RT Journal Article SR Electronic T1 Suction catheter size: an assessment and comparison of three different calculation methods JF Respiratory Care FD American Association for Respiratory Care SP respcare.02168 DO 10.4187/respcare.02168 A1 Chris Russian A1 Joshua F. Gonzales A1 Nicholas R. Henry YR 2013 UL http://rc.rcjournal.com/content/early/2013/06/18/respcare.02168.abstract AB Background: Current AARC clinical practice guidelines (CPGs) recommend a suction catheter to endotracheal tube (SC:ETT) ratio based on a comparison between the external diameter of the suction catheter and the internal diameter (ID) of the ETT. A SC:ETT ratio of less than 50% is consistent with the current recommendation. We theorized that a more satisfactory assessment of SC:ETT ratio could be accomplished using volume or area formulas and expansion of diameter recommendations. Some respiratory care texts recommend a SC:ETT ratio that exceeds the CPG standard. Methods: This research project was granted exemption status by the institutional review board at Texas State University-San Marcos. The project involved calculating the internal volume and area of a variety of ETT sizes, calculating the external volume and area of a variety of SC sizes and comparing the ETT and SC calculations to achieve a final ratio. In addition, we assessed negative pressures using vacuum suction and a lung model during multiple suction maneuvers. Results: Our results indicate volume and area calculations provide an alternative method to determining SC:ETT ratio. We found that a volume or area ratio of 50% corresponds to a diameter ratio of 70%. We demonstrated that negative pressures during suctioning remain low at the new ratios. This indicates that use of a larger suction catheter than current clinical practice guidelines is possible while continuing to allow air entrainment between the suction catheter and endotracheal tube. Conclusion: Our investigation determined the ETT internal volume and area, SC external volume and area and SC:ETT ratios based on volume, area and diameter for a variety of ETTs and SCs. Our results support an alternative ratio when pairing suction catheters and endotracheal tubes.