Influence of the selective insufflation technique on cerebral blood flow in preterm infants

Abstract Introduction The intervention of respiratory physio-therapy in neonatal units is in continuous development, having its own care characteristics related to the weight and gestational age of the newborn, respecting the immaturity of the organs and systems and the diseases of this patient. Through techniques, the objective is to optimize the respiratory function, assisting in the clearance of secretions, and the restoration of lung volumes. Objective To verify if the respiratory physiotherapy technique of selective insufflation alters the cerebral blood flow in premature infants under 34 weeks of gestational age. Methods This is an uncontrolled clinical trial, conducted in a Neonatal Intensive Care Unit of a level III hospital, between January 2019 and March 2020, with participation of premature newborns under 34 weeks of gestational age. All were submitted to transfontanellar Doppler ultrasonography to assess cerebral blood flow measurements, mainly the resistance index, before and after the application of the selective insufflation respiratory physiotherapy technique. Results Sixty-two newborns were included, with a mean gestational age of 29.3 ± 2.2 weeks and birth weight of 1,259 ± 388 grams. The resistance index did not change significantly (RI before: 0.55 ± 0.07; after: 0.54 ± 0.07; p = 0.06) before and after the intervention and no studied variables such as, gender, gestational age, weight, Apgar score or SNAPPE II score had an influence on cerebral blood flow measurements. Conclusion The selective insufflation technique did not alter cerebral blood flow in premature newborn infants under 34 weeks gestational age.


Introduction
The intervention of respiratory physiotherapy in neonatal units is in continuous development, having its own care characteristics related to the weight and gestational age of the newborn, respecting the immaturity of the organs and systems and the diseases of this patient.1 Through techniques, the objective is to optimize the respiratory function, assisting in the clearance of secretions, and the restoration of lung volumes.1,2 The care must be performed by a specialized professional, who knows how to determine the need and the moment to intervene, with a well elaborated program, respecting the physiological and anatomical particularities of the newborn baby.The use of inappropriate techniques may cause instability and expose the newborn to adverse effects.[1][2][3] The developing premature newborn brain is extremely vulnerable.One of the aims of all neonatal care should be the prevention of brain damage.4 Newborns with birth weights less than 1,500 grams are particularly susceptible to brain injury, since autoregulation of cerebral blood flow (CBF) is not yet adequately established especially during the first five days after birth.Thus, it is essential to minimize blood pressure fluctuations by reducing handling, discomfort, and stress.The more premature the newborn, the more unstable and higher the risk of brain damage.5 Besides brain immaturity, premature birth also interferes The respiratory physiotherapy technique of selective insufflation is indicated to re-expand collapsed areas, restoring lung volumes.It consists of gently applying manual chest compression to one of the newborn's hemithoraxes so that the expansion of the contralateral hemithorax is favored.However, its influence on the CBF of preterm infants is not documented in the literature.8-10 In this context, the objective of the present study was to verify whether the selective insufflation technique alters the CBF of premature newborns assessed by means of transfontanellar Doppler ultrasonography.

Methods
This is an During all the handling, the newborns remained in their incubators, accommodated in their "nests", made with linens, whose use is standardized by the ICU, for comfort and to facilitate adequate posture.The temperature of the newborn was previously checked by the nursing professional responsible for care and the maximum handling time was 20 minutes.
With the newborn in dorsal decubitus, head in midline, the first Doppler ultrasound examination was performed by a single specialist physician, the findings were noted on the evaluation form.Then, the application of the respiratory physiotherapy technique was started and soon afterwards the Doppler ultrasound was repeated.The final results were also recorded, as well as the vital signs, evaluation by the pain scale and any alteration that occurred during the procedure.
The technique evaluated in the study was selective insufflation, which consists of gently and manually applying chest compression at the end of expiration on an entire hemithorax, with the newborn in dorsal decubitus and head centered.9 The release phase

Results
A total of 136 newborns were admitted to the ICU during the study period, of which 78 met the inclusion criteria and were recruited.Among those eligible for evaluation there were 16 sample losses (Figure 1).The SNAPPE II Severity Score ranged from 0 to 92 points, with nine (14.5%) scoring 39 or more and 50 patients (80.6%) scoring less.This score could not be assessed in three patients (4.8%), due to the absence of necessary information in the medical record.
The 62 newborns underwent a single assessment, performed on average at 7.7 ± 3.2 days of life.The mean weight at the time of evaluation was 1,206.0 ± 318.0 grams.Other information regarding ventilatory support is described in Table 1.
The CBF measurements studied are shown in     The strategy considered the gold standard for blood pressure measurement would be the invasive form, which would also allow the evaluation of its alterations during the application of the physiotherapy technique.However, not all newborns were indicated for the invasive device, reserved, due to the risks, for unstable or severely ill newborns.Nevertheless, even though blood pressure measurement was not available in the patients studied, it is reasonable to assume that there were no major changes since only stable newborns were included in the study.

Conclusion
The study provided knowledge on how the CBF of premature newborns behaves after the application of the selective insufflation technique of respiratory physiotherapy and how it interferes on the physiological parameters.It proved to be a procedure without deleterious repercussions in the population studied, that is, a safe technique to be used in premature newborns.
Studies evaluating the safety and effects of respiratory physiotherapy techniques in the neonatal and premature population are necessary, there are few clinical trials addressing the subject.

Authors´contributions
EOG, MGA, and RPGVCS were responsible for the study conception, and SAA, SRV, and RPGVCS for its design.Data analysis and interpretation were done by EOG, MGA, SRV, and RPGVCS, and manuscript writing by EOG.All authors reviewed the manuscript and approved the final version.
in pulmonary development and the occurrence of the Respiratory Distress Syndrome is frequently observed, caused mainly by insufficiency in the production of surfactant and pulmonary immaturity, generating the need for ventilatory support with positive pressure in an invasive or non-invasive way and the offer of supplementary oxygen.Lung disease causes increased production of bronchial secretion and increases the occurrence of collapse of lung areas, generating atelectasis.6,7 was always performed slowly.Chest compression was maintained for three timed minutes on the left hemithorax in all participants for standardization purposes, taking into consideration the newborn's clinical condition, ventilatory parameters, chest expansion and pulmonary auscultation at the time of evaluation.Those who were under invasive mechanical ventilation were evaluated only after radiological imaging that ensured the correct position of the cannula, avoiding handling newborns with atelectasis to the left due to malpositioning of the cannula.The technique was always applied by the same physiotherapist.CBF was evaluated by means of measurements obtained by transfontanellar Doppler ultrasound.The examination was performed during the study period following the routines of the service, at the bedside, by a pediatric neurologist physician who has specific training in cerebral ultrasonography and expertise in the area.The artery chosen for study was the pericallosal, a branch of the anterior cerebral artery, located adjacent to the genu of the corpus callosum, and the following parameters were assessed: RI (resistance index = SFV-DFV/SFV); systolic flow velocity (SFV) and diastolic flow velocity (DFV).The pericallosal artery was the first choice, but if this was not possible, due to the premature babies' characteristics, adjacent branches were used for measurement.The evaluation was made of at least five sequential stable waveforms for analysis.The Sono Site device, model M-Turbo®, with a 5 MHz transducer was used.During the whole procedure, vital parameters monitoring (heart rate; respiratory rate and peripheral oxygen saturation) was strictly carried out.The criteria for interruption were as follows: if the newborn presented signs of intolerance, such as bradycardia or drop in oxygen saturation to 20% of the initial value without immediate return with increased inspired fraction of oxygen, or signs of pain and stress without immediate consolation, pain was assessed using the Neonatal Infant Pain Scale (NIPS).

Figure 1 -
Figure 1 -Flow chart for data collection.
Transferred to another hospital (n = 5) Unstable without indication of respiratory physiotherapy (n= 37) Peri-intraventricular hemorrhage grade III or IV (n = 9) Refused to participate in the study (n = 2) Data analysis (n = 62) Unavailability of the evaluator (n = 14) Presented signs of pain and stress on the day of the evaluation (n = 2)

Table 2 .
It is observed that the RI and the DFV were not significantly altered after the selective insufflation technique, but there were significant alterations in the SVF measurements.Table3shows the analysis performed between the absolute measurements of CBF before and after the application of the technique and, the weight, gestational age and ventilatory support on the day of the evaluation.

Table 3 -
Distribution of the CBF measurements before and after the action of the respiratory physiotherapy technique according to the study (n = 62) Note: Data shown as mean.Weight and gestational age corrected according to their ratings on the day of the evaluation.CBF = cerebral blood flow; RI = resistance index (cm/s); GA = gestational age; O 2 = oxygen; NIV = non-invasive ventilation; IMV = invasive mechanical ventilation.*Anova one-way; post hoc Duncan's.

Table 1 -
Clinical characteristics of the study participants (n = 62) PIVH grade I and II, which corresponded to 16.1% of the sample.These findings are relevant considering that very premature newborns, 29.3 ± 2.2 weeks of gestational age and very low birth weight, 1,259.0 ± 388.0 grams were studied.

Table 2
Note: Data shown as mean and standard deviation.RI = resistance index; SFV = systolic flow velocity; DFV = diastolic flow velocity.*t Student for dependent sample.Gomes EO et al.Fisioter Mov.2023;36:e36117 6 The assessment of CBF in the neonatal period is still a challenge.Although ultrasound is an easily accessible device to assess cerebral circulation in the premature at the bedside, measurement of parameters is difficult in small-caliber vessels.11 Absolute velocity measurements such as SFV and DFV are difficult to compare because they depend on the insonation angle.On the other hand, the RI value is not affected by changes in this angle and is reproducible, with high inter-observer reliability.11,12 of nasal oxygen catheter, by means of transfontanellar Doppler ultrasound.The measurements of CBF were evaluated before, during and after physiotherapy with the technique of increased expiratory flow, as well as the vital parameters of the newborns.No significant changes were observed in the measurements of CBF or vital data with the application of the technique and the authors concluded that respiratory physiotherapy did not bring about changes in the CBF of the studied newborns.13 It is known that the ventilatory strategy in the neonate requiring support has consequences on the pulmonary and cardiovascular system and the immature brain.was no statistically significant difference in the RI between the groups with and without hemorrhage, although the group with PIVH was smaller (10 newborns), changes were found only in the absolute values of SFV (p = 0.04) and DFV (p < 0.01).

Table 4 -
27stribution of cerebral blood flow measures and the study variable (n = 62) before and after evaluation Pellicer A, et al.Diagnostic and predictive value of Doppler ultrasound for evaluation of the brain circulation in preterm infants: a systematic review.Pediatr Res.2020;87(Suppl 1):50-8.DOIobtain reliable results of blood pressure during handling for ultrasound and physiotherapy, as it is recommended that such measurements be performed with the patient at rest.27 Note: Data demonstrated as mean and standard deviation.PIVH = peri-intraventricular hemorrhage; M = male; F = female; FiO 2 = fraction of inspired oxygen; RI = resistance index; SFV = systolic flow velocity; DFV = diastolic flow velocity.*tStudent, independent groups.Gomes EO et al.