Fig. 2

F-V curves using tracheal catheters of three different sizes. Reproducibility of the F-V curves was good using any size catheter (a). Peak expiratory flow rate was not affected by the size of the tracheal catheter (b). FVC was not affected by the size of the tracheal catheter (c). When a 14G catheter was used, the peak flow was delayed (c). Mean ± SD. $P < 0.05 versus 12G, *P < 0.05 versus 13G. All four phases of the F-V curve—initial steep increase (first), steep decrease (second), slow decrease (third), and steep decrease (fourth)—are depicted in a for the 12G catheter