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Results for “Functional Residual Capacity”

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PubMed2006

Non-invasive forced expiratory flow-volume curves to measure lung function in cats.

Forced expiratory flow-volume curves were performed in 15 cats using the non-invasive thoracic compression techniques developed for use in human infants. Cats breathed through a face mask and pneumotachygraph from which flow and volume were obtained. Thoracic compression was applied from an inflatable bag in a non-expandable jacket surrounding the animal. Bag inflation at end inspiration was initiated by a computer pulse to a pressurized chamber. Processed signals from the pneumotachygraph determined maximum-forced expiratory flow at lung volume equivalent to functional residual capacity (FRC), termed V'maxFRC. Different compression pressures were used, and the highest value from a technically satisfactory flow-volume loop was taken as the result. Mean (+/- 95% CI) V'maxFRC was 422 (369-475) ml/s. Compared with infants of similar weight (V'maxFRC approximately 180 ml/s), cats had a much higher V'maxFRC. Tests repeated another day showed a mean (+/-95% CI) percentage difference between paired tests to be 2.8 (-12.6, +18.3)%. Non-invasive forced expiratory flow-volume measurements can be reliably obtained in sedated cats.

Air Pressure↗

PubMed1975

Idiopathic scoliosis. Mechanical properties of the respiratory system and the ventilatory response to carbon dioxide.

The aims were to examine the effects of scoliosis (angle), and age on lung volumes, elastic properties of the respiratory system, and the ventilatory response to CO2. The mean age of the 55 patients was 25.4 plus or minus SEM 2.5 yr, and the mean angle was 80 plus or minus SEM 4.2. The mean plus or minus SEM percent predicted lung volumes were vital capacity (VC), 60.5 plus or minus 2.7; total lung capacity (TLC), 70,2 plus or minus 2.6; functional residual capacity (frc), 79.3 plus or minus 3.2; and residual volume (RV), 99.7 plus or minus 5.2. The correlation coefficients between the angle of scoliosis and each of the following were significant: TLC (-0.548), percent predicted TLC (-0.547), VC (-0.485), percent predicted VC (-0.523), FRC (-0.533), percent predicted FRC (-0.338), RV (-0.438), and percent predicted RV (-0.318). The mean compliance of the total respiratory system (Crs) was 0.049 litter/cm H2O plus or minus SEM 0.004, and the mean compliance of the chest wall (Ccw) was 0.080 liter/cm H2O plus or minus SEM 0.012. The Crs and Ccw were inversely proportional to the angle (r-0.620 and -0.721) and directly proportional to the height and the weight. The mean deltaV/deltaPco2 was 1.32 liter/min per mm Hg (SEM 0.171), and the mean deltaVt/deltaPco2 was 28.9 ml/mm Hg (SEM 3.64). The correlation coefficients between deltaV/deltaPco2 and the following were height, 0.499; VC, 0.792; TLC, 0.632; AND Crs, 0.520; and between the deltaTt/deltaPco2 and the following were height, 0.500; VC, 0.878; TLC, 0.802; and Crs, 0.590. We conclude that body size and the deformity were the determinants of the lung volumes and the mechanical properties of the respiratory system, and that these variables were the major factors in both the magnitude and pattern of the ventilatory response to CO2. The correlations between age and the mechanical properties of the respiratory sytem, deltaV/deltaPco2, and deltaVt/deltaPco2, were not significant, but the correlation coefficients between age and several of the derivatives of deltaV/deltaPco2 and deltaVt/deltaPco2 were significant.

Adolescent↗

PubMed1981

Static lung function in puppies after pneumonectomy.

We performed left pneumonectomy on eight puppies at 9 wk of age; seven littermates underwent a sham operation and functioned as controls. All were studied at 20 wk of age, at which time the remaining lung in the animals with pneumonectomy had the same volume, weight, and surface areas as both lungs of the controls. Total lung capacity (TLC) was the same in controls and postpneumonectomy dogs, but in the latter, the ratio of functional residual capacity to TLC (FRC/TLC) and that of residual volume to TLC (RV/TLC) were larger. Lung pressure-volume curves also differed, postpneumonectomy dogs demonstrating slightly greater recoil at lung volumes below TLC. Therefore, the increased FRC and RV of postpneumonectomy animals could not be ascribed to changes in lung recoil and must have been caused by increased chest wall recoil perhaps related to differences in shape between lung and chest wall. Studies of regional lung function revealed reduced aerated lung in the left hemithorax of the postpneumonectomy dogs and increased FRC/TLC and RV/TLC at the left base. The abnormal distribution of regional volumes did not account entirely for the increase in overall FRC and RV. Comparison of excised lung pressure-volume curves in those measured in intact animals revealed better agreement in postpneumonectomy dogs than in controls.

Animals↗

PubMed1994

Change in chest wall dimensions on induction of anaesthesia: a reappraisal.

We used a linearized magnetometer to measure the changes in rib cage and abdominal dimensions which occurred during induction of anaesthesia with i.v. methohexitone when spinal movement was prevented. By plotting the changes on an adaptation of the Konno and Mead plot, we inferred changes in chest wall volume, which decreased in 11, did not change in two and increased in four patients (n = 17). The mean change was a decrease (P < 0.05). These results differ from previous studies using magnetometry but are consistent with those of three-dimensional imaging. A decrease in chest wall volume could explain the decrease in functional residual capacity associated with general anaesthesia.

Abdomen↗

PubMed1976

Static and dynamic lung compliance in asthmatic symptom-free children.

The static lung compliance was studied in 27 symptom-free asthmatic children, 6-14 years old. The technique of so-called end-expiratory compliance measurement as well as that of the 'zero volume' in the balloon at barometric pressure, used in this study, have been previously discussed. The static lung compliance value is larger than the dynamic lung compliance value, this difference being larger in asthmatic than in healthy children. This difference is explained by higher static lung compliance values in asthmatic than in healthy children, whereas dynamic lung compliance values are only slightly lower in the group of asthmatic patients compared to healthy children. Static lung compliance per unit of lung volume (specific static lung compliance) is identical in both groups. Static recoil pressure at 80% of total lung capacity (TLC) is similar in asthmatic and healthy children. However, in symptom-free asthmatic children with hyperinflated lungs [functional residual capacity (FRC) higher than 25% of predicted value and FRC/TLC ratio higher than 0.45], static recoil pressure at 80% TLC is lower than the predicted value, this difference being not significant.

Adolescent↗

PubMed1985

[PEEP ventilation without hyperinflation of the lungs. A primary ventilatory pattern of controlled respiration based on expiratory volume curves].

When starting controlled ventilation with PEEP, a ventilation within the mid-third of the inspiratory capacity (IC) with a tidal volume (VT) of IC/3 ("primary VT") is recommended, to increase functional residual capacity (FRC) effectively and to avoid adverse haemodynamic effects related to hyperinflation of the lung. The quasi-static expiratory pressure-volume curves (VPE) of 28 patients with acute respiratory failure were graphically analyzed to evaluate the PEEP which could be expected to increase FRC by 1/3 of the IC ("primary PEEP"). the volume by which VT must be reduced, to keep the endinspiratory lung volume constant, if a higher PEEP would be desired. The "primary PEEP" was found to be 12,2 +/- 2,5 cmH2O, thus confirming the clinical practice to use preferentially 10 cmH2O. In 3 patients with progressive pulmonary failure and severely reduced IC as well as in 3 grossly obese patients the "primary PEEP" was markedly higher (15-18 cmH2O). The volume-pressure relation in the steep linear mid-third of the VPE correlated closely with the IC (r = 0.92). This means that the increase in FRC per 1 cmH2O PEEP in this range can be expressed as a nearly constant fraction of the IC (delta FRC/ delta PEEP = IC/32). Hence, to avoid endinspiratory hyperinflation of the lung, it is recommended to reduce the "primary VT" by IC/32 or, which means the same, by VT/10 per 1 cmH2O PEEP exceeding 10. If, however, a ventilatory pattern has to be chosen with respect to gas exchange, where hyperinflation cannot be excluded, this should be done under close haemodynamic control using a Swan-Ganz catheter.

Adolescent↗

PubMed1985

Peritonitis, dialysate infusion and lung function in continuous ambulatory peritoneal dialysis (CAPD).

Pulmonary function tests were done in seven CAPD patients with acute peritonitis on the day of admission to the hospital and after recovery. Subsequently, the effect of dialysate infusion alone on lung function was studied in 19 patients initiated on CAPD and nine of these patients were restudied 7.6 +/- 4.1 months later. Peritonitis was associated with a 30% reduction in vital capacity and a significant fall in arterial oxygen tension (7 to 11 mmHg) (p less than 0.01). Dialysate infusion alone decreased functional residual capacity (FRC) and produced small changes in PaO2 which were more pronounced in the supine position. The decrease in PaO2 observed in changing from sitting prior to dialysate infusion, to supine after dialysate infusion was due to the development of airways closure at resting lung volumes. Follow-up studies in nine patients demonstrated a continued and significant fall in FRC with dialysate infusion, without however, any changes in PaO2. We conclude that peritonitis in CAPD patients is accompanied by significant changes in lung function which are probably due to a decrease in diaphragmatic mobility resulting in atelectasis and underventilation of dependent lung zones. In CAPD patients without peritonitis, dialysate infusion in the supine position produces significant changes in PaO2, but with time, compensatory mechanisms develop to abolish the changes in PaO2.

Adult↗

PubMed1984

Lung volume dependence of pharyngeal cross-sectional area in patients with obstructive sleep apnea.

We examined the relationship between lung volume and pharyngeal cross-sectional area in 9 obese patients with obstructive sleep apnea and 10 age-matched, obese subjects without sleep apnea. Pharyngeal area was measured in the upright, seated posture using an acoustic reflection technique. Measurements were made at a rate of 5 per second during a slow exhalation from total lung capacity (TLC) to residual volume (RV). In the control subjects, the mean +/- SE pharyngeal area was 5.6 +/- 0.2 cm2 at TLC, and decreased by 30 +/- 5% over the vital capacity range to 3.9 +/- 0.3 cm2 at RV. In contrast to the control subjects, in patients with obstructive sleep apnea, pharyngeal area was 5.0 +/- 0.2 cm2 at TLC, and decreased by 54 +/- 6% over the vital capacity range to 2.3 +/- 0.3 cm2 at RV. The difference in pharyngeal area between the patients and control subjects was significant at all lung volumes below TLC, as was the difference in the magnitude of change in pharyngeal area with change in lung volume. The results indicate that in obese patients with obstructive sleep apnea, pharyngeal cross-sectional area is abnormally small, and varies considerably with changes in lung volume. The beneficial effects of weight reduction in such patients may relate to the coincident increase in functional residual capacity, causing an increase in upper airway size.

Adult↗

PubMed2003

Effects of gravity on lung diffusing capacity and cardiac output in prone and supine humans.

Both in normal subjects exposed to hypergravity and in patients with acute respiratory distress syndrome, there are increased hydrostatic pressure gradients down the lung. Also, both conditions show an impaired arterial oxygenation, which is less severe in the prone than in the supine posture. The aim of this study was to use hypergravity to further investigate the mechanisms behind the differences in arterial oxygenation between the prone and the supine posture. Ten healthy subjects were studied in a human centrifuge while exposed to 1 and 5 times normal gravity (1 G, 5 G) in the anterioposterior (supine) and posterioanterior (prone) direction. They performed one rebreathing maneuver after approximately 5 min at each G level and posture. Lung diffusing capacity decreased in hypergravity compared with 1 G (ANOVA, P = 0.002); it decreased by 46% in the supine posture compared with 25% in the prone (P = 0.01 for supine vs. prone). At the same time, functional residual capacity decreased by 33 and 23%, respectively (P < 0.001 for supine vs. prone), and cardiac output by 40 and 31% (P = 0.007 for supine vs. prone), despite an increase in heart rate of 16 and 28% (P < 0.001 for supine vs. prone), respectively. The finding of a more impaired diffusing capacity in the supine posture compared with the prone at 5 G supports our previous observations of more severe arterial hypoxemia in the supine posture during hypergravity. A reduced pulmonary-capillary blood flow and a reduced estimated alveolar volume can explain most of the reduction in diffusing capacity when supine.

Acceleration↗

PubMed1990

Pulmonary function following positive pressure ventilation initiated immediately after birth in infants with respiratory distress syndrome.

Cardiopulmonary function following positive pressure ventilation, initiated immediately after birth, was evaluated in 10 very low birthweight infants with respiratory distress syndrome (RDS; RDS infants). Multiple gas rebreathing methodology was used to measure functional residual capacity (FRC), diffusing capacity of the lung for carbon monoxide (DLCO) and effective pulmonary capillary blood flow (Qeff) at 2, 24, and 72 hr of age. Cardiopulmonary function variables were also measured at 2 hr of age in 10 infants of similar birthweight who did not have RDS (non-RDS infants). In RDS infants, mean FRC at both 2 hr of age (15 mL/kg or 0.42 mL/cm) and 24 hours of age (20 mL/kg or 0.54 mL/cm) was less than published predicted values for healthy infants and significantly less than values in non-RDS infants at 2 hours of age (29 mL/kg or 0.8 mL/cm). By 72 hr of age, mean FRC in RDS infants rose to predicted. At 2 and 24 hours of age, mean Qeff in RDS infants (41 and 38 mL/min/kg, respectively) was below predicted, as well as below the value observed in non-RDS infants at 2 hr of age (62 mL/min/kg). in RDS infants. DLCO remained well below published predicted values throughout the first three days of life. We conclude that early aggressive respiratory therapy does not result in the establishment of normal lung volumes during the first day of life, but it does so by 3 days of age. However, in spite of intubation immediately after birth and the application of continuous positive pressure ventilation during the first 3 days of life, very low birthweight infants with RDS continue to have significant alteration in lung function, evidenced by impaired diffusing capacity of the lung and low arterial-alveolar oxygen tension ratios.

Functional Residual Capacity↗

PubMed1996

Auto-positive end-expiratory pressure during one-lung ventilation using a double-lumen endobronchial tube.

The present study was undertaken to investigate the possible relationships between the magnitude of autopositive end-expiratory pressure (auto-PEEP) and measured PaO2 during one-lung ventilation (OLV). Forty-one adults received OLV anesthesia using a tidal volume of 8 mL/kg and a respiratory rate of 12 breaths/min. Auto-PEEP was quantified using an end-expiratory port occlusion method. During two-lung ventilation (2LV), auto-PEEP was observed in 18 of 41 patients and ranged from 0.5 to 2.5 cm H2O. During OLV, auto-PEEP was observed in 34 of 41 patients and ranged from 0.5 to 10 cm H2O. The mean (+/- SD) value of auto-PEEP was significantly higher during OLV than during 2LV (3.2 +/- 3.3 cm H2O versus 0.5 +/- 0.7 cm H2O, P < 0.0001). Auto-PEEP during OLV correlated inversely with preoperative forced expiratory volume in 1 s/forced vital capacity (y = 12.5 - 0.13x, r = -.05, P < 0.005). During OLV, there was no significant correlation between auto-PEEP and measured PaO2. These findings confirm that many patients do not exhale completely to functional residual capacity during OLV.

Adult↗

PubMed1985

Elevated lung volume and alveolar pressure during jet ventilation of rabbits.

We measured lung volume, tidal volume, and pressures at the airway opening, trachea, and alveoli during jet ventilation of rabbits at frequencies from 2 to 15 Hz when inspiratory time was varied from 10 to 50% of the ventilator cycle. Lung volume was determined dynamically and was dependent on tidal volume, expiratory duration, and the expiratory time constant of the respiratory system. Tidal volume decreased with increasing frequency and lung volume, and was greater than estimated dead-space volume over most of the frequency range studied. Pressure at the airway opening was not a good estimate of either mean pressure or pressure swings in the alveoli. Tracheal pressure corresponded fairly well to alveolar pressure. Alveolar pressure swings diminished with increasing frequency and decreasing inspiratory duration. In the clinical setting these results mean that measurement of pressures at the airway opening is not an adequate way to monitor patients during jet ventilation. In addition, the clinician must be aware that substantial increases in functional residual capacity may occur during jet ventilation, thereby placing the patient at risk of pneumothorax.

Animals↗

PubMed1985

Fast real-time moment-ratio analysis of multibreath nitrogen washout in children.

To apply real-time moment-ratio analysis to multibreath N2-washout curves (MBNW) from children, a new processor-controlled device was constructed. Flow and fractional N2 concentration (FN2) were each sampled by 200 Hz. An electromagnetic triple-valve system, with an instrumental dead space of 36 ml and a valve resistance of 0.3 cmH2O . l-1 . s, was connected in series with a pneumotachograph and an N2 analyzer (Ohio 720) placed next to the mouthpiece. A FORTRAN/MACRO program on a PDP 11/23 computer enabled measurement of inspiratory and expiratory flow and FN2 sampling by a 12-bit analog-to-digital converter. The fast real-time digital processing of the N2 and flow signals incorporated filtering, delay compensation, and corrections for the effects of changes in gas composition and temperature. MBNW dynamics of the lungs were studied in 17 healthy and 28 asthmatic children and in 16 patients with cystic fibrosis, evaluating the moment ratios of the washout curves as indices of the ventilation characteristics. Intrasubject variability of the moment ratios (m1/m0, m2/m0) and determination of functional residual capacity (FRC) varied between 6.3 and 14.7% (depending on which parameter is considered) and was comparatively lower than other indices previously investigated in adults. In addition, the sensitivity of the moment ratios for discriminating different stages of ventilation inhomogeneity was superior to other indices. m2/m0 is closely related to the simultaneously measured airway resistance, and the ratio between cumulative expired volume and FRC is correlated with the ratio between residual volume and total lung capacity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1994

Displacements and strains in the costal diaphragm of the dog.

Radiopaque markers were attached at 1- to 2-cm intervals along three nearby muscle bundles to cover rectangular regions of the mid-costal diaphragms of seven dogs. The markers were tracked by biplane video fluoroscopy during spontaneous breathing (SB), mechanical ventilation with the same tidal volume (MV), and at inflation to total lung capacity (TLC) in the prone and supine positions. The three-dimensional positions of the markers at functional residual capacity (FRC), at end inspiration during SB and MV, and at TLC were determined, and the strains in the plane of the diaphragm relative to FRC were calculated. The principal strains were found to lie nearly along the muscle bundle direction and perpendicular to it. The principal strains along the muscle bundles, which describe muscle shortening, were uniform among the three bundles and uniform along the bundle for MV. For SB, in the prone and supine positions, shortening was approximately 30% greater in the middle of the bundle than near the central tendon and chest wall. Although the tidal volumes were the same for SB and MV, the shortening was larger for SB. The strains perpendicular to the bundle direction were not significantly different from zero. It appears that, for the loads that occur during tidal breathing, the diaphragm is inextensible in the direction perpendicular to the muscle direction. There is a very small displacement of the costal diaphragm at its insertion on the chest wall. The displacement at the central tendon is primarily a result of muscle shortening and rotation of the arc of the muscle around its insertion on the chest wall.

Animals↗

PubMed2002

Sex-specific prediction equations for Vmax(FRC) in infancy: a multicenter collaborative study.

Measurements of maximal flow at functional residual capacity (Vmax(FRC)) from partial forced expiratory maneuvers remain the most popular method for assessing small airway function in infants and young children. However, the lack of appropriate reference data that are both applicable outside the centers that developed them and reflect the normal variability between healthy subjects has limited interpretation of Vmax(FRC) results in both clinical practice and research. To address this problem, we collated Vmax(FRC) data from 459 healthy infants (226 boys) tested on 654 occasions during the first 20 months of life from three collaborating centers. Multiple linear regression analysis indicated that sex, age, and length were important predictors of Vmax (FRC), which was, on average, 20% higher in girls than in boys during the first 9 months of life. (Vmax(FRC))0.5 (ml x second(-1)) = 4.22 + 0.00210 x length2 (cm) for boys (RSD = 3.01; R2 = 0.48), and -1.23 + 0.242 x length for girls (RSD = 2.72; R2 = 0.49). Alternative models incorporating both age and length z scores are also described. Failure to use sex-specific prediction equations for Vmax(FRC) may preclude detection of clinically significant changes in girls and lead to false reports of diminished airway function in boys. Appropriate use of z scores, which indicate a "normal" range (z scores of 0 +/- 2) for Vmax(FRC), during infancy should also improve interpretation of both clinical and research studies.

Body Constitution↗

PubMed1997

Influence of ethnicity and gender on airway function in preterm infants.

While maximal expiratory flow at functional residual capacity, calculated from partial expiratory flow volume curves (V'maxFRC), is a valuable measure of peripheral airway function in infants, limited data are available in preterm infants despite their high prevalence of respiratory problems. To investigate the influence of gender and ethnic group, V'maxFRC and other indices of respiratory function were measured in 28 black and 28 white preterm infants (50% female in each group) at time of discharge from the neonatal unit (mean [SD] weight 2.36 [0.3] kg, postnatal age 19 [9] d). No infant had any history of cardiorespiratory disease and all were born to non-smoking mothers. V'maxFRC tended to be higher in girls than boys (115 versus 94 ml.s-1 [95% CI: -5; 47]) but there was no significant difference in this parameter between black and white infants (111 versus 98 ml.s-1 [95% CI of difference: -12; 40]). Respiratory resistance (Rrs) was significantly lower in black than white infants (95% CI: -2.9; -0.4 kPa.L-1.s) and tended to be lower in female than male infants (95% CI: -2.3; 0.2 kPa.L-1.s). Similarly, time to peak tidal expiratory flow as a proportion of total expiratory time (tPTEF:tE) was significantly longer in black than white (95% CI: 0.06, 0.20) and in female than male (95% CI: 0.02, 0.15) infants. These findings suggest that certain parameters of airway function may be influenced by both ethnic group and gender in preterm infants, both of which should therefore be taken mw account when investigating the effects of disease and/or therapeutic interventions in this group.

Airway Resistance↗

PubMed2003

Flow limitation in infants with bronchopulmonary dysplasia and respiratory function at school age.

Bronchopulmonary dysplasia is associated with abnormalities in lung function during infancy, yet many infants recover with no respiratory problems in the long term. We therefore did a longitudinal study of pulmonary function in 18 children with moderate to severe bronchopulmonary dysplasia. Forced expiratory volume in 1 s (FEV1) and forced mid-expiratory flow (FEF25-75) at school age were lower than normal in 15 of 18 children, and both showed a significant positive correlation with the maximal flow at functional residual capacity (Vmax(FRC)) at 24 months of age (r=0.68 and 0.85, respectively). Our results suggest that assessment of respiratory function during infancy can help to identify children with bronchopulmonary dysplasia at risk of incomplete recovery of respiratory function during childhood.

Bronchopulmonary Dysplasia↗

PubMed1995

Effective argon-FRC with a rebreathing technique in children with acute asthma.

In children with asthma the measurement of functional residual capacity (FRC) with standard dilution techniques requires long rebreathing times of the inert gas, i.e., helium, to reach alveolar units with long time constants. A modification of the argon-freon-22 rebreathing technique enables argon to dilute in the readily accessible lung volume and potentially can give a measurement of FRC. However, the rebreathing tests cannot be prolonged for more than 1 min thus allowing argon to reach only the rapidly accessible lung units which are grossly useful in gas exchange (effective FRC, EFRC). The aim of this study was to measure the EFRC and standard lung function in children with acute severe asthma, assess their response to nebulized salbutamol, and evaluate the relations of the EFRC response to baseline spirometric measurements. Twenty-four asthmatic children who were admitted to the hospital with an acute asthma attack had spirometry and triplicate EFRC measurements before and after treatment with nebulized salbutamol. Eighteen patients had repeated the respiratory tests 50 days later when they had fully recovered. A significant proportion (28.9%) of the argon traces obtained at baseline before treatment did not equilibrate. However, in the great majority of these tests the oscillation of the argon traces over the last 3 breaths of the test was < 5% of the simultaneous argon concentration. The EFRC values derived from the argon traces with minimal oscillation (< 5%) were reduced during the acute asthma attack when compared with the paired values obtained after recovery (P = 0.03). The administration of salbutamol caused a fall from the baseline EFRC (P = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗