Efficacy of instilled saline in conjunction with chest physiotherapy on secretion clearance in adults diagnosed with a ventilator acquired pneumonia: a randomised crossover feasibility trial

Introduction: Chest physiotherapy is routinely provided to mechanically ventilated (MV) patients in intensive care units (ICUs) to aid secretion clearance. Physiotherapists may instil saline down the endotracheal tube to aid secretion clearance. However, there is limited evidence and no UK guidelines on the use of saline instillation (SI). Objective: To evaluate the feasibility of a definitive trial examining the efficacy of SI during chest physiotherapy on secretion yield in patients with ventilator-acquired pneumonia (VAP). Methods: A randomised crossover feasibility trial was performed on patients with VAP at a large UK ICU. Patients underwent twice daily chest physiotherapy sessions, alternating between SI vs. Non-SI for three days or until extubation. Primary outcomes were feasibility measures: recruitment, retention, and protocol fidelity. Secondary outcomes included safety outcomes and secretion yield, assessed using two approaches: “adjusted wet sputum weight” and “sputum pellet weight”. Results: Of 32 eligible patients, 94% (N = 30) were recruited, of whom 7% (N = 2) were subsequently withdrawn; 21 (70%) completed all six sessions. No adverse events occurred in SI sessions. The adjusted wet sputum weight appeared to underestimate secretion yield in SI sessions, resulting in a negative median value (−0.49 g; IQR: −2.39, 1.11), which was significantly lower than Non-SI sessions (median: 0.99 g; IQR: 0.26, 2.11; p < 0.001). Analysis using sputum pellet weight reversed the direction of this effect, with medians of 3.49 g (IQR: 1.96, 5.55) vs. 1.70 g (IQR: 0.99, 2.60) for SI vs. non-SI sessions (p < 0.001). Conclusion: A trial of SI during chest physiotherapy for MV patients with VAP would be feasible. However, further validation of a method for processing sputum samples is required before proceeding to a definitive trial. Contribution of the Paper: • A prospective study investigating the efficacy of saline instillation on secretion yield would be safe and feasible. • Adjusted wet sputum weight is not a reliable objective marker to quantify sputum yield. • Development and validation of a method for processing sputum samples to obtain an accurate sputum weight is a research priority.