PREOPERATIVE OXIMETRY AND CAPNOMETRY - POTENTIAL RESPIRATORY SCREENING TOOLS

The growing number of patients admitted for outpatient surgery or for Same-day admission makes it difficult to obtain thorough pulmonary eva luation. We wanted to evaluate the applicability of pre-operative puls e oximetry and capnography as possible pulmonary screening tools. In t his preliminary study, 200 unselected, unmedicated adult patients who were being admitted for surgery were connected to a dual parameter pat ient monitor (Capnomac Ultima(TM), Datex). A standard adult clip-on fi nger probe was used for pulse oximetric oxygen saturation. Sidestream capnometry documented the end-tidal carbon dioxide and the capnogram w hich was recorded for further analysis. In these unmedicated patients, the oxygen saturation ranged from 91 to 99% and was found to be 94% o r less in five percent (N = 10) of the cases. The end-tidal carbon dio xide ranged from 21 to 48 mmHg. In five percent of the cases (N = 10) it was found to be 45 mmHg or higher, reflecting elevated arterial CO2 . When the shape of the capnogram was rated, it was found normal in 54 % of the cases. Slow rising capnogram, indicating mild (N = 84)or mode rate (N = 8)airway obstruction was detected in 42% or 4% of the cases respectively. Since pulse oximeter and end-tidal carbon dioxide values are often not measured until after sedation or after induction of ane sthesia, patients with pre-operative abnormalities might escape pre-op erative detection. In unmedicated patients, routine pre-operative or p re-admission determination of oxygen saturation, end-tidal carbon diox ide and the capnogram may be a valuable screening tool.