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Updated: May 2, 2026

Expired CO2 Measurement in Intubated or Spontaneously Breathing Patients from the Emergency Department
Published on: January 29, 2011
Relationship between Hyperventilation-Induced Electroencephalographic Changes and PCO2 Level
Seungnam Son1, Oh-Young Kwon2, Seokwon Jung1
1Department of Neurology, Gyeongsang National University School of Medicine, Jinju, Korea.
Background And Purpose:
We conducted this study to define the relationship between the hyperventilation-induced EEG changes (HV-EEG changes) and PCO2.
Methods:
In consecutive EEG recordings of 190 patients, we gathered data on PCO2 during the hyperventilation procedure. The data included baseline PCO2 (B-PCO2), PCO2 after 5 min of hyperventilation (5 min-PCO2), the mean value of the PCO2 (M-PCO2), and the difference between B-PCO2 and 5 min-PCO2 (ΔPCO2). We divided the enrolled patients into two groups by hyperventilation response (response group and no-response group), presence of epilepsy (epileptic group and non-epileptic group) and age (child-adolescent group and adult group) repeatedly. We compared the four variables between the two groups in each pair.
Results:
ΔPCO2 was 14.2±5.0 mmHg (mean±SD) in response group (n=48) and 12.4±5.0 in no-response group (n=142; p=0.033) for all the patients. For adult patients only, 5 min-PCO2 was 24.3±3.4 in response group (n=30) and 26.2±4.6 in no-response group (n=115; p=0.048), and ΔPCO2 was 15.8±4.0 and 12.9±5.0, respectively (p=0.004). In non-epileptic patients, 5min-PCO2 was 23.4±2.2 in response group (n=7) and 26.3±3.8 in no-response group (n=44; p=0.026), and ΔPCO2 was 15.9±4.3 and 12.7±3.9, respectively (p=0.053).
Conclusions:
In adults and non-epileptic patients, ΔPCO2 and 5 min-PCO2 may be crucial to the induction of EEG changes by hyperventilation. PCO2 could be a crucial factor for provoking HV-EEG changes in a limited group of patients.
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