Theoretical open-loop model of respiratory mechanics in the extremely preterm infant

Non-invasive ventilation is increasingly used for respiratory support in preterm infants, and is associated with a lower risk of chronic lung disease. However, this mode is often not successful in the extremely preterm infant in part due to their markedly increased chest wall compliance that does not provide enough structure against which the forces of inhalation can generate sufficient pressure. To address the continued challenge of studying treatments in this fragile population, we developed a nonlinear lumped-parameter model of respiratory system mechanics of the extremely preterm infant that incorporates nonlinear lung and chest wall compliances and lung volume parameters tuned to this population. In particular we developed a novel empirical representation of progressive volume loss based on compensatory alveolar pressure increase resulting from collapsed alveoli. The model demonstrates increased rate of volume loss related to high chest wall compliance, and simulates laryngeal braking for elevation of end-expiratory lung volume and constant positive airway pressure (CPAP). The model predicts that low chest wall compliance (chest stiffening) in addition to laryngeal braking and CPAP enhance breathing and delay lung volume loss. These results motivate future data collection strategies and investigation into treatments for chest wall stiffening.Comment: 22 pages, 5 figure

Indirect Applications of Additive Manufacturing for Antennas

We report the fabrication methodology of stereolithography (SLA) printed molds for metal and resin cast antennas. In the first method, a conical horn created using metal cast molds printed from a glass-filled resin utilizes a casting technique allowing for low-cost 3D printing to fabricate metal antennas, reducing the losses incurred by metallized plastics, while still producing complex geometries quickly. This metal cast conical horn is compared to a horn constructed using a more traditional 3D printing method. The second casting method demonstrates the interchangeability between creating parts via SLA printing with a glass-filled resin and using the same resin cast into a reusable Polydimethylsiloxane (PDMS) mold. We demonstrate this method by casting an interchangeable slug for a capacitively coupled, mechanically reconfigurable disk loaded monopole. Simulated and experimental data are presented for S textsubscript 11, and Gain. Simulated BW, directivity, gain and efficiency as a function of frequency are presented. The results indicate that the 3D printed metal casting process produces antennas with a higher gain and lower return loss than metallized resin antennas. The method is suitable for difficult geometries requiring resolution of at least $50 \mu \text{m}$ . The capacitively coupled disk loaded monopole demonstrates the versatility of 3D printing in antenna fabrication

Lung, chest wall, and total respiratory system compliance curves for high <i>C</i>_<i>w</i> (left) and low <i>C</i>_<i>w</i> (right).

<p>Curves are described by Eqs <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0198425#pone.0198425.e016" target="_blank">(9)</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0198425#pone.0198425.e017" target="_blank">(10)</a> and parameterized using the procedures described in <b>Parameterization</b>. Tidal breathing loops with normal <i>R</i>_<i>u</i> (grey) and increased <i>R</i>_<i>u</i> (black) are superimposed for each condition over the lung compliance curve and larger in each inset to display hysteresis.</p

Aggregate parameters and output states targeted during simulations.

<p>Aggregate parameters and output states targeted during simulations.</p

Lumped-parameter respiratory mechanics model, in both volume-pressure (panel A) and electrical (panel B) system analogs.

<p>Each non-rigid compartment has a volume <i>V</i> (black), pressure <i>P</i>, (black) and associated compliance <i>C</i> (green, for emphasis) that is a function of the transmural pressures (purple) across the compartment boundaries. Air flows (red) across resistances <i>R</i> and inertance <i>I</i> (blue) are positive in the direction of the arrows. Circular yellow arrows indication direction of loop summations in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0198425#pone.0198425.e009" target="_blank">Eq (3)</a>. Subscripts: airway opening <i>ao</i>, upper <i>u</i>, collapsible <i>c</i>, small peripheral <i>s</i>, alveolar <i>A</i>, viscoelastic <i>ve</i>, lung elastic <i>el</i>, transmural <i>tm</i>, pleural <i>pl</i>, chest wall <i>cw</i>, muscle <i>mus</i>.</p

Breath-to-breath dynamic lung compliance and tidal volume.

<p>Depicted are high and low <i>C</i>_<i>w</i> conditions, with simulated CPAP triggered in the high <i>C</i>_<i>w</i> condition when recruited fraction dropped 10%, 5%, and 3%.</p

Simulated periodic steady-state tracings of five breaths.

<p>Depicted are alveolar volume, airflow, alveolar pressure, dynamic elastic lung recoil, and pleural pressure, under high and low <i>C</i>_<i>w</i> conditions, with normal vs. high <i>R</i>_<i>u</i>.</p

Parameters varying with chest wall compliance and simulation conditions.

<p>Parameters varying with chest wall compliance and simulation conditions.</p

Breath-to-breath volumes.

<p>End-expiratory lung volume (left y-axis) and tidal volume (right y-axis) under high and low <i>C</i>_<i>w</i> conditions, no interventions.</p