Response to Resistive Loading in the Newborn Piglet

Mayock, Dennis E.; Badura, Richard J; Watchko, Jon F.; Standaert, T. A.; Woodrum, D. E.

doi:10.1203/00006450-198702000-00003

Cited by 20 publications

(16 citation statements)

References 24 publications

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“…40 A number of studies suggest that preterm infants tolerate respiratory loads poorly and are at higher risk for respiratory failure when compared with older infants and children. 5,30,31 This was thought to be because of the relative lack of highly oxidative, fatigue resistant type I fibers, in the neonatal diaphragm. 11 In animal models and humans, diaphragm myofiber composition changes significantly during postnatal development.…”

Section: Discussionmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9] There is hypertrophy of myofibers and changes in myofiber type and density that start during late gestation and continue for a variable period after birth. 5,9,10 Similar changes may occur with the human diaphragm during this period of early growth. However, there is only limited information from autopsy and functional studies in infants and children, and there is no normative data for human neonatal diaphragm dimensions and how these dimensions change with growth.…”

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Diaphragm Dimensions of the Healthy Preterm Infant

Rehan

Laiprasert²,

Wallach³

et al. 2001

Pediatrics

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ABSTRACT. Background. The diaphragm is the major inspiratory muscle in the neonate; however, human neonatal diaphragm development has not been extensively studied. We hypothesized that diaphragm thickness (t di ) would be positively related to postmenstrual age (PMA), body weight, body length, head circumference, and nutritional intake.Objectives. To evaluate the evolution of diaphragm growth and motion in the healthy, preterm infant.Methods. We used ultrasound to measure t di at the zone of apposition to the rib cage and diaphragm excursion (e di ) during inspiration. Thirty-four stable, preterm infants (16 males and 18 females) between 26 and 37 weeks' PMA were studied during quiet sleep at weekly intervals until the time of discharge or transfer from the neonatal intensive care unit. All infants were clinically stable and not receiving ventilatory support.Results. We found that 1) t di increased from 1.2 ؎ 0.1 to 1.7 ؎ 0.05 mm between 26 to 28 and 35 to 37 weeks' PMA; 2) t di was positively correlated with PMA (r ‫؍‬ 0.40), body weight (r ‫؍‬ 0.52), body length (r ‫؍‬ 0.53), and head circumference (0.49), but not with postnatal nutritional intake (r ‫؍‬ 0.09); and 3) e di decreased with increasing PMA.Conclusions. Our findings suggest that diaphragm development in premature infants scales with body dimensions. We speculate that the increase in t di with age is likely attributable to increased diaphragm muscle mass, and the reduced e di with age may be resulting from a reduction in chest wall compliance. Pediatrics 2001; 108(5). URL: http://www.pediatrics.org/cgi/content/full/ 108/5/e91; diaphragm, development, ultrasound.ABBREVIATIONS. t di , diaphragm thickness; FRC, functional residual capacity; ⌬t di , change in diaphragm thickness; PMA, postmenstrual age; BL, body length, HC, head circumference; NI, nutritional intake; GA, gestational age; e di , diaphragm dome excursion; BW, body weight.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Diaphragm Dimensions of the Healthy Preterm Infant

Rehan

Laiprasert²,

Wallach³

et al. 2001

Pediatrics

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“…Therefore, it was necessary to control central respiratory drive to the diaphragm and exclude the possibility of altered CNS output (25,26). Accordingly, bilateral phrenic nerve stimulation was used to assess diaphragmatic function as previously described (19,20,27). The transdiaphragmatic pressure generated during phrenic nerve stimulation at end-expiratory lung volume was used as a measure of force-generating capacity.…”

Section: Discussionmentioning

confidence: 99%

Effect of Aminophylline on Diaphragmatic Contractility in the Piglet

et al. 1990

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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...

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“…PdiFC were generated by the transvenous phrenic nerve stimulation technique as previously described (23)(24)(25). The phrenic nerves were stimulated via bilateral external jugular vein catheter electrodes with supramaximal voltage at 20, 30, 50, and 100 Hz for 2 s. This technique allows for control of central respiratory drive to the diaphragm and excludes the possibility of altered CNS output.…”

Section: Methodsmentioning

confidence: 99%

Effect of Methylxanthines on Diaphragmatic Fatigue in the Piglet

1992

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ABSTRACT. Studies in adult animal and human subjects have suggested that the methylxanthine drugs can delay the onsGir attenuate the severity of diaphragmatic fatigue. We have investigated the effect of aminophylline and caffeine on the pressure-generating capacity of the fatigued diaphragm in 1-mo-old piglets. Measurements of ventilation, transdiaphragmatic pressure, blood gases and pH, diaphragmatic electromyogram, diaphragmatic pressurefrequency curve (PdiFC), diaphragmatic blood flow, and end-expiratory lung volume were obtained at baseline, after 90 min of inspiratory resistive loaded breathing (IRL), and again 30 min after methylxanthine infusion while still on IRL. IRL resulted in a significant decrease in minute ventilation secondary to a fall in tidal volume. Spontaneously generated transdiaphragmatic pressure increased 7-fold from baseline. EMG activity increased to both segments of the diaphragm. Abdominal expiratory muscle activity was noted after the onset of IRL and was accompanied by a fall in end-expiratory lung volume. The PdiFC was significantly decreased from baseline after 90 min of IRL, demonstrating diaphragmatic fatigue. Aminophylline did not alter the PdiFC of the diaphragm. Diaphragmatic electromyogram and tidal volume increased. No change in diaphragmatic blood flow was demonstrable after infusion of aminophylline. Serum theophylline levels averaged 117 + 11 pmol/L (21 2 2 pg/mL). Caffeine administration did not alter the PdiFC or the diaphragmatic electromyogram during IRL. Blood flow to both segments of the diaphragm decreased after caffeine infusion. Serum caffeine levels averaged 86 f 30 pmol/L (16.6 + 5.9 pg/mL). We conclude that the methylxanthines, aminophylline and caffeine, do not reverse the loss of pressure generation by the diaphragm that occurs after 90 min of IRL in the anesthetized piglet. (Pediatr Res 32: 580-584, 1992 Supported by NIH Program Project Grant HL 39187. 5(1-7). Improved force output was documented for both fatigued (1, 3, 6, 7) and nonfatigued diaphragmatic muscle (1, 7). Some investigators have found little or no improvement in diaphragmatic contractility after methylxanthine therapy (8-12), whereas others have demonstrated that methylxanthines may, in fact, aggravate diaphragmatic fatigue (1 3, 14). Methylxanthines have recently been proposed as adjunctive therapy in weaning preterm infants from mechanical ventilation (1 5). Preliminary reports have suggested that methylxanthines may improve diaphragmatic pressure output during the neonatal period (16, 17). Lopes et al. (16) found that theophylline increased mouth occlusion pressure for a given diaphragmatic EMG level in preterm human infants. However, only three infants were completely studied, and this preliminary investigation has not been subsequently confirmed. More recently, McGilliard and Farrell (1 7) presented preliminary evidence that methylxanthines produced a dose-dependent increase in twitch tension in isolated neonatal rat diaphragm. However, the concentration of drug used was high, and it i...

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Response to Resistive Loading in the Newborn Piglet

Cited by 20 publications

References 24 publications

Diaphragm Dimensions of the Healthy Preterm Infant

Diaphragm Dimensions of the Healthy Preterm Infant

Effect of Aminophylline on Diaphragmatic Contractility in the Piglet

Effect of Methylxanthines on Diaphragmatic Fatigue in the Piglet

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