Abstract
Introduction: Dynamic hyperinflation (DH) is thought to be an important clinical feature in patients with COPD, but is difficult to measure.
Aim: To investigate DH in patients with COPD referred for bronchoscopic lung volume reduction and to test the feasibility of using metronome paced hyperventilation (MPH).
Methods: DH was measured by MPH using the breath-by-breath method (Oxycon Pro) in a 15-min protocol. After 3 baseline IC maneuvers, 3 MPH tests (40Hz for 60 sec; with 3 min. rest in-between) were performed. Each MPH test was directly followed by an IC maneuver. DH was defined as ΔIC/IC (decrease in IC/baseline IC) and calculated using the average of 3 IC's.
Patients: 29 patients with severe emphysema, Gold-IV (n=15): FEV1 23%pred (±4.9), Gold-III (n=9): FEV1 37%pred (±4.7) and Gold-II (n=5): FEV1 51%pred (±1.3) were tested. For Gold-IV RV was 239% (±55), TLCbox 136%pred (±18), IC/TLC-He 25% (±3) and 6MWT 340m (±62). For Gold-II/III RV was 189%pred (±70), TLCbox 134%pred (±15), IC/TLC-He 36% (±11) and 6MWT 413m (±84).
Results: All patients tolerated the MPH very well. IC variability was 4.6% (±3.0), and 8.6% (±4.4) after MPH. VE reached 28.8L/min (±12.6), calculated maximal VE (FEV1*37.5) was 34.5L/min (±15.5). MPH frequency was 39.7Hz (±1.4). For the Gold-IV patient group the IC of 1.83L (±0.47) decreased to 1.21L (±0.42) after MPH with a ΔIC/IC of 34% (±12). In Gold-II/III IC decreased from 2.39L (±0.93), to 1.79L (±0.63) with a ΔIC/IC of 23% (±12). In the overall group ΔIC/IC correlated with TLC-He (r=0.45, p=0.03) and FEV1 (r=-0.38, p=0.04).
Conclusion: Measuring DH is feasible using MPH, and can be used in the routine clinical setting. DH is significantly present in patients with COPD and increases with disease severity.
- © 2011 ERS