Pressure-Volume & Flow-Volume Loops Flashcards
Why monitor spirometry?
Airway obstruction & bronchospasm have highest incidence of severe injury
Fresh gas decoupling
Fresh gas is diverted by a decoupling valve to the manual breathing bag, and is thus not added to the delivered tidal volume- manual breathing bag inflates during inspiration & deflates during expiration (contents empty into absorbant and move on toward patient)
D-lite sensor technology
Flow signal conducted as a pressure difference- allows continuous dynamic compliance using end-inspiratory plateau pressure
Tidal Volume
Volume of gas entering or leaving patient during inspiratory or expiratory phase time
Minute Ventilation
RR x TV (*with her x dosing narcotic)
Ppeak
Maximum airway pressure during inspiratory phase time in cmH2O
Pplat
End inspiratory pressure after inspiratory pause in cmH2O
Pmean
Mean inspiratory pressure in cmH2O
PEEP
Positive end-expiratory pressure (at end of exhalation) in cmH2O
I:E
Ratio of inspiratory and expiratory times
Raw
Dynamic airway resistance (cm H2O/L/second)
Compliance
Ratio of change in volume/change in pressure in mL/cmH2O – dynamic compliance– measurement of well lung-thoracic system can change its total volume as changing pressure is applied [exp TV/(pressure at end of inspiration - pressure at end of expiration)
What can Pplat be used for?
A pause at the end of inspiration may benefit alveolar gas distribution from compliant to less compliant while maintaining lower airway pressures - beneficial for restrictive disease
How is PEEP identified on pressure-volume curve?
Rightward shift on horizontal axis
How is PEEP identified on airway pressure waveform?
Elevation from baseline of zero
Calculating I:E of 1:2, RR 10/min
Have a 6 second breath (60 sec/10), and 3 parts (1:2 ~> 1+2), 6/3 = 2 sec for inspiration leaving 4 for expiration
Why would you increase inspiratory time length?
Increase mean airway pressure, allow redistribution of gas from more compliant to less
What are the disadvantages of longer inspiratory times?
Increase risk of gas trapping, intrinsic PEEP, barotrauma, less well tolerated, decrease peak pressure at expense of decrease inspiratory flow, dangerous for COPD because they need longer amount of time to exhale
Normal adult & pediatric compliance
Adult: 35-100 mL/cmH2O (usually about 60), Ped: About 15 mL/cmH2O
When would you see a decrease in compliance?
Inadequate muscle relaxation, laparoscopic case, pneumoperitoneum, tumor, air embolism, narcotics, bronchoconstriction
Elastitance
Change in pressure/change in volume
Increase in resistance from what?
Obstruction, bronchoconstriction, airway collapse, too small ETT
When would you see peak pressure increase?
Deep trendelenberg, one lung intubation
What is the difference between the dotted line & the solid line?
Addition of PEEP (shifts rightward on x axis)
What is this picture representing?
Decrease compliance, more pressure is required to fill the lungs at a given volume, slope moves towards horizontal
What does this picture represent?
Unintentional one lung intubation - peak pressure increases
What does this picture represent?
Endobronchial intubation (one-lung), not as much tidal volume and decreased expiratory flow
What does this picture represent?
Esophageal intubation, increased pressure needed for small volume
What does this picture represent?
Esophageal intubation (irregular inspiratory and expiratory parts)
What does this picture represent?
Decreased tidal volume from kink in ETT
What does this picture #1 to #2 represent?
Kink in ETT causes high peak pressure, low compiance, high resistance and decreased tidal volume (solid line)