A 66-year-old man hospitalized 3 days ago for left lower lobe pneumonia is evaluated for persistent fever. He has been receiving the appropriate intravenous antibiotics as determined by antibiotic susceptibility testing of his sputum cultures. The patient has a history of diabetes mellitus and hypertension. His temperature is 38 C (100.4 F) and pulse is 87/min. Examination shows dullness to percussion and decreased breath sounds over the left lower lung. Imaging studies reveal a loculated, left-sided pleural effusion. A tube is placed to drain the fluid via an incision at the 5th intercostal space in the midaxillary line. Which of the following muscles is most likely to be dissected during the procedure?

Question

A 66-year-old man hospitalized 3 days ago for left lower lobe pneumonia is evaluated for persistent fever.  He has been receiving the appropriate intravenous antibiotics as determined by antibiotic susceptibility testing of his sputum cultures.  The patient has a history of diabetes mellitus and hypertension.  His temperature is 38 C (100.4 F) and pulse is 87/min.  Examination shows dullness to percussion and decreased breath sounds over the left lower lung.  Imaging studies reveal a loculated, left-sided pleural effusion.  A tube is placed to drain the fluid via an incision at the 5th intercostal space in the midaxillary line.  Which of the following muscles is most likely to be dissected during the procedure?

Quizplus · Accepted Answer

11ec160b_35dc_6486_9249_6b58dd398298_MD0001_00 This patient most likely has empyema requiring drainage with a chest tube. The technique involves placing the chest tube through the skin and subcutaneous fat into the 4th or 5th intercostal space in the anterior axillary or midaxillary line. The tube traverses through the serratus anterior muscle, intercostal (external, internal, innermost) muscles, and parietal pleura to reach the pleural cavity. The serratus anterior originates as multiple branches from the side of the chest along the 1st-8th ribs and inserts along the entire length of the medial scapular border. The muscle is divided into 3 parts (superior, intermediate, inferior) depending on the insertion site at the scapula. The inferior part of the muscle facilitates arm elevation by pulling the lower end of the scapula forward (scapular rotation). All 3 muscle parts can help with respiration by lifting the ribs when the shoulder girdle is fixed. (Choice A) The external oblique originates from the lateral ribs (5-12) and extends anteriorly across the abdomen to insert into the linea alba, pubis, and iliac crest of the hip bones. The muscle is usually inferior to the chest tube insertion site. (Choice B) The infraspinatus is a rotator cuff muscle that attaches medially to the infraspinous fossa of the scapula and laterally to the greater tubercle of the humerus. The muscle stabilizes the shoulder joint in addition to externally rotating the humerus. (Choice C) The latissimus dorsi is a back muscle that helps with multiple shoulder movements (eg, extension, adduction). It originates from the spinous processes of T7-L5, the 9th-12th ribs, and the inferior angle of the scapula. The muscle inserts into the humerus and is located posterior to the chest tube insertion site. (Choice D) The pectoralis major arises from the anterior clavicle, sternum, costal cartilages, and aponeurosis of the external oblique muscle. It attaches on the lateral lip of the bicipital groove of the humerus and serves to adduct and internally rotate the humerus. The muscle is anterior to the chest tube insertion site. Educational objective: A chest tube for drainage of pleural effusion is placed through the skin and subcutaneous fat into the 4th or 5th intercostal space in the anterior axillary or midaxillary line. The tube traverses through the serratus anterior muscle, intercostal muscles, and parietal pleura.

A 66-Year-Old Man Hospitalized 3 Days Ago for Left Lower