Polygraphic recordings of respiration in neonates: a pointer to SIDS?AD Dua, PR Raikar
Department of Physiology, Grant Medical College, Mumbai.
Polygraphic respiratory recordings of 60 neonates were obtained from the infants in paediatric intensive care unit of a large public hospital. Thirty infants were pre-term and thirty infants were in the term (control) group. The recordings were analysed for periodic breathing and apnoeic episodes. Results were also determined for apnoeic density in pre-term and term Infants. Apnoeic episodes were found to be statistically significant in the pre-term infants over term Infants.
Keywords: Apnea, physiopathology,Equipment Design, Human, Infant, Low Birth Weight, physiology,Infant, Newborn, Infant, Premature, physiology,Respiration, Risk Factors, Sudden Infant Death, diagnosis,
Sudden, unexpected, unexplained death in infancy (SIDS) continues to represent grave problem of medical significance, silently claiming the lives of thousands of apparently well infants, without adequate explanation.
The typical patient is a generally healthy infant, two to five months old, who dies silently during sleep.
Although over a 100 hypothesis on its pathophysiologic mechanism have been postulated, strong evidence now suggests a primary respiratory event.
In some patients there is evidence of a defect in one or more of the control components, manifested by hypoventilation and insufficient increase in ventilation during exposure to hypercapnoea. Several authors had attempted to relate SIDS to Respiratory Tract Obstruction,. Yet others have explored the sleep state and its relation to apnoeic spells,.
The current study aims to show the vulnerability of pre-term infants to cot-deaths, implicating the disarray in respiratory rhythm as a probable cause. Polygraphic measurements of apnoea and periodic breathing during sleep have been taken.
The recordings of respiration were taken in the Neonatal Intensive Care Unit, Paediatrics Dept. of J.J. Hospital. Two groups of neonates were considered:
30 new born babies weighing between 860-2500 gm, considered Low Birth Weight (LBW) and Premature. 30 full term babies with normal weights and delivered normally were taken as Control group.
The gestation period was calculated according to the history given by the mother of the Last Menstrual Period and the date of delivery.
Mother’s consent was taken prior to recordings taken on the baby. After feeding, the babies were kept in a tray in sterile conditions. When the baby attained deep sleep, a thermister was gently kept in front of the nostril. As soon as the record started, the baby’s respiration record as well as the chest movements were observed. The colour of the baby’s skin and mucous membranes was noted when the apnoeic spells were on.
Records were taken on a polygraph via a respiratory amplifier, which is shown in [Figure - 1]. All the records were obtained for 800-1000 seconds as the baby does not remain in one position for longer period, even in deep sleep. In the wakeful state recordings by this method are extremely difficult to obtain. Records were taken on a polygraph via a respiratory amplifier.
An apnoeic event was arbitrarily defined as a pause equal to or exceeding six seconds. Periodic breathing was a cessation of breathing less than six seconds.
Statistical analysis was carried out to confirm the significance of all parameters of the study. The arithmetic means of all the parameters within each subjects record was obtained and variance from the mean calculated, with standard deviation.
The Standard Error of Mean was calculated for the control and study groups.
Unpaired t - test analysis of data was performed and the `P’ value was found.
The results obtained from the respiration records of 30 pre-term infants and 30 control term infants are shown in [Table - 1].
The ratio of apnoeic periods to total breathing time was significant (P<0.05) in the study group. Pre-term infants spent greater time in apnoea.
Both term and pre-term infants experienced periodic breathing and apnoeic episodes.
Periodic Breathing Patterns were not significantly different in pre-term and term groups of infants. Periodic breathing appears to be a normal breathing pattern in all infants below 2 months of age.
The deciding feature of significance in the respiratory records is the time spent by infants in apnoeic spells of >6 secs. The time spent in apnoea periods by pre-term infants is highly significant as compared to that spent by term infants. The average duration of the apnoeic spell is longer and more densely spaced in pre-term infants compared to term infants.
A good parameter in respiration records is the Apnoea Density which is A/D x 100% (see [Table - 1]). The apnoea densities of the study groups were significantly higher (P<0.001) in comparison to the control groups.
The gestational weight shows no correlation with apnoeic spells. They seem to be predominantly influenced only by the period of gestation and not by the weight.
Patterns of Respiration in Pre-term and Full-term infants have been studied polygraphically by various investigators. Incidence of Apnoea and periodic breathing has been documented by Hoppenbrowers et al and J.M. Richard et al. They observed apnoea commonly in neonates for the first three months after which it waned.
Hoppenbrowers also pointed to the importance of taking sleep-waking state into consideration while evaluating apnoea.
Goltzback SF state in 1989 that periodic breathing is a common respiratory pattern in pre-term infants that is not usually of pathologic significance; reinforcing the view of Southall D.P. et al, Ferrari F et al and Gordon D et al and their work in the past decade.
Alfred Steinschneider alone and with other co-workers deduced that apnoea, a physiological component of sleep is part of the final pathway resulting in SIDS. Pharyngeal and laryngeal dysfunction leading to obstruction of the airway and causing apnoea related SIDS was documented by Kuzemko et al and Rigatto et al.
Guilleminault et al in a series of studies implicated a deranged cardiorespiratory central control in sleep leading to SIDS.
The present study has clearly shown an increased apnoeic density in pre-term infants as compared to term infants. Apnoea and SIDS have been well-related. The results imply an increased risk of SIDS in the pre-term infant. Follow-up of these infants over a few months is desirable to prove this hypothesis conclusively.
The patterns could be due to one of the components of the ventilatory control system being abnormal, either inherently or because of an altered chemical environment or due to exaggeration of airway obstruction in sleep.
[Figure - 1][Table - 1]