T-piece gas flow palpation as a clinical indicator of endotracheal intubation in neonates.

We aimed to determine if providers could detect simulated spontaneous respirations of an intubated neonate by palpating gas flow changes at the positive end expiratory pressure valve of a T-piece resuscitation device in an in vitro setting. We also aimed to demonstrate whether the sensitivity of this methodology was related to the exhaled tidal volumes and/or the gas flow settings on the resuscitation device. A T-piece resuscitator (Neopuff®) circuit was connected to a neonatal silicon test lung. Expiratory tidal volumes of 5, 10 and 15 ml were provided via the test lung, with the Neopuff® set at gas flow rates of 5, 10 and 15 L/min. Physician volunteers were asked to identify whether they could detect expiratory gas from the test lung at the circuit T-piece with the volar surface of their wrist, at different tidal volumes and gas flows. Ten doctors detected 315 of 450 expirations; 95, 73 and 42 % of tidal volumes of 15, 10 and 5 ml, respectively, were detected with an overall positive predictive value of 98.7 %. Detection of exhalations was similar at different gas flow rates for each tidal volume. No exhalations were detected at zero gas flow. We concluded that T-piece gas flow palpation may be a useful and previously unreported clinical sign, which may help to reassure clinicians that they have successfully intubated the trachea. As with any clinical sign, it should not be considered in isolation but within the context of the clinical picture.

A technique for preparing protein gradients on polymeric surfaces: effects on PC12 pheochromocytoma cells.

A technique for preparing micropatterns and gradients of proteins on polymeric substrates has been developed in this work. Peroxides were generated on the substrate surface by UV preirradiation and they initiated graft polymerization of acrylic acid (AA) onto the surface upon a second UV irradiation. Micropatterns and gradients of poly(acrylic acid) (PAA) were formed when the substrate was placed under or moved with respect to a photomask during UV preirradiation. Protein micropatterns and gradients were fabricated on the surface by covalently linking to the carboxyl groups on PAA chains. To test cell response to the protein gradient surfaces, PC12 pheochromocytoma cells were cultured on laminin-bound substrates in serum-free medium supplemented with nerve growth factor (NGF). It is found that both the attachment and neurite outgrowth behaviors of PC12 cells were dependent on the surface laminin density. However, the unreacted carboxyl groups on the polymer surface negatively affected PC12 cells. This weakened the positive influence from laminin.

Influence of carboxyl group density on neuron cell attachment and differentiation behavior: gradient-guided neurite outgrowth.

A UV pre-irradiation step followed by a UV grafting step was used to graft poly(acrylic acid) (PAA) on polymeric substrates. These substrates were then used to investigate the influence of carboxyl groups (-COOH) on cell behavior. Both the attachment and differentiation behaviors of C17.2 cells showed a -COOH group density-dependent response. In order to achieve an even distribution of cells on a -COOH gradient surface for neuron differentiation studies, an Ar plasma post-treatment was applied to the PAA-grafted surfaces. It greatly improved the cell adhesion properties with little damage to -COOH groups. This allows uniform distributions of seeded cells even on substrates with -COOH gradients. A linear or stepped -COOH gradient was found to be capable of serving as a repelling cue to guide the outgrowth of neurites from C17.2 cells. Up to 3.7 times more cells developed neurites growing down the -COOH gradient than growing up it.

Three-dimensional metallized features on polymeric substrates by microcontact printing.

We demonstrate the formation of 3-D metallized features on a polymeric substrate by microcontact printing. A patterned silicon stamp was "inked" with catalytic particles. Thereafter, particles were selectively removed from the raised regions of the stamp. A molten polymer was embossed against the stamp. Upon cooling and separation, the catalytic particles that were within the recessed areas of the stamp were transferred to the polymer. The polymer was then immersed in an electroless plating bath, and metallization occurred selectively on the areas where the catalytic particles were present. We have achieved 3-D metallized columns as small as 500 nm in diameter and about 1 mum tall.