Elsevier

Clinics in Perinatology

Volume 28, Issue 3, 1 September 2001, Pages 561-578
Clinics in Perinatology

PROPORTIONAL ASSIST VENTILATION IN INFANTS

https://doi.org/10.1016/S0095-5108(05)70107-XGet rights and content

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THE CONCEPT OF PROPORTIONAL ASSIST VENTILATION AND RESPIRATORY MECHANICAL UNLOADING

The strategy of proportional assist ventilation (PAV) and respiratory mechanical unloading (RMU) is fundamentally different from the conventional perception of a ventilator being a pump. Conventional modes of patient-triggered ventilation typically synchronize one or two events of the ventilator cycle to certain points in the respiratory cycle. In contrast, with PAV the ventilator pressure is servocontrolled throughout each inspiration. During full-cycle RMU, airway pressure is servocontrolled

Terminology and Therapeutic Objectives

Although the basic concept of mechanical unloading for conditions characterized by impaired respiratory mechanics dates back to the 1950s,3 servocontrolled respiratory unloading devices with an appropriate dynamic response for adults24, 26, 27, 48 and infants29, 30, 31, 32 have been designed since the 1980s.

Investigators have used diverse terminology, such as negative impedance ventilation,15, 25 negative ventilator elastance and resistance,32 or resistive-elastic unloading.41, 42 The term

Hypoventilation and Apnea

Conventional patient-triggered ventilation modalities, such as assist-control or pressure support ventilation, provide a preset constant inspiratory inflation pressure for each triggered breath. This cycling pressure guarantees a minimum tidal volume (dependent on patient compliance and resistance), even if the inspiratory effort is so weak that it just triggers but does not contribute to the tidal volume. With stronger efforts, the mechanical tidal volume is added to the tidal volume generated

Selecting the Type and Degree of the Assist

The use of PAV-RMU follows basic principles of respiratory physiology. In contrast to conventional mechanical ventilation, it enables the clinician to address specifically the three main types of derangements in respiratory function: (1) decreased compliance, (2) increased resistance, and (3) decreased functional residual capacity. When applying PAV-RMU, the clinician selects three independent settings to address the individual degree of impairment in compliance, resistance, and functional

SUMMARY

Proportional assist ventilation and respiratory mechanical unloading is a new mode of respiratory assistance that produces similar gas exchange with lower airway pressures than conventional ventilation in infants. This is achieved by tailoring the ventilator pressure contour to the specific derangements in lung mechanics and by a near perfect synchronization with the infant's own inspiratory effort. In contrast to conventional ventilation, PAV only amplifies the effect on ventilation of the

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    Address reprint requests to Eduardo Bancalari, MD Department of Pediatrics (R-131) Division of Neonatology University of Miami School of Medicine PO Box 016960 Miami, FL 33101 e-mail:[email protected]

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