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Results for “Functional Residual Capacity”

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At least 19 recordsLinked to original sources

PubMed1977

Maximal expiratory flows at functional residual capacity: a test of lung function for young children.

Maximal expiratory flows at functional residual capacity were measured noninvasively from partial expiratory flow-volume curves in 65 awake, healthy children, 4 to 6 years of age. The variabilities within and between subjects were nearly identical to those reported for flows low in the vital capacity obtained from older subjects. This test of maximal expiratory flow at functional residual capacity has the advantage that the subject does not have to inspire to total lung capacity, exhale to residual volume, or make a maximal effort, and it is therefore applicable to the testing of young children who cannot perform a vital capacity maneuver. Measurement of this flow rate in 20 patients of the same age with lung disorders of varying severity revealed abnormal flow rates in more than 50 per cent of patients. Functional residual capacity was measured by the closed-circuit helium-equilibration method. When flow rates in liters per sec were compensated for lung size, girls had significantly larger flow rates than did boys. This suggests that the lungs of young children may grow differently according to genetic determinants related to sex.

Adolescent↗

PubMedDate not supplied

The effects of expiratory positive airway pressure on functional residual capacity in normal subjects.

Functional residual capacity (FRC) was determined by constant volume, whole body plethysmography in seven normal subjects under resting conditions and following the addition of increasing levels of expiratory positive airway pressure (EPAP). There was a significant increase in FRC in six of the seven subjects studied. Grouped data showed a progressive increase in FRC with increasing EPAP (p less than 0.01). The highest level of EPAP (15 cm H2O) was associated with a 20% increase in FRC. We have been able to confirm that EPAP provides a simple and effective method of increasing FRC which could be applied to the treatment of conditions characterized by temporary and reversible reduction in lung volume.

Adult↗

PubMed1977

Lung function in infants and young children: functional residual capacity, tidal volume, and respiratory rats.

Functional residual capacity was measured by the closed-circuit, helium-equilibration method in 121 normal children 3 months to 6 years of age. Prediction equations for functional residual capacity for normal children of this age range are presented for the first time. This study demonstrates that some aspects of lung functiok can be studied relatively conveniently in young children.

Body Height↗

PubMed1977

Instrumentation for measuring functional residual capacity in small animals.

A system for measuring functional residual capacity (FRC) by the dilution method was evaluated to determine its suitability for use in neonates and small animals. The system makes use of rapid, automatically triggered valves for precise closure at end expiration. Results of a theoretical error analysis and experimental in vitro tests are presented and indicate that the measuring error in FRC is related to the FRC-to-initial rebreathing bag volume ratio. With a 200-ml bag volume one standard deviation of the calculated error was 16% for a 50-ml, 9.1% for a 100-ml, and 5.8% for a 200-ml FRC.

Animals↗

PubMedDate not supplied

Influence of increased anatomical dead space no functional residual capacity of lungs and the lung clearance index.

A study of the influence of added anatomical dead space on the functional residual capacity of the lung was carried out on a total number of 40 healthy subjects of ages ranging between 21 and 50 years. The functional residual capacity was found to decrease as additional dead space was introduced in the breathing circuit. This decrease was associated with an increase in tidal volume, lung functions, as given by the lung clearance index, were found to deteriorate with each addition of dead space. There was also an increase in pulse rate in all age groups.

Adult↗

PubMed1978

A simplified method to determine functional residual capacity during mechanical ventilation.

We describe a nonrecirculating helium-rebreathing method providing rapid and simple measurement of the functional residual capacity (FRC) in spontaneously breathing subjects and patients receiving mechanical ventilation. Results of triplicate determinations in 24 normal subjects revealed a repeatability of +/- 5.2 percent of the measured FRC, results similar to those predicted for these subjects. Results in six additional subjects were not significantly different from those obtained with a standard method using helium equilibration in the pulmonary function laboratory. Triplicate determinations in eight patients after cardiac surgery demonstrated similar repeatability. In 22 other patients studied after open-heart surgery, the FRC fell more in those who could not be weaned than in those who could be weaned from the respirator. Since an increase in FRC is the goal of therapy with positive end-expiratory pressure, this method should be useful in determining the efficacy of a particular level of positive end-expiratory pressure.

Adolescent↗

PubMed1978

Is air trapping important in the maintenance of the functional residual capacity in the hours after birth?

Serial measurements of thoracic gas volume revealed no evidence of air trapping in maintenance of functional residual capacity (FRC) in healthy term babies in the first days of life. Tidal pressue/volume and flow/volume analysis demonstrated intermittent air trapping in only 2 of 19 such babies. Artificial FRC reduction by continuous positive external pressure of 7 cm H20 induced grunting in 4 babies, but otherwise had no effect on spontaneous breathing pattern or on dynamic compliance. Group mean total pulmonary resistance rose by 52.9% but only one baby demonstrated evidence of air trapping. Our findings suggest that FRC is maintained in the immediate neonatal period by some means other than air trapping.

Age Factors↗

PubMed1979

Effects of endotracheal tube leaks on functional residual capacity determination in intubated neonates.

The present study evaluates a new closed circuit helium (He) dilution technique for determination of endotracheal (ET) tube leakage and functional residual capacity (FRC) in neonates with ET tubes. By analytically relating the fall in He concentration due to mixing with that due to leakage, it is possible to predict the final equilibration concentration of He and, therefore, correct for ET tube leaks. The system (120 ml) contains an air pump, He meter, breathing bag in cyclinder, a strip chart readout, and solenoid valve. Continuous positive airway pressure (CPAP) or ventilator pressure can be applied during testing. FRC measurements were performed on 13 neonates (799--4500 g) on CPAP with ET tubes. Leak rates were significantly higher (P less than 0.001) on 3 cm H2O CPAP compared to O cm H2O CPAP. The mean measured FRC was 53.5 ml at 3 cm H2O and 46.3 ml at 0 cm H2O CPAP. If gas leakage had not been considered in FRC calculations, the error in FRC could have been as high as 39% at 3 cm H2O CPAP and 18% at 0 cm H2O CPAP.

Birth Weight↗

PubMed1978

A study of the role of air trapping in the establishment of the functional residual capacity by analysis of pressure/volume and flow/volume loops.

Pulmonary mechanics were measured in 22 normal, full-term babies as soon as quiet, regular breathing was established. The method included construction of tidal resistance profiles, by which it was demonstrated that 'air trapping' is probably not the major factor in establishing and maintaining the functional residual capacity immediately after birth.

Air↗

PubMed1979

Dynamic mechanisms determine functional residual capacity in mice, Mus musculus.

Awake mice (22.6--32.6 g) were anesthetized intravenously during head-out body plethysmography. One minute after pentobarbital sodium anesthesia, tidal volume had fallen from 0.28 +/- 0.04 to 0.14 +/- 0.02 ml and frequency from 181 +/- 20 to 142 +/- 8. Functional residual capacity (FRC) decreased by 0.10 +/- 0.02 ml. Expiratory flow-volume curves were linear, highly repeatable, and submaximal over substantial portions of expiration in awake and anesthetized mice; and expiration was interrupted at substantial flows that abruptly fell to and crossed zero as inspiration interrupted relaxed expiration. FRC is maintained at a higher level in awake mice due to a higher tidal volume and frequency coupled with expiratory braking (persistent inspiratory muscle activity or increased glottal resistance). In anesthetized mice, the absence of braking, coupled with reductions in tidal volume and frequency and a prolonged expiratory period, leads to FRCs that approach relaxation volume (Vr). An equation in derived to express the difference between FRC and Vr in terms of the portion of tidal volume expired without braking, the slope of the linear portion of the expiratory flow-volume curve expressed as V/V, the time fraction of one respiratory cycle spent in unbraked expiration, and respiratory frequency.

Anesthesia↗

PubMed1979

Lung expansion, tidal exchange, and formation of the functional residual capacity during resuscitation of asphyxiated neonates.

Ventilatory exchange and endotracheal and esophageal pressures were measured during resuscitation of asphyxiated neonates born by cesarean section. In contrast to spontaneously breathing, vaginally born babies, an opening pressure had to be exceeded before lung expansion occurred. Subsequently there was usually a gradual increase in gaseous exchange over the first few lung inflations. A further rise in lung compliance occurred with the baby's inspiratory efforts. The functional residual capacity was formed with or without active inspiratory efforts by the baby, although gaseous retention occurred more rapidly as a result of the infant's inspiration.

Asphyxia Neonatorum↗

PubMed1979