Emergency medical services bring a 69-year-old retired teacher to the resuscitation bay du… — USMLE Step 2 CK

Emergency medical services bring a 69-year-old retired teacher to the resuscitation bay due to three days of worsening respiratory distress. She reports an increase in sputum production that has become dark yellow. Her medical history is significant for hypertension, diet-controlled type 2 diabetes, and a 45-pack-year smoking history.

On physical examination, she is alert and cooperative but visibly exhausted, sitting on the edge of the stretcher and leaning forward on her arms. Temperature is $37.4^\circ\text{C}$ ( $99.3^\circ\text{F}$ ), pulse is $112/\text{min}$ , respirations are $28/\text{min}$ , and blood pressure is $155/88\text{ mm Hg}$ . Pulse oximetry shows an oxygen saturation of $85\%$ on room air. Jugular venous pulsation is visible $4\text{ cm}$ above the sternal angle. Chest auscultation reveals a prolonged expiratory phase with diffuse polyphonic wheezes and faint basilar crackles. Mild bilateral pitting edema is present at the ankles.

An electrocardiogram shows sinus tachycardia with right axis deviation and peaked P waves in lead II. A chest radiograph demonstrates hyperinflated lung fields, flattened hemidiaphragms, and enlarged central pulmonary arteries without focal consolidation.

Relevant laboratory results are as follows:

Test	Result
Leukocyte count	$11,500/\text{mm}^3$
B-type natriuretic peptide	$310\text{ pg/mL}$
Arterial blood gas (room air)
pH	$7.27$
$\text{PaCO}_2$	$68\text{ mm Hg}$
$\text{PaO}_2$	$54\text{ mm Hg}$
$\text{HCO}_3^-$	$31\text{ mEq/L}$

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

Initiate noninvasive positive-pressure ventilationAnswer
B
Administer intravenous furosemide
C
Administer intravenous sodium bicarbonate
D
Initiate intravenous piperacillin-tazobactam and vancomycin
E
Administer 100% oxygen via a non-rebreather mask

Answer

Initiate noninvasive positive-pressure ventilation

The correct intervention is noninvasive positive-pressure ventilation (NPPV). This patient presents with a severe acute exacerbation of COPD (AECOPD), complicated by acute-on-chronic respiratory acidosis (pH 7.27, elevated PaCO2, and elevated baseline HCO3). In patients with AECOPD and acute respiratory failure (defined as a pH < 7.35 or PaCO2 > 45 mm Hg), NPPV is the gold-standard first-line therapy. It provides inspiratory positive airway pressure to decrease the work of breathing and expiratory positive airway pressure to keep airways open, dramatically reducing the need for endotracheal intubation and improving mortality. Because she is alert, cooperative, and sitting up, there are no contraindications to a trial of NPPV.

Step-by-Step Solution

Analyze the clinical presentation and physical exam findings.

The patient has a history of smoking, a barrel chest on x-ray, wheezing, and signs of right heart failure (cor pulmonale) such as JVD and pedal edema. This points to an acute exacerbation of chronic obstructive pulmonary disease (AECOPD).

Differentiating between acute decompensated heart failure and AECOPD is critical, as treatments oppose each other.

Interpret the arterial blood gas (ABG) values.

The ABG shows acidemia (pH 7.27) driven by hypercapnia (PaCO2 68 mm Hg). The elevated bicarbonate (31 mEq/L) indicates underlying chronic respiratory acidosis with metabolic compensation. Thus, this is an acute-on-chronic respiratory acidosis.

Identifying ventilatory failure dictates the immediacy and type of respiratory support needed.

Determine the appropriate level of respiratory support.

The patient has an uncompensated respiratory acidosis (pH < 7.35) but remains alert, cooperative, and able to protect her airway. Therefore, noninvasive positive-pressure ventilation (NPPV) is indicated.

NPPV is the gold standard for AECOPD with acute respiratory failure, reducing mortality, intubation rates, and hospital length of stay.

Key Concept

Noninvasive positive-pressure ventilation (NPPV) is the first-line intervention for patients with an acute exacerbation of COPD complicated by acute-on-chronic respiratory acidosis (pH < 7.35 and PaCO2 > 45 mm Hg) provided there are no contraindications (e.g., impaired consciousness, inability to clear secretions).

Estimated Time:1m 30s

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