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Results for “Functional Residual Capacity”

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PubMed1994

Effect of endotracheal tube leakage on functional residual capacity determination by nitrogen washout method in a small-sized lung model.

The determination of functional residual capacity (FRC) would be extremely helpful for the controlled adjustment of mechanical ventilation in sick neonates and infants. However, these patients have small lung volumes and usually have been intubated by uncuffed endotracheal tubes (ETT). Therefore, the open-circuit nitrogen washout technique (N2wo) may give false FRC values if the inspired oxygen concentration (FIO2) is high and leakage around the ETT is present. We evaluated the N2wo as supplied by the Pediatric Pulmonary System 2600 (Sensor-Medics) in a small-sized lung model by 570 measurements using five different ventilator settings, an FIO2 increasing up to 0.9, different bypass flows between 0 and 12 L/min, and various patterns of leakage, either during inspiration or exhalation, or both. We found the most reliable results (error, 0.6%; CV, 0.7%) with a bypass flow of 6 L/min. Absolute N2 volumes as small as 14 mL could be measured using an FIO2 as high as 0.9 with only slight loss of accuracy (error, 4%; CV, 2.8%). During leakage, FRC had been underestimated with a very strong correlation to the total amount of leakage over the measurement period, which was irrespective of the ventilatory parameters (r = 0.9, P < 0.001). The regression equation could, therefore, be used for FRC correction in the lung model. However, most of the miscalculation was due to N2 loss during expiratory leakage, which quite simply and reliably can be excluded by an end-inspiratory occlusion test.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional Residual Capacity↗

PubMed1986

Continuous positive airway pressure and expiratory positive airway pressure increase functional residual capacity equivalently.

The effect of continuous positive airway pressure (CPAP) and expiratory positive airway pressure (EPAP) on functional residual capacity (FRC) of ten healthy, spontaneously breathing, lightly anesthetized intubated mongrel dogs was studied. The CPAP and EPAP at 5, 10, 15, and 20 cm H2O were alternately applied to all animals. Total (lung and chest wall) compliance, esophageal pressure, airway pressure, transpulmonary pressure, control FRC, and the change in FRC (delta FRC) were measured before and after each application of CPAP and EPAP. Neither expiratory transpulmonary pressure nor delta FRC with CPAP differed significantly from that with EPAP at all levels (p greater than 0.05). These data suggest that CPAP and EPAP, when applied at the same expiratory pressure, result in an equivalent increase in FRC due to passive mechanical distention of the lungs.

Animals↗

PubMed1974

Functional residual capacity during anaesthesia. I: Methodology.

The helium dilution technique for the measurement of functional residual capacity (FRC) is reviewed with special reference to anaesthesia. A modification is described which permits measurements to be made during intermittent positive pressure ventilation. This modification causes minimal interference with the circuit as it is used for spontaneous respiration. The measuring circuit may be alternated with an open circuit without disturbance of the pattern of breathing (spontaneous or artificial). Potential errors in the measurement of FRC during anaesthesia are considered and assessment of linearity, reproducibility and accuracy is described.

Anesthesia↗

PubMed2006

Functional residual capacity and airway resistance of the rat measured with a heat- and temperature-adjusted body plethysmograph.

The functional residual capacity (FRC) and airway resistance (R(aw)) of the rat were measured, using a newly designed body plethysmograph (BPG), the inner environment of which was maintained at body temperature and was water-vapor saturated. The subjects were anesthetized and tracheally intubated male Wistar rats (n = 15). After measuring the FRC and R(aw), we analyzed the effects of inhaled methacholine (Mch, 0-8 mg/ml) on R(aw).The determined FRC was 5.37 +/- 0.22 ml (mean +/- SE). An almost linear relationship between box pressure and respiratory flow was obtained when the difference between box-gas temperature and the rectal temperature of the rat was less than 1.0 degrees C. The R(aw) at FRC was 0.230 +/- 0.017 cm H(2)O/ml/s. It increased proportionally with increases in the Mch concentration. When the dynamic changes in R(aw) were analyzed, the R(aw) was found to progressively increase during expiration; this increase continued throughout inspiration. Thus in the rat, R(aw) is not simply a function of changes in lung volume. In conclusion, the humidity- and temperature-adjusted BPG provided an absolute and possibly dynamic value of R(aw).

Administration, Inhalation↗

PubMed2001

Measurement of functional residual capacity through the transient phase of He dilution in newborns.

Helium dilution maneuver is used to determine the functional residual capacity (FRC) 14 newborns ages 1-5 mo. The model equation describes the changing alveolar fractions of He and the ventilation promoted by a rebreathing procedure that does not exceed 40 s. The model does not involve the volume of the rebreathing bag usually needed when applying rebreathing technique and which is a source of error. The equation is discretized and solved for recorded data obtained with equipment adapted to newborns. Results show a strong relationship between FRC and the biometrical indexes, and confirm those found in the literature featuring that the measurement duration of FRC can be considerably shortened.

Body Surface Area↗

PubMed2002

Functional residual capacity (FRC) does not predict response to surfactant in preterm infants.

We tested the hypothesis that the initial functional residual capacity (FRC) of preterm infants with hyaline membrane disease (HMD) could predict the response to surfactant replacement (Survanta, 4 mL/kg/dose), with a better initial FRC being correlated with a greater improvement in PaO2, a/A PO2 ratio, and FRC. Thirty-four preterm infants were studied on 41 occasions. FRC and arterial blood gases were measured immediately prior to treatment. FRC was measured by the helium dilution method. Arterial blood gases were measured again after 30, 60, and 120 minutes. FRC was measured after 120 minutes. Twenty-seven treatments resulted in an increase in PaO2 >10 mmHg (responders); 14 did not (nonresponders). There was no correlation between initial FRC, change in FRC, and change in PaO2 (r2 = 0.07). These results suggest that there is no relationship between initial FRC and response to surfactant treatment.

Biological Products↗

PubMed1980

A method of estimating the functional residual capacity of infants with respiratory distress syndrome.

This report describes and evaluates a new method of estimating the functional residual capacity (FRC) of newborn infants receiving continuous positive airway pressure (CPAP). Standard nitrogen washout methods of measuring lung volume are time consuming, frequently interfere with patient care, and may be hazardous to prematurely born infants. The authors are using a four-breath nitrogen washout technique to estimate the FRC of infants. The method was evaluated using: (1) a mechanical lung model, and (2) results from 32 newborn infants with RDS. The actual volume of the mechanical lung model was 21.6 ml and the estimated volume was 21.4 +/- 2.3 (SD) n = 13. Using different volumes in the mechanical lung model and comparing with estimated FRCs yielded a correlation coefficient of 0.96 (n = 15). Comparing the FRC of infants determined by standard nitrogen washout with the estimated FRC yielded a correlation coefficient of 0.92, n = 145. Thus, the results of the two methods are in good agreement. The new method reduces the period of breathing pure oxygen from several minutes to just a few seconds, thus, decreasing the dangers of absorption atelectasis and oxygen toxicity. The new system also lends itself well to micro-processor automation.

Functional Residual Capacity↗

PubMed1986

Functional residual capacity in normal neonates and children up to 5 years of age determined by a N2 washout method.

Functional residual capacity (FRC) was determined in 50 infants by a simplified N2 washout method. Fourteen infants were preterm, four full-term newborns and the rest were 1 month to 5 yr of age. Weight ranged from 1.19 to 25.8 kg. The method gave well reproducible values with a mean coefficient of variation of 3.9%. The FRC values are equally well correlated to weight and length (r = 0.98). The correlation with weight is linear, intercepting the x axis (FRC = 0) at a weight of 480 g, the one with length is best described by a power curve. The course of the regression lines reflects the observation that FRC per kg weight or per cm length is lower in neonates than in larger infants. The FRC measurements are in the same range as values obtained by other investigators using the N2 washout or He-dilution techniques. The values are significantly smaller than thoracic gas volume measurements obtained by plethysmography. This difference may be due to air trapping or to possible methodological problems with the plethysmographic technique. The data demonstrate that FRC can be measured easily and accurately in preterm and older infants using a N2 washout technique.

Child, Preschool↗

PubMed1998

Assessment of functional residual capacity using nitrogen washout and plethysmographic techniques in infants with and without bronchopulmonary dysplasia.

OBJECTIVE: In normal infants, functional residual capacity using plethysmography (FRCpleth) exceeds FRC(N2) (using nitrogen washout) and the within-subject difference FRC(pleth-N2) indicates the part of pulmonary gas volume not ventilated during tidal breathing. We postulated that infants with bronchopulmonary dysplasia (BPD) have an elevated FRC(pleth-N2). DESIGN: In a prospective study, FRC(pleth-N2) in healthy newborns (controls n = 17) was compared to that in neonates recovering from the respiratory distress syndrome without BPD (noBPD, studied at discharge, n = 13) and with BPD (BPD1 n = 14, studied at 36 post-conceptional weeks; BPD2 n = 16, at discharge). MEASUREMENTS AND RESULTS: Paired measurements, FRCpleth and FRC(N2), were performed using a plethysmograph (Jaeger, Germany) and an open-circuit nitrogen washout technique (SensorMedics 2600, USA). In comparison to the controls (5.2 ml/kg), FRC(pleth-N2)/kg in noBPD (12.7 ml/kg, p < 0.001), in BPD1 (24.9 ml/kg, p < 0.001) and in BPD2 (13.5 ml/kg, p < 0.001) was significantly higher. Compared with that of the controls FRCpleth was significantly increased in BPD1 (p < 0.001) and FRC(N2) was decreased in noBPD and both BPD groups. CONCLUSION: The FRC(pleth-N2) is a reliable indicator for pulmonary inhomogeneities in infants with respiratory diseases.

Breath Tests↗

PubMed1990

The relationship between conductance and functional residual capacity during drug-induced bronchoconstriction.

UNLABELLED: We wondered if the inverse changes in airway conductance (Gaw) and functional residual capacity (FRC) during histamine (H) and acetylcholine (ACH) challenge are interrelated or occur at random. In 14 normal and 14 asthmatic subjects, we determined FRC and Gaw changes corresponding to changes in specific airway conductance (SGaw) around -40 percent produced by an aerosol of H or ACH inhaled quantitatively and with measured lung deposition. We also assessed the elastic recoil following H inhalation (5A). We found that in 11 normal and nine asthmatic subjects, after H or nine normal and 11 asthmatic subjects after ACH, Gaw and 1/FRC were linearly and directly related (p less than 0.05). The steepness of this slope was directly related to the resting Gaw values. A similar relation was uncovered in the literature for asthmatic patients at rest or during recovery from natural asthma. As the elastic recoil was normal and did not change after H, it could not explain delta FRC at delta SGaw of -40 percent. IN CONCLUSION: (1) during H or ACH challenge, Gaw-FRC relationship in normal or asthmatic subjects tends to be hyperbolic and dependent on resting Gaw; (2) such a relationship is seemingly present in other bronchoconstrictor responses with a different pathogenesis; and (3) during bronchoconstriction, as Gaw vs FRC is no longer linear, SGaw becomes volume dependent.

Acetylcholine↗

PubMed1990

Functional residual capacity in anesthetized children: normal values and values in children with cardiac anomalies.

To assess the increase in functional residual capacity (FRC) with growth, FRC was measured after induction of anesthesia in two groups of children. One group consisted of 74 children, 0.1-11.2 yr of age, without signs of cardiorespiratory disease (referred to here as "normal" children), and the other of 21 children, 0.2-6.9 yr of age, with cardiac malformations. Anesthesia was maintained with halothane in the normal children and with fentanyl, droperidol, and nitrous oxide in the children with cardiac anomalies. All patients were paralyzed, their tracheas intubated, and their lungs mechanically ventilated. FRC was measured with an automated tracer gas washout technique. In 70 patients the measurements were performed in duplicate with a mean coefficient of variation of 2.0%. FRC correlated significantly with height, weight, and age in both groups. Multiple regression analysis for both groups considered together indicated no significant improvement when factors for the sex of the child or for the presence of cardiac anomalies were incorporated into the model. In normal children the simple linear and nonlinear regression equations for FRC (in milliliters) versus height (in centimeters) were: FRC = -529 + 9.48 x height, r = 0.96; and FRC = 0.00175 x height2.66, r = 0.97, respectively. The corresponding equations for FRC (in milliliters) versus weight (in kilograms) were: FRC = -92 + 29.9 x weight, r = 0.93; and FRC = 9.51 x weight1.31, r = 0.95.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

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↗

PubMed1983

Measurement of functional residual capacity during mechanical ventilation. Comparison of a computerized open nitrogen washout method with a closed helium dilution method.

The functional residual capacity of patients treated with mechanical ventilation was measured with two methods: the closed helium dilution method and the open nitrogen washout method with a computerized system. Measurements of FRC were made with and without PEEP. The results obtained did not show significant differences between the methods. Additionally we checked the accuracy of the open nitrogen washout method to measure FRC of patients and healthy subjects breathing high concentrations of oxygen which was the same as breathing air. Both methods were equally reliable and safe when measuring the FRC of patients on mechanical ventilation but the nitrogen method was easier and quicker.

Computers↗

PubMedDate not supplied

Total respiratory compliance and functional residual capacity in young children.

Measurements of total compliance of the respiratory system (CRS) by the weighted spirometer technique and functional residual capacity (FRC) by helium gas dilution were attempted in 63 healthy children (aged 2 to 7 years). Weighted spirometry was well tolerated in all but six children, and FRC measurements were successful in 42. Both measurements were reproducible and not affected by posture. Good correlations were found between CRS and height (r = 0.73) and age (r = 0.83) as well as between FRC and height (r = 0.83) and age (r = 0.74). No differences were found between boys and girls. CRS also correlated significantly with FRC (r = 0.67). In five children with cystic fibrosis, measurements of CRS, FRC and specific compliance correlated with disease severity. Our data suggest these well-tolerated techniques may provide a useful means to distinguish the effects of disease from those of growth.

Age Factors↗

PubMed1992

Changes in functional residual capacity and regional diaphragm lengths after upper abdominal surgery in anesthetized dogs.

The respiratory performance of the diaphragm may be altered by changes in mechanical or neural factors, or both, induced by upper abdominal surgery. We conducted this study to examine the effects of upper abdominal surgery on postoperative respiratory function. We studied resting lengths of four diaphragm regions, three in the costal and one in the crural diaphragm, with biplane video-roentgenography in six dogs immediately after upper abdominal surgery and up to 30 days postoperatively. Functional residual capacity was 16.7% smaller immediately after surgery compared with values obtained in the same animals after 30 days. Simultaneously measured resting lengths of each of the diaphragm regions immediately after surgery were longer, on average by 8.3%, than 30 days postoperatively. During the postoperative course, resting diaphragm lengths gradually and uniformly decreased as functional residual capacity increased. Phrenic nerve stimulation in four other dogs immediately after identical surgery resulted in large diaphragm shortening (from 42% to 55%), indicating that neither the diaphragm nor phrenic nerves were injured by the surgical manipulation. We hypothesize that respiratory dysfunction after upper abdominal surgery may be, at least in part, attributed to a decreased central drive for breathing caused by activation of the afferent limb of an inhibitory reflex owing to stretching of the diaphragm.

Abdomen↗

PubMed1997

Relationship between transdiaphragmatic and mouth twitch pressures at functional residual capacity.

The clinical application of transdiaphragmatic twitch pressure (Pdi,tw) response to phrenic nerve stimulation has been hindered by the requirement for placement of oesophageal and gastric balloons. Investigators have reported that mouth twitch pressure (Pmo,tw) estimates Pdi,tw accurately at lung volumes above and below functional residual capacity (FRC). However, it is not known whether Pmo,tw estimates Pdi,tw accurately when stimulation is performed at FRC during relaxed conditions. The aim of this study was to develop a simple method whereby measurements of Pmo could be used to predict oesophageal twitch pressure (Poes,tw) and possibly Pdi,tw at FRC. The study was performed in 11 healthy volunteers during phrenic nerve stimulation. At FRC, 9 of the 11 subjects showed a poor correlation between Pmo,tw and Poes,tw, and between Pmo,tw and Pdi,tw, probably due to varying degrees of glottic closure. Stimulations performed while subjects maintained an inspiratory flow of approximately 50 mL x s(-1), or at the point of reattaining FRC during an inspiration preceded by a limited exhalation, produced good correlations between Pmo,tw and Poes,tw (r=0.97 in both instances) and Pmo,tw and Pdi,tw (r=0.96 and r=0.95, respectively), with a steep slope. The respective slopes for the Pmo,tw Poes,tw relationship were 0.88 and 0.94, and for the Pmo,tw Pdi,tw relationship, 0.59 and 0.54. Unfortunately, these manoeuvres produced a significant increase in transpulmonary pressure (3.6+/-0.6 (SE) and 5.6+/-1.4 cmH2O, respectively), suggesting change in diaphragmatic length. Stimulations delivered while subjects performed an inspiratory effort or during exhalation against a high resistance preceded by a limited inhalation could not be used to predict Poes,tw and Pdi,tw from Pmo,tw. In conclusion, although transdiaphragmatic and oesophageal twitch pressure could be predicted from mouth twitch pressure during some inspiratory manoeuvres mouth twitch pressure was not reliable for the prediction of the oesophageal and transdiaphragmatic twitch pressure at functional residual capacity during relaxed conditions in healthy volunteers.

Adult↗

PubMedDate not supplied

Relationship of functional residual capacity to static pulmonary mechanics in chronic obstructive pulmonary disease.

Static pulmonary mechanics may not be the sole determinant of the functional residual capacity (FRC) in the chronic obstructive pulmonary diseases (COPD). To assess the relationship of FRC to pulmonary mechanics, pulmonary function tests such as spirometry, lung volumes, maximum expiratory flow volume curves, and single-breath diffusing capacity were related to compliance measurements in 65 patients with stable COPD. Compliance studies were examined over the range of tidal volume and at maximum lung inflation. The results showed that there was a poor correlation between the degree of hyperinflation at FRC and static compliance in the tidal range. However, there was a highly significant correlation between FRC and static lung mechanics at maximum lung inflation, as well as between FRC and diffusing capacity. Thus, in patients with stable COPD, FRC is a useful guide to static recoil properties of the lung as assessed at maximum lung inflation. Lung compliance measurement in tidal range may not reflect this relationship. An increase in FRC remains a useful index of pulmonary emphysema, even in the presence of chronic airway disease.

Adult↗

PubMed1987

Effects of barbiturate anesthesia on functional residual capacity and ribcage/diaphragm contributions to ventilation.

The effect of iv methohexital infusion anesthesia on functional residual capacity (FRC) (helium dilution) in 14 surgical patients (age 23 to 59 years) was determined. Eight subjects were studied wearing an inflatable mask, sealed with surgical lubricant. They showed a mean +/- SD 3.5 +/- 6.4% FRC decrease (no significance). Six subjects studied via mouthpiece awake and via endotracheal tube during anesthesia showed a mean 22 +/- 19% reduction in FRC, significantly greater than face mask studies (P less than 0.05). The greatest FRC decrease occurred in subjects with repetitive or protracted coughing after intubation. The serum methohexital level was 6.6 +/- 3.6 micrograms/ml for intubated patients, and 6.0 +/- 1.1 micrograms/ml in those with face mask (no significance). The depth of anesthesia was sufficient to produce a 50% reduction in ventilatory response to CO2 rebreathing, from 15.8 to 8.7 l/min/% CO2. Respitrace plethysmography indicated a 38 +/- 12% ribcage contribution to tidal volume during quiet breathing, which increased to 47 +/- 14% with CO2 breathing (end-tidal FCO2 9-10%). There was no dimunition of ribcage contribution during anesthesia in either group, irrespective of CO2 concentration. The authors interpret their findings to indicate that iv methohexital anesthesia does not produce FRC reduction, in contrast to an inhaled anesthetic such as halothane. It is proposed that this difference may be related to maintenance of coordinated ribcage/diaphragm muscle activity, because ribcage activity is markedly suppressed by halothane. In addition, it is proposed that FRC reduction in intubated subjects was the result of a confounding variable, namely coughing in response to the endotracheal tube.

Adult↗