FILTRex is a single-centre, controlled, randomised, prospective, non-inferiority clinical trial to compare the efficiency and safety of prolonged (72-hours) versus standard (24-hours) duration of use for Heat and Moisture Exchange (HME) filters in adult mechanically ventilated critically ill patients

Rationale: Ventilator-associated pneumonia (VAP) is the most common hospital-acquired infection (HAI) in the intensive care unit (ICU), and its impact is very high in terms of morbidity, length of hospital stay and overall costs. Minimising manipulation and disconnection of the ventilator circuit by reducing the frequency of HME filter exchange may lower the risk of its secondary contamination, hence the incidence of VAP, while maintaining its efficacy in terms of sufficient humidification of the inhaled gas mixture and safety in terms of no or minimal change in resistance to airflow.

Aim: To test the effectiveness and safety of prolonged (72-hour exchange interval) use of a single HME.

Design: Prospective, single-centre, parallel-group randomised controlled trial. Subjects: ICU patients (general ICU)

Treatment in the intervention group: HME filter exchange every 72 hours

Control group: Standard-of-care: daily HME filter exchange

Primary outcome:

1. Presence of HME-associated adverse events (a composite endpoint of endotracheal tube occlusion or nosocomial tracheobronchitis or pneumonia).
2. The cumulative incidence of lower respiratory tract microbial colonisation analysed by the Kaplan-Maier method, censored in the case of ICU discharge or extubation > 24h.

Secondary and exploratory outcomes: Differences in the relative risk of infection-related ventilator-associated complications, antibiotics (ATB) exposure analysis, length of ICU stay in days (time frame: three months), number of ventilator-free days (time frame: 28 days); differences in the incidence of endotracheal tube occlusion necessitating reintubation between individual groups, differences in airway resistance, humidity delivered to the patients and efficacy of HMEs between groups

Inclusion Criteria:

1. Age ≥18 years
2. In-patient in ICU and expected to stay > 3 days
3. Mechanical ventilation or imminent need of it; predicted length of mechanical ventilation ≥ 72h
4. Clinical Pulmonary Infection score (CPIS) less than six at the baseline 5 No history and symptoms of aspiration at the baseline

Exclusion Criteria:

1. Suspected pulmonary infection on admission and in the first 48 hours of mechanical ventilation
2. Pregnancy
3. Acute respiratory distress syndrome
4. Body temperature < 32°C
5. Airway bleeding or other contraindications for the use of HME
6. An early decision of treatment withdrawal

Due to the nature of the intervention, nurses can't be blinded to allocation (the frequency of HME exchange), but are strongly inculcated not to disclose the allocation status of the participant at the follow-up assessments. As the ICU is paperless and fully computerised, the data in the computer can be acquired and analysed by the researchers without having access to information about the allocation.