University of Groningen The management of ... · High variability and low irradiance of phototherapy devices in Dutch NICUs 115 Introduction Unconjugated hyperbilirubinaemia is very

University of Groningen

The management of hyperbilirubinemia in preterm infantsVader-van Imhoff, Deirdre Elisabeth

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Chapter 7

High variability and low irradiance of

phototherapy devices in Dutch NICUs

Deirdre E. van Imhoff, Christian V. Hulzebos, Maaike van der Heide, Vera W. van den Belt,

Henk J. Vreman, Peter H. Dijk,

and the BARTrial Study Group

Arch Dis Child Fetal Neonatal Ed. 2012 May 18. (Epub ahead of print)

114

Abstract

Objective: To evaluate phototherapy practices by measuring the irradiance levels of phototherapy (PT) devices.

Design: Prospective study

Setting: Tertiary neonatal intensive care units

Patients: None

Interventions: Irradiance levels of PT devices used in the ten Dutch NICUs were measured according to the local PT practice patterns. The irradiance levels of all overhead and fibre optic PT devices were measured with a radiometer using an infant silhouette model.

Results: Eight different PT devices were used in the ten NICUs; five were overhead devices and three fibre optic pads. The median (range) irradiance level for overhead PT devices was 9.7 (4.3 – 32.6) µW/cm2/nm and for fibre optic pads 6.8 (0.8 – 15.6) µW/cm2/nm. Approximately 50% of PT devices failed to meet the minimal recom-mended irradiance level of 10µW/cm2/nm. Maximal irradiance levels for overhead PT spot lights were inversely related to the distance between device and infant model (R2=0.33). The distances ranged from 37 to 65 cm.

Conclusions: PT devices in the Dutch NICUs show considerable variability with of-ten too low irradiance levels. These results indicate that suboptimal PT is frequently applied and may even be ineffective towards reducing TSB levels. These results underline the need for greater awareness among all health care workers towards the requirements for effective PT including measurements of irradiance and distance.

High variability and low irradiance of phototherapy devices in Dutch NICUs 115

Introduction

Unconjugated hyperbilirubinaemia is very common in newborn infants and may result in bilirubin neurotoxicity. PT is an effective and safe treatment for reducing total serum bilirubin (TSB).(1)

Specific TSB thresholds to start PT treatment have been defined in several in-ternational guidelines.(2–4) These guidelines contain also recommendations for the effective irradiance level of PT, which is strongly related to the decrease in TSB.(2,5) The irradiance level within the effective bilirubin photo degradation spectrum (400–520 nm with a peak at 460 nm) to a sufficient treatment area can be measured with a radiometer. The American Academy of Pediatrics (AAP) recommends that effective PT should occur with a minimal irradiance level of 8 to 10 µW/cm²/nm.(2,6) Adherence to this recommendation has not been investigated thoroughly. Only a few studies from developing countries measured low irradiance suggesting that PT is not always applied effectively.(7–9) Limited resources with inferior light sources, maintenance constraints, inconsistent power supply and lack of awareness of health care workers are probably the most important barriers to effective PT.(10) We hy-pothesize that in the technically advanced NICUs in industrialised countries these barriers do not exist and that PT is applied more effectively. Therefore we measured the irradiance levels of PT devices in the ten Dutch level III Neonatal Intensive Care Units (NICUs).

Methods

All ten Dutch level III NICUs were invited to be visited for measurements of irradi-ance levels under practice conditions. At least one sample of each type of PT device in combination with each type of incubator in use in each NICU was included.

The PT devices that were studied included overhead PT devices with diffuse light or spot patterns illumination using fluorescent tube or halogen lamps, and underneath or contact devices using halogen lamps with fibre optic cables and pads (Table 1).

116

Tabl

e 1. P

hoto

ther

apy d

evic

es, ir

radi

ance

leve

ls an

d di

stan

ces.

PT d

evic

eN

ICU

s n

Irra

dia

nce

pro

vid

ed

by

MD

A o

r m

anufa

cture

r ra

ng

es

(µ

W/c

m2 /

nm

)#

Irra

dia

nce

m

easu

red

m

ed

ian (

rang

e) n

(µ

W/c

m2 /n

m)

Dis

tance

re

com

mend

ed

by

manufa

cture

r (c

m)

Dis

tance

m

easu

red

med

ian (

rang

e)

(cm

)

Ove

rhead

dev

ices

:

Ohm

ed

a S

pot

Lam

p1

852–

788.6

(4

.6–1

4.0

) 18

38–6

04

6 (

37–6

5)

Gir

aff

e S

pot

Lite

23

29–5

819

.5 (

18.1–

19.7

) 4

38–6

04

6 (

38

–53)

Med

ela

Lam

p3

114

–31

9.6

(8.4

–10

.8)

225

–45

40

(38

–42)

Drä

ger

Unit

40

00

42

14–2

721

.4 (

8.3

–32.

6)

530

–40

50

(38

–50

)

Fibre

Op

tic p

ad d

evic

es:

Ohm

ed

a li

ght5

315

–35

5.9

(1.8

–6.4

) 3

––

Ohm

ed

a p

lus5

632

6.5

(0

.8–1

4.0

) 6

––

Ohm

ed

a h

igh

54

15–3

514

.9 (

9.6

–15.6

) 4

––

1. Date

x-O

hm

ed

a P

T S

pot

Lam

p (

H):

Ohm

ed

a M

ed

ica

l, C

olu

mb

ia, M

D, U

SA

, 2.

Gir

aff

e S

pot

PT L

ite (

H):

Gener

al E

lect

ric

Hea

lthca

re, L

aure

l, M

D, U

SA

, 3. M

ed

ela

PT

lam

p (

F):

Med

ela

AG

Med

ica

l Tech

nolo

gy,

Baar,

Sw

itze

rland

, 4

. Drä

ger

PT

Unit

40

00

(F):

Drä

ger

Med

ica

l, Lü

beck

, Ger

many,

5. D

räg

er-H

eraeus

PT U

nit

80

0 (

GD

): D

räg

er M

ed

ica

l, Lü

beck

, Ger

many,

6

. Ohm

ed

a (

H a

nd F

O):

Ohm

ed

a M

ed

ica

l, C

olu

mb

ia, M

D, U

SA

. Ty

pe P

T la

mp

: H =

ha

log

en, F

= f

luore

scent, G

D =

ga

llium

dis

charg

e b

ulb

and

FO

= f

ibre

op

tic

# Ir

r ad

iance

was

calc

ulate

d f

rom

data

pro

vid

ed

by

the M

ed

ica

l Dev

ice A

gency

(M

DA

) b

y d

ivid

ing

irra

dia

nce

in m

W/c

m2 b

y th

e s

pect

ral r

ang

e (

whic

h

was

40

0–5

50

nm

= 150

), t

he lo

west

and

hig

hest

va

lues

are

pre

sente

d.(

11–1

5)


A silhouette model representing a preterm infant was used to measure the irradiance levels of overhead PT devices. Five measurement points in craniocaudal direction were marked on the model representing the head, trunk, abdomen, knees and feet (3, 12, 18, 23 and 33 cm, respectively, figure 1). Local NICU nurses placed the silhouette model in the incubator and installed the PT device above or on top of the incubator as they would do in daily clinical practice. The type of PT device, type of incubator, the distance between PT device and silhouette model were noted. The irradiance levels of underneath contact fibre optic PT pads were measured on top of the rou-tinely used disposable cover at three predefined measure points (12, 18 and 23 cm respectively, figure 1).

Figure 1. Silhouette models with measurement points used for irradiance level measurements of overhead PT devices and underneath fibre optic PT devices.

A. Irradiance levels of panel and spot overhead PT devices were measured at the five indicated points in craniocaudal direction on a 35 cm long silhouette model representing a preterm infant.

B. For underneath fibre optic PT devices, irradiance was measured at the 3 indicated points on a disposable cover.

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A Dale40 Phototherapy Radiometer (Fluke Biomedical, Everett, WA, USA) was used to measure the energy distribution. This radiometer is designed to measure light radiation of fluorescent lamps in the blue part of the spectrum with a band range of 429 to 473 nm and peak sensitivity at 453 nm. The measured energy divided by the bandwidth (width of sensitivity spectrum at 50% of maximum) of 44 nm as is reported by the manufacturer resulted in the integrated irradiance (µW/cm2/nm) delivered by the device at the measured distance from the light exit point.

Five replicate irradiance measurements were performed at each of the five or three measurement points (as appropriate) for each PT device studied. The mean values of the five replicates were used for further calculations. For each PT device type tested, the means of all measurement points were averaged to one mean ir-radiance level, in agreement with the definition of the ‘effective surface area’ by the International Electrotechnical Commission and the recommendation of the AAP.(2) For each NICU, the mean irradiance levels per device tested were used to calculate medians, quartiles and outliers to be represented in box plots. To evaluate the effect of distance on irradiance of PT spot devices, the irradiances of the measurement points the closest to the devices were used (which are the measurement points with the highest irradiance levels).

Microsoft Office Excel (Microsoft Corporation, Redmond, Washington) and SPSS for Windows (version 16.0, Chicago, IL) were used for data entry and analysis.

Statistical tests: Alternate T-test was used for comparing the irradiance on the five measurement points on the model for PT tube lights versus PT spot lights. A p value < 0.05 was considered statistically significant.

Results

All ten level III Dutch NICUs participated. Eight types of PT devices were found to be in use; five types of overhead PT devices and three types of underneath fibre optic PT pads (table 1). Five types of incubators were used (Giraffe, Dräger Caleo, Dräger 8000, Vita and Hill Rom Airshield). We measured a total of 42 PT device – incubator combinations (29 overhead and 13 fibre optic devices).

Figure 2 shows the variation in irradiance in each NICU of all PT devices together. The irradiance levels ranged from 0.8 to 32.6 µW/cm2/nm.


0

10

20

30

40

1

NICU

Irra

dia

nce

(µW

/cm

2 /nm

)

2 3 4 5 6 7 8 9 10 All

Figure 2. Irradiance levels of all phototherapy devices in the ten NICUs. Irradiance levels for all PT devices (n=42) in each of the ten NICUs and for all NICUs together. The median is marked by the horizontal line in the box. The boxes are limited by the 25th and 75th percentile. The whiskers (┴) represent the lowest and highest irradiance levels measured within 1.5 interquartile distance below or above the box. Outliers (○) are depicted separately and represent irradiance levels between 1.5 and 3 interquartile distance below or above the box. The minimal recommended irradiance level of PT (8 – 10 µW/cm2/nm) is represented by the grey horizontal line.

Figure 3 shows the ranges in irradiance levels for all the overhead PT devices and fibre optic pads. The median (range) irradiance level for overhead PT devices was 9.7 (4.3 – 32.6) µW/cm2/nm and for fibre optic pads 6.8 (0.8 – 15.6) µW/cm2/nm. Irradiance levels were lower than 10 µW/cm2/nm in 52% of the overhead and 69% of the fibre optic underneath PT devices. Table 1 shows the median irradiance level for each type of PT device and the calculated irradiance as provided by the manufacturer and/or Medical Device Agency, together with the recommended and measured distances.(11–15)

120

0

10

20

30

40

Overhead PT Underneath PT

Irra

dia

nce

(µW

/cm

2 /nm

)

Figure 3. Irradiance levels of overhead PT and underneath fibre optic PT devices. Irradiance levels of overhead PT (n=29) compared to underneath fibreoptic PT (n=13) devices. The median is marked by the horizontal line in the box. The boxes are limited by the 25th and 75th percentile. The whiskers (┴) represent the lowest and highest irradiance levels measured within 1.5 interquartile distance below or above the box. Outliers (○) are depicted separately and represent irradiance levels between 1.5 and 3 interquartile distances below or above the box. The minimal recommended irradiance level of PT (8 – 10 µW/cm2/nm) is represented by the grey horizontal line.

The distance between PT-device and silhouette model ranged from 37 to 65 cm. Figure 4 shows the significant relationship (R2=0.33) between the increasing distance and lower irradiance levels of PT spots included in this study. We found no significant differences between the distances at which the PT devices were positioned per type of incubator or type of PT device (data not shown).


0

10

20

30

40

30

y=90.826 e–0.031x

R2=0.3256

Distance between PT device and silhouette model (cm)

Irra

dia

nce

(µW

/cm

2 /nm

)

35 40 45 50 55 60 65

Figure 4. The relationship between irradiance level and distance between PT device and silhouette model of Spot PT devices. Irradiance level corresponding to the shortest distance between the PT device and the measurement point on the silhouette model (and consequently the highest irradiance) for the Ohmeda Spot lights and Giraffe Spot PT Lite lights (n=22). A statistical significant natural logarithmic correlation with a R2 of 0.33 was found between irradiance (y) and distance (x): y=90.826e -0.031x. Distances ranged from 37 to 65 cm and irradiance levels from 7.4 to 41.2 µW/cm2/nm.

Figure 5 shows the mean irradiance level per measurement point on the silhouette model for tube lights compared to spot lights. Irradiance levels were higher for the tube – versus spot PT devices on measurement points 1, 4 and 5 (p=0.058, p=0.03 and p=0.005, respectively), but not on measurement points 2 and 3, indicating a smaller footprint for spot-devices.

122

0

10

20

30

40

1

Measurement point on silhouette model

Irra

dia

nce

(µW

/cm

2 /nm

)

2 3 4 5

Tube lights

Spot lights

p=0.005

p=0.03

p=0.058

Figure 5. Irradiance level per measurement point on the silhouette model for tube and spot overhead PT devices. Irradiance levels for each measurement point on the silhouette model for tube PT devices n=6 (Dräger PT Unit 4000 and Medela PT lamps) compared to spot PT devices n=22 (Ohmeda Spot PT lamp and Giraffe Spot PT Lite). Data represent mean values and standard deviations. P values are the result of alternate T-tests comparisons between tube and spot PT devices.

Discussion

We found a wide variation in irradiance levels of the PT devices in daily clinical use in Dutch NICUs. Approximately 50% of the devices delivered irradiance levels lower than the minimal recommended level of 10 µW/cm2/nm.(2,6) These results indicate that suboptimal PT is often applied and may even be ineffective towards reducing TSB levels. We established that this low irradiance was due to excessive distances between PT device and infant and disappointing performance of PT devices.


We had expected that in NICUs in an industrialised country such as the Nether-lands, PT would often meet the irradiance level that is recommended for effective PT. However, we found that it does not. In fact, our results are not that different from those in developing countries.(7–9) Pejaver et al. studied PT devices among 24 Indian neonatal care centres. Only 31% of 58 PT devices provided an acceptable irradiance level.(7) Similarly, Ferreira et al. found that only 33.3% of the 36 PT devices in Maceió, Brazil, provided an irradiance level of 10 µW/ cm2/nm or more.(8) Owa et al. studied 63 PT devices at 12 nurseries in Nigeria. Only 6% provided an irradiance level of 10 µW/cm2/nm or more, and 75% of less than 5 µW/cm2/nm.(9)

Bhutani et al. described four categories of barriers to effective PT in developing countries that may explain the high percentage of PT devices that produce subop-timal levels of irradiance. Firstly, PT devices may contain inferior light sources with suboptimal spectral range. Secondly, maintenance constraints may result in devices with burned out or missing lights. Thirdly, environmental barriers such as lack of consistent electrical power supply may negatively influence the efficacy of PT. The fourth barrier consists of a lack of awareness of requirements for effective PT among the health care workers that administer PT, and the lack of radiometers to assess the efficacy of PT.(10) While resource-constrainment is probably the most important contributor in the developing countries, lack of awareness of the factors that influ-ence the effectiveness of PT is probably the most important barrier in industrialised countries.

The first factor is the PT device itself and its specifications such as light source, intensity, spectral range and lifetime.(10,16) The light sources vary from fluorescent to halogen lights, gas discharge tubes and gallium nitride light emitting diodes (LED). The number of light bulbs and colour of the light also differ between PT devices. Vari-ous PT devices are used in the Dutch NICUs (table 1). Since these irradiance levels were measured not in a standardized laboratory setting, but in the clinical setting, our results may be different from those provided by manufacturers and agencies that evaluate medical devices like the MDA.(11–14) We think that a clinical evaluation, like ours, may be more veracious than standardized laboratory evaluations.

Maintenance and especially lifetime of the light sources are important for the performance of PT devices, but these were not systematically evaluated in this study. However, NICU nurses were often not aware of the lifetime of the lights, which may have been more prone to suboptimal functioning than expected.

The second factor influencing the effectiveness of PT is the distance between the PT device and the infant. Positioning the PT device as close to the infant as possible increases irradiance levels and consequently the efficacy of PT (figure 4).(6) However, if a specific light source produces too much heat, as could happen with halogen-lamp

124

based devices, close positioning of the lamp to the infant may increase the risk of heat burn.(2,17) Therefore, it is very important to follow the safety instructions of the manufacturer.

In the present study, several clinical variables may have influenced the distance between the infant and the PT devices. Five types of incubators were used, all with different dimensions. Although the height of an incubator limits the minimal distance between PT device and the infant, the type of incubator was not the most important variable that determined the operational distance. We found a broad range of applied distances for each type of incubator, and no clear relationship between the type of incubator and distance or irradiance levels. Apparently, the positioning of the PT devices above the incubator by the NICU nurses was different and contributed in particular to the differences in distances.

The third factor that influences the effectiveness of PT is the amount of surface area of naked skin of the infant that is exposed to a PT light. Firstly, baby hats, diapers and clothes reduce the surface area of naked skin exposed to the light. Furthermore, the positioning of the PT light above the incubator or the degree of dispersion be-tween the light source and the infant affects irradiance. Figure 5 illustrates that the footprints of spot lights have considerably higher irradiance levels in the centre of the light and much less intense irradiance levels at the periphery compared to tube devices.(18) This figure also illustrates that improper positioning of the PT device can seriously reduce irradiance levels.(17)

Our primary goal was not to compare the performance of different types of PT devices, but to compare clinical practice conditions of PT. As such, we chose to mea-sure irradiance with one type of radiometer. PT devices differ in delivered spectrum of light while radiometers differ in the measured spectrum of light. Manufacturers of PT devices recommend the use of radiometers that fit the spectrum of the light deliv-ered by their device. The ideal handheld radiometer that would equally measure the complete and only treatment spectrum of PT light does not yet exist. The radiometer that we used measured irradiance levels with a bandwidth between 429 to 473 nm, which is within the effective treatment bandwidth of 430–490 nm, recommended by the AAP.(2) Irradiance levels are expressed as µW/cm2/nm, which means that the absolute results of the measurements depend on the bandwidth and sensitivity level of the radiometer.(16,19) The irradiance levels of this study may differ from those of other studies or specifications given by the manufacturers of PT devices (table 1). This underlines the need for a universal radiometer.(19)


Conclusion

This study shows that the irradiance levels of PT devices in level III NICUs in an industrialised country, such as the Netherlands, are not that different from subop-timal irradiance levels of PT devices observed in developing countries. Resource-constrained related barriers are probably not the most important in industrialised countries. Awareness and understanding of the factors that influence the efficacy of PT by all health care professionals that buy, apply and maintain PT devices, seems of key importance (table 2). In particular, the distance between PT device and in-fants turned out to be an important factor toward optimising irradiance. Frequently measuring the irradiance levels of PT devices is essential, and using only devices that deliver effective PT under clinical conditions. Finally, our results underline the need for a universal radiometer that measures the clinical relevant irradiance level of all PT devices.

Table 2. Recommendations for effective use of phototherapy

Recommendations

Educate all health care professionals who buy, apply and maintain PT devices about the factors that affect the efficacy of PT.

Measure the irradiance level of your PT devices regularly. The minimal recommended irradiance level is 8 to 10 µW/cm2/nm. Replace lamps that do not deliver.

Match PT devices to incubators in use and place the PT device as close to the infant as is safe and possible. Follow the safety instructions of the manufacturer of the PT device to avoid heat and burns (especially with halogen lights)!

Illuminate as much naked skin of the infant as possible, making sure optimal body tem-perature is maintained.

Use eye protection.

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Funding

This study preceded the Netherlands Neonatology Research Network RCT ‘Reducing bilirubin induced neurological dysfunction in premature newborns: additional use of the bilirubin/albumin ratio in the treatment of hyperbilirubinemia’ (BARTrial: ISRCTN 7446543). The trial was funded by the ZonMW Cost-Effectiveness programme (nr: 94507407)

Acknowledgements

The BARTtrial Study Group members are: Academic Medical Center University of Amsterdam, the Netherlands:

L. van Toledo-Eppinga, MD, PhD. University Medical Center Maastricht, the Netherlands:

A.L.M. Mulder, MD, PhD. Erasmus Medical Center Rotterdam, the Netherlands:

P. Govaert, MD, PhD. Isala Clinics Zwolle, the Netherlands:

R.A. van Lingen, MD, PhD. University Medical Center Leiden, the Netherlands:

E. Lopriore, MD, PhD. Maxima Medical Center Veldhoven, the Netherlands:

J. Buijs, MD. University Medical Center Groningen, the Netherlands:

D.E. van Imhoff, MD; P.H. Dijk, MD, PhD; C.V. Hulzebos, MD, PhD. University Medical Center St. Radboud Nijmegen, the Netherlands:

K.D. Liem, MD, PhD. University Medical Center Utrecht, the Netherlands:

M.J.N.L. Benders, MD, PhD. University Medical Center Amsterdam, the Netherlands:

W.P.F. Fetter, MD, PhD.


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