Anesthesiology
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The authors have defined the margin of safety in positioning a double-lumen tube as the length of tracheobronchial tree over which it may be moved or positioned without obstructing a conducting airway. The purpose of this study was to measure the margin of safety in positioning three modern double-lumen tubes (Mallinkrodt [Broncho-Cath], Rusch [Endobronchial tubes], and Sheridan [Broncho-Trach]). The margin of safety in positioning a: 1) left-sided double-lumen tube (all manufacturers) is the length of the left mainstem bronchus minus the length from the proximal margin of the left cuff to left lumen tip; 2) Mallinkrodt right-sided double-lumen tube is the length of the right mainstem bronchus minus the length of the right cuff; and 3) Rusch right-sided double-lumen tube is the length of the right upper lobe ventilation slot minus the diameter of the right upper lobe. ⋯ The average margin of safety in positioning left-sided double-lumen tubes ranged 16-19 mm for the different manufacturers. The average margin of safety in positioning Mallinkrodt right-sided double-lumen tubes was 8 mm, and the margin of safety in positioning Rusch right-sided double-lumen tubes ranged 1-4 mm, depending on French size. The authors concluded that left-sided double-lumen tubes are much preferable to right-sided double-lumen tubes because they have a much greater positioning margin of safety, and that proper confirmation of proper position of either a left- or right-sided double-lumen tube should be aided by fiberoptic bronchoscopy, because the absolute distances that constitute the margin of safety are extremely small.
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Oxygen saturation, SpO2%, was recorded during rapidly induced 42.5 +/- 7.2-s plateaus of profound hypoxia at 40-70% saturation by 1 or 2 pulse oximeters from each of six manufacturers (NE = Nellcor N100, OH = Ohmeda 3700, NO = Novametrix 500 versions 2.2 and 3.3 (revised instrumentation), CR = Criticare CSI 501 + version .27 and version .28 in 501 & 502 (revised instrumentation), PC = PhysioControl Lifestat 1600, and MQ = Marquest/Minolta PulseOx 7). Usually, one probe of each pair was mounted on the ear, the other on a finger. Semi-recumbent, healthy, normotensive, non-smoking caucasian or asian volunteers (age range 18-64 yr) performed the test six to seven times each. ⋯ The mean and SD errors of pulse oximeters (vs. HbO2%) were: (table; see text) The plateaus were always long enough to permit instruments to demonstrate a plateau with ear probes, but finger probes sometimes failed to provide plateaus in subjects with peripheral vasoconstriction. Nonetheless, SpO2 read significantly too low with finger probes at 55% mean SaO2.(ABSTRACT TRUNCATED AT 250 WORDS)