Figure 1.

Examples of routine methods of Respiratory mechanics Measurements for AHR: each panel illustrates animal instrumentation, airway measurement (s) and presence of mechanical or spontaneous ventilation. (A) Airway Pressure Time Index: APTI measures the tracheal pressure response to MCh in a mouse to calculate an aggregate change in respiratory system impedance (Levitt and Mitzner, 1988). (B) Flow Plethysmography: Flow and tracheal pressure (P_tr) signals derived from a flow-plethysmograph and tracheal cannula are used to calculate Rrs or RL depending on whether transrespiratory or transpulmonary pressure is measured (Amdur and Mead, 1958; Waldron and Fisher, 1988). (C) End-Inflation Occlusion: This technique relies on a purpose built ventilator to deliver and hold known inflation volumes and measure the resultant pressure peak and plateau pressures to calculate Rrs and Crs (Ewart et al., 1995; Volgyesi et al., 2000). Ventilators may be lab constructed or use a commercial product (Volgeysi ventilator). (D) Forced Oscillation Technique: The FOT method relies on a purpose built ventilator requiring sophisticated software for the control of volume perturbations and analysis of generated pressure, volume and flow signals. In brief, ventilator housed pistons generate a complex frequency perturbation in the volume signal administered to mice. The lung response is measured as pressure from which lung impedance and other variables are calculated. Current use applications in the literature appear to be restricted to a commercially built ventilator (Scireq®flexivent).