PubMed · 2205122
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B E Smith. 1990. High frequency weaning.. https://doi.org/10.1111/j.1365-2044.1990.tb14408.x
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OBJECTIVE: To test a high-frequency jet ventilator, the Mistral (Acutronic Laboratory) on a lung model. METHODS: The jet ventilator Mistral was tested with two connectors (7 and 20 ml) and four catheters. Pressure and flow measurements were performed by varying the driving pressure (1 to 3 bars), the I/T ratio (0.25, 0.35, 0.45) and the frequency (1 to 5 Hz). Recorded data were: the volume delivered by the ventilator, the pressure measured in the connecting line between the ventilator and the injector and the difference between the end expiratory pressure measured by the ventilator through the injector and the tracheal pressure. RESULTS: An increase in driving pressure induced a proportional increase in minute volume whatever the injection catheter used. After insufflation, when a Seldicath catheter was used, the pressure decrease was the slowest and the time constant the longest. Increase in frequency or I/T ratio, particularly beyond 0.35, was associated with an increase of the end expiratory pressure measured by the respirator. The gradient of pressure measured by the respirator and by an external sensor was lower with the 7 ml connector whatever the catheter used, and was larger with the Seldicath catheter. CONCLUSION: The use of a low volume connector should be preferred, because it allows the measurement of the end expiratory pressure for a larger range of driving pressure, expiratory time and catheters. The performances of the Seldicath catheter are below those of the other catheters studied.
BACKGROUND: Chronic pulmonary disease is a major cause of mortality and morbidity in very low birth weight infants despite increased use of antenatal steroids and surfactant therapy. Ventilator injury and oxygen toxicity are thought to be important factors in the pathogenesis of chronic pulmonary disease. There is evidence in animal studies and adult human studies that high frequency jet ventilation may reduce the severity of lung injury associated with mechanical ventilation. OBJECTIVES: In preterm infants with severe pulmonary dysfunction, does the use of high frequency jet ventilation (HFJV) compared to conventional ventilation (CV) reduce mortality and morbidity without an increase in adverse effects? SEARCH STRATEGY: We searched MEDLINE (1966 - August 2005), Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 3, 2005), and EMBASE (1988 - August 2005). Information was also obtained from experts in the field and cross references were checked. SELECTION CRITERIA: Randomized and quasi-randomized controlled trials of rescue high frequency jet ventilation versus conventional ventilation in preterm infants born at less than 35 weeks of gestation or with a birth weight less than 2000 grams with respiratory distress were included in the systematic review. DATA COLLECTION AND ANALYSIS: The standard methods of the Cochrane Neonatal Review Group were used, including independent trial assessment and data extraction. Data were analysed using relative risk (RR) and risk difference (RD). MAIN RESULTS: Two randomized trials were identified. One trial (Engle 1997) was excluded as the study was restricted to term and near-term infants. The included trial (Keszler 1991) randomized 166 preterm infants and reported data on 144 infants. Cross-over to the alternate treatment was permitted if the initial treatment failed. There was no statistically significant difference in the overall mortality (including survival after cross-over) between the two groups [RR 1.07, (95% CI 0.67, 1.72)]. The survival by original assignment was identical. In a secondary analysis, the study demonstrated rescue treatment with HFJV, up until the time of cross-over, was associated with lower mortality, [RR 0.66 (95% CI 0.45,0.97)]. No significant differences were found in the incidence of CLD in survivors at 28 days of age, IVH, new air leaks, airway obstruction and necrotizing tracheobronchitis. AUTHORS' CONCLUSIONS: There was no significant difference in the overall mortality between rescue high frequency jet ventilation and conventional groups. In a secondary analysis, rescue treatment with HFJV, up until the time of cross-over, was associated with lower mortality. There was no significant increase in adverse effects like intraventricular hemorrhage, new air leaks, airway obstruction and necrotizing tracheobronchitis with rescue high frequency jet ventilation. The included study was done before the introduction of surfactant and widespread use of antenatal steroids. The number of infants included was small and there were high numbers of post randomization exclusions. Due to the crossover design and small numbers of infants in the included study, there is insufficient information to assess the effectiveness of rescue HFJV in preterm infants. Studies that target the most at-risk population and have appropriate power to assess some of the important outcomes are needed. These trials would also need to incorporate long term pulmonary and neurodevelopmental outcomes.
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