Article Figures & Data
Figures
- Fig. 1.
Mechanical lung design. A pressure transducer was fitted 2.5 cm from the Y-piece during pressure measurements. During retrograde CO2 entrainment measurements, the pressure transducer was removed and the gas analyzing line was inserted at 76 cm from the Y-piece, and positioned at locations of interest during the different experiments. Y = Y-piece. ETT = endotracheal tube.
- Fig. 2.
Inverse effects of mean airway pressure (P̄aw) and ΔP on inspiratory limb negative pressure. Increasing P̄aw reduces negative pressure (other settings: ΔP 90 cm H2O, frequency 7 Hz, bias flow 30 L/min, inspiratory time 33%). Raising ΔP increases negative pressure (other settings: P̄aw 34 cm H2O, frequency 7 Hz, bias flow 30 L/min, inspiratory time 33%).
- Fig. 3.
Effect of inspiratory limb negative pressure on retrograde CO2 entrainment. Retrograde CO2 entrainment increases (at 51 cm from the Y-piece) when more negative pressure is generated by either reducing mean airway pressure (P̄aw) or raising ΔP. The data points represent the means of duplicate experiments (measurements varied ≤ 1 mm Hg).
- Fig. 4.
Inspiratory limb CO2 pressure and distance of CO2 entrainment at baseline settings in the mechanical lung and swine models. The high-frequency oscillatory ventilation (HFOV) settings were: mean airway pressure P̄aw 34 cm H2O, ΔP 90 cm H2O, frequency 7 Hz, bias flow 30 L/min (without cuff leak), inspiratory time 33%. Despite maximal cuff inflation, there was a persistent 10 mm Hg CO2 leak within the swine's oropharynx.
- Fig. 5.
Effect of mean airway pressure (P̄aw) adjustments on retrograde CO2 entrainment. The P̄aw was manipulated by either the mean pressure adjustment or by bias flow (17–60 L/min). Adjustments were made relative to baseline settings: P̄aw 34 cm H2O, ΔP 90 cm H2O, frequency 7 Hz, bias flow 30 L/min, inspiratory time 33%. Mechanical lung data were obtained at 51 cm from the Y-piece, and swine data at 25 cm from the Y-piece.
- Fig. 6.
Effect of bias flow manipulations at constant mean airway pressure P̄aw on retrograde CO2 entrainment. Data were obtained at 51 cm from the Y-piece. Other high-frequency oscillatory ventilation settings remained at baseline: mean airway pressure P̄aw 34 cm H2O, ΔP 90 cm H2O, frequency 7 Hz, inspiratory time 33%.
- Fig. 7.
Effect of ΔP manipulations on retrograde CO2 entrainment. Data were obtained 51 cm from the Y-piece in the mechanical lung model and 25 cm from the Y-piece in the swine model. Other HFOV settings remained at baseline: mean airway pressure 34 cm H2O, bias flow 30 L/min, frequency 7 Hz, inspiratory time 33%.
- Fig. 8.
Effect of respiratory frequency manipulations on retrograde CO2 entrainment. Data were obtained at 51 cm from the Y-piece in the mechanical lung model and at 25 cm from the Y-piece in the swine model. Other HFOV settings remained at baseline: mean airway pressure 34 cm H2O, ΔP 90 cm H2O, bias flow 30 L/min, inspiratory time 33%.
