Semi-automated assessment of transdiaphragmatic pressure variability across motor behaviors

Abstract

We developed and tested a semi-automated algorithm to generate large data sets of ventilatory information (amplitude, premotor drive and timing) across a range of motor behaviors. Adult spontaneously breathing, anesthetized mice (n=27) underwent measurements of transdiaphragmatic pressure (Pdi) during eupnea, hypoxia-hypercapnia, and tracheal occlusion with values ranging from 8±1 to 9±2 to 44±3 cm H2O, respectively. Premotor drive to phrenic motor neurons (estimated by the rate of rise during initial 60 ms) was ~5-fold greater during tracheal occlusion compared to other behaviors. Variability in Pdi amplitude (normalized to spontaneously occurring sighs for each animal) displayed minimal evidence of complex temporal structure or dynamic clustering across the entire period of examination. Using a deterministic model to evaluate predictor variables for Pdi amplitude between successive inspiratory events, there was a large correlation for premotor drive and preceding Pdi amplitude vs. Pdi amplitude (r=0.52). These findings highlight substantial variability in Pdi amplitude that primarily reflects linear components rather than complex, dynamic effects over time.

Compensatory effects following unilateral diaphragm paralysis

“…Respiratory rate, inspiratory duration, and duty cycle were obtained by semi-automated analysis of the Pdi signal for each animal (Medina-Martinez et al, 2015), while the tension-time index was calculated as described in the Materials & Methods.…”

“…Data were exported for post hoc analysis using a custom-designed semi-automated script in MATLAB (MathWorks, Natick, MA). Peak amplitude, both instantaneous and average respiratory rate, inspiratory duration, and duty cycle were determined using previously described techniques (Medina-Martinez et al, 2015). Pdi measurements across all motor behaviors were obtained before, immediately after, and 14 days after unilateral DNV in the DNV group; in the time control group, measurements were made at two time points separated by 14 days.…”

Functional Measurement of Respiratory Muscle Motor Behaviors Using Transdiaphragmatic Pressure

“…Additional parameters of analysis may include amplitude duration, inspiratory time, expiratory time, and estimates of drive (24). Additionally, respiratory frequency and frequency of naturally occurring sighs can be determined during ventilatory behaviors.…”

“…Measurements of Pdi have been conducted in a range species including humans (16, 17), sheep (18), dogs (19), cats (11), piglets (20, 21), rabbits (22, 23), hamsters (12, 13), rats (2, 6, 3) and mice (14, 15, 24). The current position statement of the American Thoracic and the European Respiratory Societies outlines the accepted use of Pdi (25), with the most traditional methodology involving a dual balloon catheter system, with balloons spanning the diaphragm muscle in the thoracic and abdominal cavity.…”

“…The current position statement of the American Thoracic and the European Respiratory Societies outlines the accepted use of Pdi (25), with the most traditional methodology involving a dual balloon catheter system, with balloons spanning the diaphragm muscle in the thoracic and abdominal cavity. This methodology has been adapted for use with solid-state pressure transducers, which has proven especially useful in smaller animals such as mice (14, 15, 24). …”