Indices | Low drive | High drive |
|---|
Clinical signs/symptoms | Apneasa | Respiratory distressb |
ΔPdi | < 3 cmH2O | ≥ 12 cmH2O |
Pmusswc | < 3 cmH2O | ≥ 15 cmH2O |
ΔPes | > − 3 cmH2O | < − 8 cmH2O |
PTP/minc | < 50 cmH2O*s/min | > 200 cmH2O*s/min |
P0.1 | < 1–1.5 cmH2O | > 3.5–4 cmH2O |
Poccld | > − 4 cmH2O cmH2O | ≤ − 20 cmH2O |
- ΔPdi: trans-diaphragmatic pressure increase during inspiration; Pmussw: pressure swings of respiratory muscles (inspiratory and expiratory) during the breath; ΔPes: negative change in esophageal pressure from the end-expiratory level; PTP/min: esophageal pressure (Pes)–time product per minute (PTP/min), calculated as the difference between Pes and the chest wall elastic recoil pressure during inspiration
- aThe only reliable clinical sign of low drive in a mechanically ventilated patient is the occurrence of repetitive apneas (Cheyne–Stokes breathing) as a result of over-assist
- bClinical signs and symptoms indicating respiratory distress are numerous, including accessory inspiratory muscles use, expiratory muscles contraction, diaphoresis, tachycardia, nose flaring, intercostal retraction and dyspnea
- cCalculation of Pmussw and PTP/min necessitates measurement of chest wall elastance (passive conditions, unreliable in patients with active breathing)
- dWhen Poccl is multiplied by − 0.75 and − 0.66, a gross estimate of Pmussw and ΔPes from un-occluded tidal breaths can be obtained, respectively
