Hi Jessica,
The origional pumps invented by Einer Egnell (which evolved into the
Ameda and Medela heavier, hospital grade pumps) were based on research
into what the optimum suction pressures were for milk expression, what
the maximum time the human nipple could be subjected to negative
pressure, and what pattern of suction pressure/release worked best
within the bounds of what is mechanically possible.  Egnell's genious
has stood the test of time, especially since there are no pumps that
have been proven to express more milk per unit time than the heavy,
hospital grade ones he developed (Ameda Lact-e and SMB, Medela
Classic).  New developments in the pump world have focused on making
pumps cheaper (and this almost always involves compromise in the number
of cycles per minute, or the peak suction pressure, or the amount of
time the nipple is exposed to the peak suction) and making pumps more
comfortable or acceptable to women (Medela Symphony, Whittlestone).
Medela went with the researcher's second most efficient expression
pattern in order to increase the comfort and  acceptability of the
Symphony pump.

The Medela Mini-electric pump cycles fewer times per minute than larger
pumps.  It also exposes the nipple to peak suction for longer periods of
time (as do all small electric or battery pumps, since they need to
evacuate air for up to several seconds to build enough vacuum to expell
milk, because of the small size of their motors and pistons).  Together,
this means that the mother will get less milk per minute pumped, and
increases the risk that her nipples will get damaged from pumping,
particularly if she overuses the pump.  This is why this pump is rated
for casual, a few times a week, use.  It is very, very difficult for
women to maintain a milk supply with small machines that are not meant
for that purpose, especially in light of research showing how fast milk
supplies increase during the first 2 weeks postpartum, and that they
need to in order to ensure a long term milk supply.  I think that this
is more important than risk of infection from these single user pumps,
but infection is always a concern.  Before the new kits for hospital
grade pumps that contain filters (Medela) or closed system diaphragms
(Ameda), there were numerous infections traced back to breastpumps in
hospital nicu's.

The Pump in Style does not have a filter at all, and it is common for
the inside of the pump unit itself to get moldy or crusty.  The Purely
Yours (Ameda's personal double pump) has a closed system kit, but a
lower peak suction than the lact-e or elite.  The Purely Yours could be
shared safely (by mothers each using their own kit) from an infection
standpoint, but the small motor is not meant for heavy use (same is true
of the Pump in Style) and it will burn out if overused.

I've seen huge differences in the amount of milk per unit time that moms
are able to pump with the larger hospital grade pumps vs the Pump in
Style and Purely Yours (and even larger differences with smaller
pumps).  When a mother has a preterm infant, or an infant that is not
stimulating the milk supply for any reason, I recommend the heaviest
hospital grade pumps, beased on my clinical experiences tracking
outcomes for the different pumps over the years.  I understand that in
some nations that are not as rich as the US, these pumps may not be
economically viable, but in that case we have proven effectiveness of
manual expression when mothers are properly instructed and supported.

Finally, for trials of small pumps, the mother can be allowed to try the
rental grade pump on minimum to medium suction.  If she gets optimal
results on low suction, she will succeed with the Purely Yours or Pump
in Style.  If she needs medium or higher suction on the hospital grade
pumps,, she will get less milk than she needs to from the smaller pumps
to maintain a supply.

--
Catherine Watson Genna, IBCLC  New York City  mailto:[log in to unmask]

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