SEARCH · PubMed Health

Results for “Functional Residual Capacity”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 145 records · Page 8Linked to original sources

PubMed1992

Measurement of bronchial responsiveness in young children: comparison of transcutaneous oxygen tension and functional residual capacity during induced bronchoconstriction and -dilatation.

Demonstration of an increased bronchial responsiveness in preschool children may support the diagnosis of asthma. Most young children cannot perform routine lung function tests. Transcutaneous PO2 (PtcO2) measurement has been applied successfully in young children, and changes in PtcO2 have been shown to correlate well with changes in forced expiratory volume in 1 second (FEV1) during bronchoprovocation testing with methacholine. PtcO2 is, however, an indirect measure of the effect of inhaled spasmogens. As functional residual capacity (FRC) can also be measured by helium dilution spirometry in preschool children, we compared PtcO2 and FRC during methacholine inhalation challenges and after inhaled terbutaline, in order to determine whether FRC is useful as a more direct measure of induced bronchoconstriction and -dilatation than PtcO2. We studied 41 allergic asthmatic children (mean age, 5.2 years) who underwent a methacholine bronchoprovocation test; 38 children received terbutaline 1 h after the final methacholine dose. The provocative concentration of methacholine that caused a 20% decrease of PtcO2 was determined, and changes in FRC and PtcO2 after each methacholine dose step were compared. Similarly, changes in PtcO2 and FRC before, and 15 and 30 min after, terbutaline were compared. All children had a drop in PtcO2 after increasing doses of methacholine; a 20% change was reached in 38 patients. Mean FRC values increased significantly but variably with increasing doses of methacholine, and changes in PtcO2 and FRC did not correlate. After terbutaline, PtcO2 increased slightly but significantly, and FRC again varied unpredictably. In a separate group of 11 children, the effect of terbutaline was assessed directly after the final methacholine dose, when significant bronchoconstriction was still present.(ABSTRACT TRUNCATED AT 250 WORDS)

Asthma↗

PubMed2003

In vitro validation of an ultrasonic flowmeter in order to measure the functional residual capacity in newborns.

Ultrasonic transit-time airflow meters (UFM) allow simultaneous measurements of volume flow V'(t) and molar mass MM(t) of the breathing gas in the mainstream. Consequently, by using a suitable tracer gas the functional residual capacity (FRC) of the lungs can be measured by a gas wash-in/wash-out technique. The aim of this study was to investigate the in vitro accuracy of a multiple-breath wash-in/wash-out technique for FRC measurements using 4% sulphur hexafluoride (SF6) in air. V'(t) and MM(t) were measured with a Spiroson SCIENTIFIC flowmeter (ECO Medics, CH) with 1.3 ml dead space. Linearity of airflow and MM were tested using different tidal volumes (V(T)) and breathing gases with different O2 and SF6 concentrations. To determine the accuracy of FRC measurements SF6 wash-in and wash-out curves from four mechanical lung models (FRC of 22, 53, 102 and 153 ml) were evaluated by the Spiroson. For each model five measurements were performed with a physiological V(T)/FRC ratio of 0.3 and constant respiratory rate of 30 min(-1). The error of measured V(T) (range 4-60 ml) was <2.5%. There was a strong correlation between the measured and calculated MM of different breathing gases (r = 0.989), and the measuring accuracy was better than 1%. The measured FRC of the four models were 20.3, 49.7, 104.3 and 153.4 ml with a coefficient of variation of 16.5%, 4.5%, 4.9% and 3%. Accordingly, for FRC <100 ml the in vitro accuracy was better than 8% and for FRC >100 ml better than 2.5%. The determination of FRC by MM measurements using the UFM is a simple and cost-effective alternative to conventionally used gas analysers with an acceptable accuracy for many clinical purposes.

Functional Residual Capacity↗

PubMed1991

Pulmonary contusion causes long-term respiratory dysfunction with decreased functional residual capacity.

To elucidate the mechanism of persistent dyspnea after blunt chest trauma, we prospectively studied the pulmonary function of 18 patients with blunt chest trauma for 6 months. Nine of the patients had flail chest and 12 had pulmonary contusion (PC). Pulmonary function was evaluated using spirometry, arterial blood gas analysis, chest x-ray studies and CT scans. Functional residual capacity (FRC) remained significantly reduced throughout the 6 months in patients with PC. Such patients experienced a fall in Pao2 when changed from a sitting position to a supine position and they had fibrous changes in the contused lung as demonstrated by CT scans at 6 months after injury. These findings were supported in an additional study of another 20 patients who had suffered PC 1 to 4 years previously. This study demonstrated that pulmonary function recovered within 6 months in patients without PC even with a residual deformity of the thoracic wall caused by flail chest, while patients with PC had decreased FRC and a fall in Pao2 when moved to the supine position even several years after injury. This might be related to the persistent dyspnea seen after blunt chest trauma.

Adult↗

PubMed1991

John Caffey Award. Determination of functional residual capacity from digital radiographs of the normal neonatal chest: studies in a rabbit model.

Spirometric measurement of lung volume in an infant or uncooperative child is often a difficult and time-consuming procedure. Previous investigators have successfully estimated total lung capacity in adults and older children by using chest radiography. The purpose of this study was to assess the accuracy of functional residual capacity (FRC) determination from chest radiographs in an animal model of the normal neonatal chest. FRC was determined with the helium dilution (HeD) method in 13 anesthetized, intubated, and paralyzed rabbits (weight range, 1.5-3.9 kg). FRC was then estimated from digital frontal and lateral chest radiographs. The radiographic estimate was made by applying measurements taken from the radiographic film pair to a geometric model of the chest. The best-fit model assumed an elliptical cross section for the intrathoracic cavity, heart, paraspinal structures, and diaphragm in the axial plane. Linear regression on independently determined HeD and radiographically determined FRC yielded a slope of 1.02 (p less than .001), an intercept of -3.02 cm3 (p = .565), and a correlation coefficient of 0.96 (p less than .001). We conclude that radiographic FRC estimates closely approximate HeD estimates in a rabbit model of the normal neonatal chest.

Algorithms↗

PubMed1990

Functional residual capacity in ventilated infants and children.

Positive end expiratory pressure (PEEP) is an accepted treatment for children with acute respiratory failure secondary to restrictive lung diseases. Using a simple technique based on open circuit nitrogen washout, we determined the functional residual capacity (FRC) in 25 ventilated children (age 3 wk-10 y) with acute respiratory failure secondary to restrictive lung disease (pulmonary edema, bilateral pneumonia). FRC measured at a physiologic level of PEEP (2-4 cm H2O) was 45.0 +/- 3.6% (mean +/- SEM; range 12-80%) lower than normal predicted values. At the PEEP level chosen clinically (4-10 cm H2O, mean = 6.0), the FRC was below normal predicted values for nonintubated children by a mean of 31.8% (range 0-73%) (p = 0.0001) and only seven patients (28%) had FRC within 20% below predicted normal values. FRC normalized at PEEP levels of 6-18 cm H2O (mean = 11.6), which was up to 200% above the clinically chosen PEEP level. In six children without lung disease who were ventilated at a PEEP level of 2-4 cm H2O, the FRC was within normal range in two, but significantly higher (by 45%) in the other four. We conclude that FRC in ventilated children with acute restrictive lung disease is significantly lower than normal and the clinically chosen PEEP fails to normalize the FRC in most of the cases.

Child↗

PubMed1976

Measurement of 'closing volume' initiated from functional residual capacity.

Comparison of the nitrogen method closing volume (CV) test, with oxygen inspiration initiated at residual volume (RV method) and functional residual capacity (FRC method), was made in 91 seated normal subjects. For RV and FRC methods, respectively CV%VC (mean+/-SD) was 14.4% (+/-6.2) and 17.5%(+/-7.5) (P=0.005); slope of Phase III of CV trace was 0.99% N2/1 (+/-0.76) and 1.66% N2/1(+/-1.07) (P=0.005); size of cardiogenic oscillations was 1.05% N2(+/-0.42) and 1.21% N2(+/-0.40) (P=0.001). These data confirm earlier predictions, based on a calculated increased lung top to bottom N2 gradient in the FRC method. Support for this mechanism was obtained in 5 additional normal subjects in whom the increased CV%VC, slope of Phase III and size of cardiogenic oscillations with the FRC method were eliminated when the top-to-bottom N2 gradient was reduced by breathing a reduced FIN2. Measurements made using the classical RV method cannot be directly compared to those using the FRC method.

Adult↗

PubMed1998

Determination of functional residual capacity (FRC) by multibreath nitrogen washout in a lung model and in mechanically ventilated patients. Accuracy depends on continuous dynamic compensation for changes of gas sampling delay time.

OBJECTIVE: Validation of an open-circuit multibreath nitrogen washout technique (MBNW) for measurement of functional residual capacity (FRC). The accuracy of FRC measurement with and without continuous viscosity correction of mass spectrometer delay time (TD) relative to gas flow signal and the influence of baseline FIO2 was investigated. DESIGN: Laboratory study and measurements in mechanically ventilated patients. SETTING: Experimental laboratory and anesthesiological intensive care unit of a university hospital. PATIENTS: 16 postoperative patients with normal pulmonary function (NORM), 8 patients with acute lung injury (ALI) and 6 patients with chronic obstructive pulmonary disease (COPD) were included. INTERVENTIONS: Change of FIO2 from baseline to 1.0. MEASUREMENTS AND MAIN RESULTS: FRC was determined by MBNW using continuous viscosity correction of TD(TDdyn), a constant TD based on the viscosity of a calibration gas mixture (TD0) and a constant TD referring to the mean viscosity between onset and end of MBNW (TDmean). Using TDdyn, the mean deviation between 15 measurements of three different lung model FRCs (FRCmeasured) and absolute volumes (FRCmodel) was 0.2%. For baseline FIO2 ranging from 0.21 to 0.8, the mean deviation between FRCmeasured and FRCmodel was -0.8%. However, depending on baseline FIO2, the calculation of FRC using TDmean and TD0 increased the mean deviation between FRCmeasured and FRCmodel to 2-4% and 8-12%, respectively. In patients (n = 30) the average repeatability coefficient was 6.0%. FRC determinations with TDmean and TD0 were 0.8-13.3% and 4.2-23.9% (median 2.7% and 8.7%) smaller than those calculated with TDdyn. CONCLUSION: A dynamic viscosity correction of TD improves the accuracy of FRC determinations by MBNW considerably, when gas concentrations are measured in a sidestream. If dynamic TD correction cannot be performed, the use of constant TDmean might be suitable. However, in patient measurements this can cause an FRC underestimation of up to 13%.

Adult↗

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↗

PubMedDate not supplied

Effect of vagal cooling on lung functional residual capacity in rats with pneumonia.

We examined the effect of cold vagal block on the functional residual lung capacity (FRC) in control rats and in rats with experimental pneumonia induced by intratracheal administration of the herbicide paraquat. The measurements were performed in a body plethysmograph in anaesthetized and intubated rats. Rats with pneumonia had tachypnoea and increased minute ventilation. Their FRC was 3.6 +/- 0.7 ml in comparison with 2.5 +/- 0.6 ml in controls (mean +/- SD). Cooling the cervical vagi, so that the Hering-Breuer inflation reflex was abolished (approximately 8 degrees C), resulted in a marked decrease of the rate of breathing and an increase of tidal volume in both groups of animals. The value of FRC did not change during vagal cooling (3.7 +/- 0.9 ml in rats with pneumonia, 2.8 +/- 0.8 ml in controls). In rats with model pneumonia, bilateral cervical vagotomy was followed by a normalization of the FRC (2.3 +/- 0.7 ml). In control animals, the FRC did not change after vagotomy (2.5 +/- 0.6 ml). We conclude that increased FRC in rats with paraquat pneumonia depends on intact conduction through thin, slowly conducting vagal fibres.

Animals↗

PubMed1980

[A simple helium-dilution method for the determination of functional residual capacity in artificially ventilated patients (author's transl)].

A convenient modification of the classical closed circuit helium dilution technique was developped to determine functional residual capacity, especially in intubated and artificial ventilated patients. The determination of the still inflatable lung volume and its variability in the course of pulmonary insufficiency or after a change in the adjustment of the respirator (PEEP a.o.), was reproducible better than +/- 10%. This method can be performed in a short time, without risk for the patient and with instruments locally independent of the ICU, surgery or recovery room.

Carbon Dioxide↗

PubMed2005

Estimation of functional residual capacity at the bedside using standard monitoring equipment: a modified nitrogen washout/washin technique requiring a small change of the inspired oxygen fraction.

We developed a modified nitrogen washin/washout technique based on standard monitors using inspiratory and end-tidal gas concentration values for functional residual capacity (FRC) measurements in patients with acute respiratory failure (ARF). For validation we used an oxygen-consuming lung model ventilated with an inspiratory oxygen fraction (Fio(2)) between 0.3 and 1.0. The respiratory quotient of the lung model was varied between 0.7 and 1.0. Measurements were performed changing Fio(2) with fractions of 0.1, 0.2, and 0.3. In 28 patients with ARF, duplicate measurements were performed. In the lung model, an Fio(2) change of 0.1 resulted in a value of 103 +/- 5% of the reference FRC value of the lung model, and the precision was equally good up to an Fio(2) of 1.0 with a value of 103 +/- 7%. In the patients, duplicate measurements showed a bias of -5 mL with a 95% confidence interval [-38; 29 mL ]. A comparison of a change in Fio(2) of 0.1 with 0.3 showed a bias of -9 mL and limits of agreement of [-365; 347 mL]. This study shows good precision of FRC measurements with standard monitors using a change in Fio(2) of only 0.1. Measurements can be performed with equal precision up to an Fio(2) of 1.0.

Adult↗

PubMed1996

Arterial blood gas changes during breath-holding from functional residual capacity.

Breath-holding serves as a model for studying gas exchange during clinical situations in which cessation of ventilation occurs. We chose to examine the arterial blood gas changes that occurred during breath-holding, when breath-holding was initiated from functional residual capacity (FRC) while breathing room air. Eight normal subjects who had a radial artery catheter placed for another study were taught to breath-hold on command from FRC. FRC was determined using respiratory inductance plethysmography. Arterial blood gas specimens were obtained at 5-s intervals until the termination of breath-holding. The average breath-holding time (+/-SD) was 35 (+/-10 s). The PaO2, PaCO2, and pH values were plotted against time and individually fit to logistic equations for each subject. The arterial PaO2 fell by a mean of 50 mm Hg during the first 35 s of breath-holding under these conditions, while the arterial PCO2 rose by a mean of 10.2 mm Hg during the first 35 s and the pH fell by a mean of 0.07 in the first 35 s. The rapid decline in PaO2 is greater than that previously reported using different methods and should be considered in clinical situations in which there is an interruption of oxygenation and ventilation at FRC while breathing room air. The changes in PaCO2 and pH are similar to those previously reported in paralyzed apneic patients.

Adolescent↗

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↗

PubMed1997

Effect of prone and supine positions on functional residual capacity, oxygenation, and respiratory mechanics in ventilated infants and children.

Although numerous reports have described the improvement in PAO2 in patients in the prone position, the underlying mechanism has yet to be determined. Some authors have suggested this phenomenon may be related to an increase in functional residual capacity (FRC); however, no previous studies have described positional changes in FRC in children with severe lung disease or in those under neuromuscular blockade. We measured arterial blood gases, FRC, Rrs, and Crs in supine and prone positions in 30 patients under neuromuscular blockade with lung disorders including moderately severe restrictive (n = 10) and obstructive (n = 10) disease and control subjects without significant lung disease (n = 10). Prone positioning was not associated with a significant increase in FRC in the cohort of 30 patients, nor in any of the subgroups. Although individual patients demonstrated large improvements in oxygenation, a statistically significant (but clinically insignificant) increase in AaPO2 ratio was observed only in the subgroup of patients with obstructive disease (0.35+/-0.03 to 0.38+/-0.04, p = 0.027). There was no correlation between changes in FRC and changes in AaPO2 (r = 0.225, p = 0.23). A significant improvement in Rrs occurred in the prone position compared to supine in patients with obstructive lung disease, decreasing from 0.264+/-0.024 to 0.216+/-0.021 cm H2O/ml/s, p = 0.009. No significant changes in Crs were seen in the prone position. We conclude that prone positioning has no effect on FRC and in this series of 30 patients significantly improved oxygenation only in patients with obstructive airway disease. A significant decrease in Rrs in patients with obstructive lung disease was also observed.

Blood Gas Analysis↗

PubMed2000

Functional residual capacity and static compliance during the first year in preterm infants treated with surfactant.

Individual lung development during the first year of life was studied in surfactant treated preterm infants with respiratory distress syndrome (RDS) and healthy controls, as well as in a group who subsequently developed chronic lung disease of the newborn (CLDN). Lung development was assessed from functional residual capacity (FRC) and compliance of the respiratory system (Crs). Twenty-one infants with RDS after preterm birth received surfactant treatment. Six of them developed CLDN. Eighteen preterm infants without RDS served as a control group. Lung function measurements were performed at term age and 4, 8, and 12 months afterwards. FRC was obtained by means of the closed-system helium dilution technique whereas static Crs was obtained by means of the weighted spirometer technique. At term age, FRC was lower in the CLDN group compared with uncomplicated RDS and controls (p < 0.05). No significant differences between groups were found in the development of FRC during the first year of life (p = 0.4). No differences were found in Crs during the first year of life in surfactant treated infants who recovered from uncomplicated RDS and the control group. However, lower values were found in the CLDN group (p < 0.05). We conclude that surfactant treated infants without CLDN have similar lung development during the first year of life as control preterm infants.

Functional Residual Capacity↗

PubMed1995

Diaphragm thickness heterogeneity at functional residual capacity and total lung capacity.

One of the determinants of muscular force is the number of myofibrils in parallel, which is approximated by thickness. To better understand the heterogeneity of diaphragm thickness, we quantified the interregional and radial patterns of thickness of nine canine diaphragms rapidly perfusion fixed in situ with glutaraldehyde at functional residual capacity (FRC) (n = 6) and total lung capacity (TLC) (n = 3). Thickness was determined gravimetrically from punch biopsies radiating from the central tendon to rib cage insertion in ventral, middle, and dorsal costal and crural regions. For comparison, the contralateral unfixed hemidiaphragm was sampled in the same fashion. The findings of this investigation include the following. 1) The costal diaphragm exhibits the same pattern of interregional heterogeneity at FRC, TLC, and in the freshly excised state. 2) The costal diaphragm is significantly thinner at FRC in situ (0.17 +/- 0.01 cm) than is the freshly excised contralateral diaphragm (0.21 +/- 0.01 cm; P < 0.05), whereas there is no significant difference between thickness at TLC and the freshly excised state. 3) There is significant, previously underscribed, radial tapering from the rib cage attachment (0.24 +/- 0.02) to the central tendon insertion (0.15 +/- 0.01 cm; P < 0.05) that is exaggerated at TLC. 4) With passive inflation from FRC to TLC, the greatest increase in thickness occurs close to the rib cage attachment for the ventral and medial costal regions but close to the central tendon in the dorsal and crural regions. We conclude that the diaphragm at FRC and TLC exhibits radial thickness heterogeneity that cannot be predicted from dimensions of the freshly excised diaphragm.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2001

Measurement of functional residual capacity in rabbits and children using an ultrasonic flow meter.

A sulfur hexafluoride (SF(6)) washin/washout technique was developed using an ultrasonic flowmeter to measure functional residual capacity (FRC) during mechanical ventilation. The ultrasonic flowmeter measures simultaneously flow and molar mass of the mainstream gas. Ventilation distribution was studied using moment ratios analysis (alveolar-based mean dilution number). Accuracy and precision of the measurement technique were tested in a mechanical lung model, and the method's sensitivity to changes of FRC was assessed in seven ventilated rabbits and six children. In the mechanical lung model with a volume range from 10 to 60 mL, the mean error of FRC measurement was 0.096 +/- 0.9 mL (range, 0-2 mL). In seven rabbits (mean body weight, 3.6 kg), measurements of FRC and alveolar-based mean dilution number were made at positive end-expiratory pressures (PEEP) of 0, 3, and 6 cm H(2)O. The mean coefficient of variation of 66 FRC-measurements was 5.5% (range, 0-15.3%). As the applied PEEP increased, mean FRC per kilogram body weight increased from 13.3 +/- 3.4 mL/kg (PEEP of 0 cm H(2)O) to 16.7 +/- 3.6 mL/kg (PEEP of 3 cm H(2)O) and to 20.8 +/- 4.3 mL/kg (PEEP of 6 cm H(2)O). Alveolar-based mean dilution number decreased accordingly from 1.94 +/- 0.42 (PEEP = 0; mean +/- SD), to 1.91 +/- 0.45 (PEEP = 3) and to 1.59 +/- 0.35 (PEEP = 6). In the six children, as applied PEEP increased, mean FRC per kilogram increased from 21.1 +/- 4.51 mL/kg (PEEP = 0), to 22.4 +/- 1.8 mL/kg (PEEP = 5) and 27.2 +/- 3.4 mL/kg (PEEP = 10). FRC measurement using the ultrasonic flowmeter is accurate and simple to use in ventilated and spontaneously breathing children.

Animals↗

PubMed1993

Inhaled beta 2-agonist and positive expiratory pressure in bronchial asthma. Influence on airway resistance and functional residual capacity.

INTRODUCTION: Positive expiratory airway pressure seems to dilate narrowed or collapsed airways, but this may be accompanied by a maintained and harmful increase in resting lung volume in obstructive pulmonary disease. PURPOSE: To evaluate the influence of inhaled terbutaline and positive expiratory pressure (PEP) on airway resistance (Raw) and functional residual capacity (FRC) in bronchial asthma. DESIGN: Randomized crossover design, single blind with regard to inhaled medication, open with regard to PEP (PEP can be felt). MATERIAL AND METHODS: Ten patients with bronchial asthma inhaled placebo and terbutaline in doses of 0.125 mg, 0.5 mg, and 1.5 mg by cone spacer combined with a facemask giving 0, 10, or 15 cm H2O PEP on separate days. FRC and Raw were measured by body plethysmography before and after inhalations. Data were analyzed by analysis of variance with terbutaline dose and PEP as factor levels. RESULTS: The effect of terbutaline: Raw decreased significantly (p < 0.0001) after 0.125 mg and 1.5 mg. The FRC did not change significantly. The effect of PEP: Raw decreased, but significantly only when the dose of 1.5 mg terbutaline was excluded from the analysis. Raw decreased with PEP 10 and 15 cm H2O, mean 0.6 (95 percent CI: -1.1, -0.2) and 0.9 (95 percent CI: -1.3, -0.4) cm H2O/L/s. The FRC did not change significantly with the PEP level. CONCLUSION: PEP only had influence on Raw when insufficient doses of terbutaline were inhaled, whereas once an efficient dose of terbutaline was administered, significant bronchodilation was achieved with or without PEP. Positive expiratory pressure did not increase FRC.

Administration, Inhalation↗