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Results for “Functional Residual Capacity”

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PubMed1996

Cysteinyl leukotriene involvement in chronic lung disease in premature infants.

The pathophysiology of chronic lung disease (CLD) in premature infants who require mechanical ventilation and prolonged oxygen supplementation has been well-described but the underlying mechanisms are not understood. Our aim was to test the hypothesis that excess cysteinyl leukotriene (LT) production was a contributing factor in CLD. We compared LT production and lung function, at 7 months of age, in nine premature infants with CLD and in eight control infants without CLD. None of the control infants developed any neonatal respiratory problems, but two subsequently required bronchodilator therapy. Respiratory function was assessed by the measurement of thoracic gas volume (TGV), airways resistance (Raw) and functional residual capacity (FRC). Total cysteinyl LT production was quantified by measurement of leukotriene E4 (LTE4) in a spot urine sample. Although all patients were asymptomatic at follow-up, there was evidence of significant lung function abnormalities in infants with CLD. The CLD infants had significantly elevated TGV, Raw and FRC values reflecting airway obstruction when compared to the controls. Urinary LTE4 levels were significantly higher in the CLD infants when compared to the controls (geometric mean: 741 and 337 pmol.mmol-1 creatinine, respectively). There was no direct correlation between urinary LTE4 levels in the CLD group and TGV, Raw or FRC values. Although this study is small and a direct correlation between lung function and urinary leukotriene E4 was not demonstrated, pathological lung function and an enhanced urinary leukotriene E4 production in infants with chronic lung disease would tend to suggest that the cysteinyl leukotrienes were involved in the sequelae of this disease.

Airway Obstruction↗

PubMed1997

[Progress of respiratory muscle dysfunction in patients with severe chronic obstructive disease].

The altered function of respiratory muscle function in chronic obstructive pulmonary disease (COPD) has been documented by short term studies but not by prospective follow-up. To evaluate the progression of muscle dysfunction and its relation to hyperinflation, air flow obstruction and generalized muscle weakness, we studied seven patients upon admission and 10 to 25 months later. We measured peak inspiratory (PImax) and expiratory (PEmax) pressures in the mouth, peak pleural inspiratory pressure (Pplimax) and peak transdiaphragmatic pressure (Pdimax). Pdimax was measured using gastric (Pg) and esophageal (Ppl) balloons. The slope of excursion of Pg and Ppl measured at the end of inspiration and expiration (Pg/Ppl) was used to assess respiratory muscle recruitment. Nutritional status was indexed as the ratio of weight to height (W/H). FEV1 remained unchanged (1.0 +/- 0.1 to 0.8 +/- 0.3 L), while functional residual capacity (FRC) increased from 7.1 +/- 1.0 to 8.9 +/- 2.0 L (p < 0.05). W/H, PImax, Pplimax and PEmax remained unchanged, while Pdimax decreased significantly from 83 +/- 35 to 47 +/- 16 cmH2O. Diaphragm loading (TTDI and Pdi/Pdimax) were found to increase and Pg/Ppl shifted toward increased use of accessory muscles. The last finding was significantly related to changes in FRC (r = 0.87; p < 0.05). We conclude that diaphragm function deteriorates progressively in patients with severe COPD, even though overall inspiratory muscle strength is preserved, apparently as a consequence of the effect of mechanical factors (hyperinflation) but not of air flow obstruction or generalized muscle weakness.

Data Interpretation, Statistical↗

PubMed1985

Acute effects of 0.12 ppm ozone or 0.12 ppm nitrogen dioxide on pulmonary function in healthy and asthmatic adolescents.

Adolescent asthmatic subjects have been shown to be much more sensitive than healthy adolescents to the inhaled effects of sulfur dioxide. To test whether similar adolescent asthmatics are more sensitive to other common ambient air pollutants, 10 healthy and 10 asthmatic adolescent subjects were exposed for 60 min to filtered air, 0.12 ppm ozone (O3), and 0.12 ppm nitrogen dioxide (NO2) on separate days at rest. The following pulmonary functional values were measured before, at 30 min, and after 60 min of exposure: peak flow, total pulmonary resistance (RT), thoracic gas volume at functional residual capacity (FRC), maximal flow at 50 and 75% of expired vital capacity (Vmax50 and Vmax75), and forced expiratory volume in one second (FEV1). Following 60 min of exposure at rest to low concentrations of O3 or NO2, there were no consistent significant functional changes in either healthy or asthmatic adolescent subjects. There also were no measurable differences between the 2 groups.

Adolescent↗

PubMed1993

Effects of mean airway pressure and tidal volume on lung and chest wall mechanics in the dog.

Dependencies of the dynamic mechanical properties of the respiratory system on mean airway pressure (Paw) and the effects of tidal volume (VT) are not completely clear. We measured resistance and dynamic elastance of the total respiratory system (Rrs and Ers), lungs (RL and EL), and chest wall (Rcw and Ecw) in six healthy anesthetized paralyzed dogs during sinusoidal volume oscillations at the trachea (50-300 ml; 0.4 Hz) delivered at mean Paw from -9 to +23 cmH2O. Changes in end-expiratory lung volume, estimated with inductance plethysmographic belts, showed a typical sigmoidal relationship to mean Paw. Each dog showed the same dependencies of mechanical properties on mean Paw and VT. All elastances and resistances were minimal between 5 and 10 cmH2O mean Paw. All elastances, Rrs, and RL increased greatly with decreasing Paw below 5 cmH2O. Ers and EL increased above 10 cmH2O. Ecw, Ers, Rcw, and Rrs decreased slightly with increasing VT, but RL and EL were independent of VT. We conclude that 1) respiratory system impedance is minimal at the normal mean lung volume of supine anesthetized paralyzed dogs; 2) the dependency of RL on lung volume above functional residual capacity is dependent on VT and respiratory frequency; and 3) chest wall, but not lung, mechanical behavior is nonlinear (i.e., VT dependent) at any given lung volume.

Air Pressure↗

PubMed1995

Prognosis with preoperative pulmonary function and lung volume assessment in infants with congenital diaphragmatic hernia.

OBJECTIVES: To determine whether fatal pulmonary hypoplasia, as assessed by functional residual capacity (FRC), can be distinguished from other reversible causes of respiratory failure in infants with congenital diaphragmatic hernia (CDH). METHODS: In the present study, 25 term neonates having CDH without other anomalies (mean birth weight +/- SD, 3.25 +/- 0.50 kg) were enrolled prospectively into a protocol evaluating pulmonary function. Lung compliance (CL) and FRC were measured before diaphragmatic repair and compared with the highest oxygenation index (OI) and lowest PaCO2, also obtained preoperatively. Pulmonary function assessment was repeated after diaphragm repair on postoperative days 3 and 7. CL was determined by esophageal manometry and pneumotachography, and FRC was determined by helium dilution. RESULTS: Fifteen infants (60%) survived to hospital discharge. Eighteen (72%) required extracorporeal membrane oxygenation (ECMO) for support, and of these, 8 (44%) survived. PaCO2 was similar preoperatively in infants grouped as survivors without ECMO, survivors with ECMO, and nonsurvivors. In nonsurvivors (all of whom received ECMO), the preoperative OI was significantly higher (51 +/- 21), CL was less (0.11 +/- 0.04 mL/cm of water per kg), and FRC was smaller (4.5 +/- 1.0 mL/kg) than in the survivors who required ECMO (26 +/- 18, 0.18 +/- 0.08 mL/cm of water per kg, and 12 +/- 5 mL/kg, respectively), as well as in the survivors without ECMO, (6 +/- 2, 0.32 +/- 0.16 mL/cm of water per kg, and 15.8 +/- 4 mL/kg, respectively). The group surviving with ECMO had a higher OI than the infants surviving without ECMO. All nonsurviving infants had FRCs of less than 9.0 mL/kg preoperatively. In contrast, only 2 of the 15 survivors had preoperative FRCs less than 9 mL/kg. CONCLUSIONS: The results of this study suggest that preoperative assessment of FRC may predict fatal pulmonary hypoplasia in most infants with CDH.

Analysis of Variance↗

PubMed2006

Mechanical response to methacholine and deep inspiration in supine men.

The effects of supine posture on airway responses to inhaled methacholine and deep inspiration (DI) were studied in seven male volunteers. On a control day, subjects were in a seated position during both methacholine inhalation and lung function measurements. On a second occasion, the whole procedure was repeated with the subjects lying supine for the entire duration of the study. On a third occasion, methacholine was inhaled from the seated position and measurements were taken in a supine position. Finally, on a fourth occasion, methacholine was inhaled from the supine position and measurements were taken in the seated position. Going from sitting to supine position, the functional residual capacity decreased by approximately 1 liter in all subjects. When lung function measurements (pulmonary resistance, dynamic elastance, residual volume, and maximal flows) were taken in supine position, the response to methacholine was greater than at control, and this was associated with a greater dyspnea and a faster recovery of dynamic elastance after DI. By contrast, when methacholine was inhaled in supine position but measurements were taken in sitting position, the response to methacholine was similar to control day. These findings document the potential of the decrease in the operational lung volumes in eliciting or sustaining airflow obstruction in nocturnal asthma. It is speculated that the exaggerated response to methacholine in the supine posture may variably contribute to airway smooth muscle adaptation to short length, airway wall edema, and faster airway renarrowing after a large inflation.

Adult↗

PubMed1996

Body plethysmographic measurement of thoracic gas volume without panting against a shutter.

When a subject breathes through a pneumotachograph in a body box, the measured value of specific airway resistance (sRaw1) is equal to the product of thoracic gas volume (TGV) and the sum of the airway resistance (Raw) and the instrument resistance (Rins). If an additional resistance (Radd) is put in the breathing path, the measured specific, airway resistance (sRaw2) exceeds sRaw1 by the product of TGV and Radd and can be used for determining TGV. With the use of a device increasing Rins by a known amount (Radd) during normal breathing, sRaw1 and sRaw2 were measured in 3 normal subjects, 16 asthmatic patients, 2 patients with chronic obstructive pulmonary disease, and 1 patient with restrictive lung disease from the slopes of the x-y plots of airflow vs. box signals obtained before and after adding Radd. TGV was calculated by dividing (sRaw2-sRaw1) bu Radd. We also determined subjects' TGV by the panting method of A. B. DuBois, S. Y. Botelho, G. N. Bedell, and J. H. Comroe, Jr. (J. Clin. Invest. 35: 322-326, 1956) and functional residual capacity by the helium-dilution method. The results of the new method were quite reproducible (coefficient of variation = 5.6) and equivalent to those obtained by the other two methods.

Adolescent↗

PubMed1995

The effect of inhaled adrenaline on lung function of recurrently wheezy infants less than 18 months old.

Inhaled bronchodilators have been shown not to improve lung function in infants with wheeze. This observation has led to the suggestion that airway wall edema may be more important than bronchoconstriction in infants with airway narrowing. Inhaled adrenaline is used to relieve upper airway edema in children with croup and has been demonstrated to improve clinical scores and lower pulmonary resistance in some infants with wheeze associated with bronchiolitis. The aim of the present study was to examine the effect of inhaled adrenaline on lung function in a group of infants with recurrent wheeze. Eleven infants aged 10 to 18 months with a history of recurrent wheeze were studied during an asymptomatic interval. Respiratory function was assessed (1) by measuring maximal expiratory flow at functional residual capacity (VmaxFRC) during a forced partial expiratory maneuver and (2) by measuring conductance of the respiratory system (Grs) using a single expiratory occlusion technique. Following baseline measurements, the infants received 0.5 mg/kg adrenaline by nebulizer and serial lung function tests were repeated at 5 min intervals. Ten infants had abnormal baseline lung function (median VmaxFRC 44.2% predicted; median Grs 34% predicted). Using a random effects model, VmaxFRC and Grs declined significantly at 10 and 5 min after adrenaline, respectively. No significant improvements from baseline were observed in either measurement for up to 30 min following adrenaline delivery. It is concluded that inhaled adrenaline did not relieve airways obstruction in this group of asymptomatic infants with recurrent wheeze.

Administration, Inhalation↗

PubMed1990

Acute lung injury from mechanical ventilation at moderately high airway pressures.

We have explored adverse pulmonary effects of mechanical ventilation at a peak inspiratory pressure of 30 cmH2O in paralyzed and anesthetized healthy sheep. A control group of eight sheep (group A) was mechanically ventilated with 40% oxygen at a tidal volume of 10 ml/kg, a frequency of 15 breaths/min, a peak inspiratory pressure less than 18 cmH2O, and a positive end-expiratory pressure of 3-5 cmH2O. During the ensuing 48 h, there were no measurable deleterious changes in lung function or arterial blood gases. Another 19 sheep were ventilated with 40% oxygen at a peak inspiratory pressure of 30 cmH2O under a different set of conditions and were randomly assigned to two groups. In group B, the respiratory rate was kept near 4 breaths/min to keep arterial PCO2 in the normal range; in group C, the frequency was kept near 15 breaths/min by including a variable dead space in the ventilator circuit to keep arterial PCO2 near baseline values. There was a progressive deterioration in total static lung compliance, functional residual capacity, and arterial blood gases. After some hours, there were abnormal chest roentgenographic changes. At time of death we found severe pulmonary atelectasis, increased wet lung weight, and an increase in the minimum surface tension of saline lung lavage fluid.

Air Pressure↗

PubMed1981

Comparison of lung diffusing capacity during rebreathing and during slow exhalation.

In five normal sitting subjects DLCO and Qc were measured from the disappearances of a stable isotope of carbon monoxide (C18O) and of acetylene with respect to an inert and insoluble reference gas (Helium). Measurements were made during two respiratory maneuvers: (1) during rebreathing both at functional residual capacity (FRC) and near total lung capacity (TLC); and (2) during a slow exhalation at a constant rate from TLC to FRC. Changes in gas concentration were measured at the mouth during both maneuvers with a respiratory mass spectrometer. Mean DLCO was significantly higher during rebreathing near TLC (34.6 ml . min-1 . mm Hg-1) than near FRC (28.8 ml . min-1 . mm Hg). Mean DLCO measured during slow exhalation near FRC (32.7 ml . min-1 . mm Hg) was significantly higher than DLCO measured during rebreathing over the same volume range. Measurements of Qc were not significantly different between the rebreathing and slow exhalation maneuvers. Differences in DLCO between the two methods at FRC were not due to differences in Qc.

Adult↗

PubMed1976

Direct determination of surface tension in the lung.

We have used the spreading behavior of small drops of several fluorocarbon fluids and silicone oil on air-liquid interfaces to measure the surface tension of lungs in situ. The test fluids were calibrated in a surface balance at 37 degrees on monolayers of dipalmitoylphosphatidylcholine. At particular surface tensions characteristic of each fluid used, an increase in the tension of 1 mN/m or less caused the droplets to spread reversibly from a sphere to a lens shape. Using micropipettes we placed such droplets on the alveolar surfaces of excised rat lungs held at functional residual capacity and 37 degrees and found that the surface tension remained below 9 mN/m for at least 30 min. The surface tension-volume relationship was linear for tensions ranging from 9 to 20 mN/m.

Animals↗

PubMed1988

Numerical and experimental study of steady-state CO2 and inert gas washout.

The predictions of a single-path trumpet-bell numerical model of steady-state CO2 and infused He and sulfur hexafluoride (SF6) washout were compared with experimental measurements on healthy human volunteers. The mathematical model used was a numerical solution of the classic airway convention-diffusion equation with the addition of a distributed source term at the alveolar end. In the human studies, a static sampling technique was used to measure the exhaled concentrations and phase III slopes of CO2, He, and SF6 during the intravenous infusion of saline saturated with a mixture of the two inert gases. We found good agreement between the experimentally determined normalized slopes (phase III slope divided by mixed expired concentration) and the numerically determined normalized slopes in the model with no free parameters other than the physiological ones of upper airway dead space, tidal volume, breathing frequency, and breathing pattern (sinusoidal). We conclude 1) that the single-path (Weibel) trumpet-bell anatomic model used in conjunction with the airway convection-diffusion equation with a distributed source term is adequate to describe the steady-state lung washout of CO2 and infused He and SF6 in normal lungs and 2) that the interfacial area separating the tidal volume fron from the functional residual capacity gas, through which gas diffusion into the moving tidal volume occurs, exerts a major effect on the normalized slopes of phase III.

Carbon Dioxide↗

PubMed1977

Relationship of lung recoil to lung volume and maximum expiratory flow in normal children.

Thirty-one normal children, aged 6--18 yr, were studied by measurements of static lung volumes, static expiratory pressure-volume (PV) curves, and maximum expiratory flow-volume (MEFV) curves. A theoretical standard volume was used to compare children of differing size and this showed that total lung capacity (TLC) is also a valid standard volume. The shape of the PV curve was found to change so that static elastic recoil at a fixed proportion of TLC was higher in older than in younger children. This was also true of static recoil at functional residual capacity (FRC) and an associated increase in the ratio of FRC to TLC was interpreted as evidence for increase in outward recoil of the chest wall during childhood. Since static recoil at "closing capacity" (CC) remained constant, a decrease in the ratio of CC to TLC was quantitatively explained by the PV shift during childhood. Although maximum expiratory flow at various lung volumes increased in constant proportion to TLC, "upstream conductance" decreased relative to TLC. It was concluded that maturation of the respiratory system is disproportionate in several features during childhood and that these disproportions are likely to be even more prominent during infancy and early childhood.

Adolescent↗

PubMed1997

Pulmonary sequelae in infants treated with extracorporeal membrane oxygenation.

The decision to place an infant on extracorporeal membrane oxygenation (ECMO) is based on predictions of expected morbidity and mortality. One unknown factor is the relationship between pre-ECMO pulmonary dysfunction and on barotrauma and post-ECMO pulmonary sequelae. To determine whether placement of infants on extracorporeal membrane oxygenation (ECMO) early is associated with less subsequent pulmonary dysfunction than placing infants on EMCO later, we evaluated pulmonary function in 25 neonates prior to ECMO, when the infants had come off EMCO, and at the time of nursery discharge. Pulmonary resistance (R) and compliance (CL) were determined by a pneumotachograph and esophageal manometry, and functional residual capacity (FRC) was determined by a helium dilution method. Maximal expiratory flow (VmaxFRC) was determined by thoracic compression at the time of discharge. Infants were assigned to an early ECMO group (< 36 hours of age, n = 12), or a late ECMO group (> 36 hours of age, n = 13). When first evaluated, the early group had a higher oxygenation index than the late group (mean value, 63 versus 48), but initial pulmonary function measurements were not different between the two groups. In the early group mean CL increase from 0.20 to 0.36 ml/cmH2O/kg, FRC increased from 7 to 20 ml/kg, and mean R decreased from 107 to 61 cmH2O/L/sec between the initial study and immediately after ECMO. In the late group, only FRC increased from a mean of 8 to 20 ml/kg. CL and FRC increased from post-ECMO to discharge in both groups (mean CL from 0.36 to 0.76 ml/cmH2O/kg in the early group, and from 0.30 to 0.79 in the late group). Mean FRC increased from 20 to 26 ml/kg in the early group, and from 20 to 25 ml/kg in the late group. VmaxFRC was lower in the late than the early group at discharge (mean, 1.14 versus 1.58 L/sec; P < 0.05). While both groups of infants had minimal pulmonary dysfunction at discharge, the infants placed on ECMO early had evidence of slightly less airway dysfunction despite a higher initial oxygenation index than the infants placed on ECMO late.

Airway Resistance↗

PubMed2002

Relative ability of full and partial forced expiratory maneuvers to identify diminished airway function in infants with cystic fibrosis.

The tidal and raised volume rapid thoracoabdominal compression techniques are increasingly used to detect diminished airway function in infancy. The aim of this study was to assess the relative ability of parameters measured by these techniques to identify diminished airway function in infants newly diagnosed with cystic fibrosis (CF) with and without clinical evidence of prior lower respiratory illness. A cross-sectional, prospective study design was used in which maximal flow at functional residual capacity (VmaxFRC) from the tidal technique and FVC, FEV0.5, FEF75, and FEF25-75 from the raised volume technique were measured in 47 infants with CF and 187 healthy infants of similar body size, sex distribution, ethnic group, and exposure to maternal smoking. Multiple linear regression was used to assess group differences and to calculate SD scores for each parameter for the infants with CF. Airway function was also compared with clinical assessments of respiratory status made by pediatric pulmonologists. FEV0.5 was significantly diminished in 13 infants with CF, of whom 4 had been identified by clinicians as having normal respiratory status. Only one infant with CF had a VmaxFRC below the estimated normal range. Airway function is diminished in infants with CF irrespective of prior lower respiratory illness and in those whose respiratory status is considered normal by pediatric pulmonologists. In infants with CF, the raised volume technique identified diminished airway function more frequently than the tidal technique.

Age Factors↗

PubMed1978

Changes in pulmonary mechanics and gas exchange following thoracocentesis.

In nine patients with large pleural effusions, we studied the changes in pulmonary mechanics and gas exchange that occurred in the first three hours following removal of 600 to 1,800 ml of fluid by thoracocentesis. There was a small but significant increase in the functional residual capacity and total lung capacity but no change in residual volume and vital capacity. Calculated pulmonary shunt fraction did not change. We could not relate the subjective improvements noted by patients after thoracocentesis to the changes in pulmonary volumes or blood gas levels.

Adult↗

PubMed1983

Postural effects on gas exchange in infants.

In adults with unilateral lung disease, pulmonary gas exchange is better when the patients is positioned with the good lung dependent. We studied the effects of body position on gas exchange in 10 infants with unilateral lung disease by measuring transcutaneous oxygen and carbon dioxide pressures in the supine and right and left lateral positions. We also performed krypton lung scans and measured changes in thoracic gas volumes in four of the infants. Transcutaneous oxygen pressure (mean +/- S.E.) was greater with the good lung uppermost (82 +/- 7.6 mm Hg) than with the good lung dependent (73 +/- 7 mm Hg) (P less than 0.02) or in the supine position (78 +/- 7 mm Hg). There were no changes in transcutaneous carbon dioxide pressure. The proportion of ventilation to the good lung was greater with the good lung uppermost than with the good lung dependent (P less than 0.01) or in the supine position (P less than 0.02) (64 +/- 3, 46 +/- 6, and 59 +/- 7 per cent, respectively). There were no significant changes with position in functional residual capacity, tidal volume, or dynamic lung compliance. We conclude that oxygenation in infants with unilateral lung disease is best with the good lung uppermost--the reverse of what has been observed in adults.

Carbon Dioxide↗

PubMed2005

Morphometric deformations of small airways and alveoli under quasi-static inflation process.

Localized morphometric deformations of small airways and alveoli during respiration have many biomedical and physiological implications. We developed fast synchrotron radiation CT system to visualize the small airways and alveoli of an intact mouse lung without fixation and dehydration, and analyzed their localized morphometric deformations between functional residual capacity (FRC) and total lung capacity (TLC). In the diameter behavior, the averaged and range values were significantly larger for smaller airways (68.8%, range: 0.36-0.89) than larger airways (45.2%, range: 0.40-0.57). These results indicated that the airway did not deformed in same manner and that these morphological differences characterized the heterogeneous lung function.

Air Pressure↗