Bolton’s methods: One of several interspaces between the medial clavicular and anterior axillary lines in the lower costal margins. A monopolar needle is inserted just above the costal margin at a right angle to the chest wall. As the needle advances, recordings can be made through the muscles of the chest wall (e.g., external oblique or rectus abdominus, external and internal costal muscles) and then finally, the diaphragm.

Saadeh et al.:² The needle is inserted at the point where the paramidclavicular line (the line drawn halfway between the jugular notch of the sternum and the lateral border of the clavicle) intersects the lower costal margin at the ninth rib cartilage. The needle slowly advances through the skin and abdominal muscle, closely hugging the posterior aspect of the chest wall, while the examiner’s free hand depresses the abdominal wall. A 50-millimeter-long monopolar needle is recommended.