Abstract
We studied six patients with symptomatic hyperventilation, using new techniques to quantify baseline variability of respiratory variables, and to assess CO2 sensitivity around the control point using a stimulus not detectable by the subject. We compared them with six normal subjects and six patients with mild asthma. Symptomatic hyperventilators had normal mean ventilation and end-tidal carbon dioxide tension (PETCO2) at rest. Asthmatic subjects had higher ventilation and lower PETCO2. Symptomatic hyperventilators had a larger number of sighs and abnormally wide fluctuations in baseline for inspiratory time, expiratory time, and PETCO2. These could not be explained by an abnormal ventilatory response to a transient CO2 input; the transient response near the control point was undoubtedly normal.