Arterial blood gas analyses at the exercise breaking point were performed on eight normal subjects, eight patients with valvular heart disease, nine subjects with chronic obstructive airway disease, and four patients with severe dyspnea unexplained by organic disease (exercise hyperventilation group). Normal subjects demonstrated the most severe metabolic acidosis at the breaking point; patients with cardiac and pulmonary disease showed lesser degrees. The exercise hyperventilation group had a respiratory alkalosis at the breaking point. Arterial oxygen partial pressure was higher at the breaking point than at rest in normal subjects, patients with heart disease, and in the group with hyperventilation with exercise. In patients with pulmonary disease, arterial oxygen partial pressure usually fell with exercise. Arterial blood gas analysis at the exercise breaking point provides useful information concerning the physiological state and may be of diagnostic value in patients with puzzling dyspnea.
Gilbert R, Auchincloss JH. Arterial Blood Gases and Acid-Base Balance at the Exercise Breaking Point: Results in Normal and Dyspneic Subjects. Arch Intern Med. 1970;125(5):820–824. doi:10.1001/archinte.1970.00310050058005
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