Evaluation of the inspiratory pressure using a digital vacuometer in mechanically ventilated patients: analysis of the time to achieve the inspiratory peak.

BACKGROUND: The measurement of the maximal inspiratory pressure (P(Imax)) is of great importance in choosing the time for the start of weaning. OBJECTIVE: To measure the inspiratory pressure in mechanically ventilated patients suitable for weaning to determine the point at which the P(Imax) is achieved within 60 seconds of observation, and analyze factors associated with P(Imax) values. METHODS: Measurement of P(Imax) was accomplished with a digital vacuometer with a unidirectional valve, which allows only exhalation (P(ImaxUV)). With this technique, values are registered and stored, remaining accessible whenever necessary. All patients were on mechanical ventilation, and met the criteria recommended by the American Thoracic Society/European Respiratory Society in 2007 to undergo weaning trial. RESULTS: Eighty-four from the 87 enrolled patients completed the test. No patients reached the P(ImaxUV) in the first 20 seconds of observation. P(ImaxUV) was achieved between 20.1 and 40 seconds in 12 patients (14.0%), and between 40.1 and 60 seconds in 72 cases (86.0%). In a multivariate analysis model in which age, sex, days of mechanical ventilation, APACHE score, and respiratory drive (measured as airway-occlusion pressure 0.1 s after the start of inspiratory flow [P(0.1)]) were included, only age (P = .006) and P(0.1) (P = .003) were significantly associated with the values of P(ImaxUV). CONCLUSIONS: Within an observation period of 60 seconds, the majority of patients reached the maximal inspiratory peak between 40.1 and 60 seconds. Older patients were found to have lower P(ImaxUV) values, whereas higher values for P(0.1) strongly correlated with higher P(ImaxUV) values. These findings are potentially useful to improve successful weaning prediction in the future, but further studies are needed to better clarify this issue.

Intermittent bag ventilation of preterm infants on continuous positive airway pressure: The effect on transcutaneous PO2.

Preterm infants with respiratory distress syndrome requiring continuous positive airway pressure are frequently assisted with intermittent bag ventilation. We assessed the effect of intermittent bag ventilation on PO2 in these infants by continuous monitoring with a transcutaneous oxygen electrode. The behavior of the infants during bagging determined the effect on PO2. Bag ventilation decreased PO2 significantly (P less than 0.01) in infants who were restless during bagging, whereas a significant increase in PO2 (P less than 0.02) was observed in infants who were quiet while being bagged. Although the duration of the increase in PO2 was variable, a sustained rise (greater than 20 minute) occurred in almost half of the infants studied. Intermittent bag ventilation appears to be beneficial in infants who remain quiet during the bagging period.