ABSTRACT. The diaphragmatic force generation and electromyographic response to long-term (1 h) inspiratory resistive loading was examined in the newborn piglet during the 3rd postnatal wk of life. Minute ventilation decreased to approximately 50% of baseline level within 5 min of imposition of a severe resistive load and remained at this level for the duration of loading. The decrease in ventilation was secondary to a fall in tidal volume at a constant frequency. There was a significant increase in central nervous system output to the diaphragm as manifested by integrated diaphragmatic electromyogram. Progressive augmentation of this index of central drive continued throughout the period of loading. Functional residual capacity fell significantly by 60 min of inspiratory resistive loading. This strategy should allow greater force generation by placing the diaphragm at a more optimal length-tension relationship. However, the force generating capability of the diaphragm was compromised as assessed by forcefrequency curve analysis. These results suggest that the diaphragm of the neonatal piglet fatigues during prolonged inspiratory resistive loading. (Pediatr Res 21: 121-125, 1987) (1) found that the force reserve of the diaphragm was small in patients with chronic obstructive pulmonary disease and that this reserve could be rapidly exhausted by minor modifications in the breathing pattern. Furthermore, in normal adult volunteers and animals, the imposition of a large inspiratory flow resistive load results in mechanical failure of the diaphragm (2-13). These studies suggest that the diaphragm, the major force generating muscle of respiration, may fail to develop adequate tension following the imposition of an added respiratory load resulting, at times, in ventilatory failure.Little is known about the ventilatory response of the newborn to altered respiratory mechanics. Abbasi et al. (14) studied the ventilatory response to short-term (10 min) inspiratory resistive loading in premature infants and found an immediate decrease in minute ventilation and tidal volume to 50% of control values. However, the infants were able to compensate for the added inspiratory resistance without significant hypoxia or hypercapnia. In the newborn monkey, respiratory compensation to shortterm added inspiratory resistive loads is a function of postnatal maturation with older animals demonstrating the ability to defend minute ventilation whereas the young monkey had a significant fall in ventilation (1 5). The response of the neonate to longterm resistive loading has not been documented. The current work was designed to evaluate the ventilatory response of the newborn piglet to a long-term (1 h) IRL, testing the hypothesis that failure to maintain baseline ventilation during inspiratory loading would occur secondary to fatigue of the diaphragm. Diaphragmatic fatigue was defined as a decrease in the force-frequency curve of the muscle (2, 16, 17). METHODSFive piglets, 14-21 days postnatal age, weighing 2.45-3.06 kg were studied. Only...

A retrospective study of 11 instances of idiopathic coronal craniostenosis in otherwise normal children revealed that early lightening, prolonged moderate to severe pelvic discomfort late in pregnancy, and/or an abnormal fetal lie were unusual gestational features indicative of intrauterine constraint for eight of these patients. The impression of unusual constraint in utero was futher implied by finding associated positional foot deformities in four of these latter eight children. We hypothesize that prolonged constraint of the fetal head may limit anteroposterior growth stretch at the coronal suture and thereby predispose toward early sutural fusion.

Although intracranial teratoma is a well-recognized entity in the differential diagnosis of pediatric brain tumors, massive congenital intracranial teratoma replacing the cerebral hemispheres of a neonate has seldom been reported. We describe two such instances that histologically exhibit predominantly neuroepithelial differentiation. In 1 case serial prenatal ultrasonography revealed ventricular dilatation prior to identification of the lesion. Theories of pathogenesis are briefly discussed.