One Seattle-area hospital system has set up its own makeshift assembly line — using parts purchased from Home Depot and craft stores — to create protective face shields for workers. Boston nurses are gathering racquetball glasses to use in place of safety goggles. In New York, a dialysis center is preparing to use bandannas in place of masks as protection against the novel coronavirus. Just 11 weeks into a pandemic crisis expected to last months, the nightmare of medical equipment shortages is no longer theoretical. Health-care workers, already uneasy about their risk of infection amid reports of colleagues getting sick and new data showing even relatively young people may become seriously ill, are frustrated and fearful. “That has really freaked everybody out,” said Elissa Perkins, an emergency medicine physician at Boston Medical Center. President Trump responded to the growing crisis Wednesday by invoking the Defense Production Act to mobilize war-scale manufacturing for critical items, and federal health officials have announced plans to buy 500 million N95 respirators over the next 18 months. Also, Vice President Pence said legislation signed Wednesday gives manufacturers p...