Assessment of the Mechanically Ventilated Patient Flashcards
An increase in PIP with no change in Pplat indicates what?
Increasing airway resistance
An increase in PIP and an increase in Pplat indicates what?
Decreasing compliance
List 5 causes of increasing airway resistance in an intubated, ventilated pt
- Increased secretions
- Bronchoconstriction (asthma, COPD)
- Biting the ETT
- Kinked ETT
- Small ETT
List 5 causes of decreasing compliance in an intubated, ventilated patient
- ARDS
- Pulmonary fibrosis
- Pneumothorax
- Scoliosis
- Morbid obesity
What is the calculation to determine resistance?
Raw = (PIP-Plateau) / VI (flow)
Normal: 10-15cmH2O/L/second
What is mPAW and what is the calculation used to determine it’s number?
mPAW = Mean Airway Pressure
0.5 x (PIP-PEEP) x (Ti/TCT) + PEEP, or 0.5 x (peak inspiratory pressure - PEEP) x (inspiration time / total respiratory cycle time) + PEEP
Eg. 0.5 x (30-5) x (1/4) + 5 = 8.125cmH2O
In the pressure-volume loop, which way will the curve shift if PEEP is applied?
The whole curve shifts to the right
What is the PaO2/FiO2 Ratio used for? How is it calculated?
- It indicates hypoxemia even if PaO2 normal due to supplemental O2 admin
- Used to indicate ARDS severity
- PaO2/FiO2 = normal of 300-500
What is the PaO2/FiO2 Ratio for mild, moderate and severe ARDS?
Mild: PaO2/FiO2 200-300 (mortality 27%)
Moderate: PaO2/FiO2 100-200 (mortality 32%)
Severe: PaO2/FiO2 <100 (mortality 45%)
What does a normal A-a gradient (5-10 mmHg) indicate in the setting of hypoxemia?
Normal A-a gradient indicates an oxygenation problem (hypoventilation or decreased inspired O2 from altitude)
What does an elevated A-a gradient indicate in the setting of hypoxemia?
An elevated A-a gradient indicates a diffusion problem (V/Q mismatch, R-L shunt or other impairment of gas diffusion)
What is the formula for achieving a desired ETCO2?
(Current ETCO2 x RR) / Desired ETCO2
Eg. (62mmHg x RR14) / 45mmHg = 19 breaths per minute to achieve an ETCO2 of 45 mmHg
