Seal or No Seal

Abstract

To the Editor After tracheal intubation of a patient in whom only the epiglottis could be visualized, the Philips IntelliVue M1019A Gas Analyzer (Philips Electronics N.V., Amsterdam, The Netherlands) reported an absence of CO2. Extubation and reintubation produced similar results. After confirming tracheal intubation using a self-inflating bulb,1 we suspected a broken watertrap. While replacing it, we found that one seal between the watertrap and analyzer had fallen off causing a leak. The seals are placed vertically between the watertrap and gas analyzer (Fig. 1). The seals are small (0.6 × 1.0 cm) and nearly clear, so they are hardly noticeable and furthermore are recessed behind a cover plate making visual inspection impossible. When the watertrap is removed, the seals should be retained by the analyzer prongs. However, the analyzer prongs are smooth and have no barb or fixation method to secure them and we have observed seals simply falling off the prongs while replacing a watertrap. A missing seal allows dilution of monitored gases with room air causing falsely low or absent readings and distorted capnograms.Figure 1: Left, View of left front of Philips IntelliVue Gas Analyzer (M1019A) where the watertrap cartridge inserts into the analyzer, hiding the manifold seals. Right, Watertrap with 1 (0.6 × 1.0 mm) of 2 manifold seals shown.These events were reported to the Food and Drug Administration and to Philips who sent representatives to evaluate the incident. Philips issued a Field Safety Notice on July 14, 2010. The Philips warning reads in part: “Ensure both manifold seals are in place when fitting a new watertrap.” It continues, “In rare cases, one or both of the manifold seals (short silicone tubes) may remain attached to the watertrap when it is removed from the Gas Analyzer. If this occurs, remove the seals from the watertrap and reattach them to the watertrap manifold of the Gas Analyzer.” The characterization of seal detachment as “rare” differs from our experience with 12 gas analyzers in which one seal detaches on average every 3 days (communication from our Clinical Engineering Department). Replacing the silicone seals without using the watertrap as a deployment device is nearly impossible. Seals can fall from the analyzer and not remain attached to the watertrap. Therefore, the absence of seals on the watertrap prongs does not guarantee that seals are retained internally, a situation not anticipated by the language contained in the Field Safety Notice. Watertrap replacement kits contain neither replacement seals nor any alert about the seals. The response from Philips informs users that there are issues with the gas analyzer manifold seals but does not eliminate the latent error condition of the design. Samsun Lampotang, PhD John Bordes, CRNA David Paulus, MD Dietrich Gravenstein, MD Department of Anesthesiology University of Florida College of Medicine Gainesville, Florida [email protected]