Bed-side Pulmonary Function Testing and Continuous In-line Mechanics - What Can We Learn from Loops and Waves?

Overview

The modern trend in the therapy of severe respiratory failure in children is to avoid the adversive effects of conventional mechanical ventilation by optimal ventilator setting. On most PICUs and NICUs the setting of the ventilator is made empirically by following the patient-ventilator interaction, and later verified by blood gas analysis.The Bicore CP-100 minor makes possible continuous sampling of many parameters of ventilation and pulmonary mechanics in the newborn, infants and older children. When a flow transducer is used, one can continuously measure proximal airway pressure (PAW) and flow (V), when moreover the oesophageal balloon catheter and occlusive valve were used one can get information on the oesophageal pressure (Pes) and the values of ventilation under semistatic conditions. From direct by measured parameters the monitor placed in line can calculate many further data. The author made measurements of dynamic and semistatic conditions in 65 newborns, 25 infants and in 15 children treated by mechanical support for respiratory failure. According to the author’s experience careful monitoring of dynamic parameters of ventilation and pulmonary mechanics is sufficient for a change of ventilator setting. Measurements made intermittently under semistatic conditions add little or nothing for correction of ventilator setting in routine clinical practice. Following of dynamic parameters is useful mainly for detection of overstretching and autoPEEP. Continuous following of changes in the dynamic compliance (Cdyn) is useful for evaluating the response or non-response after surfactant replacement therapy and from the aspect of prognosis of survive in the course of ECMO. Monitoring of airway resistance provides valuable information concerning response to bronchodilation therapy in cases of BPDs. A flow transducer can detect even small tidal volumes during HFO.In summary, continuous monitoring of ventilation parameters and pulmonary mechanics assessment enable the clinical to make conventional ventilation more „baby friendly“ and where the risk of volu/barotrauma is high, it can be a signal to stop further conventional treatment and to select some other protective modes of ventilation. Pulmonary mechanics assessment will be a routine in future and it will be „the golden standard“ as is blood gas monitoring nowdays. A CT scan of the lungs seems to be the most sophisticated step for setting the ventilator correctly.

Key words:
pulmonary mechanics monitoring, conventional mechanical ventilation, non-conventional mechanical ventilation, barotrauma, volutrauma, respiratory failure