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Biomedical subjects

O F Pedersen

Publications and source records attributed to O F Pedersen.

At least 55 records · Page 3Linked to original sources
PubMed1996

Peak expiratory flow and the resistance of the mini-wright peak flow meter.

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.

Adolescent↗
PubMed1995

Wave speed during maximal expiratory flow and phase velocity from forced oscillations.

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.

Animals↗
PubMed1995

Nasal histamine challenge in nonallergic and allergic subjects evaluated by acoustic rhinometry.

Nasal patency shows spontaneous variations but is influenced by a number of factors like exercise and allergic conditions. Nasal histamine challenge has been used to define nasal hypersensitivity. We have applied acoustic rhinometry as a new objective method to study the spontaneous variations of the nasal mucosa and its response to histamine challenge in 12 nonallergic subjects and 12 subjects with nasal allergy to pollen, but out of the pollen season. Measurements of the minimum cross-sectional area and the volume of the nasal cavities were done every 15 min for 6 h. More pronounced spontaneous variations, defined by the coefficient of variation of the measurements, were encountered in the allergic than in the nonallergic subjects, especially with regard to the minimum cross-sectional areas in the nasal cavities (P < 0.02). Allergic subjects showed increased sensitivity to histamine, as compared with nonallergic subjects, during low-concentration (0.1%) challenge (P < 0.05) and a prolonged effect of histamine challenge (P = 0.01). Antihistamine (cetirizine) had a significant effect on the histamine-induced symptoms and decrease of nasal dimensions during histamine challenge, but no significant effect on pollen-induced changes. In the allergic group, the decrease in minimum area during allergen provocation correlated with the level of specific IgE (r = 0.81; P = 0.0015).

Acoustics↗
PubMed1995

Frequency response of variable orifice type peak flow meters: requirements and testing.

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.

Adult↗
PubMed1995

Spontaneous variations in congestion of the nasal mucosa.

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.

Adolescent↗
PubMed1994

Nasal response to inhaled histamine measured by acoustic rhinometry in infants.

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.

Acoustics↗
PubMed1994

Nasal cavity dimensions in the newborn measured by acoustic reflections.

The acoustic reflections technique was used to measure nasal cavity dimensions in 27 newborns. The results were expressed in terms of curves describing cross-sectional area as a function of the distance into the nose. From these curves, a mean curve with 95% confidence limits, nasal cavity volumes between the nostril and 4.5 cm into the nasal cavity (V45 = 1.05 (0.24) cm3), the cross-sectional area at the narrowest site (Amin = 0.114 (0.033) cm2), and the distance from the nostril to Amin (DAmin = 1.14 (0.47) cm), expressed as mean and SD were calculated. There was a weak correlation between Amin and length and weight at birth, but otherwise nasal cavity dimensions did not correlate with sex, race, birth weight, birth length, head circumference, or duration of gestation. Comparison of the curves from the newborns with curves from adults showed a facial growth in vertical/transverse directions (area) of 600% and anterior/posterior directions of 120%. The technique of acoustic rhinometry is noninvasive, and can be performed rapidly, and is therefore eminently suitable for pediatric application. Further investigations are needed to demonstrate the value as a diagnostic tool in pathological cases.

Acoustics↗
PubMed1994

Posture and nasal patency: evaluation by acoustic rhinometry.

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.

Acoustics↗
PubMed1994

Portable peak flow meters: physical characteristics, influence of temperature, altitude, and humidity.

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)

Adult↗
PubMed1993

[Effects of low concentrations of NO2 on alveolar permeability and glutathione peroxidase in healthy subjects].

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.

Adult↗
PubMed1993

[AIDS--knowledge, behavior and attitude at the University of Aarhus in 1990. A questionnaire study].

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.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Nasal airway geometry: comparison between acoustic reflections and magnetic resonance scanning.

To evaluate the accuracy of the acoustic reflection (AR) technique for determination of nasal cavity cross-sectional areas, the area-distance function of both sides of the nose was determined in 10 subjects and compared with magnetic resonance imaging (MRI). Interindividual variation for the correlation between MRI and AR was seen, but in general the areas from 1 to 6 cm into the nasal cavity measured by AR were larger than areas measured by MRI, especially where the surface was most convoluted. The total volume for this region was 6.47 +/- 1.83 (SD) cm3 for AR and 5.65 +/- 1.34 cm3 for MRI. It was demonstrated that this could be due to errors in calculation of the areas on the basis of MRI and AR. In the posterior part of the nasal cavity and the epipharynx, there was a convincingly higher correlation between acoustic measurements and a scan perpendicular to the assumed geometrical axis of the epipharynx than between acoustic measurements and coronal scanning. This indicates that the sound axis roughly follows the geometrical axis. In a model of two tubes (nasal cavities) joined in a larger tube (the epipharynx), closure of the posterior part of the latter revealed that the contralateral nasal cavity is likely to cause overestimation of the posterior part of the epipharynx during AR compared with MRI.

Adult↗
PubMed1993

Nasal reaction to changes in whole body temperature.

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.

Adult↗
PubMed1992

Respiratory disorders and atopy in cotton, wool, and other textile mill workers in Denmark.

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.

Animals↗