Dolphins are able to avoid decompression sickness when deep in the ocean by consciously dropping their own heart rates before diving, a new study revealed.
The condition, also known as the bends, occurs when dissolved gases come out of solution in bubbles and can affect just about any body area and can be fatal.
Researchers from the Fundación Oceanogràfic worked with dolphins to discover how they handle diving and depth changes without developing the condition.
They found that dolphins actively slow down their hearts before diving, and can even adjust their heart rate depending on how long they plan to dive.
Their findings, published in the journal Frontiers in Physiology, provide new insights into how marine mammals conserve oxygen and adjust to pressure while diving.
Researchers from the Fundación Oceanogràfic worked with dolphins to discover how they handle diving and depth changes without developing the condition
The research team worked with three male bottlenose dolphins specially trained to hold their breath for different lengths of time on instruction.
Dr Andreas Fahlman, lead author, said ‘We trained the dolphins for a long breath-hold, a short one, and one where they could do whatever they want.
‘When asked to hold their breath, their heart rates lowered before or immediately as they began the breath-hold.
‘We also observed that the dolphins reduced their heart rates faster and further when preparing for the long breath-hold, compared to the other holds.’
The results reveal that dolphins, and possibly other marine mammals, may consciously alter their heart rate to suit the length of their planned dive.
Dr Fahlman said: ‘Dolphins have the capacity to vary their reduction in heart rate as much as you and I are able to reduce how fast we breathe.
‘This allows them to conserve oxygen during their dives, and may also be key to avoiding diving-related problems such as decompression sickness,’ he said.
Understanding how marine mammals are able to dive safely for long periods of time is crucial to mitigate the health impacts of man-made sound disturbance on them.
‘Man-made sounds, such as underwater blasts during oil exploration, are linked to problems such as the bends in these animals,’ explained Dr Fahlman.
The research team worked with three male bottlenose dolphins specially trained to hold their breath for different lengths of time on instruction.
Avoiding sudden loud disturbances and instead slowly increasing the noise level over time would reduce stress levels for diving marine mammals, he said.
‘In other words, our research may provide very simple mitigation methods to allow humans and animals to safely share the ocean’.
Fahlman said the practical challenges of measuring a dolphin’s physiological functions, such as heart rate and breathing, have previously prevented scientists from fully understanding changes in their physiology during diving.
To solve the problem the team worked with a small sample of three trained male dolphins housed in a profession care facility.
Their findings, published in the journal Frontiers in Physiology, provide new insights into how marine mammals conserve oxygen and adjust to pressure while diving. Stock image
‘We used custom-made equipment to measure the lung function of the animals, and attached electrocardiogram (ECG) sensors to measure their heart rates,’ he said.
Andy Jabas is the Dolphin Care Specialist at Siegfried & Roy’s Secret Garden and Dolphin Habitat at the Mirage, Las Vegas, home of the dolphins who were studied.
He said: ‘The close relationship between the trainers and animals is hugely important when training dolphins to participate in scientific studies.’
‘This bond of trust enabled us to have a safe environment for the dolphins to become familiar with the specialised equipment and to learn to perform the breath-holds in a fun and stimulating training environment.
‘The dolphins all participated willingly in the study and were able to leave at any time,’ explained Jabas.
WHAT IS A HYPERBARIC CHAMBER AND HOW IS IT USED?
A hyperbaric chamber is a highly-pressurized room or tube where a patient is given pure oxygen to breathe.
The air pressure in these chambers is three times higher than normal pressure outside.
Lungs operate on gas exchange, which happens more or less efficiently at different pressures.
At this higher air pressure, the lungs are able to take in more oxygen than under normal conditions.
All the body’s tissues require oxygen to live and stay healthy, so in a hyperbaric chamber the lungs take in more oxygen which is then carried throughout the body to restore tissues that may be struggling or infected.
Oxygen also help to reduce inflammation and encourage new blood vessels to grow.
WHAT ARE HYPERBARIC CHAMBERS USED TO TREAT?
Hyperbaric oxygen therapy is a proven treatment for decompression sickness, a condition that some people develop after SCUBA diving, wherein the high pressure of being deep under water causes nitrogen to form in their blood vessels.
This typically causes muscle and joint aches and fatigue, but in rare cases can prove fatal. Hyperbaric oxygen therapy reverses the process that allows the dangerous nitrogen bubbles to form.
According to the Mayo Clinic, doctors may also recommend hyperbaric oxygen therapy for:
- Anemia, severe
- Brain abscess
- Bubbles of air in your blood vessels (arterial gas embolism)
- Burn
- Decompression sickness
- Carbon monoxide poisoning
- Crushing injury
- Deafness, sudden
- Gangrene
- Infection of skin or bone that causes tissue death
- Non-healing wounds, such as a diabetic foot ulcer
- Radiation injury
- Skin graft or skin flap at risk of tissue death
- Vision loss, sudden and painless
Although claims have been made that the therapy helps a whole hosts of other medical issues, there is only scientific evidence to support the above uses.
There isn’t significant reason to believe it treats conditions like fibromyalgia, depression or chronic fatigue syndrome.
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