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Results for “Functional Residual Capacity”

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PubMed2006

Respiratory function of very prematurely born infants at follow up: influence of sex.

OBJECTIVE: To test the hypothesis that male compared with female prematurely born infants would have worse lung function at follow up. DESIGN: Prospective follow up study. SETTING: Tertiary neonatal intensive care units PATIENTS: Seventy six infants, mean (SD) gestational age 26.4 (1.5) weeks, from the United Kingdom oscillation study. INTERVENTIONS: Lung function measurements at a corrected age of 1 year. MAIN OUTCOME MEASURES: Airways resistance (Raw) and functional residual capacity (FRC(pleth)) measured by whole body plethysmography, specific conductance (sGaw) calculated from Raw and FRC(pleth), and FRC measured by a helium gas dilution technique (FRC(He)). RESULTS: The 42 male infants differed significantly from the 34 female infants in having a lower birth weight for gestation, requiring more days of ventilation, and a greater proportion being oxygen dependent at 36 weeks postmenstrual age and discharge. Furthermore, mean Raw and FRC(pleth) were significantly higher and mean sGaw significantly lower. After adjustment for birth and current size differences, the sex differences in FRC(pleth) and sGaw were 15% and 26% respectively and remained significant. CONCLUSION: Lung function at follow up of prematurely born infants is influenced by sex.

Airway Resistance↗

PubMedDate not supplied

Respiratory function in infancy following pleuro-amniotic shunting.

Respiratory status was assessed at a median of 12 (range 3-60) months in 17 infants who had undergone pleuro-amniotic shunting to drain fetal pleural effusions. The shunts had been inserted at a median of 29 weeks (range 21-35) gestation; 12 fetuses were hydropic at the time of shunting. In all 17 cases effective chronic drainage of the pleural effusions was achieved. Respiratory status at follow-up was assessed by documentation of respiratory symptoms and measurement of functional residual capacity (FRC) by a helium gas dilution technique. Six infants suffered from recurrent respiratory symptoms, this incidence (37%) did not differ significantly from that found in a control group. The mean FRC of the study population was 28 ml/kg (range 19-34 ml/kg), only 2 infants' FRCs were below the reference range. These results suggest that pleuro-amniotic shunting may, be effective drainage of pleural effusion and hence prevention of chronic antenatal intrathoracic compression, avoid impairment of antenatal lung growth.

Amnion↗

PubMed2002

Abnormal lung function in healthy preterm infants.

The aim of this study was to assess the consequences of preterm birth for the functional development of the lungs. We studied 32 healthy preterm infants (gestational age 25 to 33 wk at birth) and 53 healthy full-term infants (37 to 42 wk) at the same mean postmenstrual age of 40 wk with a multibreath nitrogen washout technique to assess functional residual capacity (FRC), gas mixing efficiency, and dead space and with the single-breath occlusion technique to calculate compliance and resistance of the respiratory system. Twenty of the preterm infants were also assessed with the same methods at 34.2 (32 to 37) wk. At the same postmenstrual age the preterm infants had lower FRC/kg body weight, lower specific compliance, impaired gas mixing efficiency, and higher total and dead space ventilation/kg than the full-term infants. Specific compliance and specific conductance decreased but gas mixing efficiency increased from 34 to 40 wk. We conclude that premature exposure to extrauterine conditions changes lung function. Preterm infants showed signs of dysfunction of the terminal respiratory units and higher elastic recoil than infants who spent the corresponding time for development in utero. It is suggested that preterm birth per se affects alveolarization and formation of elastic tissue in the lungs.

Airway Resistance↗

PubMed2001

Characterisation of the Hering-Breuer deflation reflex in the human neonate.

Human infants have been observed making inspiratory efforts in response to chest compression. These may be a manifestation of the Hering-Breuer deflation reflex. We sought to stimulate the reflex in 33 term infants by rapidly reducing lung volume using an inflatable jacket. The effect of altering the timing, magnitude or rate of application of the lung deflation on the strength of the inspiratory response was investigated. Inspiratory effort was quantified by measuring (1) the rate of fall in oesophageal pressure on inspiration; and (2) the mean inspiratory flow (MIF) in response to lung deflation. Variables which significantly affected (1) and resulted in increased inspiratory effort were, in order of importance: larger rises in oesophageal pressure on chest compression (38%) (percentage of variance explained), greater reductions in lung volume below functional residual capacity (FRC) (26%), faster rates of lung deflation (19%) and slower respiratory rates (11%). Increased inspiratory efforts, as assessed by response (2), were generated by greater reductions in FRC (23%), larger rises in oesophageal pressure (11%) and faster rates of lung deflation (10%). Increasing deflation pressures eventually resulted in a plateau in both measures of inspiratory response. These results were consistent with the Hering-Breuer deflation reflex being activated which could have a role in protecting the FRC of the newborn infant.

Constriction↗

PubMed1979

Cardiopulmonary readjustments in passive tilt.

There is ample evidence that posture affects many cardiorespiratory variables, but the extent to which secondary reflex mechanisms complement or oppose the primary gravity effect is not clear. We have addressed ourselves to this problem by studying five normal volunteers, passively tilted from the supine to the upright position in 15 degrees increments, in random sequence, determinging cardiac output (Q), heart rate (HR), stroke volume (SV), minute and alveolar ventilation (VE and VA), functional residual capacity (FRC), and arterial-end-tidal PCO2 pressure difference. In each position, four to five measurements were obtained by noninvasive techniques. Changes in Q and in FRC were linearly related to the sine of the tilt angle, indicating that reflexes were either absent or that their net effect was proportional to the effects of gravity; this was clearly not the case for other variables (HR, SV, VE, VA) in which it was possible to demonstrate threshold values for the appearance of secondary changes.

Adolescent↗

PubMed1985

Lung volumes measured by helium dilution and by body plethysmography with mouth and oesophageal pressures: a comparative study in patients with lung disease.

A comparison was made between the helium dilution technique and body plethysmography--using both mouth pressure and oesophageal pressure against box pressure--for measuring functional residual capacity (FRC). In patients with restrictive lung disease (n = 9) no major differences in FRC were noted between the techniques. In patients with obstructive lung disease (n = 17), helium dilution underestimated FRC by a mean of 0.9 l and conventional body plethysmography (mouth-box pressure) overestimated it by 0.4 l in comparison with FRC obtained by oesophageal pressure against box pressure. The difference between the techniques increased with increasing lung volumes. It is concluded that conventional body plethysmography measures FRC more accurately than the helium dilution technique in patients with obstructive lung disease.

Female↗

PubMed2002

Development of airway function in infancy after preterm delivery.

OBJECTIVE: To assess airway function at 1 year and compare this with similar measurements made shortly after birth in preterm infants without clinical neonatal respiratory disease. STUDY DESIGN: Infants born at </=36 weeks' gestational age were eligible if they required no neonatal ventilatory support and were otherwise healthy. Paired measurements of maximal expiratory flow at functional residual capacity (V'(maxFRC)) were obtained ~3 weeks after birth in 24 preterm infants (gestational age [mean +/- SD], 33.2 +/- 2.2 weeks) and repeated at a corrected postnatal age (mean +/- SD) of 57.0 +/- 12.2 weeks. V'(maxFRC) values were expressed as Z scores by means of sex-specific prediction equations. RESULTS: V'(maxFRC) was within normal range for all infants shortly after birth (mean +/- SD Z score: -0.06 +/- 0.92). By 1 year, Z scores had reduced significantly [mean (95% CI) 2nd-1st test: -1.94 (-2.27, -1.60)]. V'(maxFRC )Z scores at 3 weeks were highly correlated with those at 1 year of age (Spearman correlation coefficient 0.64). CONCLUSIONS: Airway function during the first year shows considerable tracking. Even in the absence of neonatal respiratory disease, preterm delivery is associated with altered airway development during early infancy.

Body Height↗

PubMed1988

Effect of budesonide on pulmonary hyperinflation in young asthmatic children.

In 19 asthmatic children, aged 2-6 years, the effect of six weeks' treatment with inhaled budesonide or placebo on functional residual capacity (FRC--helium dilution) and bronchodilator responsiveness was assessed in a double blind, randomised crossover trial. FRC was increased in most children at the start of treatment. Treatment with budesonide was associated with a reduction in FRC by comparison with placebo (median change 9% v 0%; p less than 0.05). There was a trend towards a greater response to a bronchodilator after budesonide. The results suggest that inhaled corticosteroids reduce hyperinflation in young asthmatic children.

Airway Resistance↗

PubMed1992

Kinetics of NO2 air space absorption in isolated rat lungs.

We previously showed, during quasi-steady-state exposures, that the rate of inhaled NO2 uptake displays reaction-mediated characteristics (J. Appl. Physiol. 68: 594-603, 1990). In vitro kinetic studies of pulmonary epithelial lining fluid (ELF) demonstrated that NO2 interfacial transfer into ELF exhibits first-order kinetics with respect to NO2, attains [NO2]-dependent rate saturation, and is aqueous substrate dependent (J. Appl. Physiol. 71: 1502-1510, 1991). We have extended these observations by evaluating the kinetics of NO2 gas phase disappearance in isolated ventilating rat lungs. Transient exposures (2-3/lung at 25 degrees C) employed rebreathing (NO2-air) from a non-compliant continuously stirred closed chamber. We observed that 1) NO2 uptake rate is independent of exposure period, 2) NO2 gas phase disappearance exhibited first-order kinetics [initial rate (r*) saturation occurred when [NO2] > 11 ppm], 3) the mean effective rate constant (k*) for NO2 gas phase disappearance ([NO2] < or = 11 ppm, tidal volume = 2.3 ml, functional residual capacity = 4 ml, ventilation frequency = 50/min) was 83 +/- 5 ml/min, 4) with [NO2] < or = 11 ppm, k* and r* were proportional to tidal volume, and 5) NO2 fractional uptakes were constant across [NO2] (< or = 11 ppm) and tidal volumes but exceeded quasi-steady-state observations. Preliminary data indicate that this divergence may be related to the inspired PCO2. These results suggest that NO2 reactive uptake within rebreathing isolated lungs follows first-order kinetics and displays initial rate saturation, similar to isolated ELF.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗

PubMedDate not supplied

Changes in airway resistance following droperidol, hydroxyzine, and diazepam in normal volunteers.

The effects of droperidol, hydroxyzine, and diazepam on airway resistance (AR), functional residual capacity (FRC), and thoracic gas volume (TGV) were compared, using a CPI model-2000 body plethysmograph. Significant decreases in AR were seen following droperidol and hydroxyzine at all time intervals. A significant increase in AR also was noted 90 minutes after diazepam injection. FRC significantly decreased at 60, 90, 120, and 150 minutes following droperidol, and at 90 minutes following hydroxyzine, while no change was seen following diazepam. No significant changes in TGV were seen following administration of any of the drugs.

Adult↗

PubMed1975

Bronchoconstrictor effects of a deep inspiration in patients with asthma.

A deep inspiration from functional residual capacity to total lung capacity, performed at a low flow rate by a group of 40 unselected adult patients with asthma, yielded an immediate and transient increase (71 per cent, P smaller than 0.001) in specific airway resistance. In 2 of the 40, deep inspiration provoked an attack of asthma. The effect of deep inspiration can be attributed to a vagal bronchoconstrictor reflex, because it was prevented or decreased in most of the cases by inhalation of an anticholinergic drug. Beta-adrenergic blockade by propranolol potentiated in a minority of subjects the bronchoconstrictor response to deep inspiration. Deep expiration also induced a bronchoconstrictor effect, which was weaker than that of deep inspiration. It follows that functional studies of asthmatics may be biased if the technique requires maximal respiratory maneuvers.

Adolescent↗

PubMed1999

Human lung volumes and the mechanisms that set them.

Definitions of human lung volumes and the mechanisms that set them are reviewed in the context of pulmonary function testing, with attention to the distinction between functional residual capacity (FRC) and the static relaxation volume of the respiratory system, and to the circumstances in which FRC and residual volume are set by dynamic rather than by static mechanisms. Related terms, conventions, and issues are addressed, including some common semantic and conceptual difficulties, with attention to "gas trapping", "hyperinflation", and "restriction".

Functional Residual Capacity↗

PubMed2003

Respiratory effects of the scalene and sternomastoid muscles in humans.

Previous studies have shown that in normal humans the change in airway opening pressure (DeltaPao) produced by all the parasternal and external intercostal muscles during a maximal contraction is approximately -18 cmH(2)O. This value is substantially less negative than DeltaPao values recorded during maximal static inspiratory efforts in subjects with complete diaphragmatic paralysis. In the present study, therefore, the respiratory effects of the two prominent inspiratory muscles of the neck, the sternomastoids and the scalenes, were evaluated by application of the Maxwell reciprocity theorem. Seven healthy subjects were placed in a computed tomographic scanner to determine the fractional changes in muscle length during inflation from functional residual capacity to total lung capacity and the masses of the muscles. Inflation induced greater shortening of the scalenes than the sternomastoids in every subject. The inspiratory mechanical advantage of the scalenes thus averaged (mean +/- SE) 3.4 +/- 0.4%/l, whereas that of the sternomastoids was 2.0 +/- 0.3%/l (P < 0.001). However, sternomastoid muscle mass was much larger than scalene muscle mass. As a result, DeltaPao generated by a maximal contraction of either muscle would be 3-4 cmH(2)O, which is about the same as DeltaPao generated by the parasternal intercostals in all interspaces.

Adult↗

PubMed1976

The effect of positive end expiratory pressure on lung mechanics and arterial oxygenation after open heart surgery in young children.

The effect of positive end expiratory pressure (PEEP) during mechanical ventilation of the lungs was measured in 10 young children, aged 3 weeks to 30 months, who were being ventilated artificially after cardiopulmonary bypass surgery. Changes in the end-tidal lung volume were measured directly using a jacket plethysmograph, and were assumed to indicate change in functional residual capacity (FRC). Simultaneous changes in compliance and blood-gases were measured also. FRC was increased in all subjects, and in most this increase was accompanied by an increase in arterial oxygenation. There was no significant alteration in the mean values of dynamic or static compliance in the group, although dynamic compliance increased during PEEP in six patients. PEEP may be of value after cardiopulmonary bypass in young children when oxygenation is poor despite high inspired oxygen fractions. The possible mechanisms by which it increases PaO2 are discussed.

Cardiopulmonary Bypass↗

PubMed2001

Pulmonary responses during the cycle-run succession in elite and competitive triathletes.

OBJECTIVES: The purpose of this study was to determine the effect of performance level on the pulmonary responses in triathletes during the cycle-run succession. METHODS: Eight regionally and nationally ranked (Competitive) and six internationally ranked (Elite) male triathletes underwent 30 min of cycling followed by 20 min of running (C-R) and 30 min of control cycling (C). Before and 10 min after each trial, the triathletes underwent lung function testing. Ventilatory data were collected every minute using an automated breath-by-breath system. RESULTS: The results showed that (a) cycling induced a significant increase in residual volume and functional residual capacity in the Elite group (P <.05); (b) although cycling induced a significant decrease in DLCO in both groups, this decrease persisted at the end of the cycle-run exercise in the Competitive group only (P <.05); and (c) the rise in breathing frequency was significantly greater in the Competitive triathletes during the first 8 min of the subsequent run (P <.04). CONCLUSIONS: We conclude that the internationally ranked--or elite-performance--triathletes may have developed specific responses to the cycle-run succession.

Adult↗

PubMed1999

A radiographic method for assessing lung area in neonates.

The aim of this study was to determine whether computer assisted analysis of lung area on the chest radiograph reliably predicted lung volume in neonates. Anteroposterior chest radiographs taken for clinical purposes were scanned and analysed using a Power Macintosh computer with a Wacom A5 Ultra Pad and NIH image software. The cardiac, mediastinal and thymic densities and areas of perihilar and lobar consolidation were subtracted from the thoracic area to give the lung area. This was compared with lung volume, assessed by measurement of functional residual capacity (FRC), within 1 h of the chest radiograph being performed. 50 infants, median gestational age 30 weeks (range 24-43) were studied. Their median lung area was 11.23 cm2 (range 0.82-28.53) and lung volume 28 ml (range 3-103). The intraobserver and interobserver coefficients of repeatability of lung area were 1.0 cm2 and 1.06 cm2, respectively. Lung area correlated significantly with FRC (r = 0.60, p < 0.0001). It is concluded that computer assisted analysis of the chest radiograph lung area is a reliable method of assessing lung volume in neonates.

Functional Residual Capacity↗

PubMed2000

Effects of weight loss on peak flow variability, airways obstruction, and lung volumes in obese patients with asthma.

STUDY OBJECTIVES: To clarify the pathophysiologic features of the relation between asthma and obesity, we measured the effects of weight reduction on peak expiratory flow (PEF) variability and airways obstruction, compared to simultaneous changes in lung volumes and ventilatory mechanics in obese patients with stable asthma. METHODS: Fourteen obese asthma patients (11 women and 3 men; aged 25 to 62 years) were studied before and after a very-low-calorie-diet period of 8 weeks. PEF variability was determined as diurnal and day-to-day variations. FEV(1) and maximal expiratory flow values were measured with a flow-volume spirometer. Lung volumes, airways resistance (Raw), and specific airways conductance were measured using a constant-volume body plethysmograph. Minute ventilation was monitored in patients in supine and standing positions. RESULTS: As patients decreased their body mass index (SD) from 37.2 (3.7) to 32.1(4.2) kg/m(2) (p < 0. 001), diurnal PEF variation declined from 5.5% (2.4) to 4.5% (1.5) (p = 0.01), and day-to-day variation declined from 5.3% (2.6) to 3. 1% (1.3) (p < 0.005). The mean morning PEF, FEV(1), and FVC increased after weight loss (p = 0.001, p < 0.005, and p < 0.05, respectively). Flow rate at the middle part of FVC (FEF(25-75)) increased even when related to lung volumes (FEF(25-75)/FVC; p < 0. 05). Functional residual capacity and expiratory reserve volume were significantly higher after weight loss (p < 0.05 and p < 0.005, respectively). A significant reduction in Raw was found (p < 0.01). Resting minute ventilation decreased after weight loss (p = 0.01). CONCLUSION: Weight loss reduces airways obstruction as well as PEF variability in obese patients with asthma. The results suggest that obese patients benefit from weight loss by improved pulmonary mechanics and a better control of airways obstruction.

Adult↗

PubMed2003

[Relationship between thoracic cross-sectional area measured on CT and pulmonary function or dyspnea in patients with COPD].

We examined the relationship between the thoracic cross-sectional area (TCSA) and pulmonary function data or dyspnea grade in 24 patients with chronic obstructive pulmonary disease (COPD). The TCSA, i.e., the area surrounded by the rib cage, was measured on computed tomography (CT) images made 1 cm below the top of the aortic arch. Analysis of our data showed a good correlation between TCSA and total lung capacity (r = 0.65, p < 0.001), as well as functional residual capacity (r = 0.67, p < 0.0005) and residual volume (r = 0.62, p < 0.005). The patients were grouped according to their grade of dyspnea (Fletcher's five-degree scale), and the ratio of TCSA over square of height (TCSA/Ht2) was calculated for each patient. In the group with grade IV dyspnea, the TCSA/Ht2 ratios were significantly greater than those in the groups with grade II and III dyspnea, combined. In summary, in the patients with COPD, pulmonary function data indicative of lung hyperinflation correlated with the TCSA, and both parameters were increased in patients with severe dyspnea.

Aged↗