Ultrasound evaluation of piglet diaphragm function before and after fatigue

Kocis, Keith C., Peter J. Radell, Wayne I. Sternberger, JaneE. Benson, Richard J. Traystman, and David G. Nichols. Ultrasound evaluation of piglet diaphragm function before and after fatigue. J. Appl. Physiol. 83(5):1654-1659, 1997.Clinically, a noninvasive measure of diaphragmfunction is needed. The purpose of this study is to determine whetherultrasonography can be used to 1)quantify diaphragm function and 2)identify fatigue in a piglet model. Five piglets were anesthetized withpentobarbital sodium and halothane and studied during the followingconditions: 1) baseline (spontaneous breathing); 2) baseline + CO₂ inhaledCO₂ to increase arterial PCO₂ to 50-60 Torr (6.6-8kPa)]; 3) fatigue + CO₂ (fatigue induced with 30 minof phrenic nerve pacing); and 4)recovery + CO₂ (recovery after 1 hof mechanical ventilation). Ultrasound measurements of the posteriordiaphragm were made (inspiratory mean velocity) in the transverseplane. Images were obtained from the midline, just inferior to thexiphoid process, and perpendicular to the abdomen. M-mode measures weremade of the right posterior hemidiaphragm in the plane just lateral tothe inferior vena cava. Abdominal and esophageal pressures weremeasured and transdiaphragmatic pressure (Pdi) was calculated duringspontaneous (Sp) and paced (Pace) breaths. Arterial blood gases werealso measured. Pdi(Sp) and Pdi(Pace)during baseline + CO₂ were 8 ± 0.7 and 49 ± 11 cmH₂O, respectively, anddecreased to 6 ± 1.0 and 27 ± 7 cmH₂O,respectively, during fatigue + CO₂. Mean inspiratory velocityalso decreased from 13 ± 2 to 8 ± 1 cm/s during theseconditions. All variables returned to baseline during recovery + CO₂. Ultrasonography can beused to quantify diaphragm function and identify piglet diaphragm fatigue.