Cough is a key airway protective mechanism requiring coordinated neuromuscular function. Peak cough flow (PCF) is a simple, non-invasive measure widely used to assess cough effectiveness and guide clinical decisions. Current ATS/ERS guidelines recommend measuring PCF in a seated position using a mouthpiece with a nose clip; however, this setup is not always feasible in clinical practice. Some patients cannot maintain posture or ensure an adequate mouthpiece seal, making a facial mask a potential alternative. The influence of body position and interface on PCF measurements remains unclear, with limited evidence from randomized crossover studies.

This study aims to evaluate the effects of body position (sitting vs standing) and measurement interface (mouthpiece vs facial mask) on PCF in healthy young adults. In a randomized within-subject crossover design, participants perform PCF measurements under four conditions (Sit-Mask, Stand-Mask, Sit-Mouthpiece, Stand-Mouthpiece) during a single session. The findings will help inform more flexible and standardized PCF assessment procedures in clinical practice.

Cough is an essential protective mechanism that requires intact neuromuscular function and precise coordination across the inspiratory, compressive, and expulsive phases. Peak cough flow (PCF) is a simple, non-invasive measure, widely used to assess cough intensity and guide clinical decisions. Because of its clinical relevance, standardized procedures are essential. Current ATS/ERS recommendations specify seated testing with a mouthpiece and a noseclip (MP). However, this configuration is not always possible or consistently used in practice. Many patients cannot maintain adequate posture or mouthpiece seal, and a facial mask (FM) may be a feasible alternative. Evidence regarding the effects of posture (sitting vs standing) and interface (MP vs FM) on PCF remains inconsistent, with few studies comparing both factors within the same individuals using a randomized crossover design.

Aims To determine the effects of body position (sitting vs standing) and measurement interface (FM vs MP) on PCF in healthy young adults. We hypothesized that both factors would influence PCF.

Methods This randomized within subject crossover study included healthy, non smoking adults aged 20-30 years. Exclusion criteria were chronic disease, top-level athletic status and any signs of obstruction and/or auscultatory noise (wheezing or stridor) before the trial. Each participant completed four randomized conditions during a single session: Sit-Mask, Stand-Mask, Sit-Mouthpiece, and Stand-Mouthpiece. PCF (L/s) was measured using an ultrasonic spirometer (SpiroScout, Ganshorn). For each condition, participants performed three standardized maneuvers consisting of three tidal breaths, a rapid inspiration to total lung capacity, and a maximal cough; the highest PCF per condition was used for analysis. A two factor repeated measures ANOVA evaluated the effects of posture, interface, and their interaction (α = 0.05).

Inclusion Criteria:

• Healthy adults aged 20 to 30 years
• Non-smoker
• Self-reported good health status
• Able to perform all four randomized cough conditions

Exclusion Criteria:

• Any chronic disease
• Signs of airway obstruction on clinical examination
• Auscultatory abnormalities (wheezing or stridor) prior to testing
• Incomplete participation in all four conditions

Same number for each gender