COPD flow rate and frequency

Continuous recordings of flow, esophageal pressure (Pes), and chest volume (the sum of rib-case and abdominal motion) in a patient with COPD receiving assist-control ventilation with a constant tidal volume. As flow increased from 30 to 60 and 90 L/min (from right to left), frequency increased from (18 to 23 and 26 breaths/min, respectively), Auto-PEEP decreased (from 15.6 to 14.4 and 13.3 cm H2O, respectively) and end-expiratory chest volume also fell. Increases in flow from 30 L/min to 60 and 90 L/min also led to decreases in the swings in Pes from 21.5 to 19.5 and 16.8 cm H2O, respectively.