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Breathing circuit respiratory work in infants recovering from respiratory failure
1Department of Anesthesiology, University of South Florida, College of Medicine, Tampa 33612-4799.
Insights
Continuous-flow breathing circuits did not affect infant cardiopulmonary function, but high-flow resistance circuits increased airway pressure fluctuations. Evaluating breathing circuit characteristics is crucial to prevent increased respiratory work in infants.
Area of Science:
- Pediatric critical care medicine
- Respiratory physiology
Background:
- Continuous-flow breathing circuits are used for spontaneous breathing in infants.
- The exhalation valve's flow resistance can vary significantly between circuits.
Purpose of the Study:
- To compare cardiopulmonary function in infants breathing spontaneously using three continuous-flow circuits with differing exhalation valve resistance.
- To assess the impact of breathing circuit characteristics on respiratory mechanics.
Main Methods:
- A randomized crossover trial involving 12 infants (3-10 kg) recovering from respiratory failure.
- Cardiopulmonary function was assessed after 15 minutes of equilibration on each circuit, with constant airway pressure and FIO2.
Main Results:
- No significant differences in ventilation, gas exchange, or circulatory function were observed across circuits.
- Airway pressure (Paw) and esophageal pressure fluctuations increased with higher exhalation valve resistance, particularly in infants over 4.5 kg.
- A threshold-resistor circuit reduced Paw fluctuations by over 2 cm H2O in 10 of 12 infants.
Conclusions:
- The choice of continuous-flow breathing circuit can impact respiratory mechanics in infants.
- Evaluating breathing circuit characteristics is essential to minimize equipment-induced increases in respiratory work for infants and children.
Objective:
To compare cardiopulmonary function during spontaneous breathing with three continuous-flow breathing circuits. The major difference between these circuits was the degree of flow resistance offered by the exhalation valve.
Design:
Randomized crossover trial.
Patients:
Twelve infants less than 12 months of age recovering from respiratory failure of variable etiology. Only patients weighing 3 to 10 kg were studied.
Interventions:
The patients were connected to each respiratory circuit in a random sequence, with 15 min allowed for equilibration before assessment of cardiopulmonary function. Airway pressure (Paw) and FIO2 were maintained unchanged.
Measurements And Main Results:
Ventilation, gas exchange, or circulatory function were not altered significantly by changing the breathing circuit. However, Paw and esophageal pressure fluctuations were altered and were largest during breathing with the circuit that had an exhalation valve with high-flow resistance. The Paw fluctuation recorded while the patient was breathing with the flow-resistor circuit increased with weight and exceeded 2 cm H2O in all patients weighing greater than 4.5 kg. Paw fluctuation could be decreased by greater than 2 cm H2O in ten of 12 patients by using the threshold-resistor circuit.
Conclusions:
The results indicate a need for evaluating the characteristics of respiratory circuits used for spontaneous breathing in infants and children, to avoid unnecessary equipment-related increase in respiratory work.