Pressure support ventilation (PSV) is the most commonly used mode in mechanical ventilated patients. Studies have shown that over-assistance was prevalent in patients undergoing PSV. Up to now, no reliable method has been recommended to select an "optimal" inspiratory support level. Pressure muscle index (PMI) was introduced recently to evaluate the degree of spontaneous breathing effort. We hypothesize that PMI might be used as an indicator for over-assistance during PSV. In this randomized crossover study, inspiratory support is set at three levels according to negative, positive and zero PMI. Inspiratory effort, work of breathing, and respiratory mechanics are compared among the three inspiratory pressure support levels.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
SUPPORTIVE_CARE
Masking
SINGLE
Enrollment
20
Inspiratory support is the pressure delivered by the ventilator during pressure support ventilation.
China-Japan Friendship Hospital
Beijing, Beijing Municipality, China
RECRUITINGBeijing Tiantan Hospital
Beijing, Beijing Municipality, China
RECRUITINGInspiratory effort
Inspiratory effort is measured as pressure generated by inspiratory muscles using esophageal pressure monitoring.
Time frame: 30 minutes
Work of breathing
Work of breathing is measured by the Campbell diagram and pressure-time-product using esophageal pressure monitoring.
Time frame: 30 minutes
Respiratory system compliance (ml/cmH2O)
Respiratory system compliance is calculated as the ratio between tidal volume and driving pressure.
Time frame: 30 minutes
Partial pressure of oxygen in arterial blood (mmHg)
Partial pressure of oxygen in arterial blood is obtained by blood gas analysis.
Time frame: Partial pressure of oxygen in arterial blood
Partial pressure of carbon dioxide in arterial blood (mmHg)
Partial pressure of carbon dioxide in arterial blood is obtained by blood gas analysis.
Time frame: 30 minutes
Respiratory rate (breaths/min)
Respiratory rate calculation includes ineffective trigger.
Time frame: 30 minutes
Tidal volume (ml)
Tidal volume is obtained by intergation of flow-time tracing.
Time frame: 30 minutes
Rapid shallow breathing index
Rapid shallow breathing index is calculated as the ratio between respiratory rate and tidal volume.
Time frame: 30 minutes
The use of accessory respiratory muscle
The use of accessory respiratory muscle is observed at the bedside.
Time frame: 30 minutes
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