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Ventilatory depression by halothane in infants and children
Insights
Infants show a greater decrease in tidal volume (VT) than children during halothane anesthesia. This study investigated age-related respiratory differences in infants and children under varying halothane concentrations.
Area of Science:
- Anesthesiology
- Pediatric Pulmonology
- Respiratory Physiology
Background:
- Halothane anesthesia affects respiratory mechanics differently in infants and children.
- Previous studies noted a greater decrease in tidal volume (VT) in infants compared to children.
Purpose of the Study:
- To investigate age-related differences in respiratory responses to halothane anesthesia.
- To analyze inspiratory flow, CO2, and pressure waveforms during spontaneous and occluded inspirations.
Main Methods:
- Recorded flow, pressure, and PCO2 in 15 infants and 15 children at varying halothane concentrations (inspired: 0%, 1%, 2%).
- Analyzed parameters including minute ventilation, inspiratory time, tidal volume, and respiratory drive (dP/dt, PMAX).
- Estimated respiratory mechanics (E'rs).
Main Results:
- Tidal volume (VT) and total time (Ttot) decreased with increasing halothane concentration in both groups (P < 0.05).
- End-tidal CO2 (PETCO2) increased in both groups, with a proportionally greater increase in infants.
- Infants exhibited a more pronounced reduction in VT compared to children.
Conclusions:
- Halothane anesthesia significantly impacts respiratory parameters in both infants and children.
- Age-related differences in respiratory drive and mechanics contribute to the observed variations in response to halothane.
- Further research is needed to fully elucidate the mechanisms behind these age-specific respiratory adaptations.
Abstract:
The purpose of this study was to extend previous observations of a greater decrease in tidal volume in infants than in children during halothane anaesthesia. We analyzed the inspiratory flow waveform recorded during spontaneous ventilation in: infants, two to six months of age, and children, one to five years of age. In addition we analyzed the CO2 signal and the pressure waveform during an occluded inspiration. The pressure generated during the initial 100 msec of inspiratory occlusion, an index of respiratory drive, was analyzed to give some insight into the aetiology of the age-related differences. In 15 infants and 15 children, Flow (V), pressure (Pao) and PCO2 were recorded at three concentrations of inspired halothane (FIH): 0%, 1% and 2% which correspond to an endtidal halothane concentration of about 0.3%, 0.9% and 1.3% respectively. Data were analyzed for minute ventilation (Vi) and parameters of timing (Total time (Ttot), Inspiratory time (Ti)), the amplitude of the neural output (mean inspiratory flow (VT/Ti), tidal volume (VT)) and the shape of the inspiratory breath profile (the inspiratory centroid flow (Ci/Ti), the inspiratory duty cycle (Ti/Ttot)). In some, the airway was occluded at end expiration and the slope of the initial 100 msec of occlusion (dP/dt) together with the maximal negative pressure (PMAX) were measured. Estimates of respiratory mechanics E'rs (PMAX/VT) and (VT/Ti)/(dP/dt) were obtained. The VT and Ttot decreased with increasing FIH in both infants and children (P < 0.05). The PETCO2 increased in both groups and the % increase was greater in infants.(ABSTRACT TRUNCATED AT 250 WORDS)