Fig 1.
(a) Location of DCS, catheter and ICP sensor relative to the NHP’s head. These positions were maintained across all NHPs. (b) The saline reservoir connected to the ventricle catheter was raised and lowered in a circular motion on a lever, whose center point was placed relative to the NHP’s head to allow for ICP manipulation. (c) Change in positive end-expiratory pressure (PEEP), the pressure remaining in the lungs after exhalation, through active programming of the ventilator influences systemic mean ABP (MAP).
Fig 2.
A representative measurement of one NHP under fentanyl anesthesia.
The left side shows the entire time trace of this NHP. Clear steps in ICP are shown on the top graph. ABP follows the ICP baseline trend in the second graph from the top, keeping CPP in the third graph largely stable. CPP is defined as the difference between MAP and ICP. ΔCBF changes in the bottom graph show immediate reactions to baseline changes and recovery. The right-hand side shows a zoomed in frame around the minutes 300 to 317 (grey box on the left). Here it can be seen that ICP oscillations (until 310 minutes) as well as ABP oscillations (after 310 minutes) were translated into CPP and ΔCBF.
Fig 3.
Partial pressure in end tidal CO2 averages per animal.
The error bar shows the standard deviation around the mean ETCO2 calculated across all measurements of each individual animal. The left side highlighted in red shows isoflurane anesthetized animals, the right side shows predominantly fentanyl anesthetized subjects.
Fig 4.
Lassen’s curve shows the relationship of ΔCBF over CPP (top) as a function of anesthetic.
Here the red line indicates isoflurane anesthesia, and the blue line represents the group with mainly fentanyl anesthesia. Shaded areas show the standard deviation across all NHPs in this group. The histograms are based on group averaged data for CPP, ABP, and ICP (from the top), with histogram bin sizes of 1 mmHg. A Mann-Whitney U-test was performed to test statistical significance between fentanyl and isoflurane groups. The bottom graph shows the distribution of isoflurane percentage for the anesthetic groups with the number of measurements (of approx. one-hour length each). Isoflurane percentages were recorded manually every 15 minutes, and an average across one recording (approx. 90 minutes of unchanged ICP baseline) was calculated.
Fig 5.
Pressure reactivity (PRx) values plotted as averages according to underlying CPP values.
The red line indicates the averaged response of isoflurane anesthetized NHPs, while blue is the average of fentanyl. Shaded areas show the standard deviation. The dashed line marks a correlation of 0.
Fig 6.
The phase lag between ABP and ICP during oscillations in ABP (left) and ICP (right). Red markers show isoflurane anesthesia group averages with error bars spanning the standard deviation. Blue markers show the fentanyl group.