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Peak expiratory flow (PEF) can be defined as the maximum flow at the mouth achieved during an expiration, delivered with maximum force starting from the level of maximum lung inflation. There is evidence that PEF may be determined by the wave speed flow-limiting mechanism, in which case a high PEF is consistent with a low resistance upstream to the flow-limiting segment (the choke point), a large cross-sectional area here, and/or a small compliance of the airway wall. PEF is obtained when the expiration is initiated with maximal inflation of the lungs, because this will make the elastic recoil pressure maximal and the upstream frictional pressure loss minimal. PEF is obtained with maximum expiratory effort, because high acceleration of flow will cause wave speed limitation at a higher lung volume. If PEF is not flow-limited, the effort-dependence will be marked. Flow transients of PEF beyond the maximum flow-volume perimeter may be related to effort-dependent contribution of flow from the collapsing airway, but time-dependent factors, instability of the airway, and inhomogeneities of the lungs may contribute. For the purpose of standardization, it is recommended that forced expiration is initiated with open glottis and immediately after a maximal inspiration. The position of the head should be neutral, because hyperextension may increase PEF and flexion may decrease PEF by changing the stiffness of the larger airways.

We investigated the effects of antigen and histamine on the nasal passage patency in guinea pigs with or without nasal allergy. The change of nasal patency was measured by acoustic rhinometry and nasal airway resistance. Acoustic reflections have been used in adult humans to determine nasal cavity dimensions in terms of cross-sectional areas as a function of the distance from the nostril. In order to measure nasal cavity dimensions in guinea pigs, we modified equipment for use in humans by decreasing sound tube dimensions, increasing sampling frequency, and applying a special nosepiece. The percent change of volume, minimum cross-sectional area, and nasal airway resistance showed the largest changes at 10 minutes after antigen challenge in sensitized guinea pigs. There was a significant correlation between the individual percent change of nasal airway resistance and volume or minimum cross-sectional area. Histamine, 10(2) to 10(5) micrograms/mL, caused a dose-dependent reduction in percent change of volume in the challenged side of nonsensitized guinea pigs, but not in the opposite side. These results indicate that the noninvasive acoustic reflections technique is useful in small experimental animals, especially to assess the effect of nasal cavity dimensions after the challenge of antigen or nonspecific stimuli.

The purpose of this study was to examine whether the resistance of the peak flow meter influences its recordings. One hundred and twelve subjects, (healthy nonsmokers and smokers and subjects with lung diseases) performed three or more peak expiratory flow (PEF) manoeuvres through a Fleisch pneumotachograph with and without a mini-Wright peak flow meter added in random order as a resistance in series. The results were as follows. In comparison with a pneumotachograph alone, peak flow measured with an added mini-Wright meter had a smaller within-test variation, defined as the difference between the highest and second highest values of PEF in a series of blows. The mean (SE) variation was 14 (1.3) L.min-1 and 19 (1.5) L.min-1 with and without meter added, respectively. In comparison with the pneumotachograph alone, the addition of the mini-Wright meter caused PEF to be underread, especially at high flows. The difference (PEF with meter minus PEF without meter) = -0.064 (average PEF) -8 L.min-1; R2 = 0.13. The mean difference was -7.8 (1.1) %, and increased numerically for a given PEF, when maximal expiratory flow when 75% forced vital capacity remains to be exhaled (MEF75%FVC) decreased. The reproducibility criteria for repeated measurements of peak flow are more appropriately set at 30 L.min-1 than the commonly used 20 L.min-1, because a within-test variation of less than 30 L.min-1 was achieved in 76% of the subjects without PEF meter inserted and in 88% with meter inserted, with no difference between healthy untrained subjects and patients. The resistance of the peak expiratory flow meter causes less variation in recordings but reduces peak expiratory flow, especially at high values and when the peak is large as compared with the rest of the maximal expiratory flow-volume curve.

To test the hypothesis that pressure waves in the airways propagate at the speed obtained from maximal expiratory flow we compared wave speeds (WS) associated with flow limitation and phase velocities (PV) of oscillatory pressure waves in four excised calf tracheae for transmural pressures (Ptm) between 0 and -10 kPa. WS was calculated from static area-Ptm curves using the acoustic reflection technique. PV was determined by the forced oscillation method between 16 and 1024 Hz. WS ranged from 80 to 120 m/sec slightly increasing with decreasing Ptm. PV was relatively constant between 60 and 160 AZ with values between 170 and 310 m/sec. With decreasing Ptm, PV also increased, however, at 100 HZ it was 1.5-2.5 times higher than WS at all Ptm. In one additional trachea we found that PV decreased from approximately 200 m / sec at 7 Hz to approximately 130 m / sec at 0.23 Hz approaching WS. We suggest that VP is larger than WS because of the differences in airway wall mechanics during small-amplitude oscillations and large amplitude oscillations and large amplitude unidirectional wall motion such as a forced expiration. These results may provide an additional explanation why expiratory flow during rapid breathing or expiratory transients can exceed the maximum expiratory flow-volume envelope.

Background: Nasal patency shows spontaneous variations but is also influenced by exercise and allergic conditions. These variations have not been described in detail with regard to allergy., Objectives: The purpose of this study was to examine whether these variations are different in nonallergic subjects and in subjects with nasal allergy to pollen out of the pollen season., Methods: We examined 12 of each type of subject in the winter on two days for seven hours in a climatic chamber with constant temperature and relative humidity, one day for examination of spontaneous variations and one day for examination of exercise response. Every 15 minutes the volume of the nasal cavities, minimum cross-sectional areas, and areas at fixed distances from the nostril were measured by acoustic rhinometry. Symptoms were scored by a questionnaire., Results: There were more pronounced spontaneous variations expressed as the coefficient of variation of nasal volume in allergic than in nonallergic subjects (14% against 9%, P = .004). A nasal cycle was observed in four of the nonallergic subjects and three of the allergic subjects. In the postexercise period, the spontaneous variations in the nonallergic subjects were increased but decreased in the allergic subjects. Exercise increased nasal patency more in the allergic subjects but only significantly for the cross-sectional area at 3.3 cm (105% compared with 43% in the nonallergic subjects, P = .05). In contrast, pharmacologic decongestion in the allergic subjects showed a tendency to be more pronounced for the nasal cavity volume (55% increase versus 42%, P = .08). There was no difference between the groups in nasal symptom scores., Conclusion: Allergic subjects out of the pollen season have more congested and more sensitive nasal mucosa than nonallergic subjects.

Little is known about the response of variable orifice peak flow meters to high frequency flow input. The purpose of this study was to define and test dynamic requirements for such peak flow meters. In a population sample we measured peak expiratory flow (PEF), rise time (tr), from 10-90% PEF and the duration of the flow in excess of 97.5, 95 and 90% of PEF, by use of a carefully calibrated Fleisch pneumotachograph with known and adequate frequency response. Three peak flow meters (Mini Wright, Vitalograph and Ferraris) were tested with an explosive decompression calibrator adjusted to values for PEF and tr as close as possible to the 95th and 5th percentile values, respectively, both for males and females, and with peak durations between 5 and more than 100 ms. The 95th percentile values of PEF were 597 L.min-1 for females and 894 L.min-1 for males. The 5th percentile values of tr were, respectively 55 and 45 ms. The duration of flow in excess of 95% PEF was longer than 10 ms in 99% of the subjects. For all meters, the deviation of PEF corrected for alinearity were less than 5% at a peak duration of 10 ms. We conclude that PEF, rise time, and peak duration can be used for description of dynamic properties of variable orifice meters, and that the tested meters had a satisfactory frequency response for recording PEF in mostly normal subjects.

Aerosolized histamine, delivered via a face mask, is commonly used to evaluate bronchial responsiveness in infants. To investigate nasal response to inhaled histamine we have measured nasal passage geometry in 32 infants by the use of acoustic reflections. Satisfactory data were obtained from only 17 infants (12 males, 5 females, 6.6 +/- 4.4 months), because of awakening prior to completing the study in the remaining 15 infants. Acoustic rhinometry provided nasal cavity volume at 4 cm from the entrance of the nostril (V04), the minimum cross-sectional area (Amin), and the distance from the nostril to Amin (Dmin). Nasal geometry and lung function (maximum expiratory functional residual capacity [VmaxFRC] were measured before and immediately after a histamine challenge test using rapid thoratic compression. The histamine aerosols decreased both VO4 and Amin significantly by a mean of 17% and 13%, respectively (P < 0.001). There was a small, but significant increase (mean = 0.19 cm) of Dmin in the right side only, indicating a posterior dislocation of the narrowest site with swelling of the mucous membrane. In general, we found a dose-response relationship in grouped data, with a greater fall in VO4 with increasing dose of histamine, but there was no correlation between percent fall in VO4 and VmaxFRC. This pilot study suggests that histamine aerosol affects nasal cavity geometry and that of acoustic rhinometry in infants and children warrants further investigation.

Little is known about the linearity of portable peak flow meters, or about physical gas factors affecting peak expiratory flow (PEF) readings. We therefore tested five portable peak flow meters of three types in an altitude chamber (sea level to 5,500 m) and in a climate chamber at sea level (7-37 degrees C) to determine the influence of the physical conditions of the gas on the reading of the meters. The nonlinear response of the variable orifice meters was confirmed and, when this was corrected for, the readings of these meters were found to be significantly reduced by higher altitude and lower temperature. The readings from a turbine type of peak flow meter were not affected by altitude but were reduced at low temperature. A mathematical model for the variable orifice meters could correct for both their nonlinear behaviour and the effect of gas density (altitude, temperature and humidity). The model showed that correction is not necessary for the differences in gas conditions between calibration and taking of measurements under normal laboratory conditions. All the meters tested had impedances higher than recommended (0.05 kPa.l-1.s) and this may influence PEF at high flows. The mean uncorrected PEF of six healthy subjects when measured with a Mini Wright peak flow meter at sea level and at 3,000 m fell by 5%, but the mean corrected PEF increased by 12%. This increase in PEF was about 60% of that predicted for fully density-dependent flow and agreed with the findings of other similar studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Nasal passage geometry was measured by acoustic rhinometry in 8 healthy medical students (5 males and 3 females, 21-29 years old; mean age 24 years) after 6 min in different postures of head and body. The minimum cross-sectional area (A-min) and volume between the nostril and 7 cm posteriorly were measured on both sides. When changing from sitting to horizontal the total airway dimension (i.e., the sum of A-min for the two sides) decreased by about 16% (Mean +/- SD = 0.19 +/- 0.14 cm2), and when standing up it increased by about 12% (0.14 +/- 0.13 cm2). A-min seemed more sensitive than volume to detecting postural changes. Including the variation between the cavities, the coefficient of variation (CV = SD/Mean) for area was 24.8 +/- 6.7 and for volume 22.4 +/- 6.4 for the 8 subjects. For the total nasal airway passage the corresponding figures were 12.9 +/- 3.9 and 10.9 +/- 5.5. These figures are considerably higher than for subjects measured only in the sitting position under comparable circumstances. In conclusion, our findings indicate a composite response of the nasal cavity mucosa to both systemic (hydrostatic) and local conditions, probably induced by vascular and cutaneous reflexes. These factors must be taken into account in studies of environmental, clinical, and pharmacological conditions.

Potential toxic effects of prolonged NO2 exposure below the current threshold limit value (TLV) were examined in 14 healthy, non-smoking adults. The subjects were exposed to 2,3 ppm NO2 and to clean air for five hours with a one week interval between exposures. Physiological and biochemical measurements were obtained during exposure and the following 24 hours after. A 14% decrease in serum glutathione peroxidase activity (GSH-Px) was observed 24 hours after the start of the NO2 exposure while indications of a 22% decrease in alveolar permeability were found 11 hours after the start. There were no indications of mucous membrane irritation or of decreased lung function during or after NO2 exposures. The results support the assumption that a delayed response is a feature of the human reaction to NO2 even below the current TLV of three ppm, and they stress the importance of an extended period of observation in future NO2 exposure studies.

The changes in nasal patency following a 1.5 degrees C decrease or increase in whole body temperature were measured in 8 healthy young males, during and after 30 min of immersion in a 15 degrees C cold or a 40 degrees C warm bath, breathing air at the same temperature, in a cross-over experimental design. The nasal reactions were traced by consecutive measurements of changes in nasal cavity volumes by acoustic rhinometry. Swelling of the mucosa during cooling and an almost maximal shrinkage of the mucosa during heating were indicated by respectively a decrease and an increase in nasal cavity volumes. The reactions were determined predominantly by the whole body thermal balance, but were also influenced by the temperature of the inhaled air, either enhanced, reduced or temporarily reversed. The greatest change occurred in the nasal cavity, left or right, which differed most from the final state at the beginning of exposure due to the actual state of nasal cycle.

To describe knowledge, attitude and behaviour regarding AIDS among students and employees at the University of Aarhus an anonymous self-administered questionnaire survey was conducted in April 1990. Of the 2169 and 850 questionnaires to students and employees, respectively, 1548 (71.4%) and 568 (67%) were returned. The study group had an excellent knowledge about AIDS and the transmission of HIV-virus. However, when defining "risk behaviour" in relation to transmission of HIV-virus among heterosexuals as "> or = 2 sexual partners within the past year without using condoms" 27% of the male and 20% of the female students showed risk behaviour. Among employees the rate was highest (23%) among the male scientific staff than among the remainder (17%). It is concluded that risk behaviour was not related to age and occurred in spite of the fact that 42% of the students and 31% of the employees, who showed risk behaviour were also aware of a personal risk of being infected. There is still a need for information about AIDS, and future campaigns should be directed towards all age groups as risk behaviour is not only a phenomenon among young people.

Potential toxic effects of prolonged NO2 exposure below the current threshold limit value (TLV) were examined in 14 healthy, nonsmoking adults. The subjects were exposed to 2.3 ppm NO2 and to clean air for 5 h with a 1-wk interval between exposures. Physiologic and biochemical measurements were obtained during the exposures and until 24 h after. A 14% decrease in serum glutathione peroxidase activity (GSH-Px) was observed 24 h after the start of the NO2 exposure, while indications of a 22% decrease in alveolar permeability were found 11 h after the start. There were no indications of mucous membrane irritation or of decreased lung function during or after NO2 exposures. The results support the assumption that a delayed response is a feature of the human reaction to NO2 even below the current TLV of 3 ppm, and they stress the importance of an extended period of observation in future NO2 exposure studies.

Adult volunteers were exposed to 25 ppm (75 mg/m3) diethylamine in a climate chamber for 15 min in order to study the acute nasal reactions to an exposure equivalent to the present threshold limit value-short-term exposure limit. Changes in nasal volume and nasal resistance were measured by acoustic rhinometry and by rhinomanometry. Acute change in nasal volume, usually seen as acute nasal mucosa response to thermal stimuli, was not observed, nor was an acute change in nasal airway resistance. In a subsequent experiment, the aim was to measure acute sensory effects. Exposure to a concentration increasing from 0 to 12 ppm took place for 60 min, equal to an average concentration of 10 ppm (30 mg/m3). A moderate to strong olfactory response and distinct nasal and eye irritation were observed. In spite of considerable individual variation, the results were in agreement with sensory effect estimates obtained from animal studies.

The purpose of this study was to measure trigeminal sensitivity of the eyes to irritative exposures and to examine the influence of individual characteristics, e.g., gender, age, and smoking, on this sensitivity. During an experimental study, 158 of 2,025 randomly selected volunteers were examined for sensory irritation threshold in the eyes to carbon dioxide (CO2). Eyes were exposed to progressive concentrations of CO2 (10, 20, 40, 80, and 160 ml/l), until the subject claimed a distinct irritation. Each exposure level lasted 2 min. A special exposure mask system was used for eyes-only exposure. No significant dependence of gender or smoking was found, but subjects who were less than 40 y of age were more sensitive than were the elderly subjects. Subjects who reported frequent "sick building syndrome" irritation symptoms had lower thresholds (i.e., higher sensitivity). The CO2 threshold was related to skin irritation sensitivity, i.e., response to lactic acid smeared on the cheek, and there were indications that occupational stress was associated with low thresholds. Studies of irritation to n-decane indicate that the CO2 threshold may be an important factor in the prediction of individual sensitivity to irritation from airborne pollutants. The CO2 threshold of the eyes may be of value in the evaluation of hypersensitivity to indoor air pollution. Furthermore, the threshold may be used to assess important relationships between the different trigeminal innervated areas, e.g., skin and eyes. Finally, the method has the advantage of avoiding interference from olfactory stimulation.

A cross-sectional study of respiratory disorders and atopy in Danish textile industry workers was conducted to survey respiratory symptoms throughout the textile industry, to estimate the association of these disorders with atopy, and to study dose-response relationships within the cotton industry. Workers at cotton mills, a wool mill, and a man-made fiber (MMF) mill were examined. Four hundred nine (90%) of the 445 workers participated in this survey, i.e., 253, 62, and 94 workers at the cotton mills, the wool mill, and the MMF mill, respectively. An interview designed to assess the prevalence of common respiratory and allergic symptoms was given to all workers willing to participate, and blood samples were drawn. Lung function measurements determined a baseline FEV1, FVC and the change in FEV1 and FVC during work hours on a Monday. The working environment was examined for dust, bacteria, endotoxins, and molds, and the exposure was estimated for each participant. The mean personal samples of airborne respirable dust and respirable endotoxin were highest in the cotton industry, i.e., 0.17-0.50 mg/m3 and 9.0-126 ng/m3 respectively, whereas mold spores were found in the highest concentrations in the wool mill: 280-791 colony-forming units (cfu)/m3. Only small concentrations of microorganisms were found in the MMF mill. The mean change in FEV1% and FVC% was greatest among atopic individuals in both cotton and wool industry and other textile industries although the differences were not significant. FEV1% and FVC% in the cotton workers were significantly associated with the cumulative exposure to respirable endotoxin. Byssinosis was diagnosed only in the cotton industry. We found a dose-response relationship between endotoxin exposure and byssinosis, and a significant association between A-1-A serum concentrations less than or equal to 35 mumol/liter and byssinosis, a finding we are further evaluating in subsequent studies.

The nose with normal feeling of nasal patency, and no gross structural changes has been described in 82 individuals by acoustic rhinometry. Curves for one and both sides of the nasal cavity and before and after decongestion have been recorded. We have found that the minimal cross-sectional area (MCA) is located anteriorly in the nasal cavity; in some subjects it is localized at the head of the inferior turbinate and in other subjects more anteriorly at the nasal valve. After decongestion MCA moves even more anteriorly. Beyond the MCA the dimension of the nasal cavity increases, with maximal effect of decongestion at 4 cm from nostrils. Decongestion increases the total volume of the nasal cavity by 35%.

Ten healthy subjects (four men and six women) were subjected to localized skin cooling by submersion for 5 min of both feet and, in another experiment, one hand and forearm into ice-cold water. Repeated measurements of nasal cavity volumes by a new method, acoustic rhinometry, showed characteristic patterns ranging from marked increases in volumes lasting the entire exposure period to transient monophasic or biphasic responses to no change at all. The pattern in individual subjects was reproducible with the two methods of cooling, and it could be characterized by five types when related to baseline measurements during the preexposure period. Because of large minute-to-minute variations, probably determined by local differences and fluctuations in blood flow in tissues through the nose, evaluation of induced changes in the nasal cavity volume cannot be based on single measurements as has frequently been done in the past by using rhinomanometry as the experimental method. The mechanisms behind the characteristic patterns in immediate human nasal response to local skin cooling challenge remains to be explored.

We used acoustic rhinometry to assess the geometry of the nasal cavity. The cross-sectional area of the nasal cavity as a function of distance from the nostrils was obtained. Seventeen patients with hypertrophy of the inferior turbinate and septal deviations were examined preoperatively and postoperatively; 34 normal subjects served as controls. The cross-sectional area at the anterior part of the nose suggested that skeletal hypertrophy of the inferior turbinate might be expected in the side opposite the main septal deviation. Unilateral inferior turbinoplasty seems advisable.

The purpose of the present study was to evaluate the relation between photographically assessed changes in eye redness and sensory eye irritation in 17 patients suffering from hayfever, provoked by increasing doses of birch pollen in the eye. Pre- and post-exposure diapositives were compared in a randomized and double blind design by a panel of five members. By evaluating the photographs we found a high reproducibility between panel members and for repeated evaluation by the individual panel member. Furthermore, we found that the photographic method was more sensitive for measurements of changes in eye redness than the observations normally performed during such conjunctival provocation tests. The correlations of the objective findings with the symptoms reported were good at high pollen doses, but at lower doses of birch pollen (about half the effective dose) a decreased eye redness was observed. We found that sensory irritation (often expressed as dryness) measured simultaneously by questionnaires, in general occurred before any increased eye redness. The study indicates that photographic measurement of eye redness is reproducible, sensitive, unbiased and therefore a useful tool in environmental studies. Furthermore we demonstrated that the relation between eye redness and eye irritation is interestingly biphasic and may need further clarification.

This study evaluated whether formaldehyde, at concentrations similar to those found in the indoor environment, could produce adverse effects on the lower airway of 15 asthmatic persons with documented bronchial hyperresponsiveness who were exposed for 90 min in a climate chamber to clean air containing formaldehyde vapor at levels of 0.85 mg/m3, 0.12 mg/m3, and 0.008 mg/m3. No significant changes in forced expiratory volume in 1 sec (FEV1), airway resistance (Raw), specific airway resistance (SRaw), and flow-volume curves could be detected during formaldehyde exposure. Furthermore, histamine challenge tests performed immediately after formaldehyde exposure showed no evidence of changes in bronchial reactivity. No late reactions were registered during the first 14-16 hr after exposure. The results suggest that residential levels of formaldehyde are of minor importance in the emergence of pulmonary symptoms. Discrepancies between the present study and previous data may be due to differences in environmental conditions.

In order to evaluate the possible effects of respiratory muscle training in patients with neuromuscular disease, we examined the cardiopulmonary response in 13 patients and 17 healthy controls by recording flow volume curves, ECG and alveolar carbon dioxide levels and collecting mixed expiratory air in Douglas bags. The cardiopulmonary response of our patients was not significantly different from that of the controls, and therefore we see no reason to avoid muscle training in patients with such disease.

The use of a photoionisationdetector (PID) for measurement of alveolar concentrations of gases and vapours was evaluated during a human exposure experiment with toluene. Two other methods, the standard gaspipette method and the gasbag /charcoal method, was tested for comparison. The best method appeared to be the PID-method. The major disadvantage in using this instrument was the missing selectivity towards individual compounds in a mixed atmosphere. In all other respects, the method is just as good as or better than the standard gaspipette method and the gasbag method. Results from 40 measurements with the three methods on 16 persons were examined statistically, and the average toluene absorption at 100 ppm exposure levels was estimated to be 1.6 mg/min.

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.

The purpose of this investigation was to determine whether inhalation of a freon gas mixture, the propellant of the commercial metered-dose aerosols, consisting of freon 11, freon 12, and freon 114, reduces the bronchodilating effects of inhaled salbutamol or ipratropium bromide or causes cardiac arrhythmias in control, asthmatic and bronchitic subjects. FEV1 and flows measured at different lung volumes on the maximal effort expiratoryflow-volume curve were measured during a period of 6 h. Inhalation of freon caused no significant overall reduction in the salbutamol and ipratropium bromide response in any group. Arrhythmias only occurred among the asthmatic and bronchitic patients, and were most frequent after salbutamol. Ventricular extrasystoles occurred in three cases, all after salbutamol and in two of these in combination with freon inhalation. In one patient there was furthermore hyposia and hypercapnia. The combination of the effects of hypoxia, hypercapnia, catecholamines and freon on the heart is therefore a more likely cause of arrhythmia than the effect of freon alone.

Sixty-two subjects selected among 287 persons with indoor air complaints were exposed to a standard mixture of 22 different organic gases and vapors normally found in Danish houses. Persons were randomly assigned to one of four exposure groups, and each subject stayed during the test day from 10:00 AM to 4:00 PM under standardized conditions in a climate chamber. During exposure the blink frequency was recorded, and after exposure the tear fluid contents of serum albumin, potassium, and sodium were measured. It was found that the persons had an increased concentration of serum albumin in the tear fluid, and that exposure to high concentrations of organic gases and vapors induced a tear reflex-mediated dilution of the tears.

8 normals, 8 asthmatics and 8 bronchitics inhaled comparable doses of ipratropin and salbutamol. Five different flow-volume parameters were measured before and at intervals from 3 to 360 minutes after inhalation, on a total number of 2880 maximal effort expiratory flow-volume curves. Arterial blood gas tensions were measured before and 60 minutes after inhalation. In all parameters a significant larger effect (p less than 0.05) of ipratropin was found in normals, but in different time intervals. The parameter FEV1 and MEF at 50% of FVC showed the largest effect of salbutamol during the interval from 3 to 60 minutes in the asthma patients. None of the parameters showed significant difference in drug effects in the bronchitis patients. The findings suggested a more peripheral action of ipratropin than of salbutamol in the normals. No significant change in gas tensions were found after inhalation in any of the three groups.

In a study of 75 workers employed in a tobacco factory producing cheroots we measured cellular contents of tear fluid, redness of eyes, discomfort, total (0-5.7 mg/m3) and respirable dust in the breathing zone and total ambient dust by stationary sampling (0.08-1.0 mg/m3). A matched group of 50 office workers in a telephone company (total ambient dust concentration between 0.08-0.13 mg/m3) was similarly examined as referents. We found a difference between the two companies with regard to cell counts, with tobacco workers having the largest numbers except for lymphocytes. Among tobacco workers we furthermore found that the number of cuboidal and columnar epithelial cells increased during the day. The increase of cuboidal cells, however, occurred mainly in a small group of tobacco workers exposed to the highest concentrations of tobacco dust (mean = 1.26 mg/m3). No difference in the sensation of eye irritation was found between companies, but increased irritation in the morning was associated with increased exposure to total dust during the workshift among tobacco workers. A dose-dependent difference in photographically measured eye redness was found among the tobacco workers. It could not be explained by differences in tobacco smoking, sex, age, sleeping habits or use of glasses. Irritation of lips and upper airways as reported by questionnaire were more common in tobacco workers than in referents. In conclusion the tobacco workers, more often than the referents, had complaints and objective changes in the mucous membranes of the eyes. These may be related to tobacco dust exposure.

A total of 2,880 maximum expiratory flow-volume curves were performed in a controlled double-blind cross-over examination designed to evaluate the bronchodilating effects of two different nebulized doses of salbutamol (1.75 and 0.875 mg) and ipratropium bromide (0.175 and 0.0875 mg) inhaled by 8 normal, 8 asthmatic, and 8 bronchitic subjects. FEV1, FVC, and flows at 50% FVC and at three fixed volumes below TLC have been measured over a period of 6 h on the maximum expiratory flow-volume curve. In the normal subjects, salbutamol seems to have a smaller bronchodilating effect than ipratropium bromide both at high and low lung volumes. After salbutamol the average initial FEV1 increased from 4.0 to 4.3 liters, whereas after ipratropium bromide it increased to 4.4 liters. In our asthmatic patients the initial response to salbutamol was much larger than to ipratropium bromide. After salbutamol FEV1 increased from 1.8 to 2.7 liters in 60 min, whereas after ipratropium bromide it increased to 2.4 liters in 120 min. In our bronchitic patients the difference between the two drugs seems to be very small. After both drugs FEV1 increased from 1.6 to 2.1 liters. The choice of drug for treatment of the condition would then depend on how well the individual patients tolerate the two drugs.

In each of ten healthy young subjects breathing different concentrations of CO2 in O2, four alveolar CO2-tension levels were obtained, ranging from about 20 mmHg when hyperventilating in O2 to 50 mmHg. Maximum expiratory flows at 60% total lung capacity were measured at each level and corrected for the influence of the expired gas on the flow. The corrected maximum flow decreased significantly when the alveolar CO2 tension was below 30-35 mmHg, while there was only slight or no influence of CO2 on the maximal flow when the tension was above 35 mmHg. The decrease is taken as evidence of a constrictor effect on peripheral bronchi of hypocapnia.

By means of a pilot-static tube airway compliance curves describing the cross-sectional area (A) as a function of transmural pressure (Ptm) were constructed for several locations in the elastic airway of a mechanical model of the lung. From these curves local relations between elastic recoil pressure of the lung (Pel) and maximal expiratory flow (Vmax) were calculated and compared with the experimentally determined Pel-Vmax curve for the entire airway, i.e. all parts in series. Theory and experiments showed that the latter was the lower borderline of all the local Pel-Vmax curves. This means that the maximal flow through the entire airway at a given Pel is determined by the segment of the airway, having the smallest Vmax, just as the maximal strength of a chain is determined by its weakest link. The relation between the critical transmural pressure (Ptm-) and the corresponding cross-sectional area (A-) was derived from the experimental Pel-Vmax curve. This Ptm--A- curve had a composed appearance, which was found to reflect parts of the different local Ptm-A curves and transitions between them because of movement of the flow limiting site within the airway. The Ptm--A- curve depends on the elastic properties of the flow limiting segment, and the slope of this curve (dA-/dPtm-) is the compliance of the flow limiting segment. Significant frictional pressure losses upstream from the site of flow limitation caused underestimation of both A- and dA-/dPtm-, but downstream pressure losses had no influence on the Ptm--A- curve.

We have constructed a calibration device which simulates a maximum expiratory flow, and which can also be used to determine quantitatively the frequency response and linearity of flow recording equipment. It consists of a pressure chamber full of copper chips serving as a heat exchanger. When inflated to twice the atmospheric pressure, it delivers 8.2 l of air during deflation. Deflation is released by a falling weight. The time tS between 10% and 90% of the peak expiratory flow out of the chamber (PEFR) can be varied between 10 ms and 90 ms. PEFR up to 19 l X s-1 can be obtained by changing the size of an orifice in the outlet line. The calibrator was tested with a Fleisch no 4 pneumotachograph linear up to 15 l X s-1. The coefficient of variation of PEFR (12.2 l X s-1) and FVC (8.2 l) was 2% and 1% respectively for 10 consecutive deflations. The frequency response in terms of tS of the tested equipment can be evaluated from the flow-volume curve produced by the calibrator. Examination of tS in 50 medical students shows that tS of the equipment should be less than about 20 ms in order to correctly measure PEFR. By means of a single deflation, the linearity of the total recording system can be tested over a range of flows because the flow signal of the calibrator is declining almost linearly with time.

The critical transmural pressure (Ptm) is defined as the transmural pressure of the airway at the site where and when flow is limited during a forced expiration. According to the presented theory, the maximal expiratory flow (Vmax) can be calculated from the relation between Ptm and the corresponding cross-sectional area of the airway (A). By means of a pitot-static tube, Ptm-A curves were constructed for several locations in the elastic airway of a mechanical model. From these curves local Vmax was calculated at different values of Ptm and compared with actual flow, i.e. measured Vmax for the entire airway. In the downstream part of the airway, the actual flow equalled calculated Vmax at most Ptm values. The site of flow limitation, being the most upstream point where actual flow equals calculated local Vmax could therefore be located. Theory and experiments showed positive as well as negative Ptm not influenced by change in upstream or downstream resistance. Flow limitation could therefore be initiated at distending as well as compressing pressures across the wall of the airway. V was regarded as a function of Ptm and the elastic recoil pressure of the lung (Pel). Measured and calculated iso-Pel, Ptm-V curves agreed well with one major exception: when Ptm less than Ptm measured curves were distorted due to a concomitant downstrean compression of the collapsible airway.

We have studied the mechanisms determining the residual volume (RV), by inducing temporary changes in RV through respiratory manoeuvres and bronchodilation. Four asthmatic and 5 normal subjects inhaled placebo, salbutamol, and ipratropium bromide, and performed maximum expiratory manoeuvres after partial and maximal inspiration. RV and static lung pressure-volume measurements were made in each experiment. After bronchodilation, RV increased in both groups after a maximal inspiration, while bronchodilatation, as such, decreased RV in both groups. We also found unexpectedly that in the asthmatic patients, the static transpulmonary pressure (Pst) at low lung volumes increased after bronchodilatation. Our findings can be explained if bronchodilators open-up closed airways, and if a preceding maximal inspiration decreases the elastic recoil pressure of the lungs causing a change of the lung volume at which airway closure occurs. The results also support that Pst at low lung volume is influenced by airway closure and underestimates the elastic recoil pressure of the lungs, even in normal subjects. We postulate that the increase in Pst at low lung volumes after bronchodilatation is due to smaller amounts of trapped gas.

Maximal expiratory flow rate (Vmax) was measured at 20, 35, 50, 65, and 80% vital capacity in 4 young healthy subjects breathing air, SF6/O2, and He/O2 mixtures. The flows of SF6/O2 and He/O2 were corrected to normal alveolar gasflow by means of only the density of the gases. The values for normal alveolar gasflow and corrected SF6/O2 flow were identical at 35% VC and larger volumes while the values for normal alveolar gasflow and corrected He/O2 flow were not. The results indicate that in young healthy subjects it is possible to correct Vmax at lung volumes above 35% VC for the changes induced by an increase in density of the gas breathed, provided viscosity is not much changed. Without correction, Vmax after O2-breathing will be underestimated by about 6%, compared with Vmax for normal alveolar gas, whereas a change in alveolar CO2 concentrations between 3 and 9% only causes a 1% decrease of Vmax.

In ten normal young subjects four alveolar O2-concentration levels ranging from about 7% to 95% were obtained by breathing different concentrations of oxygen in nitrogen at a constant alveolar CO2-concentration of about 5%. Maximum expiratory flows at 60% TLC were measured at each level and corrected for the influence of the expired gas density on flow. The corrected maximum flows were not significantly different, which is taken as evidence of no effect of oxygen on tone of peripheral bronchi.