Oscillations in the near-infrared signal in patients with severe head injury.

摘要

OBJECTIVE: To use a non-invasive system, near infrared spectroscopy (NIRS) to detect oscillations in cerebral blood oxygenation in intensive care patients with severe traumatic brain injury. MATERIALS AND METHODS: 9 patients (7 male, 2 female) with a GCS < 8 were monitored in the intensive care units at King's College Hospital and the Royal London Hospital. A CCD-based spectrometer was coupled to the patient's forehead with one excitation and one detection optode. Spectra in the range of approximately 600-800 nm were collected at intervals of 2-4 seconds (subject to signal strength) and a curve-fitting algorithm applied, thus extracting time series data for oxyhaemoglobin (HbO), deoxyhaemoglobin (Hb) and cytochrome-c-oxidase (Cyt-c). The oxyhaemoglobin data was subjected to Fast Fourier Transform analysis. RESULTS: In all nine patients, unequivocal oscillations in the HbO signal were observed. The frequencies of these oscillations were at: 0.013-0.042 Hz (0.78-2.5 cycles min-1), 0.11 Hz (6.7 cycles min-1) and 0.19-0.28 Hz (12-16 cycles min-1). CONCLUSIONS: The presence of oscillations at 0.013-0.033 Hz, 0.11 Hz and 0.19-0.28 Hz are compatible with B-waves, vasomotion and respiratory cycles (respectively). However, due to the unknown contribution of the scalp to the NIR signal this data must be interpreted with care. Further work is required in order to investigate this.