As of 2018, there were only 3 in service in the US: https://people.com/health/polio-survivor-last-3-people-use-iron-lung/ https://people.com/health/polio-surviv

As of 2018, there were only 3 in service in the US: https://people.com/health/polio-survivor-last-3-people-use-iron-lung/ https://people.com/health/polio-survivor-last-3-people-use-i... There were quite a few interviews done in recent years with people who still rely on them; one recurring difficulty they talk about is that both expertise and availability of parts became scarce over time, so it becomes harder and harder to keep the machines running.