Distance from the glottis to the grille: the LMA Unique, Air-Q and CobraPLA as intubation conduits: a randomised trial.

BACKGROUND: Supraglottic airway devices are often used in airway management to facilitate tracheal intubation. Knowledge of the distance from the grille of the device to the patient's vocal cords is essential for the safe passage of the tracheal tube below the vocal cords. OBJECTIVES: To assess the distance from the glottis to the grille of three supraglottic airway devices [LMA (LMA Unique), Air-Q (Air-Q Intubating Laryngeal Airway Reusable) and CobraPLA (Cobra Perilaryngeal Airway)] and their safe usage as intubation conduits. DESIGN: Randomised controlled trial. SETTING: Tertiary, university hospital. PATIENTS: Thirty women undergoing elective gynaecological surgery with planned supraglottic airway management. INTERVENTIONS: In-vivo fibreoptic assessment and in-vitro measurement. MAIN OUTCOME MEASURES: The distance from the grille to the glottis was defined as primary outcome. The distance from the beginning of the cuff of a tracheal tube passed through the device to the grille was assessed as secondary outcome. RESULTS: The three devices exhibited significant differences in the mean ±â€ŠSD distance from the glottis to the grille (LMA 4.6 ±â€Š1.5  cm, Air-Q 5.7 ±â€Š1.4  cm, CobraPLA 3.4 ±â€Š1.4  cm; P = 0.009). The Air-Q was predicted to allow the safe passage of a tracheal tube into the trachea, whereas the cuff was predicted to rest on the vocal cords in 57% of the LMA patients and 14% of the CobraPLA patients. CONCLUSION: Using the LMA Unique as a conduit for tracheal intubation may pose a safety risk, whereas the use of the Air-Q would position the tracheal tube at a safe depth in the trachea.

Elevated fluid shear stress enhances postocclusive collateral artery growth and gene expression in the pig hind limb.

OBJECTIVE: The role of fluid shear stress (FSS) in collateral vessel growth remains disputed and prospective in vivo experiments to test its morphogenic power are rare. Therefore, we studied the influence of FSS on arteriogenesis in a new model with extremely high levels of collateral flow and FSS in pig and rabbit hind limbs. METHODS AND RESULTS: A side-to-side anastomosis was created between the distal stump of one of the bilaterally occluded femoral arteries with the accompanying vein. This clamps the collateral reentry pressure at venous levels and increases collateral flow, which is directed to a large part into the venous system. This decreases circumferential wall stress and markedly increases FSS. One week after anastomosis, angiographic number and size of collaterals were significantly increased. Maximal collateral flow exceeded by 2.3-fold that obtained in the ligature-only hind limb. Capillary density increased in lower leg muscles. Immunohistochemistry revealed augmented proliferative activity of endothelial and smooth muscle cells. Intercellular adhesion molecule-1 and vascular cell adhesion molecule (VCAM)-1 were upregulated, and monocyte invasion was markedly increased. In 2-dimensional gels, actin-regulating cofilin1 and cofilin2, destrin, and transgelin2 showed the highest degree of differential regulation. CONCLUSIONS: High levels of FSS cause a strong arteriogenic response, reinstate cellular proliferation, stimulate cytoskeletal rearrangement, and normalize maximal conductance. FSS is the initiating molding force in arteriogenesis. The role of fluid shear stress on the development of a collateral circulation was studied by abruptly increasing collateral blood flow by a distal femoral artery-to-vein anastomosis. This increased number and size of collateral vessels to a hitherto unknown degree. Fluid shear stress is the primary and strongest arteriogenic stimulus.