Irene Telias, Canada
Respiratory drive is the output of respiratory centers that control the magnitude of inspiratory effort
Why assess respiratory drive?
- Derangements are frequent
- Can have adverse consequences on diaphragm/lungs/ sleep
Respiratory control is complex
- Chemoreflex – pH, pCO2 and pO2 via central and peripheral chemoreceptors control the output of the respiratory center
- Multiple factors modify the drive in ICU patients (inflammation, metabolic demands, mechanical ventilation etc)
Monitoring
- Respiratory center cannot be monitored directly. Respiratory drive is a surrogate
- Measures of respiratory drive can be used to estimate inspiratory effort and vice versa
Techniques
- Electrical activity of the diaphragm (EAdi)
- Mechanical activation of diaphragm (Diaphragm Ultrasound)
- Esophageal or gastric pressure measurement
- P0.1 or Pocc
- P0.1 specific for respiratory drive
- Respiratory rate is not a good measure of the drive (except when it is <17 or >30 in ICU patients)
How is it done?
- Majority of vents do it
- P0.1 is the drop in airway pressure in the first 100 msec; Pocc is the drop in airway pressure during an end expiratory occlusion maneuver
- P0.1 – Surrogate of respiratory drive, validated
High Respiratory drive
- P0.1 > 3.5 – 4 cmH2O– High respiratory drive
- Identify modifiable factors (adjust flow and tidal volume, reduce dead space, treat infection, pain etc)
- PEEP and FiO2 adjustment
- Sedation and analgesia
Low respiratory drive
- 1 <1 cmH20
- Typically, in patients recovering from respiratory failure – usually on high levels of PS – causes apnea and disrupted sleep
- Reduce PS or use other modes