This study is a PhD dissertation. In this study, the investigators aim to investigate the effects of three different positions after feeding on gastric residual volume, abdominal oxygenation using near infrared spectroscopy (NIRS), and fractional oxygen extraction values in preterm newborns.

The Design of Research

This study was planned in a randomized crossover study design to evaluate the effects of three different positions on gastric residual volume, fractional oxygen extraction and abdominal oxygenation in clinically stable breastfed preterm newborns. The order of the 3 positions that will be given to the participants the research group will be determined by drawing lots and 3 intervention groups will be formed. The participants in each intervention group will be followed for two hours after feeding in all three positions: semi-elevated supine position, prone position, and right lateral position. Positions will be given to the participants, taking into account the order of positions in each group. All positions will be applied once to each participant. Groups and position rankings according to the result of the draw:

1. st group: Prone, right lateral, and semi-elevated supine position;
2. nd group: Semi-elevated supine, prone, and right lateral position;
3. rd group: Right lateral, semi-elevated supine, and prone position;

48 participants in the study group will be randomly assigned to these 3 intervention groups. In order to determine which participant will be in which group, the numbers from 1 to 48 were distributed to 3 groups through a program in the computer environment without repeating the number (https://www.randomizer.org/). Randomization is provided as follows.

Intervention group 1: 2.8,12,17,18,22,24,25,26,31,33,36,37,40,42,45; Intervention group 2: 1,3,5,10,14,16,19,20,27,28,29,30,32,34,43,44; Intervention group 3: 4,6,7,9,11,13,15,21,23,35,38,39,41,46,47,48;

Location and Time of Research Data of the research Istanbul Kartal Dr. Lütfi Kırdar City Hospital will meet at the Newborn Intensive Care Unit between July 2023 and July 2024. 2., 3., and the university hospital, which provides 4A level intensive care, consists of a total of 41 beds. It consists of 14 level beds, 3rd level 14 beds and 13 beds with 4A level.

Survey's Universe and Sampling After the necessary legal permits have been obtained in the universe of the research, (Ethical Board approval and institution permit ), Kartal Dr. at the time of the investigation. The preterm followed by the Lütfi Kırdar City Hospital Newborn Intensive Care Unit will create newborns.

The sample of the research is Eagle Dr. Lütfi Kırdar City Hospital will create 48 preterm newborns with 28-33 gestation weeks, which are hospitalized between March 2023 and March 2024, which meet the inclusion criteria and received written consent from their parents. Intake swallowing coordination but 32-34. Since it develops after the gestation week, (Törüner ve Büyükgönenç, 2012) sampling will be included in preterm newborns smaller than the 34th gestation week.

Power analysis was performed using the G*Power (v3.1.9.2) program to determine the number of samples. The strength of the study is 1-β (β = II. The probability of type error is expressed as ) and in general research should have 80% power. S. S. Based on the study of Ceylan et al, the effect size of the calculation result made based on the difference of Gastric residuals (ml) measurements according to the supine and right lateral position was calculated as d=0.420 and at the level of α=0.05 %It has been calculated that there must be at least 47 preterm newborns in total to get 80 powers. Considering the loss of case, the number of samples was determined as 48.

Inclusion criteria; The participants who are in the 28-33 gestation week according to the mother's last men's history, are the 1st enteral feeding after mechanical ventilation, fed with breast milk, clinically stable and enteral nutrition, Newborns provided with at least 50% ' of enteral nutrition, fed with free flow and orogastric probe, and received informed consent from parents will be included in the study.

Exclusion criteria; With cerebrovascular disease, with a need for mechanical ventilation, diagnosed with NEC, vomiting, abdominal distension, nasal mechanical obstruction, congenital anomaly, gastrochysis or congenital diaphragm hernia, Newborns with apnea episodes, severe neurological disease will not be included in the study. The participants that worsen clinically after being included in the sample group will be removed from the study.

Independent variables: Positioning (Prone, right lateral and semi-elevated supine position) Dependent variables: Preterm newborn abdominal NIRS value, fractional oxygen extraction value, gastric residual volume.

Research Hypotheses H0: There is no difference between the effects of the three positions on gastric residual volume, abdominal oxygenation, and fractional oxygen extraction.

H1: Abdominal oxygenation and oxygen level (SPO2) are higher in the prone position than in the semi-elevated supine position and the right lateral position.

H2: Abdominal oxygenation and oxygen level (SPO2) are higher in the right lateral position than in the semi-elevated supine position.

H3: The amount of gastric residual volume in the prone position is lower than in the semi-elevated supine position and the right lateral position.

H4: The amount of gastric residual volume in the right lateral position is lower than in the semi-elevated supine position.

H5: Fractional oxygen extraction in the prone position is lower than in the right lateral and semi-elevated supine position.

Data Collection Method The data were collected from Kartal Dr. It will be collected in the neonatal intensive care unit of Lütfi Kırdar City Hospital. Study data will be collected by two investigators. The investigators responsible for the study, the subjects, and the statistician who will analyze the study will be blinded to the data. In the study, the blinding technique was planned as three blinds.

I ntroductory Information and Data Collection Form The intervention group of each participant included in the sample, week of gestation (according to last menstrual period), date, type of delivery, postnatal age, birth weight, postnatal body weight, gender, receiving intravenous fluid support, mean NIRS value, heart rate, and saturation value, amount and color of gastric residual volume before feeding, presence of a disease requiring medical treatment will be recorded.

To assess abdominal oxygenation (ArSO2), the NIRS sensor probe will be placed over the lower abdomen (under the umbilicus) and monitored. The participants who meet the inclusion criteria will be monitored through the NIRS for three feedings. Average NIRS values will be calculated for periods immediately before, during and after feeding. NIRS values will be recorded by the monitor, after the monitoring, the picture of the records will be taken from the monitor. During the follow-up, the location of the probe and the NIRS value will be followed by the investigators who collect data. The probe position will be changed to be in the lower abdomen before each feeding during the follow-up period. While NIRS values are recorded, pulse oximetry values will also be recorded.

Materials to be Used

1. Gastric residual volume Gastric residual volume will be checked manually using a 5 ml syringe prior to feeding. Gastric residue will be excreted or given back in consultation with the doctor according to its amount and color.

2. Breast Milk: Name and date control of the milk stored in milk storage bags in the refrigerator will be made. The breast milk drawn into the injector in accordance with the hygiene rules will be given to the participants after it reaches the appropriate temperature (must be at body temperature) in hot water. Heating breast milk above 40°C is not recommended as it will destroy immunologically active factors.

3. Positioning: Participants will be placed in the supine position during feeding. Feeding will be done every 2-3 hours. Participants will be positioned in one position for 2 hours after feeding.

   • Semi-elevated supine position
   • prone position
   • Right lateral position

Data Collection Feeding time will take 10-20 minutes. The participants will be included in the sampling from their 1st feeding after weaning off the mechanical ventilator. The procedure will begin when participants in all groups are calm. The entire application process will be carried out in the neonatal intensive care unit and all materials will be prepared before the procedure. In all three intervention groups, gastric residue will be checked with a 5 ml injector just before feeding, and the residual content will be discarded or returned with the decision of the doctor. The NIRS sensor probe will be attached to the lower abdomen. Since the cost of the probes is high, reversebl probes will be used and their cleaning will be provided with high-level disinfectant (Ecolab wipes). One NIRS probe will be used for two participants. The same enteral feeding protocol will be applied to all participants. In the institution where the study will be conducted, minimal enteral nutrition is started in participants, with breast milk being the first choice after 24 hours postnatally. Then, if the participant can tolerate enteral feeding, the amount is gradually increased each day. Decisions to increase feeding volume, stop feeding and use breast milk fortifier are made by the clinical team based on local protocols. The amount and frequency of feeding will be decided according to the gestational week, body weight and clinical condition of the participant.

Data Analysis NCSS (Number Cruncher Statistical System) 2020 Statistical Software (NCSS LLC, Kaysville, Utah, USA) program will be used for statistical analysis. While evaluating the study data, Shapiro Wilks test and Box Plot charts will be used to evaluate the conformity of the data to the normal distribution, as well as descriptive statistical methods (mean, standard deviation, median, frequency and ratio). Student's t test in the evaluation of two groups of normally distributed variables; Oneway Anova test will be used in the comparison of three groups and above, and the Bonferroni test will be used to determine the group that causes the difference. Repeated Measures test for evaluations according to three positions within the group; Bonferroni test will be used in post hoc evaluations and Paired Sample t test will be used in peer-to-peer evaluations. Mann Whitney U test in the evaluation of non-normally distributed variables according to two groups; Kruskal Wallis test will be used in the comparison of three groups and above, and Dunn test will be used to determine the group causing the difference. Friedman test post hoc Dunn test in the evaluations according to three positions within the group; Wilcoxon Signed Rank test will be used for peer-to-peer evaluations. Pearson or Spearman's correlation analysis will be used according to the distribution in the evaluation of the relations between the variables; Linear regression models will be made in further evaluations. Chi-square test and Fisher's Exact test will be used in the comparison of qualitative data. The results will be evaluated at the 95% confidence interval, at the p<0.05 level of significance.

Inclusion Criteria:

• Preterm newborns who are at 28-33 weeks of gestation according to the last menstrual period of the mother,
• Preterm newborns who are breastfed,
• Preterm newborns who are clinically stable and enteral feeding started,
• Preterm newborns who are first enteral nutrition 24 hours after mechanical ventilation,
• Preterm newborns who are at least 50% of their nutrition provided with enteral nutrition,
• Free Newborns fed by flow and orogastric tube and with informed consent of the parents will be included in the study.

Exclusion Criteria:

• Preterm newborns requiring mechanical ventilation,
• Preterm newborns diagnosed with NEC,
• Preterm newborns vomiting,
• Preterm newborns who have abdominal distension,
• Preterm newborns who have nasal mechanical obstruction,
• Preterm newborns who have congenital anomalies,
• Preterm newborns who have gastrointestinal problems such as gastroschisis or congenital diaphragmatic hernia,
• Preterm newborn who have cerebrovascular disease, apnea episodes, severe neurological disease, were included in the study. will not be included,
• Preterm newborns who worsen clinically after inclusion in the sample group will be excluded from the study.