The Science Journal of the American Association for Respiratory Care

1998 OPEN FORUM Abstracts

THE USE OF NEGATIVE PRESSURE VENTILATION TO IMPROVE SECRETION CLEARANCE IN TWO PATIENTS FAILING CONVENTIONAL THERAPIES

Hilary Klonin, Michelle Peters, Parakkel Raffeeq*, Andrew Durward*, Jon Meliones, Ira Cheifetz. Divisions of Pediatric Critical Care at Duke University Medical Center, Durham, North Carolina and Hospital for Sick Children*, Toronto, Ontario.

Introduction. Negative pressure ventilation may be beneficial for improved secretion clearance in select patients either alone or in combination with positive pressure ventilation. High-frequency external chest wall compression has been shown to improve peripheral and central mucus clearance in a canine model.^{1,2} We report two pediatric patients in whom the secretion clearance mode of the negative pressure Hayek Oscillator (Breasy Medical, London) improved pulmonary function.

Case 1: The first case is a 4 month old infant with chronic lung disease of prematurity who had been recently extubated after recovery from ARDS. This infant subsequently developed complete collapse of the left lung and right upper lobe. This patient was ventilated using external chest wall oscillation with intermittent secretion clearance in order to avoid positive pressure ventilation and its associated risk of barotrauma, especially in vulnerable lungs. The lungs were re-expanded in 3 days and the need for reintubation was avoided.

Case 2: The second case is a 16 month old child with bronchiolitis obliterans and plastic casts of the airway who failed to improve after 18 days on ECMO. The secretions were successfully mobilized only after negative pressure ventilation was commenced. This patient's dynamic compliance increased from 0.35 mL/cm H_{2}O to 0.72 mL/cm H_{2}O over the first 24 hours on the Hayek Oscillator. The oxygenation index decreased from 15 to 5 (without a change in the oxygen delivery via the ECMO system). After 48 hours of using the secretion clearance mode, the child was weaned from ECMO. Two days later the child was successfully extubated.

Discussion. Negative pressure ventilation is a non-invasive form of respiratory support which when used alone avoids the complications associated with endotracheal intubation and positive pressure ventilation. When used in association with positive pressure ventilation, negative pressure ventilation may shorten the duration of ventilation. The Hayek Oscillator has the advantage of a highly effective secretion clearance mode which consists of oscillation around a negative pressure baseline followed by a "cough" mode which has a prolonged inspiration and a forced short expiration. The effects of this relatively new mode of ventilation on mucocilliary clearance are largely unexplored in humans. The laboratory data and case reports, such as presented here, support the need for a clinical trial of negative pressure ventilation for secretion clearance.

1 Gross et al. J Appl Physiol. 1985.

2 King et al. Am Rev Resp Dis. 1983.

The 44th International Respiratory Congress Abstracts-On-DiskĀ®, November 7 - 10, 1998, Atlanta, Georgia.

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