Thorax 59:694-698 doi:10.1136/thx.2003.016949
  • Respiratory physiology

Effects of breathing pattern and inspired air conditions on breath condensate volume, pH, nitrite, and protein concentrations

  1. J B McCafferty,
  2. T A Bradshaw,
  3. S Tate,
  4. A P Greening,
  5. J A Innes
  1. Respiratory Unit, Western General Hospital and University of Edinburgh, Edinburgh, UK
  1. Correspondence to:
    Dr J McCafferty
    Respiratory Unit, Western General Hospital, Crewe Road, Edinburgh EH2 4XU, UK;
  • Received 5 October 2003
  • Accepted 14 April 2004


Background: The effects of breathing pattern and inspired air conditions on the volume and content of exhaled breath condensate (EBC) were investigated.

Methods: Total exhaled water (TEW), EBC volume, pH, nitrite and protein concentrations were measured in three groups of 10 healthy subjects breathing into a condenser at different target minute ventilations (Vm), tidal volumes (Vt), and inspired air conditions.

Results: The volumes of both TEW and EBC increased significantly with Vm. For Vm 7.5, 15 and 22.5 l/min, mean (SD) EBC was 627 (258) μl, 1019 (313) μl, and 1358 (364) μl, respectively (p<0.001) and TEW was 1879 (378) μl, 2986 (496) μl, and 4679 (700) μl, respectively (p<0.001). TEW was significantly higher than EBC, reflecting a condenser efficiency of 40% at a target Vm of 7.5 l/min which reduced to 29% at Vm 22.5 l/min. Lower Vt gave less TEW than higher Vt (26.6 v 30.7 μl/l, mean difference 4.1 (95% CI 2.6 to 5.6), p<0.001) and a smaller EBC volume (4.3 v 7.6 μl/l, mean difference 3.4 (95% CI 2.3 to 4.5), p<0.001). Cooler and drier inspired air yielded less water vapour and less breath condensate than standard conditions (p<0.05). Changes in the breathing pattern had no effect on EBC protein and nitrite concentrations and pH.

Conclusion: These results show that condensate volume can be increased by using high Vt and increased Vm without compromising the dilution of the sample.


  • Funded by Chest, Heart and Stroke Scotland, UK