Pulmonary mechanics measurements by respiratory inductive plethysmography and esophageal manometry: Methodology for infants on non-invasive respiratory support

Abstract

BACKGROUND:

Infants are commonly supported with non-invasive ventilation (NIV) such as nasal CPAP and high flow nasal cannula (HFNC). These modes utilize a nasal/oral interface precluding use of a traditional airway flow sensor, such as a pneumotachometer (PNT), needed for pulmonary mechanics (PM) measurements. Respiratory Inductive Plethysmography (RIP), when properly calibrated, records tidal volume non-invasively from chest wall movements. Our aim was to integrate RIP into an existing neonatal pulmonary function testing system to measure PM in infants on NIV and to compare measurements of dynamic lung compliance (C_L) and resistance (R_L) using RIP with those obtained using a PNT.

DESIGN/METHODS:

RIP ribcage (RC) and abdominal (ABD) signals were recorded simultaneously with the flow signal from a PNT; transpulmonary pressure was estimated using an esophageal catheter. Two calibration algorithms were applied to obtain RC and ABD scaling factors.

RESULTS:

Forty PM measurements were performed on 25 infants (GA 31.5±2.9 weeks; birth weight 1598±510 g; median age 7 days). Correlation coefficients for RIP- vs. PNT-based PM were r² = 0.987 for C_L and r² = 0.997 for R_L. From Bland-Altman analysis, the mean bias (±95% CI) between RIP and PNT methods was –0.004±0.021 ml/cmH₂O/kg for C_L and 0.7±2.9 cmH₂O/(L/sec) for R_L. The upper, lower limits of agreement (±95% CI) were 0.128±0.037, –0.135±0.037 ml/cmH₂O/kg for C_L and 18.6±5.1, –17.2±5.1 cmH₂O/(L/sec) for R_L.

CONCLUSION:

Properly calibrated RIP may be a useful tool with sufficient diagnostic accuracy for PM measurements without need for a nasal/oral airflow sensor in infants receiving NIV.