Abstract
The inspiratory work exerted by an electromechanical lung model in drawing a 500ml breath, was assessed by planimetry of pressure/volume loops for six commercial demand valve CPAP devices (Servo B and C from Siemens, EV-A and UV-2 from Dräger, the Puritan Bennett 7200 and the Engström ERICA) and compared to the loading of a conventional high flow CPAP system. The effect of trigger sensitivity and inspiratory pressure support on inspiratory work was also investigated in some cases. The lung model allowed for calibrated changes in compliance and airway resistance. In the non-assisted CPAP mode, all machines required slightly larger amounts of inspiratory work than the continuous flow CPAP system. Most machines were comparable in performance but the ERICA and the Servo B required up to 22% more work than the continuous flow CPAP system and represented the maximal increase of total work due to any given machine. The greater part of total inspiratory work was due to lung compliance and airway resistance, factors external to the machines. Halving complicance doubled the work and exchanging a 7 for a 9 mm i.d. endotracheal tube in the circuit increased work by about 3% regardless of machine. Decreasing trigger sensitivity from 0 to 2 cm H2O for the Servo B increased work by up to 24%. Using 5 cm H2O of inspiratory pressure support decreased work for all machines up to 36% maximally. In conclusion, under the chosen experimental conditions the inspiratory work of breathing was only minimally increased with the following demand valve systems in comparison to a continuous flow CPAP system: Servo C, EV-A, UV-2, and Bennett 7200. The remaining required additional work could be eliminated by using inspiratory pressure support. However, triggering effort remains the unavoidable additional load of demand valve CPAP systems.
Article PDF
Similar content being viewed by others
References
Gherini S, Peters MM, Virgilio RW (1979) Mechanical work on the lungs and work of a breathing with positive end-expiratory pressure and continuous positive airway pressure. Chest 76:251
Schlobohm RM, Falltrick RT, Quan SP, Katz JA (1981) Lung volumes, mechanics and oxygenation during spontaneous positive pressure ventilation: the advantage of CPAP over EPAP. Anesthesiology 55:416
Katz JA, Marks JD (1985) Inspiratory work with and without continuous positive airway pressure in patients with acute respiratory failure. Anesthesiology 63:598
Gibney RTN, Wilson RS, Pontoppidan H (1982) Comparison of the work of breathing on high gas flow and demand valve continuous positive airway pressure systems. Chest 82:692
Thies WR, Härter P, Falke KJ (1983) Increased work of breathing with demand flow CPAP systems (abstract). 2nd European Congress on Intensive Care, Geneva
Viale JP, Annat G, Bertrand O, Godart J, Motin J (1985) Additional inspiratory work in intubated patients breathing with continuous positive airway pressure systems. Anesthesiology 63:536
Hillman DR, Finucane KE (1985) Continuous positive airway pressure: breathing system to minimize respiratory work. Crit Care Med 13:38
Katz JA, Kraemer RW, Gjerde GE (1985) Inspiratory work and airway pressure with continuous positive airway pressure delivery systems. Chest 88:519
Bolder PM, Healy TEJ, Bolder AR, Beatty PCW, Kay B (1986) The extra work of breathing through adult endotracheal tubes. Anesth Analg 65:853
Bshouty ZH, Roeseler J, Reynaert MS, Rodenstein D (1986) The importance of the balloon reservoir volume of a CPAP system in reducing the work of breathing. Intensive Care Med 12:153
Mecklenburgh JS, Latto IP, Al-Obaidi AA, Swai EA, Mapleson WW (1986) Excessive work of breathing during intermittent mandatory ventilation. Br J Anesth 58:1048
Brandl M, Lang M, Obermayer A (1986) Vergleichende Untersuchungen von CPAP Systemen an einem Atmungssimulator. Anaesthesist 35:73
Hillman K, Friedlos J, Davey A (1986) A comparison of intermittent mandatory ventilation systems. Crit Care Med 14:499
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Samodelov, L.F., Falke, K.J. Total inspiratory work with modern demand valve devices compared to continuous flow CPAP. Intensive Care Med 14, 632–639 (1988). https://doi.org/10.1007/BF00256768
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00256768