A 56 yo woman comes to the physician because of a 6 mo history of difficulty swallowing foods. Initially, only solid food was a problem, but liquids have become more difficult to swallow over the last 2 months. She also reports occasional regurgitation of food when she lies down. The patient is an avid birdwatcher and returned from a trip to from the beautiful Amazon rainforest of Colombia 3 months ago. She has had a 8 lb weight loss over the past 6 mo. She has not had abdominal pain, blood in stools, or fever. She has smoked a pack of cigarettes daily for 25 years.

The examination shows no abnormalities. Her hemoglobin concentration is 12.2 g/dL. A barium esophagram showed narrowing at the distal esophagus. Esophageal manometry monitoring shows the lower esophageal sphincter failing to relax during swallowing. Which of the following is the next best step in management?

A 43 yo man is brought to the ED with severe retrosternal pain radiating to back and shoulder for 4 hrs. The pain began after attending a farewell party for his coworker at a local bar. He had 3-4 episodes of nonbilious vomiting before the onset of pain. He has HTN. His father died of cardiac arrest at the age of 55 yo. He has smoked one pack of cigarettes daily for the last 23 years and drinks 2-3 beers daily. His current medications include amlodipine and valsartan. He appears pale.

Vitals: Temp 96.8˚F, P 115, BP 90/60

There are decreased breath sounds over the left base and crepitus is palpable over the thorax. Abdominal examination shows tenderness to palpation in the epigastric region; bowel sounds are normal. Laboratory studies show no abnormalities except mild hypokalemia/chloremia and slightly elevated bicarbonate. Which of is the most appropriate test to confirm the diagnosis of this patient?