Breath-by-breath lung gas volume detection using GASMAS in a neonatal mannequin

UNLABELLED: Monitoring lung gas volumes of ventilated infants is important. Gas in Scattering Media Absorption Spectroscopy (GASMAS) can estimate gas volume inside tissues by measuring oxygen absorption. We hypothesized that GASMAS can detect different tidal volumes (TV) delivered to mechanically ventilated lungs in a neonatal mannequin model breath-by-breath.

METHODS: A neonatal mannequin was ventilated with a set range of TVs (2-6 ml), different inspired fractional oxygen (FiO2) (0.21 and 1.00), and respiratory rate settings (10-60 breaths per minute), and GASMAS measurements were acquired.

RESULTS: For both FiO2 levels, the mean O2 projected concentration (PC) was significantly higher during inspiration compared to expiration for all TV values (p < 0.05). However, the difference in mean O2 PC between the inspiration and expiration phases depended on the TV (p < 0.001 for phase*TV interaction). The differences between the inspiration and expiration phases increased progressively with rising TV values. The oxygen absorption difference between inspiration and expiration differed by respiratory rate (p < 0.001).

CONCLUSION: GASMAS detects the difference between inspiration, expiration, and tidal volume gas changes, suggesting a potential clinical application of GASMAS for respiratory monitoring of ventilated neonates.

IMPACT: What is the key message of your article? An experimental study demonstrating the feasibility of the GASMAS technique for detecting changes in lung gas volume. What does it add to the existing literature? GASMAS detects the difference between inspiratory and expiratory breath phases, various tidal volumes, oxygen concentration, and respiratory rate. What is the impact? This suggests a potential clinical application of GASMAS for respiratory monitoring of neonates.