Effects of a Valved Feeding System in Late-preterm Newborns: the Safe Oral Feeding Trial

The swallowing patterns are still immature in the newborn, especially if preterm. An incomplete synchronization in the process of sucking, swallowing and breathing could lead to some difficulty during feedings with desaturations and risk of milk inhalation in the upper airway tract. Moreover, a dysfunctional or immature pattern of sucking, swallowing and breathing also affect the post-prandial period, tiring the newborn and increasing the cardio-respiratory instability.

Breastfeeding promote the development of a physiological coordination of the process of sucking, swallowing and breathing, guaranteeing high and stable values of oxygenation during feedings. On the other hand, bottle-feeding could be responsible of a difficult coordination among the phases of swallowing and breathing. In an healthy, at term, brestfed newborn is observed a typical pattern of sucking-swallowing-expiration with a ratio of 1:1:1. In a bottlefed newborn this ratio is 2-12:1:4, with a relative increase of the period of sucking compared to the swallowing one, that could lead to apnoeas and desaturations.

The differences between the two feedings modality are more accentuated in the late-preterm newborn, which is more prone to cardio-respiratory instability compared to the healthy at term newborn, because of the immaturity of the respiratory centers in the brainstem, and of the processes responsible for the coordination of the sucking, swallowing and breathing .

However breastfeeding, in spite of the fact that is crucial for the development of the correct process of sucking, can be challenging in the premature infant because it requires a considerable physical effort.

Therefore, disposing of devices for nutrition able to facilitate oral feeding, simulating the physiologic breastfeeding, is necessary. In this way, we can contribute to the development of the proper sucking-swallowing-breathing pattern and to improve cardio-respiratory stability.

In literature there are multiple studies carried out on term newborns demonstrating the importance of the negative pressure or air vacuum created in the oral cavity, in order to promote the emptying of the lactiferous ducts and/or of the teat and simultaneously promote the maintainance of the right respiratory pattern. An ergonomic feeding system with a valve able to create vacuum could be able to respond to the demands of late preterm newborns.

Aim of the study is to evaluate the effects of a trial with an experimental feeding system with a teat with a valve able to facilitate the vacuum in the oral cavity on the pattern of sucking-swallowing and breathing in late preterm newborns.

NUMBER OF PATIENTS Precise data regarding swallowing/respiration rate in bottle-fed late preterm infants in the first 3 days of life are lacking in the literature. Considering a mean swallow/respiration ratio of 1.5 and a variance of 0.5, obtained from surveys performed at our center prior to the study, a sample size of 38 infants per arm was estimated to achieve 80% power to detect a 30% difference on the primary outcome with a significance level of 0.05.

STUDY DESIGN Late preterm newborns eligible to enter in the study, prior obtaining the informed consent from parents, will be assigned in the "B-ESP" or "B-STD" group through a process of block randomisation, controlled by a software.

Newborns included in the randomisation, after a training of 3 meals with the feeding bottle assigned from the randomisation, can be entered in the study.

Newborns included in the study will be monitored for the entire duration of a meal and the subsequent 3-hours period. This monitoring will be collected in two different times (T1 and T2): in the second day of life (24-48 hours of life) and in the fourth day of life (72-96 hours of life). The study includes an audio recording of the swallowings through a microphone in the room and the recordings of the process of sucking and swallowing through a cutaneous sensor.

In addition, a cardiorespiratory monitoring with a poligraph will be made, considering oxygen saturation, cardiac and respiratory frequency and electrocardiography. The meal's video recording will permit a subsequent classification of the sucking movements and the evaluation of any possible interference in the polygraphic recording.

FEEDING DEVICES

Newborns of the B-STD group will be fed using a classic disposable feeding device, which is actually in use in our centre and provided by our hospital, composed of:

• a 150 mL feeding bottle in polypropylene, devoid of BPA;
• a silicon teat, devoid of BPA, available in two types, (a slow graduated flow and a standard flow) depending on the necessities and suction abilities of the baby;
• a protective plug.

Newborns of the B-ESP group will be fed using a feeding system with a valved ergonomic teat, composed of:

• a slow-flow ergonomic silicon teat
• polipropilene bottle with a capacity of 150 mL, with a ventilation valve on the bottom
• silicon valve

Newborns will be fed with defined quantities of maternal milk or bank donated milk, based on weight and gestational age.

The meal will be administered by the caregiver (a parent or a nurse) previously trained. The meal's administration will be performed keeping the baby in the caregivers's arms in the ESL position (semielevated side-lying). At the end of the feeding process the newborn will be repositioned in his cradle in the supine position.

The cardiosaturimetric evaluation will be performed using a system of polygraphic monitoring, which allows a simultaneous non-invasive recording of cardiorespiratory parameters, noises and movements associated to the sucking and swallowing processes combined to video recordings.

The evaluation of the sucking process will be carried out using a structured questionnaire composed by 31 items, which allows to distinguish normal suction (mature) from disorganized and dysfunctional ones.

Considering simultaneously the cardiosaturimetric parameters, video, audio and cutaneous sensor's recordings, it is possible to obtain a more accurate evaluation of the processes of swallowing, sucking and breathing of the newborn during meal administration. It is also possible to identify the exact moment of the breathing process assigned to the newborn's swallowing.

CLINICAL DATA

At birth:

• gestational age;
• weight in grams;
• z-score;
• sex;
• type of delivery;
• peri-partum condition, including possible administration of prenatal corticosteroids;
• type of support provided at birth;

At T1 and T2:

• hours from birth;
• weight;
• z-score;
• number of meals in a day;
• type of milk administered;
• overall volume administered expressed in mL in a day;
• duration of a meal expressed in minutes;
• number of regurgitation or vomit during the administration of a meal;
• number of regurgitation or vomit after the admninistration of a meal;

At discharge:

• weight;
• z-score;
• number of meals in a day;
• type of feeding (exclusive breastfeeding; exckusive bottlefeeding or mixed)
• overall volume administered expressed in mL in a day;

INSTRUMENTAL DATA

• Number of suctions;
• Number of swallowings;
• Number of apnoeas;
• Average duration of apnoeas;
• Number of oxygen desaturations
• Minimal oxygen saturation;
• Number of reduction of cardiac frequency (bradycardia);
• Minimal cardiac frequency. The definition of apnoea, oxygen desaturation and bradycardia applied in this study are the ones defined by literature (Di Fiore JM, Arko MK, Miller MJ, et al. Cardiorespiratory Events in Preterm Infants Referred for Apnea Monitoring Studies. PEDIATRICS. 2001;108(6):1304-1308.)
• APNOEA: arrest of the breathing acts for a period of at least 20 seconds or arrest of the breathing acts for a period of at least 5 seconds associated with bradycardia and/or desaturations;
• OXYGEN DESATURATIONS: reduction of the oxygen saturation (SpO2) <80% or of at least 5% compared to the baseline, for at least 4 seconds.
• BRADYCARDIA: reduction of the cardiac frequency under 80 bpm for at least 4 seconds

STATISTICAL ANALYSIS

Statistical analysis will be carried out using the STATISTICA software package for Windows (StatSoft, Inc., Tulsa, Oklahoma, USA). Every newborn in the experimental group will be matched with a newborn of the control group similar for gestational age and weight. For the normal distribution, data will be tested with the Kolmogorov-Smirnov test and with the exploratory data analysis. Data will be expressed as statistical mean and standard deviation (SD) or as median and interquantile range depending on the relative distribution. The differences between the polisonnographic data will be evaluated with the Student's T test or through a similar non-parametric test depending on the distribution: Fisher test for comparison between categorical data and regression tests (linear and non-linear) for comparison between continuous variables. Statistical significance is set as p<0.05.

EXPECTED RESULTS

The more physiological administration of milk with a feeding system with a valved ergonomic teat, could better promote the development of coordination in the process of sucking-swallowing-breathing. Therefore inhalation and cardiosaturimetric events during a meal and immediately after will be reduced and therefore the newborn's oral feeding tolerance will increase, making it more similar to physiological breastfeeding.

Bottle-feeding milk administration with a feeding system with a valved ergonomic teat in the first days of life, the period when exclusive breastfeeding is more difficult, could also promote the transition between bottle-feeding to breastfeeding, because this mechanism is more similar to the physiological one.

If the results of this study will support this hypotesis, feeding system with a valved ergonomic teat could be chosen as a non-pharmacological treatment for late-preterm newborns who encounter difficulty in the oral feeding, such as cardio-respiratory instability during the sucking process and risk of milk inhalation when the breastfeeding is not possible.