The Science Journal of the American Association for Respiratory Care

2004 OPEN FORUM Abstracts

UN(EXPLAINED) HYPERVENTILATION

Prashant N Chhajed, MD, FCCP 1, Wolf Langewitz, MD 2, Michael Tamm, MD 1Divisions of Respiratory Medicine1 and Psychosomatic Medicine2, University Hospital Basel, Switzerland

Introduction: Psychosomatic hyperventilation is a clinical diagnosis. Hyperventilation leads to a fall in the arterial carbon dioxide tension. However, it is very difficult to document the continuous fall in the arterial carbon dioxide tension during an episode of hyperventilation.

Case summary: A 30 year old man was referred from his General Practitioner for resistant chronic pain, fatigue, muscular weakness, and disturbed sleep. The patient wakes up at night with his whole body being stiff and aching and burning sensations in the upper half of the body and his face. Asked for any measure to alleviate the symptoms he reported that sitting by the window and breathing calmly would relieve his distress to some extent. An exacerbation in pain intensity shows the following time course: air-hunger, stiffness in the legs, then extending to the whole body, tingling and burning in the feet, a feeling of pressure in the back and in his chest. Asked explicitly for respiratory symptoms he admits dyspnea at rest and occasionally on physical exercise. Lung auscultation was clear, chest x-ray showed no infiltrates and lung function test revealed no abnormalities. Maximum oxygen uptake on spiroergometry was 58% predicted (22.8 ml/kg/min), maximum heart rate achieved was 85% predicted (154/minute) and ventilatory reserve was 30% (46.7% maximum voluntary ventilation). Arterial blood gas analysis on maximal exercise showed ph 7.38, partial pressure of oxygen 96 mm Hg and partial pressure of carbon dioxide 32.2 mm Hg. Day time capnography was performed to check for hypocapnea as a marker of hyperventilation using a new digital cutaneous carbon dioxide tension (PcCO2) monitoring sensor (Sentec AG, Therwil, Switzerland) that was placed on the left earlobe in the sitting position [1, 2]. The baseline PcCO2 value was 33 mm Hg, which gradually increased to 35 mm Hg. An arterial blood gas was performed which revealed, ph 7.46, partial pressure of carbon dioxide 36.2 mm Hg (parallel PcCO2 35.1 mm Hg), partial pressure of oxygen 92.2 mm Hg and bicarbonate 25.5 mmol/L. The patient was then offered a newspaper and was left alone. When the doctor arrived in the room 10 minutes later, the PcCO2 value was 26 mm Hg and the patient complained of feeling faint. He was made to lay down and the blood pressure was 130/80 mm Hg in the left arm. Ten minutes later when he was feeling well, he was again left alone in the room for ten minutes (PcCO2 was 29 mm Hg) and this was done twice. The lowest PcCO2 value was recorded as 21 mm Hg when the doctor entered the room for the last time. At this time, another blood gas was done, which revealed respiratory alkalosis showing ph 7.57, partial pressure of carbon dioxide 25.2 mmHg (parallel PcCO2 24 mm Hg), partial pressure of oxygen 83.7 mm Hg and bicarbonate 23.2 mmol/L. The oxygen saturation during this entire test was above 96%.

Discussion: The diagnosis in this patient was profound hyperventilation at rest. A suspected diagnosis of hyperventilation in a patient with atypical symptoms could be diagnosed by the use of cutaneous carbon dioxide tension monitoring.

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