The most likely cause of this patient's respiratory failure is hypophosphatemia, which occurs in patients with chronic alcohol use, malnutrition, or critical illness. Symptoms rarely occur unless the serum phosphate concentration is <2.0 mg/dL (0.65 mmol/L); severe symptoms occur with a serum phosphate concentration <1.0 mg/dL (0.32 mmol/L). Symptoms include weakness, myalgia, rhabdomyolysis, arrhythmias, heart failure, respiratory failure, seizures, coma, and hemolysis. This patient has chronic alcoholism with moderate hypophosphatemia on presentation. Factors that contribute to hypophosphatemia in the patient with chronic alcohol use include decreased dietary intake of phosphate and vitamin D, chronic diarrhea, and a direct toxic effect of alcohol on the proximal tubule. Intravenous dextrose-containing fluids can exacerbate the hypophosphatemia by causing a refeeding syndrome. Glucose stimulates insulin release, which promotes phosphate uptake by the cells and worsening hypophosphatemia. Severe hypophosphatemia can cause respiratory failure from impaired diaphragmatic contractility.

In general, total calcium declines by 0.8 mg/dL (0.2 mmol/L) for each 1.0 g/dL (10 g/L) decrement in serum albumin concentration. This patient's calcium correction for hypoalbuminemia is 8.8 mg/dL (2.2 mmol/L), which is not low and does not explain the respiratory failure.

This patient has mild hypokalemia. Although severe hypokalemia can cause profound muscle weakness, it is unlikely that his serum potassium would decrease to such critically low levels to cause paralysis based on his current treatment.

The patient's magnesium level is within the lower limits of normal range and unlikely to be the cause of his respiratory failure.

Although the patient does have hyponatremia, it is not severe and would not result in respiratory failure. Symptoms of acute hyponatremia are caused by cerebral edema and usually do not manifest until the sodium concentration is lower than 125 mEq/L (125 mmol/L).