title: Continuous low-flow supracarinal and subcarinal oxygen insufflation in addition to intermittent positive-pressure ventilation does not improve gas exchange.
abstract: Recent studies in animals have demonstrated that continuous insufflation of oxygen near the tracheal carina results in ventilation and carbon dioxide removal that is proportional to the flow rate. The purpose of this study was to determine whether the addition of supracarinal and subcarinal low-flow oxygen insufflation to conventional intermittent positive-pressure ventilation (IPPV) of critically ill and anesthetized patients results in increased ventilation and improved oxygenation. In eight studies a supracarinal catheter (3.7 mm OD) was placed 1 to 2 cm above the carina, and in another eight studies two subcarinal catheters (1.7 mm OD) were placed 2 cm below the tracheal carina under direct vision with a fiberoptic bronchoscope. Both supracarinal and subcarinal catheters were passed within the lumen of an 8 mm ID endotracheal tube. In both groups, conventional IPPV consisted of a tidal volume of 10-12 mL/kg, respiratory rate of 8 to 10 breaths/min, 0 cm H2O positive end-expiratory pressure (PEEP), and F1O2 of 1.0. In both groups, continuous oxygen insufflation flow rates were 0.05, 0.10, and 0.20 L/ kg/min. It was found that compared with control conditions (no insufflation), oxygen insufflation at all flow rates in both supracarinal and subcarinal insufflation groups did not cause any significant change in either oxygenation or ventilation. There was a significant increase in proximal peak airway pressure with each incremental increase in continuous oxygen flow rate. Conversely, there was a significant decrease in mean arterial pressure and cardiac output with each incremental increase in continuous oxygen flow rate. It is concluded that use of continuous low-flow insufflation of oxygen with simple administration systems (catheters within the lumen of endotracheal tube) in addition to conventional IPPV is contraindicated at the present time. Further studies using different insufflation systems may prove to be worthwhile.
authors.affiliation: Department of Anesthesiology, University of California, San Diego, School of Medicine, La Jolla, CA 92093, USA.
authors.forename: J
authors.initials: J
authors.lastname: Parker
authors.forename: J L
authors.initials: JL
authors.lastname: Benumof
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002245:Carbon Dioxide / Q000097:blood; D005260:Female; D006801:Humans; D007385:Intermittent Positive-Pressure Ventilation; D008297:Male; D008875:Middle Aged; D010102:Oxygen Inhalation Therapy / Q000379:methods*; D011659:Pulmonary Gas Exchange
chemical_list: D002245:Carbon Dioxide