Nature and incidence of bubbles in the spinal cord of decompressed goats

The nature of so-called autochthonous bubbles was investigated. Their presence in compressed/decompressed goats was compared with that in animals killed before decompression and in controls. Ten goats (group 1) were subjected to compression/decompression in air. Clinical signs of spinal decompression sickness usually occurred. Within 35 min of surfacing, the animals were given a lethal dose of thiopentone sodium, i.v.. Spinal cords were fixed by immersion in 10% formol saline. Histologically autochthonous bubbles appeared to arise from rupture of over-distended blood vessels. The incidence of grossly dilated empty vessels (GDEV) was recorded. Seven goats (group 2) were similarly compressed but killed before decompression. In five animals of group 1 there was a greater number of GDEV than in controls (group 3, seven animals) but in the other five animals the incidence was similar to the controls. The incidence of GDEV in group 2 was greater than in the controls (P < 0.05). The percentage of sections of spinal cord in which the meninges also contained GDEV was assessed. In all except two animals in group 1, the percentage was higher than in the controls, whereas in group 2 the percentage was higher than in the controls. The experiments show that autochthonous bubbles arise as an artifact and that intravascular bubbles arise in situ.