Canet E, Praud J P, Laberge J M, Blanchard P W, Bureau M A
Centre Jeremy Rill, Département de Pédiatrie, Faculté de Médecine, Université de Sherbrooke, Quebec, Canada.
J Appl Physiol (1985). 1993 Jun;74(6):3013-9. doi: 10.1152/jappl.1993.74.6.3013.
This study was designed to determine the effect of the removal of chemical stimuli on breathing rhythmicity in awake newborn lambs; it was also designed to define the chemical threshold below which breathing would stop [arterial PCO2 (PaCO2) apnea threshold]. We used a technique of graded extracorporeal CO2 removal with apneic oxygenation in three groups of animals according to age and carotid body (CB) integrity: < 2 days, CB intact (n = 5); 12 days, CB intact (n = 7); and 12 days, CB denervated (CBD; n = 5). In all animals, whatever their age and CB status, suppression of the chemical drive resulted in sustained apnea. The study, performed at four constant levels of oxygenation (hyperoxia, normoxia, moderate hypoxia, and severe hypoxia), allowed precise determination of the PaCO2 apnea threshold. We found that this PaCO2 apnea threshold depended on the degree of postnatal maturation (it was higher in the younger lambs), the level of arterial oxygenation (it was lowered by hypoxia), and CB status (it was higher in CBD animals). Moreover, we found that the 12-day-old CBD lambs breathe at a level of PaCO2 set close to the point of apnea.(ABSTRACT TRUNCATED AT 250 WORDS)
本研究旨在确定去除化学刺激对清醒新生羔羊呼吸节律的影响；同时也旨在确定呼吸停止时的化学阈值[动脉血二氧化碳分压（PaCO2）呼吸暂停阈值]。我们采用了一种在三组动物中通过无呼吸氧合进行分级体外二氧化碳去除的技术，这三组动物根据年龄和颈动脉体（CB）完整性划分：小于2天，CB完整（n = 5）；12天，CB完整（n = 7）；以及12天，CB去神经支配（CBD；n = 5）。在所有动物中，无论其年龄和CB状态如何，化学驱动的抑制都会导致持续性呼吸暂停。该研究在四个恒定的氧合水平（高氧、常氧、中度低氧和重度低氧）下进行，从而能够精确测定PaCO2呼吸暂停阈值。我们发现，该PaCO2呼吸暂停阈值取决于出生后的成熟程度（较年幼的羔羊中该阈值更高）、动脉氧合水平（低氧会降低该阈值）以及CB状态（CBD动物中该阈值更高）。此外，我们发现12日龄的CBD羔羊在接近呼吸暂停点的PaCO2水平下呼吸。（摘要截选至250词）
