Long-term oral sensitivity and feeding skills of low-risk pre-term infants

https://doi.org/10.1016/j.earlhumdev.2003.10.001Get rights and content

Abstract

This study examined the oral sensitivity and feeding skills of low-risk pre-term infants at 11–17 months corrected age. Twenty pre-term infants (PT) born between 32 and 37 weeks at birth without any medical comorbidities were assessed. All of this PT group received supplemental nasogastric (NG) tube feeds during their birth-stay in hospital. A matched control group of 10 healthy full-term infants (FT) was also assessed. Oral sensitivity and feeding skills were assessed during a typical mealtime using the Royal Children's Hospital Oral Sensitivity Checklist (OSC) and the Pre-Speech Assessment Scale (PSAS). Results demonstrated that, at 11–17 months corrected age, the PT group displayed significantly more behaviours suggestive of altered oral sensitivity and facial defensiveness, and a trend of more delayed feeding development than the FT group. Further, results demonstrated that, relative to the FT group, pre-term infants who received greater than 3 weeks of NG feeding (PT>3NG) displayed significantly more facial defensive behaviour, and displayed significant delays across more aspects of their feeding development than pre-term infants who received less than 2 weeks of NG feeding (PT<2NG). The information from this preliminary study suggests that low-risk pre-term infants, particularly those who receive supplemental NG feeding for greater than 3 weeks, may be at risk for displaying long-term altered oral sensitivity and facial defensiveness, as well as feeding delays. These observations warrant further investigation on this topic.

Introduction

To date, there has been little information in the literature regarding the long-term feeding and oral sensitivity skills of pre-term (PT) infants. Of the literature that is available regarding this issue, most has focused on the outcomes of high-risk pre-term infants, aged less than 32 weeks gestational age and/or presenting with severe medical comorbidities affecting the oral, pharyngeal, cardiac, respiratory, gastrointestinal, or neurological systems. Many of these infants present with dysphagia and may be at risk of aspiration, thus requiring long periods of non-oral feeding until they mature sufficiently and their primary medical conditions improve enough to allow oral feeding to be attempted [1], [2], [3], [4], [5], [6], [7]. Several studies suggest that this group of high-risk pre-term infants often display long-term feeding difficulties beyond the neonatal period [7], [8], [9]. However, very little literature has focused on the feeding and oral sensitivity outcomes of lower-risk pre-term infants, who are born relatively more mature and present without medical sequelae.

Pre-term infants who are born after 32 weeks gestational age without any severe medical comorbidities generally do not present with dysphagia, and are usually able to commence oral feeds soon after birth [1], [2], [3], [4], [5]. However, most of this group display difficulty meeting their full nutritional and caloric needs through oral feeding alone in the weeks prior to their term date [1], [2], [3], [4], [5]. It is suggested that this difficulty is largely due to their poor nutritional and energy reserves, as well as immaturity of the neurological and muscular systems, which results in low endurance levels for feeding [1], [2], [3], [4], [5], [10]. Consequently, the majority of low-risk pre-term infants generally require at least some degree of short-term artificial dietary supplementation to augment oral feeds. This is usually accomplished through supplemental tube-feeding [1], [2], [3], [4], [5], [10], [11], [12], [13], [14].

Nasogastric (NG) feeding is the most commonly used form of tube-feeding [15]. Nasogastric feeding has an advantage over many other forms of tube-feeding, in that no anaesthesia or surgery is required for the insertion of the feeding tube, and in that the tube does not obstruct the oral cavity. For this reason, NG feeding is often the initial method of tube-feeding used with pre-term infants who display either dysphagia or difficulty meeting their full dietary needs orally [1], [2], [3], [6], [7], [10], [13], [14], [16]. However, despite the widespread use of this form of tube-feeding, it remains uncertain whether exposure to NG feeding in infants may impact on later oral sensitivity and feeding. While it has been reported that the immediate side-effects of NG feeding can include the presence of pharyngeal irritation and discomfort, as well as irritation of the mucosa of the oesophagus and stomach [6], [7], [10], [15], [16], limited information is available regarding the long-term outcomes for infants who receive NG feeding, in terms of oral sensitivity and feeding development. The information that is currently available regarding this issue is almost entirely based on anecdotal evidence, such as the subjective clinical observations of authors, and is confounded by the comorbidities of the infants studied.

There have been many anecdotal reports in the literature that suggest that exposure to NG feeding in infants may affect oral sensitivity [1], [2], [3], [6], [7], [10], [12], [16]. Specifically, it has been suggested that the adverse stimulation caused by NG feeding may contribute to some children becoming hypersensitive to some forms of oral stimulation, leading to discomfort and rejection of new sensory stimuli [1], [2], [3], [6], [10], [12], [16]. It has also been suggested that, over time, the continued presence of adverse stimulation from the NG tube may actually contribute to some children becoming desensitised/hyposensitive to stimulation in the oral and pharyngeal regions, possibly leading to delayed triggering of the swallow mechanism and aspiration [1], [2], [3], [6], [12]. However, as little systematic research has been undertaken in this area, it remains unclear what proportion of low-risk pre-term infants who have been exposed to NG feeding are affected by either of these conditions.

It has been reported that oral sensitivity issues, particularly hypersensitivity, may develop into a conditioned facial defensiveness [1], [2], [3], [6], [7], [12], [17]. Facial defensiveness is reported to result from a behavioural conditioning process that is likely to occur if physical or emotional trauma, as may be caused by the process of insertion and presence of a NG tube, occurs to the feeding mechanism during the early stages of central nervous system development [3], [6], [7], [12]. It is suggested that children learn to relate this discomfort with the feeding process, thus developing a conditioned avoidance of food and other oral and facial stimulation, which may persist beyond the existence of the original source of the trauma [3], [7], [12], [17]. Behaviour reported to be associated with facial defensiveness includes the use of avoidance tactics in anticipation of approaching food or contact with the face, such as crying, biting, head turning, gagging, and pushing food away [1], [2], [3], [6], [7], [12]. However, despite widespread anecdotal reports of the existence of conditioned facial defensiveness in infants who have received NG feeding, there remains no specific data to report the incidence of this behavioural response in the low-risk pre-term population, or any data regarding the duration over which this defensive behaviour persists following the removal of the feeding tube.

There are many anecdotal reports in the literature that suggest that the use of NG feeding in infants may impact on later feeding skill development [1], [2], [3], [4], [5], [6], [7], [12], [16], [17]. These reports suggest that children who have a history of tube-feeding may go on to display delayed oral motor development across a range of specific feeding skills, including sucking, swallowing, biting and chewing [1], [2], [3], [4], [5], [6], [7], [12], [16], [17]. However, few reports are available that adjust for the confounding effect of pre-existing dysphagia or other medical conditions that may be present in infants who receive NG feeding. As comorbidities of the respiratory, cardiac, digestive, and neurological systems may all affect feeding outcomes [1], [2], [3], [7], [12], it is difficult when studying a population with these conditions to separate the effects of NG feeding from the effects of the primary medical conditions themselves. Therefore, it remains unclear whether NG feeding has the potential to merely exacerbate existing feeding problems/dysphagia, or whether NG feeding has the potential to negatively affect feeding development in previously non-dysphagic individuals, as occurs in low-risk pre-term infants.

In addition, there is a paucity of information available regarding the association between duration of exposure to NG feeding in infants and their feeding and oral sensitivity outcomes. However, considering that it is possible for some children to undergo temporary supplemental NG feeding, while others receive full NG feeding for months and even years, it cannot be assumed that the impact of NG feeding would be of the same degree in these infants.

Given the limitations of the information currently available regarding the long-term oral sensitivity and feeding skills of low-risk pre-term infants, or the association between duration of NG feeding and later oral sensitivity and feeding skills in this population, it is clear that further systematic investigation is needed.

The current descriptive study was designed to assess the oral sensitivity (i.e. sensitivity of the palate, gums, tongue, lips, and face in relation to touch, taste, and texture) and feeding development (e.g. sucking, chewing, biting, and swallowing) of pre-term infants born after 32 weeks gestational age, who had no comorbidities that may affect feeding outcomes. Infants were assessed at 11–17 months corrected age to allow an assessment of long-term oral sensitivity and feeding outcomes.

Two specific aims were investigated: (a) to ascertain any significant differences between the oral sensitivity and feeding development of pre-term and full-term (FT) infants with no medical conditions at the same corrected age, and (b) to examine any significant differences between the oral sensitivity and feeding development of pre-term infants who received shorter durations of NG feeding and those who received longer durations of NG feeding.

Section snippets

Participants

Two main groups of infants were recruited for the study: low-risk pre-term infants and a matched control group of full-term infants. Exclusion criteria for both groups included any history of structural lesions to the swallowing mechanism, as well as any history of respiratory, cardiac, gastro-intestinal, or neurological conditions. In this way, only infants void of any known medical conditions that may affect feeding were included.

Candidates for the PT group were recruited from a database of

Comparison of FT and PT groups

Comparison across the two subtests of the OSC revealed statistically significant differences between the FT and PT groups in both subtests (see Table 2). Specifically, the PT group displayed significantly more behaviours suggestive of altered oral sensitivity than the FT group (p=0.000), with all of the infants in the PT group displaying some behaviours suggestive of altered oral sensitivity. Of them, 1 infant displayed hyposensitive behaviours, while the remaining 19 displayed hypersensitive

Discussion

Although the results of the present study are based on small numbers of participants, they provide important preliminary data. Specifically, results demonstrate that, relative to full-term controls, low-risk pre-term infants were found to display continued altered oral sensitivity, facial defensiveness, and delayed feeding development at 11–17 months corrected age. The results also demonstrate that low-risk pre-term infants who received greater than 3 weeks of NG feeding displayed more facial

Conclusion

To date, there has been limited systematic evidence regarding the long-term oral sensitivity and feeding skills of low-risk pre-term infants, born between 32 and 37 weeks gestational age with no medical comorbidities. This study, however, suggests that this population may be at risk of altered oral sensitivity, facial defensiveness, and delayed feeding development until at least 11–17 months corrected age. The feeding outcomes that low-risk pre-term infants appear to be at greatest risk of

Acknowledgments

Thanks must be given to the Neonatal Department of the Royal Women's Hospital (Brisbane) and to the Speech Pathology Department at Royal Children's Hospital (Brisbane) for their support of this study. In addition, thanks must also be given to the parents of all the participants for allowing their children to be involved in the study.

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