Workflow to develop 3D designed personalized neonatal CPAP masks using iPhone structured light facial scanning

Abstract

Background: Continuous positive airway pressure (CPAP) is a common mode of respiratory support used in neonatal intensive care units. In preterm infants, nasal CPAP (nCPAP) therapy is often delivered via soft, biocompatible nasal mask suitable for long-term direct skin contact and held firmly against the face. Limited sizes of nCPAP mask contribute to mal-fitting related complications and adverse outcomes in this fragile population. We hypothesized that custom-fit nCPAP masks will improve the fit with less skin pressure and strap tension improving efficacy and reducing complications associated with nCPAP therapy in neonates.

Methods: After IRB approval and informed consent, we evaluated several methods to develop 3D facial models to test custom 3D nCPAP masks. These methods included camera-based photogrammetry, laser scanning and structured light scanning using a Bellus3D Face Camera Pro and iPhone X running either Bellus3D FaceApp for iPhone, or Heges application. This data was used to provide accurate 3D neonatal facial models. Using CAD software nCPAP inserts were designed to be placed between proprietary nCPAP mask and the model infant's face. The resulted 3D designed nCPAP mask was form fitted to the model face. Subsequently, nCPAP masks were connected to a ventilator to provide CPAP and calibrated pressure sensors and co-linear tension sensors were placed to measures skin pressure and nCPAP mask strap tension.

Results: Photogrammetry and laser scanning were not suited to the neonatal face. However, structured light scanning techniques produced accurate 3D neonatal facial models. Individualized nCPAP mask inserts manufactured using 3D printed molds and silicon injection were effective at decreasing surface pressure and mask strap pressure in some cases by more than 50% compared to CPAP masks without inserts.

Conclusions: We found that readily available structured light scanning devices such as the iPhone X are a low cost, safe, rapid, and accurate tool to develop accurate models of preterm infant facial topography. Structured light scanning developed 3D nCPAP inserts applied to commercially available CPAP masks significantly reduced skin pressure and strap tension at clinically relevant CPAP pressures when utilized on model neonatal faces. This workflow maybe useful at producing individualized nCPAP masks for neonates reducing complications due to misfit.

Keywords: Neonatal CPAP masks; Structured light scanning; Three-dimensional; iPhone.

Fig. 1

Infants face were scanned with an infrared structured light camera (Bellus 3D™) which projected 50,000 infrared dots onto the face area. Using proprietary (Bellus 3D™) landmark recognition software surface images are created with close range scanning at up tp 0.4 mm resolution

Fig. 2

a) A point cloud created as 500,000 3D surface points recognized by structured infrared light scanning software. b) High density surface face model created with 250,00 high-definition triangles. c) Texture map applied to the surface of high-definition triangles (b) which can be used for direct 3D printing

Fig. 3

Anthropometric landmarks used on camera generated 3D face model to assess accuracy of dimensions determined by scanning

Fig. 4

Part comparison analysis of measurements determined by structed light scanning camera (Bellus) compared to CT scanned surface map. a) The structured light scanning 3D data was superimposed onto the CT scanned image surface and the comparison to the 3D model was assessed by color mapping. b) Color scale representing the difference in mm between each point of the 3D surface with the corresponding CT surface data. Green = 0.0 mm difference. Red = 2.0 mm difference. c) A histogram depicting the number of points that correspond to each color

Fig. 5

9 representative structured facial scan of neonates using Bellus 3D camera and Bellus 3D scanning software

Fig. 6

Using structured light scans of neonatal faces individual CPAP inserts were designed to uniquely conform, to facial topography

Fig. 7

A. Preterm 3D printed neonatal face. Digitally the solid face bodies were use as a digital “cutting tool” to contour the reaward potion of the CPAP insert. B, “Concept design” of nCPAP mask design with 2 parts forward part to mate proprietary nCPAP connection and rear part to conform to the surface topography of each face while providing flat mating surface to forward part. C. Silicon molding process D. Proprietary neonatal CPAP mask (Hamilton infant XL) (left),2- part molded CPAP mask (risk and below)

Fig. 8

3D infant face model and CPAP insert design and fabrication workflow

Fig. 9

Test platform for determining surface pressure between neonatal CPAP mask and model neonatal face and determining minimal strap tension to elicit air leak less than 0.5 L/min. A artificial lung prosthesis. B 3D printed model neonatal face. C Force transducer to measure strap tension. D Adjustable nasal CPAP strap. E Proprietary neonatal CPAP mask. F ventilator tubing. G Pressure transducer to measure surface pressure between neonatal CPAP mask and model neonatal face

Fig. 10

A Infant Model 1. Representative case showing that CPAP mask surface pressures were lesser at each mask position and at each CPAP setting. B Infant Model 1. Representative case showing that CPAP mask strap tensions were lower at each strap position at each CPAP setting