BURBANK, CALIFORNIA (NYTIMES) -Ms Irma Mangayan was lathering and rinsing a 92-year-old woman in Room 413 one recent afternoon when she received a page from another room. An incontinent resident had an accident, and Ms Mangayan would have to clean it up.

Before her shift was over at Belmont Village Senior Living, Ms Mangayan would hoist women and men into their wheelchairs, escort residents using walkers downstairs to the dining room and perform myriad other tasks that they once could do for themselves.

Ms Mangayan is a personal care aide, a gruelling and low-paid profession that happens to be one of the fastest growing in the United States. It is also increasingly filled with foreign-born, low-skilled workers like Ms Mangayan, the kind now at the centre of a national debate on immigration.

A proposal favoured by a number of congressional Republicans and the Trump administration would replace the current family-preference immigration system, which critics call "chain migration", with one that favours skilled immigrants, while reducing admissions overall.

Democrats have balked at the plan, while some Republicans have insisted it be a condition of any Bill that legalises the unauthorised young adults, known as Dreamers, who could soon lose their protection against deportation.

Several attempts to reach a deal have failed, and a spending Bill passed on Friday (March 23) did not resolve the issue, leaving the fight over immigration reform for another day.

"It is time to create a merit-based immigration system that makes sense for a modern economy, selecting new arrivals based on their ability to support themselves financially and to make positive contributions to US society," the White House said in a statement last month. But economists do not necessarily agree.

Those who study immigration and labour patterns have questioned the wisdom of restricting family-based immigration, a crucial source of low-skilled workers, many of whom hail from countries like Mexico and the Philippines, where Ms Mangayan, 47, is from.

"In any plausible future scenario, the US needs far more new low-skilled workers than high-skilled workers, so many that it will be impossible for native labour to fill all those jobs, even if native workers wanted to," said Mr Michael Clemens, an economist at the Centre for Global Development, a Washington think tank.

A Bureau of Labour Statistics analysis notes that among the 10 occupations expected to grow fastest through 2026, only three require college degrees, all of them digital or data-focused: software developers, statisticians and mathematicians.

The two that will require the most new workers: personal care and home health aides, with 1.2 million new positions between them.

About 10,000 baby boomers turn 65 every day, and more than half will need long-term care, according to the Pew Research Centre. Already, homecare agencies and elderly-care facilities are struggling to recruit.

"If one of our aides is sick or has an emergency, it's very difficult to find a backup," said Mr Kevin Smith, president of Best of Care in the Boston area, who taps into the large Haitian and Brazilian communities in Massachusetts.

In 2017, 26 per cent of personal care aides and home health aides were foreign born, a high, according to an analysis of official data by Mr Brian Schaitkin, a senior economist at the Conference Board. In New York, 62 per cent of home aides were foreign born. In California, Massachusetts and New Jersey, foreigners represented nearly half of them.

Ms Lupe Mercado, a Mexican immigrant who works for an agency called 24Hr HomeCare in Los Angeles, has endeared herself to clients with dementia who initially cursed and flung food at her. One of them recently died holding her hand, Ms Mercado noted, brandishing a picture of the woman on her mobile phone.

On a recent afternoon, she doted on 92-year-old Olive Tanaka. "I'm spoiled by her," said Ms Tanaka, a line dancer in her day who is now widowed, blind in one eye and needs round-the-clock care since falling.

Having entered the United States without authorisation, Ms Mercado benefited from a 1986 amnesty law signed by president Ronald Reagan, obtaining a green card and eventually becoming a citizen.

"It doesn't pay so much, but I love my job," said Ms Mercado, who earns US$12 (S$16) an hour and supplements her pay by taking private clients on her days off.

Proponents of restricting immigration say the low wages in her field - and in other workplaces where immigrants have a foothold, such as construction, farms, and restaurant kitchens - are a prime reason immigrants have begun to supplant US workers in the jobs.

Some of those other professions, too, face worker shortages. A survey in September by the Associated General Contractors of America found that 70 per cent of construction firms had difficulty finding bricklayers, roofers and electricians, among others. Last August, the restaurant and accommodation sector had 742,000 vacancies, a historic high, according to the Bureau of Labour Statistics.

Stemming the flow of low-skilled immigrants could pressure employers to raise wages, compelling many Americans, including millions who are chronically unemployed, to go back to work.

"It may draw all these people, or some fraction of these people, into the labour force," said Mr Steven Camarota, research director of the Centre for Immigration Studies, which supports curbs on immigration.

Indeed, more people, but not enough, would do blue-collar work they now shun if wages were higher, said Mr Chris Tilly, a labour economist at UCLA.

"Wage is not the main issue," he said. "There are also expectations and status. Not everybody wants to work with their hands touching people; not everybody will do dirty work."

Supporters of an immigration overhaul cite other reasons the country should be choosier about whom it lets in.

The Trump administration has also framed it as a national security issue, noting several cases in which terror suspects came to the United States through family connections.

Immigrants are also more likely to use welfare programmes than native-born Americans, owing largely to their comparatively low skill levels upon arrival, the Centre for Immigration Studies says, citing Census Bureau data.

Under a House Bill introduced by Representative Bob Goodlatte and supported by the White House, citizens and permanent residents, or green card holders, could continue to bring spouses and children younger than 18 into the United States.

But they would no longer be able to sponsor parents, adult children, siblings, nephews and nieces.

The Bill would also create a point system for admission based on factors including education, English skills and job offers in the US, and it would cut the overall number of green cards awarded each year by half, to 500,000.

Employers who rely on immigrant labour are anxious about what will happen in Washington. Elder-care agencies in particular are worried because many are dependent on Medicaid and Medicare and so cannot, they say, easily raise wages to make their jobs more attractive to native-born workers.

If Congress makes it more difficult for relatives to immigrate, "where are all these workers going to come from?" asked Ms Patricia Will, founder of Belmont Village, a Houston-based network of upscale facilities that employs 4,000 people in several states.