[Oscillometry, rheology and morpho-oscillometry. Importance and respective advantages].
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Coronary Disease↗
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Oscillometry of radial artery in acrocyanosis and cold sensitivity.
Acrocyanosis is reassessed on the basis of 34 new patients with diagnostic clinical features. The most useful tests are the skin temperature differences (STD) between wrist and end of fingers (or ankle and end of toes) and oscillometry over the radial and dorsalis pedis and posterior tibial arteries. Capillaroscopy of the conjunctival and nailfold vessels is useful in half the patients. Capillary resistance was not helpful. STD of 1.5 degrees C or more between skin of wrist or ankle and fingertip or toetip, is usually associated with more severe disease and capillary abnormalities on microscopy, and with reduced oscillometry (to 1 or less) over the radial arteries and dorsalis pedis and posterior tibial arteries. Reduced oscillometry is more associated with abnormalities than the other tests, and more than STD. The work of Mulvany and his colleagues suggests an explanation for the low oscillometry. Larger vessels than the arterioles and digital vessels can become resistance vessels in various circumstances. It is likely that the radial artery and vessels of similar diameter can temporarily act as resistance vessels in patients with acrocyanosis in a low temperature environment.
Adolescent↗
[Assessment of lung function using forced impulse oscillometry in cystic fibrosis patients].
The aim of this study was to evaluate the usefulness of forced impulse oscillometry to measure airway resistance in patients with cystic fibrosis. Thirty-four patients (20 men) with a mean age of 15 +/- 4 years were studied. All patients underwent forced impulse oscillometry, forced spirometry and body plethysmography. Correlations among spirometric, plethysmographic and oscillometric variables were analyzed. We found a statistically significant relation between both forced expiratory volume in one second (FEV1) and total airway resistance (Raw) and the following oscillometric variables: impedance (Zrs), resonance frequency (Fres), resistance to 5 hertz (Rrs5) and reactance to 5 hertz (Xrs5). The measurements that correlated most highly with classical pulmonary function tests were Zrs and Xrs5. Both resistance (Rrs) and reactance (Xrs) of the respiratory system were dependent on frequency. Their correlation with FEV1 and Raw were therefore lower when frequencies above 5 hertz were used. We conclude that airway resistances of cystic fibrosis patients can be adequately estimated by forced impulse oscillometry. This technique is a promising test of pulmonary function in such patients.
Adolescent↗
Validation of impulse oscillometry in Friesian and Blue Belgian calves with respect to changes in extrathoracic upper airway resistance.
Impulse oscillometry (IOS) was compared with conventional pulmonary function techniques (using oesophageal balloon and airflow measurements). Healthy Friesian (FR) and Blue Belgian (BB) calves were examined in different conditions of extrathoracic airway resistance (physiological and vertical head position). Higher resistance values were detected in BB calves compared with FR calves with both conventional and forced oscillation techniques in both head positions. Upper airway narrowing was characterised by increasing resistance values without changes in frequency dependence. Measuring input impedance in animals using a face mask, a considerable capacitive shunt of the upper airways (including the capacitive components of the mask) has to be taken into account. Even if the absolute value of this capacitive component is constant, its influence on the measurement results increases with growing frequency and with an increase in upper airway resistance. In conclusion, (1) impulse oscillometry is sensitive to upper airway resistance changes and (2) face mask capacitance is important and has frequency dependent effects on the respiratory impedance.
Airway Resistance↗
Analysis of respiratory mechanics by impulse oscillometry in non-sedated and diazepam-sedated swine.
Analysis of respiratory mechanics using impulse oscillometry is applicable to sedated, or non-sedated (trained) pigs when they are fixed in a sling. In this study, the influence of the following sources of variability on measurement results was examined: (i) sedation with diazepam; (ii) body weight of animals (ranging in age: 40 to 102 days); and (iii) time of the measurement (circadian influences). The following parameters were examined: respiratory rate (RR), tidal volume (v(t)), spectral resistance, reactance and coherence, each at 5, 10, 15 and 20 Hz (R5,...R20, X5,...X20, CO5...CO20, respectively), distal respiratory resistance (Rdist), and proximal airway resistance (Rprox). After sedation (using 1.5 mg diazepam per kg body weight), RR and v(t) decreased significantly. There was a significant improvement of CO5, CO10 and CO15. Increase in body weight was strongly correlated to v(t), furthermore to spectral resistance parameters. Impulse oscillometry system (IOS) parameters showed only slight non-significant alterations in dependency on the time of day. In consequence, different sources of variability must be taken into account when performing IOS measurements in swine.
Age Factors↗
The effects of inhaled albuterol and salmeterol in 2- to 5-year-old asthmatic children as measured by impulse oscillometry.
The functional assessment of the response to bronchodilators in 2- to 5-year-old asthmatic children is technically difficult. For this reason, there have been no reports on the effects of long-acting bronchodilators, such as salmeterol, in this age group. Of the several techniques available for measuring resistance to airflow, forced oscillation remains the most adaptable to young children and the most practical for research and clinical use. In this stud we used the Jaeger MasterScreen Impulse Oscillometry System to assess the response of 2 to 5 year-old asthmatic children to an inhaled long-acting bronchodilator, salmeterol, by comparing it to the effect of a standard dose of the short-acting bronchodilator, albuterol. We performed a placebo-controlled, randomized, crossover study in 10 children aged 2 to 5 years who had a history of physician-diagnosed asthma and who were not on regular controller therapy. At weekly intervals after baseline measurements of reversibility, each child received two inhalations from an albuterol metered-dose inhaler (MDI) with a spacer (200 microg), or placebo MDI with spacer, or two inhalations from a salmeterol MDI (50 microg), or 50 microg from a salmeterol Diskus. Measurements were obtained at 5, 30, 60, 360, and 540 min, the last time interval only on the salmeterol days. Based on previous studies, total respiratory system reactance at 5 Hz (X5), calculated by the MasterScreen computer from mouth pressure and flow data, was used as the primary efficacy variable. The mean intra-individual variability in X5 was 10.5% (range 3.6% to 17.9%). The mean (SE) changes from baseline X5 at each time point were as follows: for placebo, 9.6 (3.0), 10.1 (2.6), 5.1 (2.9), 6.1 (3.5), p=0.36 vs. baseline; after treatment with albuterol, 32.7 (3.8), 53.9 (1.2), 47.3 (5.4), 18.1 (5.8), p<0.01 vs. baseline at all time points; after salmeterol MDI, 16 (6.4), 28.9 (5.2), 32.7 (3.9), 34.6 (4.4), 31.2 (4.8), p<0.05 at 60, 360, and 540 min; and after salmeterol Diskus, 16.4 (4.0), 16.9 (6.6), 27.8 (5.9), 28.6 (5.6), 33.8 (4.0), p<0.05 at 540 min. No significant adverse events or electrocardiographic changes were noted at any time. Impulse oscillometry is an acceptable method of assessing airway responses to bronchoactive drugs in this age group. Compared to albuterol and to its effect in older children and adults, the response to salmeterol Diskus appears to be somewhat blunted in this age group. The MasterScreen system is well suitedfor pharmacodynamic studies and clinical investigations in pre-school-aged children.
Administration, Inhalation↗
Method specificity of non-invasive blood pressure measurement: oscillometry and finger pulse pressure vs acoustic methods.
1. The agreement of blood pressure measurements by stethoscope auscultation (SBPa, DBPa-IV and DBPa-V), oscillometry (Dinamap; SBPo, and DBPo) and digital photoplethysmography (Finapres; SBPf, and DBPf) with the graphical analysis of the analogue microphone signals of vascular wall motion sound (SBPg and DBPg) was evaluated in eight healthy subjects in the presence of responses to the intravenous infusion of 1 microgram min-1 isoprenaline. 2. In general, there was good agreement between the SBP/DBP-measurements based on auscultatory Korotkoff-I- and IV-criteria and the reference method; the average method difference in estimating the isoprenaline responses for SBPa-SBPg was: -1.1, 95% CI: -5.4 to 3.1 mm Hg with a within-subject between-method repeatability coefficient (REP) of 11.6 mm Hg and for DBPa-IV-DBPg: 3.5, 95% CI: -0.5 to 6.5 mm Hg, REP: 11.5 mm Hg. The ausculatation of Korotkoff-V substantially overestimated the isoprenaline induced reduction of DBP: method difference DBPa-V-DBPg: -11.3, 95% CI: -17.8 to -4.7 mm Hg, REP: 31.8 mm Hg. 3. Oscillometry yielded good approximations for the SBP response to isoprenaline (average method difference SBPo-SBPg: -2.9, 95% CI: -9.0 to 3.3 mm Hg, REP: 17.6 mm Hg) but was poorly sensitive with regard to the DBP responses: method difference DBPo-DBPg: 6.5, 95% CI: -1.3 to 14.3 mm Hg, REP: 25.7 mm Hg. 4. Whilst the finger pulse pressure agreed well with regard to DBP (method difference for the DBP responses to isoprenaline: DBPf-DBPg: 1.8, 95% CI: -5.1 to 8.6 mm Hg, REP: 18.5 mm Hg) it was rather unsatisfactory with regard to SBP (method difference SBPf-SBPg: -14.1, 95% CI: -28.2 to -0.1 mm Hg, REP: 49.9 mm Hg).(ABSTRACT TRUNCATED AT 250 WORDS)
Adrenergic beta-Antagonists↗
Measurement of respiratory impedance by impulse oscillometry--effects of endotracheal tubes.
Impulse Oscillometry is a new, noninvasive method to measure respiratory impedance, i.e. airway resistance and reactance at different oscillation frequencies. These parameters are potentially useful for the monitoring of respiratory mechanics in the critically ill patent with respiratory dysfunction. The endotracheal tube, used to mechanically ventilate these patients, however, represents an additional nonlinear impedance that introduces artifacts into the measurements. The objective of this work was therefore to investigate the effects of clinically available endotracheal tubes on resistance and reactance of an in vitro analogue of the respiratory system. Additionally, the effects of decreasing the compressible gas volume in this experimental model, as a simulation of decreased lung capacity and compliance, was investigated. Impulse oscillometric measurements of the test analogue gave highly reproducible results with and without an endotracheal tube. The tubes had significant influence on the measurement of the test object at all frequencies investigated. Changes of low frequent reactance were negligible - at least if repetitive measurements of the same system are performed - for realistic measurement of airway resistance, a correction of the tube impedance or measurement of the pressure distal of the tube is required. Resistance increased and low frequent reactance decreased significantly with decreasing gas volume. These changes were of magnitudes higher than the variations due to the introduction of the endotracheal tubes. Our results suggest that changes of respiratory reactance measured with impulse oscillometry may be used as a monitoring parameter in intubated patients.
Airway Resistance↗
Oscillometry and direct blood pressure: a comparative clinical study during deliberate hypotension.
Oscillometry using an automatic monitor was compared with invasive blood pressure monitoring in 21 patients scheduled for surgery under general anaesthesia with deliberate hypotension. Six ranges of mean blood pressure measurements were studied, two of which were hypotensive. An excellent correlation was found between the two methods (systolic: r = 0.94; mean: r = 0.93; diastolic: r = 0.88) but there was a large variability among individual subjects. For systolic, diastolic and mean intra-arterial readings above an approximative value of 10.64 KPa (80 mmHg), the oscillometric monitor was found to underestimate blood pressure. Inversely, it was found to overestimate blood pressure for intra-arterial readings under the approximative value of 10.8 KPa (80 mmHg). We conclude that the non-invasive monitor represents a good trend estimation of the invasive radial blood pressure technique, but that wide inter-individual variability and the overestimation of blood pressure below an approximative value of 10.64 KPa (80 mmHg) precludes interchange of techniques when absolute values are considered, especially during controlled hypotension. However, oscillometry could represent a better estimate of central aortic pressure.
Adult↗
Within- and between-day variability of respiratory impedance, using impulse oscillometry in adolescent asthmatics.
The objectives of the present study were to: 1) assess spirometric indices and respiratory impedance with forced oscillation (FO), using impulse oscillometry (IOS) in clinically stable asthmatic children over 3 consecutive days; 2) assess FO reactance (X), using an integrated index and resistance (R) separately during inspiration and expiration; and 3) assess effects on FO of hand support of cheeks vs. no hand support. Our hypotheses were: 1) because of increased sensitivity, IOS manifests day-to-day variability not demonstrable by spirometry; 2) IOS R during expiration exceeds that during inspiration; and 3) hand support of cheeks affects IOS R and X only minimally. We obtained triplicate twice-daily measures of IOS R and X in asthmatic adolescents at summer camp, in a convenience sample of children willing, with parental permission, to undergo repeated testing on consecutive days. Subjects received all medications between 6:30-7:30 AM, and were bronchodilated at time of testing. Subjects underwent IOS tests without hand support of cheeks, followed by tests with both hands supporting cheeks. ANOVA and regression analyses were used to discern technique differences.Significant differences in IOS inspiratory R5, R5 - R15 (frequency dependence of R), and low frequency reactance area (AX) occurred across 3 days, but spirometric indices were unchanged. Inspiratory R at 5 Hz (R5) was significantly smaller than expiratory R5 (P < 0.0001). ANOVA revealed no significant differences between hand and facial muscle cheek support for IOS R and X below 15 Hz, but significant differences occurred above 15 Hz. In conclusion, inspiratory R5, R5 - R15, and AX are sensitive measures for detecting changes in bronchomotor tone in adolescent asthmatic subjects, while expiratory R5 may be influenced by additional factors. Manual support of cheeks does not appear to affect IOS indices of peripheral airway obstruction in adolescent asthmatics. IOS is a practical method for quantifying respiratory mechanics, and its potential role in disease management warrants further study.
Adolescent↗
Impulse oscillometry: a measure for airway obstruction.
The impulse oscillometry system (IOS) was introduced as a new technique to assess airflow obstruction in patients who are not able to perform forced breathing maneuvers, e.g., subjects with cerebral palsy or severe mental retardation, and young children. This study evaluates the sensitivity and specificity of IOS parameters to quantify changes in airflow obstruction in comparison with forced expiratory volume in the first second (FEV(1)) and peak expiratory flow (PEF) measurements. Measurements of FEV(1), PEF, and resistance (R) and reactance (X) at frequencies of 5-35 Hz were performed in 19 children with asthma before, during, and after methacholine challenge and subsequent bronchodilatation. All parameters changed significantly during tests. Values of R5 and R10 correlated with FEV(1) (r = -0.71 and -0.73, respectively, P < 0.001), as did values of X5 and X10 (r = 0.52 and 0.57, respectively, P < 0.01). Changes in R preceded changes in PEF and FEV(1) during methacholine challenge. The area under the receiver operating characteristic (ROC) curve to predict a 15% fall in FEV(1) showed better sensitivity and specificity for R5 (area under the curve, 0.85) compared to PEF (0.79) or R10 (0.73). We conclude that IOS parameters can be easily used as an indirect measure of airflow obstruction. This might be helpful in patients who are not able to perform forced breathing maneuvers. In individual subjects, R values measured at 5 Hz showed to be superior to PEF measurements in the detection of a 15% fall in FEV(1).
Adolescent↗
The diagnosis value and its implication of impulse oscillometry in obstructive sleep apnea syndrome patients.
The change of measurements of impulse oscillometry (IOS) in obstructive sleep apnea syndrome (OSAS) patients and its mechanism were observed. The respiratory impedance was measured by using IOS technique and polysomnography (PSG) was monitored synchronously in 36 OSAS patients, 14 patients with chronic obstructive pulmonary disease (COPD) and 12 normal controls. Results showed that R20 in OSAS group was significantly higher than in COPD group and control group (P < 0.01). R5-R20 in OSAS group was lower than that in COPD group, but significantly higher than that in control group (P < 0.01). The levels of R20 and R5-R20 were positively correlated with severity degree of the disease. In addition, apnea-hyponea index (AHI) was positively correlated with R5 and R20 with the correlation index (r)being 0.66 and 0.86 respectively. The lowest SO2 was negatively correlated with R5 and R5-R20, with r being -0.66 and -0.79 respectively. The mean SO2 was negatively correlated with R5 and R5-R20 with r being -0.81 and -0.69 respectively. IOS technique could be used as a valuable tool for assessing the degree of upper airway obstruction in the patients with OSAS, and could help to explore its pathological mechanism.
Adult↗
Respiratory mechanics in conscious swine: effects of face mask, head position and bronchoconstriction evaluated by impulse oscillometry.
Airway obstruction in pigs (sedated or non-sedated) fixed in a sling was studied using impulse oscillometry (IOS). (i) Vertical flexion of the pig's head was used to simulate an artificial obstruction of the upper airways. (ii) Bronchial obstruction was induced by inhaling differing quantities of an aerosol produced from 0.33% carbachol solution. The ventilatory pattern was examined by measuring respiratory rate (RR) and tidal volume (V(t)). To evaluate respiratory mechanics, impedance parameters resistance (R) and reactance (X) as well as coherence (Co) were examined, each at frequencies of 5, 10, 15, 20, 25 and 35 Hz. Using a simple 7-element-model introduced by J. Mead [Physiological Review 41 (1961) 281], distal respiratory resistance (R(dist)), proximal airway resistance (R(prox)), and additional shunt compliance (C(a)) of the animal's snout and the air inside the facemask were evaluated. By fitting this model to the primary measured impedance spectra, the influence of the face mask could be eliminated in the model calculation to allow assessment of the real respiratory impedance. This recalculation made clear that the facemask had an influence on the spectral course of R and X, depending on the clinical situation, and the upper frequency range was altered the most. Under conditions of (i) upper airway obstruction, especially the X values were distorted by facemask almost over the whole frequency range. Once the data were corrected for the mask, resistance was increased across all frequencies by a fixed amount while reactance was not affected. Under (ii) bronchial airway obstruction (bronchospasm) caused the resistance spectrum to be increased mainly in the lower frequency range. This became visible in both, originally measured impedance spectra and spectra after correction of the mask influence. The reactance course (originally measured and recalculated) decreased at all frequencies during bronchospasm. Coherence over the whole frequency range was lowered at both bronchial and upper airway obstruction.
Airway Obstruction↗
Comparative evaluation of impulse oscillometry and a monofrequency forced oscillation technique in clinically healthy calves undergoing bronchochallenges.
Multifrequency impulse oscillometry (IOS) was compared with a monofrequency forced oscillation technique (MFO) in calves undergoing experimentally induced bronchoconstriction and subsequent bronchodilatation. The dynamic lung compliance (Cdyn) was also measured by conventional methods. For each test, the baseline mean and the responses to saline, a bronchoconstrictive agent (carbachol) and a bronchodilator (fenoterolhydrobromide) were calculated. Using the IOS, the information was markedly frequency-dependent. The resistance (R) and the magnitude of respiratory impedance (Z) were only sensitive at 5 Hz, leading to negative frequency dependence of these parameters as an indicator of peripheral airway obstruction. A high sensitivity for reactance (X) and phase angle phi values was observed between 5 and 20 Hz. For MFO (10 Hz), the parameters Ros (which includes resistive and capacitive components of the respiratory system), phase shift (psi), and the oscillatory derived compliance of the respiratory system (Crs) were of the greatest clinical potential. Crs showed a significant coefficient of linear correlation (r = 0.88, P < 0.001) with Cdyn. At the 10 Hz test frequency similar results were observed with MFO and IOS, suggesting that for healthy calves the measurement effect of an impulse is not significant. With respect to peripheral airway calibre, a test frequency less than 10 Hz appeared to be most sensitive and least variable.
Airway Resistance↗
Reference ranges for blood pressure in preschool Australians, obtained by oscillometry.
OBJECTIVE: To derive reference centiles for blood pressure in children aged 1-6 years which seek to address shortcomings in available reference ranges. METHODS: Prospective cohort study of 2876 children in Perth, Western Australia, commenced in 1989 with serial blood pressure measurements through early childhood obtained by oscillometry under standardized conditions. RESULTS: Gender-specific reference centile charts for systolic and diastolic blood pressure, (i) across ages 1-6 years and (ii) across the range of corrected Body Mass Index values at ages 1, 3 and 6 years, were generated by fitting linear models with both fixed and random effects. CONCLUSIONS: Reference values for blood pressure for young children are of clinical use and may be of long-term predictive value.
Blood Pressure↗
Mechanics of the respiratory system in healthy newborn calves using impulse oscillometry.
Arterial blood gases, acid-base balance and respiratory function tests using impulse oscillometry (IOS) were performed on 40 clinically healthy newborn calves during the first 24 hours of life to evaluate their respiratory adaptation to extrauterine life. Gas exchange efficiency of the lung was significantly improved with time and was accompanied by the correction of the mixed acidosis observed at birth and by significant changes in respiratory mechanics. Major changes were detected within the first 6 hours. The significant decrease in resistance (R) and the increase in reactance (X) with time, demonstrate the improvement in respiratory mechanics of both upper and lower airways, and reflect the increase in lung volume, the improved lung tissue elasticity and/or distribution of the ventilation. Respiratory mechanical, arterial blood gases and acid-base balance data provided in this study describe a successful respiratory adaptation to extrauterine life in healthy newborn calves.
Acid-Base Equilibrium↗
Airway resistance in chronic heart failure measured by impulse oscillometry.
BACKGROUND: Patients with chronic heart failure (CHF) complain of breathlessness and fatigue on exertion, have reduced peak oxygen consumption (pV(O(2))), and an increased ventilatory response to exercise (V(E)/V(CO(2)) slope). These limitations correlate with abnormalities of spirometry (forced expiratory volume in 1 second [FEV(1)] and forced ventilatory capacity [FVC]). Increased airway resistance by increasing the work of breathing might contribute to exercise intolerance in CHF. METHODS: Impulse oscillometry (IOS) measures airway resistance and lung compliance independently of respiratory muscle strength and patient compliance. Sound waves of varying frequencies are sent into the lungs and the amplitude and phase shift of the reflected waves give a measure of airway resistance (R) and reactance (X). Twenty-three CHF patients and 18 controls underwent peak exercise testing with metabolic gas analysis and had airway resistance assessment using the Jaeger (Würtzberg, Germany) IOS system. RESULTS: Patients had a lower pV(O(2)) (18.7 (4.0) v 39.2 (8.3) mL x kg x min; P < .0001), elevated V(E)/V(CO(2)) slope (41.6 (8.1) v 27.4 (2.9)), and lower FEV(1) (2.4 (0.4) v 3.2 (0.7) L/min; P = .0001) and FVC (3.3 (0.7) v 4.1 (1.1) L; P < .005) than controls. R and X correlated with spirometric abnormalities and were different between patients and controls (R at 5 Hz 0.44 (0.16) v 0.30 (0.15) kPa (L/s); P < .005 and X at 5 Hz -0.16 (0.08) v -0.09 (0.08) kPa (L/s); P < .05). R at 5 Hz correlated with pV(O(2)) (0.46; P = .0025) and V(E)/V(CO(2)) slope (0.43; P < .05). CONCLUSION: CHF patients have elevated airway resistance and reduced reactance measured with IOS compared with control subjects.
Aged↗
Impulse oscillometry provides an effective measure of lung dysfunction in 4-year-old children at risk for persistent asthma.
BACKGROUND: Objective lung function measurements are routinely used to diagnose and manage asthma, but their utility for young children has not been defined. OBJECTIVE: Bronchodilator responses were measured by means of impulse oscillometry (IOS) and compared with conventional spirometry to determine the value of lung function measures in 4-year-old asthma-prone children. METHODS: The study participants were in the Childhood Asthma Prevention Study (National Institute of Health/National Institute of Allergy and Infectious Diseases) and at risk for asthma. At age 4 years, concurrent asthma was determined by using a previously validated modified American Thoracic Society questionnaire. Children performed IOS and spirometry before and after albuterol administration and underwent skin prick testing to 13 common allergens to assess atopy. IOS measures were as follows: airways resistance at 5 Hz and 10 Hz, airways reactance at 5 Hz and 10 Hz, and resonant frequency. RESULTS: Asthmatic patients versus nonasthmatic patients significantly differed in their IOS-assessed bronchodilator responses through Delta resistance at 5 Hz (medians, 27% vs 17%; P =.02) and Delta resistance at 10 Hz (24% vs 16%; P =.03). Because atopic children who have frequent wheezing are at risk for persistent asthma, the data were analyzed in regard to atopic patients with or without asthma. IOS strongly distinguished atopic asthmatic children through Delta resistance at 5 Hz (36% vs 13%, P =.007), Delta resistance at 10 Hz (25% vs 11%, P =.02), and Delta reactance at 10 Hz (47% vs 12%, P =.03). Conventional spirometry did not establish similar statistically significant findings. CONCLUSION: IOS bronchodilator responses are remarkably abnormal in 4-year-old children, who are most likely to have persistent asthma. IOS is a useful diagnostic tool in early asthma development and might be a helpful objective outcome measure of early interventions.
Airway Resistance↗