Question

A 68-year-old woman is brought to the emergency department by emergency medical services for severe, worsening shortness of breath over the last 24 hours. She has a history of ischemic cardiomyopathy with an ejection fraction of $30\%$, chronic obstructive pulmonary disease (COPD), and chronic kidney disease. Upon arrival, she is lethargic and confused. Her son is at the bedside and demands that she receive "only breathing treatments and no life support," despite the patient having a recently updated, legally valid advance directive explicitly requesting full interventions, including intubation and cardiopulmonary resuscitation, for acute reversible conditions.

Her temperature is $37.1^\circ\text{C}$ ($98.8^\circ\text{F}$), blood pressure is $76/48$ mmHg, heart rate is $128$/min and irregular, and respiratory rate is $32$/min. Oxygen saturation is $82\%$ on room air.

Physical examination reveals jugular venous distention up to the angle of the mandible. Lung auscultation demonstrates diffuse bilateral expiratory wheezing with a significantly prolonged expiratory phase; no crackles are present. Heart sounds are rapid and irregular. The extremities are cold, clammy, and display mottled skin up to the knees.

An electrocardiogram shows atrial fibrillation with a rapid ventricular response.

Arterial blood gas analysis on room air reveals:
pH: $7.15$
$PaO_2$: $52$ mmHg
$PaCO_2$: $68$ mmHg
$HCO_3^-$: $23$ mEq/L
Lactate: $5.4$ mmol/L

Which of the following is the most appropriate initial step in the management of this patient?