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Acta Odontológica Latinoamericana

versão On-line ISSN 1852-4834

Acta odontol. latinoam. vol.26 no.3 Buenos Aires dez. 2013



Cyclical pattern of non-nutritive sucking in normal and high-risk neonatos


Alicia V. Simbrón1-2, Lucas Sorbera-Ferrer2, María E. Gómez de Ferraris2, Miriam L. Carranza2

1 Neonatology Service, University Maternity and Neonatology Hospital, Pediatrics Department, School of Medical Sciences, National University of Córdoba, Córdoba, Argentina
2 Department of Oral Biology, School of Dentistry, National University of Cordoba, Córdoba, Argentina.

CORRESPONDENCE Dr. Miriam Carranza. Espinosa Negrette 215. 5008. Cordoba, Argentina. e-mail:



This study determined patterns of suction cycles by recording sucking pressure in full-term infants, normal pre-term infants and newborns with pathology (hypoxia at birth). Associations between these patterns and some clinical parameters were established in order to evaluate feeding capacity for the purpose of guiding specific stimulation and aiding hospital discharge in better health conditions. Seventy-five infants of both sexes were assessed after informed consent, grouped by their status at birth. Body weight and Apgar score were determined. Sucking pressure was evaluated with an ad-hoc device. Maximum and minimum pressure scores and the number of suction cycles were measured. Data were analyzed statistically at a significance level of p<0.05. Maximum sucking pressure values varied between study groups. Full-term infants showed the highest pressure values and number of suction cycles. In pre-term infants, lower pressure values and fewer suction cycles were observed. Those with hypoxia showed great variability in both parameters. This study found a cyclical pattern of non-nutritive sucking in normal and high-risk newborns. Normal and preterm infants showed a significant direct correlation between suction cycles and Apgar scores at 5 minutes, but the infants with pathology due to hypoxia group did not show the same association. These findings are an important tool that will contribute to improving newborn maternal nutrition and optimizing the quality of life for high-risk newborns in our environment.

Keywords: Suction; Neonates.

Patrón cíclico de la succión no nutritiva en neonatos normales y de alto riesgo


En este trabajo se determinaron patrones de ciclos de succion mediante registros de la presion de succion en recien nacidos a termino, prematuro normal y recien nacido con patologia (hipoxia al nacer). Ademas, se establecieron asociaciones entre estos patrones y algunos parametros clinicos, con el proposito de valorar la capacidad de alimentacion, para orientar la estimulacion especifica y favorecer el alta de internacion en mejores condiciones de salud. Se evaluo a 75 neonatos de ambos sexos con consentimiento firmado, agrupados segun su condicion al nacer. Se determino el peso corporal y el score de Apgar. Se obtuvieron los registros de valores maximos y minimos de presion utilizando un aparato "ad-hoc" (de presion- succion) que permitio medir el numero de ciclos de succion. Los datos fueron analizados estadisticamente con un nivel de significacion p<0.05. Los valores maximos de presionsuccion presentaron variaciones entre los grupos analizados. Los valores mas altos de presion y el mayor numero de ciclos de succion se observo en nacidos a termino. Los prematuros mostraron valores de presion mas bajos y menor cantidad de ciclos de succion, lo que posibilito establecer un patron especifico para estos grupos. Los hipoxiados exhibieron una gran variabilidad en ambos parametros. En los neonatos normales y pretermino hubo una correlacion directa y significativa entre los ciclos de succion y los valores de Apgar a los cinco minutos. El grupo de recien nacidos con patologia debido a hipoxia no mostro la misma asociacion. Estos resultados constituyen una importante herramienta que contribuira a mejorar la nutricion materna neonatal y optimizar la calidad de vida de los recien nacidos de alto riesgo en nuestro medio.

Palabras clave: Succion; Neonatos.



Sucking is routinely evaluated at Neonatal Intensive Care Units (NICUs) through qualitative clinical observation of formula feeding or breastfeeding, and reported by nurses as good, fair or poor according to intake volume and time. It is used as an indicator of behavior and the success of oral feeding1, as well as being a diagnostic tool for detecting future developmental problems2. Sucking involves rhythmical coordinated movements of neuromus- cular and osteoarticular components3. Clinical assessments identify abnormal sucking and are of vital importance for managing dysphagia (with uncoordinated or weak sucking patterns), where the subject is unable to obtain an adequate volume of food within a given time, particularly premature newborns, whose proper coordination of sucking, swallowing and breathing reflexes needs to be assessed4,5. Lack of suck-swallow coordination due to immaturity or injury to neurological centers occurs in pre-term and small-for-gestational-age infants6. Evaluation of sucking in newborns is a useful rehabilitation strategy for starting oral stimulation programs to organize sucking components and improve feeding7.
Based on this background, this study determined suction cycle patterns by recording sucking pressure in full-term infants, normal pre-term infants and infants born with pathology (hypoxia at birth). In addition, associations were established between those patterns and some clinical parameters, in order to assess feeding capacity to guide specific stimulation, aiding hospital discharge in better health conditions.


Study design
This is a descriptive, observational, quantitative study of sucking pressure in normal full-term infants, pre-term infants and infants with hypoxia.

Sucking pressure was measured in 75 newborns of both sexes, grouped as: 1) full-term infants (controls: FTI, n=34), 2) pre-term infants (PTI; n=32) and 3) infants with pathology due to hypoxia (IPH; n=9) born at the Hospital Universitario Maternidad y Neonatologia (Cordoba National University - UNC), Argentina. The population was proportional to the number of births at this hospital over the same years (2004-2009).
This study was approved by the Bioethics Committee of the School of Medical Science at Cordoba National University in office at the time the study was begun, and follows the standards set forth in the Treaty of Helsinki. Newborns receiving care at the Neonatology Service through office visits or NICU were included with authorization from their parents (informed consent). All study groups were clinically stable (without respiratory assistance, hemodynamic compensation or generalized infections). The study procedure was safe and non-invasive. Infants were weighed on a digital pediatric scale and their Apgar score was determined. The 1 to 10 Apgar scale measures breathing effort, heart rate, muscle tone, reflexes and skin color. The higher the score, the better will be the infant's progress, while a score of less than 5 at five minutes after birth indicates probable perinatal hypoxia.
Non-nutritive sucking pressures were measured using an ad-hoc recording device (intellectual property No. 336022 registered at Argentina's National Intellectual Property Office [Direccion Nacional de Derecho de Autor]). The system consists of a pressure sensor with a piezoresistive silicon device and a transducer that transforms variations in pressure into electric current. It measures the pressure applied at one of its inputs compared to the reference pressure (pressure of a water column expressed in millimeters) which was used to calibrate the displacement of an air column in the device at different pressures. Another input is connected to a pacifier by means of a 50 cm length of latex tubing, both sterilized by autoclaving. The pressure recorded by the device is transferred to a computer and stored in an ExcelR database, which allows them to be viewed graphically. We determined the number of suction cycles per minute and established a profile of maximum values for sucking pressure expressed in millimeters of water column. The device was calibrated at three degrees of resistance (low, medium and high) and adapted according to sucking capacity. Low-resistance sensors were used for pre-term infants to prevent them from wasting energy, which might affect body weight gain. We made efforts to control the risk of any potential bias in this study by establishing commitment criteria such as clinical stability and the last feeding time at the time sucking pressure was recorded.

Statistical analysis
Data were entered into a database for statistical analysis and subject to descriptive statistics, twoway non-parametric tests to compare means (Mann Whitney's U-test and Kruskal Wallis) and linear correlation coefficient analysis (Spearman's test) using the software InfostatR 8. The significance level was set at p≤ 0.05.


Non-nutritive sucking pressure recorded for one minute showed moments of maximum pressure values followed by brief pauses. Minimum sucking pressure values expressed the passive return of the water column after the pressure applied. Maximum and minimum pressures formed sucking cycles, appearing as positive pressures greater than zero separated from each other by an interval of time (Figs. 1 and 2).

Fig. 1
: Maximum and minimum sucking pressure values in a full-term infant, expressed in millimeters of water column, in one minute.

Fig. 2
: Maximum and minimum sucking pressure values in a normal pre-term infant, expressed in millimeters of water column, in one minute.

In FTI, sucking pressure was low for the first few seconds while the infant adapted to the teat, followed by normal sucking up to 60 seconds, approximately (Fig. 1). Maximum sucking pressure values ranged from 16 to 20 mm water column using the high-resistance sensor.
In PTI, sucking pressure during the first 35 seconds was too low to be recorded, after which it increased and became more regular (Fig. 2). Maximum sucking pressure values ranged from 14 to 18 mm water column using the low-resistance sensor. In IPH, regular suction cycles were not observed. Most IPH showed maximum sucking pressure values ranging from 13 to 16 mm water column; the rest showed sucking pressure values either lower (33%) or higher (22%) than those, upon applying orofacial stimulation techniques.
In groups FTI and PTI, there was no significant difference in maximum sucking pressure values with relation to sex, although there was a significant correlation between maximum sucking pressure values and body weight (R= 0.33, p<0.05).
FTI performed more sucking cycles per minute than the other groups (Table 1). Apgar scores (FTI: 8.85 } 0.44; PTI: 8.75 } 0.62, IPH: 7.22 } 1.48) differed significantly among groups (p<0.0005), with the lowest values for IPH.

Table 1: Suction cycles in full-term infants, pre-term infants and infants with pathology.

*Mean values ± standard deviation (SD) differ between groups

In FTI and PTI there was a direct significant correlation between sucking cycles and Apgar scores at 5 minutes (R= 0.41, p<0.02). This association was not found for IPH.


Nutritive sucking involves lips, mandible, tongue, and hard and soft palate. The synchronous movement of tongue and jaw causes the liquid to flow, facilitated by the pressure seal of the lips. These coordinated actions generate the strong negative intraoral pressure that characterizes sucking. Nutritive sucking requires significant forces generated by the mandible and tongue in cycles of approximately 1 Hz, whereas in non-nutritive sucking, the cycles are 1 to 2 Hz 9.
Analysis of sucking is a sensitivity indicator used clinically in the evaluation of normal neurodevelopment based on sucking patterns10, knowledge of the biomechanics of the anatomical-histological and functional structures involved in sucking and the sucking times of newborns11.
Breathing, chewing and swallowing have cyclical motor behavior patterns, with a pattern of muscle activation and deactivation in each cycle. Behavior during sucking cycles may be similar. These activities may be controlled by a neuron network located in the brain stem and spinal cord, which regulates muscle activity for motor behavior12.
The system used for recording sucking in this study enabled measurement of sucking capacity, charting of sucking cycles and comparison of clinical appraisals to graphic records in full-term infants, pre-term infants and infants with pathologies. Sucking is a complex combination of muscular, joint and neurological activities, which requires systematized evaluation that will minimize any possible subjective appraisals of the force applied during sucking. The recording system used in this study clearly provides advantages over the usual method for evaluating suction by quantitative clinical observation. Quantitative determination of sucking pressure applied in one minute by full-term infants, pre-term infants and infants with pathology revealed sucking patterns with different numbers of cycles according to the characteristics of each group.
Full-term infants were able to apply greater pressure and perform more sucking cycles per minute than the other two groups 13. Pre-term infants were unable to perform the muscle activity required for sucking. Pre-term infants develop age-appropriate sucking patterns later and some attain it by 40 weeks gestation. Breathing, salivation and swallowing are altered in these infants, causing apnea and choking due to lack of coordination, which improves with gestational age, in agreement with reports from other authors5,13-15. Some studies are consistent with our findings, highlighting the importance of knowledge of these different sucking development stages in order to design appropriate therapies2, 10.
Other authors consider that proper neonatal sucking achieved at 40 weeks is a predictor of neurodevelopment2 and a monitoring strategy for high-risk newborns (HRN). Poorly coordinated sucking rate and swallowing may predict feeding and neurological problems, particularly in newborns with bronchopulmonary dysplasia4.
In this study, the sucking capacity in newborns with hypoxia was altered and showed no association similar to those observed in the other groups, which may be the result of alterations caused by the hypoxia with particular affectation on each newborn. These newborns may be rapidly fatigued due to their pathology, and be unable to complete the sucking cycle, requiring immediate early stimulation programs.
Knowledge of the cyclical sucking pattern and its direct association with the Apgar score in normal and high-risk newborns is an important tool for assessing neonatal breastfeeding. This is a starting point for further studies on sucking which will aid hospital discharge in better health conditions and optimize quality of life of high-risk newborns in our environment.


We thank Pedro R. Moya for his advice on project design and for facilitating access to the Neonatal Service, University Maternity and Neonatology Hospital (HUMN), National University of Cordoba, Cordoba, Argentina This work was supporteded by a grant from the Secretaria de Ciencia y Tecnologia (SECyT), Universidad Nacional de Cordoba. Resol No 214/2010, 26/2011.Argentina.


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