Impact of Humidification and Nebulization During Expiratory Limb Protection: An Experimental Bench Study

Abstract

BACKGROUND: Different filtering devices are used during mechanical ventilation to avoid dysfunction of flow and pressure transducers or for airborne microorganisms containment. Water condensates, resulting from the use of humidifiers, but also residual nebulization particles may have a major influence on expiratory limb resistance. OBJECTIVES: To evaluate the influence of nebulization and active humidification on the resistance of expiratory filters. METHODS: A respiratory system analog was constructed using a test lung, an ICU ventilator, heated humidifiers, and a piezoelectric nebulizer. Humidifiers were connected to different types of circuits (unheated, mono-heated, new-generation and old-generation bi-heated). Five filter types were evaluated: electrostatic, heat-and-moisture exchanger, standard, specific, and internal heated high-efficiency particulate air [HEPA] filter. Baseline characteristics were obtained from each dry filter. Differential pressure measurements were carried out after 24 hours of continuous in vitro use for each condition, and after 24 hours of use with an old-generation bi-heated circuit without nebulization. RESULTS: While using unheated circuits, measurements had to be interrupted before 24 hours for all the filtering devices except the internal heated HEPA filter. The heat-and-moisture exchangers occluded before 24 hours with the unheated and mono-heated circuits. The circuit type, nebulization practice, and duration of use did not influence the internal heated HEPA filter resistance. CONCLUSION: Expiratory limb filtration is likely to induce several major adverse events. Expiratory filter resistance increase is due mainly to the humidification circuit type, rather than to nebulization. If filtration is mandatory while using an unheated circuit, a dedicated filter should be used for < 24 hours, or a heated HEPA for a longer duration.

Aerosol therapy in intensive and intermediate care units: prospective observation of 2808 critically ill patients

“…One-third of aerosols (n = 1502) were administered in intubated patients with no filter protecting the expiratory block. No dysfunction was documented over the 2-week study period, in part due to the predominant delivery of bronchodilators and corticosteroids; nevertheless, given the very severe complications reported, including pneumothorax and cardiac arrest, additional educational efforts are warranted in order to promote better practice [10,14,[28][29][30]. Regarding efficacy, unlike for bronchodilator therapy, nebulization/ventilation set-up is a key factor for success of inhaled anti-infectious therapy, in particular when aiming to treat pneumonia, which was the case for 73 % of anti-infective aerosol deliveries [31].…”

Ventilator-Integrated Jet Nebulization Systems: Tidal Volume Control and Efficiency of Synchronization

“…When the nebulizer is placed close to the Y-piece, medication nebulized during expiration is cleared mostly through the expiratory limb of the ventilator and thus is lost for the patient and has the potential to damage the expiratory flow meter and/or obstruct filters protecting this flow meter. 11,12 To deliver a higher amount of drug to the patient, it may be desirable to reduce the drug loss during expiration. 13,14 The Galileo and G5 ventilators are designed to synchronize nebulization with inspiration rather than with insufflation (Fig.…”

Nebulized Heparin in Burn Patients with Inhalation Trauma—Safety and Feasibility

“…The combined use of an active humidification system with a filter on the expiratory limb of the ventilator circuit may result in life-threatening obstruction of the filter [11,12]. The expiratory resistance can increase due to filter saturation with water condensates [12]. This risk can be reduced by the use of specific expiratory filters [10].…”

“…This risk can be reduced by the use of specific expiratory filters [10]. Other possible complications related to a nebulization procedure include the occurrence of mucus plugging in the artificial airways and clogging of the expiratory limb of the ventilator circuit due to drug precipitation [11][12][13][14].…”