Supplementary Material for: Assessment of Bronchial Obstruction Using Lateral Pressure Measurement during Bronchoscopy

<b><i>Background:</i></b> In patients with bronchial obstruction estimating the location of the maximal obstruction is crucial for guiding interventional bronchoscopy. However, flow-volume curves cannot discriminate between the right and left lungs. <b><i>Objectives:</i></b> The aim of this study was to physiologically evaluate bronchial obstruction during interventional bronchoscopy. <b><i>Methods:</i></b> We prospectively measured lateral airway pressure (P_lat) at either side of the obstruction using a double-lumen catheter (pressure-pressure [P-P] curve) simultaneously to assess the degree of bronchial obstruction in 22 patients. The shape of the P-P curve was assessed to confirm the site of maximal obstruction. <b><i>Results:</i></b> In the experimental study, P_lat was uniform between both bronchi in the normal model. For the unilateral and bilateral obstruction models, a phase shift was only seen for the more obstructed side. In healthy subjects, the angle of the P-P curve was close to 45° and linear in shape. In patients with bronchial obstruction, the angle was much smaller but approached 45° after the bronchoscopic procedure. The degree of bronchial obstruction was significantly correlated with the angle of the P-P curve (<i>r</i> = –0.51, <i>p</i> &lt; 0.01). Dyspnea significantly increased when the airway lumen was obstructed by more than 60% (<i>p</i> &lt; 0.0001), and when the P-P curve appeared loop-shaped (<i>p</i> &lt; 0.01). <b><i>Conclusions:</i></b> The shape of the P-P curve could be used to detect the site of maximal obstruction for the optimal positioning of the stent and assess the need for additional procedures in real time in patients with<i></i> bronchial obstruction.