Ventilator high pressures
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High Pressure Alarms
- In volume control mode, (high)pressure alarm sounds. In pressure control mode (low) volume alarm sounds--BOTH signify similar problems and troubleshoot with the following 4 maneuvers.
Measure Peak Plateau Pressure
- Need to measure peak plateau pressure P(Plat) not only peak airway pressure P(Peak).
- Press and hold the “inspiratory hold” button-waveform shows peak pressure and then lower plateau.
- P(Plat) >30 thought to be potentially injurious to lung.
- P(Plat) reflects equilibration of airway pressures without flow, accounts for airway resistance.
Determine Airway Resistance
- When airway resistance high, P(Peak)>> P(Plat)
- Normal P(Peak)-P(Plat) < 5cm H2O
- Airway resistance increased with: asthma, mucus plugging, small tube, tube kinking, tube obstructed
- Normal P(Peak)-P(Plat) < 5cm H2O
Eval for Dynamic Hyperinflation
- Flow at end of expiration has not stopped, ie breath stacking, ie need more time to exhale and each breath adding volume to lungs
- Consequence of dynamic hyperinflation
- Harder to trigger vent- dys-synchrony
- Increased dead space- hypoxic/hypercapneic
- Elevated intra-thoracic pressures decrease venous return
- Look to make sure expiratory flow returns to baseline.
Measure Hyperinflation
- If you suspect dynamic hyperinflation, perform “expiratory hold”, then PEEP on ventilator may be higher than PEEP on ventilator settings
- Differences in PEEP with “expiratory hold” and PEEP set on ventilator suggest hyperinflation.
Management
High P(Peak), Low P(Plat)
- Suggests increased airway resistance, not compliance problem
- Kinked tube- pass suction catheter?
- Mucus plug- pass suction catheter and suction
- Bronchospasm- inhaled bronchodilators
- Tube too small- swap tube
High P(Peak), High P(Plat)
- Suggests decreased compliance, not an isolated resistance problem
- Mainstem bronchus- pull back ETT, CXR?
- Atelectasis- bronchoscopy
- Cardiogenic [[[pulmonary edema]]-diuretics vs inotropes
- ARDS- lower Vt
- Pneumothorax- Chest tube
- Pneumonia- Antibiotics
PEEP measured > PEEP Vent Setting
- Suggests Dynamic Hyperinflation
- Remove from vent, allow complete exhalation
- Lower ventilator rate
- Shorten I-time to change I:E around 1:4
- Tidal volume 6-8mL/kg predicted body weight
- Increase inspiratory flow rate to 60-80L/min to allow more exhalation time
- Opioid sedation blunts intrinsic tachypnea
- Treat bronchospasm