Abstract
The Hearing-Breuer inflation reflex (H.B.i.r.) and the thoracic respiratory reflex (th.r.r.) have been studied in 17 babies of different postmenstrual age (30½ to 13 weeks). Pronounced development of the strength of the reflexes have been found indicating the existence of differences in the mechanoreceptor regulation of breathing between infants of this maturity level and adults.
The H.B.i.r. was studied by tidal volume inflation obtained by occluding the airways at the height of an inspiration. The strength of the reflex was assessed by relating the relative increase of the length of the breathing cycle to the transpulmonary pressure at the moment of occlusion (thus the pressure which simultaneously stimulates the pulmonary stretch receptors). The reflex was found to be very weak at a postmenstrual age of 32 weeks. It increased to a maximum strength at a postmenstrual age of 36 to 38 weeks. Later on there was a decline of the strength of the reflex.
The th.r.r. was studied as the reflex respiratory response to an added respiratory load and recorded as the change in amplitude of the intraesophageal (=intraplecural) pressure swings caused by airway occlusion. It has earlier been shown in adults that an increase of the respiratory load leads to an increased power generation of the respiratory muscles reflected as an increasing amplitude of the intrapleural pressure swings. In the babies studied the response to an increased respiratory load was found to increase gradually with increasing postmenstrual age indicating increasing maturation of the thoracic respiratory reflex system.
In some babies estimations both of the strength of the H.B.i.r. and the th.r.r. were made at repeated occasions and the same principal development of the reflexes was seen in the single baby as was seen from cross-sectional data in all the infants studied.
Furthermore there was found a dip in the development of the th.r.r. at the time when the H.B.i.r. reaches its maximum which might indicate some kind of competition between the two reflex systems. Such a competitive interaction could also explain why the H.B.i.r. decreases in strength after 38 weeks of age weeks of age when the th.r.r. contunues to increase in strength.
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Bodegård, G., Schwieler, G. 35. Respiratory reflexes in the newly born. Pediatr Res 5, 90 (1971). https://doi.org/10.1203/00006450-197102000-00040
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DOI: https://doi.org/10.1203/00006450-197102000-00040