Experimental study on a causal relationship between sleeping in a face-down position and sudden death in infants

[方法]用聚氨酯树脂制作婴儿死亡口罩，施加1.5 kg的垂直载荷，观察被褥对健康婴儿是否存在致死性低氧血症。一根气管导管被放置在一只小猪身上，并连接到面罩的鼻腔，小猪通过鼻腔呼吸。连续监测血压(BP)、心率(HR)、动脉血氧饱和度(O2sat)、呼吸频率(RR)、呼气氧浓度(ExO2)和呼气二氧化碳浓度(ExCO2)，必要时监测动脉血氧分压(PaO2)和动脉二氧化碳分压(PaCO2)。床上用品使用软硬日式床(蒲团)和俯卧专用床垫。[结果]1.当面罩朝下放置在柔软的蒲团上时，动物立即开始用力吸气。氧分压和氧分压在3分钟内迅速下降，氧分压在3分钟后降至29.8毫米汞柱。面罩放置3分钟后，呼吸状况及各项测定值迅速恢复正常。2.将面罩放置在硬垫上，5分钟后PaO2逐渐降至44.2 mm Hg，25分钟后降至30.1 mm Hg，35分钟后降至31.0 mm Hg。O2sat和ExO2也逐渐下降，50分钟后动物死亡。3.相应地将口罩放在俯卧专用床垫上，5分钟后PaO2降至36 mm Hg。O2sat和ExO2在入睡前3分钟迅速下降，之后逐渐下降，与BP、HR和RR一样逐渐下降，25分钟后死亡。[结论]俯卧位，尤其是面朝下卧位时，婴儿可能会因口鼻被盖引起的低氧血症而迅速死亡。

An animal experiment was conducted to investigate whether covering both nose and mouth by bedding may cause lethal hypoxemia in healthy infants.[Methods]A mask of a dead infant was made of polyurethane resin, and a vertical load of 1.5 kg was added. An endotracheal tube was placed in a piglet and linked to the nasal cavity of the mask, through which the piglet breathed. Blood pressure (BP), heart rate (HR), arterial oxygen saturation (O_2sat), respiratory rate (RR), expired air oxygen concentration (exO_2) and expired air carbon dioxide concentration (exCO_2) were monitored continuously, and arterial oxygen concentration (PaO_2) and arterial carbon dioxide concentration (PaCO_2) were monitored as necessary. For bedding, soft and hard Japanese beds (futons) and a mattress dedicated for prone sleeping were used.[Results]1.When the mask was placed in a face-down position on the soft futon, the animal immediately started forced inspiration. O_2sat and exO_2 quickly decreased within three minutes, and PaO_2 decreased to 29.8 mmHg three minutes later. When the mask was placed in a face-up position three minutes later, respiratory condition and all test values quickly returned to normal.2.When the mask was correspondingly placed on the hard futon, PaO_2 gradually decreased to 44.2 mmHg five minutes later, 30.1 mmHg 25 minutes later and 31.0 mmHg 35 minutes later. O_2sat and exO_2 also gradually decreased, and the animal died 50 minutes later.3.When the mask was correspondingly placed on the mattress dedicated for prone sleeping, PaO_2 decreased to 36 mmHg five minutes later. O_2sat and exO_2 quickly decreased for the first three minutes and thereafter decreased as gradually as BP, HR and RR did, and the animal died 25 minutes later.[Conclusion]These findings suggest that infants may quickly die from hypoxemia caused by both nose and mouth being covered by bedding while they sleep in a prone position, especially in a face-down position.