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Accuracy of levelling intraventricular collection drainage systems.


When a drain is inserted into the ventricles for diagnostic or intracranial pressure (ICP) relief purposes the system must be levelled appropriately. A two-part study was conducted to investigate the ability of registered nurses to accurately level an intraventricular drainage system to a patient's anatomical landmark using visual checks only. The second part of the study was conducted to evaluate if use of a tool improved levelling accuracy and to compare levelling accuracy of two tools. The tools studied were a carpenter's level (the facility's current tool) and a laser levelling device which has been designed by the two researchers and colleagues.

Registered nurses working in an intensive care unit or on an acute neuroscience inpatient unit voluntarily participated in the study. Each participant completed levelling accuracy trials as well as demographic and an ICP monitoring knowledge questionnaire. Methodology employed, accuracy results and analysis of factors impacting accuracy are presented.


Critically ill neuroscience patients may have intraventricular drains (ventriculostomies) inserted as an aid to diagnosis and management. To place the drain, a neurosurgeon introduces a catheter, via a burrhole in the skull, into the lateral ventricle. The lateral ventricles are the primary site of cerebrospinal fluid (CSF) production and the largest intracranial reservoir of CSF. Once placed, the catheter can be connected to a transducer for continuous pressure monitoring or to an external collection system for drainage. An intraventricular drain can also be used to facilitate diagnosis of increased ICP, identify a state of decreased intracranial compliance, or instill intrathecal medication. Although other routes may be used to diagnose or monitor intracranial pressure (ICP) only the intraventricular catheter has therapeutic capabilities through its ability to divert CSF.

When an intraventricular drain is used to divert the CSF, the collection system is set at a prescribed height above the outlet of the lateral ventricles at the interventricular foremen of Munro. This allows CSF to drain whenever the intraventricular pressure exceeds that set by the height of the collection system. Once the intraventricular CSF pressure equalizes, flow into the collection system ceases. Thus, accurate placement of the collection system is critical for a diagnosis of ICP, control of the pressure within the ventricular and intracranial compartments and the ability to maximize intracranial compliance.

When the intraventricular drain is inserted and the desired height of the collection system is determined, management of the patient with a ventricular drainage collection system becomes a nursing responsibility. To accomplish accurate placement of the collection system the nurse is first required to adjust the height of the collection system such that its zero point is level with the interventricular foremen of Munro. The external landmarks that approximate the foremen are varyingly described as the center of the head, the outer canthus of the eye or the external auditory meatus. Secondly, the nurse must adjust the primary collection system to the prescribed height above the zero point. Although both steps are important for correct CSF drainage, the ability to level the system accurately was the focus of interest in these studies. Readjustment to the zero point must be made whenever the patient's position changes relative to the collection system to ensure correct pressure readings and CSF drainage.

Purpose of the Study

Invasive intracranial monitoring occurs infrequently in the study hospital, 25-30 times/year; the intraventricular catheter is used exclusively to monitor and treat acutely increased ICP. Typically intraventricular drains are maintained as continuous drainage systems, open to a collection system at a prescribed height. It has been standard practice to level the drainage collection system with the assistance of a carpenter's level prior to adjusting the height of the collection bag or cylinder. Frequent readjustments may be required and the carpenter's level is awkward and may not be immediately available. Therefore, visual checks may be used for many of the levelling adjustments. A decision was made to investigate the accuracy with which nurses were able to level ventricular drainage collection systems. The first study hypothesis was: registered nurses are NOT able to accurately level a ventricular drainage collection system to patients' anatomical landmarks using visual checks. After data analysis it was evident that a second part to the study was indicated, evaluating levelling accuracy using a tool. The second part was designed to assess levelling accuracy using two tools - a standard carpenter's level and a laser levelling device. The hypothesis for the second part of the study was that use of either levelling tool will improve accuracy of levelling a ventricular drainage collection system. In the second part of the study additional outcomes of time to level and nurses' ratings of ease of use and patient safety were also measured.

Literature Review

The literature search was conducted using the terms intraventricular drainage/ventriculostomy and hemodynamic monitoring phlebostatic axis. No articles were found that described the accuracy with which nurses could visually "level" an intraventricular drain collection system or a transducer for either ICP or hemodynamic monitoring. A number of articles and texts which outlined the nursing management of ventricular drains cautioned that the transducer or drainage collection system must be accurately zeroed and placed to assure correct pressure readings and drainage.[1,5,6,8,10,11,13] Cummings described the importance and technique for zeroing and placing the collection system but failed to specify the tools required to carry out the "levelling" itself.[3] Rudy suggests a carpenter's level may be helpful[9] for accurate placement.

Similarly, articles reviewing management of hemodynamic pressure monitoring systems discussed the importance of accurately determining the zero point.[2,7] The benchmark study that provided the physiological evidence for the phlebostatic axis[12] stated the use of a level was not necessary for accurate determination but did not provide evidence for this counsel.

In summary, the literature emphasized the importance of accurate determination of the zero reference point and subsequent placement of the transducer and/or collection system. Although most authors used the term "level," only one article provided recommendations regarding a specific levelling tool - the carpenter's level. Moreover, there was no research evidence to determine the accuracy with which nurses were able to level the collection systems for extraventricular drainage, either visually or with the carpenter's level.

Research Questions

The study addressed the following questions:

Part 1

* Are registered nurses able to accurately level intraventricular drainage collection systems using visual checks?

Part 2

* Does the use of a carpenter's level or a laser levelling device improve accuracy of levelling intraventricular drainage collection systems?

Operational definitions are listed in Table 1.
Table 1. Operational Definitions

Accurately: Within 2 centimeters of identified or
 standard zero point

Ventricular drain Codman II extraventricular drain
collection system: collection system

Visual checks: Any technique that does not involve the
 use of a carpenter's level or laser
 levelling device; may include use of
 drainage system tubing, pens, nurse's
 arm, etc.

Carpenter's level: Standard bubble to ascertain level or

Laser levelling device: Levelling tool, developed by the
 researchers and colleagues that attaches
 to the extraventricular drain collection
 system by means of a modified clamp and
 uses laser light to ascertain level or
 alignment (Fig 1).


The studies were carried out in a vacant patient room at a 450-bed academic health center in southwestern Ontario. Three mock patients (resuscitation mannequins) were each placed in the middle of a standard hospital bed with a small pillow under the head. The beds were 90 cm wide and 86 cm high at top of mattress level with the head of the bed elevated 30 degrees (as determined on manufacturer's frame gauge). Each of the "patients" had a full head dressing with ears exposed. The Codman II extraventricular drain collection system was secured to the "patient's" head and extended from the head dressing.

For Part 1 the collection system was hung from a portable intravenous pole at the bedside using the attached string and "Cord loc[R]" locking mechanism. For Part 2 the collection system was attached to a portable intravenous pole by means of a clamp manufactured by Codman for this purpose which had been modified by the researchers to allow attachment of the laser levelling device. Parts 1 and 2 used different suspension tools for the collection system; the laser levelling device used in Part 2 required the clamp for attachment. The collection systems were placed at random heights with the drip chamber at zero and all stopcocks open to the collection system. Each study was conducted over a 24-hour period for the investigators convenience.

Accuracy was determined by the two researchers working as a team. One researcher extended the carpenter s level from the "patient's" external auditory meatus to the collection system and adjusted the level until it was level with the horizontal. The second researcher then used a set square on or under the level to determine the collection system's vertical variance (in cm) from true level. To establish intra rater reliability the researchers' ratings of variance from zero was tested for consistency by blinded evaluation and re-evaluation. Three collection systems were hung at random heights and scored for accuracy. Placement of one of the collection systems was then altered and the researchers again scored all three placements for accuracy. The researchers repeated the levelling activity for a total of 6 trials. Collection systems that had height adjustments were appropriately scored differently (2/2 times) and scoring of the systems which had not been adjusted remained consistent 3 of 4 times. On 1 of 4 occasions a system that had not been moved was scored differently (zero variance vs 1 cm) but according to the operational definition would still be deemed accurate.

Participant Selection

All registered nurses who worked in the intensive care unit (ICU), neuroscience special care unit (NSCU) or the acute unit in the study periods were eligible. This included full-time, part-time and casual nursing staff members, regardless of years of nursing experience or experience with ventricular drains.

The ICU is a 26-bed general unit where medical and surgical patients, including neuroscience patients requiring ventilatory assistance receive care. The neuroscience unit has 60 beds for patients with a variety of neurological and neurosurgical problems. Included in the 60 beds is a 6-bed neuroscience SCU for acutely ill neuroscience patients who require continuous observation but do not require mechanical ventilation assistance.

The investigators met with groups of eligible staff members to explain the purpose of the study and to provide a letter of information to read. The following day, the investigators reapproached staff. If verbal consent was given, a time was negotiated to visit the study site for participation. On arrival at the study site, the letter of information was reviewed, questions answered and written consent obtained. Participants were recruited until the required sample size was achieved.

Study Design

Part 1

In Part 1 the participants were asked to accurately level a ventricular drainage system using the visual method at 3 work stations. Participants were given written instructions to "keep ventricular drain open at 10 cm of water" with no patient anatomical zero point being specified. An opportunity to read the instructions on the Codman II ventricular drain collection system was provided. Study participants were observed at the three work stations by one of the investigators and any "levelling behaviors" (such as bending down to eye level, extending drainage tubing, pens or arms between the patient and the collection system) were noted. Participants were able to use any tools available at the bedside (eg, drainage tubing, pens) to assist the zeroing activity.

The participants then exited the room and completed a demographic and knowledge questionnaire. The two researchers checked the accuracy of the levelling of the three drainage collection systems using a carpenter's level and a set square. Variance was recorded, the collection systems height was randomly readjusted on the pole, and the collection cylinder height returned to zero.

The same participants then returned to the study room and were given written instructions stating: "keep ventricular drain open at 10 cm of water" with "use external auditory meatus as the zero point" as added instructions. The nurse then proceeded through the three work stations. Again, each nurse was observed and levelling behaviors noted. Participants then exited the study site and the accuracy of levelling was again scored.

Part 1 resulted in six levelling trials per participant (N = 33); 3 with no anatomical landmark identified and 3 with an anatomical landmark identified.

Part 2

In the second study, a different group of participants (N = 31) was asked to accurately level the drain using the carpenter's level and the laser levelling device (Fig 1). The participants were given written instructions to "keep ventricular drain open at 10 cm of water. Use external auditory meatus as the zero point."


In the first three trials of Part 2, the participant was asked to use the supplied carpenter's level to level the system (standard practice in the study hospital). After three levelling events, the participant exited the room and completed the demographic and knowledge questionnaire while the researchers scored levelling accuracy. In the later three trials, the participant was asked to use the laser levelling device. Because few participants had used the laser in clinical practice, all were verbally briefed regarding its use prior to completing this phase of the study. Each of the six attempts with a levelling tool was timed to provide an additional outcome measure. Accuracy was scored by the researchers using a carpenter's level and set square. Finally each participant rated the levelling tools on variables of ease of alignment, manual dexterity required and feeling of safety when using with patient.

Ethical Considerations

The proposed studies were approved by the Health Science Centre's Nursing Research Committee. In addition, the nursing manager of the neuroscience unit and the nursing coordinators of the neuroscience unit and the ICU were given an outline of the proposed study. Nursing staff on the eligible units were recruited on a voluntary basis. Because one of the investigators had direct line authority in ICU, participants from this area were recruited and observed in the study area by the other researcher to maximize participant comfort.

Results and Discussion

In Part 1, 33 registered nurses participated. In Part 2, 31 registered nurses participated. In both studies, the majority of the participants were employed in the ICU and most worked full time. Years of nursing experience varied from less than one year to greater than 15 years with a greater number of participants in the Part 1 study having only 0-5 years of experience in nursing than Part 2 participants (p = .03). Comparative demographics are summarized in Table 2.
Table 2. Comparison of Participant Demographics
Between Part 1 and Part 2

 Part 1 (N=33) Part 2 (N=31)
 visual only levelling tool

Area of Work
 ICU 21 22
 NSCU 3 5
 Neuro Unit 9 4

Employment Classification
 Full-time 22 24
 Part-time 6 5
 Casual 5 2

Years Experience in Nursing
 0-5 13 4
 6-10 8 11
11-15 7 5
>15 5 11

#Expereiences with ventricular
drains in past 2 years

0 10 9
1-5 23 19
6-10 -- 2
>10 -- 1

# Expereinces with other lines
requiring zeroing in past 2 years

0 3 1
1-5 6 8
6-20 6 6
21-50 5 2
>50 16 14

 Difference Chi Square
 (unless specified)

Area of Work
 ICU p=.72
 NSCU p=.636 (F)
 Neuro Unit p=.624

Employment Classification
 Full-time p=.498
 Part-time p=.909
 Casual p=.475 (F)

Years Experience in Nursing
 0-5 p=.03(*)
 6-10 p=.487
11-15 p=.841
>15 p=.112

#Experiences with ventricular
drains in past 2 years

0 p=.871
1-5 p=.657
6-10 p=.445 (F)
>10 p=.484 (F)

# Expereinces with other lines
requiring zeroing in past 2 years

0 p=.141 (F)
1-5 p=.150
6-20 p=.412
21-50 p=.475 (F)
50 p=.988

(*) statistically significant

(F) Fisher's Exact Test

Part 1 revealed that nurses were unable to accurately (within 2 cm) place ventricular drainage collection systems using visual checks alone. Figure 2 depicts the significant variance in placement over six trials for each of 33 participants (variance 0-19 cm, mean 4.4, SD 3.3) When an anatomical reference point was provided, variance decreased and accuracy improved significantly (variance 0-11cm, mean 3.8, SD 3.0, p = .02) (Fig 3). Choosing a standard reference point appears to be a prerequisite for consistency in placement.


Variables examined for influence on accuracy included: employment classification, areas of work, number of years of experience in nursing, number of times caring for a patient with a ventricular drain or other line requiring zeroing in the past two years, attendance at ventricular drainage collection system inservice and number of levelling behaviors used. When the anatomical landmark was provided in the written instructions only two variables improved accuracy of visual levelling: full-time employment (p [is less than] .05) and greater than 5 years of nursing experience (p [is less than] .05). Other variables were not statistically significant (Table 3).
Table 3. Significance of Variables Studied - Part 1 and Part 2

Variable Part 1 - Visual Anatomical
 Landmark Given N=33

Area of Work: ICU vs. Other .459 (m)
Employment: Full-time vs other <.05 (D*)
Years of experience in nursing
 [is less than or equal to]
 vs 5 years <.05 (D*)
# Experiences with ventricular
 drains in past 2 years: 0 vs >1 .744 (m)
Experience with other lines requiring
 zeroing past 2 years:
 [is less than or equal to] 20 vs >20 .489 (m)
Attended inservice on ventricular
 drain: Yes vs No .980 (m)
# Levelling behaviors: 3 vs <3 .737 (t)

Variable Part 2 - Tool Used

Area of Work: ICU vs. Other .691 (m)
Employment: Full-time vs other .786 (m)
Years of experience in nursing
 [is less than or equal to]
 vs 5 years <.05 (m*)
# Experiences with ventricular
 drains in past 2 years: 0 vs >1 .133 (m)
Experience with other lines requiring
 zeroing past 2 years:
 [is less than or equal to] 20 vs >20 .152 (m)
Attended inservice on ventricular
 drain: Yes vs No .227 (m)
# Levelling behaviors: 3 vs <3 n/a


(*) = significant (t) = t test (m) = Mann-Whitney Rank Sum Test (D) = Dunn's test

In Part 2 when a tool was used, levelling accuracy improved significantly (Fig 4). Overall accuracy with a levelling tool was clinically and statistically (p [is less than] .05) better than visual levelling only (Table 4). However participants between Part 1 and Part 2 are not entirely comparable. Demographic analysis reveals that participants in Part 1 were more likely to have [is less than] 5 years experience in nursing than were participants in Part 2 (p = .03) and this variable did influence accuracy in both studies (Table 3). Analyzing this relatively inexperienced subgroup alone (participants with 0-5 years experience in nursing), the use of a tool continued to significantly improve accuracy over visual levelling (carpenter's level p = .009, laser levelling device p = .03) (Table 5). Additionally, in the most experienced group of participants, those with [is greater than] 15 years experience, use of a tool also improved accuracy (carpenters' level p [is less than] .001, laser levelling device p [is less than] .001). Despite differences in populations between Parts 1 and 2, it appears that use of a tool is superior to visual levelling.
Table 4. Accuracy of Placement of Collection System
Using Visual Carpenter's Level or Laser Levelling Devices

 Visual Carpenter's Laser Levelling
 Level Device

Mean Variance
from zero point (cm) 4.4 1.3 0.9
SD 3.3 2.2 0.8
Range (cm) 0-19 0-16 0-5

Visual vs carpenter's p<.05
Visual vs laser level p<.05
(Dunn's multiple comparison test)

Table 5. Accuracy of Placement of Collection System Using Visual Carpenter's Level or Laser Levelling Devices (Less than 5 years nursing experience)
 Visual Carpenter's Level
 n=11/33 n=4/31

Mean variance
from zero point (cm) 2.3 1.8
SD 2 04.5
Range (cm) 0-8 -16

 Laser Levelling
 Device n=4/31

Mean variance
from zero point (cm) 1.1
SD 1.3
Range (cm) 0-5

Visual vs carpenter's p=.009

Visual vs laser level p=.03


In comparing tools, less time was required to level the ventricular collection system with the laser levelling device (range 9.34-129.59 seconds, mean 34.79, SD 19.58) than with the standard carpenter's level (range 1.25-115.81 seconds, mean 45.43, SD 22.68). Although the difference was statistically significant (p [is less than] .001, ANOVA) it is unlikely to be clinically significant.

Nurses also indicated a preference for the laser levelling device over the traditional carpenter's level. Ratings for ease of alignment, manual dexterity required and feeling of safety when using with patients were consistently more favorable for the laser levelling device than for the carpenter's level.

Although the research focus concerned the ability to accurately zero ventricular drainage collections systems, additional information was obtained that had significant patient care implications. Data obtained from Part 1 demographic and knowledge questionnaire indicated that several nurses identified the mid chest or mid axillary line as the accepted external anatomical landmark for levelling ventricular drainage collection systems (n = 5). Others failed to correctly adjust the collection cylinder once the level had been assessed for zero (or set the collection chamber top at 10 cm and then zeroed to the top of the collection cylinder, instead of the zero point (n = 9). The researchers interpreted these behaviors as indicative of inexperience and lack of understanding of the principles of ICP monitoring and ventricular drainage, and/or the collection system itself. A minority (14/33, no response 2/33) had attended a recent inservice on the extraventricular drainage collection system.

Demographic data also confirmed that some staff members were inexperienced in the care of patients with intraventricular drainage collection systems. Because of the numbers of staff members involved in the care of neuroscience patients, and the infrequency with which intraventricular drains are used at the study hospital, it was identified that special teaching strategies or tools needed to be employed to ensure safe patient care. A core team was developed to act as expert resources for nursing staff in the ICU and the neuroscience unit; a bedside card and wall-mounted posters outlining key concepts were produced and made available on the unit for reference.


The significant demographic difference in years of experience between participants in the two parts of the study (Table 1) make it difficult to directly compare the three levelling techniques (visual, carpenter's level and laser levelling device) for accuracy. Although inexperience impacts accuracy, subgroup analysis reveals that levelling tools continue to positively impact accuracy regardless of years of experience.

The study results may also be specific to the institution and the nurses who participated. Because relatively few patients have intraventricular drains, nurses had limited experience which may have significantly affected results.

Third, studying a single system limits the ability to generalize results. The Codman II ventricular drainage collection system was the only system studied. It is difficult to determine if other collection systems would have been levelled more accurately because of design variations.

Fourth, it is not known whether the definition of accuracy chosen by the researchers was correct. An acceptable variation of +/- 2 cm. was chosen based on the researchers' clinical experience but no data in the literature was found to support or refute this measure. Use of mock patients may also influence results and their interpretation.

Finally, the role of knowledge deficit is difficult to separate from inaccuracies in placement. Some of the behaviors demonstrated by the nurses (particularly evident in Part 1) indicated a lack of knowledge of the principles of ventricular drainage. The distinction between knowledge deficit and inability to level the system accurately was difficult to determine but were certainly interrelated. Further study is indicated with comparable populations, other centers and collection systems.


The data findings support both hypotheses. Registered nurses are unable to accurately level a ventricular drainage collection system using visual checks alone. Moreover, use of a tool, either the standard carpenter's tool or the newly developed laser levelling device significantly improved levelling accuracy in this study. Use of the laser levelling device consistently resulted in more accurate levelling attempts (Table 3) in the least amount of time. Participants also rated the laser levelling device superior to the carpenter's level for ease of use, dexterity required and patient safety.


We wish to gratefully acknowledge the financial support of the Division of Advanced Nursing Practice and Patient Centred Care for Part 1, and Greenshields Canada for a generous grant supporting Part 2. We are also indebted to our collaborators in the development of the laser levelling device Robert Petrosenko, P Eng, and Mark Studenny, Reg N.


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Questions or comments about this article may be directed to: Deborah Bisnaire, RN, BNSc, MHSc, CNNC, London Health Sciences Centre, University Campus, 339 Windermere Road London, Ontario, N6G 3Y7, Canada. She is an expanded role nurse with neurosurgery.

Lynda Robinson, RN, MSCN, is a manager of cerebral care at London Health Sciences Centre, University Campus, in London, Ontario, Canada.

Copyright [C] American Association of Neuroscience Nurses 0047-2603/97/2904/0261$1.25
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Author:Bisnaire, Deborah; Robinson, Lynda
Publication:Journal of Neuroscience Nursing
Date:Aug 1, 1997
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