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  • 1
    Online Resource
    Online Resource
    Effect of body posture on respiratory impedance
    American Physiological Society ; 1988
    In:  Journal of Applied Physiology Vol. 64, No. 1 ( 1988-01-01), p. 194-199
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 64, No. 1 ( 1988-01-01), p. 194-199
    Abstract: The effects of posture on the mechanics of the respiratory system are not well known, particularly in terms of total respiratory resistance. We have measured respiratory impedance (Zrs) by the forced random noise excitation technique in the sitting and the supine position in 24 healthy subjects. Spirometry and lung volumes (He-dilution technique) were also measured in both postures. The equivalent resistance (Rrs), compliance (Crs), and inertance (Irs) were also calculated by fitting each measured Zrs to a linear series model. When subjects changed from sitting to the supine position, the real part of Zrs increased over the whole frequency band. The associated equivalent resistance, Rrs, increased by 28.2%. The reactance decreased for frequencies lower than 18 Hz and increased for higher frequencies. Consequently, Crs decreased by 38.7% and Irs increased by 15.6%. All of these parameter differences were significant (P less than 0.001). A covariance analysis showed that a significant amount of the postural change in Rrs and Crs can be explained by the reduction of functional residual capacity (FRC). This indicates that the observed differences on Zrs can in part be explained be a shift of the operating point of the respiratory system induced by the decrease in the FRC.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.1988.64.1.194
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1988
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  • 2
    Online Resource
    Online Resource
    Automatic regulation of the cuff pressure in endotracheally-intubated patients
    European Respiratory Society (ERS) ; 2002
    In:  European Respiratory Journal Vol. 20, No. 4 ( 2002-10-01), p. 1010-1013
    Details
    In: European Respiratory Journal, European Respiratory Society (ERS), Vol. 20, No. 4 ( 2002-10-01), p. 1010-1013
    Type of Medium: Online Resource
    ISSN: 0903-1936 , 1399-3003
    URL: Article
    DOI: 10.1183/09031936.02.02692001
    Language: English
    Publisher: European Respiratory Society (ERS)
    Publication Date: 2002
    detail.hit.zdb_id: 2834928-3
    detail.hit.zdb_id: 1499101-9
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  • 3
    Online Resource
    Online Resource
    Human lung impedance from spontaneous breathing frequencies to 32 Hz
    American Physiological Society ; 1994
    In:  Journal of Applied Physiology Vol. 76, No. 3 ( 1994-03-01), p. 1176-1183
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 76, No. 3 ( 1994-03-01), p. 1176-1183
    Abstract: Lung impedance (ZL) was measured from 0.1875 to 32 Hz in spontaneously breathing healthy subjects by spectral analysis of the pressure and flow signals generated simultaneously by the muscular generator of breathing and by a forced oscillation system. This method did not require cooperation from the subject to perform panting or special ventilatory maneuvers and therefore allowed us to analyze the frequency dependence of lung resistance, reactance, and elastance (-2 pi.frequency.reactance) at the physiological conditions of normal breathing. Resistance and elastance parameters were also computed by multiple linear regression of the time-domain pressure and flow data on a simple resistance-elastance model. Resistances and elastances computed at the breathing frequency by spectral analysis and by multiple linear regression were similar (nonsignificant differences 〈 4 and 10%, respectively). The results obtained when comparing ZL from the breathing component (0.1875–0.75 Hz) of the recorded signals and from the forced oscillation component (2–32 Hz) were fairly consistent. ZL (0.1875–10 Hz) was interpreted in terms of a model consisting of an airway compartment, including a resistance and an inertance, in series with a viscoelastic tissue compartment (J. Hildebrandt. J. Appl. Physiol. 28: 365–372, 1970) characterized by two parameters. The model analysis provided parameter values (resistance 2.49 +/- 0.58 hPa.l-1.s, inertance 1.70 +/- 0.29 Pa.l-1.s2, Hildebrandt parameters 4.87 +/- 2.28 and 0.73 +/- 0.99 hPa/l) consistent with the hypothesis that lung tissue in healthy humans during spontaneous breathing behaves as a viscoelastic structure with a hysteresivity of approximately 0.10.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.1994.76.3.1176
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1994
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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  • 4
    Online Resource
    Online Resource
    Lung and respiratory impedance at low frequency during mechanical ventilation in rabbits
    American Physiological Society ; 1995
    In:  Journal of Applied Physiology Vol. 78, No. 6 ( 1995-06-01), p. 2153-2160
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 78, No. 6 ( 1995-06-01), p. 2153-2160
    Abstract: We have tested in eight rabbits the feasibility of measuring respiratory (Zrs) and lung (ZL) impedances in the low-frequency domain, including below the breathing frequency (fb), during conventional mechanical ventilation (CMV). The animals were tracheotomized and ventilated with a tidal volume (VT) of 20 ml at a fb of 1 Hz. The excitation signal was provided by a flow generator connected in parallel with the ventilator; it included six components ranging from 0.45 to 14.8 Hz, which met the neither-sum-nor-difference criterion of B. Suki and K. Lutchen (IEEE Trans. Biomed. Eng. 39: 1142-1151, 1992) to minimize the influence of nonlinearities. Zrs and ZL were also measured at the same mean lung volume and with the same excitation signal both during apnea and when the ventilator signal was replaced by a sine wave with the same VT and fb (SMV). The real parts (Re) of both Zrs and ZL, as well as the effective elastances, were significantly larger during apnea than during CMV and SMV over the whole frequency range. Re(Zrs) and Re(ZL) were similar during CMV and SMV above fb but they were lower during CMV at 0.45 Hz. The latter difference seems to be related to the presence of harmonics of fb and of additional frequency components due to pulse amplitude modulation. We conclude that, because of nonlinearities, it is feasible to measure Zrs and ZL during CMV only at and above fb.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.1995.78.6.2153
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1995
    detail.hit.zdb_id: 1404365-8
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    SSG: 31
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  • 5
    Online Resource
    Online Resource
    Analog circuit for real-time computation of respiratory mechanical impedance in sleep studies
    Institute of Electrical and Electronics Engineers (IEEE) ; 1997
    In:  IEEE Transactions on Biomedical Engineering Vol. 44, No. 11 ( 1997-Nov.), p. 1156-1159
    Details
    In: IEEE Transactions on Biomedical Engineering, Institute of Electrical and Electronics Engineers (IEEE), Vol. 44, No. 11 ( 1997-Nov.), p. 1156-1159
    Type of Medium: Online Resource
    ISSN: 0018-9294
    URL: Article
    DOI: 10.1109/10.641343
    RVK:
    XA 48665
    Language: Unknown
    Publisher: Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 1997
    detail.hit.zdb_id: 2021742-0
    detail.hit.zdb_id: 2571926-9
    detail.hit.zdb_id: 2561637-7
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  • 6
    Online Resource
    Online Resource
    A correction procedure for the asymmetry of differential pressure transducers in respiratory impedance measurements
    Institute of Electrical and Electronics Engineers (IEEE) ; 1989
    In:  IEEE Transactions on Biomedical Engineering Vol. 36, No. 11 ( 1989-Nov.), p. 1137-1140
    Details
    In: IEEE Transactions on Biomedical Engineering, Institute of Electrical and Electronics Engineers (IEEE), Vol. 36, No. 11 ( 1989-Nov.), p. 1137-1140
    Type of Medium: Online Resource
    ISSN: 0018-9294
    URL: Article
    DOI: 10.1109/10.40822
    RVK:
    XA 48665
    Language: Unknown
    Publisher: Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 1989
    detail.hit.zdb_id: 2021742-0
    detail.hit.zdb_id: 2571926-9
    detail.hit.zdb_id: 2561637-7
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  • 7
    Online Resource
    Online Resource
    Respiratory input impedance in anesthetized paralyzed patients
    American Physiological Society ; 1990
    In:  Journal of Applied Physiology Vol. 69, No. 4 ( 1990-10-01), p. 1372-1379
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 69, No. 4 ( 1990-10-01), p. 1372-1379
    Abstract: Respiratory impedance (Zrs) was measured between 0.25 and 32 Hz in seven anesthetized and paralyzed patients by applying forced oscillation of low amplitude at the inlet of the endotracheal tube. Effective respiratory resistance (Rrs; in cmH2O.l-1.s) fell sharply from 6.2 +/- 2.1 (SD) at 0.25 Hz to 2.3 +/- 0.6 at 2 Hz. From then on, Rrs decreased slightly with frequency down to 1.5 +/- 0.5 at 32 Hz. Respiratory reactance (Xrs; in cmH2O.l-1.s) was -22.2 +/- 5.9 at 0.25 Hz and reached zero at approximately 14 Hz and 2.3 +/- 0.8 at 32 Hz. Effective respiratory elastance (Ers = -2pi x frequency x Xrs; in cmH2O/1) was 34.8 +/- 9.2 at 0.25 Hz and increased markedly with frequency up to 44.2 +/- 8.6 at 2 Hz. We interpreted Zrs data in terms of a T network mechanical model. We represented the proximal branch by central airway resistance and inertance. The shunt pathway accounted for bronchial distensibility and alveolar gas compressibility. The distal branch included a Newtonian resistance component for tissues and peripheral airways and a viscoelastic component for tissues. When the viscoelastic component was represented by a Kelvin body as in the model of Bates et al. (J. Appl. Physiol. 61: 873-880, 1986), a good fit was obtained over the entire frequency range, and reasonable values of parameters were estimated. The strong frequency dependence of Rrs and Ers observed below 2 Hz in our anesthetized paralyzed patients could be mainly interpreted in terms of tissue viscoelasticity. Nevertheless, the high Ers we found with low volume excursions suggests that tissues also exhibit plasticlike properties.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.1990.69.4.1372
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1990
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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  • 8
    Online Resource
    Online Resource
    A new estimator to minimize the error due to breathing in the measurement of respiratory impedance
    Institute of Electrical and Electronics Engineers (IEEE) ; 1988
    In:  IEEE Transactions on Biomedical Engineering Vol. 35, No. 12 ( 1988-Dec.), p. 1001-1005
    Details
    In: IEEE Transactions on Biomedical Engineering, Institute of Electrical and Electronics Engineers (IEEE), Vol. 35, No. 12 ( 1988-Dec.), p. 1001-1005
    Type of Medium: Online Resource
    ISSN: 0018-9294
    URL: Article
    DOI: 10.1109/10.8684
    RVK:
    XA 48665
    Language: Unknown
    Publisher: Institute of Electrical and Electronics Engineers (IEEE)
    Publication Date: 1988
    detail.hit.zdb_id: 2021742-0
    detail.hit.zdb_id: 2571926-9
    detail.hit.zdb_id: 2561637-7
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  • 9
    Online Resource
    Online Resource
    Respiratory input impedance up to 256 Hz in healthy humans breathing foreign gases
    American Physiological Society ; 1993
    In:  Journal of Applied Physiology Vol. 75, No. 1 ( 1993-07-01), p. 307-320
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 75, No. 1 ( 1993-07-01), p. 307-320
    Abstract: Currently available data concerning respiratory input impedance (Zrs) at frequencies up to 300 Hz indicate that Zrs is determined mainly by the airways and, in particular, the gas compressibility in the airways and the airway wall compliance. Hence, measurements of Zrs when breathing gases with different physical properties would be useful in investigating airway mechanics and the role of acoustic propagation. Zrs measured with a standard generator (Zst) and corrected for the upper airway shunt (Zrs*) were measured in nine healthy subjects breathing air or a gas mixture consisting of 20% O2 and 80% He or SF6. The frequency band was extended up to 256 Hz for air and He-O2 and up to 128 Hz for SF6-O2. Zrs exhibited a similar pattern for the three gases, with a shift toward low frequencies as the gas density increased. Moreover, the resonance peaks tended to be narrower and higher as the gas density increased. The second frequency of resonance for He-O2, air, and SF6-O2 were 220, 180, and 50 Hz, respectively, for Zrs* and were systematically higher for Zst. Zrs* and Zst data were interpreted in terms of a tricompartmental model that partitioned the airways into two segments: a central one featuring the acoustic propagation in the airways and a peripheral one that included bronchial wall elasticity (Farre et al. J. Appl. Physiol. 67: 1973–1981, 1989). The model was able to interpret the gas dependence of Zrs* but not that of Zst. The influence of the gas physical properties on both Zrs* and Zst confirms that total Zrs at high frequencies is basically that of the airways and that the second resonance is related mainly to the gas compressibility in the airways.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.1993.75.1.307
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1993
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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  • 10
    Online Resource
    Online Resource
    Optimized estimation of respiratory impedance by signal averaging in the time domain
    American Physiological Society ; 1992
    In:  Journal of Applied Physiology Vol. 73, No. 3 ( 1992-09-01), p. 1181-1189
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 73, No. 3 ( 1992-09-01), p. 1181-1189
    Abstract: The spontaneous breathing of a subject during measurements of respiratory impedance (Zrs) by the forced oscillation technique (FOT) induces errors that result in biased impedance estimates, especially at low frequencies. Although in standard measurements this bias may be avoided by using special impedance estimators, there are two applications of FOT for which such estimators are not useful: when a head generator is used and when measurements are made during intubation. In this paper we describe a data-processing procedure for unbiased impedance estimation for all FOT setups. The proposed estimator (Z) was devised for pseudorandom excitation and is based on time-domain signal averaging before frequency analysis. The performance of estimator Z was first analyzed by computer simulation of a head generator setup and a setup including an endotracheal tube to measure (2–32 Hz) a resistance-inertance-elastance model mimicking Zrs of a healthy subject. Second, Z was assessed during real measurements in 16 healthy subjects. The results obtained in the simulation (e.g., error in elastance was reduced from 15.6% with most conventional estimators to 3.3% with Z in simulation of head generator setup) and in the measurements in subjects (differences of less than 1.6% between Z and a reference) confirmed the theoretical lack of bias of Z and its practical suitability for the different FOT setups. In addition to its applicability in the situations in which no other unbiased estimators are available, estimator Z is also advantageous in most conventional applications of FOT, since it requires much less computing time and thus allows on-line Zrs measurements.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.1992.73.3.1181
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1992
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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