Does the stressed patient with chronic fatigue syndrome hyperventilate?

Because the symptoms of acute hyperventilation (e.g., fatigue, headaches) and the complaints of patients with chronic fatigue syndrome (CFS) are similar, a relation may exist between these conditions. This study attempted to identify whether patients with CFS hyperventilate while breathing quietly or under stress. Two participant groups were compared: One comprised 10 patients who met the established criteria for CFS; the other comprised 9 control participants matched to patients with respect to age, sex, and socioeconomic status. Participants sat and breathed quietly through a mouthpiece for the entire study. Minute ventilation (V_e), end-tidal CO₂ (P_etCO₂), and heart rate were monitored before, during, and after presentation of psychosocial and chemical (inspiration of 5% CO2 + 95% O2) Stressors. Two psychological Stressors were used: a computational and a socioevaluative task. To evaluate each patient's perception of dyspnea, a modified Borg scale questionnaire was administered. All the variables measured except P_etCO₂ were similar in patients and normals before stressors; P_etCO₂ of participants was significantly less than controls (p<.025). V_e, Borg scores, and P_etCO₂ were not altered by psychological stress; respiratory rate did increase significantly during stress but only for the control group. In contrast, increases in heart rate occurred more consistently in the patient group than in controls. Ventilatory output did not differ between groups during CO₂ stimulation. These data show that patients with CFS are hypocapnic at rest. We define normal ventilation as eucapnia; therefore, patients with CFS hyperventilate. However, because V_e during tidal breathing as well as the ventilatory responses to both CO₂ and lab stressors were similar in patients and controls, the reason for hyperventilation is unclear.