SEARCH · PubMed Health

Results for “Functional Residual Capacity”

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

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

At least 1,081 records · Page 60Linked to original sources

PubMed1977

Cardiopulmonary readjustments during graded immersion in water at 35 degrees C.

Six normal male volunteers, aged 25 to 34, suspended vertically in a harness that allowed them to completely relax their postural muscles, were studied in four randomly ordered conditions, namely in air at 28 degrees C, and immersed in water at 35 degrees C to the level of the hips, the xiphoid, or the chin. In each situation, several variables were measured by noninvasive techniques. Cardiac output rose from 5.11 min-1 (air) to 8.31-min-1 (chin), the increase in each of the three steps being significant at the 0.001 level. Heart rate dropped from 76 to 68 min-1 (P less than 0.001) from air to xiphoid immersion, but appeared to rise again (P less than 0.02) during chest immersion. Functional residual capacity decreased marginally during lower limb submergence, and considerably in each of the following stages. Pulmonary capillary blood volume rose significantly only during abdomen immersion. The arterial-endtidal PCO2 difference was minimally reduced as water reached hip level and then remained steady. Mixed venous PO2 increased during abdomen submergence, and PVCO2, was unaltered throughout. Analysis of the step-to-step changes demonstrates that some variables are set by a combination of processes which may counteract each other, and explains the difference between results obtained by previous investigators.

Adult↗

PubMed1977

Regional intrapulmonary gas distribution in awake and anesthetized-paralyzed man.

Intrapulmonary distribution of ventilation/unit lung volume was studied in 28 volunteers in the sitting, supine, or right lateral decubitus position, either awake or anesthetized-paralyzed and mechanically ventilated. We found significant differences between the awake state and anesthesia-paralysis with mechanical ventilation in 1) intrapulmonary gas distribution, and 2) the vertical gradient of regional functional residual capacities for the subjects in the lateral decubitus position, but not for those in the sitting and supine positions. The effect of increasing the tidal volume on distribution of ventilation was significantly different 1) between the three body positions for a given state, and 2) between the two states for a given body position. The data suggest thoracoabdominal mechanics are different in the three body positions and that anesthesia-paralysis and mechanical ventilation may cause a different pattern of expansion of the respiratory system than spontaneous breathing in the awake state.

Adult↗

PubMed2003

Effect of posture on oxygenation, lung volume, and respiratory mechanics in premature infants studied before discharge.

OBJECTIVES: To determine if the prone versus the supine posture was associated with higher oxygenation levels in prematurely born infants before discharge, whether any such effect was explained by alterations in lung volume or respiratory mechanics, and if the changes were greater in oxygen-dependent infants. PATIENTS: Twenty infants (10 oxygen-dependent), median gestational age 30 (range: 27-32) weeks, were studied at a median postconceptional age of 35 weeks (range: 32-38 weeks). METHODS: On 2 successive days, infants were studied both supine and prone; each posture was maintained for 3 hours. Oxygen saturation was continuously monitored and at the end of each 3-hour period; compliance and resistance of the respiratory system and functional residual capacity (FRC) were measured. RESULTS: Overall, the median oxygen saturation and FRC were significantly higher in the prone position; compliance of the respiratory system and resistance of the respiratory system were not significantly affected by posture. Differences in oxygen saturation and FRC were significantly higher in the prone posture in the oxygen-dependent, but not the nonoxygen-dependent infants. CONCLUSIONS: Superior oxygenation in the prone posture in oxygen-dependent premature infants studied before discharge could be explained by higher lung volumes.

Functional Residual Capacity↗

PubMed1982

Laryngeal narrowing measured with low frequency sound.

We measured laryngeal resistance with 800 Hz sound in human subjects. 800 Hz sound was forced into the mouth and the intensities of sound above and below vocal cord were detected by two microphones on the anterior neck. Respiratory resistance (Rrs) was simultaneously measured by an oscillation method. When the subject voluntarily controlled the glottis aperture at functional residual capacity, the percent increase of difference of intensity of sound between two microphones (Y %) was curvilinearly proportional to the increase of Rrs (X) from the control state; Y = 20.8 X X 1.24. Since Rrs below the larynx was constant at a given lung volume, we could estimate the increase of laryngeal resistance from the control state by knowing the percent increase of difference of intensity of sound. The present method would be clinically applicable to measure Rrs independent from laryngeal artifact.

Adult↗

PubMed1993

Impaired respiratory function in infants with anterior abdominal wall defects.

Respiratory function at follow-up was assessed in 13 infants who had undergone surgical repair of an anterior abdominal wall defect. Six infants had exomphalos and seven had gastroschisis. The infants were delivered at a median gestational age of 36 weeks (range, 32 to 38 weeks). Respiratory function was assessed by measurement of functional residual capacity (FRC) at a median postnatal age of 5 months (range, 1 to 10 months). Although there was no significant difference in the FRC of the infants with gastroschisis compared with those with exomphalos, the study group's mean FRC (25 mL/kg) was significantly lower than that of 50 healthy control infants (mean, 30 mL/kg; 95% CI, +/- 6 mL/kg). Five infants had an FRC below the 95% confidence limit of the normal range. These data suggest that infants with anterior abdominal wall defects may have impaired antenatal lung growth.

Abdominal Muscles↗

PubMed1991

Relation between nocturnal symptoms and changes in lung function on lying down in asthmatic children.

Nocturnal symptoms are common in young asthmatic children. Such symptoms may be caused by increased impairment of lung function when they adopt the supine posture. Thirty one children aged 2.8-8.3 years were studied, of whom 20 had asthma (10 with frequent nocturnal symptoms) and 11 had no respiratory problems (control subjects). Peak expiratory flow (PEF) was measured with a Wright's peak flow meter and functional residual capacity (FRC) by a helium gas dilution technique after 30 minutes of lying supine; the values were compared with FRC measured sitting and PEF standing. Peak flow fell significantly on adoption of the supine posture in the asthmatic children, but there was no difference in this fall between the asthmatic children with and without nocturnal symptoms. FRC also fell on adoption of the supine posture, but the decrease in FRC was significant only in the control children and the asthmatic children without nocturnal symptoms. The failure to find a greater fall in PEF or a greater change in FRC on adoption of the supine posture among asthmatic children with nocturnal symptoms suggests that mechanisms other than increased impairment of lung function are responsible for nocturnal asthma.

Asthma↗

PubMed2006

Small airway changes in healthy and ovalbumin-treated mice during quasi-static lung inflation.

Previously, we developed a synchrotron radiation CT system to evaluate the morphometric changes (length and diameter, D) and small airway compliance (sC(aw)) of euthanized mice under quasi-static inflation [Sera, T., Uesugi, K., Yagi, N., 2005. Localized morphometric deformations of small airways and alveoli in intact mouse lungs under quasi-static inflation. Respir. Physiol. Neurobiol. 147, 51-63). Using this system, this study compared normal and asthmatic small airways. Ovalbumin-treated mice were used as an asthma model. Compared with the values at functional residual capacity, D of normal and asthmatic small airways (D<200microm) increased by 48% and 36% at the end of tidal inspiration. For larger airways (D>500microm), the increases were 23% and 20%, respectively. The ratio of the sC(aw) of asthmatic small airways to that of healthy small airways was 0.57, and the ratio was 0.70 for larger airways. The morphometric changes and sC(aw) in asthma model mice were significantly lower than those of healthy mice. The differences in sC(aw) between healthy and asthma model mice were greater for smaller airways.

Animals↗

PubMed1999

Paralysis of ventilated newborn babies does not influence resistance of the total respiratory system.

Paralysis with pancuronium bromide is used in newborn infants to facilitate ventilatory support during respiratory failure. Changes in lung mechanics have been attributed to paralysis. The aim of this study was to examine whether or not paralysis per se has an influence on the passive respiratory mechanics, resistance (Rrs) and compliance (Crs) of the respiratory system in newborn infants. In 30 infants with acute respiratory failure, Rrs was measured during paralysis with pancuronium bromide and after stopping pancuronium bromide (group A). Rrs was also measured in an additional 10 ventilated infants in a reversed fashion (group B): Rrs was measured first in nonparalysed infants and then they were paralysed, mainly for diagnostic procedures, and the Rrs measurement repeated. As Rrs is highly dependent on lung volume, several parameters, that depend directly on lung volume were recorded: inspiratory oxygen fraction (FI,O2), arterial oxygen tension/alveolar oxygen tension (a/A) ratio and volume above functional residual capacity (FRC). In group A, the Rrs was not different during (0.236+/-0.09 cmH2O x s x mL(-1)) and after (0.237+/-0.07 cmH2O x s x mL(-1)) paralysis. Also, in group B, Rrs did not change (0.207+/-0.046 versus 0.221+/-0.046 cm x s x mL(-1) without versus with pancuronium bromide). FI,O2, a/A ratio and volume above FRC remained constant during paralysis. These data demonstrate that paralysis does not influence the resistance of the total respiratory system in ventilated term and preterm infants when measured at comparable lung volumes.

Acute Disease↗

PubMed1999

[Algorithms for oxygenation and difficult intubations in obstetrics].

The obstetrical population is prone to difficult or failed intubation. Control of the airway is complicated by several factors specific to obstetric anesthesia; time of apnea is short due to a reduced functional residual capacity, pregnancy-induced hypertension and obesity are relatively frequent; anesthetist's skill can also be mentioned. The best approach to this problem lies in its prevention, using epidural analgesia as soon as possible. Furthermore, the number of difficult intubations can be considerably reduced by a thorough pre-anesthetic examine. Each anesthetist must keep an algorithm in mind, should a difficult or failed intubation in obstetrical patient. Whichever method is used (ventilation through a facial mask or laryngeal mask, transtracheal oxygenation), the anesthetist must never forget that the first priority is always the safety of the mother.

Algorithms↗

PubMed1993

Effect of salbutamol on histamine induced bronchoconstriction in healthy infants.

BACKGROUND: The effect of inhaled beta 2 adrenergic drugs on infants with wheezing disorders remains controversial. Salbutamol inhibits the bronchial responsiveness of infants to histamine and nebulised water but whether or not it acts as a bronchodilator in this age group is unclear. The aim of the present study was to determine whether salbutamol can hasten the reversal of histamine induced bronchoconstriction in infants. METHODS: Bronchial challenge with histamine was performed in 40 infants aged 12 months or less with no previous history of respiratory symptoms. Response to histamine was assessed by forced partial expiratory flow/volume curves to measure maximal flow at functional residual capacity (VmaxFRC). After a fall of 40% or more from baseline VmaxFRC, each infant was randomly assigned to receive either salbutamol 0.5% or saline 0.9% solution by nebuliser. The rate of recovery of VmaxFRC and the time to reach baseline VmaxFRC were derived by linear regression. RESULTS: Infants who received salbutamol had a significantly faster rate of recovery (geometric mean 8.5 ml/s/min) than those who received saline (4.1 ml/s/min). Considerable interindividual variation was observed in the time from maximum bronchoconstriction to recovery of baseline VmaxFRC in both groups of subjects. CONCLUSIONS: Salbutamol significantly speeds the reversal of histamine induced bronchoconstriction in infants during the first 12 months of life. This observation provides further evidence to support the presence of functional beta adrenergic receptors in the airways of infants.

Administration, Inhalation↗

PubMed1986

Effects of cognitive and psychomotor tasks on breath-holding span.

Bartlett (J. Appl. Physiol. 42: 717-721, 1977) demonstrated that a psychomotor task (hand dynamometer) extended breath holds at functional residual capacity (FRC) in a manner comparable to Valsalva and Mueller maneuvers. This led us to the hypothesis that distraction of a subject's attention from dyspneic sensations accounted for Bartlett's findings. This hypothesis was tested by comparing a hand dynamometer task (rubber-bulb squeeze) with a mental performance task (mental arithmetic). Results for tasks performed separately and concurrently in a within-subjects design showed comparable effects, without reaching a FRC breath-hold performance ceiling. Implications of results for effects of nonmechanical and nonchemical factors on respiratory drive are discussed.

Adolescent↗

PubMed1986

Steady-state response of normal subjects to inspiratory resistive load.

Tidal volume (VT) is usually preserved when conscious humans are made to breathe against an inspiratory resistance. To identify the neural changes responsible for VT compensation we calculated the respiratory driving pressure waveform during steady-state unloaded and loaded breathing (delta R = 8.5 cmH2O X 1(-1) X s) in eight conscious normal subjects. Driving pressure (DP) was calculated according to the method of Younes et al. (J. Appl. Physiol. 51: 963-989, 1981), which provides the equivalent of occlusion pressure at functional residual capacity throughout the breath. VT during resistance breathing was 108% of unloaded VT, as opposed to a predicted value of 82% of control in the absence of neural compensation. Compensation was accomplished through three changes in the DP waveform: 1) peak amplitude increased (+/- 23%), 2) the duration of the rising phase increased (+42%); and 3) the rising phase became more concave to the time axis. There were no changes in the relative decay rate of inspiratory pressure during expiration, in the shape of the declining phase of DP, or in end-expiratory lung volume.

Adult↗

PubMed1995

Pulmonary effects after surfactant treatment in premature infants with severe respiratory distress syndrome.

To understand the mechanisms behind the improved oxygenation after intratracheal surfactant instillation, the immediate effects of lung volume and pulmonary mechanics were analyzed. All infants studied were enrolled in multicenter trials in which surfactant therapy was instituted according to a rescue protocol. Infants received either synthetic surfactant (Exosurf) or modified porcine surfactant (Curosurf). Measurements of lung volume and pulmonary mechanics were successfully performed in 12 patients with a birth weight of 1.3 +/- (SD) 1.4 weeks. Functional residual capacity (FRC) and pulmonary mechanics were measured during mechanical ventilation. The FRC increased significantly by 70% (median), from 7.10 +/- (SD) 2.8 ml/kg to 11.5 +/- 3.3 ml/kg after surfactant instillation. However, a concomitant decrease in specific compliance was also seen. These findings could suggest that this immediate increase in FRC is initially nonuniform. However, since no significant correlation between changes in FRC and improvement in arterial-to-alveolar oxygen tension ratio is seen, other effects of surfactant must also be considered. These could include local and/or systemic changes in hemodynamics, such as decreased shunting as well as various effects on gas diffusion.

Functional Residual Capacity↗

PubMed1981

Pressure-volume and airway closure relationships in each lung in anaesthetized man.

Airway closure, functional residual capacity (FRC) and transpulmonary pressure-volume curves were assessed for each lung separately in the anaesthetized subject by means of a double lumen tracheal catheter. In the supine position airway closure occurred synchronously in the two lungs and 0.2-0.31 above FRC. The pressure- volume curves in both lungs were rather similar and critical closing pressure (CP) was approximately 3 cmH2O in each lung. In the left lateral posture, FRC was increased in the non-dependent and reduced in the dependent lung, while closing capacity (CC) remained unaltered. Airway closure was asynchronous and discontinuous between the two lungs. This was caused by the non-linear transpulmonary pressure-volume curve in the lungs, in conjunction with the vertical pleural pressure gradient. An interpulmonary "pendelluft" phenomenon was observed in the left lateral posture, increasing inhomogeneity of ventilation. It may depend on regional differences in compliance.

Adult↗

PubMedDate not supplied

The unreliability of indirect lung compliance in healthy subjects and patients with chronic lung disorders.

The clinical usefulness of lung compliance calculated indirectly was reassessed in a large number of healthy subjects and patients with chronic airflow obstruction or restrictive lung disorders. Indirect compliance was calculated from maximal expiratory flow-volume (MEFV) curve and airway resistance measured plethysmographically according to two approaches. In the first (approach A) all calculations were done at the functional residual capacity, whereas in the second (approach B) they were obtained over the 50-75% volume range of the forced vital capacity; values were compared to those of direct compliance measured concurrently. For the group as a whole, the correlations between indirect and direct values were poor regardless of the approach. Examined separately, the best correlations were found for the healthy group using approach A (r = 0.501) and for the obstructive group using approach B (r = 0.312). Failure to derive a valuable indirect compliance is due to the fact that there is a very poor correlation between upstream resistance and airway resistance measured by body plethysmography.U

Adult↗

PubMed2005

Measurement of neural respiratory drive in patients with COPD.

Assessment of neural respiratory drive may be useful in patients with chronic obstructive pulmonary disease (COPD) for diverse clinical and academic reasons. We hypothesised that the oesophageal diaphragm EMG during CO2 rebreathing and treadmill exercise could be used for this purpose. The oesophageal catheter consisted of nine consecutive recording electrode coils, which formed five pairs of electrodes with an inter-electrode distance 3.2 cm within a recording pair. Each coil was 1cm in length and the gap between adjacent coils was 0.5 mm. Maximal isometric contractions at functional residual capacity (FRC) and maximal voluntary inspirations from FRC to total lung capacity (TLC) were performed. All subjects performed CO2 rebreathing until end-tidal CO2 was approximately 9% or they became intolerably breathless. There was a good linear relationship between peak of root mean square (RMS) of the diaphragm EMG and end-tidal CO2 (r = 0.92 +/- 0.06) during CO2 rebreathing. The method was also shown to be feasible during exercise. It is concluded that the diaphragm EMG recorded from an oesophageal electrode is a useful technique to assess neural respiratory drive in patients with COPD.

Aged↗

PubMed1989

Detrimental effects of positive end-expiratory pressure during controlled mechanical ventilation of patients with severe airflow obstruction.

Positive end-expiratory pressure (PEEP) in treatment of asthma may be beneficial by dilating airways or detrimental by increasing hyperinflation. Several studies have reported beneficial results but with conflicting effects on lung volume. We studied the effects of PEEP on pulmonary hyperinflation, gas exchange, and circulation in six patients (59 +/- 19 yr, four men, two women) with severe airflow obstruction requiring mechanical ventilation (four with asthma, two with an exacerbation of chronic airflow obstruction). Three levels of PEEP (5, 10, and 15 cm H2O) were studied. All patients were paralyzed and ventilated with a tidal volume of 1.0 L, and respiratory rates (R) of 10, 16, and 22 breaths per min. End-inspiratory lung volume (VEI) or the degree of pulmonary hyperinflation above functional residual capacity (FRC) was quantified by measuring total exhaled gas volume during a period of apnea following steady-state tidal inspiration (1). Two patients were not studied at 15 cm H2O PEEP because of hypotension. Without PEEP, all patients showed gas trapping above FRC that increased progressively as R was increased (i.e., expiratory time decreased). At each R, increases in PEEP progressively increased FRC up to 1.42 +/- 0.43 L (mean +/- SD) at 15 cm H2O PEEP (n = 4) and progressively reduced the degree of gas trapping above the PEEP FRC.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Obstruction↗

PubMed1989

Low frequency oscillatory ventilation through the suction channel of a pediatric bronchoscope.

To determine whether low frequency oscillatory ventilation (LFOV) may be safely applied through the suction channel of a pediatric fiberoptic bronchoscope, we devised a system using a combination of jet ventilation and constant air suction, both delivered with a single interface valve. The system was tested on an in vitro lung model and on rabbits. With tidal volumes of 12 mL, inadvertent increase in functional residual capacity (FRC) measured in the lung model was minimal. All rabbits experienced marked hypoventilation (PaCO2 62 +/- 2 torr) on introduction of the bronchoscope, which promptly improved with administration of LFOV (PaCO2 41 +/- 4 torr). That baseline FRC remained stable indicated that air trapping did not occur. We conclude that LFOV improves ventilation in rabbits during bronchoscopy without causing air trapping. A similar system might be applied during bronchoscopy in full-term and premature infants, thus facilitating safer and more complete visualization of their airways and preserving the possibility of obtaining samples by suction.

Animals↗