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PubMed1990

Divers' lung function: small airways disease?

Pulmonary function was measured in 152 professional saturation divers and in a matched control group of 106 subjects. Static lung volumes, dynamic lung volumes and flows, transfer factor for carbon monoxide (T1CO), transfer volume per unit alveolar volume (KCO), delta-N2, and closing volume (CV) were measured and compared with reference values from recent Scandinavian studies, British submariners, and the European Community for Coal and Steel (ECCS) recommended reference values. Diving exposure was assessed as years of diving experience, total number of days in saturation and depth, and as the product of days in saturation and mean depth. Divers had significantly lower values for forced expired volume in one second (FEV1), FEV1/forced vital capacity (FVC) ratio, FEF25-75%, FEF75-85%, FEF50%, FEF75%, T1CO, and KCO compared with the controls and a significantly higher CV. There was a positive correlation between diving exposure and CV, whereas the other variables had negative correlations with diving exposure. Values for the control group were not different from the predictive values of Scandinavian reference studies or British submariners, although the ECCS standard predicted significantly lower values for the lung function variables both in divers and the control group. The pattern of the differences in lung function variables between the divers and controls is consistent with small airways dysfunction and with the transient changes in lung function found immediately after a single saturation dive. The association between reduced pulmonary function and previous diving exposure further indicates the presence of cumulative long term effects of diving on pulmonary function.

Adult↗
PubMed1990

The lungs and airways in achondroplasia. Do little people have little lungs?

Achondroplasia is a unique model of the effects of skeletal dysplasia and dwarfism on the respiratory system. We measured chest dimensions, spirometry, lung volumes, maximal expiratory flow volume curves, nasal and airways resistance, closing volume, maximal inspiratory/expiratory pressures, and tracheal area by acoustic reflection in 12 healthy subjects with achondroplasia. Anterior-posterior thoracic diameter was mildly reduced in men. Vital capacity for all subjects was 108 percent +/- 18.6 percent (SD) of that predicted for achondroplastic subjects, but was reduced when compared with values for people of average stature that were predicted, based on either sitting height or thoracic height. The reduction was relatively greater in male than in female subjects. The RV/TLC and FRC/TLC ratios were normal. Other measurements were similar to those in average-statured adults. We conclude that achondroplasia results in a reduction in vital capacity out of proportion to what would be expected if these subjects had normal limb size. Although the lungs may be small, they are functionally normal, as are the airways.

Achondroplasia↗
PubMed1980

Pulmonary function abnormalities in thalassemia patients on a hypertransfusion program.

Pulmonary function tests were performed in 12 thalassemia patients on a hypertransfusion program (age 18.4 +/- 2.6 SEM years) to determine the presence of any abnormalities of lung function. These included spirometry, expiratory flow rates, body plethysmography, single-breath nitrogen washout, single breath carbon monoxide diffusing capacity, and arterial blood gases. Only one patient had normal pulmonary function. Arterial hypoxemia was present in ten of 12 patients at rest. The total lung capacity (TLC) was normal. The residual volume was abnormally increased in five of 12 patients. The slope of phase III of single breath nitrogen washout curve was abnormal in five of 12 patients, but the closing volume was normal. The maximal expiratory flow rate at 60% total lung capacity was decreased in four of 12 patients, suggesting the presence of small airway disease. The single breath carbon monoxide diffusing capacity was normal in all patients. These pulmonary function abnormalities did not correlate with age or the cumulative amount of iron via blood transfused. The small airway obstruction, hyperinflation; and hypoxemia observed in thalassemia patients on a hypertransfusion program may result from the basic disease, iron deposition in the lungs, or other factors.

Adolescent↗
PubMed1979

Inflection points of lung pressure-volume curves using a three-balloon-catheter system.

We measured the pressure-volume curves (PV curves) of the lung simultaneously at three levels in the esophagus below the tracheal bifurcation using the three-short-balloon-catheter system in 11 normal seated men and compared the inflection points (IP's) of three PV curves with the closing volume (CV) on the single-breath nitrogen washout curve. The mean pressure gradient from the top of the uppermost balloon to the top of the lowermost balloon (10 cm apart) was 0.58 +/- 0.06 cmH2O/cm at 60% total lung capacity (TLC). The IP was dependent on depth within the esophagus; i.e., the lung volume at IP (VIP) of the uppermost balloon was the smallest and the transpulmonary pressure (Ptp) at IP (PIP) of that balloon was the largest of the three IP's. VIP's were significantly larger than CV's and the mean absolute difference between the VIP of the uppermost balloon and the closing capacity (CC) was 0.9 liter. These results suggest that IP may not exactly reflect airway closure.

Adult↗
PubMed1996

The effect of continuous positive airway pressures on lung volumes in tetraplegic patients.

Continuous positive airway pressure (CPAP) is widely advocated for the treatment of respiratory complications. However the effects of CPAP on the respiratory function of tetraplegic patients have not yet been investigated. The purpose of this study was to examine the effects of breathing with different levels of CPAP on the relationship between closing volume (CV) and functional residual capacity (FRC) in ten recently injured, but otherwise healthy tetraplegic patients with lesions between the fourth and eighth cervical segments. Lung volumes were measured before, during and after 32 min of zero end-expiratory pressure and 5 and 10 cm H2O of CPAP. FRC was measured by the open-circuit nitrogen washout method and CV was measured by the single breath nitrogen washout method. FRC was unaffected by zero end-expiratory pressure, but both 5 cm H2O and 10 cm H2O of CPAP caused significant increases in FRC. FRC returned to pre-CPAP values by the first minute after removal of 5 and 10 cm H2O of CPAP. We were unable to measure CVs in any subjects. It was concluded that 5 and 10 cm H2O of CPAP increase FRC in healthy tetraplegic individuals, but that these increases are rapidly lost with the subsequent removal of CPAP. These results suggest that CPAP may have a role in the treatment and prevention of respiratory complications in tetraplegics.

Adult↗
PubMed1981

Changes in distribution of ventilation with lung growth.

We systematically studied the effects of varying preinspiratory lung volumes and expiratory flow rates on the alveolar plateau of the single-breath oxygen test in children and adults. With inhalations of oxygen beginning at functional residual capacity (FRC) compared with residual volume (RV), the slope of phase III increased in 52 of 54 children and 6 of 6 adults (mean increase 29.2%, P less than 0.001) but then decreased at preinspiratory volumes greater than FRC. With maximal expiratory flows, the slopes were smaller than slopes from conventional maneuvers in 14 of 15 children by a mean 24.1%, P less than 0.001. These data suggest that apex-to-base differences in regional lung volume are a major determinant of the slope. Slopes (FRC maneuver) decreased as a function of the height of the children (r = -0.73, P less than 0.001), but differences in nitrogen concentration over the alveolar plateau increased with height (r = 0.70, P less than 0.001). This indicates that the apex-to-base differences in regional lung volume increase with lung size. An estimate of mixing efficiency between resident and inspired gas derived from the alveolar plateau increased with height for both RV (r = 0.40, P less than 0.005) and FRC maneuvers (r = 0.45, p less than 0.005) and was greater for FRC than RV (P less than 0.001). These increases in mixing efficiency are consistent with previously demonstrated decreases in closing volume with growth.

Adult↗
PubMedDate not supplied

[Functional approach to asthma (author's transl)].

The different pulmonary function tests which enable the diagnosis of asthma and its functional criterium, reversible bronchial obstruction, are reviewed. It is our opinion that in epidemiology where the diagnosis should be made "on the spot" in a simple, rapid and non-aggressive manner, the most appropriate tests are the following: the FEV1 or other forced expiration parameters, to which could be added the measurements of closing volume, the slope of phase III, and/or flow-volume curves using two gas mixtures. The modifiers of bronchomotricity could confirm the reversible nature of the bronchial obstruction.

Airway Resistance↗
PubMed1988

Does airway closure affect lung sound generation?

The purpose of this experiment was to test the hypothesis that airway closure impedes the production of lung sounds at low lung volume. We recorded breath sounds in three healthy men during inspiratory vital capacity manoeuvres in upright, head-down and lateral decubitus postures. We then compared the rate of increase of breath sound intensity (BSI) between the dependent and non-dependent lung zones. Closing volumes, measured separately, were normal in the upright but increased in the head-down postures. The data revealed no consistent lag in the rate of increase of BSI over the dependent lung zones in any of the postures. Our data suggest that airway closure does not influence lung sound generation. If true, this implies that lung sounds are produced proximally to the site of physiologic airway closure.

Adult↗
PubMedDate not supplied

Regional hypoventilation and bronchoconstriction during pulmonary air embolism.

The hypothesis that experimental pulmonary air embolism would lead to bronchoconstriction in the upper lungs and a shift in ventilation toward the lower lung regions was tested in anaesthetized and paralyzed dogs. During constant rate air infusion (0.15 ml X kg-1 X min-1), regional distribution indices were obtained using radioactive xenon boli injected at the mouth at residual volume. The results show that there was a shift of inspired xenon toward the dependent lungs after 30 min of air infusion and that this shift was accompanied by a rise in pulmonary artery pressure, a slight decrease in vital capacity, a significant increase in closing volume and an increase in airway resistance. Inspiring 5% CO2 after the shift did not reverse the distribution of xenon boli. Intravenous injection of isoproterenol after the changes had occurred, on the other hand, invariably returned the distribution toward control values. These findings indicate that hypoventilation and bronchoconstriction occurred in the non-dependent lungs during pulmonary air embolism.

Airway Resistance↗
PubMed1997

Pulmonary function in space.

The lung is exquisitely sensitive to gravity, and so it is of interest to know how its function is altered in the weightlessness of space. Studies on National Aeronautics and Space Administration (NASA) Spacelabs during the last 4 years have provided the first comprehensive data on the extensive changes in pulmonary function that occur in sustained microgravity. Measurements of pulmonary function were made on astronauts during space shuttle flights lasting 9 and 14 days and were compared with extensive ground-based measurements before and after the flights. Compared with preflight measurements, cardiac output increased by 18% during space flight, and stroke volume increased by 46%. Paradoxically, the increase in stroke volume occurred in the face of reductions in central venous pressure and circulating blood volume. Diffusing capacity increased by 28%, and the increase in the diffusing capacity of the alveolar membrane was unexpectedly large based on findings in normal gravity. The change in the alveolar membrane may reflect the effects of uniform filling of the pulmonary capillary bed. Distributions of blood flow and ventilation throughout the lung were more uniform in space, but some unevenness remained, indicating the importance of nongravitational factors. A surprising finding was that airway closing volume was approximately the same in microgravity and in normal gravity, emphasizing the importance of mechanical properties of the airways in determining whether they close. Residual volume was unexpectedly reduced by 18% in microgravity, possibly because of uniform alveolar expansion. The findings indicate that pulmonary function is greatly altered in microgravity, but none of the changes observed so far will apparently limit long-term space flight. In addition, the data help to clarify how gravity affects pulmonary function in the normal gravity environment on Earth.

Humans↗
PubMed1985

[Computerizing the single-breath nitrogen washout test].

The classical assembly used for the single breath nitrogen washout implies the manipulation of valves by the operator, a perfect coordination of respiratory maneuvers by the subject and a rigid standardization of the interpretation of the tracings by the technicians doing the calculations. We present a computerized analysis of the single breath nitrogen test, based on a microcomputer (Apple II 48K) solving most of the problems above. The opening of the valves is operated by the computer program recorded on disk; the tidal volume and expiratory flow are displayed on the screen on line allowing the subject to comply with the requested limits; the nitrogram is displayed at the end of the test, allowing the technician to explain the errors (if any). The program then goes on computing the slope of phase III, the closing volume, total lung capacity and its subdivisions for each trial, and the average values for two or three trials accepted by the operator. The system worked satisfactorily during a pilot study in healthy adults (variability and reproducibility) and was particularly useful in a field survey of children and adolescents.

Closing Volume↗
PubMed1981

[Discriminating power of multivariate parameters of respiration in epidemiological studies (author's transl)].

Applying a broad scale of lung function tests in epidemiological surveys (929 metal workers of a big industrial shop, 211 of them with signs of chronic obstructive lung disease, COLD, and 1,266 pupils of 2 towns with different dust exposition) we found similar multivariate discriminant functions in all age groups between 7 and 79 years of age to differentiate between COLD-population and normal population. Residual volume in % of total capacity (RV/TC) seems to be the most relevant central parameter in all age groups, which should be combined with one of the inhomogeneity parameters of single breath or multi breath distribution tests ( delta F/ delta V or breath of inhomogeneity IHB) in juveniles between 7 to 16 years of age and with closing volume (CV/VC) in adults between 20 to 79 years of age. Conventional ventilation parameters and the arterial oxygen tension don't contribute additional information to multivariate analysis, which isn't already summarized by the parameters RV/TC.

Adolescent↗
PubMed1984

Airway pressure gradient during high-frequency ventilation.

Six mongrel dogs, each serving as its own control, underwent ventilatory trials on high-frequency positive-pressure ventilation (HFPPV) and high-frequency oscillation (HFO), before and after oleic acid-induced lung injury. Central and distal airway pressures were compared to simultaneous measurements of oxygen transport and shunt fraction. Airway pressure differences were more pronounced with HFO. Mean proximal pressure with HFO was 4.91 +/- 1.9 mm Hg, rising to 11.6 +/- 3.6 mm Hg distally. HFPPV produced somewhat higher proximal and distal pressures of 9.5 +/- 5.2 and 14.2 +/- 6.9 mm Hg, respectively. After induction of lung injury with a subsequent decrease in compliance, central (proximal) airway pressures remained relatively unchanged, while distal pressures showed a further rise, thus increasing the pressure gradient to 9.2 +/- 3.8 mm Hg for HFO and 6.6 +/- 4.6 mm Hg for HFPPV. Shunt fraction increased with decreased oxygen transport after lung injury in both models; however, the increase was less pronounced with HFO, which maintained a greater pressure gradient. The distal increase in airway pressures may be important in maintaining critical closing volumes in the diseased lung. By creating a pressure gradient, high-frequency ventilation by either jet or oscillator may improve functional residual capacity and oxygenation.

Animals↗
PubMed2006

Nitrogen washout slope in poorly controlled asthma.

Short-term control of asthma is often lacking even though forced expiratory volume in 1 s (FEV1) remains above normal value. Small airways are a potential key site of persistent inflammation and structural modification. Noninvasive assessment of small airways was found to be difficult, but the computerized single breath nitrogen washout test (SBNT) has been recently successfully reintroduced with this aim. Twenty-four asthmatics (13 females) of various severity but with normal FEV1 were compared with 24 healthy volunteers (13 females) and studied at steady-state after bronchodilatation (400 microg salbutamol). Spirometric values, plethysmographic data, phase III (slope of phase III of the SBNT, dN2) and IV [closing volume (CV), with closing capacity (CC) = CV + residual volume (RV)] of the SBNT were checked. Asthma severity, recent control, exacerbation rate, and therapy requirements were assessed on the basis of validated questionnaires (ACQ) and international guidelines. Patients were prospectively pooled into two equal groups according to their exacerbation rate. The reproducibility of the measurements obtained on 2 following days was assessed. All plethysmographic values, except total lung capacity (TLC), differentiated asthmatic patients from controls. The CC/TLC [124 (117-148) vs 117 (112-123), P = 0.04] and dN2 [110 (99-190) vs 94 (75-111), P = 0.02] were increased in asthma. The dN2 was significantly increased in patients with frequent exacerbations [100 (83-105) vs 195 (141-212), P = 0.0005]. A correlation was obtained between dN2 and recent asthma control (rho: 0.62; P = 0.003), number of exacerbations (rho: 0.71, P = 0.0008), and RV/TLC (rho: 0.49, P = 0.026). This study demonstrated that ventilation inequalities assessed by dN2 represent an important indicator of poor asthma control and high exacerbation rate in high symptom perceivers. New therapies focused on small airways should now be developed.

Adolescent↗
PubMed1978

Indications for pulmonary function testing.

Pulmonary function testing is needed to determine the pathophysiology present in the patient with cardiopulmonary disease. Blood gases and pH should be obtained during emergency situations and during cranial, thoracic, and extensive cervical or abdominal surgery. Lung function tests can be divided in global such as spirometry and diffusing capacity which study the ventilation and transfer of gases and regional determinations of ventilation and perfusion. Both types of tests complement each other and should be used together. The spirometry should consist at least of determination of the vital capacity and is determined in the first second to ascertain if there is obstructive lung disease. Some tests such as flow-volume curves, alveolar-arterial gradients and closing volume are very useful to detect early pulmonary disease before any symptoms or findings are present. This is probably one of the most important medical indications for pulmonary function testing. Before certain types of surgery pulmonary function testing is indicated; if the spirometry and diffusing capacity tests are normal, there is no pulmonary contraindication for the planned surgery. In chest surgery if there is significant compromise of the spirometry and diffusing capacity regional lung function tests are indicated to study the pathophysiology at regional level, thus trying to circumscribe the lung resection to the diseased areas.

Blood Gas Analysis↗
PubMed1984

Pulmonary function tests in excised dog lungs with small airway obstruction by beads.

About 100 beads, 2 mm in diameter were wedged into the small airways of excised dog lungs. Pulmonary function tests were performed in the lungs before and after the obstruction of the small airway with beads. Of the pulmonary function tests performed, lung pressure-volume curve, lung resistance-lung volume relationship, frequency dependency of dynamic compliance, closing volume, and N2 multiwashout curve did not show any significant alteration after small airway obstruction. Only the flow-volume curve at low lung volume showed any significant alteration. This suggests that the flow-volume curve is the most sensitive pulmonary function test in the detection of early obstructive impairment of the small airways.

Airway Obstruction↗
PubMed1978

Small airways function in pulmonary sarcoidosis.

Closing volume and maximal expiratory flow-volume curves were performed in a group of 25 patients with pulmonary sarcoidosis in stages I and II and with normal spirographic results. Although the mean values of these tests were mostly within the limits of predicted values, 48% of the patients had an increased slope of the alveolar plateau and 40% had decreased maximal expiratory flow at low lung volumes. Abnormal test results were found even in patients with normal static lung compliance. Our results suggest that functional abnormalities in small airways may occur early in the course of sarcoidosis.

Adolescent↗
PubMed1981

Exchanges of oxygen and carbon dioxide alter inert gas pattern in single-breath tests.

Concentration of inert gas in the lung is lowered when CO2 entrance exceeds O2 exit and is raised when O2 exit predominates. In air-breathing subjects who expire to residual volume, this "metabolic gas effect" often causes a rising N2 concentration when in fact there should be a terminal fall because of low N2 in apical regions. In single-breath tests, we compared the dilution of resident N2 with dilution of an inspired gas, Ne, to find the "ideal" inert gas concentration (due only to mixing of resident gas with inspired gas). The displacement from the ideal concentration vs. volume pattern depends on the timing of the breath, because early CO2 entrance gives way later to O2 exit. Sometimes observed patterns are above or below but parallel to the ideal, and sometimes the observed slope of phase III is steeper than ideal for N2 and flatter than ideal for Ne. In addition to phase III distortions, the metabolic gas effect sometimes also distorts phase IV height and the intersection between phases III and IV. The distortions depend strongly on absolute concentration of the indicator gas in the lung, so they are very small when "closing volume" maneuvers are done in the conventional manner. However, distortions can be large and misleading when single-breath maneuvers are done in unconventional ways.

Carbon Dioxide↗