Do we still use negative pressure ventilation?

Yes, we still use negative pressure ventilation in modern medicine and engineering, though its applications have evolved and it is used in specific contexts rather than as a general breathing method. In healthcare, negative pressure ventilation in the form of negative pressure rooms, also called airborne infection isolation rooms, is standard and widely used in hospitals worldwide to contain airborne infectious diseases like tuberculosis, measles, chickenpox, and for COVID patients during aerosol-generating procedures. These rooms use HEPA filtered negative air machines that keep pressure lower inside than outside so contaminated air does not escape. In construction and remediation, negative pressure ventilation is standard for mold remediation, asbestos removal, and lead abatement, where containment with negative air machines prevents hazardous dust from spreading to clean areas, required by OSHA and IICRC standards. In building ventilation, negative pressure is sometimes used to exhaust stale air from bathrooms and kitchens. Historically, negative pressure ventilation for breathing was used in iron lungs for polio patients in the 1950s, where a machine created negative pressure around the chest to draw air into lungs, but this has been largely replaced by positive pressure ventilators that push air in via a mask or tube, which are more efficient and easier to manage. However, modern cuirass ventilators still use negative pressure around the chest for some patients who cannot tolerate positive pressure. So yes, negative pressure ventilation is very much in use today for containment and specialized medical devices.