The single breath nitrogen washout test.
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Child↗
Biomedical subjects
R Sixt
Publications and source records attributed to R Sixt.
Density dependence of expiratory flow--a useful basis for lung function tests?
The aim of this investigation was to study the density dependence of forced expiratory flow and the ability of tests based on density dependence to disclose smoking-induced small airways dysfunction. The lung function of 212 systematically sampled men (mean age 40.3; range 30-48 years) was studied by recording flow-volume curves during air or helium-oxygen (HeOx) breathing and by the single breath N2-test. Density dependence was expressed as the percentage increase in flow from air to HeOx when 50 and when 25% of the vital capacity (VC) remained to be expelled (dMEF50 and dMEF25). The mean dMEF50 in 59 healthy non-smokers was 40% (range +7 to +72) and the mean dMEF25 24% (range -20 to +63). Density dependence apparently decreased with relative lung volume and also with increasing age. Despite the wide variation of density dependence in the reference group, dMEF50 was on average significantly reduced in smokers, and dMEF25 in ex-smokers and subjects with symptoms such as cough and/or sputum production, wheezing unrelated to common colds and dyspnea when walking on level ground. However, only 8% of the smokers exhibited 'abnormal' density dependence (dMEF25 less than (predicted value--2RSD] as compared to 11 and 33% for the forced expiratory volume in one second (FEV1) and dN2 (alveolar slope). If abnormal dN2 in the smoking group is taken to indicate smoking-induced small airway dysfunction, then the ability of dMEF50 and dMEF25 to disclose such dysfunction is limited.
Adult↗
Overestimation of inspiratory upper airway resistance.
Inspiratory resistance was found to be 10-50% larger than the expiratory in a model of the upper airways. This was most likely caused by a high kinetic energy component in the airstream close to the constriction reducing the lateral pressure in excess of what could be explained by the frictional pressure drop. Consequently, the inspiratory resistance was overestimated. During expiratory flow, on the other hand, the kinetic energy component at the same site in the trachea was smaller and similar to that in the mouthpiece resulting in an apparently adequate assessment of expiratory resistance. These results may explain why previous authors have found equal inspiratory and expiratory upper airway resistance although the vocal cords abduct during inspiration and adduct during expiration. Pressures obtained by means of the tracheal puncture appeared to be more reliable compared to those obtained from puncture of the cricothyroid membrane.
Air Pressure↗
The single-breath N2-test and spirometry in healthy non-smoking males.
Healthy males (aged 30-70), who had never smoked, were studied. The 178 subjects were selected by systematic sampling from an urban population. Using the single-breath N2-washout test we measured the closing volume (CV) and the slope of the alveolar plateau (delta N2). A prediction equation for CV was produced by simple regression on age. delta N2 showed an accelerated increase with age above the age of 50. A curvilinear equation was established: delta N2 (%/1) = 0.85 + e0.0929 x A( yrs ) -6.302. Reference equations were also established for vital capacity (VC), forced expiratory volume in one second (FEV1) and FEV1 in per cent VC (FEV%) by means of linear multiple regression on age and height. The distribution of delta N2 was not homogenous throughout the age-range. As an upper limit of the reference range, we suggest 180% of the predicted value.
Adult↗
Lung function of sheet metal workers exposed to fiber glass.
Out of 532 registered and contacted sheet metal workers, 251 responded, but only seven pairs were acceptable for the present study due to the following requirement: no history of smoking, pleural plaques or asbestos exposure. Seven of these workers were exposed daily to fiber glass, and seven were almost never exposed. In a second step nine additional exposed workers were included. Ordinary spirometry, lung volumes, closing volumes and the slope of the alveolar plateau, the maximum expiratory flow in air and after helium-oxygen breathing, and the elastic recoil pressures were measured. No evidence of small airway dysfunction or restrictive or obstructive ventilatory impairment was found, but the elastic recoil pressures of the exposed group were slightly increased. Fiber glass can conceivably cause a corresponding faint and probably harmless fibrous reaction in the lung parenchyma.
Adult↗
Tracheotomy--a satisfactory method in the treatment of acute epiglottitis. A clinical and functional follow-up study.
A follow-up study, including clinical examination, X-ray and function tests, of 27 children with acute epiglottitis treated with tracheotomy at the ENT-Department, Mölndal Hospital during 1971-1975 has been performed. The function tests were an important part of the investigation and included measurement with the He-dilution technique, flow--volume curves and the forced oscillation technique. No child had any detectable tracheal stenosis or any other serious per- or postoperative complication. The only complication at all was one ugly scar on the neck. The tracheotomized patient needs very little sedation and the time spent at the intensive care unit can be shorter than for those patients treated with nasotracheal intubation.
Acute Disease↗
Effects of preinspiratory volume on the nitrogen closing volume test.
The effect of varying the preinspiratory volume (VIair; range: 0-75% vital capacity, VC) on the nitrogen closing volume (CV) test was studied in twelve seated subjects, aged 24-62 years. When VIair was increased from 0 to about 12% VC, the height of phase IV, the amplitude of the cardiogenic oscillations, CV and the slope of phase III increased. The height of phase IV and the amplitude of the cardiogenic oscillations showed a maximum at VIair = 12% VC, although the average CV was about 18% VC. While the height of phase IV and the amplitude of the cardiogenic oscillations decreased when VIair was increased above 12% VC, CV did not change and the slope of phase III increased consistently. These results cannot be explained solely by the regional lung volume model of Sutherland et al. (1968). However, if that model is extended to include the assumption that within a region alveoli behind closed airways may be differently expanded, we predict CV to be underestimated at low VIair, independently of the upper to lower nitrogen concentration difference, in agreement with present findings. This assumption would also explain why the maximal height of phase IV can be obtained at a VIair lower than CV.
Adult↗
Prediction of postoperative hypoxemia in smokers and non-smokers.
Age, weight, spirometric variables, peak expiratory flow and airway closure assessments were correlated to postoperative gas exchange in 40 cholecystectomized subjects grouped according to smoking history. Pao2 was significantly lower in the smoking group both pre- and postoperatively, but the decrease in Pao2 following operation was of the same magnitude irrespective of smoking history. In non-smokers, the preoperative relationship between expiratory reserve volume and closing volume (ERV-CV) showed the highest correlation to postoperative alveolar-arterial oxygen difference P(A-a)o2 (r = -0.88, P less than 0.001) and to the increase of P(A-a)o2 following operation (r = -0.67, P less than 0.001), whereas age was found to be the best preoperative predictor of postoperative gas exchange in smokers.
Adult↗
Effect of the slope of the alveolar plateau on determination of closing volume.
Repeated closing volume (CV) determinations were obtained simultaneously with the nitrogen method (CV-N2) and with a helium bolus method (CV-He) in 19 selected subjects with normal routine spirometry. Ten subjects had normal slopes of phase III and nine had abnormally steep slopes of phase III obtained with the nitrogen method. No systematic difference was found between CV-N2 and CV-He irrespective of the steepness of phase III, which seems to indicate that at least in spirometrically normal subjects airway closure is adequately assessed by the nitrogen method - even in the presence of a steep slope of phase III.
Closing Volume↗
Validity of the "airflometer"--a simple device for assessment of forced expiration.
The device is basically a plastic turbine with a reduction gear (approximately 1:300) driving an indicator. Following a forced expiration on the indicator comes to rest after about 30 s, when it is read. The reading appears to be generated by the expired flow versus time pattern, and during a forced expiration, close to maximum speed for the turbine is reached within 0.5 s. In a given subject repeated measurements with the same apparatus varied within a few per cent, whereas the variation was considerable among different apparatuses. Readings correlated about equally well with FEV0.5 and FEV1.
Forced Expiratory Flow Rates↗
Ventilatory lung function following two years of tobacco abstinence.
Spirometry, maximal expiratory flows and the nitrogen closing volume test were studied in 59 subjects following their attempt to give up smoking. Seventeen subjects were tobacco abstinent for at least 5 months. This group showed significant improvement of vital capacity (VC), forced expiratory volume in 1 sec (FEV1) and the slope of phase III. Nine of these subjects remained ex-smokers for at least 24 months. However, no significant improvement of any of the measured variables could be established in this group. This may be due to the small number in the group and the circumstance that they were older and had worse lung function before smoking cessation compared with those who resumed smoking.
Adult↗
Closing volume and gas exchange in obese patients before and after intestinal bypass operation. (A preliminary report).
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Adolescent↗
A simple pressure calibrator.
A simple reliable, easy-to-use, and inexpensive device for obtaining any predetermined static gas pressure within +/- 35 cm H2O is described. It is suitalbe as a calibrator for pressure transducers as used in respiratory physiology. It is more convenient to use than an ordinary U-tube.
Manometry↗
Further studies on nicotine-induced alterations in histamine metabolism in the rat.
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Adrenal Glands↗
The forced oscillation technique in children with respiratory disease.
The single-frequency forced oscillation technique was used to estimate the total respiratory impedance, resistance, and reactance at 2, 4, and 12 Hz of children who had cricoid stenosis (CS; n = 11), provoked bronchoconstriction (PB; n = 6), or cystic fibrosis (CF; n = 13). The selection criteria for patients who had CS and CF were abnormal forced expiratory volume in 1 sec (FEV!) and/or maximal expiratory flow at 50% vital capacity (Vmax 50%). Sixteen of the 17 patients who had CS or PB were found to have resistance (Rrs) values outside the normal range at 4 Hz; at 2 Hz, 14 were found to have abnormal values and, at 12 Hz, only 9. The reactance in the CS and PB groups was somewhat less discriminative than Rrs at all frequencies. Of the 13 patients who had CF, only 4 had abnormal Rrs values; in this clinical condition, the reactance at 2 Hz was the most discriminative variable, being abnormal in 6 of the 13 patients. Irrespective of the clinical group, the Rrs was, in absolute terms, highest at 2 Hz, and it decreased with increasing frequency. This pattern of negative frequency dependence was, however, not obviously specific for any of the tested clinical conditions and offered no information in addition to a single low-frequency determination.
Adolescent↗
Non-uniform lung elastic properties and the slope of the alveolar plateau.
Dispersion of elastic properties within the lungs may contribute to the creation of a sloping alveolar plateau of the single-breath N2 washout curve. In this study we have systematically explored the behaviour of a simple two-compartment lung model with non-uniform pressure-volume characteristics. The inhomogeneity was expressed in terms of the ratio between the shape constants (k1/k2) of the compartmental pressure-volume curves and the ratio between compartmental RV/TLC (R-RV/TLC). The model simulations indicate that normal slope magnitudes can be achieved with a moderate degree of inhomogeneity (k1/k2 and R-RV/TLV = 2). The model simulations also show that a phase II-like shape of the curve--of non dead space origin--may occur and furthermore that single-breath TLC determinations increasingly underestimate true TLC as the R-RV/TLC deviates from unity. For a given degree of inhomogeneity, the model predicts the slope to increase with overall RV/TLC and k but decrease with TLC. The relations between these overall factors and the slope of phase III are also found in a patient group, where these factors explain approximately 61% of the slope variance.
Adolescent↗