Pulmonary mechanics during rapid mechanical ventilation in rabbits with saline-lavaged lungs

J. J. Perez Fontan, B. S. Turner, G. P. Heldt, G. A. Gregory

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Infants with respiratory failure are frequently mechanically ventilated at rates exceeding 60 breaths/min. We analyzed the effect of ventilatory rates of 30, 60, and 90 breaths/min (inspiratory times of 0.6, 0.3, and 0.2 s, respectively) on the pressure-flow relationships of the lungs of anesthetized paralyzed rabbits after saline lavage. Tidal volume and functional residual capacity were maintained constant. We computed effective inspiratory and expiratory resistance and compliance of the lungs by dividing changes in transpulmonary pressure into resistive and elastic components with a multiple linear regression. We found that mean pulmonary resistance was lower at higher ventilatory rates, while pulmonary compliance was independent of ventilatory rate. The transpulmonary pressure developed by the ventilator during inspiration approximated a linear ramp. Gas flow became constant and the pressure-volume relationship linear during the last portion of inspiration. Even at a ventilatory rate of 90 breaths/min, 28-56% of the tidal volume was delivered with a constant inspiratory flow. Our findings are consistent with the model of Bates et al. (J. Appl. Physiol, 58: 1840-1848, 1985), wherein the distribution of gas flow within the lungs depends predominantly on resistive factors while inspiratory flow is increasing, and on elastic factors while inspiratory flow is constant. This dynamic behavior of the surfactant-depleted lungs suggests that, even with very short inspiratory times, distribution of gas flow within the lungs is in large part determined by elastic factors. Unless the inspiratory time is further shortened, gas flow may be directed to areas of increased resistance, resulting in hyperinflation and barotrauma.

Original languageEnglish (US)
Pages (from-to)1431-1437
Number of pages7
JournalJournal of Applied Physiology
Volume61
Issue number4
StatePublished - 1986

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Mechanics
Artificial Respiration
Rabbits
Lung
Gases
Lung Compliance
Pressure
Tidal Volume
Barotrauma
Functional Residual Capacity
Architectural Accessibility
Therapeutic Irrigation
Mechanical Ventilators
Surface-Active Agents
Respiratory Insufficiency
Linear Models

ASJC Scopus subject areas

  • Endocrinology
  • Physiology
  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

Cite this

Pulmonary mechanics during rapid mechanical ventilation in rabbits with saline-lavaged lungs. / Perez Fontan, J. J.; Turner, B. S.; Heldt, G. P.; Gregory, G. A.

In: Journal of Applied Physiology, Vol. 61, No. 4, 1986, p. 1431-1437.

Research output: Contribution to journalArticle

Perez Fontan, J. J. ; Turner, B. S. ; Heldt, G. P. ; Gregory, G. A. / Pulmonary mechanics during rapid mechanical ventilation in rabbits with saline-lavaged lungs. In: Journal of Applied Physiology. 1986 ; Vol. 61, No. 4. pp. 1431-1437.
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