Thoracoabdominal Asynchrony Is Not Associated with Oxyhemoglobin Saturation in Recovering Premature Infants

Background: Recovering premature infants are at risk for hypoxemia and lack of synchrony between their rib cage and abdomen due to airflow obstruction and poor respiratory compliance. Thoracoabdominal asynchrony (TAA) is a useful marker of resistive and elastic lung properties. Whether TAA predicts oxygenation is unknown. Objectives: We investigated oxyhemoglobin saturation (SpO 2 %) and TAA (phase angle, φ) in preterm infants with/without high-humidity nasal cannula (HHNC). Methods: A cross-sectional observational study was conducted in 92 infants at 32 weeks' postmenstrual age. We measured SpO 2 % with pulse oximetry and TAA with φ via respiratory inductance plethysmography in infants (mean gestational age: 26.4 + 1.3 weeks) who required room air (n = 18) or HHNC with/without supplemental oxygen (1-5 liters per minute, FiO 2 0.21-0.33, n = 74). We calculated median SpO 2 % from 24.7 + 10.0 min of quiet sleep and median φ from up to 60 breaths. Results: Infants breathing room air alone had marked TAA (φ = 83.6 + 32.9°, range: 10.9-148.5) as did those receiving varying degrees of ventilatory and oxygen support via HHNC (range of group means, φ = 47.0-90.0°). Infants breathing room air had statically greater median SpO 2 % than those receiving support (96.3 + 0.6% vs. 91.3 + 0.6%; ANOVA p = 0.001). SpO 2 % was not associated with TAA in either group (r 2 = 0.09). Conclusion: Recovering premature infants exhibited TAA regardless of need for ventilatory support and supplemental oxygen. TAA was not associated with SpO 2 % in either group. Maintenance of SpO 2 % does not require correction of TAA.