Assessment of airflow obstruction from tidal breathing expiratory flow recordings in patients with chronic obstructive pulmonary disease

The research presented in this thesis focuses on the identification and utilisation of novel indices measured from tidal breathing expiratory flow patterns to assess airflow obstruction in adults. The work is in two parts, firstly the development of the data collection protocol and the identification of suitable indices and secondly the evaluation of the reproducibility of these indices and their comparison with conventional indices and reported symptoms. The current routine method used to assess airflow obstruction is the measurement of FEV], however this test requires patient understanding of the test procedure and maximal effort to produce satisfactory results. Furthermore, forced expiration is not a breathing manoeuvre that people perform in every day life. The usefulness of FEVi in assessing reversibility to bronchodilation was studied in a retrospective study which showed that 41% of patients who were identified as non-reversible by FEVi criteria showed reversibility of forced or relaxed vital capacity, indicating that FEVi does not detect all the physiological effects of bronchodilators. Iftidal breathing is measured, a number of the disadvantages of FEVi are overcome. It is effort-independent, requires no learning of special breathing manoeuvres on the patient's part and so can be performed even in acutely breathless patients. A method of recording tidal breathing patterns was developed in which the type of equipment and the measurement protocol was comfortable for the subject, applicable to the routine clinical setting and impacted minimally on the tidal breathing pattern. A five-minute collection time was chosen, recorded after a two-minute acclimatisation period. A method of producing an averaged breath was developed from which a number of novel tidal indices could be measured. After analysis of these indices in pilot studies, three indices, (TBEV i (volume of air exhaled in the first second of a tidal breath), TPEF (peak tidal expiratory flow rate) and EF25 (expiratory flow at end tidal volume plus 25% end tidal volume) were identified which changed consistently following bronchodilators and these were subsequently studied in more depth. Each of these indices correlated with specific conductance (sGaw) at baseline and showed significant increases after bronchodilator but not after placebo treatment in patients known to have reversible airflow obstruction. Placebo treatment in patients known to have reversible airflow obstruction. For the tidal breathing method to be clinical acceptable it had to be shown to be reproducible and ideally to correlate with patient perceived breathlessness. The final section of the thesis reports studies of reversibility of these measures. Reproducibility was similar to conventional indices of airway obstruction. In summary this thesis describes development of a method for the measurement and analysis of tidal breathing expiratory flow patterns, which yields consistent and physiologically plausible changes in defined tidal indices following bronchodilator treatment.

Grantor dc:publisher

The University of Edinburgh

Year dc:date.issued

2003

Author dc:creator

• Montgomery, Joanne Margaret

Handle dc:identifier.uri

http://hdl.handle.net/1842/35389

OAI identifier oai:identifier

oai:era.ed.ac.uk:1842/35389