Letters To The Editor: Letters & Announcements
To The Editor:
We have previously described a “soap bubble” drain tube (DT) test utilizing children’s bubble solution to create a soap membrane on the DT port (1). This method is a useful aid when learning to use the ProSeal™ laryngeal mask airway (PLMA) and is also a valuable technique for routinely monitoring safe PLMA usage. The bubble test can verify that there is zero leak at the PLMA/esophageal seal (1), confirm PLMA location behind the cricoid cartilage (2), detect negative DT pressure and aerophagia with spontaneous ventilation (3), and diagnose potentially dangerous esophageal insufflation during positive pressure ventilation (4).
Our original demonstration of the bubble DT test utilized the tennis-racket shaped wand that is supplied within the bottle (1). This method is not optimal because repeated use of the same tennis-racket device with different patients is not aseptic. We now use a simple method shown in Figure 1. A small amount of bubble solution is dispensed into a small cap. The anesthesiologist puts on a new examining glove and wets a fingertip with the solution in the cap. Simply touching the DT port with this fingertip quickly creates a membrane.
Use of the fingertip application method allows the anesthesiologist to easily perform DT tests on multiple occasions during a single anesthetic. It is a very neat method (no dripping) and it is aseptic. It is easily performed when signing a case over to a colleague, for confirming PLMA position (2) and verifying zero DT leak with positive pressure ventilation (1). Finally, this is a simple way to perform the bubble test if it is used as part of a research protocol.
The bubble method is a logical extension from the DT tests that have been previously published (5–7). The PLMA instruction manual recommends placing 1–2 mL of gel within the DT (5). Drs. Brain, Verghese, and Strube recommend placing 0.5–1 mL within the DT (6). Drs. Brimacombe, Keller and Berry recommend observing the gel meniscus (7). The bubble DT test can be considered an infinitesimally thin version of these published methods.
Cornelius J. O’Connor Jr.,, MD
Michael S. Stix, MD, PhD
1. O’Connor CJ Jr., Davies SR, Stix MS. “Soap bubbles” and “gauze thread” drain tube tests. Anesth Analg 2001; 93: 1082.
2. O’Connor CJ Jr, Borromeo CJ, Stix MS. Assessing ProSeal laryngeal mask positioning: the suprasternal notch test. Anesth Analg, In Press.
3. Stix MS, Rodriguez-Sallaberry FE, et al. Esophageal aspiration of air through the drain tube of the ProSeal laryngeal mask. Anesth Analg, In Press.
4. Stix MS, Borromeo CJ, O’Connor CJ Jr. Esophageal insufflation with normal fiberoptic positioning of the ProSeal laryngeal mask airway. Anesth Analg 2001; 93: 1354–7.
5. LMA-ProSeal™ Instruction Manual. San Diego: LMA North America, 2000.
6. Brain AIJ, Verghese C, Strube PJ. The LMA “ProSeal”–a laryngeal mask with an oesophageal vent. Br J Anaesth 2000; 84: 650–4.
7. Brimacombe J, Keller C, Berry A. Gastric insufflation with the proseal laryngeal mask. Anesth Analg 2001; 92: 1614–5.