A respiratory jacket for ventilatory measurements in children

Identification of optimal lung volume during high-frequency oscillatory ventilation using respiratory inductive plethysmography

OBJECTIVES

First, to define the relationships between critical opening and closing pressures and oxygenating efficiency, and second, to address whether respiratory inductive plethysmography (RIP) could be used to monitor changes in thoracic volume that follow changes in mean airway pressure during high- frequency oscillatory ventilation (HFOV).

DESIGN

Prospective, interventional animal study.

SETTING

University research laboratory.

SUBJECTS

Five anesthetized, paralyzed, and ventilated pigs.

INTERVENTIONS

The animals were ventilated by using HFOV after lung injury. Pre- and post-HFOV pressure-volume curves were obtained by supersyringe. A pressure-volume curve was constructed during HFOV as mean airway pressure was increased from 10 to 40 cm H(2)O and then weaned back down to the minimum sustainable. Hemodynamic and oxygenation data were obtained at each data point.

MEASUREMENTS AND MAIN RESULTS

RIP-derived thoracic volumes correlated with known lung volumes during supersyringe (r(2) =.78, p <.00001). During HFOV, three of five animals had an identifiable critical opening pressure of the lung, and four of five had an identifiable critical closing pressure. No consistent relationship between critical opening and critical closing pressures was observed. During the weaning phase of HFOV, a relative decrease in RIP-measured volume of >10% predicted the decrease in oxygenation associated with reaching the critical closing pressure.

CONCLUSIONS

The ability of RIP to detect optimal lung volume during the weaning of mean airway pressure may allow clinicians to more directly monitor lung volume changes during HFOV and use the lowest possible airway pressures after lung recruitment.

Respiratory monitoring of the infant in anaesthesia and intensive care

Respiratory monitoring of children during general anaesthesia and critical care is in its early stages. Acquisition of physical information remains of great importance because of the difficulties in obtaining specific and objective data from paediatric patients. Many of the obstacles presented by them, such as small and rapid respiration, lack of patient cooperation, use of an uncuffed tracheal tube and relatively higher airway humidity to keep the small airway patent, have been overcome recently by sophisticated technology based on well known principles and thoughtful use of computers. It is now possible to monitor and apply many pulmonary function tests at the bedside that were once confined to the laboratory.