Chest
Volume 128, Issue 4, October 2005, Pages 2991-2998
Journal home page for Chest

Laboratory and Animal Investigations
Effects of Spontaneous Breathing During Airway Pressure Release Ventilation on Respiratory Work and Muscle Blood Flow in Experimental Lung Injury

https://doi.org/10.1378/chest.128.4.2991Get rights and content

Study objectives

To evaluate the effects of spontaneous breathing at ambient airway pressure (Paw) and during airway pressure release ventilation (APRV) on respiratory work and respiratory muscle blood flow (RMBF) in experimental lung injury.

Design

Prospective experimental study.

Setting

Research laboratory of a university hospital.

Subjects

Twelve hemodynamically stable, analgosedated, and tracheotomized domestic pigs.

Measurements

Respiratory work was estimated by the inspiratory pressure time product (PTPinsp) of esophageal pressure, and RMBF was measured with colored microspheres. Lung injury was induced with IV boli of oleic acid. The first set of measurements was performed before induction of lung injury while pigs were breathing spontaneously at ambient Paw, the second after induction of lung injury while breathing spontaneously at ambient Paw, and the third with lung injury and spontaneous breathing with APRV.

Results

After induction of lung injury PTPinsp increased from 138 ± 14 to 214 ± 32 cm H2 O s/min when pigs breathed spontaneously at ambient Paw (p < 0.05) and returned to 128 ± 27 cm H2 O s/min during APRV. While systemic hemodynamics and blood flow to the psoatic and intercostal muscles did not change, diaphragmatic blood flow increased from 0.34 ± 0.05 before to 0.54 ± 0.08 mL/g/min after induction of lung injury and spontaneous breathing at ambient Paw (p < 0.05) and returned to 0.32 ± 0.05 mL/g/min during APRV (p < 0.05 vs spontaneous breathing at ambient Paw [lung injury]).

Conclusion

Respiratory work and RMBF are increased in acute lung injury when subjects breathe spontaneously at ambient Paw. Supporting spontaneous breathing with APRV decreases respiratory work and RMBF to physiologic values.

Section snippets

Instrumentation

The principles of laboratory animal care (revised National Institutes of Health guidelines, 1985) were followed, and the study was approved by the local Laboratory Animal Care and Use Committee. Twelve pigs, mixed German country breed, weighing 10 to 19 kg (15.2 ± 0.8 kg [mean ± SEM]) were fasted for 24 h while having free access to water. Prior to instrumentation, animals were premedicated with IM ketamine (10 mg/kg), xylazine hydrochloride (2 mg/kg), and glyopyrronium bromide (15 μg/kg) and

Results

For validation of the microspheres technique, adequate mixing of injected microspheres and even distribution of blood flow to the various organs were indicated by highly significant correlations between the number of microspheres trapped in the two reference blood samples (5,030 ± 619 microspheres per sample vs 4,848 ± 556 microspheres per sample, r = 0.95) and the blood flows to the right and left adrenal glands (1.99 ± 0.22 mL/g/min vs 1.91 ± 0.25 mL/g/min, r = 0.94) [p < 0.0001,

Discussion

The aim of our study was to investigate the effects of spontaneous breathing on respiratory work and RMBF in a pig model with oleic acid-induced lung injury. We found that PTPinsp and diaphragmatic blood flow markedly increased when animals with lung injury were breathing spontaneously at ambient Paw, and that ventilatory support with APRV resulted in a reduction of PTPinsp and diaphragmatic blood flow to normal physiologic values not different from those obtained in animals with normal lungs

References (27)

  • GodjeO et al.

    Reproducibility of double indicator dilution measurements of intrathoracic blood volume compartments, extravascular lung water, and liver function

    Chest

    (1998)
  • PutensenC et al.

    Effect of interfacing between spontaneous breathing and mechanical cycles on the ventilation-perfusion distribution in canine lung injury

    Anesthesiology

    (1994)
  • PutensenC et al.

    Spontaneous breathing during ventilatory support improves ventilation-perfusion distributions in patients with acute respiratory distress syndrome

    Am J Respir Crit Care Med

    (1999)
  • FroeseAB et al.

    Effects of anesthesia and paralysis on diaphragmatic mechanics in man

    Anesthesiology

    (1974)
  • WriggeH et al.

    Spontaneous breathing improves lung aeration in oleic acid-induced lung injury

    Anesthesiology

    (2003)
  • HormannC et al.

    Biphasic positive airway pressure (BIPAP): a new mode of ventilatory support

    Eur J Anaesthesiol

    (1994)
  • SydowM et al.

    Long-term effects of two different ventilatory modes on oxygenation in acute lung injury: comparison of airway pressure release ventilation and volume-controlled inverse ratio ventilation

    Am J Respir Crit Care Med

    (1994)
  • PutensenC et al.

    Long-term effects of spontaneous breathing during ventilatory support in patients with acute lung injury

    Am J Respir Crit Care Med

    (2001)
  • MagderS et al.

    Respiratory muscle blood flow in oleic acid-induced pulmonary edema

    J Appl Physiol

    (1986)
  • HussainSN et al.

    Distribution of respiratory muscle and organ blood flow during endotoxic shock in dogs

    J Appl Physiol

    (1985)
  • ViiresN et al.

    Regional blood flow distribution in dog during induced hypotension and low cardiac output: spontaneous breathing versus artificial ventilation

    J Clin Invest

    (1983)
  • KowallikP et al.

    Measurement of regional myocardial blood flow with multiple colored microspheres

    Circulation

    (1991)
  • BrunnerJX et al.
    (1988)
  • Cited by (31)

    • Does airway pressure release ventilation offer new hope for treating acute respiratory distress syndrome?

      2022, Journal of Intensive Medicine
      Citation Excerpt :

      There are three common methods for ARDS model establishment: (1) oleic acid injection, (2) saline lung lavage, and (3) ischemia-reperfusion and peritoneal sepsis. Most studies indicated that SB during APRV can improve oxygenation, decreases respiratory work, and redistribute ventilation to the dependent lung area, thereby reducing VILI.[52–58] Most studies compared CV modes and APRV in the animal ALI model and found that APRV had lower lung injury histological scores and could reduce cytokine mRNA expressions in lung tissue and reduce tumor necrosis factor (TNF)-a, interleukin (IL)−8, and IL-6 in the bronchoalveolar lavage fluid (BALF).[56,58–60]

    • Airway pressure release ventilation

      2020, BJA Education
      Citation Excerpt :

      There have been multiple experiments predominantly using porcine or rodent animal models to investigate whether APRV confers any advantage or harm compared with conventional ventilation. In animal models, APRV improves arterial oxygenation, increases ventilation in dependent areas of lung, reduces inflammatory cytokine production, and can prevent the development of ARDS.11–15 One of the most striking animal experiments was in pigs with induced sepsis, randomised to receive APRV or ‘ARDSnet protocol’ low tidal volume (LTV) ventilation.15

    • Spontaneous breathing improves shunt fraction and oxygenation in comparison with controlled ventilation at a similar amount of lung collapse

      2011, Anesthesia and Analgesia
      Citation Excerpt :

      The present study to our knowledge is the first to compare nonassisted SB with MV set to the same small tidal volumes and low pressures as during SB. The explanation for the improvement in gas exchange with SB efforts has been reduction in atelectatic lung areas close to the diaphragm, supporting the concept of reopening of dependent lung regions by diaphragmatic contractions.1–5,17–22 This is a possible mechanism in APRV or BiPAP in which tidal volumes are not necessarily as small as the “biological” Vt of SB adopted in this study.

    View all citing articles on Scopus

    Supported by departmental funding.

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/misc/reprints.shtml).

    View full text