The capnography-tilt test for the diagnosis of hyperventilation syncope

We describe the capnography tilt test (CTT) for the diagnosis of hyperventilation syncope. The CTT is a 10-min supine, 30-min head-up tilt test with simultaneous monitoring of end-tidal PCO2 (ETPCO2). Hyperventilation (HV) was defined as ETPCO2 < or = 25 mmHg. Hyperventilation syncope (HV syncope...

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Bibliographic Details
Published in:QJM : An International Journal of Medicine 1997-02, Vol.90 (2), p.139-145
Main Authors: NASCHITZ, J. E, GAITINI, L, MAZOV, I, ERIDZHANYAN, L, KEREN, D, SABO, E, YESHURUN, D, HARDOFF, D, JAFFE, M
Format: Article
Language:English
Subjects:
Adolescent
Adult
Biological and medical sciences
Breath Tests
Carbon Dioxide
Female
Humans
Hyperventilation - complications
Hyperventilation - diagnosis
Male
Medical sciences
Middle Aged
Pneumology
Respiratory system : syndromes and miscellaneous diseases
Space life sciences
Syncope - etiology
Tilt-Table Test - methods
Tropical medicine
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Summary:We describe the capnography tilt test (CTT) for the diagnosis of hyperventilation syncope. The CTT is a 10-min supine, 30-min head-up tilt test with simultaneous monitoring of end-tidal PCO2 (ETPCO2). Hyperventilation (HV) was defined as ETPCO2 < or = 25 mmHg. Hyperventilation syncope (HV syncope) was defined as loss of consciousness with ETPCO2 < or = 25 mmHg and no significant drop in blood pressure. Four groups of patients had the CTT: group I (n = 14), patients presenting with syncope who during a prior tilt test had lost consciousness without concomitant fall in blood pressure; group II (n = 50), syncope, primary evaluation, no prior tilt test done; group III (n = 20), generalized anxiety disorder, no syncope; group IV (n = 80), arterial hypertension, no syncope. Hyperventilation was found in 11/14 patients in group I, 5/50 in group II, 7/20 in group III, and none in group IV; HV syncope was diagnosed in seven patients, all in group I. None of the parameters measured in the evaluation, including ETPCO2, predicted HV syncope on tilting. The mechanisms of resting HV and HV during tilt are not well understood. We confirm the existence of HV syncope. The tilt test should probably be used to screen patients presenting with syncope, with the CTT reserved for patients who lose consciousness during the tilt test without an associated fall in blood pressure, as HV is not always clinically obvious.
ISSN:1460-2725
1460-2393
1460-2393
DOI:10.1093/qjmed/90.2.139