Response to Preemie Nipple Use with Older Infants?
The unintended consequences of the extended use of preemie flow rate bottle nipples to support breastfeeding
Catherine S. Shaker, MS/CCC-SLP, BCS-S, C/NDT
Neonatal/Pediatric Speech-Language Pathologist
Board Certified Specialist – Swallowing and Swallowing Disorders
After reading the recent post entitled Preemie Nipple Use with Older Infants? The unintended consequences of the extended use of preemie flow rate bottle nipples to support breastfeeding, I felt compelled to respond. Both my clinical experience and the infants I have worked with tell a different story, and the research-base also suggests otherwise.
The original post’s suppositions are worrisome.
A very slow flow nipple the infant must suck harder to pull the milk from the bottle, thereby, strengthening their suck and ensuring bottle feeding is not “easier” than breast.
Use of slow flow nipples for infants who are both breast and bottle-fed is not intended to “strengthen the suck, or ensure bottle-feeding is not easier than the breast.” Breastfeeding is easier because controllable flow rate optimally supports deep and timely breaths. Faster flowing bottle nipples can create “flow rate confusion” with breastfed infants, and that leads to maladaptive sucking to stop/slow the bottle nipple flow (humping the tongue, retracting the tongue, flattening the tongue, using compression-only sucking pattern). These are all adaptive behaviors that breastfed infants will use to “get through” a bottle feeding from a well-intentioned caregiver who provides a rubber nipple whose flow that is faster than the breast flow. These adaptive oral-motor behaviors in response to the after flow can then become learned maladaptations that endure.
Matthew concluded that preterm infants purposefully used significantly lower sucking pressures (changed their suck to compression-only) with high flow bottle nipples, as compared with low flow nipples. This may have been an attempt to manage or “slow” the flow, so they could breathe when necessary.
A study by Eishima described how infants who demonstrated a strong rhythmical suck-swallow-breathe pattern with a regular flow rate nipple changed their sucking pattern to compression-only sucking when the flow was increased. This was hypothesized to be the infant’s purposeful response in attempt to reduce flow, to allow for breathing.
The assumption that a slow flow requires the infant to suck harder, with its obvious adverse effects, has not been proven and is not accurate. The slow flow nipple merely allows less fluid to come out at a time, i.e., a smaller bolus size, so the infant can return to breathing in a timelier fashion.
It is important to note that any nipple ring tightened excessively will create a vacuum that does indeed require “more work”. Just “hand turning” the nipple ring to close it, but not “man turning it,” averts creating a vacuum. This is not nipple-related, it is caregiver related.
Preemie flow rate nipples have been observed to … interfere with self-regulated suck(le)/swallow/breathe sequence. These increase energy expenditure that cause increased fatigue, and in some complex cases, resulting in failure to gain adequate weight or weight loss.
Research indicates that the more controllable flow rate from a premie nipple does not lead to diminished intake. Just the opposite. Paula Meier’s seminal research on flow from the breast versus manmade rubber nipples found that the infant’s ability to control the flow from the breast, i.e. to stop flow by slowing sucking rate and reducing sucking pressure, is what underlies the exquisite physiology of breastfeeding. Supporting breathing, whether at breast or bottle, is the pathway to safe and efficient intake. Indeed, Nyqvist reported that even tiny 29-week PMA infants in Sweden fed small volumes from the breast with physiologic stability. What Meier’s and Nyqvist’ s findings suggest to us is that when the flow is manageable and more controllable, it is ventilatory-sparing and creates opportunities for breathing to occur. When the infant can breathe as needed, physiologic stability is maintained, and this promotes safe and efficient feeding
Research does not support the stated assumption that slow flow nipples cause fatigue, incoordination and weight loss. Lau et al hypothesized that preterm infants would feed more if the flow rate were unrestricted, versus if milk flowed only when the infant was sucking. The study was designed to identify the difference in intake when flow was faster (less controllable) compared to a slower, more manageable “infant-guided” flow rate. Oral feeding performance was documented when milk delivery was “unrestricted”, as routinely administered in nurseries, versus “restricted” when milk flow, which occurred only when the infant was sucking. Proficiency (% volume transferred during first 5 minutes of a feeding/total volume ordered), efficiency (volume transferred per unit time) and overall transfer (% volume transferred) were calculated. Restricted flow rate (i.e., milk flow only with active sucking, such a as a slow flow nipple) enhanced all three parameters. With a slower flow rate, infants were less likely to have to struggle with milk flow when they need to pause to breathe. This is what Goldfield postulates is essential to coordinating swallowing with breathing. The infant’s ability to feed greater volume with a slower flow rate reflects how a manageable flow rate enhances intake. The slow flow promotes the essential respiratory reserves to “go the distance” like marathon runners, as it allows for frequent and deep breaths.
Research shows that flow rate is negatively correlated with feeding efficiency, meaning the faster the flow, the less the intake. Using a randomized controlled trial, Chang and colleagues evaluated the effects of a crosscut nipple (faster flow rate) versus a single-hole nipple (slower flow rate) on feeding. While feeding thin liquids with a crosscut is ill-advised, the cross-cut was studied in comparison to a comparatively slower flowing nipple. Infants were more physiologically stable and used a more efficient sucking pattern with the slower flowing nipple than with the crosscut nipple.
Research by Pados and colleagues looked at effects of milk flow on the physiologic and behavioral responses to feeding in infants with Hypoplastic Left Heart Syndrome. They remind us that feeding is a physiologically stressful event due to the need to coordinate suck-swallow-breathe and maintain adequate oxygenation during the aerobic demands of feeding. During frequent swallows, there is a repeated and prolonged disruption in ventilation during the time the airway is closed for swallowing. A slower flow rate may assist the infant with both maintaining baseline respiratory reserves, as well as the support the timing of the dynamic airway adjustments (opening and closing) that surround the actual swallow. In their study, Pados et al observed physiologic and behavioral responses to a standard flow (Dr. Brown’s level 2) and a slow flow nipple (Dr. Brown’s preemie). Results included the finding that the slower flow allowed the infant to maintain heart rate closest to baseline, and indeed a lower heart rate overall compared to the standard flow rate, suggesting the slow flow feeding was less physiologically stressful, and the infants fed more volume.
Slow flow nipples clearly can be helpful. Because flow rate should be as seamless as possible when infants go from breast to bottle, we always need to look at the bigger picture, and thoughtfully peel apart what is going on and do so in the context of the evidence-base we currently have. This includes our professional wisdom of course, but also the research studies that have helped to change volume-driven practice even with otherwise healthy infants.
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