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Pawel Sliwinski - One of the best experts on this subject based on the ideXlab platform.

  • modified Campbell Diagram to assess respiratory muscle action in speech
    1999
    Co-Authors: Sharn Johnston, Sheng Yan, Pawel Sliwinski, Peter T Macklem
    Abstract:

    Ten normal and four moderate to severe stutterers participated in the study. Pleural (Ppl) and abdominal (Pab) pressure was studied using oesophageal and gastric balloon catheter systems and VL (VL) was studied using magnetometry. The classical Campbell Diagram was modified by plotting Pab versus VL. In a preliminary study we determined whether a surrogate curve could be substituted for the true curve in the Campbell Diagram. We obtained true relaxation curves in six subjects. We obtained surrogate chest wall relaxation curves by joining the Pab value at functional residual capacity (FRC) to a point on the dynamic expiratory Pab, VL curve where Pab had decreased to half its maximum inspiratory excursion. In order to obtain the mirror image of the elastic recoil curve of the lung subjects breathed slowly from FRC to total lung capacity. Dynamic Pab, VL and Ppl, VL measurements during quiet breathing and speech were superimposed on static lung and chest wall curves. The simultaneous plot of Ppl and Pab provided a continuous measure of transdiaphragmatic pressure as a function of VL. We inferred non-diaphragmatic muscle recruitment vis-a-vis the diaphragm by the relationship of Pab to Ppl and Pab to the relaxation curve. We compared dynamic Ppl during phonation with that during breath-holding with the glottis open at the same VL, as an estimate of subglottic pressure (Psg). Analysis of variance testing showed that the true, surrogate and predicted relaxation slopes were not significantly different. The strategies that stutterers used to speak were either higher or lower VL than normal subjects and they had a different pattern of respiratory muscle recruitment. Stutterers were unable to achieve the appropriate degree of recruitment to develop and maintain a normal Psg for conversational speech and this contributed to dysfluency. We conclude that the quiet breathing loops can provide a reasonable approximation to the relaxation curve in normal healthy subjects and that modifications to the Campbell Diagram provide useful means of measuring Psg and assessing respiratory muscle recruitment patterns.

  • comparison of static and dynamic intrinsic positive end expiratory pressure using the Campbell Diagram
    1996
    Co-Authors: Sheng Yan, Bengt Kayser, M Tobiasz, Pawel Sliwinski
    Abstract:

    Intrinsic positive end-expiratory pressure (PEEPi) due to dynamic hyperinflation has been measured as a plateau airway opening pressure during airway occlusion (PEEPi,stat). PEEPi has also been dynamically determined as a fall in esophageal pressure (Pes) before the inspiratory flow starts (PEEPi,dyn). The aims of the current study were to systematically compare PEEPi,stat and PEEPi,dyn and to explain the underlying mechanisms of their difference. The study was performed in healthy subjects with dynamic hyperinflation induced by expiration through a Starling resistor. The Campbell Diagram was constructed for each subject by determining the static pressure-volume curves of the lung (Pst,[l]) and chest wall (Pst,[w]). For a given end-expiratory volume, PEEPi,stat was measured on the Campbell Diagram as the pressure difference between Pst(w) and -Pst(l). PEEPi,dyn was measured as mentioned above. The effects of respiratory muscle recruitment on PEEPi,dyn were estimated by the Pes values when Pes started to fall relative to Pst(w). We found that: (1) there was a great variability of the PEEPi,dyn/PEEPi,stat ratio among and within subjects; (2) expiratory muscle recruitment was evident on most occasions; (3) persistent inspiratory muscle activity during expiration was present in some subjects; (4) the Pes values at the start of inspiratory flow were frequently on the left of -Pst(l), which contributed to the difference between PEEPi,stat and PEEPi,dyn and implied a greater dynamic than static elastance presumably due to viscoelastic properties; (5) chest wall distortions characterized by inflation of the abdomen with deflation of the rib cage during the initial inspiratory efforts were observed in three subjects. In conclusion, interpretation of PEEPi,dyn needs to be cautious because both expiratory and tonic inspiratory muscle activities that lead to significant over- or underestimation of PEEPi by PEEPi,dyn, respectively, are associated with acute dynamic hyperinflation. In addition, the effects of viscoelastic properties and chest wall distortions on PEEPi,dyn need to be further investigated.

Sheng Yan - One of the best experts on this subject based on the ideXlab platform.

  • modified Campbell Diagram to assess respiratory muscle action in speech
    1999
    Co-Authors: Sharn Johnston, Sheng Yan, Pawel Sliwinski, Peter T Macklem
    Abstract:

    Ten normal and four moderate to severe stutterers participated in the study. Pleural (Ppl) and abdominal (Pab) pressure was studied using oesophageal and gastric balloon catheter systems and VL (VL) was studied using magnetometry. The classical Campbell Diagram was modified by plotting Pab versus VL. In a preliminary study we determined whether a surrogate curve could be substituted for the true curve in the Campbell Diagram. We obtained true relaxation curves in six subjects. We obtained surrogate chest wall relaxation curves by joining the Pab value at functional residual capacity (FRC) to a point on the dynamic expiratory Pab, VL curve where Pab had decreased to half its maximum inspiratory excursion. In order to obtain the mirror image of the elastic recoil curve of the lung subjects breathed slowly from FRC to total lung capacity. Dynamic Pab, VL and Ppl, VL measurements during quiet breathing and speech were superimposed on static lung and chest wall curves. The simultaneous plot of Ppl and Pab provided a continuous measure of transdiaphragmatic pressure as a function of VL. We inferred non-diaphragmatic muscle recruitment vis-a-vis the diaphragm by the relationship of Pab to Ppl and Pab to the relaxation curve. We compared dynamic Ppl during phonation with that during breath-holding with the glottis open at the same VL, as an estimate of subglottic pressure (Psg). Analysis of variance testing showed that the true, surrogate and predicted relaxation slopes were not significantly different. The strategies that stutterers used to speak were either higher or lower VL than normal subjects and they had a different pattern of respiratory muscle recruitment. Stutterers were unable to achieve the appropriate degree of recruitment to develop and maintain a normal Psg for conversational speech and this contributed to dysfluency. We conclude that the quiet breathing loops can provide a reasonable approximation to the relaxation curve in normal healthy subjects and that modifications to the Campbell Diagram provide useful means of measuring Psg and assessing respiratory muscle recruitment patterns.

  • comparison of static and dynamic intrinsic positive end expiratory pressure using the Campbell Diagram
    1996
    Co-Authors: Sheng Yan, Bengt Kayser, M Tobiasz, Pawel Sliwinski
    Abstract:

    Intrinsic positive end-expiratory pressure (PEEPi) due to dynamic hyperinflation has been measured as a plateau airway opening pressure during airway occlusion (PEEPi,stat). PEEPi has also been dynamically determined as a fall in esophageal pressure (Pes) before the inspiratory flow starts (PEEPi,dyn). The aims of the current study were to systematically compare PEEPi,stat and PEEPi,dyn and to explain the underlying mechanisms of their difference. The study was performed in healthy subjects with dynamic hyperinflation induced by expiration through a Starling resistor. The Campbell Diagram was constructed for each subject by determining the static pressure-volume curves of the lung (Pst,[l]) and chest wall (Pst,[w]). For a given end-expiratory volume, PEEPi,stat was measured on the Campbell Diagram as the pressure difference between Pst(w) and -Pst(l). PEEPi,dyn was measured as mentioned above. The effects of respiratory muscle recruitment on PEEPi,dyn were estimated by the Pes values when Pes started to fall relative to Pst(w). We found that: (1) there was a great variability of the PEEPi,dyn/PEEPi,stat ratio among and within subjects; (2) expiratory muscle recruitment was evident on most occasions; (3) persistent inspiratory muscle activity during expiration was present in some subjects; (4) the Pes values at the start of inspiratory flow were frequently on the left of -Pst(l), which contributed to the difference between PEEPi,stat and PEEPi,dyn and implied a greater dynamic than static elastance presumably due to viscoelastic properties; (5) chest wall distortions characterized by inflation of the abdomen with deflation of the rib cage during the initial inspiratory efforts were observed in three subjects. In conclusion, interpretation of PEEPi,dyn needs to be cautious because both expiratory and tonic inspiratory muscle activities that lead to significant over- or underestimation of PEEPi by PEEPi,dyn, respectively, are associated with acute dynamic hyperinflation. In addition, the effects of viscoelastic properties and chest wall distortions on PEEPi,dyn need to be further investigated.

Charis Roussos - One of the best experts on this subject based on the ideXlab platform.

  • contribution of expiratory muscle pressure to dynamic intrinsic positive end expiratory pressure validation using the Campbell Diagram
    2000
    Co-Authors: Spyros Zakynthinos, Theodoros P Vassilakopoulos, Epaminondas Zakynthinos, Antonis Mavrommatis, Charis Roussos
    Abstract:

    In spontaneously breathing (SB) patients expiratory muscle contraction leads to an overestimation of dynamic intrinsic PEEP (PEEP(i),dyn). To quantify this overestimation, PEEP(i),dyn measured with the esophageal balloon technique was corrected for the increase in Pga over the course of expiration (Pga,exp rise), for the whole decay of Pga during inspiration (Pga,total decay) or for the part of Pga decay restricted between the onset of inspiratory effort and the point of zero flow (Pga,zf decay). Corrections were compared with the reference PEEP(i),dyn (PEEP(i),dyn ref ), calculated by using the Campbell Diagram. In 15 ventilator-dependent, SB, and actively expiring patients, we found that the difference PEEP(i),dyn - Pga, total decay (mean +/- SD, 5.7 +/- 1.9 cm H(2)O) was quite similar to PEEP(i),dyn ref (5.3 +/- 1.9 cm H(2)O). Their mean difference was 0. 37 cm H(2)O with limits of agreement -0.09 to 0.83 cm H(2)O, indicating strong agreement between these methods. PEEP(i),dyn - Pga, exp rise (6.0 +/- 2.1 cm H(2)O) was also similar to PEEP(i),dyn ref. Their mean difference was 0.72 cm H(2)O with limits of agreement -1. 69 to 3.13 cm H(2)O, indicating good agreement. In contrast, mean difference of PEEP(i),dyn - Pga,zf decay and PEEP(i),dyn ref was 3. 14 cm H(2)O with limits of agreement -0.46 to 6.74 cm H(2)O, indicating lack of agreement. The error in measurement due to the subtraction of Pga,zf decay from PEEP(i),dyn (i.e., [PEEP(i),dyn - Pga,zf decay] - PEEP(i),dyn ref ) was proportional to the intensity of expiratory muscle contraction, as expressed by the Pga,exp rise (r = 0.903, p < 0.001). We conclude that in actively expiring patients an adequate correction of PEEP(i),dyn for the overestimation caused by expiratory muscle contraction can be made by subtracting either Pga,total decay or Pga,exp rise from PEEP(i), dyn, the former achieving the best performance.

Theodoros P Vassilakopoulos - One of the best experts on this subject based on the ideXlab platform.

  • understanding wasted ineffective efforts in mechanically ventilated copd patients using the Campbell Diagram
    2008
    Co-Authors: Theodoros P Vassilakopoulos
    Abstract:

    Wasted or ineffective efforts are inspiratory efforts that fail to trigger the ventilator [1]. Nearly 25% of mechanically ventilated patients exhibit ineffective efforts which are even more frequent in COPD patients [2]. The pathophysiology of wasted efforts can be illustratively presented using the Campbell Diagram.

  • contribution of expiratory muscle pressure to dynamic intrinsic positive end expiratory pressure validation using the Campbell Diagram
    2000
    Co-Authors: Spyros Zakynthinos, Theodoros P Vassilakopoulos, Epaminondas Zakynthinos, Antonis Mavrommatis, Charis Roussos
    Abstract:

    In spontaneously breathing (SB) patients expiratory muscle contraction leads to an overestimation of dynamic intrinsic PEEP (PEEP(i),dyn). To quantify this overestimation, PEEP(i),dyn measured with the esophageal balloon technique was corrected for the increase in Pga over the course of expiration (Pga,exp rise), for the whole decay of Pga during inspiration (Pga,total decay) or for the part of Pga decay restricted between the onset of inspiratory effort and the point of zero flow (Pga,zf decay). Corrections were compared with the reference PEEP(i),dyn (PEEP(i),dyn ref ), calculated by using the Campbell Diagram. In 15 ventilator-dependent, SB, and actively expiring patients, we found that the difference PEEP(i),dyn - Pga, total decay (mean +/- SD, 5.7 +/- 1.9 cm H(2)O) was quite similar to PEEP(i),dyn ref (5.3 +/- 1.9 cm H(2)O). Their mean difference was 0. 37 cm H(2)O with limits of agreement -0.09 to 0.83 cm H(2)O, indicating strong agreement between these methods. PEEP(i),dyn - Pga, exp rise (6.0 +/- 2.1 cm H(2)O) was also similar to PEEP(i),dyn ref. Their mean difference was 0.72 cm H(2)O with limits of agreement -1. 69 to 3.13 cm H(2)O, indicating good agreement. In contrast, mean difference of PEEP(i),dyn - Pga,zf decay and PEEP(i),dyn ref was 3. 14 cm H(2)O with limits of agreement -0.46 to 6.74 cm H(2)O, indicating lack of agreement. The error in measurement due to the subtraction of Pga,zf decay from PEEP(i),dyn (i.e., [PEEP(i),dyn - Pga,zf decay] - PEEP(i),dyn ref ) was proportional to the intensity of expiratory muscle contraction, as expressed by the Pga,exp rise (r = 0.903, p < 0.001). We conclude that in actively expiring patients an adequate correction of PEEP(i),dyn for the overestimation caused by expiratory muscle contraction can be made by subtracting either Pga,total decay or Pga,exp rise from PEEP(i), dyn, the former achieving the best performance.

Dufour Régis - One of the best experts on this subject based on the ideXlab platform.

  • Dynamique d'un rotor embarqué soumis à des excitations combinées de la base
    2011
    Co-Authors: Dakel Mzaki, Baguet Sébastien, Dufour Régis
    Abstract:

    The proposed on-board rotor model is based on Timoshenko beam finite elements. It takes into account the six translations and rotations of the rigid support and the geometric asymmetry of disks and/or shaft. Thus the obtained equations of motion contain time-varying parametric terms which can lead to lateral dynamic instability. The influence of combined rotational and translational support motions is analyzed by means of Campbell Diagram and rotor stability chart

  • Dynamique d'un rotor embarqué soumis à des excitations combinées de la base
    2011
    Co-Authors: Dakel M. Zaki, Baguet Sébastien, Dufour Régis
    Abstract:

    National audienceThe proposed on-board rotor model is based on the Timoshenko beam finite elements. It takes into accountthe six translations and rotations of the rigid support and the geometric asymmetry of disks and/or shaft.Thus the obtained equations of motion contain time-varying parametric terms which can lead to lateraldynamic instability. The influence of combined rotational and translational support motions is analyzed bymeans of Campbell Diagram and rotor stability chart.Le modèle de rotor embarqué proposé est basé sur les éléments finis de la poutre de Timoshenko. Il prend encompte les six translations et rotations du support rigide et la dissymétrie géométrique des disques et/ou del’arbre. Ainsi les équations du mouvement obtenues comportent des termes paramétriques variables dans letemps qui peuvent conduire à une instabilité dynamique latérale. L’influence des mouvements de rotation etde translation combinés du support est analysée par le Diagramme de Campbell et la carte de stabilité durotor