• T Kolobow, N Rossi, K Tsuno, and M Aprigliano.
• Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland.
• Biomed Instrum Technol. 1994 Mar 1; 28 (2): 123-9.

AbstractUsing a new technology, the authors fabricated a series of ultrathin-walled, non-kinking, wire-reinforced polyurethane endotracheal (ET) tubes for use in the newborn, with a wall thickness of 0.2 mm from the smallest to the largest ET tubes (one-stage tubes), as well as two-stage ET tubes, with the tracheal section of smaller diameter than the oropharyngeal section. The wire reinforcement consisted of 0.1-mm x 0.5-mm stainless steel 304 flat wire; to impart crush-proof features, some ET tubes were reinforced with Nitinol (nickel-titanium shape-memory alloy) wire. Circular layers of highly pliable polyurethane film ("gills"), 0.025 mm thick, in series, were then incorporated onto the distal sections of the ET tubes to reduce potential air leakage (no-pressure cuff). In-vitro pressure-flow measurements showed a sixfold-to-ninefold decrease in airflow resistance for the two-stage ET tubes, compared with standard tubes. For example, a two-stage ET tube of the new design with the outside diameter of a standard 2.5-mm ET tube has the airflow resistance of a hypothetical conventional 4.2-mm ET tube, while a straight ET tube with a similar thin wall and the same outside diameter throughout (one-stage ET tube) has the resistance of an imputed 3.2-mm standard ET tube, or a twofold-to-threefold decrease in air flow resistance. When tested in a 4-kg rabbit, the air leak of the 2.5-mm two-stage ET tube with "gills" and the outside diameter of a standard 2.5-mm ET tube was much less than that of a standard 2.5-mm ET tube, and was similar to the air leak found with a 4.0-mm ET tube of conventional design (without cuff). The authors conclude that the new ET tubes have a greatly reduced air flow resistance compared with conventional ET tubes; they provide enhanced sealing from possible air leaks; they are non-kinking and crush-resistant; and they are crush-proof when used with Nitinol wire reinforcement.

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