Variability in the Rate of Milk Flow from Infant Bottle Nipples: Guiding

Variability in the Rate of Milk Flow from Infant Bottle Nipples:
Guiding Decision-Making for Nurses, Parents, and Researchers
* Britt Pados, PhDc, RN, NNP-BC1
† #
n
n
Jinhee Park, PhD, RN2
1
BACKGROUND
Feeding can be physiologically challenging
n
for medically fragile infants.
Milk flow, or the rate of milk transfer from
n
the bottle to the mouth during feeding,
contributes to the extent of physiologic
instability encountered.
There is little current data on milk flow rates
from available bottle nipples.
AIMS
Describe milk flow rates from bottle nipples
n
commonly used to feed infants in the hospital
and after discharge home.
Guide decision-making for nurses, parents,
n
and researchers.
METHODS
Ten each of 38 types of nipples (n=373)
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were tested using a standardized procedure.
Power analysis: 10 nipples of each type
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sufficient for 80% power with an alpha
of 0.05.
Nipple attached to breast shield and
n
positioned at 30 degree angle.
Similac Advance ready-to-feed 20 calorie/
n
ounce formula used for all tests.
60mL Grad-U-feed bottle filled with 50mL
n
of formula.
Formula expressed using breast pump for
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1 minute and the milk transferred recorded.
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2
n
n
*Hayley Estrem, PhDc, RN1
RESULTS
Some nipples were found to have holes that were not open.
nAs formula was exposed to air for prolonged periods of time, it thickened
and reduced flow rate.
n
VARIABILITY IN FLOW RATES
Milk flow varied significantly between different types of nipples, from 2.1
(Enfamil Cross-Cut) to 85.3 mL/min (Dr. Brown’s Y-cut).
There was a wide range in variability in flow rates amongst the nipples
tested. COV ranged from 0.03 (Dr. Brown’s Level 3) to 0.61 (Bionix Level 5).
n
n
Mean
Flow
Rate
(mL/min)
Mean Milk
Milk Flow
Rate
(mL/min)
Coefficient
of Variation
(SD/mean)
Coefficient
of Variation
(SD/mean)
Similac Standard
Similac Slow
Similac Premature
Playtex Ventaire Slow
Pigeon Standard
Pigeon Slow
Pigeon No Drip
Parents Choice Slow
Nuby Medium
NUK
NUK Slow
Medela Calma
Medela Wide Base Slow
Medela SpecialNeeds Feeder
MAM
The First Years Gumdrop
Fisher-Price
First Essentials
Enfamil Standard
Enfamil Slow
Enfamil Preemie
Enfamil Cross-Cut
Dr. Brown's Y-cut
Dr. Brown's Level 3
Dr.Brown's Level 2
Dr.Brown's Level 1
Dr.Brown's Preemie
Difrax
Bionix Level 5
Bionix Level 4
Bionix Level 3
Bionix Level 2
Bionix Level 1
Similac Standard
Similac Slow
Similac Premature
Playtex Ventaire Slow
Pigeon Standard
Pigeon Slow
Pigeon No Drip
Parents Choice Slow
Nuby Medium
NUK
NUK Slow
Medela Calma
Medela Wide Base Slow
Medela SpecialNeeds Feeder
MAM
The First Years Gumdrop
Fisher-Price
First Essentials
Enfamil Standard
Enfamil Slow
Enfamil Preemie
Enfamil Cross-Cut
Dr. Brown's Y-cut
Dr. Brown's Level 3
Dr.Brown's Level 2
Dr.Brown's Level 1
Dr.Brown's Preemie
Difrax
Bionix Level 5
Bionix Level 4
Bionix Level 3
Bionix Level 2
Bionix Level 1
COV
0.1
- Excellent
COV <<0.1
- Excellent
COV
<
0.2
Good
COV < 0.2 - Good
COV < 0.3 - Fair
COV
0.3
- Fair
COV <<0.4
- Poor
COV
>
0.4
Very
Poor
COV < 0.4 - Poor
COV > 0.4 - Very Poor
10
20
30
40
50
Milk Flow (mL/min)
60
70
80
Dr. Brown’s Y-cut nipple tested using standard formula; usually used with
thickened formula.
nOnly negative pressure applied to nipples. The Enfamil cross-cut and
Medela SpecialNeeds Feeder have a slit opening instead of a hole and
likely perform differently during feeding when positive pressure is applied.
n
CONCLUSIONS
0.1
0.2
0.3
0.4
0.5
0.6
Lowest Flow
aa
Similac Standard
aa
Parents Choice Slow
Highest Flow
a, b
d,e
Formula was changed every 10 trials to
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maintain milk consistency.
For nipples requiring bottles of different
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shapes and sizes, efforts made to ensure
consistent hydrostatic pressure.
analysis used to compare milk flow between
nipples.
Non-parametric one-way ANOVA and pairwise
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Wilcoxon rank sum tests, adjusting alpha
to 0.001, used for non-normally distributed
nipples.
b
First Essentials
Bionix Level 2
c
Enfamil Standard
0
2
4
6
8
10
Mean Flow Rate (mL/min)
12
14
0
16
Note. Nipples indicated with the same color bar are of comparable flow rates to one another.
RESEARCHERS
a,a, bb
Dr.Brown's Level 1
Bionix Level 1
Mean and Coefficient of variation (COV, SD/
One-way ANOVA with Duncan’s post-hoc
e
Fisher-Price
5
10
15
Mean Flow Rate (mL/min)
20
Bionix Controlled Flow Baby Feeder
nNipple
and Collar tested separately because interchangeable.
nNipple tests: Levels 2-5 not different from one another.
nCollar tests: Levels 2 and 3 the same. Levels 4 and 5 the same.
nBionix Levels 4 and 5 were among the most variable of all of the
nipples tested.
Dr. Brown’s
nTests
performed with venting system in place.
nAll levels significantly different from one another.
nDr. Brown’s Preemie, level 1, 2, and 3 among least variable of
all nipples tested.
25
30
Note. Nipples indicated with the same color bar are of comparable flow rates to one another.
In the post-hoc analysis, some nipples overlapped between groups. Nipples with mean flow
rates that were not significantly different from one another are indicated by the same letter
to the right of the bar.
COMPARISONS WITHIN BRAND
n
n
b
The First Years Gumdrop
When an infant is ready to be discharged home, choose a nipple of
comparable flow to that used successfully in the hospital.
nIf a baby is having difficulty feeding with the nipples available in the
hospital, purchase a nipple with lower flow and low variability to take
into the hospital for feedings.
n
b
MAM
ANALYSIS
mean) of milk flow (mL/min) calculated for
each nipple.
b
Medela Wide Base Slow
Dr.Brown's Preemie
PARENTS
a, b
NUK
Enfamil Slow
Start with the slowest flow nipple available for vulnerable infants.
nConsider changing to a different nipple of the same type if having a
difficult feeding.
nConsider checking that the nipple hole is open and reapply nipple to
bottle to release suction if not transferring milk.
n
c, d
Nuby Medium
Medela Calma
Medela SpecialNeeds Feeder
NURSES
e
Pigeon Standard
NUK Slow
Samba Micro-Pressure Measurement
System every 50 trials.
GUIDING DECISION-MAKING
b
Playtex Ventaire Slow
Sucking rate and pressure tested using
0.7
COMPARISONS WITHIN CATEGORY
Mean FlowMean
Rate
of “Slow” Flow Nipples (n=9)
Mean Flow Rate
of “Standard”
Flow
Nipples (n=14)
Flow Rates
of "Standard" Flow
Nipples
Flow Rate of "Slow" Flow Nipples
Pigeon Slow
n
Choosing a nipple is an important decision given the wide range of flow
rates of available nipples.
nThe name of a nipple (e.g., slow, preemie) does not always give an accurate
indication of the flow rate.
nVariability in flow rate between and within nipple types is an added challenge
that may contribute to feeding difficulty in vulnerable infants.
n
Note. Nipples are color coded according to category of coefficient of variation.
Pigeon No Drip
Bionix:
qChanging the nipple or collar may inadvertently change milk flow rate even if on same level of flow.
qChanging the flow indicator level may not significantly change flow
delivered.
nDr. Brown’s is the most consistent brand of those tested (all nipples had
excellent or good COV).
nBoth Enfamil Slow and Similac Slow nipples had individual tests that were
faster than some of the Standard flow nipples of these brands.
n
90
Note. Nipples are color coded according to brand.
Similac Slow
DISCUSSION
LIMITATIONS
0
0
William B. Nix, BMET, BA1
OTHER SIGNIFICANT FINDINGS
Mean sucking rate was 110 sucks/minute. nMean sucking pressure was 14.3 mmHg.
MILK FLOW RATES
n
n
Duke University School of Nursing
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Nurses, parents and researchers are faced
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Suzanne M. Thoyre, PhD, RN1
The University of North Carolina at Chapel Hill School of Nursing
SUCKING RATE AND PRESSURE
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with decisions about nipple selection for
bottle feedings.
n
n
Enfamil
nAll
levels significantly different from one another.
nEnfamil Preemie was highest flow of all Enfamil nipples.
nSome Enfamil Slow nipples faster than Enfamil Standard.
Similac
nSimilac
Slow and Standard were not significantly different from
one another.
nSimilac Premature was significantly faster than other Similac
nipples.
nSome Similac Slow nipples faster than Similac Standard.
Medela
nAll
nipple types significantly different.
Poster Produced by the Department of Information & Instructional Technologies, The University of North Carolina at Chapel Hill School of Nursing (HWH 2/14)
In studies evaluating effect of feeding interventions, it is critical to:
qKnow the flow rate of the nipple chosen for the study.
qChoose a nipple with low variability in flow rate to ensure consistency.
qReport the nipple used in the study.
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ACKNOWLEDGEMENTS
This research is supported by †NIH F31
NR011262; *Sigma Theta Tau International
Honor Society of Nursing Alpha Alpha Chapter
Research Award; #James and Patricia Leak
Fund for Nursing Research. Nipples were
donated by North Carolina Children’s Hospital,
Duke University Medical Center, Biobehavioral
Laboratory at UNC-Chapel Hill, Boston Children’s
Hospital, Floating Hospital for Children at
Tufts University Medical Center, University of
Oklahoma Children’s Hospital, Royal Children’s
Hospital, Queensland, Australia, Medela, Inc.,
& Handi-Craft Company
THE FEEDING FLOCK
Feeding Interest Group

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