Hyperventilation and chronic fatigue syndrome

We studied the link between chronic fatigue syndrome (CFS) andhyperventilation in 31 consecutive attenders at a chronic fatigueclinic (19 females, 12 males) who fulfilled criteria for CFSbased on both Oxford and Joint CDC/NIH criteria. All experiencedprofound fatigue and fatigability associated with minimal exertion,in 66% developing after an infective episode. Alternative causesof fatigue were excluded. Hyperventilation was studied duringa 43-min protocol in which end-tidal PCO₂ (P_ETCO2 was measurednon-invasively by capnograph or mass spectrometer via a finecatheter taped in a nostril at rest, during and after exercise(10–50 W) and for 10 min during recovery from voluntaryover-breathing to approximately 2.7 kPa (20 mmHg). P_ETCO2 <4kPa (30 mmHg) at rest, during or after exercise, or at 5 minafter the end of voluntary overbreathing, suggested either hyperventilationor a tendency to hyperventilate. Most patients were able voluntarilyto overbreathe, but not all were able to exercise. Twenty-twopatients (71%) had no evidence of hyperventilation during anyaspect of the test. Only four patients had unequivocal hyperventilation,in one associated with asthma and in three with panic. Onlyone patient with severe functional disability and agoraphobiahad hyperventilation with no other obvious cause. A furtherfive patients had borderline hyperventilation, in which P_ETCO2was <4 kPa (30 mmHg) for no more than 2 min, when we wouldhave expected it to be normal. There was no association betweenlevel of functional impairment and degree of hyperventilation.There is only a weak association between hyperventilation andchronic fatigue syndrome. When present, hyperventilation isusually related to known causes of respiratory stimulation suchas asthma or panic.