External pacing is most commonly a term associated with temporary and externally applied pacemakers that regulate or initiate the electrical current of the heart thereby initiating a heart contractions in order to cure bradycardia (dangerously slow heart contractions) or asystole (no heart contractions) or even by regulating some tachycardias (dangerously fast heart contractions). This is not the context in which I am using the term. I hope someone with cardiac expertise will expound on this type of external pacing further.

External pacing is also a treatment technique for feeding an infant with a problematic suck, swallow, breath sequence. Smoothly coordinated sucking, swallowing and breathing are all necessary for a safe and efficient infant feeding to occur. Sometimes there are problems in the functioning of one or more of the three, sometimes there are problems in the infant's anatomy, and commonly immaturity plays a role. Sometimes the feeder causes problems because of techniques used.

Premature infants frequently get into trouble with their suck, swallow, breath sequence. In fact, if a premature infant is fed by mouth too early it is predicable that there will be problems. Use of a faster flowing "premie nipple" may get the milk in but it may also cause feeding-induced apnea because of the faster flow. Sometimes even a full term infant with no other discernable problems will also have this problem and this may be a red flag of future developmental problems or may be an isolated finding. Either way, the infant may fail to breathe during prolonged bursts of sucking. Normally infants suck in a burst with some interspersed breathing followed by a period of no sucking and more rapid breathing. If they fail to breath during the sucking burst it is called feeding-induced apnea and it may in turn lead to bradycardia and low oxygen saturation. In mild cases, feeding induced apnea may prevent an infant from having enough energy to take in adequate nutrition orally and in extreme cases it can kill.

In terms of infant feeding, external pacing is the feeder basically stopping the feeding to allow breathing time. If feeding induced apnea is suspected or confirmed, the feeder counts the number of suck/swallows and stops the feeding after 3 - 5 suck/swallows if the infant doesn't spontaneously breath. The nipple may be removed, or the suction may simply be broken (causing less distress in a hungry infant and making it easier return to feeding but not enough of an intervention for some infants who must have the nipple removed to inntiate breathing. In the case of bottle feeding the bottle may sometimes be tilted downward to stop the flow of the milk (with the same precautions expressed above about breaking the suction). Constant, close observation in good light of the infant during feeding is necessary, both to assess the need for continued external pacing and to set the rhythm. Frequent reassessment of the need for external pacing should be done throughout the feeding as well as over time. The infant (if not showing any signs of distress, such as bradycardia, low oxygen saturation or color changes) may be allowed 5 or 6 sucks to see if s/he will breath spontaneously. Often external pacing is only needed during part of a feeding; during a mother's let down while the milk flow is most rapid (and which may occur multiple times during a single feeding) or at the start of a bottle feeding session. Sometimes the premature infant is just too young and oral feeding should be delayed another week or 2 to allow for maturation. Typically the premature infant is ready to begin oral feeding between 32 and 35 weeks post conception. Most premature infants can safely breastfeed about 2 weeks before they can safely bottle feed. 32 to 35 weeks is a wide window and like most developmental milestones varies with individuals. Infants go through a learning period where they can safely but not yet efficiently feed and so are often also given some tube feedings (gavage feedings).

It should also be noted that a baby with a normal suck, swallow, breath sequence takes frequent (albeit shallow) breaths throughout the sucking burst and so may and probably will tolerate much longer bursts of suckles than an infant with feeding induced apnea. Long bursts of suckles alone does not diagnose feeding-induced apnea. Rather, it is the clinical signs seen in the infant during feeding (oxygen desaturation, color changes, bradycardia) sometimes seen with long bursts of suckles but sometimes even seen with short bursts that show us there is a problem. Further diagnostic certainty of feeding-induced apnea as well as other possible functional or anatomical problems can be had with tests such as a multichannel pneumogram, polysomnogram, GER work-up or videofluoroscopy.

Most infants typically outgrow the problem of simple maturity related feeding-induced apnea and can eventually pace themselves appropriately throughout the feeding to allow breathing as well as sucking and swallowing. Until then, external pacing is an extremely effective and low tech method to improve the safety and the efficiency of oral feeding.

Sources: Feeding and Swallowing Disorders in Infancy Assessment and Management is my main text book source. I also rely on my memory of a 2 day workshop with the authors where breastfeeding was more integrated than in the textbook. The reference to safely breastfeeding before safely bottle feeding is from research by Paula Meier.

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