The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform
Ola Stenqvist - One of the best experts on this subject based on the ideXlab platform.
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regional intratidal gas distribution in acute lung injury and acute respiratory distress syndrome assessed by electric impedance tomography
Minerva Anestesiologica, 2010Co-Authors: K Lowhagen, Stefan Lundin, Ola StenqvistAbstract:Background. Regional tidal volume distribution and end-expiratory lung volume (EELV) distribution in patients with acute lung injury and acute respiratory distress syndrome (ALI, ARDS) have previously been investigated using computed tomograpy and electric impedance tomography (EIT). In the present study, we utilized the high temporal resolution of EIT to assess intratidal gas distribution. Methods. Sixteen ventilator patients with ALI/ARDS were studied. EIT was used for analysis of intertidal, intratidal and EELV regional distribution. Intratidal regional gas distribution (ITV) was analyzed by dividing the regional tidal impedance signal into eight iso-volume parts. Alveolar Pressure/volume curves during ongoing ventilation and volume-dependent compliance during the initial inspiration (Cini) were calculated. A low-Pressure (∼32 cm H 2 O) recruitment maneuver and a decremental PEEPtrial were implemented. Results. The increase in EELV was preferentially distributed to non-dependent lung regions. The intratidal gas distribution pattern was similar to the tidal volume distribution following increased PEEP; non-dependent distribution decreased and dependent distribution increased during inspiration. Cini increased, indicating successful recruitment. The distribution varied widely among individual patients. In one patient with a low EELV, the ITV pattern showed that non-dependent distribution increased and dependent distribution decreased. This coincided with minimal improvement in volume-dependent compliance. This patient probably needed higher recruitment Pressure. In one patient with a high baseline EELV, there was very little change in regional ITV, and non-dependent Cini decreased. This was probably a patient with low potential recruitability, who required only moderate PEEP. Conclusion. On-line intratidal gas distribution monitoring offers additional information on recruitability and optimal PEEP.
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The dynostatic algorithm accurately calculates Alveolar Pressure on-line during ventilator treatment in children
Pediatric Anesthesia, 2003Co-Authors: Soren Sondergaard, Jan Wiklund, Sigurbergur Kárason, Angela Hanson, Krister Nilsson, Stefan Lundin, Ola StenqvistAbstract:Summary Background: Monitoring of respiratory mechanics during ventilator treatment in paediatric intensive care is currently based on Pressure and flow measurements in the ventilator or at the Y-piece. The characteristics of the tracheal tube will modify the Pressures affecting the airways and alveoli in an unpredictable manner. The dynostatic algorithm (DSA), based on a one-compartment lung model, calculates the Alveolar Pressure during on-going ventilation. The DSA is based on accurate measurement of tracheal Pressure. The purpose of this study was to test the validity of the DSA in a paediatric lung model and to apply the concept in an observational clinical study in children. Methods: We validated the DSA in a paediatric lung model with linear, nonlinear Pressure flow and frequency-dependent characteristics by comparing calculated dynostatic (Alveolar) Pressures with directly measured Alveolar Pressures in the model and proximal plateau Pressure with maximum Alveolar Pressure. Sixty combinations of ventilation modes, positive end expiratory Pressures, inspiratory : expiratory ratios, volumes and frequencies were studied. A 0.25-mm fibreoptic Pressure transducer in the tube lumen was used in combination with volume and flow from ventilator signals. Clinical measurements were performed in eight patients during anaesthesia and postoperative ventilator treatment. Results: In the lung model we found a correlation coefficient between calculated and measured Alveolar Pressure of 0.93–0.99 with root mean square median values of 1 cm H2O. Distal plateau Pressure agreed well with maximum Alveolar Pressure. In the clinical situation, the algorithm provided a breath-by-breath display of the volume-dependent lung compliance and the temporal course of Alveolar Pressure during uninterrupted ventilation. Conclusions: Fibreoptic measurement of tracheal Pressure in combination with the dynostatic calculation of Alveolar Pressure provides an on-line monitoring of the effects of ventilatory mode in terms of volume-dependent compliance, tracheal peak Pressure and true positive end expiratory Pressure.
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Alveolar Pressure monitoring an evaluation in a lung model and in patients with acute lung injury
Intensive Care Medicine, 2003Co-Authors: Soren Sondergaard, Sigurbergur Kárason, S Lundin, J Wiklund, Ola StenqvistAbstract:We evaluated an algorithm for continuous on-line monitoring of Alveolar Pressure over time in a lung model with lower and upper inflection points and variable resistance ratios and in patients with acute lung injury. The algorithm is based on "static" Pressure/volume curves obtained from tracheal Pressure measurements under dynamic conditions. Experimental and clinical evaluation of algorithm in a university hospital laboratory and intensive care unit. Ten patients undergoing postoperative respiratory therapy (feasibility of tracheal measurement) and ten patients with acute lung injury undergoing ventilator treatment (evaluation of algorithm). Direct tracheal Pressure measurements with a catheter inserted through the endotracheal tube. Comparison of measured Alveolar and the dynostatic Alveolar Pressure vs. time in a lung model with changes in five ventilatory parameters. Examples of clinical monitoring are reported. In the model there was excellent agreement between Alveolar Pressures obtained by the algorithm, the dynostatic Alveolar Pressure, and measured Alveolar Pressure at all ventilator settings. For inspiratory/expiratory resistance ratios between 1:2.1–2.1:1, the dynostatic Alveolar Pressure was within ±1.5 cm H2O of measured Alveolar Pressure. In patients the technique for direct tracheal Pressure measurement using a catheter inserted through the endotracheal tube functioned satisfactorily with intermittent air flushes for cleansing. Using a thin tracheal Pressure catheter inserted through the endotracheal tube Alveolar Pressure allows continuous bedside monitoring with ease and precision using the dynostatic algorithm. The method is unaffected by tube and connector geometry or by secretions.
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warning suctioning a lung model evaluation of closed suctioning systems
Acta Anaesthesiologica Scandinavica, 2001Co-Authors: Ola Stenqvist, Soren Sondergaard, Sigurbergur Kárason, S Lindgren, S LundinAbstract:Background: Closed system suctioning, CSS, has been advocated to avoid Alveolar collapse. However, ventilator manufacturers indicate that extreme negative Pressure levels can be obtained during closed system suctioning, impeding the performance of the ventilator. Methods: Suctioning with a 12 or 14 Fr catheter with a vacuum level of −50 kPa was either performed with an open technology or a CSS, where the catheter is introduced through a tight-fitting connection through the endotracheal tube, ETT. The lung model was ventilated with a Servo 900C or 300 ventilator with an I:E ratio of 1:2, 1:1 and 2:1 and extrinsic positive end-expiratory Pressure (PEEP) at 0 or 10 cm H2O. Respiratory volumes and Alveolar Pressure were measured at the lung model alveolus. Results: The initial suctioning flow was >40 l/min with a 14 Fr catheter. When inserting the catheter through a no. 7 ETT, PEEP rose from 11 to 23 cm H2O during volume control ventilation with an I:E ratio 1:1. During suctioning the Alveolar Pressure fell to 10 cm H2O below the set PEEP level. CSS during Pressure control ventilation had fewer effects. Low tidal volumes, inverse I:E ratio and secretions in the tube resulted in Pressures down to −92 cm H2O. Conclusion: CSS should not be used in volume control ventilation due to risk of high intrinsic PEEP levels at insertion of the catheter and extreme negative Pressures during suctioning. Pressure control ventilation produces less intrinsic PEEP effect. The continuous positive airway Pressure (CPAP) mode offers the least intrinsic PEEP during insertion of the catheter and least sub-atmospheric Pressure during suctioning.
Pierachille Santus - One of the best experts on this subject based on the ideXlab platform.
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diagnostic insights from plethysmographic Alveolar Pressure assessed during spontaneous breathing in copd patients
Diagnostics (Basel Switzerland), 2021Co-Authors: Camilla Zilianti, Pierachille Santus, Matteo Pecchiari, Edgardo Dangelo, Dejan RadovanovicAbstract:Since its introduction in the clinical practice, body plethysmography has assisted pneumologists in the diagnosis of respiratory diseases and patients' follow-up, by providing easy assessment of absolute lung volumes and airway resistance. In the last decade, emerging evidence suggested that estimation of Alveolar Pressure by electronically-compensated plethysmographs may contain information concerning the mechanics of the respiratory system which goes beyond those provided by the simple value of airway resistance or conductance. Indeed, the systematic study of expiratory Alveolar Pressure-flow loops produced during spontaneous breathing at rest has shown that the marked expansion of expiratory loops in chronic obstructive pulmonary disease patients mainly reflects the presence of tidal expiratory flow-limitation. The presence of this phenomenon can be accurately predicted on the basis of loop-derived parameters. Finally, we present results suggesting that plethysmographic Alveolar Pressure may be used to estimate non-invasively intrinsic positive end-expiratory Pressure (PEEPi) in spontaneously breathing patients, a task which previously could be only accomplished by introducing a balloon-tipped catheter in the esophagus.
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tidal expiratory flow limitation induces expiratory looping of the Alveolar Pressure flow relation in copd patients
Journal of Applied Physiology, 2020Co-Authors: Matteo Pecchiari, Camilla Zilianti, Edgardo Dangelo, Dejan Radovanovic, Laura Saderi, Giovanni Sotgiu, Pierachille SantusAbstract:During spontaneous breathing at rest, the Alveolar Pressure (Palv)-flow (V) relation exhibits a prominent expiratory loop in many chronic obstructive pulmonary disease (COPD) patients. Among the possible determinants of the loop, tidal expiratory flow limitation (tEFL) may be the main responsible. To compare the characteristics of the expiratory loop in COPD patients with flow limitation (FL) and without flow limitation (NFL), tEFL was assessed with the negative expiratory Pressure technique in stable mild to very severe COPD patients undergoing body plethysmography before and after bronchodilation (BD), an intervention that is able to reduce mechanical heterogeneity, recruitment/derecruitment, and gas trapping but rarely abolishes tEFL. The magnitude of the expiratory loop was indexed by the integral of Palv on V during expiration (Aexp). Before BD, Aexp was 360% greater in FL (n = 35) than in NFL (n = 25) patients (P < 0.001). After BD, Aexp was unchanged in NFL patients (ΔAexp 0%, P = 0.882) and slightly decreased in FL patients who remained FL (n = 32, ΔAexp -17%, P = 0.064). Three FL patients became NFL after BD, and their Aexp decreased markedly (ΔAexp -61%), reaching values similar to those observed in NFL patients at baseline. In conclusion, the greater Aexp measured in FL relative to NFL COPD patients, its relative invariance after BD when flow limitation persists, and its fall when flow limitation is abolished indicate that tEFL is a major determinant of the magnitude of the expiratory loop. Furthermore, Aexp can be used as a predictor of the presence of tEFL.NEW & NOTEWORTHY In stable chronic obstructive pulmonary disease (COPD) patients spontaneously breathing at rest, tidal expiratory flow limitation is the major determinant of the occurrence of expiratory looping in the plethysmographic flow-Alveolar Pressure diagram. In these patients the magnitude and the characteristics of the loop can be used as predictors of the presence of tidal expiratory flow limitation.
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detection of expiratory flow limitation in copd using the forced oscillation technique
European Respiratory Journal, 2004Co-Authors: Raffaele Dellaca, Andrea Aliverti, Pierachille Santus, N Stevenson, Stefano Centanni, Peter T Macklem, A Pedotti, P M A CalverleyAbstract:Expiratory flow limitation (EFL) during tidal breathing is a major determinant of dynamic hyperinflation and exercise limitation in chronic obstructive pulmonary disease (COPD). Current methods of detecting this are either invasive or unsuited to following changes breath-by-breath. It was hypothesised that tidal flow limitation would substantially reduce the total respiratory system reactance (Xrs) during expiration, and that this reduction could be used to reliably detect if EFL was present. To test this, 5-Hz forced oscillations were applied at the mouth in seven healthy subjects and 15 COPD patients (mean +/- sD forced expiratory volume in one second was 36.8 +/- 11.5% predicted) during quiet breathing. COPD breaths were analysed (n=206) and classified as flow-limited if flow decreased as Alveolar Pressure increased, indeterminate if flow decreased at constant Alveolar Pressure, or nonflow-limited. Of these, 85 breaths were flow-limited, 80 were not and 41 were indeterminate. Among other indices, mean inspiratory minus mean expiratory Xrs (deltaXrs) and minimum expiratory Xrs (Xexp,min) identified flow-limited breaths with 100% specificity and sensitivity using a threshold between 2.53-3.12 cmH2O x s x L(-1) (deltaXrs) and -7.38- -6.76 cmH2O x s x L(-1) (Xexp,min) representing 6.0% and 3.9% of the total range of values respectively. No flow-limited breaths were seen in the normal subjects by either method. Within-breath respiratory system reactance provides an accurate, reliable and noninvasive technique to detect expiratory flow limitation in patients with chronic obstructive pulmonary disease.
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detection of expiratory flow limitation in copd using the forced oscillation technique
European Respiratory Journal, 2004Co-Authors: Raffaele Dellaca, Andrea Aliverti, Pierachille Santus, N Stevenson, Stefano Centanni, Peter T Macklem, A Pedotti, P M A CalverleyAbstract:Expiratory flow limitation (EFL) during tidal breathing is a major determinant of dynamic hyperinflation and exercise limitation in chronic obstructive pulmonary disease (COPD). Current methods of detecting this are either invasive or unsuited to following changes breath-by-breath. It was hypothesised that tidal flow limitation would substantially reduce the total respiratory system reactance (X rs ) during expiration, and that this reduction could be used to reliably detect if EFL was present. To test this, 5‐Hz forced oscillations were applied at the mouth in seven healthy subjects and 15 COPD patients (mean±sd forced expiratory volume in one second was 36.8±11.5 % predicted) during quiet breathing. COPD breaths were analysed (n=206) and classified as flow-limited if flow decreased as Alveolar Pressure increased, indeterminate if flow decreased at constant Alveolar Pressure, or nonflow-limited. Of these, 85 breaths were flow-limited, 80 were not and 41 were indeterminate. Among other indices, mean inspiratory minus mean expiratory X rs (Δ X rs ) and minimum expiratory X rs (X exp,min ) identified flow-limited breaths with 100% specificity and sensitivity using a threshold between 2.53–3.12 cmH 2 O·s·L −1 (Δ X rs ) and −7.38– −6.76 cmH 2 O·s·L −1 (X exp,min ) representing 6.0% and 3.9% of the total range of values respectively. No flow-limited breaths were seen in the normal subjects by either method. Within-breath respiratory system reactance provides an accurate, reliable and noninvasive technique to detect expiratory flow limitation in patients with chronic obstructive pulmonary disease.
Mara S Ludwig - One of the best experts on this subject based on the ideXlab platform.
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extracellular matrix and oscillatory mechanics of rat lung parenchyma in bleomycin induced fibrosis
American Journal of Respiratory and Critical Care Medicine, 1999Co-Authors: Marisa Dolhnikoff, Thais Mauad, Mara S LudwigAbstract:We investigated in vivo and in vitro oscillatory mechanics in bleomycin-induced fibrotic lungs and correlated these with morphometric changes in the collagen-elastin matrix and contractile cells. Fischer rats received bleomycin sulfate (BLEO,1.5 U) or saline intratracheally. Four weeks later tracheal flow and tracheal and Alveolar Pressure (using Alveolar capsules) were measured in open-chested rats during mechanical ventilation (V T = 8 ml/kg, f = 1 Hz, PEEP = 4 cm H(2)O). Total lung, tissue, and airway resistance (R) and lung elastance (E) were calculated. In addition, excised parenchymal strips (10 x 2 x 2 mm) were studied in the organ bath. Strips were attached to a force transducer at one end and to a servo-controlled lever arm that effected length (L) changes at the other. Sinusoidal oscillations were applied (f = 1 Hz, amplitude = 2. 5% resting L and tension = 0.7 g) and R, E, and hysteresivity (eta) were calculated. Strips were then exposed to acetylcholine (ACh, 10(-)(3) M). The amount of collagen and elastic fibers in the parenchymal strip was assessed semiquantitatively by point-counting in 5-micrometer-thick sections stained with either Sirius Red or Weigert's Resorcin-fuchsin. alpha-Smooth-muscle-specific actin was detected immunohistochemically. Both in vivo and in vitro, R, E, and eta were significantly increased in BLEO rats (p < 0.05). The % increase in R, E and eta after Ach was greater in BLEO rats (p < 0. 01). There was also a significant increase in the volume proportion of collagen, elastic fibers, and actin in the parenchyma (p < 0.01). In BLEO rats, baseline R and E were correlated with the volume proportion of collagen in the parenchyma. We conclude that changes in the collagen-elastin matrix contribute to changes in the viscoelastic properties of bleomycin-treated rat lungs. Dolhnikoff M, Mauad T, Ludwig MS. Extracellular matrix and oscillatory mechanics of rat lung parenchyma in bleomycin-induced fibrosis.
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extracellular matrix and oscillatory mechanics of rat lung parenchyma in bleomycin induced fibrosis
American Journal of Respiratory and Critical Care Medicine, 1999Co-Authors: Marisa Dolhnikoff, Thais Mauad, Mara S LudwigAbstract:We investigated in vivo and in vitro oscillatory mechanics in bleomycin-induced fibrotic lungs and correlated these with morphometric changes in the collagen-elastin matrix and contractile cells. Fischer rats received bleomycin sulfate (BLEO,1.5 U) or saline intratracheally. Four weeks later tracheal flow and tracheal and Alveolar Pressure (using Alveolar capsules) were measured in open-chested rats during mechanical ventilation (V˙ t = 8 ml/kg, f = 1 Hz, PEEP = 4 cm H2O). Total lung, tissue, and airway resistance (R) and lung elastance (E) were calculated. In addition, excised parenchymal strips (10 × 2 × 2 mm) were studied in the organ bath. Strips were attached to a force transducer at one end and to a servo-controlled lever arm that effected length (L) changes at the other. Sinusoidal oscillations were applied (f = 1 Hz, amplitude = 2.5% resting L and tension = 0.7 g) and R, E, and hysteresivity ( η ) were calculated. Strips were then exposed to acetylcholine (ACh, 10− 3 M). The amount of collagen and...
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airway and tissue responses during hyperpnea induced constriction in guinea pigs
American Journal of Respiratory and Critical Care Medicine, 1994Co-Authors: T Nagase, M J Dallaire, Mara S LudwigAbstract:It has been reported that hyperpnea-induced bronchoconstriction in guinea pigs is a potential model for exercise-induced asthma in humans. On the basis of recent studies that show increases in tissue resistance after allergen exposure in sensitized rats, we hypothesized that lung tissues might also be involved in the pathophysiology in this asthma model. We measured tracheal Pressure (Ptr) and Alveolar Pressure (PA) using Alveolar capsules in open-chested, mechanically ventilated (respiratory frequency [f] = 1 Hz, tidal volume [VT] = 9 ml/kg, positive end-expiratory Pressure [PEEP] = 4 cm H2O) guinea pigs under control conditions (regular breathing of warm, humidified air) and after dry gas hyperpnea challenge (HC, mixture of 95% O2 and 5% CO2, 150 breaths/min, 7 min). We calculated lung elastance (EL) and resistance of lung (RL), tissue (Rti), and airway (Raw) by fitting the equation of motion to changes in Ptr and PA. To assess the effects of volume history, we applied a single deep inflation (three tim...
P M A Calverley - One of the best experts on this subject based on the ideXlab platform.
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detection of expiratory flow limitation in copd using the forced oscillation technique
European Respiratory Journal, 2004Co-Authors: Raffaele Dellaca, Andrea Aliverti, Pierachille Santus, N Stevenson, Stefano Centanni, Peter T Macklem, A Pedotti, P M A CalverleyAbstract:Expiratory flow limitation (EFL) during tidal breathing is a major determinant of dynamic hyperinflation and exercise limitation in chronic obstructive pulmonary disease (COPD). Current methods of detecting this are either invasive or unsuited to following changes breath-by-breath. It was hypothesised that tidal flow limitation would substantially reduce the total respiratory system reactance (Xrs) during expiration, and that this reduction could be used to reliably detect if EFL was present. To test this, 5-Hz forced oscillations were applied at the mouth in seven healthy subjects and 15 COPD patients (mean +/- sD forced expiratory volume in one second was 36.8 +/- 11.5% predicted) during quiet breathing. COPD breaths were analysed (n=206) and classified as flow-limited if flow decreased as Alveolar Pressure increased, indeterminate if flow decreased at constant Alveolar Pressure, or nonflow-limited. Of these, 85 breaths were flow-limited, 80 were not and 41 were indeterminate. Among other indices, mean inspiratory minus mean expiratory Xrs (deltaXrs) and minimum expiratory Xrs (Xexp,min) identified flow-limited breaths with 100% specificity and sensitivity using a threshold between 2.53-3.12 cmH2O x s x L(-1) (deltaXrs) and -7.38- -6.76 cmH2O x s x L(-1) (Xexp,min) representing 6.0% and 3.9% of the total range of values respectively. No flow-limited breaths were seen in the normal subjects by either method. Within-breath respiratory system reactance provides an accurate, reliable and noninvasive technique to detect expiratory flow limitation in patients with chronic obstructive pulmonary disease.
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detection of expiratory flow limitation in copd using the forced oscillation technique
European Respiratory Journal, 2004Co-Authors: Raffaele Dellaca, Andrea Aliverti, Pierachille Santus, N Stevenson, Stefano Centanni, Peter T Macklem, A Pedotti, P M A CalverleyAbstract:Expiratory flow limitation (EFL) during tidal breathing is a major determinant of dynamic hyperinflation and exercise limitation in chronic obstructive pulmonary disease (COPD). Current methods of detecting this are either invasive or unsuited to following changes breath-by-breath. It was hypothesised that tidal flow limitation would substantially reduce the total respiratory system reactance (X rs ) during expiration, and that this reduction could be used to reliably detect if EFL was present. To test this, 5‐Hz forced oscillations were applied at the mouth in seven healthy subjects and 15 COPD patients (mean±sd forced expiratory volume in one second was 36.8±11.5 % predicted) during quiet breathing. COPD breaths were analysed (n=206) and classified as flow-limited if flow decreased as Alveolar Pressure increased, indeterminate if flow decreased at constant Alveolar Pressure, or nonflow-limited. Of these, 85 breaths were flow-limited, 80 were not and 41 were indeterminate. Among other indices, mean inspiratory minus mean expiratory X rs (Δ X rs ) and minimum expiratory X rs (X exp,min ) identified flow-limited breaths with 100% specificity and sensitivity using a threshold between 2.53–3.12 cmH 2 O·s·L −1 (Δ X rs ) and −7.38– −6.76 cmH 2 O·s·L −1 (X exp,min ) representing 6.0% and 3.9% of the total range of values respectively. No flow-limited breaths were seen in the normal subjects by either method. Within-breath respiratory system reactance provides an accurate, reliable and noninvasive technique to detect expiratory flow limitation in patients with chronic obstructive pulmonary disease.
Clive A Ramsden - One of the best experts on this subject based on the ideXlab platform.
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effect of i e ratio on mean Alveolar Pressure during high frequency oscillatory ventilation
Journal of Applied Physiology, 1999Co-Authors: Jane J Pillow, Heather L Neil, Malcolm Howard Wilkinson, Clive A RamsdenAbstract:This study investigated factors contributing to differences between mean Alveolar Pressure ( P A ¯ ) and mean Pressure at the airway opening (Pao) during high-frequency oscillatory ventilation (HFO...