SEARCH · Search PubMed

Results for “Functional Residual Capacity”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources

PubMed1974

Functional residual capacity during anaesthesia. II. Spontaneous respiration.

Functional residual capacity has been measured by helium dilution in 26 spontaneously breathing patients before and immediately after anaesthesia, which was induced with thiopentone and maintained with halothane. The mean reduction was 390 ml (16.1% or pre-induction value) and the change was highly significant (P less than 0.001). The decrease in FRC correlated with age (r equals 0.41: P less than 0.005) and less (P less than 0.001). The decrease in FRC correlated with age (r equals 0.41; P less than 0.005) and less satisfactorily with the weight/height ratio (r equals 0.31; P less than 0.05) which itself correlated with age. Inspired oxygen concentration, expiratory reserve volume and the presence of phasic expiratory muscle activity bore no significant relationship to the decrease in FRC. There was no evidence of any progressive change in FRC between 6 and 20 min after the induction of anaesthesia.

Adult↗

PubMed1976

The effect of thoracic extradural analgesia on pulmonary gas distribution, functional residual capacity and airway closure.

Pulmonary gas distribution, functional residual capacity (FRC), closing capacity (CC), arterial oxygen tension (PaO2) and alveolar-arterial oxygen tension gradient (PAO2-PAO2) were measured in seven subjects before and after the induction of extradural analgesia for routine surgery. It was found that pulmonary gas distribution was within normal limits throughout the study, although there were two patients in whom airway closure occurred consistently within the tidal volume. In both cases this was associated with a low PaO2. CC and FRC were substantially unchanged by the induction of extradural analgesia. Changes in (PAO2-PaO2) and PaO2 were usually not large, and are apparently related to factors other than changes in lung geometry.

Adult↗

PubMed1988

Abnormalities of functional residual capacity in symptomatic and asymptomatic young asthmatics.

Functional residual capacity (FRC) was measured by helium gas dilution in 186 young asthmatics, aged between 2 and 9 years. The majority were hyperinflated, as evidenced by an increase in FRC, regardless of symptom status. Symptomatic children and those hospitalized with an acute asthma attack had significantly elevated FRC when compared to asymptomatic children (p less than 0.01). Eight symptomatic children, following treatment modification, became asymptomatic. This was associated with a reduction in FRC. We suggest that an FRC result greater than one standard deviation from the mean of asymptomatic asthmatics could be used to predict inadequacy of treatment.

Asthma↗

PubMed1987

Functional residual capacity in healthy preschool children lying supine.

Functional residual capacity (FRC) was measured by the closed-circuit helium dilution method in 41 supine healthy children 1 month to 8 yr of age. In 20 children, the measurement was carried out while they were awake, and in the others, who were less cooperative, testing was done during ketamine anesthesia before elective surgery. There was no significant difference in the FRC values between these groups, and they were subsequently analyzed as a single group. For males and females separately and combined, FRC correlated significantly with height, age, and weight, both with linear and nonlinear regression analyses. No significant difference between the sexes was found. The best correlation of FRC was with height; the linear equation being FRC (ml) = -457.3 + 8.8 X height (cm) (r2 = 0.662), and the nonlinear equation being FRC (ml) = 0.0052 X [height (cm)]2.44 (r2 = 0.827).

Child↗

PubMed1981

Absolute intraesophageal pressure at functional residual capacity in frequency.

Absolute intraesophageal pressure at functional residual capacity (FRC) has been estimated in 15 infants (age 1-30 wk) by the extrapolation of the esophageal pressure-volume relationships to zero balloon volume by use of air-filled balloons in their ranges of infinite compliance. The pressure-volume relationships of the esophageal balloons (length 3.5-5.0 cm, perimeter 1.7-2.5 cm, wall thickness 0.045-0.075 mm) were determined in air and in erect and horizontal positions under water, the behavior of the balloons placed horizontally under water closely approximated that of the balloons in vivo. The mean absolute intraesophageal pressure at FRC was -1.44 cmH2O in eight normal infants and -1.56 cmH2O in seven convalescent infants with a variety of cardiorespiratory disorders. The less negative absolute end-expiratory esophageal pressure in infants when compared with that in adults can be explained by changes in lung elastic recoil, chest wall recoil, or a combination of these factors during the development and growth of the respiratory system from birth to adulthood.

Esophagus↗

PubMed1983

[Behavior of functional residual capacity in acute respiratory insufficiency].

Variations of functional residual capacity (FRC, estimated by the N2-washout technique) and oxygenation (PaO2/FIO2) were investigated in patients mechanically ventilated for acute respiratory failure (ARF, caused by pneumonia). The various ventilatory modes were compared. The results were as follows: 1. If FRC is reduced due to ARF, the reduction is diminished by PEEP. The quantitative amount of this effect cannot be predicted in the individual patients. 2. If CPPV is switched to IMV or CPAP with an equal PEEP value, FRC was not usually changed when the clinical course was favourable; however, FRC decreased if clinical signs of insufficient spontaneous respiration were present. The proportion of FRC reduction following such a change of respiratory mode was equal to the effect of removal of PEEP from 10 cm H2O to zero. 3. FRC and oxygenation do not undergo a parallel change in every situation. 4. Treatment and further research should focus not only on increasing reduced lung volume but mainly on diverting ventilation to perfused lung regions.

Acute Disease↗

PubMed1985

Measurement of functional residual capacity by sulfur hexafluoride washout.

Measurement of functional residual capacity (FRC) by the open-circuit multiple breath tracer gas washout technique is an established method. A system based upon washout of sulfur hexafluoride (SF6) during mechanical ventilation is described. The central unit in the system is a sensitive and rapid-response infrared SF6 analyzer. SF6 is washed in until the alveolar concentration of SF6 is 0.5%, a concentration so low that the supply of other gases is hardly influenced. During washout, the flow of SF6 from the lungs is calculated by a computer every 10 ms from signals representing expiratory flow and SF6 concentration. The total volume of SF6, washed out, is calculated by integration of SF6 flow. Since the alveolar concentration at the end of washin is known, the lung volume may be obtained. The measurement procedure is highly automated and the result is presented by the computer immediately after washout. Accurate and reproducible results in model lung tests were obtained during air and N2O/O2 ventilation. Comparison with body plethysmography (FRCBOX) in eight sitting healthy subjects gave the following: FRCSF6 = 7 ml + 0.98 X FRCBOX, r = 0.99. Comparison with nitrogen washout (FRCN2) in five postoperative patients gave the following: FRCSF6 = 59 ml + 0.97 X FRCN2, r = 0.97. FRCSF6 during N2O/O2 ventilation was the same as during air/O2 ventilation in a group of paralyzed patients. The measurement system has not been tested in patients with obstructive lung disease.

Adolescent↗

PubMedDate not supplied

Automated evaluation of functional residual capacity by oxygen washout.

OBJECTIVE: Measurement of functional residual capacity (FRC) is of considerable interest for monitoring ventilated patients in ICUs. However, the lack of instruments that can be used in the clinical setting has so far impeded the routine application of this measurement. It was the aim of our study to evaluate the accuracy and the reproducibility of a simplified oxygen washout technique (FRC[O2]). MATERIALS AND METHODS: For the evaluation of FRC[O2J, gas flow, CO2 and O2 concentrations were determined by the flow probe of an ICU ventilator, a mainstream capnometer and O2 analyser. In 30 volunteers FRC[O2] as measured during spontaneous breathing was compared to: 1. Helium dilution technique (FRC[He], n = 21), 2. Body plethysmography (FRC[bp], n = 9). In n = 7 male patients FRC[O2] was repeatedly evaluated during mechanical ventilation and compared to the preoperative FRC[bp]. RESULTS: FRC[O2J corresponded well with FRC[He] (range: 1.9 to 6.0 l, bias of FRC[O2]: 0.53 l (95% CI 0.24 l to 0.82 l)) and FRC[bp] (range: 2.1 to 4.3 l, bias of FRC[O2] 0.03 l (95% CI -0.30 l to 0.37 l)). The mean of the repeated FRC[O2]-measurements (basic range: 1.3 to 3.6 l) during mechanical ventilation with unchanged ventilator settings stayed unchanged. The within subject-between error ranged from 0.1 to 0.4 l (mean = 0.23 1). Mean FRC[O2] during mechanical ventilation decreased to 66.6 percent of the preoperative mean FRC[bp]. CONCLUSIONS: The automated oxygen washout technique is a simple method to measure FRC in the ICU patient.

Adult↗

PubMed1986

Influence of breathing pattern on functional residual capacity in sleeping newborn infants.

The present study was designed to assess the influence of breathing pattern on the variations of functional residual capacity during sleep in newborn infants. Functional residual capacity was measured by the He-dilution method. Neurophysiologic criteria were used to identify sleep states. Movements of chest and abdomen were monitored. Twenty-six healthy newborn infants were studied. Sixteen were premature and 10 were at term. Functional residual capacity did not change in relation to changes in sleep states. In active sleep it was 1.48 +/- 0.07 ml/cm compared with 1.50 +/- 0.06 ml/cm in quiet sleep. Functional residual capacity decreased when rib cage and abdomen moved out-of-phase with a value of 1.38 +/- 0.09 ml/cm as compared to 1.56 +/- 0.09 ml/cm when in phase (P less than 0.01), in the 7 infants who displayed these two opposite patterns.

Functional Residual Capacity↗

PubMed1980

Reference values for functional residual capacity and maximal expiratory flow in young children.

To determine the relation of functional residual capacity and maximal expiratory flow at functional residual capacity to sex, age, height, and weight in healthy young children living in Portland, Oregon, we tested 37 boys and 36 girls using a modified helium-dilution technique and partial expiratory flow-volume curves. Within the age, height, and weight ranges studied, exponential or multiple regression techniques offered no substantial advantage over simple linear regression using height, weight, or age. There were no sex differences for the relationship between either variable and age, height, or weight. These techniques can readily be used in children as young as 3 years of age and may provide a method for studying lung growth and development in early childhood and a way to observe the progression of disease or the effect of treatment in the young child.

Body Height↗

PubMed2004

Functional residual capacity and respiratory mechanics as indicators of aeration and collapse in experimental lung injury.

UNLABELLED: Increased functional residual capacity (FRC) and compliance are two desirable, but seldom measured, effects of positive end-expiratory pressure (PEEP) in mechanically ventilated patients. To assess how these variables reflect the morphological lung perturbations during the evolution of acute lung injury and the morphological changes from altered PEEP, we correlated measurements of FRC and respiratory system mechanics to the degree of lung aeration and consolidation on computed tomography (CT). We used a porcine oleic acid model with FRC determinations by sulfur hexafluoride washin-washout and respiratory system mechanics measured during an inspiratory hold maneuver. Within the first hour, during constant volume-controlled ventilation with PEEP 5 cm H(2)O, FRC decreased by 45% +/- 15% (P = 0.005) and compliance decreased by 35% +/- 12% (P = 0.005). Resistance increased by 60% +/- 62% (P = 0.005). Only the FRC changes correlated significantly to the decreased aeration (R(2) = 0.56; P = 0.01) and the increased consolidation (R(2) = 0.43; P = 0.04) on CT. When the PEEP was changed to either 10 or 0 cm H(2)O, there were larger changes in FRC than in compliance. We conclude that, in our model, FRC was a more sensitive indicator of PEEP-induced aeration and recruitment of lung tissue and that FRC may be a useful adjunct to PaO(2) monitoring. IMPLICATIONS: Lung injury was quantified on computed tomography and related to monitored values of functional residual capacity and mechanical properties of the respiratory system. We found the functional residual capacity to be a more sensitive marker of the lung perturbations than the compliance. It might be of value to include functional residual capacity in the monitoring of acute lung injury.

Airway Resistance↗

PubMed2006

Functional residual capacity measurement by heptafluoropropane in ventilated newborn lungs: in vitro and in vivo validation.

OBJECTIVE: Heptafluoropropane is an inert gas commercially used as propellant for inhalers. Since heptafluoropropane can be detected in low concentrations, it could also be used as a tracer gas to measure functional residual capacity and ventilation homogeneity. The aim of the present study was to validate functional residual capacity measurements by heptafluoropropane wash-in/wash-out (0.8%) during mechanical ventilation in small, surfactant-depleted lungs using a newborn piglet model. DESIGN: Prospective laboratory and animal trial. SETTING: Animal laboratory in a university setting. SUBJECTS: Sixteen newborn piglets (age<12 hrs, median weight 1390 g [705-4200 g]) before and after surfactant depletion (Pao2<100 torr in Fio2=1.0) by lung lavage. INTERVENTIONS: Heptafluoropropane was measured with a new infrared mainstream sensor connected with the flow sensor of the Dräger Babylog 8000. Accuracy and precision of the measurement technique were tested in a mechanical lung model with a volume range from 11 to 35 mL. Reproducibility of the method and its sensitivity to detect changes of functional residual capacity were assessed in vivo by variation of ventilatory variables. MEASUREMENTS AND MAIN RESULTS: In vitro the absolute error of functional residual capacity was <1 mL (relative errors<3%) with a coefficient of variation<4%. The coefficient of variation of consecutive in vivo measurements was only slightly higher (<5.1%). Measurement of heptafluoropropane concentrations in blood showed no significant accumulation for repeated functional residual capacity measurements within short time periods. After lung lavage, the functional residual capacity decreased from 20.9 mL/kg to 14.5 mL/kg (p<.05) despite increased ventilatory pressures, and lung clearance index (p<.001) and moment ratios (p<.01) increased significantly due to uneven alveolar ventilation. In healthy lungs, the increase in peak inflation pressure and positive end-expiratory pressure by 3-4 cm H2O had only a moderate effect on functional residual capacity (20.9+/-8.6 vs. 26.0+/-11.9 mL/kg, p=.17) and no effect on ventilatory homogeneity, whereas in surfactant-depleted lungs the functional residual capacity increased from 14.5+/-6.7 mL/kg to 29.9+/-12.6 mL/kg (p<.001) and lung clearance index and moment ratios decreased significantly (p < .01). CONCLUSIONS: Heptafluoropropane is a suitable tracer gas for precise functional residual capacity measurements tested in vitro and allows for reproducible measurements in ventilated small lungs without any adverse effects on mechanical ventilation. The sensitivity of the method is sufficiently high to demonstrate the effect of changes in ventilatory settings on the functional residual capacity and ventilation homogeneity.

Administration, Inhalation↗

PubMed1975

Lung function in childhood. 2. Thoracic gas volumes and helium functional residual capacity measurements in healthy children.

The helium dilution functional residual capacity (FRC) and the total gas volume by plethysmograph (TGV) were measured on 236 healthy London schoolchildren. There was no difference between the results obtained by the boys and girls. The results of the TGV were higher than the FRC values. From the results, normal data charts have been devised for clincial use.

Adolescent↗

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↗

PubMed1992

Relationship of functional residual capacity to various body measurements in normal sheep.

Functional residual capacity (FRC) was determined by nitrogen washout in 55 normal sheep. Data on various external body measurements were collected which included body weight, chest circumference, chest width, body length, height, and sternum length. In addition, data on wet lung weight and wet lung weight/body weight ratio were collected on 10 of the sheep. A significant correlation was found between FRC and all measured parameters except height and sternum length. Multiple linear regression of all external body measurements showed the best correlation of FRC to body weight and body length, while the addition of chest circumference and/or chest width did not significantly improve the correlation. Significant deviation from the population was noted in three sheep (5.5%) that had lung weight/body weight ratios which were significantly lower than the rest of the population.

Animals↗

PubMed1983

Functional residual capacity and sleep states in the premature newborn.

Functional residual capacity (FRC) variations in relation to sleep state changes were studied in 11 premature infants with birth weights of 1.68 +/- 0.48 kg and gestational ages of 32.7 +/- 2.2 weeks (mean +/- SD). Helium dilution was used to measure FRC, and sleep states were identified using neurophysiologic criteria. No significant difference in FRC could be demonstrated between data collected during active sleep (AS) and quiet sleep. However a relationship was shown between AS and paradoxical breathing (p less than 0.02) and between AS and irregular breathing (p less than 0.05). Several factors are discussed which might explain the discrepancy between the present data in premature infants and the previously published data in term infants. (1) Neurophysiologic identification of sleep states does not include breathing pattern whereas behavioral identification does. It is therefore possible that lung volume changes are related to breathing pattern changes and not to sleep state changes per se. (2) Maturational changes may occur among the mechanisms which control FRC, leading to a progressive stabilisation of FRC, the variation of which could become related to sleep state changes.

Functional Residual Capacity↗

PubMed1984

Decrease in functional residual capacity during sleep in normal humans.

A decrease in functional residual capacity (FRC) during sleep could result in worsening of ventilation distribution contributing to sleep hypoxemia. Therefore the purpose of this study was to determine whether FRC does decrease and to what extent it decreases in normal humans during sleep. Using helium dilution in a closed system we measured FRC in 10 healthy males during wakefulness, stage 2, stages 3-4, and rapid-eye-movement (REM) sleep. Mean FRC decreased from 3.14 +/- 0.01 (SE) liters during wakefulness to 2.95 +/- 0.01 liters in stage 2 sleep. Lowest sleep values were 2.86 +/- 0.01 liters in stages 3-4 and 2.83 +/- 0.01 liters in REM sleep (P less than 0.05 from wakefulness). Although the amount of the decrease in FRC identified during sleep was surely not large enough to impair ventilation distribution in normal humans, this degree of decrease might contribute to the hypoxemia seen in patients with severe airflow limitation.

Adult↗

PubMed1996

Measuring functional residual capacity in normal and oleic acid-injured lungs.

Functional residual capacity (FRC) is an important oxygen reserve that is often depleted in acute respiratory failure. Recent interest in the mechanisms of liquid ventilation and limited experience in measuring FRC in paralyzed, mechanically ventilated, normal and lung-injured animal models have mandated development of accurate laboratory techniques. Eight sheep, from 17 to 27 kg, were anesthetized and instrumented to provide a tracheostomy, a pulmonary artery catheter, and carotid arterial line. They were randomized to two groups, one of which received 0.07 ml/kg of intravenous oleic acid to induce lung injury. Gas ventilation of both groups was identical except for respiratory rate, which was adjusted to normalize PaCO2. FRC was measured in duplicate by both helium dilution (HD) and body plethysmography (BP). When measurements were completed, the animals were euthanized and their endotracheal tubes clamped at end expiration. The lungs were then removed and their water displacement (WD) FRC values were measured. FRC was the difference between WD and tissue weight assuming 1 ml = 1g. Pearson's correlation coefficient (R(2)) was calculated. During in vitro measurement of test lungs, HD had an R(2) value of 0.99 and BP had an R(2) value of 0.98. When compared to WD, in vivo measurement of FRC by HD had an R(2) value of 0.94 while the value for BP was 0.97. In conclusion, both HD and BP are accurate methods of determining FRC in an uninjured and injured lung model when compared to postmortem WD. Documenting changes in FRC will aid in elucidating the mechanisms of alternative ventilatory techniques.

Animals↗