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Background: Intracranial compliance (ICC) has been studied to complement the interpretation of intracranial pressure (ICP) in neurocritical care and help predict brain function deterioration. It has been reported that ICC is related to maintaining ICP stability despite changes in intracranial volume. However, this has not been properly translated to clinical practice. Therefore, the main objective of this scoping review was to map the key concepts of ICC in the literature. This review also aimed to characterize the relationship between ICC and ICP and systematically describe the outcomes used to assess ICC using both invasive and non-invasive measurement methods. Methods: This review included the following: (1) population: animal and humans, (2) concept of compliance or its inverse "elastance," and (3) context: neurocritical care. Therefore, literature searches without a time frame were conducted on several databases using a combination of keywords and descriptors. Results and Discussion: 43,339 articles were identified, and 297 studies fulfilled the inclusion criteria after the selection process. One hundred and five studies defined ICC. The concept was organized into three main components: physiological definition, clinical interpretation, and localization of the phenomena. Most of the studies reported the concept of compliance related to variations in volume and pressure or its inverse (elastance), primarily in the intracranial compartment. In addition, terms like "accommodation," "compensation," "reserve capacity," and "buffering ability" were used to describe the clinical interpretation. The second part of this review describes the techniques (invasive and non-invasive) and outcomes used to measure ICC. A total of 297 studies were included. The most common method used was invasive, representing 57-88% of the studies. The most commonly assessed variables were related to ICP, especially the absolute values or pulse amplitude. ICP waveforms should be better explored, along with the potential of non-invasive methods once the different aspects of ICC can be measured. Conclusion: ICC monitoring could be considered a complementary resource for ICP monitoring and clinical examination. The combination and validation of invasive/non-invasive or non-invasive measurement methods are required.
RESUMO
OBJECTIVE: This study aimed to correlate the P2/P1 ratio of intracranial pressure waveforms with sedentary behavior during the chronic stage of stroke. MATERIALS AND METHODS: Eight patients from São Carlos, Brazil, who had hemiparesis and stroke onset within the previous 6 months, participated in this study. To monitor their intracranial pressure, we used noninvasive Brain4Care® intracranial pressure monitoring during a postural change maneuver involving 15 min in a supine position and 15 min in an orthostatic position. The patients' sedentary behavior was continually monitored at home using a StepWatch Activity Monitor™ for 1 week. Moreover, the patients completed the International Physical Activity Questionnaire before and after using the StepWatch Activity Monitor™. RESULTS: In the supine and orthostatic positions, the P2/P1 ratios were 0.84 ± 0.14 and 0.98 ± 0.17, respectively. The percentage of time spent in inactivity was 71 ± 11%, and the number of steps walked per day was 4220 ± 2239. We found a high positive correlation (r = 0.881, p = 0.004) between the P2/P1 ratio and the percentage of time spent in inactivity. CONCLUSION: This preliminary study showed a correlation between sedentary behavior and cerebral compliance. Thus, monitoring of intracranial pressure during the late stage of a stroke could guide the clinician's treatment to reduce sedentary behavior and the risks of recurrent stroke and cardiovascular diseases.
