Lead author Dr Nicolas Dussex, of the University of Otago, New Zealand, and Swedish Museum of Natural History, says the team set out to investigate if it was external (habitat loss, mammalian predators) or internal (demography, genetic effects) factors which led to their extinction.

Very little was known about the forest songbirds he describes as “iconic and somehow mysterious,” which were last seen in 1960s and 1907 respectively, but recent advances in the extraction and analysis of ancient DNA provided the opportunity scientists needed to find out more.

The study, just published in Biology Letters, produced what Dr Dussex calls “very surprising” results.

The researchers mapped the birds’ complete genomes and saw a response to ice age climate change many thousands of years ago, but no signs of genetic problems common in small populations such as inbreeding. This suggests a rapid population decline possibly caused by habitat loss and new predators introduced by the Europeans.

“Because even the earliest Polynesian settlers more than 700 years ago had a significant impact on forest cover, we would have expected huia and South Island kokako populations to have survived at small population sizes for centuries and thus to have experienced an increase in inbreeding.

“However, our data did not show evidence for inbreeding and indicated that the two species still had quite a bit of genetic diversity close to the time of extinction. This means that their extinction was most likely not driven by genetic effects and inbreeding, but that further habitat loss and introduction of mammalian predators by European must have triggered a rapid extinction,” he says.

Dr Dussex says this is the first study to generate high-quality genomes from historical specimens of extinct New Zealand species.

“Using complete genomes allowed us to reconstruct the birds’ population history, and, more importantly, to determine whether genetic effects could have contributed to their extinction.

“While we focused here on two extinct species, understanding the role of genetic effects in the extinction process is extremely relevant to the study of declining and inbred populations, such as the kakapo, saddleback, and kiwi. This knowledge can thus contribute the conservation and recovery of endangered species potentially exposed to negative genetic effects.”

Co-author Dr Michael Knapp, of Otago’s Department of Anatomy, says the team hopes its work will stimulate similar research in other extinct or endangered endemic species from New Zealand.

“Recent advances in ancient DNA mean that it is the right time to study extinction from a genomics perspective. So far, very little is known about the role genetic effects play in the process of extinction. This research is thus very timely and extremely relevant to the understanding of the decline in biodiversity in New Zealand.”

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Materials provided by University of Otago. Note: Content may be edited for style and length.

Known as an alternating-pressure mattress, the high-tech devices contain air pockets that inflate and deflate to constantly change pressure points on the skin. They cost at least £1,000 each (US $1,217).

In comparison, a specialist foam mattress is around £200 (US $243) and is made up of high-quality polyurethane and viscoelastic foam designed to cradle the patient to reduce pressure on the skin.

The specialist foam mattresses are in widespread use across the NHS (National Health Service). The high-tech air mattresses are found on approximately 10% of NHS hospital beds and given to patients considered to be at high risk of pressure ulcers even though there has been no independent evaluation of their effectiveness.

The UK Government’s health regulator, the National Institute of Health and Care Excellence, had called for a scientific trial to investigate the benefits of the high-tech mattresses.

That study, led by nurse researchers at the University of Leeds, is published today (04/09/19) in the journal EClinicalMedicine.

Clinical benefit

The investigation showed that the gains from the use of the high-tech air mattresses were marginal. The paper concludes that for every 50 patients allocated to one of the high-tech air mattresses, only one would benefit from it.

The results showed that 6.9% of patients on the high-tech air mattresses developed a pressure sore that was grade two (ie blister or break in the skin) or worse compared with 8.9% on the specialist foam mattress. Ulcers are graded on a scale from one to four, with four being the most serious.

The median length of time it took for the ulcers to develop for the patients on a high-tech air mattress was 18 days compared to 12 days for those on the specialist foam mattress.

The paper — Pressure relieving support surfaces for pressure ulcer prevention: clinical and health economic results of a randomised controlled trial — also noted that the overall number of patients who developed pressure sores during the study was smaller than expected: the result, the researchers believe, of changes in nursing practice designed to reduce the burden of pressure sores.

This is the first large-scale study world-wide into the effectiveness of high-tech air and specialised foam mattresses to prevent pressure sores. It involved more than 2000 patients at high risk of developing pressure sores in hospital and NHS community units.

In 2018, NHS Improvement described pressure sores as a “concerning and avoidable harm” with the costs to the NHS of treating the condition running at more than £3.8 million every day.

Pressure sores are a major complication faced by people who are bedridden or immobile. The pressure that builds on soft tissue causes distortion to the tissues and/or an interruption to the blood supply — and that kills or damages skin leading to painful ulcers.

The study was led by Jane Nixon, Professor of Tissue Viability and Clinical Trials at the University of Leeds.

She said: “The professional guidelines tell healthcare staff that they should use specialist foam for all at-risk patients and high-tech air- mattresses for patients with an existing pressure ulcer when adequate pressure distribution cannot be achieved.

“But in practice, some nurses provide high-risk patients as well as those with existing pressure ulcers with the high-tech air mattresses and there has not been any evaluation of the effectiveness of one type of mattress over another.

“Some patients find the air mattress unsettling. They are kept awake by the noise of the pump, feel unsafe because the mattress is moving, or just find them uncomfortable.

“Rehabilitating patients also complain that they can’t move around themselves or get in and out of bed — and that exacerbates already limited mobility.”

Patients who agreed to take part were randomly allocated to either a high-tech air or specialised foam mattress for 2 months or until discharge, whichever came sooner. They were then assessed by a nurse for a final time 30 days after discharge. The majority of the patients were elderly, with the median age 81 and included a number of patients who were aged over 100.

The analysis suggested that the patients who benefitted most from the high-tech air mattresses were those who were completely immobile, confused, had nutritional deficits and very red skin on a pressure area.

Financial evaluation

The study found an economic advantage to using the high-tech air pressure mattresses. Although they cost more to buy, the patients who were nursed on them had, on average, a slightly shorter stay in hospital, and that reduced the overall cost of care.

More research is needed to fully understand the correlation between mattress type and length of hospital stay.

While acknowledging that there were benefits to using the high-tech air pressure mattresses, the researchers said that as the gains were small, the advice to nurses should be that most patients could be safely cared for on a specialised foam mattress.

Professor Nixon said: “The outcome of this study provides the evidence that specialist foam mattresses are appropriate for most patients who are at high risk of developing pressure ulcers.

“But staff should be free to exercise clinical discretion in provision of either mattress, informed by patient preference, comfort or rehabilitation needs as well as specific risk factors such as being completely immobile, being confused, having nutritional deficits or early signs of pressure damage.”