Inspiratory pressure support prolongs exercise induced lactataemia in severe COPD
- Michael I Polkeyc,
- Peter Hawkinsa,
- Dimitris Kyroussisc,
- Sheric G Elluma,
- Roy Sherwoodb,
- John Moxhama
- aDepartment of Respiratory Medicine, King's College Hospital Campus, Guy's, King's and St Thomas' School of Medicine, London SE5 9PJ, UK, bDepartment of Clinical Biochemistry, cRespiratory Muscle Laboratory, Royal Brompton Hospital, London SW3 6HP, UK
- Dr M I Polkey email:
- Received 16 September 1999
- Revision requested 7 January 2000
- Revised 18 February 2000
- Accepted 30 March 2000
BACKGROUND A physiological benefit from pulmonary rehabilitation in chronic obstructive pulmonary disease (COPD) is more probable if exercise is performed above the lactate threshold. This study was undertaken to investigate whether it was possible to extend the lactataemia of exercise using non-invasive inspiratory pressure support (IPS).
METHODS Plasma lactate levels were measured in eight men with severe COPD who performed two treadmill walks at an identical constant work rate to a condition of severe dyspnoea; the second walk was supported by IPS.
RESULTS Mean plasma lactate levels before the free and IPS assisted walks were 1.65 mmol/l and 1.53 mmol/l, respectively (p = NS). Lactate levels increased during both walks to 2.96 mmol/l and 2.42 mmol/l, respectively (p = 0.01 for each) but the duration of the IPS assisted walk was significantly greater than the free walk (13.6 minutes versus 5.5 minutes, p = 0.01).
CONCLUSIONS Patients with severe COPD can sustain exercise induced lactataemia for longer if assisted with IPS. This technique may prove to be a useful adjunct in pulmonary rehabilitation.
Funding: PH was supported by grant No. F97/1 from the National Lotteries Board administered by the British Lung Foundation. SGE was supported by a project grant from NHS Research & Development (South Thames).