Microsoft Word - 3PiperIanTheBrainMonitoring.doc


 
 
 
12          Romanian Neurosurgery (2010) XVII 1: 12 - 33 

 
 
 

The Brain Monitoring with Information Technology 
(BrainIT) collaborative network:  
Past, Present and Future Direction 

Ian Piper1, Iain Chambers2, Giuseppe Citerio3, Per Enblad4, 
Barbara Gregson2, Tim Howells4, Karl Kiening5, Julia Mattern5,  
Pelle Nilsson4, Arminas Ragauskas6, Juan Sahuquillo7, St.M. Iencean8,  
R. Donald9, R. Sinnott10, A. Stell10, on behalf of the BrainIT Group 

1Clinical Physics, Southern General Hospital, Glasgow UK; 2Regional Medical Physics 
Department, Newcastle General Hospital, Newcastle, UK;  
3Neurorianimazione, Hospital San Gerardo, Monza, Italy; 4Neurosurgery, Uppsala 
University Hospital, Uppsala, Sweden;  5Neurosurgery, Ruprecht-Karls-Universitat 
Hospital Heidelberg, Germany; 6Kaunas University Hospital, Kaunas, Lithuania; 
7Neurosurgery, Vall d’Hebron Hospital, Barcelona, Spain 
8Neurosurgery, Emergency Hospital “Prof Dr N Oblu ”Iasi, Romania;  9C3 Global Ltd, 
Dingwall, Scotland; 10National eScience Centre, University of Glasgow, Scotland 
On-behalf of the Brain-IT Group (www.brainit.org). 

Abstract 
The BrainIT group works collaboratively on developing standards for collection and analyses of 
data from brain injured patients and to facilitate a more efficient infrastructure for assessing new 
health care technology with the primary objective of improving patient care. European 
Community funding supported meetings over a year to discuss and define a core dataset to be 
collected from patients with traumatic brain injury using IT based methods. In this paper, we 
give an overview of the aims and future directions of the group as well as present the results of 
an EC funded study with the aim of testing the feasibility of collecting this core dataset across a 
number of European sites and discuss the future direction of this research network. Over a three 
year period, data collection client and web-server based tools were developed and core data 
(grouped into 9 categories) were collected from 200 head-injured patients by local nursing staff 
in 22 European neuro-intensive care centres. Data were uploaded through the BrainIT web site 
and random samples of received data were selected automatically by computer for validation by 
data validation (DV) staff against primary sources held in each local centre. Validated data were 
compared with originally transmitted data and percentage error rates calculated by data category. 
Feasibility was assessed in terms of the proportion of missing data, accuracy of data collected and 
limitations reported by users of the IT methods. Thirteen percent of data files required cleaning. 
Thirty “one-off” demographic and clinical data elements had significant amounts of missing data 
(> 15%). Validation staff conducted 19,461 comparisons between uploaded database data with 
local data sources and error rates were commonly less than or equal to 6%, the exception being 
the surgery data class where an unacceptably high error rate of 34% was found. Nearly 10,000 
therapies were successfully recorded with start-times but approximately a third had inaccurate or 
missing end times which limits the analysis of duration of therapy. Over 40,000 events and 
procedures were recorded but events with long durations (such as transfers) were more likely to 
have “end-times” missed. The BrainIT core dataset is a rich dataset for hypothesis generation 
and post-hoc analyses provided studies avoid known limitations in the dataset. Limitations in the 



 
 
 

Ian Piper et al           Brain Monitoring (BrainIT)          13 

 
 
 

current IT based data collection tools have been identified and have been addressed. In order for 
multi-centre data collection projects to be viable the resource intensive validation procedures 
will require a more automated process and this may include direct electronic access to hospital 
based clinical data sources for both validation purposes and for minimising the duplication of 
data entry. This type of infrastructure may foster and facilitate the remote monitoring of patient 
management and protocol adherence in future trials of patient management and monitoring. 

Keywords: clinical network, traumatic brain injury, Grid, Internet 

Background 
Severe traumatic brain injury is a 

leading cause of death and survivors have 
serious and long term morbidity [1]. 
There are significant social and economic 
effects including loss of employment and 
an increased burden of care to the victim 
their families and society as a whole. 

The aetiology of the disease is complex 
often implicating multiple organ systems 
causing a high variation in the 
presentation of injury and, as a result, a 
large number of patients are required 
when assessing new health care 
technology. Recruiting patients from 
multiple centres will significantly reduce 
the time to assess new therapies and 
monitoring devices. However, despite the 
existence of guidelines for the 
management of severely head injured 
patients [2, 3] this group of patients is 
subject to considerable variability in care 
across centres [4-9]. To improve the 
monitoring and management standards in 
this population, the inter and intra-centre 
variability in the intensive care 
management, physiological monitoring 
and treatment of these patients needs to 
be assessed on a multi-national basis. To 
do so requires a standardised, IT based, 
higher resolution methodology for 
acquiring multi-centre patient 

management and physiological 
monitoring information. 

One consequence of the variability in 
the clinical management across centres 
that take care of patients with TBI 
(traumatic brain injury) is the 
confounding influence that this may have 
in multi-centre trials of therapy. Despite 
promising pre-clinical results of several 
potential neuroprotective drugs most have 
failed to show efficacy in the head-injured 
population. A number of reasons have 
been proposed for these failures which 
include: poor study design, insufficient 
dose of drug penetrating the blood brain 
barrier and inter-species differences in 
brain injury mechanisms. 

Another factor, not as yet 
systematically examined, may be the 
occurrence of secondary insults which are 
missed through use of inappropriate 
monitoring methods. Recent estimates 
put the proportion of adverse events 
missed by using only end-hour recording 
compared with minute by minute 
computer based monitored to be in the 
region of 30% [13]. Even in large scale 
randomised trials an accurate sample size 
analysis cannot be made without a 
knowledge of the incidence of the true 
variability of relevant confounding 
factors. Inaccurate sample size estimates 



 
 
 
14          Romanian Neurosurgery (2010) XVII 1: 12 - 33 

 
 
 

will lead to trials that are not correctly 
powered. 

Improving the standards and 
resolution for multi-centre data collection 
will also effect assessment of new medical 
technology which is of relevance to the 
medical device industry. The majority of 
companies that develop or support 
devices used to monitor brain injured 
patients in intensive care are small to 
medium size enterprises (SME). Unlike 
the pharmaceutical industry SMEs lack 
the resources to independently assess 
their devices in multi-centre clinical trials 
and this severely limits the ability to 
provide an evidence base demonstrating 
the clinical utility of their products. 

In order to address these issues it is 
essential to develop an open, collaborative 
network of centres interested in the 
realisation of higher resolution and 
standardised methods for the collection of 
neuro-intensive care monitoring and 
management data from patients with 
traumatic brain injury. Such an 
infrastructure will provide a more 
efficient means for assessing new and 
developing health care technology which 
may be new pharmaceutical compounds, 
management approaches or monitoring 
devices. 

To address these issues, the Brain 
Monitoring with Information 
Technology (BrainIT) group was formed 
(www.brainit.org) . The group has 3 main 
aims: 

1) To develop and disseminate 
standards for the collection, analysis and 
reporting of intensive care monitoring 
and management data collected from 
brain injured patients.  

2) To develop and use a standardised 
database as a tool for hypothesis 
generation and the development, testing 
and validation of new data analysis 
methodologies.  

3) To provide an efficient multi-centre 
infrastructure for generating evidence on 
the utility of new invasive and non-
invasive intensive care monitoring and 
management methods. 

The BrainIT group have first defined a 
core dataset collected using PC based 
tools as part of a European Community 
(EC) funded study (QLGT-2000-00454). 
A series of meetings spread over one year 
enabled key stake holders to meet and the 
group to define a minimum set of data 
that should be collected from all patients 
with traumatic brain injury (TBI). The 
outcome of the study was to define a core 
dataset which would be useful in most 
research projects conducted in this 
population of patients [10]. 

This paper reports on the results of a 
subsequent three year EC funded study 
(QLGC-2002-00160) that enabled the 
group to develop IT methods to collect 
the core dataset and to assess the 
feasibility and accuracy for collection of 
this core-dataset from 22 neuro-intensive 
care centres across Europe. Feasibility was 
assessed in terms of amount of missing 
data, accuracy of data collected and 
limitations reported by users of the IT 
data collection methods. To assess 
accuracy, data validation staff (usually 
research nurses) were hired on a regional 
basis (normally country by country) to 
check samples of the collected data against 
the local primary clinical record in order 
to quantify the accuracy of the IT based 



 
 
 

Ian Piper et al           Brain Monitoring (BrainIT)          15 

 
 
 

data collection methods. This paper 
describes an analysis of the comparison of 
the data from 200 patients with that 
obtained independently by data validation 
staff . The error rates classed by data 
category are described and the known 
limitations of current IT data collection 
methods are considered along with some 
proposed solutions . 

Methods 
Core dataset Definition 
Through European Community (EC) 

funding (QLRI-2000-00454), a series of 
meetings over a one year period brought 
together neurosurgeons, intensivists, 
scientists and representatives from the 
medical device and pharmaceutical 
industries to define and discuss a “core-
dataset definition” for data that should be 
collected from all patients with traumatic 
brain injury (TBI), irrespective of the 
underlying project aim. A core dataset was 
defined and published [10] that consisted 
of the following nine data categories: 

i) Demographic and “one-off” clinical 
data (pre-neurosurgical hospital data, 
neurosurgical hospital admission data and 
the first and worst CT scan data). This 
data is collected only once per patient. 

ii) Daily management data (eg: use of 
sedatives, analgesics, vasopressors, fluid 
input/output balance etc). This data is 
collected as an overview of the day to day 
intensive care management of the patient 
and is collected only once per day. 

iii) Laboratory data (eg: blood gas, 
haematology, biochemistry data etc). This 
is “episodic” data which is data collected 
more than once but at unpredictable 
times. 

iv) Event data (eg: nursing 
manoeuvres, physiotherapy, medical 
procedures (line insertion), calibrations 
etc - also episodic data). 

v) Surgical procedures.  
vi) Monitoring data summary (eg: type 

and placement location of ICP sensor, BP 
lines, etc). Typically this data is only 
collected once per patient and is an 
overview of the monitoring configuration 
for a patient. 

vii) Neuro Event data (eg: Glasgow 
Coma Score, pupil size and reactivity also 
episodic data). 

viii) Targeted Therapies A set of 
therapy categories have been defined with 
some associated therapy type detail. For 
every therapy given an intended target 
must also be given (eg: mannitol for 
raised ICP). 

ix) Vital monitoring data. This is 
bedside monitoring data which is 
collected at regular intervals with a 
minimum sampling rate of once per 
minute. 

Network Structure 
The BrainIT group network structure 

consists of a central coordinating and data 
centre (Glasgow) with individual centres 
clustered into language based regions 
where each language region contains a 
sub-coordinating centre. Each sub-
coordinating centre is responsible for 
coordinating the training and validation 
activities across centres within their 
region and to meet this requirement hire 
a “data validation” nurse responsible for 
providing training on the data collection 
tools and web-services to all centres 
within their own language region. The 
data validation nurses also provide a data 



 
 
 
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checking and validation service 
coordinated from Glasgow.  

Data Collection Tools 
Clinical data is entered by local bedside 

nursing staff either on hand held PDA’s 
or on in-house designed JAVA based 
software running on a PC. In 
collaboration with Kelvin Connect Ltd 
[11] the BrainIT core dataset definition 
was implemented in a flexible and easy to 
use hand-held PDA based device. A 
training course was held for the data 
validation nursing staff in Glasgow on the 
optimal use of the data collection 
instruments which also provides data 
entry in six European languages. An 
anonymisation routine removed patient 
identification elements from the collected 
data and labelled the patient data file with 
a unique BrainIT study code generated 
from the BrainIT web-site. A local 
database held in each centre linked the 
anonymised data to local centre patient 
ID information which was needed during 
the data checking stage of the study. 
Anonymised data was uploaded via the 
BrainIT website. A server side data 
converter tool converted data from centre 
specific format into a standardised 
BrainIT data format generating nine data 
category files which are imported into the 
BrainIT Microsoft SQL2005 database.  

Data Validation Process 
Figure 1 graphically represents the data 

validation process. Centre staff enter data 
using client side tools such as the hand 
held PDA. Data is uploaded via the 
BrainIT web-services and a server-side 
converter formats data into the series of 
common data format files which are input 
into the BrainIT SQL database. A 

validation request tool residing on the 
database server randomly samples 20% of 
the data uploaded for each data category 
and generates a validation request file for 
each local data validation nurse listing the 
timestamps and data items to be checked 
against local data sources. Data validators 
move between their designated centres 
and enter into a data validation tool the 
requested data items from source 
documentation held in each local centre. 
The resulting validation data file is 
uploaded to the BrainIT data coordinating 
centre via the website and using data 
validation checking software tools, the 
validated data is checked against the data 
items originally sent from which 
percentage accuracy data was calculated. 

As part of this validation process, and 
in addition to the categorical and numeric 
clinical data being checked for accuracy, 
we also assessed the minute by minute 
monitoring data. Random samples of 
monitoring data channels uploaded (eg: 
ICP, SaO2) were selected and validation 
staff asked to manually enter the hourly 
recorded values from the nurses chart (or 
local gold standard data source) for the 
first and last 24 hour periods of bedside 
monitoring for a given patient for a given 
channel. These “validation” values could 
then be compared with a range of 
summary measures (eg: mean, median) 
from the computer based monitoring data 
acquired from the patient.  

Assessing Feasibility 
To assess feasibility, we sought answers 

to specific questions including:  
a) What data cleaning was necessary 

prior to analysis?  



 
 
 

Ian Piper et al           Brain Monitoring (BrainIT)          17 

 
 
 

b) What proportion of missing data 
was found in each data category?  

c) How accurate is the data that was 
collected?  

d) What are the known limitations of 
the existing IT methods for collection of 
the data? 

Results 
Data Description 
Over a two year period, core dataset 

data (grouped by nine categories) were 
collected from 200 head-injured patients 
by local nursing staff. One patient’s data 
was discarded from the cohort as there 
was less than 4 hours of monitoring data 
which fell outside our inclusion criteria 
leaving 199 patients in the feasibility study 
dataset. Table 1 summarises the key 
demographic and clinical features of the 
study cohort. Mean age was 36 years with 
the usual predominance of male patients 
in such series. Using the TCDB 
classification on worst CT, 100 patients 
were coded with diffuse injury and 60 
with mass lesions. Using the extended 
Glasgow Outcome Scale (GOSe) there 
were 33 deaths (20%) with 47% good and 
53 % poor outcome respectively. Table 2 
summarises the quantity of data collected 
per patient classed by data category. There 
were 109 “one-off” demographic and 
clinical data items collected which 
included pre-neurosurgical (PHSH) and 
neurosurgical hospital (NSH) data. The 
majority of the data were “episodic” in 
nature in that they were collected more 
than once per patient but at un-
predictable times. These data types 
included “ICU monitoring” categories 
describing, for example, the location and 

type of medical monitoring device placed 
(eg: right frontal ICP bolt), neurological 
status (ICU GCS scores/pupil size and 
reactivity) , therapies delivered, surgeries 
performed etc. The largest number of 
data items collected fell within the “Other 
clinical events” category which included 
annotations of blood samples, lab results, 
and other nursing and medical 
procedures. In this category there was on 
average greater than 230 recordings per 
patient. The next most common category 
of data collected were those of 
annotations of target driven therapies. In 
this category there were on average 
greater than 60 targeted therapies 
delivered per patient. By far the largest 
category of data collected was the 
“periodic” minute by minute 
physiological monitoring data with over 2 
million records in the patient cohort. 
Table 3 lists the number of patients with 
specific types of monitoring. Figure 2 is a 
histogram plot showing the quantity and 
spread of time-series data for the main 
monitored channels: ICP, BP, CPP, 
CVP, SaO2, Core Temperature, ETCO2 
and PtiO2. The number of data points 
sampled per channel ranges from 89,524 
for PtiO2 to 1.98 million samples for 
BPm. (BPm = 1,979,284, ICPm = 
1,748,423, CPP= 1,719,166 , CVPm= 
541,524, SaO2 = 1,656,614 , Tc = 
1,372,641, ETCO2 = 502,524, PtiO2 = 
89,524. 



 
 
 
18          Romanian Neurosurgery (2010) XVII 1: 12 - 33 

 
 
 

Data Cleaning 
On average three raw data files were 

uploaded per patient giving 600 patient 
data files uploaded to the central database 
using the BrainIT web-services. All data 
files were validated prior to inclusion into 
the study dataset and in a proportion of 
these errors were found with data values 
needing to be re-checked and corrected 
by local nursing staff. Seven raw data 
patient files required resolving 
mismatches between physiological data 
patient identifiers and other clinical data 
files (1.2 % of files uploaded). Ten raw 
data files required trimming of 
physiological data outside the range of 
clinical data (2% of files uploaded). 
Nineteen patient files required correction 
of one or more admission, surgery or 
discharge time stamps (3% of files 
uploaded). 

Missing Data  
One-Off Measurements 
There was missing data across certain 

data fields. Figure 3 is a graph listing 
those “One-Off” demographic and 
clinical data fields with greater than 15% 
of missing data. Common patterns in the 
types of fields yielding the highest missing 
data rates could be identified: A) One 
third of the fields with significant 
amounts of missing data were “one off” 
laboratory data values (eg: glucose, 
Haematocrit, PaCO2) which should have 
been obtained from admission notes from 
either the pre-neurosurgical hospital 
(PNSH) or the receiving neurosurgical 
hospital (NSH). B) One third of the 
missing fields were explanatory variables 
associated with either the first or worst 
CT scan classification. These explanatory 

variables included “yes/no” categories as 
to whether or not specific pathologies 
were seen on CT such as SAH, 
pneumoencaphalopathy, hydrocephalus 
etc. C) Fifteen percent of the missing data 
fields were explanatory variables 
associated with the 6 month Glasgow 
Outcome Scale data. These included 
fields such as “who was the main 
respondent” to the questionnaire and 
what was deemed to be the “main cause 
of disability” (head injury or systemic 
injury).  

Episodic Measurements 
These data types include therapies, 

laboratory values and nursing and medical 
procedures that were entered more than 
once at un-predictable times. For each 
episodic data measurement both a “start-
time” and “end-time” should have been 
recorded for each measurement by local 
nursing staff. Nearly 10,000 therapies 
were successfully recorded with start-
times but approximately a third had 
missing end times. Table 4 is a 
breakdown of the therapies delivered 
classed by type listing the proportion with 
missing “end-times”. Clearly the quantity 
of missing end-times in this part of the 
dataset severely limits analyses assessing 
duration of therapy. Over 40,000 events 
and procedures were also recorded but 
events with long durations (such as 
transfers outside of the ITU for theatre or 
CT scan) were more than twice as likely 
to have “end-times” missed. These short-
comings in the acquired episodic data 
have implications for the design of future 
data collection/validation tools as well as 
project training procedures. 



 
 
 

Ian Piper et al           Brain Monitoring (BrainIT)          19 

 
 
 

Data Accuracy 
In total, 19,461 comparisons were 

made between collected data elements 
and source documentation data by data 
validation research nurses. The number 
of comparisons made per data category 
were in proportion to the size of the data 
received for that category with the largest 
number checked in laboratory data 
(5,667) and the least in the surgery data 
(567) (Figure 4). Table 5 summarises 
error rates by data class. Error rates were 
generally less than or equal to 6%, the 
exception being the surgery data class 
where an unacceptably high error rate of 
34% was found. 

In the surgery data category, nursing 
staff had to choose surgical procedures 
from a fixed list of procedure types: i) 
ICP placement, ii) Evacuation of Mass 
Lesion, iii) Elevation of depressed skull 
fracture, iv) Removal of foreign body, v) 
Anterior Fossa repair for CSF Leak, vi) 
Placement of Extra Ventricular Drain, vii) 
Active external decompression (with bone 
removal and duroplastia), viii) Other. 
This classification system was used in an 
attempt to simplify and reduce the burden 
of data entry. However, through 
discussions with local nursing and data 
validation staff it was found that there was 
particular confusion over when to record 
ICP sensor placement and the presence of 
skull fractures as the primary surgical 
procedure. Typically, these procedures 
occur during the same operative 
procedure as for example during 
“evacuation of a mass lesion”. Confusion 
over coding these two procedures 
between the original data entry nurse and 

the validation nurse accounted for the 
majority of errors in this data category.  

The detection rate of acute events was 
also examined (eg: nursing management, 
physiotherapy, blood samples etc). It was 
found that short duration events were 
rarely missed but longer duration events 
such as transfer to CT or theatre were 
more likely to be not recorded. Through 
discussions with local nursing and data 
validation staff it is believed that the 
intense nursing activity just prior to and 
following a transfer is more likely to lead 
to omissions in recording these events on 
research systems.  

Finally, we tested the accuracy of the 
minute by minute monitoring data that 
was collected. Table 6 shows the 
monitoring data validation results for the 
6 data types with the most recorded 
nursing chart values. Data is expressed in 
terms of bias (+- 95% CL) between the 
nurses chart recorded values against the 
computer collected end hour averages. It 
can be seen from this data that the 
computer collected end hour data is an 
accurate reflection of the nurse’s chart 
recorded data. 

As an example, Figure 5 shows a scatter 
plot of computer monitored minute by 
minute ICP data averaged over 60 
minutes (ICPavg) plotted against nurses 
chart end hour values (ICPvalid) 
collected by the data validation nurses. 
There is a good correlation between the 
two sets of data with a linear regression 
best fit R2 value of 0.9773. Figure 6 is an 
Altman and Bland plot showing the 
average bias (-0.15 mmHg) and 95% 
confidence limits (0.12, -0.45) for the 
computer monitored end hour averaged 



 
 
 
20          Romanian Neurosurgery (2010) XVII 1: 12 - 33 

 
 
 

data Vs the nurses chart end hourly 
recorded values collected by the validation 
nurses. 

IT Tool Limitations 
The PDA data entry tool and the 

website-upload tools did not incorporate 
sufficient validation mechanisms. Many 
fields with the PDA tool allowed export 
and upload of empty data fields. Although 
most IT technology nowadays can be 
configured to explicitly specify required 
fields and prevent upload of data with 
specific missing data, at the time this 
study was designed, such validation 
facilities were not available off the shelf. 
Also, the PDA tool was designed to allow 
acceptance of new items not part of the 
drop down selection menu, which could 
generate multiple terms for the same data 
element. This caused added burden on 
the cleaning process to consolidate 
multiple text terms for the same data 
element. The most challenging limitation 
found with the IT technology used in this 
study was an inability to automatically 
track “continuous” (non-bolus) therapies 
which were started to ensure that a 
matching “end-time” was entered. This 
resulted in approximately 1/3rd of the 
therapies annotated to have missing end 
times.  

Discussion 
This project has studied the feasibility 

for collection of the BrainIT core dataset 
using our first generation IT based tools. 
Feasibility has been assessed in terms of 
amount of missing data, data accuracy for 
data that was collected and also in terms 
of identifying limitations in the IT 
technology used to collect the data.  

Good laboratory practice dictates that 
as part of clinical trial design, acquired 
data must be checked for accuracy against 
the primary data sources. This is often 
implemented through either employing a 
contract research organisation or 
independent research nurse staff to 
perform this duty. In large multi-centre 
clinical trials, costs to hire research nurse 
data validation staff can become 
prohibitively expensive and feasible only 
if significant industry or research council 
funding support is provided. Now with 
the adoption of the new medical device 
standard ISO-14155, even small medical 
device studies are expected to provide 
some form of check on the accuracy of 
data collected even as part of a non-
regulatory post-marketing study.  

To our knowledge, this study 
conducted by the BrainIT group is one of 
only a few multi-centre projects to 
attempt to prospectively assess the data 
capture error rate within an academic 
investigator led environment [12].  

Monitoring Data Validation 
We have shown that computer 

collected minute by minute vital signs 
data, summarised as end hour averages, 
correlated well with nursing chart end 
hour recordings. This allows for the end 
hour averaged computer records to be 
used in database analyses that aim to 
assess nurses chart recorded detection of 
events with computer based sampling. 
Although, end-hour average data 
correlates well with the nurses hourly 
recorded value, this does not indicate that 
important features of the data are not 
being missed by employing only hourly 
recording. For example, Zanier and 



 
 
 

Ian Piper et al           Brain Monitoring (BrainIT)          21 

 
 
 

colleagues [13] conducted a study 
showing that although computer-
monitored end-hour data is accurately 
reflected by the nurses’ chart value, more 
complex summary measures (such as the 
detection of an intracranial pressure (ICP) 
of more than 20 mmHg) are less accurate. 
Their finding that at least one-third of 
secondary insults for raised ICP are not 
identified from the nursing chart is 
similar to that reported by Corrie and 
colleagues [14], who also found a similar 
detection error rate for other signals such 
as blood pressure, particularly the events 
of shorter duration. Importantly, Zanier’s 
paper has further shown that when data 
are categorised in terms of percentage of 
time spent with raised ICP, the patients 
exhibiting instability in ICP were most 
prone to under estimation of ICP insults. 
The data sampling rate may be pertinent 
here: Zanier’s study sampled at 600 
samples per minute, whereas other 
studies used 1 sample per minute [14] or 
as few as 4 samples per hour [15]. Our 
results here confirm those of other 
investigations showing that the end hour 
averaged computer values can be used as 
estimates of nurse’s paper based end hour 
recordings and opens up the possibility 
for further studies assessing the clinical 
influence of missed short term adverse 
physiological events without requiring 
tedious recording of nursing chart values.  

However, the key question remains 
unanswered as to whether missed adverse 
events using higher resolution sampling 
significantly influences clinical outcome. 
Work conducted by Chambers and 
colleagues may be relevant in this regard 
[16]. They found that in studies of 

children with TBI, the choice of 
summary measure is also important. They 
used an index termed the “Pressure Time 
Index (PTI)”, which is a composite index 
taking into account both the duration of 
the adverse event and the degree of 
physiological impairment below a given 
threshold. They found, using ROC 
analysis of the influence of cerebral 
perfusion pressure adverse events upon 
clinical outcome (calculated using an age - 
related PTI index in children), that 
models that included the PTI measure of 
CPP burden significantly improved the fit 
to clinical outcome compared with 
models that did not include measures of 
physiological instability. These results are 
in contrast to those published by 
Signorini et al who they found very little 
improvement in outcome prediction 
when “Insults” are added to the usual 
clinical features in prognostic models of 
patient outcome [17]. The approach 
developed by Chambers and colleagues 
needs to be repeated in the adult TBI 
population and is one of the planned 
analyses on the BrainIT dataset.  

Validation Costs 
These validation results calculated on a 

subset of patients provides an estimate of 
the data quality on a larger patient cohort 
of 350 patients collected using the same 
methodology but collected outside of the 
validation study. However, future data 
collection projects will generate datasets 
under differing data collection conditions 
and will require a separate validation stage 
if we wish to maintain our confidence in 
the level of data collection accuracy. The 
approach used by the BrainIT group to 
validate data (using 20% sampling of 



 
 
 
22          Romanian Neurosurgery (2010) XVII 1: 12 - 33 

 
 
 

uploaded data with some automation of 
generating data lists for validation) still 
requires significant research nurse time to 
track down and enter data for validation 
purposes. To maintain a full time data 
validation nurse across all participating 
countries costs in excess of 1 Million 
Euro’s per year. Such large overheads for 
an academic network is prohibitively 
expensive and not sustainable and a more 
cost-effective solution for data validation 
must be found.  

One promising approach now being 
assessed by the BrainIT group is 
developing collaborative research with 
experts in Grid based middleware 
technology. Grid technology comes in a 
variety of forms and covers more than just 
access to networks of high end servers in 
order to solve computationally intensive 
problems. There is a considerable amount 
of expertise and open source middleware 
software solutions now available that 
provide secure access to distributed 
medical datasets so that the right people 
see the correct data in the appropriate 
context [23]. Such an approach, provided 
local IT policy staff are satisfied with the 
system security, will enable remote data 
validation systems to directly query 
hospital based primary data sources for 
the purpose of checking the quality of 
previously uploaded data. Most research 
datasets contain large portions of data 
elements that are collected for routine 
patient management purposes and the 
difficulty of accessing hospital based data 
sources often means that research nurses 
are employed to re-enter data extracted 
from local hospital sources into research 
data entry systems. This results in a high 

proportion of double data entry which is 
an inefficient use of nursing resources. 
Using Grid technology to interface 
directly with local hospital data sources 
will reduce the burden of double data 
entry. Clearly some data validation staff 
will still be required to support system 
queries but increased use of automatic 
data validation procedures and access to 
hospital based datasets should 
significantly reduce the cost burden to 
conduct multi-centre clinical trials. 
Towards this end, the BrainIT group as 
part of an EC funded framework VII 
project are now assessing such an 
approach in a group of neuro-intensive 
care centres equipped with the latest Grid 
technology. This project – the AVERT-IT 
project [18] has installed Grid services 
behind hospital firewalls in six BrainIT 
neuro-intensive care units. Grid services 
will interface to local hospital systems, 
extract data which maps to the BrainIT 
core dataset and integrate data from both 
hospital sources and local AVERT-IT data 
collection tools (for those elements not 
collected as part of routine management) 
into a local database. Once every 20 
minutes, data is stripped of patient 
identifiers, encrypted and “pushed” out of 
local hospital networks to an external 
secure server cluster hosted at the 
University of Glasgow National eScience 
Centre [19]. Local databases will be 
maintained which link local patient 
identifiers with an anonymous patient 
identifier. Systems running at the BrainIT 
coordinating centre in Glasgow allow 
remote monitoring of the data acquired 
from all six participating BrainIT centres. 
Such a remote monitoring service in 



 
 
 

Ian Piper et al           Brain Monitoring (BrainIT)          23 

 
 
 

quasi real-time (updates every 20 
minutes) will allow more efficient 
collection and validation of hospital based 
data collected for research purposes while 
the patient (and their notes) are still 
within the ITU environment. This 
infrastructure will also support 
monitoring of patient management for 
adverse events (such as treatments given 
for arterial hypotension) and will enable 
testing and tracking adherence to study 
protocols.  

Lessons Learned 
A number of lessons have been learned 

during this feasibility study. First, our 
surgery classification definition is 
ambiguous. Specifically our definition 
document did not make it clear how to 
decide which surgery is the “Primary 
Reason for Surgery”. For example if a 
patient undergoes surgery for removal of 
a mass lesion and repair of depressed skull 
fracture, some approach must be used to 
provide a consistent classification 
response. We are proposing a modified 
surgery classification to include a “major 
surgery choice matrix” where individual 
surgery types are weighted and specific 
combinations that do occur can be 
resolved to a single surgical priority.  

Secondly not all staff favoured use of a 
PDA type data tool. By the end of the 
feasibility study,  

approximately half the centres 
collecting data preferred to use PC based 
systems rather than the hand-held PDA’s. 
Increasingly, nursing and medical staff 
have good IT and data entry skills and as a 
result we have developed new PC based 
data collection tools. Also, our data tools 
(although state of the art at the time), did 

not provide sufficient local validation 
features such as preventing export and 
upload of empty data fields. Most IT 
technology nowadays can be configured 
to explicitly specify required fields and 
prevent upload of missing or incorrect 
data. Our current generation of data tools 
now almost entirely allow only specific 
choices to be made from drop-down 
“combo boxes” where the default choice 
is set to a text value of “not set”. This 
makes it explicitly clear that a given field 
has not been entered. Our data schema 
will not allow mandatory fields to be left 
“not-set” before a patient is discharged 
from the system. For the entry of 
treatment information, every treatment 
must be assigned a specific target and 
again, the data schema will not accept 
treatments that have not been assigned a 
target. Furthermore, our next generation 
data collection tools, as implemented in 
the AVERT-IT project, allows annotation 
of any treatment or procedure with only 
two mouse clicks providing more rapid 
and efficient data entry for the bed side 
nurse. The web-client software now 
includes data validation routines which 
will prevent upload of missing data in any 
required fields. Patients cannot be fully 
discharged from the system until all 
required data is entered. Patients with 
missing data can be partially discharged 
from the system (when they are 
discharged from the ITU) but they 
remain in a visible list “Patients with 
Missing Data”. A single web page displays 
all missing fields in red and must be 
completed before the patient can be fully 
discharged.  



 
 
 
24          Romanian Neurosurgery (2010) XVII 1: 12 - 33 

 
 
 

Current Status and Future Direction 
The aims of the BrainIT group and 

their implementation is a staged process. 
We have successfully defined a core 
dataset standard, developed some 
standardised IT tools to collect the core 
dataset and tested the feasibility for 
collection of the dataset from 22 centres 
across Europe. Limitations in our 
methods have been found and attempts 
have been made to address those issues 
prior to starting future studies. Inevitably, 
with each new project, problems will arise 
and solutions will be found in a cyclical 
process. Our second aim “To develop and 
use a standardised database as a tool for 
hypothesis generation and the 
development, testing and validation of 
new data analysis methodologies.” has 
been achieved and a number of 
publications are now arising from access 
to this shared resource [20]. We are 
currently using the 2nd database release 
with a third release planned, and what is 
encouraging is that the existence of the 
database resource was directly responsible 
for generating and testing the hypothesis 
about application of Bayesian neural 
network methods for prediction of arterial 
hypotension adverse events which lead to 
a project now funded under the VIIth EC 
information and communications 
technology framework [18].  

One of the papers arising from the 
work of the BrainIT group was a report 
on its own internal survey of patient 
management which indicated that 
international management guidelines are 
for the most part adhered with [9]. 
However, there is a risk with surveys that 
there may be differences in results 

between what users believe to be the 
management applied in their centre and 
studies which measure it directly. In this 
regard, a recent paper published by one of 
our collaborators on analyses of the 
BrainIT dataset was to assess, subsequent 
to the BrainIT survey, whether the use of 
hyperventilation therapy for the 
management of raised ICP was indeed 
conducted according to international 
guidelines. Interestingly they found that 
despite what was suggested by the earlier 
survey results, and in conflict with 
current management guidelines, there 
was significant over use of early 
prophylactic hyperventilation [22]. This 
result highlights the importance of 
directly monitoring the applied 
management, and if it can be achieved in 
near real-time, will enable future 
management trials to monitor protocol 
adherence and better select when patients 
data can be recruited to a study. 

The third and most challenging aim of 
the BrainIT group is to use its improved 
infrastructure to generate new evidence 
on the utility of monitoring and 
management methods for patients with 
TBI. The AVERT-IT project, now 
underway, will put in place in six BrainIT 
centres, Grid middleware systems 
enabling direct access to hospital data and 
remote monitoring of patient 
management. We believe that this type of 
remote monitoring facility is a pre-
requisite for the conduct of a future 
multi-centre management trial by the 
BrainIT group. Discussions of a 
management trial design have been 
started at the recent BrainIT group 
meeting (Vilnius, September 2009) and 



 
 
 

Ian Piper et al           Brain Monitoring (BrainIT)          25 

 
 
 

the current AVERT-IT project will pilot 
the feasibility of the remote monitoring 
infrastructure required for the conduct of 
such a trial.  

Conclusions 
In this study we have shown that it is 

feasible to collect the BrainIT dataset 
from multiple centres in an international 
setting with our IT based methods and 
the accuracy of the data collected is 
greater than or equal to 94%, with the 
exception of the surgery data definition 
which is being revised. Lessons learned 
about weaknesses with our data collection 
methods have been met with advances in 
client/server tools providing improved 
validation support. We anticipate that the 
second generation of BrainIT data 
collection tools (now being used as part of 
the current AVERT-IT project) will 
improve missing data and validation 
accuracy rates. A future BrainIT 
management trial will rely on a Grid 
based infrastructure capable of remotely 
monitoring patient management and 
protocol conformance now being piloted 
in six BrainIT centres. Academic led 
multi-centre data collection projects must 
decrease validation costs and to do so will 
require more direct electronic access to 
hospital based clinical data sources for 
both data validation purposes and for 
reducing the research nurse time needed 
for double data entry of data currently not 
accessible from hospital based systems. 

References 
1. Olesen J, L. M. The burden of brain disease in 
Europe. European Journal of Neurology, 2003, 10, 471-
477. 

2. Bullock R, Chesnut RM, Clifton C, et al. (1996) 
Guidelines for the management of severe head injury. J 
Neurotrauma 13:643-734. 
3. Maas AI, Dearden M, Teasdale GM, Braakman R, 
Cohadon F, Iannotti F, Karimi A, Lapierre F, Murray 
G, Ohman J, Persson L, Servadei F, Stocchetti N, 
Unterberg A (1997) EBIC-Guidelines for management 
of severe head injury in adults. Acta Neurochir 139:286-
294. 
4. Ghajar J, Hariri RJ, Narayan RK, Iacono LA, Firlik K, 
Patterson RH (1995) Survey of critical care 
management of comatose, head-injured patients in the 
United States. Crit Care Med 23:560-567. 
5. Jeevaratnam DR, Menon DK (1996) Survey of 
intensive care of severely head injured patients in the 
United Kingdom. BMJ 312:944-947. 
6. Matta B, Menon D (1996) Severe head injury in the 
United Kingdom and Ireland: A survey of practice and 
implications for management. Crit care Med 24:1743-
1748. 
7. Murray GD, Teasdale GM, Braakman R, Cohadon F, 
Dearden M, Iannotti F, Karimi A, Lapierre F, Maas A, 
Ohman J, Persson L, Servadei F, Stocchetti N, 
Trojanowski T, Unterberg A (1999) The European 
Brain Injury Consortium survey of head injuries. Acta 
Neurochir 141:223-236. 
8. Stochetti N, Penny KI, Dearden M, Braakman R, 
Cohadon F, Iannotti F, Lapierre F, Karimi A, Maas A, 
Murray GD, Ohman J, Persson L, Servadei F, Teasdale 
GM, Trojanowski T, Unterberg A, on behalf of the 
European Brain Injury Consortium (2001) Intensive 
care management of head-injured patients in Europe: a 
survey from the European Brain Injury Consortium. 
Intensive Care Med 27:400-406. 
9. Enblad P, Nilsson P, Chambers I, Citerio G, Fiddes 
H, Howells T, Kiening K, Ragauskas A, Sahuquillo J, 
Yau YH, Contant C and Piper I. Survey of traumatic 
brain injury management in European Brain IT centres 
year 2001, Intensive Care Med (2004) 30:1058 –1065. 
10. Piper I, Citerio C, Chambers I, Enblad P , Nilsson 
P, Chambers I, Citerio G, Fiddes H, Howells T, 
Kiening K, Ragauskas A, Sahuquillo J, Yau YH, Contant 
C. The BrainIT Group: Concept and Core Dataset 
Definition. Acta Neurochir 145:615-629 2003. 
11. http://www.kelvinconnect.com/ 
12. Citerio G, Stocchetti N, Cormio M, Beretta L. 
Neuro-Link, a computer assisted database for head 
injury in intensive care. Acta Neurochir 
(Wien)142(7):769-76. 2000 
13. Zanier E, Ortolano F, Ghisoni L, Colombo A, 
Losappio S, Stochetti N. Intracranial pressure 
monitoring in intensive care: clinical advantages of 
computerised monitoring over manual recording. Crit. 
Care Med. 11:R7. 2007 



 
 
 
26          Romanian Neurosurgery (2010) XVII 1: 12 - 33 

 
 
 

14. Corrie J, Piper I, Housely A, Tocher J, Anderson S, 
Midgley S, Slattery J, Dearden N, Miller J. 
Microcomputer based data recording improves 
identification of secondary insults in head injured 
patients. British Journal of Intensive Care, June 1993. 
226-233. 
15. Venkatesh B, Garrett P, Fraenkel DJ and Purdie D. 
Indices to quantify changes in intracranial and cerebral 
perfusion pressure by assessing agreement between 
hourly and semi-continuous recordings. Intensive Care 
Med 2004; 30: 510-513. 
16. Chambers IR, Jones PA, Lo TWM, Forsyth RJ, 
Fulton B, Andrews PJD, Mendelow AD and Minns RA. 
Critical thresholds of intracranial pressure andcerebral 
perfusion pressure related to age in paediatric head 
injury. J. Neurol. Neurosurg. Psychiatry 2006;77;234-
240. 

17.[17] Signorini DF, Andrews PJD, Jones PA, 
Wardlaw JM and Miller JD. Adding insult to injury: the 
prognostic value of early secondary insults for survival 
after traumatic brain injury. J. Neurol. Neurosurg. 
Psychiatry 1999;66;26-31 
18.[18] http://www.avert-it.org 
19.[19] http://www.nesc.ac.uk 
20.[20] http://www.brainit.org/bit2web/faces/Papers.jsp 
21.[21] 
http://www.brainit.org/bit2web/faces/Meetings.jsp 
22.[22] Neuman J, Chambers I, Citerio G, Enblad P, 
Gregson B, Howells T, Mattern J, Nilsson P, Piper I, 
Ragauskas A, Sahuquillo J, Yau H, Kiening K on Behalf 
of the BrainIT Group. The use of hyperventilation 
therapy after Brain Injury in Europe: An analysis of the 
BrainIT database. Intensive Care Medicine 2008; 
S00134-008-1123-7. 
23.[23] http://www.nesc.ac.uk/hub/projects/votes/ 

Acknowledgements 
We wish to acknowledge the 

contribution of all data contributing 
members of the BrainIT group 
(www.brainit.org) who supported the 
EEC project: QLGC-2002-01160.  

Investigators and Participating Centres 
Barcelona Spain, Prof J Sahuquillo; 

Cambridge UK., Prof JD Pickard; 
Edinburgh UK, Prof R Mins, Prof I 
Whittle; Glasgow UK, Mr L Dunn; 
Gothenburg Sweden, Dr B Rydenhag; 
Heidelberg, Germany, Dr K Kiening; Iasi 
Romania, Dr St.M. Iencean; Kaunas 
Lithuania, Prof D Pavalkis; Leipzig 
Germany, Prof J Meixensberger; Leuven 
Belgium, Prof J Goffin; Mannheim 
Germany, Prof P Vajkoczy; Milano Italy, 
Prof N Stocchetti; Monza Italy, Dr G  

 

 
Citerio; Newcastle upon Tyne UK, Dr IR 
Chambers; Novara Italy, Prof F Della 
Corte; Southampton UK, Dr J Hell; 
Uppsala Sweden, Prof P Enblad; Torino 
Italy, Dr L Mascia; Vilnius Lithuania, Prof 
E Jarzemaskas; Zurich Switzerland, Prof 
R Stocker 

Corresponding Author: 
Ian Piper 
Brain-IT Group Coordinator 
Intensive Care Monitoring 
Dept. Clinical Physics, 5th Floor 
Institute of Neurological Sciences 

Southern General Hospital 
1345 Govan Road, Glasgow, UK, 

G514TF 
Tel:+44(0)141-201-2595 
Fax: +44(0)141-201-2592 
Email: ipiper@clinmed.gla.ac.uk 

 



 
 
 

Ian Piper et al           Brain Monitoring (BrainIT)          27 

 
 
 

Table 1 
Demographic and Clinical Features of Feasibility Study Data set (n = 199) 

 

Sex  TCDB 
(Worst) 

 

Male 162 Diffuse1 9  
Female 37 Diffuse2 51 

Age  Diffuse3 34 
Mean 36.1 Diffuse4 12 
Range 4-83 Mass 60 

 

<14yo 7 

 

Missing 33 
Trauma 

Type 
 GOSe  

RTA 84 1 (Dead) 31 
Pedestrian 16 2 3 

Fall 55 3 35 
Assault 18 4 8 
Sport 6 5 30 
Work 5 6 17 

Missing 14 

 

7 30 

 

 

 

8 24 
 Missing 21 

 
Table 2 

Summary of Data Collected 
 
 

Data Type No. of Fields Avg No. of Rows per Patient 
Demographic 
(eg: PNSH/NSH) 

109 1 

ICU_Monitoring 
(eg: Types of Device/Location…) 

12 15.0 

Neurological Status 
(eg: GCS/Pupils) 

10 42.3 

Other_Clinical_Events 
(eg: Blood Samples, Suction…) 

20 230.9 

Surgery 
 

11 1.4 

Target_Therapies 
 

59 69.6 

Daily_Observations 
(eg: Daily Summaries of Management) 

11 8.4 

Total 232  
 



 
 
 
28          Romanian Neurosurgery (2010) XVII 1: 12 - 33 

 
 
 

Table 3 
Monitoring Data Distribution 

 
Channel Number of Patients 

BP (blood pressure: mmHg;systolic, diastolic, mean) 199 

ICP (intracranial pressure: mmHg;mean) 195 

CPP (cerebral perfusion pressure: mmHg;mean) 195 

HRT (Heart Rate: bpm) 165 

SaO2 (arterial Oxygen saturation: %;pulse oximetry) 164 

Tc (core temperature: degrees C) 149 

CVP (central venous pressure: mmHg; mean) 105 

ETCO2 (end tidal CO2: mmHg) 79 

NIBP (blood pressure: mmHg;systolic, diastolic, 

mean) 

50 

Tp (peripheral temperature: degrees C) 17 

PtiO2 (brain tissue oxygen partial pressure: mmHg)  11 

SjO2 (jugular venous oxygen saturation: %) 10 

CO (cardiac output: ml/hour) 7 

brTemp (brain temperature: degrees C) 3 

PrX (bp-icp reactivity:dimensionless) 1 

 



 
 
 

Ian Piper et al           Brain Monitoring (BrainIT)          29 

 
 
 

Table 4 
Therapy Type Vs Missing “End Times” 

 
Therapy Start Entries End Entries Missing End Entries 
Sedation 1108 499 55% 
Analgesia 1032 574 44% 
Paralysis 741 460 38% 
Volume Expansion 1674 1308 12% 
Inotropes 614 199 68% 
Anti-Hypertensives 63 22 65% 
Anti-Pyretics 788 505 36% 
Hypothermia 22 10 55% 
Steroids 51 6 88% 
Cerebral Vasoconstr. 0 0 --- 
Osmotics (Mannitol) 807 538 33% 
Barbiturates 90 45 50% 
Other 2576 2026 21% 
Totals 9566 6192 35% 

 
Table 5 

Percentage Error Rate by Data Type Class with Description of Common Error Types. 

 
Data Class Error Rate (%) Common Fields with 

Errors 
Laboratory 2 pCO2, FiO2 value wrong 
Demographic 4 Monitoring time on arrival 

at neurosurgery, intubation 
present on arrival at 
neurosurgery wrong 

Neuro Observations 5 Pupil Size, GCSv (code 1 
Vs Unknown code error) 

Monitoring Summary 5 ICP type, ICP Location 
wrong 

Daily Management Summary 5 Infusion type (bolus Vs 
infusion or both), drug 
number (1 or > 1) 

Targeted Therapy 6 Non-standard target, no 
Target specified 

Surgeries 34 ICP placement, Skull #, 
mass lesion wrong 



 
 
 
30          Romanian Neurosurgery (2010) XVII 1: 12 - 33 

 
 
 

 

Table 6 
Monitoring Data Validation Results – Bias (+- 95% CL) Between Nurses Chart 

Recorded Values Vs Computer Collected End Hour Averages 

 
Data Type 

Value ICP 
(mmHg) 

BP 
(mmHg) 

CPP 
(mmHg) 

SaO2  
(%) 

Tc  
(C) 

Bias -0.15 0.16 0.46 0.46 -0.29 
+95%  0.32 1.57 1.81 1.23 0.09 
-95%  -0.62 -1.25 -0.88 -0.31 -0.67 
n 749 558 457 499 223 

 
Figure 1 Graphical representation of the data validation process. Centre staff enter data using client side 

tools such as the hand held PDA. Data is uploaded via the BrainIT web-services and a server-side convertor 
converts data into the series of common data format files which are input into the BrainIT SQL database. A 

validation request tool residing on the database server randomly samples 20% of the data uploaded for each data 
category and generates a validation request file listing the timestamps and data items to be checked by local 

data validators. Data validators move between their designated centres and enter into a data validation tool the 
requested data items from source documentation held in each local centre. The resulting validation data file is 
uploaded to the BrainIT data coordinating centre via the website and using data validation checking software 

tools, the validated data is checked against the data items originally sent from which percentage 
accuracy data is calculated 



 
 
 

Ian Piper et al           Brain Monitoring (BrainIT)          31 

 
 
 

 
 
 

 
 

Figure 2 is a histogram plot showing the quantity and spread of time-series data for the main 
monitored channels: ICP, BP, CPP, CVP, SaO2, Core Temperature, ETCO2 and PtiO2. The number of 
data points sampled per channel ranges from 89,524 for PtiO2 to 1.98 million samples for BPm. (BPm = 

1,979,284, ICPm = 1,748,423, CPP= 1,719,166 , CVPm= 541,524, SaO2 = 1,656,614 , Tc = 1,372,641, ETCO2 
= 502,524, PtiO2 = 89,524 



 
 
 
32          Romanian Neurosurgery (2010) XVII 1: 12 - 33 

 
 
 

 

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Figure 3 Graph showing “One-Off” demographic and clinical data fields with greater than 15% of missing 

data 

 
Figure 4 Pie chart showing the distribution of the 19,461 data validation comparisons which were made 

in proportion to the size of the data received with the largest number checked in laboratory data (5,667) 
and the least in the surgery data (567) 



 
 
 

Ian Piper et al           Brain Monitoring (BrainIT)          33 

 
 
 

 
Figure 5 Scatter plot of computer monitored minute by minute ICP data from an example patient 

showing the data averaged over 60 minutes (ICPavg) plotted against nurses chart end hour values 
(ICPvalid). Linear regression best fit R2 value = 0.9773 

 
Figure 6 Altman and Bland plot from an example patient showing the average bias (-0.15 mmHg) and 

95% confidence limits (0.12, -0.45) for the computer monitored end hour averaged data Vs the nurses chart 
end hourly recorded values collected by the validation nurses