Overinflation of the cuff and pressure on the neck reduce the preventive effect of supraglottic airways on pulmonary aspiration: an experimental study in human cadavers.

BACKGROUND: The oesophageal leak pressure is defined as the pressure which breaks the seal between the cuff of a supraglottic airway and the peri-cuff mucosa, allowing penetration of fluid into the pharynx and the oral cavity. As a consequence, a decrease in this variable increases the risk of reflux and can lead to pulmonary aspiration. The aim of this study was to analyse the effects of cuff overinflation and pressure on the neck on the oesophageal leak pressure of seven supraglottic airways. METHODS: Three laryngeal masks, two laryngeal tubes, and two oesophageal-tracheal tubes were tested in an experimental setting. In five human cadavers, we simulated a sudden increase in oesophageal pressure. To measure baseline values (control), we used an intracuff pressure as recommended by the manufacturer. The first intervention included overinflation of the cuff by applying twice the amount of pressure recommended. A second intervention was defined as external pressure on the neck. RESULTS: The oesophageal leak pressure was decreased for laryngeal masks (control, 28 cm H2O; overinflation, 9 cm H2O; pressure on the neck, 8 cm H2O; P<0.01) and for laryngeal tubes (control, 68 cm H2O; overinflation, 37 cm H2O; pressure on the neck, 39 cm H2O; P<0.01) and was unaffected for oesophageal-tracheal tubes (control, 126 cm H2O; overinflation/pressure on the neck, 130 cm H2O; n.s.). CONCLUSION: Cuff overinflation and pressure on the neck can enhance the risk of gastro-oesophageal reflux when using supraglottic airways. Therefore, both manoeuvres should be avoided in clinical practice.

Pyrimidine-2,4,6-Triones: a new effective and selective class of matrix metalloproteinase inhibitors.

Matrix metalloproteinases (MMPs) are a family of zinc endopeptidases that have been implicated in various disease processes. Different classes of MMP inhibitors, including hydroxamic acids, phosphinic acids and thiols, have been previously described. Most of these mimic peptides and most likely bind in a similar way to the corresponding peptide substrates. Here we describe pyrimidine-triones as a completely new class of metalloprotease inhibitors. While the pyrimidine-trione template is used as the zinc-chelating moiety, the substituents have been optimized to yield inhibitors comparable in their inhibition efficiency of matrix metalloproteinases to hydroxamic acid derivatives such as batimastat. However, they are much more specific for a small subgroup of MMPs, namely the gelatinases (MMP-2 and MMP-9).