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PubMed2004

Maximal expiratory flow at FRC (V'maxFRC): Methods of selection and differences in reported values.

We compared three methods of reporting maximal expiratory flow (V'maxFRC) measured in partial expiratory flow-volume curves (PEFVCs) at the point of functional residual capacity (FRC). PEFVCs were obtained with the rapid thoracoabdominal compression technique (RTC) on a total of 446 occasions in 281 HIV-negative, asymptomatic infants (4.8-28.1 months old). Three different expressions of V'maxFRC were recorded: 1) the highest measured flow (maxV'FRC), 2) the mean of the three highest flows (mean3V'FRC), and 3) the flow at FRC in a composite curve (compV'FRC) consisting of PEFVCs, obtained at different jacket pressures and superimposed at their distal limb. The numerical value of maxV'FRC was 7.4% (+/-5.6%) higher than the mean3V'FRC, and 11.9% (+/-17.7%) higher than the compV'FRC; the mean3V'FRC was 5% (+/-18.3%) higher than the compV'FRC. Bland-Altman analysis was used to evaluate the agreement between the three indices. The mean difference and 95% limits of agreement were: maxV'FRC -mean3V'FRC, 14 +/- 18 ml/sec; maxV'FRC - compV'(FRC), 23 +/- 58 ml/sec; and mean3V'(FRC) - compV'(FRC), 10 +/- 52 ml/sec. The differences between the slopes of the three indices (regressed against height) were statistically significant, although clinically unimportant. We conclude that despite their high correlation, the mean3V'FRC and maxV'FRC should not be used interchangeably, and that the composite analysis, although useful, does not improve the reproducibility of V'maxFRC, and thus it cannot be recommended for routine use in its current form.

Child, Preschool↗
PubMed1989

Use of maximal expiratory flows to evaluate central airways obstruction in infants.

Partial expiratory flow-volume (PEFV) curves obtained by the rapid compression technique were employed to assess airway function in three infants with three different lesions of the central airways (vascular ring, congenital tracheal stenosis, subglottic polyp). Preoperatively, all three demonstrated severe flow limitation with a relatively constant forced expiratory flow over the tidal volume range. Postoperatively the PEFV curves changed to a normal convex shape, and the maximal expiratory flows at functional residual capacity (VmaxFRC) returned to normal. The PEFV curve adds to our physiologic assessment of the severity of the central airway obstruction in infants and to the efficacy of our therapeutic intervention.

Airway Obstruction↗
PubMed1998

The forced expiratory volume-time curve estimation using the electrocardiogram.

The feasibility of estimating the forced expiratory volume-time curve from the amplitude modulation of the electrocardiogram was studied using a numerical torso model and ECG signal processing. A two dimensional numerical model of the torso was solved for the maximum expiration and inspiration to study the changes in the surface potential as a result of changes in the lung volume. The numerical model showed that significant changes in the surface potential amplitude occur between maximum inspiration and maximum expiration and that this amplitude change in the left-right axis of the torso might be three times as large as in the front-back axis. In the experimental setup, ECG waveforms from the surface of the chest and the mouth air flow were simultaneously recorded from four male subjects during several forced vital capacity (FVC) maneuvers. The amplitude of the QRS complex was measured for different expired lung volumes and an estimation of the forced expiratory volume-time curve was obtained. The FVC and the FEV1 (forced expiratory volume after 1 s) spirometry indices were calculated for the two volume-time curves obtained from the electrocardiogram and from the spirometry measurements. The results differ between 0.1 and 0.8 1. These preliminary results are encouraging and might indicate that a relationship between the volume-time curve during FVC test and the electrocardiogram signals does exist. Further validation in a larger number of subjects and patients is needed before the technique can be applicable for clinical use.

Adult↗
PubMed1991

Immunological and respiratory findings in swine farmers.

The prevalence of respiratory symptoms and ventilatory capacity abnormalities in relation to immunological status was studied in 32 swine farmers and in 39 controls. A large number of swine farmers reacted to swine confinement building antigens (swine hair, 34%, swine confinement agents, 28%) but also to other extracts such as animal food (78%) and corn flour (37%). Control workers also reacted to these antigens in similar frequencies. Increased serum IgE levels were found in 3 swine farmers (9.4%) and all 3 had positive skin tests to at least one of the swine antigens. Among control workers one (2.6%) had an increased serum IgE level; this worker exhibited a positive skin reaction to swine food antigen. Swine farmers with positive skin reactions had across-shift reductions of FEF50 and FEF25 significantly larger than those with negative skin tests (P less than 0.01). Preshift measured ventilatory capacity data (FEV1, FEF50, FEF25) in swine farmers with positive skin tests were significantly lower (compared to predicted) than in those with negative skin tests. Additionally, we showed that a water-soluble swine confinement building antigen causes a dose-related contraction of nonsensitized guinea pig trachea smooth muscle studied in vitro. Our data indicate significant differences in lung function between swine workers with positive and negative skin tests. We suggest that skin testing may be helpful in identifying workers at risk for developing lung disease.

Adult↗
PubMed1977

The compliance curve for the flow limiting segments of the airway. II. Experiments with human subjects.

Maximum effort flow-static recoil curves were obtained in 5 healthy subjects breathing air, He/O2, and SF6/O2 mixtures. In 4 of them maximum effort flows corresponded to really maximal flows and their curves were transformed into compliance curves for the flow limiting segments of the airway and analyzed from the point of view of a previously presented lung model (Pedersen and Nielsen 1976). The results showed, that viscosity dependent pressure losses from the alveoli to the flow limiting segments were minimal for air and SF6/O2, but not for He/O2. When viscosity dependent pressure lossess could be negleted, then expiration of gases of different densities gave almost identical compliance curves for the flow limiting segments. This supported the applicability of the model. The calculated compliance curves for the flow limiting segments were compared with data from the literature, and the findings indicated that flow limitation during expirations with just maximal flows throughout began in the extrapulmonary airways and moved upstream during the expiration.

Adolescent↗
PubMed1984

Dynamic lung function in dogs with compensatory lung growth.

Nine puppies underwent left pneumonectomy at 10 wk of age while nine sex-matched littermates had a sham operation, and all animals were studied at 25 wk of age. Postpneumonectomy dogs demonstrated compensatory growth in that lung weight and total lung capacity (TLC) were the same as those of control animals when normalized for body weight. In postpneumonectomy dogs all lobes of the remaining right lung increased in weight, but this was most notable in the cardiac lobe which grew across the mediastinum. Subdivisions of lung volume were normal in postpneumonectomy animals except for residual volume (RV): RV/TLC was increased when compared with control animals. In intact dogs static pressure-volume curves of the lung and respiratory system did not differ between groups, and the static pressure-volume curves of excised lungs were closely similar. Maximum expiratory flow was sharply reduced in postpneumonectomy dogs, averaging 40% of flow in control dogs over the lower 50% of the vital capacity. In both groups the fractional increase in maximal expiratory flow during HeO2 breathing was substantial and similar. Regional compliances, resistances, and perfusion distribution were examined using 133Xe. Regional compliance and perfusion were reduced in the left hemithorax of postpneumonectomy dogs while regional resistances were increased.

Animals↗
PubMed1986

Airway resistance measurements throughout the respiratory cycle in infants.

Using a constant-volume infant whole-body plethysmograph containing a heated rebreathing bag, we have been able to measure airway resistance (Raw) throughout the respiratory cycle using a computer-based technique. Data from the plethysmograph transducers are sampled at 60 Hz for the calculations and Raw is calculated at each point sampled during the breath, with appropriate corrections for absolute lung volume. It was found that in most cases Raw varied less with respect to tidal volume than to tidal flow. Various patterns of Raw change in relation to tidal volume were found. These included an elevated but relatively constant resistance, a progressively rising expiratory resistance, and in 3 infants with laryngomalacia, a progressively rising inspiratory resistance. It was also found that the dynamic performance of the rebreathing bag was such that considerable errors would occur if apparatus resistance was assumed to be constant and so the actual apparatus resistance at each point was subtracted from the total resistance to give Raw. In conclusion, Raw is not constant throughout the respiratory cycle in infants and the pattern of change conveys additional information.

Airway Resistance↗
PubMed1990

Effects of deep inhalation during early and late asthmatic reactions to allergen.

Eighteen asthmatic patients with a biphasic asthmatic reaction to house dust mite were studied. The effect of deep inhalation (DI) was quantitated by comparing the maximal expiratory flow at 40% (MEF40) of vital capacity from partial (P) and maximal (M) flow-volume curves, and specific airway conductance (SGaw) before and after DI (SGawDI). At baseline, the ratio MEF40M/P was significantly larger than unity (1.45 +/- 0.26 SD), whereas the ratio SGawDI/SGaw was not significantly different from unity (0.92 +/- 0.24). During early phase reaction, both MEF40M/P and SGawDI/SGaw were significantly increased to 2.66 +/- 0.97 and 1.96 +/- 0.47, respectively. During late phase reaction, when the FEV1 values were similar to those observed during early phase reaction, MEF40M/P and SGawDI/SGaw were 1.86 +/- 0.46 and 1.43 +/- 0.29, respectively, significantly higher than the values at baseline but significantly lower than those during early phase reaction. Similar results were obtained in a subgroup of nine patients when SGaw values during the late phase reaction were similar to those during the early phase reaction. We conclude that DI has a different effect during early and late asthmatic reactions, suggesting a different ratio of airway to parenchymal hysteresis. This may result from an increased parenchymal hysteresis (more peripherally located bronchial obstruction) or a decreased airway hysteresis (prominent airway inflammation) during the late phase reaction.

Adolescent↗
PubMed1975

Respiratory function during prostaglandin-induced labor.

In a group of patients receiving intraamniotic injection of prostaglandin F2alpha or intramuscular injection of a methyl analogue of prostaglandin E2 for the termination of pregnancy, significant ariway constriction was demonstrated. The greatest responses were seen in 2 patients who had personal or family histories of asthma. If such patients receive prostaglandins, they should be carefully monitored to detect clinically important airway obstruction.

Amnion↗
PubMed1976

The influence of clinical factors on site of airway obstruction in asthma.

The effect of breathing a gas mixture less dense than room air (80% helium, 20% 02) on the maximal expiratory flow-volume curve was used to determine the influence of clinical factors on the site and nature of the airway obstruction in asthmatics. If an asthmatic did not smoke or have chronic bronchitis or recurrent respiratory infections, the site of obstruction was in more central airways than it was in the presence of these factors, when the main site was more likely to be in more peripheral airways. Both the peripheral and the central airway obstruction were at least in part due to bronchoconstriction and could be reversed with bronchodilators. Comparison of maximal expiratory flow-volume curves when the subject was breathing air and when he or she was breathing a less dense gas mixture may indicate change in the mechanical properties of the lung after the use of bronchodilators that are not apparent breathing air alone. In some instances, bronchodilators produced no change in the maximal expiratory flow-volume curve when the subject was breathing air, but there were substantial changes when he or she was breathing a mixture of helium and O2.

Adolescent↗
PubMed1978

Responses to isoproterenol in a general population sample.

The response of forced expiratory flow to inhalation of isoproterenol was evaluated in a general population sample of 1,063 subjects. Percentage changes in the forced expiratory volume in 1 sec and in the maximal flow measured at 50 percent of the initial expired forced vital capacity appeared to be the best indicators of responsiveness to bronchodilator. Subjects with a history of asthma more often showed responsiveness than did the remainder of the population, even when their initial function was within normal limits. Over-all, a high proportion of subjects with abnormalities in baseline forced expiratory volume in 1 sec or maximal flow after exhalation of 50 per cent of the forced vital capacity showed sufficient improvement after bronchodilator to cause their values after isoproterenol to fall within the normal range. The data suggest that responsiveness to bronchodilator aerosol may be a useful guide to the presence of bronchial reactivity in epidemiologic studies of obstructive airway diseases.

Adult↗
PubMed1979

Pulmonary function in identical twins: comparison of nonsmokers and smokers.

Forty-five apparently normal pairs of identical twins were given pulmonary function tests to determine the role of genetics in bronchial susceptibility to cigarette smoke. Maximal expiratory flow at 60 per cent of total lung capacity (Vmax60) was the best discriminator of smokers from nonsmokers among pairs in which one member smoked and the other did not. The intrapair difference of Vmax60 values in pairs in which both members smoked was the same as in pairs in which both members did not smoke. These data support the view that genetic factors are important in determining the vulnerability of the airways to cigarette smoke.

Adult↗
PubMed1996

Cross-shift changes in blood inflammatory markers occur in the absence of airway obstruction in workers exposed to grain dust.

Grain dust is well known to cause both acute and chronic respiratory disorders, and endotoxins are considered key components in this. Since endotoxins are known to elicit proinflammatory mediators, we investigated cytokine (tumor necrosis factor [TNF], interleukin-6, interleukin-8) release and a number of proinflammatory and anti-inflammatory proteins (soluble TNF receptors, lipopolysaccharide (LPS) binding protein, bactericidal permeability increasing protein (BPI), C-reactive protein) in plasma of workers exposed to grain dust. In two surveys during 1 week, lung function was measured daily before and after the shift, using flow-volume curves and/or forced oscillation measurements. On Monday and Friday, blood samples (30 mL) were drawn and cytokine release was determined by enzyme-linked immunosorbent assay in supernatant of isolated monocytes or whole blood culture, either unstimulated or on the ex vivo stimulation with 3 ng/mL or 1,000 ng/mL endotoxin. Individual exposures were determined from stationary dust measurements at every workplace combined with personal task analysis during all shifts. In both surveys, no cross-week change in lung function parameters was observed. In the first survey (average exposure: 20.2 mg/m3), monocyte spontaneous TNF release was increased sevenfold cross week (p<0.001) and was significantly related both to individual dust exposure (r=0.62) of that week and the increase in soluble TNF receptor 75 kD (r=0.85). In the second survey, where average exposure was much lower (3.67 mg/m3), impedance parameters indicated a significant improvement of airway function, and cross-week changes in inflammatory markers were minimal. Therefore, we conclude that inflammatory events can be used to monitor adverse respiratory effects of moderate grain dust exposure.

Acute-Phase Proteins↗
PubMed1991

[Maximal ventilatory pressure through the mouth in adults: normal values and explanatory variables].

Mouth pressure measured during maximal inspiratory or expiratory efforts depends on the force exerted by ventilatory muscles. Normal values and anthropometric factors accounting for maximal inspiratory and expiratory pressures (MIP, MEP) are not fully agreed upon to date. We measured MIP and MEP in 253 normal subjects (135 females and 118 males, age 15-59 years) using a digital transducer (163 Sibelmed). All subjects had normal forced vital capacity (FVC) and one second forced expiratory volume (FEV1). Sex, age, height and weight were recorded for all subjects and were entered as independent variables in computation of linear multiple regressions with MEP or MIP the dependent variables. MEP and MIP were greater in males than in females (p less than 0.01) with MIP lower than MEP in both sexes (p less than 0.01). In both males and females, FVC and FEV1 depend on age and height (p less than 0.01). In the entire group, we found a correlation of MIP in females and MEP in males with age (p less than 0.01) and of both MIP and MEP in females with weight (p less than 0.01). However, in subjects aged 20-59 years, there was no significant dependence of MIP and MEP on age, and when the weight of subjects was normal (n = 170), MIP and MEP were independent of weight. We conclude that in adults aged 20-59 years and with normal weight, maximal ventilatory pressures depend solely on sex. In this subgroup mean (+/- SD) values of MEP and MIP were 111 +/- 25 cmH2O and 79 +/- 19 cmH2O respectively in females and 192 +/- 42 cmH2O and 117 +/- 25 cmH2O in males.

Adolescent↗