The intercostal-to-phrenic-inhibitory reflex (IPIR) in normal and intra-uterine growth-retarded (IUGR) human fetuses from 26 to 40 weeks of gestation.
The existence of an IPIR in the healthy fetus between 37 and 40 weeks of gestation has already been demonstrated: compression of the fetal thoracic wall during an epoch of fetal breathing movements (FBM) consistently caused a fetal apnea (> or = 4 s). The apnea durations were similar in fetal behavioural states 1F and 2F, with a wide inter- and intrafetal variability. We therefore hypothesized that the duration of the IPIR-apnea would increase during gestation and would be increased in IUGR-fetuses as compared to healthy fetuses of the same age. Twenty-six healthy fetuses between 28 and 40 weeks (mean 34.3 weeks) and 14 IUGR-fetuses between 26 and 38 weeks (mean 33.5 weeks) were studied. If FBM were present, the caudolateral part of the fetal thoracic wall was shortly compressed manually and the duration of the resulting apnea was measured. In a random order a sham-compression was also carried out on the fetal head. In normal fetuses 21/28 real compressions were followed by an apnea in 1F, while this was only the case in 3/21 sham-compressions (P < 10(-4)). For 2F these results were 47/57 and 7/51, respectively (P < 10(-4)). In IUGR-fetuses 43/51 real compressions (1F and 2F together) and 7/46 sham-procedures provoked an apnea (P < 10(-4)). These results prove the existence of the IPIR in normal and IUGR-fetuses. The mean (+/- S.D.) duration of apnea in the IUGR-fetuses was 15.8 s (+/- 4.0) (range 4-80 s) and 15.2 s (+/- 4.3) (range 4-106 s) in the normal group.(ABSTRACT TRUNCATED AT 250 WORDS)
Tas
B A
BA
Department of Obstetrics and Gynecology, University Hospital St-Radboud Nijmegen, Netherlands.
Nijhuis
J G
JG
Nelen
W
W
Willems
E
E
D001049:Apnea / Q000209:etiology / Q000523:psychology; D001519:Behavior / Q000502:physiology; D005314:Embryonic and Fetal Development / Q000502:physiology; D005260:Female; D005317:Fetal Growth Retardation / Q000503:physiopathology*; D005865:Gestational Age; D006801:Humans; D007367:Intercostal Nerves / Q000502:physiology*; D010791:Phrenic Nerve / Q000502:physiology*; D011247:Pregnancy; D012016:Reference Values; D012018:Reflex / Q000502:physiology*