| [ Summary ] |
We outlined the capnometry which can be used during dialysis. The measurement principles of capnometry are the mass spectrometry and the infrared absorption spectrometry, and the infrared absorption spectrometry is mainly used. Two types of capnometer are available concerning the methods of gas sampling. Side streams capnometer withdraw gas samples continuously through a capillary tube in the patient's airway, leading to the measurement equipment. A water trap removes particles of water before measurement. A disadvantage is that the narrow lumen of the sampling tube may be obstructed with pulmonary secretions or condensate. Mainstream capnometers employ a special breathing-circuit cuvette that is placed directly in the airway. The cuvette houses an infrared light source and photodetector, and is heated to prevent the dew condensation. Because there is no sampling system, this type of capnometer has rapid responses. The major disadvantages are size and weight of the cuvette in the patient's airway, and that it can be used only for patients under tracheal intubation or using a mask (including laryngeal masks). |