A continuum of states of consciousness, ranging from deep sleep though awake states to crying has been described. The optimal state for feeding is an awake, alert, or active state, although some infants can feed adequately in a drowsy state. State control difficulties may be components of a variety of medical conditions. Assessment of state should be a routine part of feeding assessment and should include the following
- Note infant’s state before, during, and after feeds.
- If at any point the infant is not in an appropriate state, note if infant can be brought into an appropriate state.
- Note what techniques are successful and how much assistance the infant needs to maintain appropriate state for feeding.
The feeding process places many demands on the infant. These demands may be internal, such as increased respiratory and digestive functions, or external, such as oral-tactile experiences during feeding or variations in ambient temperature, noise, or light. If these demands are beyond the infant’s adaptable capacities, the infant may respond with behaviors that reflect stress. If stress cues are noted before, during, or after a feeding, the source of the stress needs to be identified and modified. Examples of potential sources of stress:
- Environmental: bright lights, noise, TV, distracting movements of siblings or others
- Feeding related: liquid flowing too fast or slow, distracting movements of feeder
- Internal discomfort: gastroesophageal reflux, desaturation, increased work of breathing
Infant Stress Cues
State and Attentional
Major Stress (when seen with feeding)
Oral Reflexes: Oral reflexes can be either adaptive (assist the infant in locating and obtaining food, e.g.: rooting reflex and sucking reflex) or protective (keep airway free of foreign material or expel it as it enters the airway, e.g.: cough and gag). Expression of reflexes such as rooting and sucking can change depending on infant’s level of hunger or state of alertness and assessment should take this into account.
Assessment of cough during feeding is especially important in preterm infants. If cough occurs during sucking and swallowing it may indicate material crossing near or entering the airway as it descends through the pharynx. If coughing is observed during sucking pauses, or after feeding, it may indicate material ascending into the pharynx from gastroesophageal reflux.
Behavioral Responses to Tactile Input: During feeding the infant accommodates to a wide variety of tactile stimuli within the mouth as well as external stimuli from the touch of the feeder’s hands on the infant’s face or the touch-pressure of being held. The infant must perceive the tactile input appropriately to produce the appropriate motoric responses for feeding.
Preterm infants may perceive tactile input as stressful and may respond with a variety of stress reactions as described above. Early NICU experiences may have included negative and aversive stimuli to the oral-facial area. The infant may have been unable to engage in normal, pleasurable, oral exploration because of motoric immaturity or delay, intubation, or lack of experience. A pattern of learned negative or aversive behaviors that persists beyond discharge may develop.
Referral to a feeding therapist for a structured evaluation of tactile responses may be indicated for clear delineation of the threshold beyond which the infant has an inappropriate behavioral response to tactile input.
An optimal position for young infants is characterized by orientation around midline, neutral anterior-posterior alignment of the head and neck, neutral alignment or slight flexion of the trunk, and flexed hips and knees.
When the feeding position is not satisfactory, the underlying factors affecting the position should be identified to develop appropriate positioning techniques. A frequent example is the preterm infant who extends, becomes hypertonic during feeding, and is difficult to hold in the optimal feeding position. This infant may be using neck extension to maintain a patent airway, may be showing a stress reaction to the tactile or gustatory aspects of feeding, or may have abnormalities of the central nervous system.
Assessment of specific function of oral structures is most effective if the infant sucks on the examiner’s gloved finger. A wide variety of oral motor difficulties may be observed in LBW infants. Many problems are due to a lack of positional stability. Full-term infants are born with a substantial amount of subcutaneous fat and well defined fat pads in the checks. The tongue fills the oral cavity and is in physical contact with all the surfaces of the oral cavity. Additionally, at birth, the term infant has a strong physiological flexor tone that, combined with the exoskeleton, provides a stable base for the oral structure. In contrast, the premature infant has less muscle bulk and poorly developed tendons and ligament structures as well as less body fat. There is decreased opposition of the tongue to the surfaces of the oral cavity and reduced flexor tone through the head and neck with neck hyperextension. Lack of positional stability may lead to abnormal oral motor patterns, some of which may continue post discharge.
Examples of more common oral motor difficulties:
- Tongue-tip elevation: the tip of the tongue is held firmly against the hard palate behind the upper alveolar ridge, potentially interfering with nipple insertion.
- Tongue retraction: The tongue sits back in the mouth, well behind the alveolar ridges causing poor contact between the tongue and the nipple to stimulate appropriate tongue movements. Strong neck hyperextension can contribute to tongue retraction by pulling the tongue back into the mouth.
- Tongue protrusion: The tongue pushes outward instead of moving in the normal wavelike anterior-posterior pattern. The tongue may compress the nipple, with little suction generated, leading to inefficient sucking. This pattern may be seen in infants who have sucked on endotracheal tubes and those with low tone.
- Excessive Jaw Excursion: The jaw moves in a greater range than expected and the movement is poorly graded. Tongue contact on the nipple may be poor, diminishing both compression and suction. Lip seal can also be compromised, further impairing sucking.
The infant will have physiologic responses to the work of feeding. If an infant is not able to cope with these responses physiological changes, stress reactions, and poor endurance may result. To assess physiologic control during feeding each parameter is evaluated at baseline, during feeding, and after feeding.
Heart Rate: In term infants heart rate is typically in the range of 120 to 140 beats per minute. It is not uncommon for see heart rate increases of about 10 beats per minute during feeding. Larger increases may indicate that feeding is placing excessive demands on the infant. Bradycardia (a drop in heart rate to below 100 beats per minute) can also be observed during feeding in the high-risk infant, and is a potentially life threatening event. Bradycardia might occur after oxygen desaturation, or with a suspected reflux event, or with position change. In some cases it is a vagally mediated response to stimulation of sensory receptors in the pharyngeal-laryngeal area. Bradycardia may be triggered via stretch receptors within the pharynx that may be stimulated by a large bolus. Touch-pressure receptors can be stimulated by the presence of nasogastric tubes, or chemoreceptors can be stimulated by microaspiration of food or by reflux of gastric content. Decreases in oxygen saturation can also lead to bradycardia.
Respiratory Rate: The most accurate method of measuring respiratory rate (RR) is counting the infant’s breaths. Normal values for term infants are 30 to 60 breaths per minute. During bottle feeding the respiratory rate is low while the infant is actively sucking. It is higher during pauses. This leads to an overall RR that is adequate for effective ventilation. During the early part of feeding, when the infant is sucking eagerly, the respiratory rate decreases significantly from baseline values. As the feeding progresses and the infant sucks less eagerly, taking more pauses to breathe, the respiratory rate increases toward baseline.
In infants with respiratory compromise RR can be significantly elevated. Infants who require a high respiratory rate to maintain homeostasis may not be able to tolerate the suppression in respiration that occurs in the early part of feeding. The infant may fatigue easily or may be at risk for aspiration as he or she tries to gasp for air. Respiratory rate during feeding is measured during pauses in sucking. IF RR is above 80 breaths per minute during these pauses, it often indicates that work of feeding is too great for the infant.
Studies indicate that term and preterm infants experience light, but measurable oxygen desaturation with feeding. For the compromised infant with borderline saturations, such reduction may be significant. If desaturation is observed during feeding evaluation, the pattern of desaturation should be noted. Sudden dips may be associated with apnea or bradycardic episodes, whereas a gradual decline may indicate inadequate respiratory support for feeding.
During feeding assessment without oxymetry, attention should be focused on the infant’s color around the mouth and eyes. If cyanosis is noted it is recommended that the infant be fed with an oximeter in place. A lack of color change with feeding, however does not necessarily imply that oxygen saturation is normal. Many infants can have relatively low oxygen saturation without external evidence such as cyanosis.
Endurance: Poor endurance may result in the infant terminating the feeding before taking the required volume, or demonstrating poor weight gain despite acceptable intake. Endurance is a reflection of the infant’s work to maintain homeostasis, work for other activity (such as feeding) and the infant’s cardiopulmonary reserve. Endurance is compromised by many disease processes that are more common in LBW infants.
Problems in any one of these processes or lack of coordination among these processes can have a profound effect on the infant’s feeding abilities. Within the pharynx, feeding and breathing share a common space. This dual role of the pharynx underlies the difficulties observed when sucking, swallowing, and breathing are not well coordinated.
Sucking: Sucking involves the rhythmic movements of the tongue and jaw, with support from the lips and cheeks, which create changes in pressure that cause liquid to flow out of a nipple. Sucking is comprised of two types of pressure, positive pressure (compression) and negative pressure (suction). Non-nutritive sucking occurs in a highly organized, repetitive pattern of bursts and pauses with a high ratio of sucks per swallow (6 to 8: 1) and 1 to 4 swallows per burst. Assessment of non-nutritive sucking on a gloved finger allows evaluation of the strength of the suck and relative amounts of suction and compression.
Nutritive sucking occurs during active feeding and has a more complex pattern than non-nutritive sucking. Preterm infants often have fewer or shorter bursts of nutritive sucking. At the beginning of a feeding the sucking pattern usually consists of long sucking outbursts with few or brief sucking pauses. The suck-swallow ratio is usually 1:1, but may increase toward the end of a feeding. In assessment of sucking in bottle-fed infants, return of bubbles into the bottle is a reflection of liquid flow out of the bottle. The strength of the infant’s suck is reflected in both the resistance to pulling the nipple out of the infant’s mouth and the rate of liquid flow. On the breast, the rate of sucking and the suck-swallow ratio can give indications of the rate of milk flow. The slower the sucking rate and lower the suck-swallow ratio, the faster the milk flow. When differences are noted in the quality of sucking between nutritive and non-nutritive sucking it is suggestive of problems with some aspect of suck-swallow-breath coordination.
Swallowing: Coughing or choking during swallowing can indicate that liquid is impinging on the airway. This can be liquid that is actually aspirated into the airway or that merely penetrates the airway and then is expelled. Aspiration can result from a primary swallowing dysfunction or from lack of coordination between sucking, swallowing, and breathing. Aspiration can be descending (during feeding), but can also be ascending (during gastroesophageal reflux). A history of frequent upper respiratory infection or pneumonia may be an indication that “silent” aspiration is taking place.
Clinical assessment of swallowing function includes: ability to handle secretions, presence of noise or wet sounding breathing during or after feeding. (Noises arising from the nasopharynx may indicate nasal reflux during swallowing, while noises in the pharynx may indicate residue left in the pharynx after the swallow), and the need for multiple swallows to clear a single bolus.
Infants who show signs of swallowing dysfunction should be referred for further assessment. The most comprehensive evaluation of swallowing occurs radiologically during the videofluoroscopic swallowing study (VFSS) or modified barium swallow.
Breathing: Infants with compromised respiratory function may be unable to make sufficient adjustment to accommodate the work of feeding. Assessment should include:
- Respiratory effort: evaluation before, during, and after feeding. Increased respiratory effort is indicated by retractions at the neck, trunk, or rib cage, head bobbing, grunting or forced exhalation.
- Changes in respiratory pattern: observe whether there are excessive pauses or irregularities in breathing pattern. Short respiratory pause of 15 seconds can be considered normal at any age, but longer periods or those associated with cyanosis, pallor, or bradycardia are pathologic.
- Sounds of respirations. Noise heard during any part of the respiratory cycle may indicate airway obstruction or alteration in airway patency.
Coordination of Sucking, Swallowing, and Breathing: This is assessed by listening to the ratio of sucks to swallows and the timing and adequacy of respiratory efforts during sucking bursts. The normal rhythmic sucking pattern during bottle feeding consists of a series of bursts and pauses that begins as a continuous sucking pattern and changes to an intermittent sucking pattern over the course of the feeding. Normally recovery in all respiratory parameters occurs within the sucking pauses.
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