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The dynostatic algorithm accurately calculates alveolar pressure on-line during ventilator treatment in children (2003)

Sondergaard, Soren ; Kárason, Sigurbergur ; Hanson, Angela ; [et al.]

Oxford, UK : Blackwell Science Ltd

Pediatric anesthesia 13 (2003), S. 0

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ISSN: 1460-9592

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Medicine

Notes: 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.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1460-9592.2003.01064.x

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Evaluation of a Pitot Type Spirometer in Helium/Oxygen Mixtures (1998)

Søndergaard, Søren ; Kárason, Sigurbergur ; Lundin, Stefan ; [et al.]

Springer

Journal of clinical monitoring and computing 14 (1998), S. 425-431

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ISSN: 1573-2614

Keywords: Gas density ; helium ; oxygen ; venturimeter ; measurement ; tidal volume

Source: Springer Online Journal Archives 1860-2000

Topics: Computer Science , Medicine

Notes: Abstract Objective. Mixtures of helium and oxygen are regaining a place in the treatment of obstruction of the upper and lower respiratory tract. The parenchymal changes during the course of IRDS or ARDS may also benefit from the reintroduction of helium/oxygen. In order to monitor and document the effect of low-density gas mixtures, we evaluated the Datex AS/3 Side Stream Spirometry module with D-lite® (Datex-Engstrom Instrumentarium Corporation, Finland) against two golden standards. Methods. Under conditions simulating controlled and spontaneous ventilation with gas mixtures of He (approx. 80, 50, and 20%)/O2 or N2 (approx. 21 and 79%)/O2, simultaneous measurements using Biotek Ventilator Tester (Bio-Tek Instr., Vermont, USA) or body plethysmograph (SensorMedics System, Anaheim, USA) were correlated with data from the spirometry module. Data were analyzed according to a statistical regression model resulting in a best-fit equation based on density, voltage, and volume measurements. Results. As expected, the D-lite (a modified Pitot tube) showed density-dependent behaviour. Regression equations and percentage deviation of estimated versus measured values were calculated. Conclusion. Measurements with the D-lite using low-density gases are satisfactorily contained in best-fit equations with a standard deviation of less than 5% during all ventilatory modes and mixtures.