Failure of Perception of Hypocapnia: Physiological and Clinical Implications

Is Chronic Fatigue Syndrome Synonymous with Effort Syndrome?

Chronic fatigue syndrome (CFS), including myalgic encephalomyelitis (ME) and postviral syndrome (PVS), is a term used today to describe a condition of incapacity for making and sustaining effort, associated with a wide range of symptoms. None of the reviews of CFS has provided a proper consideration of the effort syndrome caused by chronic habitual hyperventilation. In 100 consecutive patients, whose CFS had been attributed to ME or PVS, the time course of their illness and the respiratory psychophysiological studies were characteristic of chronic habitual hyperventilation in 93. It is suggested that the labels ‘CFS’, ‘ME’ or TVS' should be withheld until chronic habitual hyperventilation - for which conventional rehabilitation is available - has been definitively excluded.

Effort syndrome: hyperventilation and reduction of anaerobic threshold

Effort syndrome is an entity in danger of being subsumed into "chronic fatigue syndrome" and lost to sight. Its distinctive feature is the reduction of the anaerobic threshold for work by depletion of the body's alkaline buffering systems through hyperventilation. This article describes the history and clinical features of effort syndrome and reports a study in which capnography is used to identify the anaerobic threshold by registering the respiratory response to the onset of metabolic acidosis. The patients' thresholds are low, and provide a goal for rehabilitation. In other forms of chronic fatigue syndrome, the pathogenesis and logic of therapy are unclear.

Hyperventilation in Patients Who Have Sustained Myocardial Infarction after a Work Injury

Patients who present with acute myocardial infarction after a work injury (AMI-WI) often report symptoms consistent with chronic hyperventilation which date back as far as the work injury itself, rather than to the AMI. The aim of the study was to test the hypothesis that hyperventilation significantly contributes to the symptoms of AMI-WI patients.

The prevalence of hyperventilation was assessed by clinical capnography in 12 AMI-WI patients, 20 normal controls, 15 AMI patients whose AMI was conventional and not subsequent to a work injury (AMI-C) and 14 patients with post-traumatic stress disorder (PTSD). End-tidal carbon dioxide partial pressure (PetCO2) was measured at rest, after 1 min hyperventilation (FHPT), after recall of the relevant stressor (Think) and when the breathing was felt to be normal (MBIN).

PetCO2 levels after FHPT were: 29.0±1.5 (mean±SD) mmHg for AMI-WI; 26.7±1.9 mmHg for PTSD; 32.1± 4.1mmHg for AMI-C and 33.7±1.4 mmHg for the controls ( P< 0.05 and P< 0.01 for AMI-WI and PTSD, respectively, versus controls). After Think, the levels were 25.8±1.6 mmHg for AMI-WI, 24.6±1.4 mmHg for PTSD, 31.2±4.1mmHg for AMI-C and 31.2± 1.5 mmHg for normals ( P<0.05 and P<0.01 for AMI-WI and PTSD, respectively, versus controls). For MBIN, values of PetCO2 were 26.8±1.7 mmHg and 26.7±1.5mmHg for AMI-WI and PTSD versus 33.8±1.2 mmHg for normals, ( P< 0.01 for both versus controls). Ten AMI-WI and 12 PTSD were positive for hyperventilation versus four AMI-C patients and four controls ( P< 0.01). The implications for rehabilitation, compensation and pathophysiology of AMI-WI are discussed, both from a medical-scientific perspective and in terms of admissible legal evidence.

The grey area of effort syndrome and hyperventilation: from Thomas Lewis to today

Lewis used the diagnosis 'effort syndrome' for subjects whose ability to make and sustain effort had been reduced by homeostatic failure. A major element was depletion of the body's capacity for buffering the acids produced by exercise. In his view this systems disorder was not to be regarded as a specific organ disease, and losing sight of the metabolic element would foster the invention of fanciful, unphysiological diagnoses. His views were dismissed because normal resting plasma bicarbonate levels were considered by others in that era to exclude serious depletion of the body's total capacity for buffering the effects of exertion. Today, effort syndrome is still a useful diagnosis for a condition of exhaustion and failure of performance associated with depletion of the body's buffering systems. Other elements associated with homeostatic failure are now recognised, principally emotional hyperarousal and hyperventilation. Their physiological interrelationships are described. Effort syndrome is amenable to recovery through rehabilitation, and it may be a mistake to treat chronic fatigue syndrome and unspecific illness without including it in the differential diagnosis.