• 1.

    Dugdale AH, Taylor PM. Equine anaesthesia-associated mortality: where are we now? Vet Anaesth Analg. 2016;43(3):242255.

  • 2.

    Costa-Farré C, Prades M, Ribera T, Valero O, Taurà P. Does intraoperative low arterial partial pressure of oxygen increase the risk of surgical site infection following emergency exploratory laparotomy in horses? Vet J. 2014;200(1):175180.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3.

    Johnston GM, Eastment JK, Wood JLN, Taylor PM. The confidential enquiry into perioperative equine fatalities (CEPEF): mortality results of phases 1 and 2. Vet Anaesth Analg. 2002;29(4):159170.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4.

    Nyman G, Funkquist B, Kvart C, et al. Atelectasis causes gas exchange impairment in the anaesthetised horse. Equine Vet J. 1990;22(5):317324.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5.

    Sorenson PR, Robinson NE. Postural effects of lung volumes and asynchronous ventilation in anaesthetized horses. J Appl Physiol Respir Environ Exerc Physiol. 1980;48(1):97103.

    • Search Google Scholar
    • Export Citation
  • 6.

    Hedenstierna G, Nyman G, Frostell C. Animal models of lung physiology during anaesthesia. In: Hau J, Van Hoosier GL, eds. Handbook of Laboratory Animal Science. 2nd ed. CRC Press; 2005:263288.

    • Search Google Scholar
    • Export Citation
  • 7.

    Stack A, Derksen FJ, Williams KJ, Robinson NE, Jackson WF. Lung region and racing affect mechanical properties of equine pulmonary microvasculature. J Appl Physiol. 2014;117(4):370376.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 8.

    Nyman G, Hedenstierna G. Ventilation-perfusion relationships in the anaesthetised horse. Equine Vet J. 1989;21(4):274281.

  • 9.

    Hopster K, Käestner SBR, Rohn K, Ohnesorge B. Intermittent positive pressure ventilation with constant positive end-expiratory pressure and alveolar recruitment manoeuvre during inhalation anaesthesia in colic horses and the influence on the early recovery period. Vet Anaesth Analg. 2011;38(3):169177.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 10.

    Hopster K, Wogatzki A, Geburek F, Conze P, Käestner SBR. Effects of positive end-expiratory pressure titration on intestinal oxygenation and perfusion in isoflurane anaesthetized horses. Equine Vet J. 2017;49(2):250256.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 11.

    Hopster K, Rohn K, Ohnesorge B, Käestner SBR. Controlled mechanical ventilation with constant positive end-expiratory pressure and alveolar recruitment manoeuvres during anaesthesia in laterally or dorsally recumbent horses. Vet Anaesth Analg. 2017;44(1):121126.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 12.

    Wettstein D, Moens Y, Jaeggin-Schmucker N, et al. Effects of an alveolar recruitment maneuver on cardiovascular and respiratory parameters during total intravenous anesthesia in ponies. Am J Vet Res. 2006;67(1):152159.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 13.

    Lessard MR, Guérot E, Lorino H, Lemaire F, Brochard L. Effects of pressure-controlled with different I:E ratios versus volume-controlled ventilation on respiratory mechanics, gas exchange, and hemodynamics in patients with adult respiratory distress syndrome. Anesthesiology. 1994;80(5):983991.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 14.

    Campbell RS, Davis BR. Pressure-controlled versus volume-controlled ventilation: does it matter? Respir Care. 2002;47(4):416424.

  • 15.

    Maeda Y, Fujino Y, Uchiyama A, Matsuura N, Mashimo T, Nishimura M. Effects of peak inspiratory flow on development of ventilator-induced lung injury in rabbits. Anesthesiology. 2004;101(3):722728.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 16.

    Grasso S, Fanelli V, Cafarelli A, et al. Effects of high versus low positive end-expiratory pressures in acute respiratory distress syndrome. Am J Respir Crit Care Med. 2005;171(9):10021008.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 17.

    Tremblay LN, Slutsky AS. Ventilator-induced lung injury: from the bench to the bedside. Intensive Care Med. 2006;32(1):2433.

  • 18.

    Pinhu L, Whitehead T, Evans T, Griffiths M. Ventilator-associated lung injury. Lancet. 2003;361(9354):332340.

  • 19.

    Wirth S, Springer S, Spaeth J, Borgmann S, Goebel U, Schumann S. Application of the novel ventilation mode FLow-controlled EXpiration (FLEX): a crossover proof-of-principle study in lung-healthy patients. Anesth Analg. 2017;125(4):12461252.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 20.

    Goebel U, Haberstroh J, Foerster K, et al. Flow-controlled expiration: a novel ventilation mode to attenuate experimental porcine lung injury. Br J Anaesth. 2014;113(3):474483.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 21.

    Schumann S, Goebel U, Haberstroh J, et al. Determination of respiratory system mechanics during inspiration and expiration by FLow-controlled EXpiration (FLEX): a pilot study in anesthetized pigs. Minerva Anestesiol. 2014;80(1):1928.

    • Search Google Scholar
    • Export Citation
  • 22.

    Lachmann B. Open the lung and keep the lung open. Intensive Care Med. 1992;18(6):319321.

  • 23.

    Schmidt J, Wenzel C, Mahn M, et al. Improved lung recruitment and oxygenation during mandatory ventilation with a new expiratory ventilation assistance device. Eur J Anaesthesiol. 2018;35(10):736744.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 24.

    Ambrisko TD, Schramel J, Hopster K, Kaestner S, Moens Y. Assessment of distribution of ventilation and regional lung compliance by electrical impedance tomography in anaesthetized horses undergoing alveolar recruitment manoeuvres. Vet Anaesth Analg. 2017;44(2):264272.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 25.

    Smith BJ, Grant KA, Bates JH. Linking the development of ventilator-induced injury to mechanical function in the lung. Ann Biomed Eng. 2013;41(3):527536.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 26.

    Marshall R. The physical properties of the lungs in relation to the subdivisions of lung volume. Clin Sci. 1957;16(3):507515.

  • 27.

    Duggan M, Kavanagh BP. Pulmonary atelectasis: a pathogenic perioperative entity. Anesthesiology. 2005;102(4):838854.

  • 28.

    Cournand A, Motley HL. Physiological studies of the effects of intermittent positive pressure breathing on cardiac output in man. Am J Physiol. 1948;152(1):162174.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 29.

    Lenfant C, Howell BJ. Cardiovascular adjustments in dogs during continuous pressure breathing. J Appl Physiol. 1960;15:425428.

  • 30.

    Wilson DV, Soma LR. Cardiopulmonary effects of positive end-expiratory pressure in anesthetized, mechanically ventilated ponies. Am J Vet Res. 1990;51(5):734739.

    • Search Google Scholar
    • Export Citation

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Flow-controlled expiration improves respiratory mechanics, ventilation, and gas exchange in anesthetized horses

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  • 1 University of Pennsylvania, School of Veterinary Medicine, New Bolton Center Campus, Kennett Square, PA

Abstract

OBJECTIVE

Mechanical ventilation is usually achieved by active lung inflation during inspiration and passive lung emptying during expiration. By contrast, flow-controlled expiration (FLEX) ventilation actively reduces the rate of lung emptying by causing linear gas flow throughout the expiratory phase. Our aim was to evaluate the effects of FLEX on lung compliance and gas exchange in anesthetized horses in dorsal recumbency.

ANIMALS

8 healthy horses.

PROCEDURES

All animals were anesthetized twice and either ventilated beginning with FLEX or conventional volume-controlled ventilation in a randomized, crossover design. Total anesthesia time was 3 hours, with the ventilatory mode being changed after 1.5 hours. During anesthesia, cardiac output (thermodilution), mean arterial blood pressures, central venous pressure, and pulmonary arterial pressure were recorded. Further, peak, plateau, and mean airway pressures and dynamic lung compliance (Cdyn) were measured. Arterial blood gases were analyzed every 15 minutes. Data were analyzed using ANOVA (P < 0.05).

RESULTS

FLEX ventilation resulted in significantly higher arterial oxygen partial pressures (521 vs 227 mm Hg) and Cdyn (564 vs 431 mL/cm H2O) values compared to volume-controlled ventilation. The peak and plateau airway pressure were lower, but mean airway pressure was significantly higher (4.8 vs 9.2 cm H2O) in FLEX ventilated horses. No difference for cardiovascular parameters were detected.

CLINICAL RELEVANCE

The results of this study showed a significant improvement of the Pao2 and Cdyn without compromising the cardiovascular system when horses were ventilated by use of FLEX compared to conventional ventilation.

Abstract

OBJECTIVE

Mechanical ventilation is usually achieved by active lung inflation during inspiration and passive lung emptying during expiration. By contrast, flow-controlled expiration (FLEX) ventilation actively reduces the rate of lung emptying by causing linear gas flow throughout the expiratory phase. Our aim was to evaluate the effects of FLEX on lung compliance and gas exchange in anesthetized horses in dorsal recumbency.

ANIMALS

8 healthy horses.

PROCEDURES

All animals were anesthetized twice and either ventilated beginning with FLEX or conventional volume-controlled ventilation in a randomized, crossover design. Total anesthesia time was 3 hours, with the ventilatory mode being changed after 1.5 hours. During anesthesia, cardiac output (thermodilution), mean arterial blood pressures, central venous pressure, and pulmonary arterial pressure were recorded. Further, peak, plateau, and mean airway pressures and dynamic lung compliance (Cdyn) were measured. Arterial blood gases were analyzed every 15 minutes. Data were analyzed using ANOVA (P < 0.05).

RESULTS

FLEX ventilation resulted in significantly higher arterial oxygen partial pressures (521 vs 227 mm Hg) and Cdyn (564 vs 431 mL/cm H2O) values compared to volume-controlled ventilation. The peak and plateau airway pressure were lower, but mean airway pressure was significantly higher (4.8 vs 9.2 cm H2O) in FLEX ventilated horses. No difference for cardiovascular parameters were detected.

CLINICAL RELEVANCE

The results of this study showed a significant improvement of the Pao2 and Cdyn without compromising the cardiovascular system when horses were ventilated by use of FLEX compared to conventional ventilation.

Supplementary Materials

    • Supplementary Figure S1 (PDF 107 KB)

Contributor Notes

Corresponding author: Dr. Hopster (khopster@vet.upenn.edu)