Effect of Aminophylline on Diaphragmatic Contractility in the Piglet

Abstract

ABSTRACT. Minute ventilation, arterial blood gases, ar-of arterial oxygen > 8 kPa (60 torr) in room air, and a partial terial pH, cardiac output, and transdiaphragmatic force pressure of the arterial carbon dioxide 5 6.7 kPa (50 torr) were generation, both during spontaneous ventilation and in accepted for study. The animals were anesthetized with an i.v. response to phrenic nerve stiwulation during airway occlu-combination of chloralose (30 mg/kg) and urethane (1 50 mg/ sion at end expiration, were measured in nine anesthetized, kg) and studied in the supine position. Subsequent infusions of tracheostomized piglets before and 30 min after parenteral anesthetic were used if the piglet developed jaw clonus. A tracheinfusion of 20 mg/kg aminophylline. Serum theophylline ostomy was placed and connected to a two-way nonrebreathing levels averaged 109 f 21 ~m o l / L (19.7 f 3.7 ~g / m L ) at valve (model 2384, Hans Rudolph, Inc., Kansas City, MO). 30 min postinfusion. No significant changes were noted in Inspiratory flow was detected by a hot-wire anemometer and pH, blood gases, blood Pressure, or ventilatory measures integrated to provide tidal volume. All animals breathed 50% after aminophylline. Amino~h~lline infusion also had no oxygen-balance nitrogen throughout the study. A femoral artery effect on transdiaphragmatic force generation at any fie-catheter was placed to measure heart rate and blood pressure, quency of phrenic nerve stimulation studied. It is concluded and to obtain samples for blood gas and p~ analysis. Rectal that aminophylline has no effect on diaphragmatic contrac-temperature was continuously monitored and maintained at 39 tility in the quietly breathing, nonfatigued piglet. (Pediatr +. 0 . 5 0~ by a radiant Res 28: 196-198,1990) Force-frequency curves were generated by the transvenous phrenic nerve stimulation technique as previously described (19, Abbreviations 20). The phrenic nerves were stimulated via bilateral indwelling external jugular vein catheter electrodes with supramaximal voltPdi, transdiaphragmatic pressure age at 20, 30, 50, and 100 Hz. Transdiaphragmatic force generation (Pdi) during airway occlusion at end expiration was measured as gastric pressure (Pgas) minus proximal airway pressure (Paw): Pdi = Pgas -Paw (2 1-23). Proximal airway pressure was measured by a PlOEZ (Spectramed, Inc., Oxnard, CA) pressure Amino~h~lline has been shown to increase the lorce Output of transducer connected to an 1 8-gauge needle inserted in the the diaphragm in adult human study subjects and animal models tracheostomy tube between the animal and the nonrebreathing ( 1 -13). This effect has been demonstrated for the nonfatigued valve A thin-walled latex balloon containing 0.5 mL of air was (1 -13) as well as the fatigued diaphragm (l,6, 10-12). The results of these studies have been extrapolated to the treatment of adult connected to a P~~Y~~~Y~~~ catheter (1.65-mm inner diameter) patients with respiratory failure (6). More recently, it has been and placed in the measure gastric pressure with a...

Effects of Theophyllme on Pharyngeal Dilator and Diaphragm Muscle Contractile Properties

“…33], and a third group of studies found an increase in force at low but not high stimulation frequen cies [9, 10, 15. 19], This discrepancy among studies can not be easily explained on the basis of species or méthodo logie differences, although of note is that one study per formed on neonatal diaphragm (piglet) found no im provement in force with aminophylline [33]. The present study was not specifically designed to resolve this contro versy for the diaphragm, but nonetheless suggests that theophylline does not augment the twitch force of the pha ryngeal dilator musculature.…”

Effect of Methylxanthines on Diaphragmatic Fatigue in the Piglet

“…The accuracy of techniques used in this study to determine the pressure-generating capability of the diaphragm have previously been critiqued (18,25). The PdiFC was used to assess Pdi generation.…”