Deep diving whales and other marine mammals can get the bend – the same painful and potentially life-threatening decompression sickness that hits divers who emerge too fast. A new study offers a hypothesis on how marine mammals generally avoid getting the bends and how they can succumb to stressful conditions.
The key lies in the unusual lung architecture of whales, dolphins, and bottlenose dolphins (and possibly other breathing-diving vertebrates) that create two distinct lung regions under intaglio, say researchers from the Woods Hole Oceanographic Institution (WHOI). and the Fundacion Oceanografic in Spain. Their study was published on April 25, 2018 in the journal Proceedings of the Royal Society B .
"As some marine mammals and turtles repeatedly dive as deep and as long as they do, scientists have a very long confused confusion," says Michael Moore, director of the Marine Mammal Center at WHOI and co-author of the study. "This paper opens a window through which we can get a new perspective on the question."
When air-breathing mammals dive at high-pressure depths, their lungs become more dense. This collapses their alveoli – the small sacs at the end of the respiratory tract where gas exchange takes place. Nitrogen bubbles form in the bloodstream and tissues of the animals. When they rise slowly, the nitrogen can return to the lungs and be exhaled. But if they rise too fast, the nitrogen bubbles do not have time to diffuse back into the lungs. Lower pressure at shallower depths expands the nitrogen bubbles in the bloodstream and tissues, causing pain and damage.
The breast structure of marine mammals compresses their lungs. Scientists suspect that this passive compression was the major adaptation of marine mammals to avoid the uptake of excess nitrogen in the deep and curvature.
In their study, researchers took CT images of a deceased dolphin, seal, and a pressurized domestic pig in a hyperbaric chamber. The team was able to see how the marine mammal lung architecture creates two pulmonary regions: one air-filled and the other collapsed. The researchers believe that blood flows mainly through the collapsed region of the lungs. This causes a so-called ventilation-perfusion mismatch, which allows some oxygen and carbon dioxide to be absorbed by the animal's bloodstream while minimizing or preventing the exchange of nitrogen. This is possible because each gas has a different solubility in the blood. The country pig did not show this structural adjustment.
This mechanism would protect whales from taking up excessive amounts of nitrogen, thus minimizing the risk of curvature, says lead author Daniel García-Parraga of Fundacion Oceanografic.
However, he said: "Excessive stress, as it can occur when exposed to human sound, can cause the system to fail and the blood to flow into the air-filled areas, which would increase gas exchange and increase nitrogen Blood and tissue readings when the pressure decreases during ascent. "
Scientists once thought that marine mammal diving was immune to decompression sickness, but a 2002 beaching incident associated with marine sonar exercises revealed that 14 whales died after stranding The Canary Islands Islands had gas bubbles in their tissues – a sign of curvature. The researchers say the paper's findings may support the earlier effects of decompression sickness in some ocean beaches.
The team says further research is developing tools to analyze changes in lung flow and ventilation patterns that require stressors in diving.
Study examines how marine mammals dive with decompression
Pulmonary Ventilation-Perfusion Mismatch: A Novel Hypothesis of How Submerged Vertebrates Can Avoid Curvatures Proceedings of the Royal Society B rspb.royalsocietypublishing.or … .1098 / rspb.2018.0482