University of Twente Student Theses
The Effect of Positive End-Expiratory Pressure induced Arterial Blood Pressure oscillations on the Cerebral Autoregulation measures
Bos, K.D.J. (2022) The Effect of Positive End-Expiratory Pressure induced Arterial Blood Pressure oscillations on the Cerebral Autoregulation measures.
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| Abstract: | Background: On the intensive care unit (ICU), critically ill patients may have difficulties maintaining an adequate cerebral blood flow (CBF) during changes in arterial blood pressure (ABP) due to cerebral autoregulation (CA) impairments. Currently, no gold standard exists to assess the functionality of CA continuously. In addition, slow ABP fluctuations are required for reliable CA estimations. However, no methods exist to induce continuous slow ABP oscillations on the ICU. Recently, Brady et al. studied the application of slow positive end-expiratory pressure (PEEP) oscillations in an animal model. They showed an increased precision in the CA measure pressure reactivity index (PRx). However, clinical applicability in critically ill patients on the ICU is unknown. Aim: Determine the effect of slow PEEP waves on the ABP signal and the effect of slow PEEP waves induced ABP oscillations on the CA measures in sedated critically ill patients on the ICU. Methods: In this observational single center study, we included ten traumatic brain injury (TBI) patients for intracranial pressure (ICP) monitoring (ICPTBI)and eight critically ill patients for near-infrared spectroscopy (NIRS) monitoring (NIRScri ). Cyclic slow PEEP waves were introduced using the sigh function on the Dräger Evita XL or Infinity V500 ventilator. ICPTBI patients and NIRScri patients were ventilated with a static PEEP at baseline level and subsequently with PEEP oscillated between baseline level and baseline level + 5 cmH2O at a frequency of 1/min (0.0167 Hz) (sigh trial 1). Additionally, NIRScri patients were thereafter ventilated with PEEP oscillated between baseline level and baseline level + 5 cmH2O at a frequency of 1.5/min (0.025 Hz) (sigh trial 2). The effect of slow PEEP waves was studied in terms of applicability, physiological changes, and effectiveness. To assess the effect on the ABP oscillations, the power and relative power increase in ABP signals were studied. To assess the effect on the CA measures we used ICP and NIRS. First, the power and mean power spectral density (PSD) increase in ICP and NIRS signals were studied. Second, for the CA estimations, a decrease in standard deviation (SD) of the PRx (i.e., Pearson's correlation between slow ABP and ICP waves) and the TFA variables between oxygenated hemoglobin (OxyHb) and deoxygenated hemoglobin (HHb) during baseline and sigh trials were studied. Various frequency ranges were studied: PRx (0.003-0.05 Hz), NIRS (very low frequency [VLF] [0.02 - 0.07 Hz], low frequency [LF] [0.07 - 0.2 Hz], high frequency [HF] [0.2 - 0.5 Hz]). Results: No measurements were discontinued, no significant physiological changes which may negatively affect the systemic and brain physiology were observed between the study periods, and the slow PEEP waves were transmitted to slow ABP and ICP oscillations. The SD-PRx significantly decreased (p = 0.002) from baseline (mean [SD], 0.25 [0.065]) to sigh trial 1 (mean [SD], 0.14 [0.059]), suggesting an improvement of 41% in PRx precision. We observed no change in PSD-OxyHb and PSD-HHb and no change in the TFA derived variables. Conclusion: We have shown that the introduction of slow PEEP waves by using the ventilator sigh function seems to be an applicable and effective method to induce ABP oscillations in sedated critically ill patients on the ICU. Slow PEEP waves did not cause physiological changes which may negatively affect the systemic and brain physiology. The slow PEEP waves induced ABP oscillations improved the PRx precision. However, we found no added value on the PSD-OxyHb, PSD-HHb, and for the TFA derived variables. |
| Item Type: | Essay (Master) |
| Faculty: | TNW: Science and Technology |
| Subject: | 44 medicine |
| Programme: | Technical Medicine MSc (60033) |
| Link to this item: | https://purl.utwente.nl/essays/89573 |
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