The two Medical Centers on the eastside of Lake Washington are Evergreen and Overlake with bed capacity of 318 and 349 respectively. Overlake has 32 ICU beds and, since I have not found numbers for Evergreen's, it's reasonable to assume Evergreen's is the same - a total of 64 ICU beds for the eastside of the Seattle metro area. Not all are medical units. Their counts may include Trauma, Cardiac, possibly Burn or Neuro units.
Medical ICU bed with isolation rooms equipped with negative pressure usually make up 10% of ICU bed capacity. So let's say the two Medical Centers may have 6 or 7 isolation rooms with rooms with negative pressure HVAC systems to contain respiratory droplet infection spread.
Staff - these type of isolation rooms in ICUs have increased labor-intensive work, entering a room, putting on protective gear, transferring any new equipment/supplies/meds with a RN dedicated to that patient with perhaps another much less severe, but critical. The hospital has gone into emergency mode, transferring patients to lower level of care or to other hospitals. These critical care nursing positions require specialized training and certifications. Hospitals may contract with agencies for critical care nurses if they cannot fill the positions locally. Prior to the epidemic Evergreen was advertising for more critical care nurses.
To complicate things, hospital staff may have been sent home to self-quarantine for two weeks due to exposure without appropriate protective equipment to coronavirus patients previously, increasing shortages. Reports are that hospitals do not have enough of the n95 respirator masks that protect against the small particles of viruses. In past outbreaks like SARS or in other areas with COVID-19, many HC professionals from EMTs to physicians have sickened and some have died.
As Oahu noted, this has been a bad flu season, filling beds in a hospital already. Existing patients in both hospitals may have been transferred to other Seattle area hospitals to open up beds and undoubtedly Evergreen and Overlake diverting ambulances from their ERs to other hospitals.
With the eastside hospitals transferring patients to other area hospitals, those too may be having significant increases in occupied beds and undergoing staffing shortages. HC workers with pre-existing pulmonary conditions like asthma would have to take extra precautions to reduce their exposure - or stay at home.
It probably goes without saying that as ICUs fill up as well as hospitals reaching their bed capacity, patients who are admitted remain in the ER.
The cities that the two medical centers - Overlake in Bellevue and Evergreen in Kirkland - have a total population of 220,000. That does not include any of the other cities on that side.