Effect of arterial oxygen desaturation on six minute walk distance, perceived effort, and perceived breathlessness in patients with airflow limitation.

Abstract

Background The effect of exercise induced hypoxaemia in determining submaximal exercise capacity, perceived breathlessness, and perceived exertion is not known. The purpose of this study was to investigate the relation of these variables to the results of lung function tests and the degree of hypoxaemia during submaximal exercise in patients with airflow limitation. Methods Forty two patients with chronic obstructive airways disease and 28 patients with chronic severe asthma were studied. Spirometry was performed and gas transfer (TLCO) and lung volumes were measured. Submaximal exercise capacity was assessed with a standardised six minute walk test. Arterial oxygen desaturation during the walk test was monitored by a portable pulse oximeter. Patients rated their perceived degree of respiratory impairment on a Medical Research Council (MRC) breathlessness scale before the walk. Perceived breathlessness was measured by means of a linear visual analogue scale and exertion on the Borg scale after the walk. Results The six minute walk distance was strongly correlated (r value) with TLCO (0-68), peak expiratory flow (PEF: 0-55), forced expiratory volume in one second (FEV,: 0 53), transfer coefficient Kco: 0 49), age (-0 49), and forced vital capacity (FVC: 0 48) but not with oxygen desaturation during the walk. Walk distance was also correlated with the breathlessness rating on the MRC scale (-0 52), but less strongly with perceived breathlessness (-0 35) and perceived exertion (-0'30). The prediction equation for the six minute walk distance in metres (6MD) generated by multiple regression analysis was 6MD = 387 + 29-7 (TLCO) -3-1(age) + 0-35(PEF l/min), which accounted for 50% of the total variance in walk distance. Conclusions Oxygen desaturation during the six minute walk is not related to walk distance, nor does it determine the degree of perceived exertion or perceived breathlessness in patients with airflow limitation. Patients who consider themselves the most disabled by breathlessness have the shortest six minute walk distance but do not necessarily have appreciable desaturation. (Thorax 1993;48:33-38) Among the most common symptoms in patients with respiratory diseases are breathlessness, reduced exercise capacity, and an increase in the sensation of effort taken to perform everyday tasks. Arterial oxygen desaturation is known to occur during exercise in some patients with respiratory disease.'7 A possible explanation for these symptoms could be arterial hypoxaemia leading to reduced oxygen delivery and acidosis resulting from anaerobic respiration; but the role of exercise induced hypoxaemia in determining submaximal exercise capacity and the degree of perceived breathlessness and perceived exertion in patients with respiratory disease is uncertain. No study has specifically examined the relation of hypoxaemia occurring during submaximal exercise to the submaximal exercise capacity and the degree of perceived breathlessness and perceived exertion.Most studies investigating exercise induced hypo...

Recommendations on the use of exercise testing in clinical practice

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“…Arterial desaturation during exercise is a common feature of advanced COPD [53,54]. While desaturation may occur with any type of intense leg exercise, walking either on a treadmill or freely along the ground elicits more hypoxaemia than cycleergometry [54,[86][87][88].…”

Distance-saturation product of the 6-minute walk test predicts mortality of patients with non-cystic fibrosis bronchiectasis

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Determinants of exercise-induced oxygen desaturation including pulmonary emphysema in COPD: Results from the ECLIPSE study

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