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A forced perturbation method of assessing pulmonary mechanical function in intubated infants
K J Sullivan1, M Durand, H K Chang
1Department of Biomedical Engineering, University of Southern California, Los Angeles 90089-1451.
Insights
Short airway pressure pulses help assess pulmonary function in infants with respiratory distress. This method identifies patient classes linked to ventilation therapy duration and airway resistance changes.
Area of Science:
- Pediatric Pulmonology
- Respiratory Mechanics
- Medical Engineering
Background:
- Infants with acute respiratory distress syndrome or bronchopulmonary dysplasia require mechanical ventilation.
- Long-term ventilation can lead to significant changes in pulmonary mechanical function.
- Assessing these changes is crucial for optimizing patient care.
Purpose of the Study:
- To evaluate the use of short airway pressure pulses for assessing pulmonary mechanical function in ventilated infants.
- To identify distinct patient classes based on their response to pressure pulses.
- To correlate these classifications with clinical parameters like ventilation duration and airway resistance.
Main Methods:
- Short airway pressure pulses (2 Hz) were applied to intubated, spontaneously breathing infants for 20-30 seconds.
- Pulses were delivered via a mechanical oscillator, maintaining mean airway pressure.
- Impedance spectra were analyzed to identify local resonance, classifying patients into two groups.
Main Results:
- Two distinct patient classes were identified based on the presence or absence of local resonance in impedance spectra.
- Classification was independent of mean airway pressure, suggesting robustness.
- Patient classification correlated with the duration of ventilation therapy and indicated changes in peripheral airway resistance and central airway shunting.
Conclusions:
- Brief airway pressure pulses can effectively assess pulmonary mechanical function in preterm infants undergoing mechanical ventilation.
- This technique may help detect changes associated with long-term ventilation therapy.
- The findings suggest potential for monitoring disease progression and treatment response.
Abstract:
Short pulses in airway pressure were used to assess the pulmonary mechanical function of nine infants suffering acute respiratory distress syndrome or bronchopulmonary dysplasia. All patients were intubated, spontaneously breathing, and mechanically ventilated at the time they were examined. The endotracheal tube was disconnected from the ventilator and connected to a mechanical oscillator that produced brief pulses in airway pressure at a rate of two pulses/s. These pulses were applied to the infants airway for 20-30 s, at which time the infant was replaced on the ventilator. The mean airway pressure during the procedure was maintained at the level of the positive and expiratory pressure that was set on the ventilator. Two classes of patients were identified from the pulse response primarily by the presence or absence of a local resonance in the impedance spectra. Similar results were obtained in five other patients who were examined with zero mean airway pressure, suggesting that the pulse response is little influenced by changes in mean lung volume or total lung compliance. Patient classification appeared related to the duration of ventilation therapy and the transition from one class to another was consistent with the development of high peripheral airway resistance and significant volume shunting in the central airways. These results suggest that brief pulses in airway pressure can be used to detect changes in the pulmonary mechanical function of preterm infants that result from long-term ventilation therapy.