Test 3 Flashcards
General indicators for Mechanical ventilation
When support is needed bc patients inability to ventilate the lungs or maintain effective gas transport across the alveolcapillary membrane. This could be the result of lung disease or things such as, drug overdose or the need to paralyze and sedate for a surgical procedure
Apnea
the absense of spontaneous breathing, which can be the result of many factors, including drug overdose, paralysis, or neurologic insult
Acute Ventilatory Failure defined as
rising levels of PaCo2 with corresponding decrease in pH, resulting in respiratory acidosis
Acute ventilatory failure can be the result of
respiratory muscule dysfunction, excessive ventilatory load, impaired ventilatory drive, or dysfunctions of the lung parenchyma affecting gas exchange
Impending Ventilatory Failure based on
patient presentation and clinical judgement.
-known factors such as hx of pulmonary disease and acute physical manifestations such as increased WOB, Decreasing OX and or ventilation, and progressive worsening of symptoms such as dyspnea, may lead to clinician to suspect the acute vent failure is close at hand
Severe oxygenation defects is when
Result of an acute or chronic lund disease
- very high levels of inspired oxygen (FiO2) are required to maintain a minimally acceptable o2 status.
- Severe are unresponsive to O2 therapy (refractory hypoxemia)
Need for mech ventilation condensed into four primary factors
- Apnea
- Acute vent. failure
- Impending vent. failure
- Severe oxygenation defects
Two major types of mechanical ventilation are
- Volume control ventilation (VCV)
- Pressure control ventilation (PCV)
VCV
tidal volume is set and delivered regardless of pressure
- Method selected whenever a constant volume is needed to maintain a desired level of arterial carbon dioxide
- tradeoff is that changes in system mechanics such as resistance and compliance will influence PIP
PCV
inspiratory pressure is set and delivered regardless of tidal volume
PIP
Peak inspiratory Pressure, highest level of pressure applied to lungs during inhalation
As compliance goes down or resistance goes up, PIP
increases
As compliance goes up or resistance goes down, PIP
decreases
Factors that impact PIP during VC ventilation
- Peak inspiratory flow setting
- Inspiratory flow pattern
- Auto-PEEP
- Tidal Volume
- Resistance
- Compliance
Peak Inspiratory flow setting impacts PIP in VC ventilation
The peak inspiratory flow rate can be set and changed based on pts needs. A higher set peak inspiratory flow results in higher PIP
Inspiratory flow pattern impacts PIP in VC
(the pattern with which the inspiratory flow is delivered can also be changed by operator)
- In VC, a square or decelerating flow pattern are available choices
- The decelerating flow pattern is associated with lower PIP
PEEP impacts PIP
Baseline pressure at the end of exhalation
-Any pressure or volume support used during mech ventilation occurs above the baseline pressure, so increases in PEEP result in increases in PIP
Auto-PEEP impacts PIP
Due to air trapping raises the PEEP pressure, thereby elevating the PIP
increases in the set VT will result in what to PIP
higher PIP
Resistance to PIP
Increases in airway resistance result in increases in PIP.
-Common cause of increased resistance are secretions in the airway or bronchospasm of the smooth muscle lining the airway
Decreased compliance of the lung or chest wall will result in what PIP during VC
Result in elevated PIP during VC ventilation
-Decreased compliance could be due to a worsening of the patients pulmonary condition
During PCV
the airway pressure is set and remains constant during changes in compliance or resistance
-BC PIP is constant during PCV, changes in resistance and compliance will result in changes in delivered tidal volume
Increased airway resistance or decreased compliance will
decrease Vt
Decreased airway resistance and increased compliance will
increase VT
Factors affecting tidal voume during PCV
- Driving pressure increases, so does Vt
- AutoPEEP, decreases Vt
- Inspiratory time, increase Vt if Inspiratory flow is present
- compliance decreases, descrease Vt
- resistance, decrease Vt
- Pt effort, increases Vt
Driving pressure
difference between PIP and PEEP
Decreases in compliance will result in decreased volume during PCV, potentially causing
hypoventilation and resp acidosis
Mode of ventilation
simply an option for how breath delivery will be provided
Major modes of ventilation common to all vents include
- CMV (AC)
- SIMV
- CPAP with or without PSV
Both CMV and SIMV modes can be either
volume or pressure controlled
CMV can deliver
either a set tidal volume or a set inspiratory pressure, along with a set minimum respiratory rate
What is constant during CMV
Volume or the pressure depending on which control method was selected. Patient can trigger or initiate a breath above the set RR.
SIMV can provide
either pressure-controlled or volume controlled mandatory breaths while allowing spontaneous breaths that may be above or below the set control variable
Purpose of SIMV is to allow
the patient and vent to share the WOB. wean
CPAP
purely spontaneous mode of ventilation that applies greater than atmospheric pressure to the airways
CPAP is often used to evaluate
a pts spontaneous breathing capability prior to extubation and discontinuation of mech vent
APC
Adaptive Pressure control
- Sets desired Vt and the vent automatically adjusts the inspiratory pressure to the lowest level needed to deliver the set tidal volume
- Constant Vt with lowest PIP possible in the face of changes in compliance and resistance
Hybrid modes of ventilation
- APC
- ASV
- APRV
- TC
- PAV
- NAVA
ASV
Adaptive support ventilation
-Automatically selects Vt and RR for mandatory breaths and a Vt for spontaneous breaths based on compliance, resistance, and a target level of minute ventilation
APRV
Airway pressure release ventilation
- Pressure-controlled modication of SIMV utilizing a high and low pressure setting that allows a pt to breath spontaneously during either
- Can provide longer inspiratory times as compared to expiratory time (inverse ratio)
- Used to maintain alveolar recruitment and improve oxygenation in instances of significant oxygenation defect
TC
Tube compensation
-Form of pressure support designed specifically to overcome the additional WOB and resistance imposed by the artificial airway
PAV
Proportional Assist ventilation
- Mode of ventilation that provides support in proportion to the pts expected neuronal output of the resp center
- Vent monitors resp drive as reflected by the insp flow of the pt, then transformed into a volume level
NAVA
Neurally adjusted ventilatory assist
- Driven by the electrical activity of the diaphragm
- determines support level
- Improves synchrony between pt and vent, as the vent responds more quickly to the spontaneous efforts as generated by the diaphragm
An effective tidal volume ventilatres the lungs while
keeping plateau pressure (Pplat) below 30 cm H2O
In the case of using smaller tidal volumes,
RR may be set at 25 to 35 breaths per minute to maintain minute vent
With higher RR,
exhalation time is shortened and the potential for the development of auto-Peep is present
Set Fi02 to 100% when
during respiratory arrest or another situation when the pts oxygenation status is unknown or strongly suspected to be poor
Excessive levels of FiO2 are associated with negative effects such as
nitrogen washout, atelectasis, and oxygen toxicity
PEEP is used in vent pts to
prevent atelectasis associated with the immobility , body position, and impaired cough ability inhereted in mech vent
Higher levels of PEEP may be required in pts with serious oxygenation defects as seen with
ARDS and ALI, in order to maintain oxygenation, also useful in overcoming the breath triggering problems associated with auto PEEP
Pts with autoPEEP have additinal threshold
pressure that needs to be overcome in order to trigger inspiration, which can contribute to an increased WOB and asynchrony.
-Increasing the set PEEP to the level of autoPEEP reduces the amount of effort needed to trigger a breath, but it may also increase PIP and Pplat to unacceptable levels
Breath-triggering setting
is an example of a parameter that is not commonly part of the physician order but that must be adjusted appropriately to maximize the benefit of mech vent
During pressure trigger,
the vent measures a drop in system pressure that is associated with diaphragmatic effort and delivers a breath
Flow trigger
operates by the vent detecting a drop in base flow that is associated with spontaneous effort
Inspiratory flow pattern has an impact on factors such as
inspiratory time and gas distribution
During volume control ventilation,
a square or decelerating flow pattern is available for selection
Gas distribution is better with what waveform
decelerating, there also may be improvements in synchrony between pt and vent
During volume control vent, the high PIP alarm is not necessary? T/F
False
During positive control ventilation, which alarms can alert the clinician to changes in respiratory mechanics?
- High and Low Vt
- during pressure control, volume is variable and dependent on the pressure setting and respiratory system mechanics. Changes such as decreased compliance can be detected with low Vt alarms and improved compliance with a high Vt alarm.
A 60-kg PBW patient is placed on CPAP with pressure support. How should the apnea parameters be set?
- The RR should be set in accordance with Vt to provide Ve of 6 L per minute
- The FiO2 should be set to 100%
Ventilation strategies for obstructive lung disease include
using a Vt low enough to maintain a Pplat of less than 30 cm H2O, usually in the range of 6 mL/kg of PBW.
- RR is used to normalize the pH as much as possible, but high rates- air trapping, inadequate exp time= hypercapnia
- I time is set as low as possible to maximize exp time and reduce auto peep
- FiO2 is titrated to the lowest level possible to maintain acceptable oxygenation
Acceptable oxygenation in obstructive lung disease may be
- SpO2 greater than 88%
- PaO2 greater than 55 mm Hg
Settings that need to be ordered
Mode, Tidal volume or pressure set, rate, FiO2, PSV, and PEEP
Settings that are set to accompany ordered settings
Trigger, Insp flow or time, waveform, alarms/ limits, backup, ventilation, and humidification
Tidal volume ranges on vent/ rate
from 4-10ml/kg (spontaneous 5-7ml/kg),
keeping plateau less than 30cmH2O
rate- 12-20
If plateau is high
decrease Vt and increase RR
Minute ventilation ranges
5-10L/m or norm women:7, males:8,
80-100ml/kg (IBW)
Ve determined by
Vt x RR (always use returned Vt and total rate)
Oxygen Percentage
100% usual starting point, reduce to 40-50% as soon as possible.
- If you have ABG’s that indicate the pt does not need 100% then start at 40-50%
- Avoid going over 60%, add PEEP instead
PEEP
-Increases gas exchange, FRC- pops open alveoli and is the norm end of exhalation
-Raises mean airway pressure
-Improves oxygenation
-Standard 3-5 cmH2O (physiologic PEEP)
FiO2 0.6 or more consider using PEEP over 5
-Apply and reduce in small increments 2-3cmH2O
-Watch cardiovascular side effects
Triggering
Set as sensitive as possible
- Pressure: -0.5 to 2.0
- Flow: 2-3 below base flow (default)
Inspiratory flow, Ti, I:E
Ti about 1 sec (0.8-1.2) is normal
-at least 1:2 ratio
=shorter Ti= faster flow
Factors that affect Ti on conventional ventilators (7200/Star)
Vt, Flowrate, flow pattern
*Vt= Ti x flow
To shorten= Ti reduce Vt or increase flow
Remember reducing Vt changes
PaCO2
Inspiratory rise time
usually on default, 3seconds.
- used to control how fast the pressure rises to peak
- much like flow rate, need to meet or exceed pts demand
Flow patterns
Square, descending ramp, ascending ramp, and sine
-Square shortest
Less effects on the heart
Higher peak pressure
-Descending ramp
Longer Ti
better gas distribution improving oxygenation
Higher mean airway pressure causing more cardiac impairment
PSV (for SIMV and CPAP modes)
Minimal to overcome tubing resistance usually 6-8cmH2O
Increase PSV pressure to increase Vt
This mode is assisting the pts ventilation if set over the minimum
Only consider extubation if PSV down to minimum
Inspiratory Cycle Off
Used to help end a PSV breath
-swine wave
Either a percentage or a set flow rate
Makes it easier to end the breath so pt does not have to go to zero flow before the pressure is released
Inspiratory Pause
Used to improve gas distribution and improve oxygenation
- Increases mean airway pressure causing more cardiac impairment
- Temp for determining lung compliance and airway resistance
- Set for 0.5 seconds for three breaths
- average number
- remember to turn off if not automatic
- remember it can affect cardiac output
Normal lungs (Post Op, Neuro-muscular, CNS, Etc)
A/C or SIMV
- Vt volume type breaths 6-10 ml/kg IBW
- RR to obtain desired Minute Ventilation
- Insp Flow/Ti: 60 Lpm or Ti 1 sec (longer=improve O2)
- FiO2 should be below 0.50 but is very pt dependant
- PEEP start at 3-5
COPD and asthma (obstructive airway disease)
Noninvasive positive pressure ventilation to start
- IPAP start about 10-12
- EPAP start about 5
- BUR just in case they stop breathing, start about 8-10 for COPD
Obstructive airway disease, invasive management
A/C or SIMV (SIMV preferred)
- Vt volume type breaths 6ml/kg IBW
- RR 10-12 , so they can spontaneously breathe in between
- Insp flow/ Ti: 60-100LPM or Ti <1 sec, try to keep E time long to reduce airtrapping
- FiO2 should be lowest possible to maintain SpO2 in low 90s
- PEEP to match auto-PEEP
How do you measure lung disease
by FEV1
