The lungs of Covid-19 patients struggle to get oxygen to vital organs. We examine what the virus can do to the lungs — and why ventilators can be the most important piece of equipment for the critically ill. nyti.ms/3bhPcWK
Human lungs are made up of millions of microscopic, balloon-shaped air sacs called alveoli, the workhorse of the respiratory system, where the exchange of gases takes place — oxygen into the bloodstream, carbon dioxide out if it. nyti.ms/3bhPcWK 
In a healthy lung, oxygen enters the bloodstream through a thin membrane between the air sac and a blood vessel.
That membrane also allows the carbon dioxide to escape the bloodstream back into the air sac, where it can be exhaled. nyti.ms/3bhPcWK
That membrane also allows the carbon dioxide to escape the bloodstream back into the air sac, where it can be exhaled. nyti.ms/3bhPcWK
In a lung infected by the coronavirus, the air sac can become inflamed and fill with fluid, limiting the body’s ability to take in oxygen and remove carbon dioxide. nyti.ms/3bhPcWK
Ventilators can help the infected lung by forcing air deep into the air sacs, dislodging the fluid that interferes with the exchange of gases. This process is not a cure, but it helps oxygen reach other organs so they can work properly while the body tries to fight off the virus.
The ventilator can assist with the patient’s breathing or control it completely. Skilled medical workers, along with the ventilator’s software, continually monitor and adjust the oxygen level in the lungs, because too much pressure can damage them. nyti.ms/3bhPcWK
Coronavirus patients connected to a ventilator are often kept on it for weeks to give their lungs a chance to heal. But the process, known as intubation, is fraught with peril. Patients must remain heavily sedated the entire time. nyti.ms/3bhPcWK
