Thoracentesis /ˌθɔrəsɨnˈtiːsɨs/, (from Greek, thorax + centesis, puncture) also known as thoracocentesis or pleural tap, is an invasive procedure to remove fluid or air from the pleural space for diagnostic or therapeutic purposes. A cannula, or hollow needle, is carefully introduced into the thorax, generally after administration of local anesthesia. The procedure was first described in 1852.The recommended location varies depending upon the source. Some sources recommend the midaxillary line, in the eighth, ninth, or tenth intercostal space. Whenever possible, the procedure should be performed under ultrasound guidance, which has shown to reduce complications.