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 1,117 records · Page 62Linked to original sources

PubMed1994

Effect of chest wall vibration on dyspnea in patients with chronic respiratory disease.

The effect of chest wall vibration on dyspnea at rest was investigated in 15 patients with severe chronic respiratory diseases. The magnitude of their baseline dyspnea was 17.9 +/- SE 3.3 mm on a 150-mm visual analog scale. One hundred hertz out-of-phase vibration (OPV; inspiratory intercostal muscles vibrated during expiration and expiratory intercostal muscles vibrated during inspiration) increased dyspnea an average of 21.9 +/- SE 7.8 mm (p < 0.05). One hundred hertz in-phase vibration (IPV; inspiratory intercostal muscles vibrated during inspiration and expiratory intercostal muscles vibrated during expiration) decreased dyspnea an average of 6.9 +/- SE 2.8 mm (p < 0.05). Changes in the respiratory pattern and arterial blood gas determinations elicited by 5-min IPV were investigated in eight of the 15 patients. Tidal volume was significantly increased in all eight of these patients. Respiratory frequency was decreased in seven patients and increased in one. Functional residual capacity, measured before and during the application of IPV for a period of about 10 breaths, was increased in one patient and decreased in the remaining seven. PaCO2 decreased by 1.3 +/- 1.0 mm Hg (p < 0.05), from 49.6 +/- 8.4 mm Hg; PaO2 increased by 3.4 +/- 2.3 mm Hg (p < 0.05), from 67.7 +/- 12.7 mm Hg. The results indicate that in-phase chest wall vibration decreased pathologic dyspnea in patients with chronic respiratory disease and suggest that the effects on respiratory sensation are mediated by afferent information from chest wall respiratory muscles to supraspinal centers.

Aged↗

PubMed1982

The effects of inspiratory muscle training in patients with cystic fibrosis.

This study evaluated whether inspiratory muscle training (IMT) could increase inspiratory muscle strength and endurance and exercise performance in 11 patients with cystic fibrosis (CF) with moderately severe airflow limitation. The IMT consisted of breathing through an inspiratory resistance (IR) for 15 min twice daily for 4 wk, preceded or followed by a 4-wk control period. After IMT, there was an increase in inspiratory muscle strength measured by maximal inspiratory mouth pressure at functional residual capacity: 74 +/- 18 cmH2O before training to 81 +/- 12 cmH2O after training, mean +/- 1 SD, p less than 0.025, and in inspiratory muscle endurance measured by the maximal IR tolerated for 10 min. Limitation of performance in the progressive exercise test was related to increased airflow limitation and possibly to poor nutrition. Mean exercise performance during progressive or submaximal exercise testing did not change after training. It is concluded that this form of IMT improved inspiratory muscle strength and endurance, but had little effect on exercise performance in patients with CF.

Adolescent↗

PubMed1976

Respiratory mechanics in normal hamsters.

Lung volumes and quasi-static deflation volume-pressure relationships were measured in male golden hamsters anesthetized with pentobarbital. Volume was measured with a pressure plethysmograph, and pleural pressure was estimated by the use of a water-filled esophageal catheter. Mean body weight +/- SE was 122.3 +/-3.0 g, mean lung weight was 0.74 +/- 0.2 g or about 0.6% of body weight. Mean lung volume at 25 cmH2O transpulmonary pressure (TLC25) was 7.2 +/- 0.14 ml, 9.78 +/- 0.17 ml/g lung weight or 5.92 +/- 0.06 ml/100 g body weight. Mean functional residual capacity was 2.4 +/- 0.06 ml or 33.3% of TLC25. Mean vital capacity was 5.2 +/- 0.13 ml. Mean quasi-static compliance of lung was 0.63 +/- 0.03 ml/cmH2O. Chord compliance of chest wall between lung volumes of 1 and 4 ml above RV was 3.39 +/- 0.53 ml/cmH2O. At FRC, the chest wall recoiled inward, so that pleural pressure was positive (1.4 +/- 0.13 cmH2O) and the lung was resisting further collapse. The slope of the lung's deflation volume-pressure curve changed at FRC, ERV was small (0.36 +/- 0.03 ml), and RV was determined by complete airway closure. Thus the mechanisms determining FRC are unusual and include an influence of airway closure.

Animals↗

PubMed1994

Abnormalities of lung volume at follow-up after antenatal rhesus iso-immunization.

Rhesus iso-immunization is associated with fatal pulmonary hypoplasia. We have examined the hypothesis that abnormalities of lung volume, as an index of lung growth, may also be found in survivors. At a median age of nine months, lung volume was assessed by measurement of functional residual capacity in 23 patients affected antenatally by rhesus iso-immunization. Seventeen of the patients had required at least one intrauterine transfusion. Five patients (group A) had an FRC < 24 ml/kg (median 21 ml/kg, range 19-22 ml/kg) and the other 18 (group B) an FRC > or = 24 ml/kg (median 27 ml/kg, range 24-36 ml/kg) (p < 0.01). The only significant difference between these two groups was the timing of the first foetal blood sampling and intrauterine transfusion, being a median of 22 weeks (range 20-23 weeks) in group A and 30 weeks (range 17-36 weeks) in group B (p < 0.01).

Blood Transfusion, Intrauterine↗

PubMed1978

Effect of lung volume on expiratory time in the newborn infant.

The effect of an increased end-expiratory lung volume on inspiratory and expiratory duration was examined in 13 term infants at 4, 30, and 70 h of age. This was accomplished by the administration of a continuous positive airway pressure (CPAP) of 0, 3, and 6 cmH2O by use of a face mask connected to a pneumotachometer, and by measurement of the timing of the respiratory cycle over 1-min intervals. At increasing functional residual capacity (FRC) there was a progressive increase in expiratory time (TE) and fall in respiratory rate, with a variable effect on inspiratory time (TI). As CPAP increased from 0 to 6 cmH2O, the TI/TE ratio fell from 0.75 to 0.62 (P less than 0.01), 0.90 to 0.66 (P less than 0.001), and 0.87 to 0.64 (P less than 0.001) at 4, 30, and 70 h, respectively. We conclude that alterations in end-expiratory lung volume significantly alter expiratory duration in the newborn infant at term. This may be analogous to the vagally mediated tonic control of expiratory time with changing FRC recently described in anesthetized animals.

Functional Residual Capacity↗

PubMed1990

Bronchial responsiveness to histamine in infants and older children.

Normal infants have been shown to respond to a relatively low concentration of inhaled histamine. However, those studies used partial maximal expiratory flow volume (PMEFV) curves to assess lung function. In order to directly compare responsiveness between infants and older children, we compared bronchial responsiveness to histamine between a group of 45 normal infants, median age 4 wk (range 2 to 6 wk) and a group of 30 nonasthmatic older children, median age 10 yr (range 5 to 15 yr) using PMEFV curves in both groups to assess lung function. In the infant group, PMEFV curves were generated using the forced expiratory flow volume technique. For the older children, PMEFV curves were generated by voluntary effort. The provocative concentration of histamine that produced a 40% fall (PC40) in maximum flow at functional residual capacity (VmaxFRC) was calculated from the PMEFV curves. The geometric mean PC40 of the infants (1.02 g/L) was lower than the geometric mean of the older children (3.4 g/L) (p less than 0.001). However, these results were then corrected for dilution of the aerosol due to air entrainment (AE). Corrected values of PC40 were not significantly different between infants and older children. These results demonstrate the importance of accounting for AE in the evaluation of histamine responsiveness and suggest that bronchial responsiveness may be similar in normal infants and older children.

Adolescent↗

PubMed1985

Managing chronic airflow obstruction: Part I.

The term "senile emphysema" has been largely abandoned. The lungs do, however, tend to lose their elastic recoil with age. The alveolar ducts enlarge, and the alveolar surface area decreases with age. Total lung capacity does not increase, but the residual volume and functional residual capacity do, with a concomitant decrease in vital capacity. The concern about lung cancer in these patients should be great, as the prevalence for that condition overlaps that of CAO. A routine chest roentgenograph and sputum samples for cytologic examination are the most commonly used techniques to diagnose lung cancer.

Adult↗

PubMed1987

Cardiovascular effects of patent ductus arteriosus in preterm lambs with respiratory distress.

We created a model for studying the cardiovascular and pulmonary effects of patent ductus arteriosus (PDA) in premature lambs with respiratory distress. In 47 fetal lambs at 129 to 133 days gestation (term, 145 days), we infiltrated the ductus arteriosus with formalin and placed a mechanical occluder about it so that its patency could be regulated. Two days later the lambs were delivered, given sheep surfactant, paralyzed, and their lungs mechanically ventilated. These premature lambs could more than double their left ventricular output when challenged with increasing degrees of left-to-right shunts through the PDA. This was accomplished by an increase in stroke volume, not by an increase in heart rate. During the 40-minute observation period, there was no change in dynamic compliance or functional residual capacity while the ductus was patent. When the ductus was patent, there was a significant increase in arterial PaO2 (even with small left-to-right shunts) and a decrease in PaCO2 (with large shunts). Despite the heart's ability to handle the increased volume load of a PDA, there were significant alterations in individual organ blood flows, resulting from a combination of decreased perfusion pressure and localized vasoconstriction. The abdominal organs had significant reductions in blood flow even with small PDA shunts. This decrease in organ blood flow may explain some of the pathophysiologic manifestations of PDA in preterm infants.

Animals↗

PubMed1992

Inhaled sodium cromoglycate for pre-term children with respiratory symptoms at follow-up.

Children born prematurely frequently have recurrent respiratory symptoms at follow-up and benefit from bronchodilator therapy. We have assessed if regular inhaled sodium cromoglycate would reduce this respiratory morbidity and need for bronchodilator therapy. Sixteen symptomatic children (median gestational age 29 weeks, post-natal age 15 months) were entered into a randomized double-blind, placebo-controlled trial. In two 3-week periods, the patients received either placebo or sodium cromoglycate (5 mg) as one puff q.d.s. from an inhaler via a coffee cup. Parents recorded their child's symptoms and need for bronchodilator therapy throughout and lung function was assessed by measurement of functional residual capacity (FRC) at the beginning and end of each 3-week period. The symptom score was reduced by 49% in the active compared to the placebo period (P less than 0.01) and bronchodilator was taken on a mean of 2.9 days per infant in the active period compared to 7.9 days in the placebo period (P less than 0.01). There was a significant improvement in FRC in ten of 16 patients over the active period but only in two infants over the placebo period (P less than 0.01). We conclude regular inhaled sodium cromoglycate is useful prophylaxis for symptomatic pre-term children.

Administration, Inhalation↗

PubMed1989

Effects of abdominal opening on respiratory system mechanics in ventilated rats.

In 16 anesthetized paralyzed mechanically ventilated rats, respiratory system mechanics and rib cage dimensions were determined both before and after wide abdominal opening. In eight animals the end-inflation occlusion method disclosed statistically significant postoperative increases in respiratory system elastance (from 4.84 to 6.49 cmH2O.ml-1) and resistance (from 0.224 to 0.300 cmH2O.ml-1.s); the latter resulted from a rise of its uneven component (from 0.161 to 0.209 cmH2O.ml-1.s). In the remaining rats, rib cage morphometry at functional residual capacity after surgery showed significant decreases in lower rib cage circumference and anteroposterior and lateral diameters, whereas there was an increase in upper rib cage circumference and a fall in its lateral diameter. When these parameters were measured at end-inspiratory lung volume, the difference between intact and open abdomen were less striking; only lower rib cage circumference and upper rib cage lateral diameter significantly decreased postoperatively. Because surgery induced an expiratory volume of only 0.1 ml, it can be concluded that abdominal opening redistributed regional volumes within the lung, leading to increased unevenness in the system.

Abdomen↗

PubMed1996

Pulmonary hyperinflation a clinical overview.

Pulmonary hyperinflation is usually defined as an abnormal increase in functional residual capacity, i.e. lung volume at the end of tidal expiration. As such, it is virtually universal in patients with symptomatic diffuse airway obstruction. Hyperinflation inferred from a standard chest radiograph implies an increase in total lung capacity. The relaxation volume of the respiratory system (Vr) increases in patients with chronic airway disease as a result of changes in the elastic properties of the lungs and chest wall. In addition, a variable degree of dynamic hyperinflation may be present. This results from the onset of inspiration before lung volume has fallen to Vr. Dynamic hyperinflation is frequently present at rest in patients with moderate-to-severe airway obstruction, and it increases further on exercise, thereby increasing the mechanical load on the inspiratory muscles and at the same time reducing their mechanical advantage. Important clinical consequences and associations of hyperinflation include: distortions of chest wall motion; impaired inspiratory muscle function; increased oxygen cost of breathing; greater likelihood of hypercapnia; impaired exercise performance; and greater severity of breathlessness. The symptomatic improvement after treatment with a bronchodilator may be due, in part, to lessening of hyperinflation.

Exercise Tolerance↗

PubMed1995

[Measurement of the reserve function of inspiratory muscle and its clinical significance].

The principles of measuring inspiratory muscle tension-time index (TTim) and the ratio of the works of inspiration over the maximal works of inspiration (Wi/Wi(max)) were investigated and their formulae were deduced, i.e. TTim = (Pi x Ti)/(MIP x Ttot) and Wi/Wi(max) = (Pi x VT)/(MIP x IC). The importance of the inspiratory pressure and the maximal inspiratory pressure (MIP) measured at function residual capacity (FRC) level was emphasized. Both TTim and Wi/Wi(max) were measured in 35 normal subjects and 89 patients with chronic obstructive pulmonary disease (COPD). The results showed that normal value of TTim was 0.0253 +/- 0.0055 which corresponds to the normal value of the diaphragm tension-time index (TTdi = 0.02-0.03) reported by Bellemare. Patients with COPD had a mean TTim much higher than that of normals (P < 0.01). The works of inspiration (Wi) in patients with COPD increased, while the maximal works of inspiration (Wi(max)) declined, so Wi/Wi(max) became significantly greater than that of normals (P < 0.01). The results also showed that there was a linear relationship between Pi/Pimax and TTim or Wi/Wimax (r = 0.7891, 0.9738, 0.6459, 0.9327, P < 0.01). Therefore, we suggest that both TTim and Wi/Wimax can be used as clinical indices to reflect the reserve function of inspiratory muscles.

Adult↗

PubMed1998

Respiratory work in elastase treated hamsters.

Biomechanical adaptations of the diaphragm in the hamster model of emphysema are similar to those observed in skeletal muscle with exercise training. The aim of this study was to evaluate whether the dynamic pressure-volume (PV) work of breathing in hamsters with elastase-induced emphysema may contribute to these adaptations. PV work in elastase treated animals was compared to healthy controls. The studies were performed in adult hamsters 14-16 months following intratracheal administration of elastase (elastase treated group, ET) or saline (control group, CTL). Airway and esophageal pressures and air flows were measured during spontaneous breathing in anesthetized, supine animals. Pulmonary work (WL) was computed from transpulmonary pressures and airflows. Functional residual capacity (FRC) and total lung capacity (TLC; defined as volume at 25 cmH2O) in ET were increased 2 and 1.8 times, respectively, compared with CTL. Averaged tidal volume (VT) and inspiratory flows were comparable between groups. Total work of breathing (WT) normalized per ml VT was not significantly affected with elastase treatment but the pulmonary elastance work (WE) was significantly less in ET animals than controls (0.88 +/- 0.61 g cm(-2) vs. 1.63 +/- 0.32). Pulmonary resistive work was not significantly different between ET and CTL animals. These results suggest that biomechanical adaptations of the diaphragm observed in ET hamsters are caused by mechanisms other than the changes in dynamic mechanical properties of the lung following elastase treatment.

Animals↗

PubMed1986

Intrapulmonary gas distribution in healthy children.

Distribution of ventilation was evaluated in 54 healthy children (24 boys and 30 girls), aged 7-16 years by multibreath nitrogen washout (MBNW) curves, from which the moment ratios (m1: m0, m2: m0), the lung clearance index, the Becklake index and the ventilatory efficiency index (E 90%) was computed. Functional residual capacity (FRC) was calculated from the washout curve and compared with the thoracic gas volume (TGV) plethysmographically determined, as well as with the FRC determined by helium dilution. The study shows that MBNW can easily be performed during spontaneous breathing in children and provides specific indices of ventilation. These indices show no sex difference and are age-independent. Therefore, the data of the present study contradict some previous indirect findings suggesting that the distribution of air in the lungs would become more even with age. There are in contrast more convincing direct measurement data showing that airways grow isotropically relative to the lungs.

Adolescent↗

PubMed1980

The role of respiratory muscles in the hyperinflation of bronchial asthma.

To examine the mechanism of hyperinflation in bronchial asthma we studied lung and chest wall mechanics in 7 asymptomatic patients in whom progressive bronchoconstriction was induced by doubling the amount of inhaled aerosolized histamine. An increase in pulmonary resistance (RL) from 2.5 +/- 0.3 cmH2O . 1-1 . s (mean, +/- 1 SE) to 12.3 +/- 0.9 cmH2 was associated with a linear increase in functional residual capacity (FRC) up to 74.7 +/- 1.7% of control total lung capacity (TLCc). The mean regression coefficient was 2.3% TLCc . cmH2O-1 . 1 . s-1. At each level of hyperinflation the most positive expiratory pleural pressures measured during spontaneous breathing were generally less than the predicted chest wall relaxation pressures, indicating persistent inspiratory muscle contraction throughout expiration. This was predominantly due to inspiratory intercostal and accessory muscle activity, because measurements of transdiaphragmatic pressure indicated complete diaphragmatic relaxation early in expiration. Recruitment of abdominal muscles during expiration, inferred from measurements of gastric pressure (Pg) and abdominal antero-posterior (A-P) diameter, was progressively more apparent with increasing bronchoconstriction. We concluded that the increase in FRC in induced asthma is substantially influenced by persistent inspiratory intercostal and accessory muscle activity during expiration. Concomitant abdominal muscle recruitment results in a chest wall configuration that tends to optimize diaphragmatic function.

Abdomen↗

PubMedDate not supplied

Pulmonary effects of ventilatory pattern following cardiopulmonary bypass.

Twenty-one patients who underwent cardiopulmonary bypass for myocardial revascularization received postoperatively controlled mechanical ventilation (CMV) or intermittent mandatory ventilation (IMV), with or without positive end-expiratory pressure (PEEP). Functional residual capacity (FRC), right-to-left intrapulmonary shunt, dynamic compliance, physiological dead space, and arterial and mixed venous blood gases were measured during mechanical ventilation and spontaneous ventilation following weaning. Controlled ventilation increased physiological dead space and arterial pH. FRC correlated positively with dynamic compliance, but not with right-to-left intrapulmonary shunt. Postoperatively, FRC was significantly lower than normal when patients were ventilated without PEEP, but was normal when patients received PEEP. Arterial oxygen tension (PaO2), intrapulmonary shunt, and dead space were unaffected in spite of higher FRC, suggesting that patients who received PEEP had fewer atelectatic and fewer unperfused "silent" lung units than those who had not received PEEP.

Cardiopulmonary Bypass↗

PubMed1994

Changes in regional ventilation during histamine bronchial challenge in stable asthma.

Our objective was to examine the changes in regional ventilation during histamine-induced bronchoconstriction in stable asthma. We measured regional ventilation by a new method which measures regional distribution of inhaled 127Xe during tidal breathing by a gated method and, by simultaneously measuring 99mTc counts from labelled macroaggregates, allowed for changes in lung shape during the breathing cycle. We studied 10 asthmatic patients [forced expiratory volume in 1 s (FEV1 2.04-4.37 litres)] and measured, in addition to the regional ventilation, oxygen saturation (SaO2), minute ventilation (VE) and tidal volume (Vt) before and after inhaling enough histamine to lower FEV1 by > 20% and/or SaO2 by > 4%. Histamine inhalation reduced FEV1 by 0.44-1.15 liters and SaO2 by 0-4%. It increased VE and functional residual capacity (FRC) in 8 of the 10 patients. The FEV1 fall did not correlate with the SaO2 fall, VE or FRC changes. Histamine inhalation increased apical ventilation in most patients, but the changes in regional ventilation in the left and right lungs were asymmetrical in 17 out of the 30 lung regions studied (upper, middle and lower paired regions in 10 patients). These results demonstrate that histamine bronchial challenge causes uneven regional ventilation. Any resultant change in ventilation-perfusion balance may be the underlying mechanism of oxygen desaturation seen in this procedure and in spontaneous attacks of asthma.

Adult↗

PubMed2003

Atelectasis causes vascular leak and lethal right ventricular failure in uninjured rat lungs.

During mechanical ventilation, lung recruitment attenuates injury caused by high VT, improves oxygenation, and may optimize pulmonary vascular resistance (PVR). We hypothesized that ventilation without recruitment would induce injury in otherwise healthy lungs. Anesthetized rats were ventilated with conventional mechanical ventilation (VT 8 ml/kg; respiratory frequency 40 per minute) and 21% inspired oxygen, with or without a recruitment strategy consisting of recruitment maneuvers plus positive end-expiratory pressure, in the presence or absence of a laparotomy. Additional experiments examined the impact of atelectasis on right ventricular function using echocardiography, as well as functional residual capacity and PVR. Lack of recruitment resulted in reduced overall survival (59% nonrecruited vs. 100% recruited, p < 0.05), increased microvascular leak, greater impairment of oxygenation and lung compliance, increased PVR, and elevated plasma lactate. Echocardiography demonstrated that right ventricular dysfunction occurred in the absence of recruitment. Finally, samples from nonrecruited lungs demonstrated ultrastructural evidence of microvascular endothelial disruption. Although such effects clearly do not occur with comparable magnitude in the clinical context, the current data suggest novel mechanisms (microvascular leak, right ventricular dysfunction) whereby derecruitment may contribute to development of lung injury and adverse systemic outcome.

Animals↗