Chan K, Kullama L K, Day L, Ogundipe A, Ross M G
Department of Obstetrics and Gynecology, Harbor-UCLA Medical Center, Torrance 90502, USA.
Otolaryngol Head Neck Surg. 1997 Jan;116(1):91-6. doi: 10.1016/s0194-5998(97)70356-5.
In newborn infants, laryngeal contact with solutions of low chloride concentration or pH evokes swallowing, laryngeal adduction, and respiratory inhibition (laryngeal chemoreflex). To determine whether the laryngeal chemoreflex is present during fetal life and its effect on fetal respiratory activity, eight time-bred ewes (128 +/- 2 days) were prepared with fetal electrocortical diaphragm and esophageal electrodes and a nasopharyngeal catheter. After a 60-minute control period, increasing volumes (0.1 to 1.0 ml/kg) of 0.15 mol/L NaCl or distilled water (0.05 to 1.0 ml/kg) and decreasing concentrations of NaCl (0.15 to 0.02 mol/L) at a fixed volume (0.3 ml/kg) were sequentially administered through the nasopharyngeal catheter (38 degrees C). The minimum water volume that stimulated swallowing was significantly less than the minimum 0.15 mol/L NaCl volume (0.10 +/- 0.02 vs. 0.70 +/- 0.05 ml/kg). The maximum NaCl concentration that stimulated swallowing was 0.04 +/- 0.01 mol/L During the control period, respiratory activity averaged 14.6 +/- 0.7 breaths/minute and did not change during absent swallow responses or isotonic saline-induced swallows. However, respiratory activity significantly decreased during water (4.7 +/- 0.6 breaths/minute) and hypotonic saline-induced swallow responses (3.7 +/- 0.7 breaths/minute). Fetal electrocortical activity did not change during absent or stimulated swallows. We conclude that laryngeal water or hypotonic saline solution may stimulate fetal swallowing and suppress fetal respiratory activity, similar to the newborn laryngeal chemoreflex. We speculate that an exaggeration of the laryngeal chemoreflex apnea response in the newborn may predispose to sudden infant death syndrome.
在新生儿中，喉部接触低氯浓度或低pH值的溶液会引发吞咽、喉部内收和呼吸抑制（喉部化学反射）。为了确定胎儿期是否存在喉部化学反射及其对胎儿呼吸活动的影响，对8只经定时配种的母羊（妊娠128±2天）进行了准备，在胎儿身上植入了皮质脑电图、膈肌电极和食管电极以及一根鼻咽导管。在60分钟的对照期后，通过鼻咽导管（38℃）依次给予递增体积（0.1至1.0 ml/kg）的0.15 mol/L氯化钠溶液或蒸馏水（0.05至1.0 ml/kg），以及固定体积（0.3 ml/kg）但浓度递减的氯化钠溶液（0.15至0.02 mol/L）。刺激吞咽的最小水量明显少于刺激吞咽的最小0.15 mol/L氯化钠溶液量（0.10±0.02与0.70±0.05 ml/kg）。刺激吞咽的最大氯化钠浓度为0.04±0.01 mol/L。在对照期，呼吸活动平均为14.6±0.7次/分钟，在无吞咽反应或等渗盐水诱导的吞咽过程中没有变化。然而，在水诱导（4.7±0.6次/分钟）和低渗盐水诱导的吞咽反应期间（3.7±0.7次/分钟），呼吸活动显著降低。在无吞咽或刺激吞咽期间，胎儿皮质脑电图活动没有变化。我们得出结论，喉部接触水或低渗盐水溶液可能刺激胎儿吞咽并抑制胎儿呼吸活动，这与新生儿喉部化学反射相似。我们推测，新生儿喉部化学反射性呼吸暂停反应的过度增强可能易导致婴儿猝死综合征。
