Fig. 1.

Resistance (cmH₂O·ml⁻¹·s) vs. concentration of inhaled acetylcholine (mg/ml). Treatment with High continuous positive airway pressure (High CPAP; 6 cmH₂O) for 4 days followed by Low CPAP (0 cmH₂O) for 1 day (thin dashed line and open circles) produced a persistent reduction in airway responsiveness compared with Low CPAP for 5 days (solid black line and closed diamonds). Animals treated with Nocturnal High CPAP for 4 days (thick dashed line and open squares) had reduced airway responsiveness compared with animals treated with Low CPAP for 5 days (solid black line and closed symbols). There was no difference in airway responsiveness for the 2 groups treated with High CPAP.