Functional Residual Capacity in Normal Neonates and Children up to 5 Years of Age Determined by a N2 Washout Method

Abstract

ABSTRACT. Functional residual capacity (FRC) was determined in 50 infantsMore recently the He-dilution method has been scaled down and perfected for the use in infants (2) and the classical N2 washout technique has been computerized to allow breath by breath analysis of NZ washed out (3, 4). We have developed a simpler, open circuit N2 washout technique suitable to measure FRC in small animals and neonates (5).FRC or TGV measurements have been reported most frequently in term neonates or infants with respiratory illness (6)(7)(8)(9)(10)(11)(12). Only a few of these studies include preterm infants (7, 1 1, 12), and none of them has been done with the N2 washout method.In the present study FRC measurements were performed in normal infants including preterm and term neonates and infants up to 5 yr of age using the open circuit N2 washout technique (5). MATERIALS AND METHODSin preterm and older infants using a NZ washout technique.Fifty healthy infants, free of any signs of pulmonary disease or (Pediatr Res 20: 668-671, 1986) upper respiratory infection were studied. Their weight ranged from 1.19 to 25.8 kg, and their age from 1 wk to 5 yr. Eighteen Abbreviations infants were studied during the newborn period (first 28 days FRC, functional residual capacity after birth). Their gestational age ranged from 32 wk to term, 14 TGV, thoracic gas volume infants were preterm. Gestational age was determined by Dubowitz examination, and added to postnatal age to obtain postconceptional age. None of the infants had a history of respiratory disease or a need for mechanical ventilation. All were breathing room air. The measurement of FRC is an important component when Newborn infants were studied without sedation while all older evaluating pulmonary function in neonates and infants. FRC infants were sedated with 50 mg/kg chloralhydrate PO. The study needs to be known as reference value when comparing compli-was done during sleep while infants rested in the supine position. ance and conductance of individuals with different size and its The procedure was well tolerated. There were no unsuccessful increase with age provides important information about lung attempts and arousal during the measurement occurred in only growth and development.one of 10 infants. Most of the lung volume determinations in neonates andThe details of the system used to measure FRC were described infants have been done by plethysmography measuring TGV previously (5). Briefly it consists of a blender connected to a rather than the FRC. This technique is difiicult to apply to sick source of oxygen and helium, providing a stable continuous flow or small preterm infants, requires complicated highly sensitive of any helium/oxygen mixture. The gas is warmed and humidiequipment, and bears a high risk of technical error. Airway fied and passed through a breathing circuit. The infants breathe closure at FRC as may occur in the newborn infant and uneven the gas from the circuit through a T tube. The gas leaving the distribution of pleural pressure may also lead to er...

Age and the onset of desaturation in apnoeic children

“…The FRC in children correlates well with height, weight, and age; but there is no difference in FRC between the sexes.4-6 The ratio of FRC to body weight increases with age. [4][5][6] reported that the ratio of FRC to body weight was 17 5:4 ml-kg -I in infants and 24 + 6 ml-kg -I in children more than one year of age. Oxygen consumption is relatively greater in younger than in older children.…”

Lung Function Tests in Neonates and Infants with Chronic Lung Disease of Infancy: Functional Residual Capacity

“…Similarly, the disproportionate growth pattern often observed among preterm babies during early life needs to be considered when relating FRC to weight or length. 58,78 …”

Multiple-breath nitrogen washout techniques: including measurements with patients on ventilators

“…There is a particular controversy concerning the N 2 washout technique, because the reported values of FRC obtained using this method in healthy infants, whilst similar to helium dilution values in infants and older children [17,40,57], are considerably lower than reported with body plethysmography in infants. Measurements in normal spontaneously breathing newborn infants show that FRC measured by body-box (32-38 mL·kg -1 ) is significantly higher than the FRC measured by N 2 washout (16-19 mL·kg -1 with a regression to weight of 20.0 mL·kg -1 ) [53]. The differences may be due to several factors, such as: trapped gas not measured by the gas dilution techniques; unreliability of the plethysmographic methods in small infants because of airway closure; and technical difficulties with both the gas dilution methods.…”

“…However, unlike the original descriptions for adults, where a 7 min period of O 2 breathing was calculated to wash out 220 mL of tissue nitrogen (up to 10% of the FRC) [24,25], it has been suggested in newborn infants that the volume of tissue and blood N 2 washed out in a test is not more than 1% of the total [40]. That is, no significant amount of N 2 is washed out during a test which ends within 2-3 min at most, and at most will cause a 5% error [39,53]. 9.…”

“…9. As with the integration technique of GERHARDT and co-workers [40,53] for spontaneously breathing infants, the background flow must be extremely constant. Flow and volume are inversely related, so that an increase in flow of 10% will decrease the N 2 volume recorded by approximately the same amount, and thus the FRC measured.…”