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Results for “Functional Residual Capacity”

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PubMed1991

Effect of a single inflation of the lungs on oxygenation during total extracorporeal carbon dioxide removal in experimental respiratory distress syndrome.

Respiratory distress syndrome (RDS) was modelled in rabbits using pulmonary lavage to remove surfactant. The stability of the resulting pressure-volume hysteresis of the lungs in vivo was studied with the aid of whole-body plethysmography during apnoeic oxygenation made possible by total extracorporeal carbon dioxide removal. Systemic oxygen delivery was measured as a function of the constant airway pressure during apnoea. In 6 subjects a single brief inflation of the lungs to 3.5 kPa resulted in a doubling of both expired lung volume (volume above functional residual capacity) and arterial oxygen partial pressure at an airway pressure of 0.65 kPa. These rises were well maintained for 40 min following the inflation. In a further 6 subjects with RDS single inflations permitted optimum systemic oxygen transport to occur at the low airway pressure of 0.3 kPa, similar to the optimum airway pressure in 6 healthy control subjects. Where pressure-volume hysteresis is present in RDS it can be exploited during apnoeic oxygenation, and probably during high frequency ventilation, to improve oxygenation by the use of infrequent single inflations of the lungs.

Animals↗

PubMed1990

Putative cerebral cortical involvement in the ventilatory response to inhaled CO2 in conscious man.

1. The response of the diaphragm to both transcranial magnetic stimulation and electrical phrenic nerve stimulation was studied in thirteen normal subjects under conditions of either a 'reflex' drive to ventilation with inhaled CO2 or during volitional ventilation of similar magnitude. 2. The induced compound action potential in the diaphragm was recorded using an oesophageal electrode, and in some cases transdiaphragmatic pressure was recorded using oesophageal and gastric balloon catheters. 3. The response of the diaphragm to transcranial magnetic stimulation was invariably facilitated with volitional inspiration; there was either minimal or no response at functional residual capacity. 4. Facilitation with inspiration was also seen during a 'reflex' drive to ventilation with inhaled CO2 in the presumed absence of any volitional contribution to ventilation. A similar degree of facilitation was seen with voluntary ventilation of similar magnitude and pattern. 5. If the facilitation is predominantly a cortical phenomenon, then these results imply that there is a behavioural component in the previously supposed purely 'reflex' drive to ventilation with inhaled CO2. We also discuss the interpretation of these results if some of the facilitation occurs at the phrenic motoneurone.

Action Potentials↗

PubMed1993

Pattern of lung volumes in patients with sighing breathing.

BACKGROUND: Sighing breathing is observed in subjects suffering from anxiety with no apparent organic disease. METHODS: Lung volumes and expiratory flow rates were measured in 12 patients with a sighing pattern of breathing and in 10 normal subjects matched for age, gender, and anthropometric data. In both groups the measurements were made by spirographic and plethysmographic techniques. In normal subjects functional residual capacity (FRC) and residual volume (RV) were measured during normal breathing and again during simulated sighing breathing to exclude technical artifacts resulting from hyperventilation during measurement by the helium closed circuit method. RESULTS: Patients with a sighing pattern of breathing had a normal total lung capacity (TLC) but significantly different partitioning of lung compartments compared with normal subjects. The vital capacity (VC) was lower when measured by both spirographic and plethysmographic methods and RV was higher. The forced expiratory volume in one second (FEV1) was also lower in patients with sighing breathing. The FEV1/VC and the maximal expiratory flow rates at 50% and at 25% of the forced vital capacity (V50 and V25) were normal and similar in both groups. In normal subjects there were no differences in RV when measured during quiet or simulated sighing breathing. CONCLUSIONS: Subjects with sighing breathing have a normal TLC with a higher RV and lower VC than normal subjects. There was no obvious physiological or anatomical explanation for this pattern.

Adult↗

PubMedDate not supplied

Partial expiratory flow-volume curves in infancy: technical aspects.

We have constructed a simple pressure-jacket with which to produce passive forced expiration in sleeping, supine infants by thoraco-abdominal compression. During expiration, flow and volume were measured at the airway opening with a face-mask and pneumotachograph. From partial expiratory flow-volume (PEFV) curves, peak expiratory flow rate (PEFR) and maximum expiratory flow at a lung volume equal to the functional residual capacity (VmaxFRC) were obtained. Using the jacket in groups of normal and wheezy infants, we have assessed the effects on PEFR and VmaxFRC of variable inflation pressure, rate and duration of jacket inflation, timing of chest compression in relation to the breathing cycle and subject interaction with the compression manoeuvre. The within-subject reproducibility of PEFR and VmaxFRC was measured. Consistent values were produced by inflating the jacket within 100 ms at end inspiration to a pressure of 3-4 kPa and maintaining the inflation (in wheezy infants) for at least 1 s. The median within-subject coefficients of variation of PEFR and VmaxFRC for both normal infants and wheezy infants were 9 and 12% respectively. The technique is clearly reproducible and can provide information about intrathoracic airway function in infancy.

Forced Expiratory Flow Rates↗

PubMed1986

Pulmonary epithelial clearance of 99mTc-DTPA after thrombin-induced pulmonary microembolism.

We investigated the effect of thrombin-induced pulmonary microembolism on the pulmonary clearance rate of aerosolized 99mTc diethylenetriamine pentaacetic acid (99mTc-DTPA) in awake, chronically prepared sheep. Chest activity was recorded after administration of a 0.44 micron aerosol of 99mTc-DTPA. Decay-corrected data were fit to an exponential and expressed as percent decrease per min (%/min). Sheep were given alpha-thrombin intravenously (80 U/kg for 10 min) 60 min after the aerosol administration. The clearance rate prior to alpha-thrombin was 0.35 +/- 0.05 %/min (mean +/- SEM). During alpha-thrombin administration, the clearance rate increased to 5.84 +/- 0.70 %/min (p less than 0.001 from baseline), but returned to 0.41 +/- 0.06 %/min within 30 min after the end of the thrombin infusion. The increased clearance rate during alpha-thrombin administration was not due to increased lung volume since alpha-thrombin did not change functional residual capacity. Moreover, the clearance rate was unchanged during gamma-thrombin administration, which does not induce coagulation, or during alpha-thrombin challenge in defibrinogenated animals. alpha-thrombin administration in neutrophil-depleted sheep caused a transient increase in DTPA clearance similar to that in control sheep, suggesting that the increase occurred independently of neutrophils. The results indicate that alpha-thrombin causes a large, transient increase in 99mTc-DTPA clearance, which may be the result of increased epithelial permeability. This response is dependent on the activation of intravascular coagulation.

Aerosols↗

PubMed1998

Impaired gas mixing and low lung volume in preterm infants with mild chronic lung disease.

The aim of this study was to assess the possible role of gas mixing inefficiency in spontaneously breathing infants with mild chronic lung disease (CLD) of prematurity in relation to changes in other functional parameters. A simple bedside technique for recording and analysis of multiple breath nitrogen washout curves was applied together with occlusion mechanics. Fifteen preterm infants with mild or moderately severe CLD were studied at a mean postconceptional age of 35 wk, together with 15 healthy preterm infants at the same maturity. All infants breathed spontaneously, and the test was performed by a continuous bypass flow system, connected to a face mask, a pneumotachograph, and a nitrogen meter. The results showed impaired gas mixing with moment ratios above the 95th percentile of the normal group in 11/15 infants with CLD. Functional residual capacity (FRC) was low in 13/15 infants, but specific compliance and resistance of the respiratory system did not differ between the groups. As FRC and moment ratios were not correlated, it is suggested that they may reflect different aspects of the pathophysiology in CLD. It is concluded that low FRC and disturbed gas mixing are characteristic disturbances in CLD at different degrees of severity. The multiple breath nitrogen washout test, followed by moment analysis of end-tidal nitrogen concentrations, is a simple and sensitive method for detection of these disturbances and for monitoring purposes.

Breath Tests↗

PubMed1989

Calibration of respiratory inductive plethysmograph during natural breathing.

We describe a single-posture method for deriving the proportionality constant (K) between rib cage (RC) and abdominal (AB) amplifiers of the respiratory inductive plethysmograph (RIP). Qualitative diagnostic calibration (QDC) is based on equations of the isovolume maneuver calibration (ISOCAL) and is carried out during a 5-min period of natural breathing without using mouthpiece or mask. In this situation, K approximates the ratio of standard deviations (SD) of the uncalibrated changes of AB-to-RC volume deflections. Validity of calibration was evaluated by 1) analyzing RIP waveforms during an isovolume maneuver and 2) comparing changes of tidal volume (VT) amplitude and functional residual capacity (FRC) level measured by spirometry (SP) with RIP values. Comparisons of VT(RIP) to VT(SP) were also obtained in a variety of postures during natural (uninstructed) preferential RC and AB breathing and with voluntary changes of VT amplitude and FRC level. VT(RIP)-to-VT(SP) comparisons were equal to or closer than published reports for single posture, ISOCAL, multiple- and linear-regression procedures. QDC of RIP in supine posture with comparisons to SP in that posture and others showed better accuracy in horizontal than upright postures.

Calibration↗

PubMed1987

Lung function in newborn infants with tachypnea of unknown cause.

Twenty-one infants with tachypnea (f greater than 60/min) lasting more than 2 h and diagnosed as mild respiratory disease or pulmonary maladaptation according to previously presented criteria were studied during the course of the disease and after clinical recovery. Lung physiology (total and alveolar ventilation, efficiency and distribution of ventilation, functional residual capacity, and lung mechanics) was studied in combination with clinical data. The pathophysiological findings were characterized by increased total ventilation but normal alveolar ventilation, reduced efficiency of ventilation but more even distribution of ventilation (nitrogen elimination pattern) during disease than after clinical recovery, hyperinflation, reduced dynamic lung compliance but unaffected specific lung conductance. Infants with low gestational ages were most severely affected and had longer duration of disease than full-term infants. Our findings suggest that this condition is caused by small airway disease. Disturbances in normal pulmonary adaptation with abnormal retention of lung fluid is the most probable cause.

Functional Residual Capacity↗

PubMed1994

Continued pulmonary recovery observed after discontinuing extracorporeal membrane oxygenation.

Extracorporeal membrane oxygenation (ECMO) is a valuable therapy for the treatment of reversible lung disease in neonates. Associated with this treatment, however, are risks for complications that increase with the duration of therapy. We evaluated alveolar-arterial oxygen tension difference P(A-a)O2 pulmonary compliance (CL), and functional residual capacity (FRC) in 20 infants immediately after ECMO was discontinued, and again 24 hours thereafter. We measured CL by pneumotachography and esophageal manometry and FRC by helium dilution. Mean (+/- SEM) values for CL and FRC increased (CL from 0.28 +/- 0.02 to 0.35 +/- 0.03 mL/cmH2O)/kg and FRC from 18.6 +/- 1.4 to 22.2 +/- 1.1 mL/kg; P < 0.05), and P(A-a)O2 and the oxygenation index (OI) decreased (200 +/- 19 to 169 +/- 14 mm Hg and 6.9 +/- 0.44 to 5.4 +/- 0.5, respectively; P < 0.02), over the 24 hour period following ECMO. Nineteen of 20 infants experienced improvement in at least two of these parameters. Improvements were found to be greatest in the infant with the worst lung function immediately after discontinuing ECMO, and in the ten infants who had not received pancuronium bromide for inducing skeletal muscle paralysis, following decannulation from ECMO. These data indicate that improvement in lung function following ECMO will generally continue over the 24 hour period following the termination of cardiopulmonary bypass, and that borderline pulmonary status may not preclude discontinuation of bypass therapy.

Extracorporeal Membrane Oxygenation↗

PubMed1980

Prostaglandin F-2 alpha functions as a local hormone on human airways.

Vasoactive hormones may be classified either as 'local' or as 'circulating', depending on whether they are or are not removed by the pulmonary circulation. Prostaglandin F-2 alpha is partially removed by the human pulmonary circulation. We examined the hypothesis that, with respect to the human lung, PGF-2 alpha functions as a local mediator. Prostaglandin F-2 alpha was given to normal and asthmatic subjects via both intravenous and aerosolized routes, and we measured specific airway conductance, spirometry, functional residual capacity, and closing volume. Aerosolized PGF-2 alpha induced significant changes of all measured parameters in both normals and asthmatics, while intravenous PGF-2 alpha-induced changes were limited to the FVC in both normals and asthmatics. The data suggest that intravenous PGF-2 alpha induced constriction of peripheral lung units. The greater sensitivity of the peripheral lung units of asthmatics versus normals to PGF-2 alpha, suggest that the increased sensitivity of airway smooth muscle of asthmatics versus normals to PGF-2 alpha is not restricted to the conducting airways, but extends to the smooth muscle of the peripheral lung units. The data is consistent with the hypothesis that, with respect to the lung, PGF-2 alpha functions as a local hormone, but, furthermore, suggest that, possibly of greater importance than the definition of a hormone as 'local' or 'circulating', is the definition of the intrinsic properties of the muscles on which the hormone is exerting its effects.

Adolescent↗

PubMed1987

The prone position improves arterial oxygenation and reduces shunt in oleic-acid-induced acute lung injury.

The arterial oxygen tension (PaO2) may increase when patients with the adult respiratory distress syndrome are turned from supine to prone. We sought to reproduce this observation in dogs with acute lung injury to study the physiologic mechanism by which the improvement in oxygenation might occur. Twenty anesthetized dogs were ventilated with a constant tidal volume (20 ml/kg) of 100% oxygen. Oleic acid (0.09 ml/kg) was injected into the right atrium while rotating the animals through 360 degrees in 4 stages. Animals in Group I (n = 5) remained supine for 10 to 120 min until the supine PaO2 fell below 200 mm Hg. Those in Group II (n = 4) were kept prone during this period. Dogs in Groups I and II were then turned supine or prone every 30 min 5 times. Cardiac output and pulmonary vascular pressures, functional residual capacity (helium dilution), and regional diaphragmatic motion (determined by dorsal and ventral diaphragmatic markers relative to markers on the chest wall seen on lateral chest radiographs taken at FRC and at end-inspiration) were obtained in each position. Eleven dogs were kept supine (Group III, n = 6) or prone (Group IV, n = 5) for 2 h after oleic acid infusion, after which intrapulmonary shunt (Qs/QT) and ventilation-perfusion heterogeneity were measured in the supine and prone positions using the multiple inert gas elimination technique.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗

PubMed1997

Respiratory mechanics and morphometric changes during pneumoperitoneum in normal rats.

Pneumoperitoneum may give rise to several respiratory changes; nevertheless, no comprehensive analysis of respiratory mechanics has been performed under this condition. Respiratory mechanics and thoracoabdominal morphometry were evaluated in six sedated, anaesthetized, paralysed, and mechanically-ventilated rats before (control) and during pneumoperitoneum. After airway occlusion at end-inspiration, respiratory system, pulmonary, and chest wall resistive pressures (deltaP1,rs, deltaP1,L and deltaP1,cw, respectively) and viscoelastic/inhomogeneous pressures (deltaP2,rs, deltaP2,L and deltaP2,cw, respectively) were determined. Total pressure changes (deltaPtot) were calculated as the sum of deltaP1 and deltaP2, yielding the values of deltaPtot,rs, deltaPtot,L and deltaPtot,cw, respectively. Respiratory system, lung, and chest wall static (Est,rs, Est,L and Est,cw, respectively), and dynamic elastances (Edyn,rs, Edyn,L and Edyn,cw, respectively), and the corresponding changes in elastance (deltaE) (calculated as Edyn-Est) were also obtained. Chest wall configuration both at functional residual capacity (FRC) and end-inspiration (FRC + tidal volume (VT)) was also evaluated in another four rats. Pneumoperitoneum significantly increased deltaPtot,rs, deltaPtot,cw, deltaP2,rs, deltaP2,cw, deltaErs, deltaEcw, Est,rs, Est,L and Est,cw. Lateral and anteroposterior diameters increased significantly, with the exception of lateral diameters at the level of crista iliaca. Cephalocaudal diameter and FRC decreased. In conclusion, pneumoperitoneum augments elastances and increases the pressure dissipated against viscoelasticity/inhomogeneity of the respiratory system and chest wall. These changes are related to a cephalad displacement of the diaphragm plus changes in thoracoabdominal configuration.

Animals↗

PubMed1983

[Effect of water immersion as a model of weightlessness on lung closing volume].

The effect of 7-day water immersion combined at night with head-down (6 degrees) tilting on the volumes of lung expiratory closing was examined in 6 healthy male test subjects, aged 25-35. During immersion they showed, along with a stable reduction of the lung vital and functional residual capacity (by 4.2 and 14.8%, respectively), an increase in the fraction parameters of the expiratory closing volumes. The increase in the closing volume (up to 40%) (P less than 0.05) was particularly distinct on immersion day 2. Subsequent changes indicated gradual recovery of the closing volumes and a decline in regional nonuniformity of lung ventilation. The time-course variations in the closing volumes may be attributed to an increase in the intrapulmonary blood volume at the early stage of adaptation to immersion and to a decrease in the nonuniformity of the ventilation-perfusion ratios.

Adult↗

PubMed1982

Variability, reproducibility and observer difference of body plethysmographic measurements.

The variability (coefficient of variation of five consecutive measurements), reproducibility (difference of results at 1 h and 24 h), and interobserver difference (independent reading of the tracings by two observers) of airways resistance (Raw) and static lung volumes (residual volume, functional residual capacity, total lung capacity) using a body plethysmograph were assessed in 14 healthy subjects and in 25 patients with various respiratory disorders. The variability was low for TLC (4-5%), moderate for FRC (7-8%) and high for Raw (28%). No significant changes of Raw or lung volumes were found for the groups at 1 h and 24 h. Between observers, a slight difference existed for FRC and Raw in normal subjects; the difference was higher (4.5% for FRC and 11% for Raw) and became significant in patients. The overestimation of Raw by observer 2 as compared to observer 1 was more important at larger values. The present findings call for caution when pooling results obtained by several observers in large-scale studies, or when comparing figures obtained by different technicians in the pulmonary function laboratory.

Adult↗

PubMed2001

Computed tomography assessment of positive end-expiratory pressure-induced alveolar recruitment in patients with acute respiratory distress syndrome.

Computed tomography (CT) assessment of positive end-expiratory pressure (PEEP)-induced alveolar recruitment is classically achieved by quantifying the decrease in nonaerated lung parenchyma on a single juxtadiaphragmatic section (Gattinoni's method). This approach ignores the alveolar recruitment occurring in poorly aerated lung areas and may not reflect the alveolar recruitment of the entire lung. This study describes a new CT method in which PEEP-induced alveolar recruitment is computed as the volume of gas penetrating in poorly and nonaerated lung regions following PEEP. In 16 patients with acute respiratory distress syndrome a thoracic spiral CT scan was performed in ZEEP and PEEP 15 cm H(2)O. According to the new method, PEEP induced a 119% increase in functional residual capacity (FRC). PEEP-induced alveolar recruitment was 499 +/- 279 ml whereas distension and overdistension of previously aerated lung areas were 395 +/- 382 ml and 28 +/- 6 ml, respectively. The alveolar recruitment according to Gattinoni's method was 26 +/- 24 g and no correlation was found between both methods. A significant correlation was found between PEEP-induced alveolar recruitment and increase in Pa(O(2)) only when recruitment was assessed by the new method (Rho = 0.76, p = 0.003), suggesting that it may be more accurate than Gattinoni's method.

Aged↗

PubMed1989

A correction formula for computing specific airway resistance from a single-step measurement.

Specific airway resistance (SRaw) is conventionally determined by multiplying the plethysmographically measured values of airway resistance and functional residual capacity (FRC). An alternative single-step method, which avoids the need for airway occlusion during determination of FRC, has been described by Dab and Alexander. The single-step method provides no correction for resistance or dead space of the apparatus and, as a result, systematically overestimates SRaw. Using 1,000 paired measurements, it was possible to compute a formula for correcting the single-step measurement. This correction formula can be adjusted and applied to measurements made in any laboratory. The unlimited applicability of the proposed correction has been demonstrated by 234 plethysmographic measurements made in the Pediatric Clinic in Rome.

Adolescent↗

PubMed1980

Analysis of pulmonary vascular interdependence in excised dog lobes.

The pressure-volume behavior of intraparenchymal extra-alveolar arteries and veins was measured at various lung inflation states by inflating and deflating the vasculatures with air. The vascular volumes at specific vascular pressures (Pv) and transpulmonary pressures (Ptp) were partitioned into components of axial length and cross-sectional area. An analysis of the interrelationships between the perivascular pressure (Px), the vascular pressure vs. cross-sectional area behavior, and the Ptp is presented. For in vivo values of Pv, at functional residual capacity, the vascular-parenchymal mechanical interaction was small and values of arterial and venous Px approximately Ppl. With increasing Ptp to 30 cmH2O, values of both the arterial and venous Px relative to Ppl (Px - Ppl) decreased to approximately -5 cmH2O, indicating that the magnitude of the vascular-parenchymal interaction with increasing Ptp is similar for both arteries and veins in the in vivo state. At any fixed Ptp, values of arterial and venous Px - Ppl decreased nearly linearly with decreasing vascular cross-sectional area. These results were generally consistent with a linear continuum elasticity solution relating stress and deformation in the perivascular parenchyma.

Animals↗

PubMed1988

Responses of pulmonary vagal mechanoreceptors to high-frequency oscillatory ventilation.

The discharge of 57 slowly adapting pulmonary stretch receptors (PSR's) and 16 rapidly adapting receptors (RAR's) was recorded from thin vagal filaments in anesthetized dogs. The receptors were localized and separated into three groups: extrathoracic tracheal, intrathoracic tracheal, and intrapulmonary receptors. The influence of high-frequency oscillatory ventilation (HFO) at 29 Hz on receptor discharge was analyzed by separating the response to the associated shift in functional residual capacity (FRC) from the oscillatory component of the response. PSR activity during HFO was increased from spontaneous breathing (49%) and from the static FRC shift (25%). PSR activity during the static inflation was increased 19% over spontaneous breathing. RAR activity was also increased with HFO. These results demonstrate that 1) the increased activity of PSR and RAR during HFO is due primarily to the oscillating action of the ventilator and secondarily to the shift in FRC associated with HFO, 2) the increased PSR activity during HFO may account for the observed apneic response, and 3) PSR response generally decreases with increasing distance from the tracheal opening.

Animals↗