Critically unwell patients in Intensive Care have a decreased ability to effectively clear secretions. High secretion load is a major risk factor in the failure of tracheal extubation failure and the requirement for reintubation. Extubation failure is a predictor of poor outcome independent of the severity of the underlying illness. Nebulisation of isotonic saline can be employed to manage secretions by reducing the secretion viscosity and facilitating clearance of respiratory sections during tracheal suction.

Standard jet nebulisers have been the mainstay of respiratory section management therapy in critical care since the early 1990s. A more recent development has been the vibrating mesh nebuliser. There is evidence of improved humidification and reduced water particle size and theoretically better transfer to the distal airways.

1.2 Rationale The vibrating mesh nebuliser (Aerogen technology) may be superior to standard nebuliser technology.

1.3 Study hypothesis Improved secretion management with reduced tenacity of respiratory sections and potentially improved lung physiology secondary to improved humidification or reduced size of nebulised particles? 2. STUDY OBJECTIVES

Primary Endpoint Pourability of respiratory secretions (As assessed by the Qualitative Sputum Assessment Tool)

(The QSA score will assess quantity, quality/stickiness/density and colour/appearance of secretions and is described and validated in the literature3,4)

Secondary endpoints

• Volume of secretions (increased or decreased may be beneficial)

• Work of breathing

• Airway resistance

• Number of number of additional nebulised doses of saline or other drugs administered during the study period

• Ease of sampling, in the opinion of treating nurse

• Frequency of requiring changing the HME(heat and moisture exchange) filter

• Length of time on ventilator

• Length of stay in ICU/HDU(Intensive care unit/high dependancy unit)

• ICU Mortality

  3. STUDY DESIGN 3.1 Study Population

A total of 60 patients will be recruited to the study. Each patient will be randomised to receive:

Continuous nebulisation of 0.9% normal saline using the Aerogen Solo Nebuliser (50mls/24h via a syringe feed set) OR

Intermittent nebulisation of 0.9% normal saline using the Aerogen Solo Nebuliser (5mls, 6 hourly) OR

Intermittent standard nebulisation of 0.9% normal saline using the Intersurgical Cirrus 2 self-sealing Jet Nebuliser (5 mls, 6 hourly)

Inclusion Criteria:

• Patient aged 18-80 years at time of recruitment to study
• Ventilated via an endotracheal tube or tracheostomy with an HME filter in the circuit
• Secretion load defined as patient requiring suctioning at least 2 times in the 6 hours prior to recruitment
• Sputum viscosity with grades 1 to 3 pourability in the Qualitative Sputum Assessment tool
• Not yet received saline nebulisation in the 6 hours prior to recruitment
• Likely to be ventilated via an endotracheal tube or tracheostomy for at least 3 days in the opinion of the treating clinician

Exclusion Criteria:

• Pregnancy
• Pulmonary embolus
• Heart Failure (NYHA Grade III/IV)
• Clinical evidence of frank pulmonary oedema
• Cardiovascular instability (systolic BP ≤75 or heart rate ≥140)