier Reservoir Bacteria Colonize the Circuit During Mechanical Ventilation?

Background:Although the circuit condensate, an ideal bacterial reservoir, may flow into the humidifier reservoir (HR), no study has investigated if HR-colonized bacteria colonize other circuit locations with airflow. Therefore, the objective of this study was to explore if bacterial growth in the HR leads to bacterial colonization in the ventilator circuit. Methods: A randomized controlled experiment was performed in a public tertiary hospital in Guangdong Province, China. In vitro mechanical ventilation models (n = 60), divided into sterile water samples (n = 30) and broth samples (n = 30), were established. Sterile water was used for humidification in the ventilation models. The sterile water group contained either Acinetobacter baumannii (n = 15) or Pseudomonas aeruginosa (n = 15) in humidifier water. The broth group was similar to the sterile water group, but brain heart infusion broth was added to the HR. After 24, 72, and 168 h of continuous ventilation, bacteria in the humidifier water and at different circuit locations were sampled and cultured, and the results were analyzed by the Chi-square test. The difference in bacterial concentration at the HR outlet was analyzed by the F test, and P < 0.05 was considered statistically significant.Results:Bacterial culture results of the sterile water samples were negative. Bacteria in the humidifier water continued to proliferate in the broth group, and the bacterial concentration at different times was not significantly different (P > 0.05). With prolonged ventilation, the bacterial concentration at the HR outlet increased (P < 0.05). During continuous ventilation, no bacterial growth occurred at 10 cm from the HR outlet and the Y-piece of the ventilator circuit. The bacterial concentration at the HR outlet was higher in the P. aeruginosa group than in the A. baumannii group (P < 0.05).Conclusions:Sterile water in the HR was not conducive to bacterial growth. Although bacteria grew in the HR and could reach the HR outlet, colonization of other circuit locations was unlikely.

The role of bacterial colonization of ventilator circuit in development of ventilator associated pneumonia in ICU of Medical Center Hospital in Tripoli, Libya

Introduction: In mechanically ventilated patients, ventilator-associated pneumonia (VAP) is a major cause of prolonged hospitalization with increased morbidity and mortality. There is a lack of studies on the relationship between bacterial colonization of the ventilator circuit (VC) and VAP. This study aimed to investigate the role of bacterial colonization of VC in the development of VAP and identify antibiotic susceptibility trends for isolated strains. Methods: A prospective study of the bacterial culture has been performed between February 2021 to March 2021 on a total of 100 mechanically ventilated patients, (n =50) samples have been obtained from patient's lower respiratory tract (LRT) and (n =50) were taken from mechanical ventilator equipment VC. Paired samples of bacteria isolated from VC and LRT, where VC was colonized before LRT. Results: A total of 58 samples were cultured positively, while 42 specimens showed negative bacterial growth. However, there was no substantial difference in comparing between the bacterial colonization of the ventilator system and the patient samples. Most isolated organisms were gram-negative bacteria which were found in the ventilator circuit with 26 (68.4%), and 14 (70%) in patient’s LRT. Gram-positive was detected in 12 (31.6%) and 6 (30%) of the ventilator circuit, and patient's LRT, respectively. The predominant bacterial type was Acinetobacter baumannii organism at the VC with 10 (26.3%) and LRT at 4 (20%) followed by Klebsiella pneumoniae (8 (21.1%) in VC and 4 (20%) in LRT). Moreover, A. baumannii showed a full resistance to amoxicillin and the first generation of cephalosporins, while the other bacterial types were resistant to the most antibiotics used in this research. Conclusions: Bacterial colonization of ventilator circuit VC is a significant cause of VAP development in mechanically ventilated patients. Preventive strategies for the early detection and decontamination of contaminated VC can play a crucial role in ventilator-associated pneumonia prevention.

Nebuliser Type Influences Both Patient-Derived Bioaerosol Emissions and Ventilation Parameters during Mechanical Ventilation

COVID-19 may lead to serious respiratory complications which may necessitate ventilatory support. There is concern surrounding potential release of patient-derived bioaerosol during nebuliser drug refill, which could impact the health of caregivers. Consequently, mesh nebulisers have been recommended by various clinical practice guidelines. Currently, there is a lack of empirical data describing the potential for release of patient-derived bioaerosol during drug refill. This study examined the release of simulated patient-derived bioaerosol, and the effect on positive end expiratory pressure during nebuliser refill during mechanical ventilation of a simulated patient. During jet nebuliser refill, the positive end expiratory pressure decreased from 4.5 to 0 cm H2O. No loss in pressure was noted during vibrating mesh nebuliser refill. A median particle number concentration of 710 particles cm−3 above ambient was detected when refilling the jet nebuliser in comparison to no increase above ambient detected when using the vibrating mesh nebuliser. The jet nebuliser with the endotracheal tube clamped resulted in 60 particles cm−3 above ambient levels. This study confirms that choice of nebuliser impacts both the potential for patient-derived bioaerosol release and the ability to maintain ventilator circuit pressures and validates the recommended use of mesh nebulisers during mechanical ventilation.

Safety and Feasibility of a Novel Protocol for Percutaneous Dilatational Tracheostomy in Patients with Respiratory Failure due to COVID-19 Infection: A Single Center Experience

Introduction. The rapidly spreading Novel Coronavirus 2019 (COVID-19) appeared to be a highly transmissible pathogen in healthcare environments and had resulted in a significant number of patients with respiratory failure requiring tracheostomy, an aerosol-generating procedure that places healthcare workers at high risk of contracting the infection. Instead of deferring or delaying the procedure, we developed and implemented a novel percutaneous dilatational tracheostomy (PDT) protocol aimed at minimizing the risk of transmission while maintaining favorable procedural outcome. Patients and Methods. All patients who underwent PDT per novel protocol were included in the study. The key element of the protocol was the use of apnea during the critical part of the insertion and upon any opening of the ventilator circuit. This was coupled with the use of enhanced personnel protection equipment (PPE) with a powered air-purifying respirator (PAPR). The operators underwent antibody serology testing and were evaluated for COVID-19 symptoms two weeks from the last procedure included in the study. Results. Between March 12th and June 30th, 2020, a total of 32 patients underwent PDT per novel protocol. The majority (80%) were positive for COVID-19 at the time of the procedure. The success rate was 94%. Only one patient developed minor self-limited bleeding. None of the proceduralists developed positive serology or any symptoms compatible with COVID-19 infection. Conclusion. A novel protocol that uses periods of apnea during opening of the ventilator circuit along with PAPR-enhanced PPE for PDT on COVID-19 patients appears to be effective and safe for patients and healthcare providers.

Evaluating cross contamination on a shared ventilator

BackgroundDisasters have the potential to cause critical shortages of life-saving equipment. It has been postulated that during patient surge, multiple individuals could be maintained on a single ventilator. This was supported by a previous trial that showed one ventilator could support four sheep. The goal of our study is to investigate if cross contamination of pathological agents occurs between individuals on a shared ventilator with strategically placed antimicrobial filters.MethodsA multipatient ventilator circuit was assembled using four sterile, parallel standard tubing circuits attached to four 2 L anaesthesia bags, each representing a simulated patient. Each ‘patient’ was attached to a Heat and Moisture Exchange filter. An additional bacterial/viral filter was attached to each expiratory limb. ‘Patient-Lung’ number 1 was inoculated with an isolate of Serratia marcescens, and the circuit was run for 24 hours. Each ‘lung’ and three points in the expiratory limb tubing were washed with broth and cultured. All cultures were incubated for 48 hours with subcultures performed at 24 hours.ResultsWashed cultures of patient 2, 3 and 4 failed to demonstrate growth of S. marcescens. Cultures of the distal expiratory tubing, expiratory limb connector and expiratory limb prefilter tubing yielded no growth of S. marcescens at 24 or 48 hours.ConclusionBased on this circuit configuration, it is plausible to maintain four individuals on a single ventilator for 24 hours without fear of cross contamination.