Table 2
From: Criteria for enhancing mucus transport: a systematic scoping review
Increase Mucus Transport | Decreased Mucus Transport | No effect on Mucus Transport |
Physiological factors • Increase temperature 0 - 37 °C [4] • “tidal breathing”/Cyclic compressive stress to lung [14] • Increase in peak inspiratory flow (PIF) [15] • Increase in expiratory – inspiratory flow difference (E-I) (achieved by increased duty cycle (Ti/Ttot) and PEEP) [15, 16] • Expiratory flow bias [15] and increased PEFR [17] • Cough - Cough clearance (CC) increases with: decreased viscosity, spinnability and adhesivity of mucus [18]; more elastic cohesive mucus [19]; increased peak flow rate [20] and increased cross-sectional area occupied by longitudinal loss of cilia [21]; HFO 25 – 68 Hz [19]; Head-up position 0 - 45° [19] Interventions/equipment • Heat moisture exchanger (HME) presence [22] • High frequency chest wall compression (HFCW) or oscillation (11-15 Hz, peaking at 13 Hz) [23,24,25,26,27] • Hard manual rib cage compression (resulting in increase peak expiratory flow (PEF) and increase mean expiratory flow (MEF) and increase in MEF – MIF (mean expiratory flow – mean inspiratory flow) with head up 20-30° [28] • Percussion energy on chest wall of 25-30 Hz – optimal with head down 60° and 60° head up [29] • High-frequency oscillation with expiratory peak flow bias [25, 30] • HFO with head up 0-45° [19] • Head down tilt of 5° [31] • Controlled coughing – short-term benefit [32] | Physiological factors • Decreased temperature 37° - 25 °C [4, 33, 34] • Lower air humidity (9 g water/m3) [35] • Bronchial blood flow stopped [36] • Increased mucus viscosity [17] • Diminished cough: CC decreases with increased viscosity [18] and increased elasticity more than viscosity [20] | Physiological factors • Head flexion or extension [37] Interventions/equipment • Commercial oscillator (40 Hz) [27] • Ventilation at low volume, high volume, high pressure [38] • Positioning upright or head down tilt 25° [39] • Forced expiration [40] |