The use of normal saline instillation as part of endotracheal suction in mechanically ventilated patients: a scoping review

Background The use of saline instillation (SI) before endotracheal suction (ETS) in mechanically ventilated patients remains contentious, with reasons for SI use/non-use varying amongst ICU clinicians. Methodological heterogeneity in the existing literature makes drawing firm conclusions surrounding SI practice, informing evidenced based practice guidelines and clinical recommendations challenging.

Objective To report the extent, scope and nature of the existing literature on the use of SI during ETS and to identify research gaps.

Data sources A systematic search was conducted of the following databases: ‘EMBASE’, ‘MEDLINE’, ‘Pedro’, ‘Cochrane’, ‘EMCARE’, ‘PubMed’ and ‘CINAHL’.

Study selection Inclusion criteria: primary research, reporting on SI use during ETS on critical care, published in English between January 2013 and October 2025.

Synthesis methods A charting form was developed and piloted to extract: Author, study demographics and design; aim; sampling technique/sample size; population; eligibility criteria; control/intervention; outcome measures and results.

Results Ten studies were included. Five were interventional, primarily focusing on the effects of SI on patient physiological outcomes; only one conducted sputum analysis. Five studies were observational and explored ICU clinicians’ beliefs and perceptions surrounding SI use, most commonly justified in the context of managing thick or viscous secretions.

Limitations Non-English language, review articles and grey literature were excluded.

Conclusions There is limited contemporary research investigating the effects of SI during ETS. Literature remains heterogenous with a gap in primary research objectively looking at the efficacy of SI during ETS on secretion clearance i.e., secretion yield, the primary reason ICU clinicians utilise SI, highlighting a future research opportunity.