Blood Gas Determinations on Premature Infants III. Investigations on Premature Infants with Recurrent Attacks of Apnea

Abstract

An extensive literature has grown up concerning the respiratory complications of the premature infant. I n spite of this, the number of wellestablished facts is still relatively small.Through blood gas determinations the author has made an attempt to clarify the respiratory situation in a number of premature infants. The study includes examination of 9 infants without any respiratory difficulties and of 12 infants who were in serious respiratory distress.This publication is the first of a series of three. Here, the laboratory methods are described, and the results obtained on premature infants without any respiratory complications are reported.Earlier investigations indicate that premature infants, in cases without neonatal complications, probably do not suffer from severe respiratory insufficiency. The arterial oxygen saturation seems to differ very little from normal values for adults (GRAHAM and co-workers, JONXIS). The acid-base conditions in a large number of premature infants have been investigated by REARDON and co-workers. The average CO, tension in this material was 38 mm Hg, which does not differ much from that of normal adults. The results showed a relatively wide spread, however, and in 10 per cent of the cases a respiratory acidosis was present.This study on normal prematures represents a re-investigation of the problem, in which a somewhat different laboratory method has been employed. It is, besides, a necessary basis for evaluating the displacements in the values which are seen in premature infants suffering from severe respiratory complications.

Acid-Base Status of ”Normal” Premature Infants in the first Week of Life

“…Seven su b je c ts (4 from G roup A a n d 3 from G roup B) w ho h a d from 1 to 3 apnoeic spells of v e ry sh o rt d u ra tio n reco v ered sp o n ta n e o u s ly : th e y w ere in clu d ed becau se th e y w ere otherw ise n o rm al b y careful an d re p e a te d clinical an d neurological e x a m in a tio n , an d becau se it has been show n t h a t s h o rt periods o f ap n o ea can affect th e acid-base s ta tu s for only a lim ite d tim e [7]. T he 3 in fa n ts from G roup B, w ho died a fte r apnoeic spells, w ere included because th e y h a d no sy m p to m s for a t le a s t 4 d ay s a fte r b irth a n d because no cause o f d e a th could be recognized a t a u to p s y ; since th e ir d e a th could be in som e w ay re la te d to th e d ev elo p m en t o f acidosis, we felt t h a t th e ir exclusion w ould be u n ju stified.…”

Efficiency of Respiratory Compensation for Metabolic Acidosis in Premature Infants

“…T his conclusion is su p p o rte d b y sim ilar findings in h ea lth y p rem atu res b y o th e r w orkers. T h e sp read of p H -v alu es in th e series of R ea r d o n [5] e x te n d e d from 7.21 to 7.48; in th a t o f G oldman [7] from 7.22 to 7.53, an d in B lystads [6] cases from 7.24 to 7.49, while in Chernicks [10] cases e x h ib itin g periodic b re a th in g w ith o u t m etabolic acidosis, p H v a rie d from 7.26 to 7.53. T his leads us to th e q u estion of th e clinical significance o f acidosis.…”

“…T he causes of th e te n d e n c y to acidosis h a v e n o t been fu lly clarified. W hile av ailable evidence sug g ests lim ited ren al e x c re to ry c a p a c ity for hyd ro g en ions in n ew b o rn in fa n ts [8][9], d a ta on re sp ira to ry co m p ensation yielded so m ew h at c o n tra d ic to ry resu lts [5,6,10]. T his w ork is lim ited to th e s tu d y o f th e a b ility o f y o u n g p re m a tu re in fa n ts to com pensate for m etab o lic acidosis w ith re sp ira to ry a d ju s tm e n ts, a n d to th e com parison of th e degree o f co m p en satio n achieved w ith th a t observed in older age g roups.…”

The lungs at birth.

“…Indeed the absence of surfactant can account for all the findings in this condition. Extensive atelectasis due to the surfactant deficiency causes the low lung compliance (Gribetz, Frank, and Avery, 1959) which in turn leads to ventilatory insufficiency (Blystad, 1956;Strang and MacLeish, 1961) and to right-to-left shunting (Strang and MacLeish, 1961;Warley and Gairdner, 1962;Prod'hom, Levison, Cherry, Drorbaugh, Hubbell, and Smith, 1962). According to Pattle (1965) the presence of the hyaline membranes, which are I I --I 580 THE LUNGS AT BIRTH mainly a blood transudate (Gitlin and Craig, 1956), can also be explained as an effect of a high alveolar surface tension which sets up a pressure gradient between the air space and the underlying capillary during any phase of ventilation in which the alveolus is held open.…”