Emergency medical services bring a 68-year-old male to the resuscitation bay due to progre… — USMLE Step 2 CK

Emergency medical services bring a 68-year-old male to the resuscitation bay due to progressive, severe difficulty breathing and purulent sputum production over the past 72 hours. He has a 40-pack-year smoking history and advanced chronic obstructive pulmonary disease (COPD). He reports poor oral intake over the last week. At a pulmonary clinic visit two weeks ago, a sputum culture grew *Haemophilus influenzae* susceptible to azithromycin and ceftriaxone.

On arrival, he is in acute respiratory distress, using accessory muscles of respiration. Vital signs are:
- Temperature: $37.8^\circ\text{C}$ ( $100.0^\circ\text{F}$ )
- Blood pressure: $102/65\text{ mmHg}$
- Heart rate: $115/\text{min}$
- Respiratory rate: $30/\text{min}$
- Oxygen saturation: $85\%$ on room air

Physical examination reveals a barrel-shaped chest, prolonged expiratory phase, and diffuse bilateral wheezing. Jugular venous pressure is normal, and there is no peripheral edema. Chest radiograph reveals hyperinflated lungs and a flattened diaphragm without focal infiltrates or cardiomegaly. Arterial blood gas analysis on room air shows:
- pH: $7.20$
- $\text{PaCO}_2$ : $50\text{ mmHg}$
- $\text{PaO}_2$ : $52\text{ mmHg}$
- $\text{HCO}_3^-$ : $19\text{ mEq/L}$

Which of the following are the most appropriate next steps in the management of this patient? (Select all that apply)

Initiate noninvasive positive pressure ventilationAnswer
Provide inhaled albuterol and intravenous methylprednisoloneAnswer
C
Administer a bolus of intravenous furosemide
D
Start intravenous piperacillin-tazobactam
E
Administer an infusion of sodium bicarbonate

Answer

Initiate noninvasive positive pressure ventilation AND Provide inhaled albuterol and intravenous methylprednisolone

This patient is experiencing a severe acute exacerbation of chronic obstructive pulmonary disease (COPD) complicated by acute respiratory failure and a mixed acid-base disorder. The clinical presentation—accessory muscle use, diffuse wheezing, hyperinflated lungs, and absence of volume overload signs—points squarely to COPD rather than acute decompensated heart failure. Initial management of a severe COPD exacerbation includes short-acting bronchodilators (albuterol) and systemic corticosteroids (methylprednisolone) to reduce airway inflammation and resistance. Furthermore, this patient requires noninvasive positive pressure ventilation (NPPV). NPPV is strongly indicated for COPD exacerbations with respiratory acidosis (pH

< 7.35

and

\text{PaCO}_2 > 45\text{ mmHg}

) or severe dyspnea, as it decreases the work of breathing, improves gas exchange, and reduces the need for endotracheal intubation.

Step-by-Step Solution

Evaluate clinical presentation and radiologic findings.

The patient demonstrates severe respiratory distress, wheezing, and hyperinflated lungs without signs of fluid overload.

Accurate clinical assessment differentiates a true COPD exacerbation from acute decompensated heart failure, guiding targeted therapy rather than inappropriate diuresis.

Analyze the arterial blood gas data using Winter's formula.

The expected PaCO2 (

1.5 \times 19 + 8 = 36.5 \pm 2\text{ mmHg}

) is much lower than the actual PaCO2 (

50\text{ mmHg}

), confirming a mixed metabolic and uncompensated respiratory acidosis.

Identifying the uncompensated respiratory failure dictates the urgent need for ventilatory support rather than simply attempting to correct the metabolic acidosis with bicarbonate.

Select appropriate targeted therapies.

NPPV, bronchodilators, and systemic corticosteroids are indicated, while narrow-spectrum antibiotics should be utilized based on prior culture data.

These combined interventions directly address airway inflammation, bronchoconstriction, and ventilatory failure while strictly adhering to antibiotic stewardship principles.

Key Concept

Management of severe COPD exacerbations complicated by acute respiratory failure, and the interpretation of mixed acid-base disorders using Winter's formula.

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