The present invention relates to a percutaneous aspiration lung biopsy needle assembly for safe extraction of biopsy tissue and/or fluids from the lungs. Percutaneous needle lung biopsy or transthoracic needle lung biopsy involves the use of a needle to enter the lung through the skin to obtain a biopsy sample. Such a procedure has many risks. These risks may be so great that invasive surgical procedures such as open lung biopsy may be preferred in certain instances. This is so, for example, if the lung biopsy needle is punched into a blood vessel, since uncontrollable bleeding may occur. The degree of bleeding largely depends on the size and shape of the lung biopsy needle which is used. In general, the larger the diameter of the needle, the greater the chance of uncontrollable bleeding. With regard to the shape of the needle tip, a bevelled shape is known to produce fewer bleeding problems than a flat tipped or a standard tapered needle tip.
A second risk of percutaneous lung biopsy is pneumothorax, i.e., lung collapse. When percutaneous biopsy is performed, since the lung itself is punctured, air may leak from the lung and accumulate between the lung surface and the chest cage. If this condition becomes severe the patient may require a chest tube to drain the air from the chest cavity, and the condition may sometimes be fatal.
Pneumothorax results from a number of factors. Theoretically, if the lung is punctured by a needle it might be expected that leakage from the lung would occur. Experimental evidence shows, however, that even larger holes in the lung (for example holes produced by biopsy with forceps) seal off quite rapidly as a result of blood or other secretion near the hole. Experience further shows that the use of larger needles for lung biopsy results in about a 25 percent occurrence of pneumothorax. This apparently conflicting data indicates that pneumothorax may not be caused by the larger hole created by the larger needle, rather it is because when a larger needle is used, the rigidity of the needle against the lung tissue may result in tearing or stretching of the tissue at the point of entry, such that leakage may occur while the needle is in place.
While bleeding and pneumothorax are risks involved where a larger relatively stiff needle and/or flat-tipped needles are used, the use of a smaller diameter needle, such as a 22 gauge needle having a bevelled tip, is also undesirable because the sample obtained using such a smaller needle may be insufficient for histological examination rather than cytological examination. Histological examination is preferred, however, since certain diseases may not be diagnosed cytologically. Historically, the sample size required for histological examination has required open lung biopsy.
At best, then, needles currently used for percutaneous lung biopsy must strike a balance between flexibility and stiffness (as determined by needle diameter) to minimize the chance of lung collapse and improve the sample size, and also balance between the use of sharp bevelled needle tips and dull tips in order to maximize the ability to pierce the skin and other tissue, but minimize chance of uncontrollable bleeding.
A third danger of percutaneous lung biopsy is air embolism. This happens when the needle enters a vessel in the lung and when the stylet is removed to apply negative suction. Air sucked into the vessel in this manner may markedly decrease the pressure in the vessel. When air gets into the vessel it travels to vital organs and blocks the blood supply and the patient can expire.
A further problem encountered during lung biopsy procedures arises in the manipulation of the needle assembly itself. In order to locate the target tissue x-ray fluoroscopy is generally used. Thus, to avoid exposure of the physician's hand to x-radiation during the procedure, the needle will generally be inserted to the approximate location desired with the fluoroscope system off. The physician's hand is then removed from the needle which is, of course, positioned between the x-ray source and the sampling site. The fluoroscope system is then turned on so that the physician may determine the position of the needle relative to the sampling site. The physician then again removes his or her hand and the needle position is determined again. This procedure is repeated until the desired sample is obtained.
Thus, it would be desirable to obtain lung biopsy samples in a manner which would allow continuous fluoroscopy without exposing the physician's hand to x-radiation, and thus speed the procedure.