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  • American Physiological Society  (6)
  • Hildebrandt, Jacob  (6)
  • 1
    Online Resource
    Online Resource
    CO 2 relaxes parenchyma in the liquid-filled rat lung
    American Physiological Society ; 2007
    In:  Journal of Applied Physiology Vol. 103, No. 2 ( 2007-08), p. 710-716
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 103, No. 2 ( 2007-08), p. 710-716
    Abstract: CO 2 regulation of lung compliance is currently explained by pH- and CO 2 -dependent changes in alveolar surface forces and bronchomotor tone. We hypothesized that in addition to, but independently of, those mechanisms, the parenchyma tissue responds to hypercapnia and hypocapnia by relaxing and contracting, respectively, thereby improving local matching of ventilation (V̇a) to perfusion (Q̇). Twenty adult rats were slowly ventilated with modified Krebs solution (rate = 3 min −1 , 37°C, open chest) to produce unperfused living lung preparations free of intra-airway surface forces. The solution was gassed with 21% O 2 , balance N 2 , and CO 2 varied to produce alveolar hypocapnia (Pco 2 = 26.1 ± 2.4 mmHg, pH = 7.56 ± 0.04) or hypercapnia (Pco 2 = 55.0 ± 2.3 mmHg, pH = 7.23 ± 0.02). The results show that lung recoil, as indicated from airway pressure measured during a breathhold following a large volume inspiration, is reduced ∼30% when exposed to hypercapnia vs. hypocapnia ( P 〈 0.0001, paired t-test), but stress relaxation and flow-dependent airway resistance were unaltered. Increasing CO 2 from hypo- to hypercapnic levels caused a substantial, significant decrease in the quasi-static pressure-volume relationship, as measured after inspiration and expiration of several tidal volumes, but hysteresis was unaltered. Furthermore, addition of the glycolytic inhibitor NaF abolished CO 2 effects on lung recoil. The results suggest that lung parenchyma tissue relaxation, arising from active elements in response to increasing alveolar CO 2 , is independent of (and apparently in parallel with) passive tissue elements and may actively contribute to V̇a/Q̇ matching.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/japplphysiol.00128.2006
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2007
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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  • 2
    Online Resource
    Online Resource
    Shunt and ventilation-perfusion distribution during partial liquid ventilation in healthy piglets
    American Physiological Society ; 1997
    In:  Journal of Applied Physiology Vol. 82, No. 3 ( 1997-03-01), p. 933-942
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 82, No. 3 ( 1997-03-01), p. 933-942
    Abstract: Mates, Elisabeth A., Jacob Hildebrandt, J. Craig Jackson, Peter Tarczy-Hornoch, and Michael P. Hlastala. Shunt and ventilation-perfusion distribution during partial liquid ventilation in healthy piglets. J. Appl. Physiol.82(3): 933–942, 1997.—Replacing gas in the lung with perfluorocarbon fluids (PFC) and periodically ventilating with a gas [partial liquid ventilation (PLV)] has been shown to improve oxygenation in models of respiratory distress syndrome. We hypothesized that the addition of PFC to healthy lungs would result in shunt, diffusion impairment, and increased ventilation-perfusion (V˙a/Q˙) heterogeneity. Previously, Mates et al. showed that O 2 shunt and arterial-alveolar CO 2 difference increased linearly with dose in piglets given graded intratracheal doses of PFC (10, 20, and 30 ml/kg followed by mechanical ventilation with 100% O 2 ) (E. A. Mates, J. C. Jackson, J. Hildebrandt, W. E. Truog, T. A. Standaert, and M. P. Hlastala. In: Oxygen Transport to Tissue XVI, 1994, p. 427–435). Here we reportV˙a/Q˙ distribution in the same animals, showing a 50% increase inV˙a/Q˙ heterogeneity during PLV independent of PFC dose. Ventilation heterogeneity was the major factor in this increase, and there was no significant change in dead space ventilation. We also report on five animals given a single 20 ml/kg dose of PFC and followed for 3 h. They showed an increase in shunt during PLV but no change in arterial-alveolar CO 2 difference.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.1997.82.3.933
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1997
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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  • 3
    Online Resource
    Online Resource
    Determination of regional ventilation and perfusion in the lung using xenon and computed tomography
    American Physiological Society ; 2001
    In:  Journal of Applied Physiology Vol. 91, No. 4 ( 2001-10-01), p. 1741-1749
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 91, No. 4 ( 2001-10-01), p. 1741-1749
    Abstract: We propose a model to measure both regional ventilation (V˙) and perfusion (Q˙) in which the regional radiodensity (RD) in the lung during xenon (Xe) washin is a function of regional V˙ (increasing RD) and Q˙(decreasing RD). We studied five anesthetized, paralyzed, mechanically ventilated, supine sheep. Four 2.5-mm-thick computed tomography (CT) images were simultaneously acquired immediately cephalad to the diaphragm at end inspiration for each breath during 3 min of Xe breathing. Observed changes in RD during Xe washin were used to determine regional V˙ and Q˙. For 16 mm 3 , Q˙ displayed more variance than V˙: the coefficient of variance of Q˙ (CV Q˙ ) = 1.58 ± 0.23, the CV of V˙ (CV V˙ ) = 0.46 ± 0.07, and the ratio of CV Q˙ to CV V˙ = 3.5 ± 1.1. CV Q˙ (1.21 ± 0.37) and the ratio of CV Q˙ to CV V˙ (2.4 ± 1.2) were smaller at 1,000-mm 3 scale, but CV V˙ (0.53 ± 0.09) was not. V˙/Q˙ distributions also displayed scale dependence: log SD of V˙ and log SD of Q˙ were 0.79 ± 0.05 and 0.85 ± 0.10 for 16-mm 3 and 0.69 ± 0.20 and 0.67 ± 0.10 for 1,000-mm 3 regions of lung, respectively. V˙ and Q˙ measurements made with CT and Xe also demonstrate vertically oriented and isogravitational heterogeneity, which are described using other methodologies. Sequential images acquired by CT during Xe breathing can be used to determine both regional V˙ and Q˙ noninvasively with high spatial resolution.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.2001.91.4.1741
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2001
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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  • 4
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    Online Resource
    Ventilation heterogeneity in excised lobes: effect of tidal volume
    American Physiological Society ; 2000
    In:  Journal of Applied Physiology Vol. 88, No. 5 ( 2000-05-01), p. 1659-1671
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 88, No. 5 ( 2000-05-01), p. 1659-1671
    Abstract: Although several factors are known to influence nonuniformity of ventilation, including lung mechanical properties (regional structure and compliance), external factors (chest wall, pleural pressure, heart), and ventilatory parameters (tidal and preinspiratory volume, flow rate), their relative contributions are poorly understood. We studied five excised, unperfused, canine right-middle lobes under varied levels of tidal volume (Vt), thus eliminating many factors affecting heterogeneity. Multiple-breath washouts of N 2 were analyzed for anatomic dead space volume (Vd anat ), nonuniformity of N 2 washout, and nonuniformity between joined acinar regions vs. that occurring between larger joined regions. Approximately 80% of ventilation heterogeneity was found among joined acinar regions at resting levels of Vt, but increasing Vt reduced intra-acinar heterogeneity to about 25% of that found at resting levels. Increasing Vt had essentially no effect on Vd anat and heterogeneity among larger joined regions. The results indicate that the magnitude of Vt is a major influence on the dominant intra-acinar component of ventilation heterogeneity and that Vt effects on Vd anat are likely due to perfusion and/or influences normally external to the lobar structure.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.2000.88.5.1659
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2000
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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  • 5
    Online Resource
    Online Resource
    Changes in bronchial and pulmonary arterial blood flow with progressive tension pneumothorax
    American Physiological Society ; 1996
    In:  Journal of Applied Physiology Vol. 81, No. 4 ( 1996-10-01), p. 1664-1669
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 81, No. 4 ( 1996-10-01), p. 1664-1669
    Abstract: Carvalho, Paula, Jacob Hildebrandt, and Nirmal B. Charan.Changes in bronchial and pulmonary arterial blood flow with progressive tension pneumothorax. J. Appl. Physiol. 81(4): 1664–1669, 1996.—We studied the effects of unilateral tension pneumothorax and its release on bronchial and pulmonary arterial blood flow and gas exchange in 10 adult anesthetized and mechanically ventilated sheep with chronically implanted ultrasonic flow probes. Right pleural pressure (Ppl) was increased in two steps from −5 to 10 and 25 cmH 2 O and then decreased to 10 and −5 cmH 2 O. Each level of Ppl was maintained for 5 min. Bronchial blood flow, right and left pulmonary arterial flows, cardiac output (Q˙t), hemodynamic measurements, and arterial blood gases were obtained at the end of each period. Pneumothorax resulted in a 66% decrease inQ˙t, bronchial blood flow decreased by 84%, and right pulmonary arterial flow decreased by 80% at Ppl of 25 cmH 2 O ( P 〈 0.001). At peak Ppl, the majority ofQ˙t was due to blood flow through the left pulmonary artery. With resolution of pneumothorax, hemodynamic parameters normalized, although abnormalities in gas exchange persisted for 60–90 min after recovery and were associated with a decrease in total respiratory compliance.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.1996.81.4.1664
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1996
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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  • 6
    Online Resource
    Online Resource
    Modeling diffusion limitation of gas exchange in lungs containing perfluorocarbon
    American Physiological Society ; 1999
    In:  Journal of Applied Physiology Vol. 86, No. 1 ( 1999-01-01), p. 273-284
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 86, No. 1 ( 1999-01-01), p. 273-284
    Abstract: We reported changes in alveolar-arterial Po 2 gradient, ventilation-perfusion heterogeneity, and arterial-alveolar Pco 2 gradient during partial liquid ventilation (PLV) in healthy piglets (E. A. Mates, P. Tarczy-Hornoch, J. Hildebrandt, J. C. Jackson, and M. P. Hlastala. In: Oxygen Transport to Tissue XVII, edited by C. Ince. New York: Plenum, 1996, vol. 388, p. 585–597). Here we develop two mathematical models to predict transient and steady-state (SS) gas exchange conditions during PLV and to estimate the contribution of diffusion limitation to SS arterial-alveolar differences. In the simplest model, perfluorocarbon is represented as a uniform flat stirred layer and, in a more complex model, as an unstirred spherical layer in a ventilated terminal alveolar sac. Time-dependent solutions of both models show that SS is established for various inert and respiratory gases within 5–150 s. In fluid-filled unventilated terminal units, all times to SS increased sometimes by hours, e.g., SF 6 exceeded 4 h. SS solutions for the ventilated spherical model predicted minor end-capillary disequilibrium of inert gases and significant disequilibrium of respiratory gases, which could explain a large portion of the arterial-alveolar Pco 2 gradient measured during PLV (14). We conclude that, during PLV, diffusion gradients for gases are generally small, except for CO 2 .
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/jappl.1999.86.1.273
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1999
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
    Library Location Call Number Volume/Issue/Year Availability
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