Test 5 Flashcards
Monitoring lung and chest wall compliance
- Compliance testing for inflection points
- Static compliance
Compliance testing for inflection points
- Deliver set volume and measure pressure, add a set volume and pressure until full
- Plot these points and look for lower inflection point and upper inflection point
- Ventilate with PEEP slightly above inflection point and / or plateau pressure below upper inflection point
Static compliance
^V/^P
Two kinds of compliance
Dynamic and Static
-static is the more common
Dynamic: Peak
Static: insp hold/ pause/ plateau
Corrected Vt
corrected tidal volume should be used because you want to use only the volume to the lung, not the circuit
Try to use the Vt and Plat from the same breaths
-AutoPEEP should be measured and used if possible
Corrected Vt/ Plat-PEEP=Clst
What does static compliance tell us
stiffness of the lungs and chest wall
Compliance values for intubated pt
Norm 70-100 unusual for vent pt mild 40-70 moderate 30-40 Severe <30 ARDS <25 unweanable
Whats most important when looking for changes in lung status
Trending values (plat)
Airway resistance equation
^Pressure/ ^flow (V) ((lpm-> L/S=cmH2O/L/s))
Peak pressure-Plateau pressure/ Peak Flow (L/s)
or just
Peak - Plateau
Ranges for Airway Resistance
norm 0-10cmH2O/L/s
moderate 11-15
severe >15
Airway pressure ranges
Peak: great concern over 50
Plateau: kept below 30-35 (below 30, O2 problems)
-consider PCV if pressure excessive
-Mean airway pressures increase for better oxygenation reduce to keep side effects down to a minimum
Mean Airway Pressures
increase for better oxygenation, reduce to keep side effects down
AutoPEEP
air that is not exhaled before next breath
Best way to tell if there is auto PEEP
check the flow/time curve
-if flow does not return to baseline, pt has autoPEEP
(this does not give you a number)
Do autoPEEP maneuver to get actual number (exp.hold)
How to fix Auto PEEP, increase expiratory time. how?
Shorten Ti(pt. with obstructive airways) -will go in faster, increasing pressures Decrease RR, lengthen resp cycle -Change CO2 and pH Decrease Vt, less to exhale Increase flow rate, -square waveform SIMV mode match PEEP
Inverse I:E when
ARDS, improve O2
Monitor breathing efforts and patterns, Work of breathing
small airway:us as large ETT as possible system imposed: effort to open valve to initiate breath(demand valves) Use flow sensitivity PSV sensitivity set appropriately keep flows set appropriately keep Raw low, bronchodilators, suction, etc treat cause of MV
Monitoring breathing efforts and patterns
WOB
Esophageal pressure monitoring:amount of pressure within chest
Oxygen cost of breathing: Paralyze pt, O2 is used on important organs
Assessing ventilatory drive, daily spontaneous breathing trial: decreasing pt problems, extubate ASAP
Vent Checks, monitoring for
integrity of the airway and circuitry, including secretions
The prescribed settings and assess for appropriateness
Acceptable gas exchange values
Respiratory system mechanics
Comfort and synchrony of breathing of the patient
Setting of alarms
Other safety issues
Flow Rate problems
Look for flow pattern to be even and pt not trying to exceed the set fl
Trigger Problems
Excessive pt effort right before breath starts
Deflection on pressure/time curve is pressure triggering
Doesn’t happen as much on flow triggering
Cycle Problems
Double breathing or breath stacking, too small volume?Forcing exhalation if breath taking too long for patient (Ti)
Assessing Graphics- Volume/ Pressure Loop
Look for inflection point to set PEEP
Look for beaking to assess overdistension
Assessing Graphics- Flow/ Volume Loop
Just like the FVC loop on PFT
Look for faster flows to assess airways
Pre and post bronchodilator assessment
Trouble shooting-Causes of sudden respiratory distress, Patient:
Airway Pneumothorax Secretions Anxiety Asynchrony
Trouble shooting-Causes of sudden respiratory distress, Vent:
Leak(ETT, Humidifier, Tubing connections) Trigger Flow Circuit Asynchrony
Imminent death
Consider removing airway if you think it is an airway problem
CXR(if time) or needle if think it is a pneumo
Could be non-respiratory,
continue to bag until issues addressed
When all patient and mechanical causes can be eliminated then consider sedation
Paralyze patient only if absolutely necessary
After the patient has been physically assessed, the mechanical ventilator should be checked routinely to ensure that:
Settings are correct
Ventilator is meeting the patient’s needs
Circuit is not compromised
Alarms are set and functioning
-Ventilator waveform analysis of flow, volume, and pressure may reveal such problems as leaks in the system, inadequate ventilator sensitivity, lung overdistension, and many other problems.
If inspiratory time is constant, as in the case of a paralyzed patient, who is breathing at a set rate of 16 bpm, the square flow pattern results in
higher peak airway pressures (PIP) than the decelerating flow pattern.
-Thus if a square waveform was initially selected and PIP were high (pressure is variable during volume control), a change to a decelerating ramp waveform would reduce the PIP, keeping in line with our lung-protective ventilation strategies to try to prevent VILI.
Auto-PEEP can be assessed directly by most modern ventilators through the use of an
exp hold maneuver
-It can also be detected on the volume, flow, and pressure waveforms.
The volume waveform can quantify
the amount of volume that is being trapped.
The flow waveform will demonstrate
incomplete exhalation prior to a subsequent breath through failure of the flow waveform returning to baseline.
Auto-PEEP can be corrected by
extending the expiratory time, or compensated for by setting PEEP close to auto-PEEP levels to reduce the excessive trigger effort required by the patient.
Alarms
High/low volume = 10% or 100 mL above/below set value
High/low V̇e = 20% or 1 to 2 L above/below set value
High/low PIP= 10 cm H2O above/below PIP
High/low Fio2 = 5% above/below set Fio2
High RR = 10 breaths above
Apnea time = less than 20 seconds
There are many factors that contribute to Paw during mechanical ventilation, including:
PIP
PEEP
I:E ratio
Flow
norm Ti
0.8-1.2
The major ventilator parameters that are typically included in a written order are
Ventilator mode Tidal volume (Vt) or inspiratory pressure (Pi) Respiratory rate (RR) Fraction of inspired oxygen (Fio2) PEEP
norm inspiratory flow rates
40-100
Patients who will be receiving mechanical ventilation under emergent conditions will display signs of the four major indicators for mechanical ventilation:
Acute ventilatory failure
Impending ventilatory failure
Severe oxygenation defects
Apnea
Static compliance represents
lung compliance during periods of zero air flow, and as such, uses Pplat in its equation.
Dynamic Compliance represents
lung compliance during periods where gas flow is present, and as such, uses PIP in its equation.
With increased resistance,
PIP rises and Pplat remains the same.
With decreased compliance, PIP
PIP rises and Pplat rises a commensurate level.
What ventilation parameters are used to evaluate a patient’s lung compliance?
AutoPEEP
PEEP
PIP
Plat
What impact will increased airway resistance due to secretions or bronchospasm have on airway pressures monitored during mechanical ventilation?
Increased PIP, unchanged Pplat
Asynchrony can be categorized in accordance with its cause:
Trigger asynchrony
Flow asynchrony
Cycle asynchrony
