Question

Paramedics transport a 30-year-old woman, gravida 2, para 1, at 34 weeks gestation to the emergency department for severe, acute-onset difficulty breathing. She has a history of moderate persistent asthma but stopped her inhaled medications weeks ago due to concerns about fetal safety. Over the past 90 minutes in the emergency department, she has been treated with continuous nebulized albuterol and ipratropium, as well as intravenous methylprednisolone. Despite these measures, her work of breathing remains highly labored. Vital signs are temperature $37.0^\circ C$ ($98.6^\circ F$), blood pressure $128/78$ mm Hg, pulse $126$/min, and respirations $32$/min. Pulse oximetry is $91\%$ on a non-rebreather mask. Physical examination reveals a lethargic patient sitting in a tripod position, using accessory muscles of respiration. Auscultation shows notably decreased breath sounds bilaterally with only faint expiratory wheezes. There is no jugular venous distention or lower extremity edema. An arterial blood gas analysis on the current oxygen setting shows:

pH: $7.33$
$PaCO_2$: $46$ mm Hg
$PaO_2$: $64$ mm Hg
$HCO_3^-$: $24$ mEq/L

Continuous fetal heart rate monitoring demonstrates a baseline of 150/min with minimal variability and recurrent late decelerations. Which of the following is the most appropriate next step in management?