FINAL Flashcards
Severe Resp Failure=
Low pH, lower than 7.25 and PaCO2 above 55
obtunded
Sort of out of it
combative
fighting it
diaphoretic
sweaty and cold
AA gradient when to intubate?
3-30
Hypoxic Resp Failure:
PaO2 < 60 (PEEP, CPAP, EPAP)
Hypercapnic (vent. failure):
PaCO2 > 50 (consider bipap or intubate)
Shunt
purfusion with no ventilation, alveoli collapse
-Does not respond to oxygen
Deadspace
Ventilation without perfusion
-Low SpO2 or PaO2 that responds to O2
Obstructed lung diseases
COPD, Asthma, Bronchiectasis, bronchitis
-they are not getting oxygen ( 70-80%pts)
Restricted lung diseases
Small lungs, stiff lungs. can lead to obstructed.
-All other lung disease
Pt hypoventilating A/a gradient will
come out normal
Chronic Resp. Failure
Combination of hypoxic and vent. failure
-Increase in PaCO2 lead to kidneys retaining bicarbonate to normalize the pH
=fully compensated resp acidosis
Cardiovascular Complication of mech vent
Reduced venous return, reduced cardiac output, hypotension
Neuromuscular of mech vent
Sleep deprivation, Increased intracranial pressure, critical illness weekness
Ventilator monitors and adjusts airway pressure needed to deliver target volume
PRVC
Respiratory failure is divided into two major categories, each of which includes many different diseases and conditions that can lead to respiratory failure.
- Type 1 Respiratory failure: Hypoxemic Resp Failure
- Type II Respiratory failure: Hypercapnic Resp Failure
Hypoxemic Resp Failure
involves inadequate blood oxygenation and low to normal levels of carbon dioxide. (oxygenation failure)
Hypercapnic Resp Failure
involves inadequate blood oxygenation with high levels of carbon dioxide. This condition is also referred to as ventilatory failure.
These four broad conditions are considered the primary indicators for mechanical ventilation:
- Apnea
- Acute ventilatory failure
- Impending ventilatory failure
- Severe oxygenation defect
Various VAP prevention strategies include:
- Elevating the head of the bed
- Frequent oral care
- Careful management of the airway cuff pressure
- Limiting circuit changes to an as-needed basis
- Use of specially designed antimicrobial endotracheal tubes
Control Variable
which is pressure or volume
- is the designated independent variable between pressure, volume, and flow as they relate to the equation of motion.
- If volume is the designated control variable, the shape of the pressure waveform is dependent on the volume setting and the resistance and compliance of the respiratory system. Volume is constant and pressure varies.
Breath Sequence
which is a pattern of mandatory or spontaneous breaths
targeting scheme
Which is the feedback control scheme used to shape the breath and determine the breathing sequence
Breath sequence can be subdivided into three categories:
- Continuous mandatory ventilation (CMV), where all breaths are mandatory
- Intermittent mandatory ventilation (IMV), where breaths can be mandatory or spontaneous
- Continuous spontaneous ventilation (CSV), where all breaths are spontaneous
Ms. Garcia’s illness has improved dramatically over the past few days and her doctor wants to determine how she may breathe if the ventilator is discontinued. Which mode of ventilation is most appropriate for the given situation?
PSV
-PSV is a purely spontaneous mode that will allow evaluation of the patient’s tidal volume and respiratory rate.
PRVC
Adaptive Pressure Control; is a dynamic mode of ventilation that allows delivery of a set tidal volume at the lowest possible inspiratory pressure. APC is one of the modes of mechanical ventilation that goes by varying names depending on the manufacturer, but the underlying mechanics remain the same.
-A desired tidal volume is set; the ventilator monitors and adjusts the airway pressure needed to deliver the target volume.
APRV
(BiVent) Airway pressure release ventilation; is a time-cycled, pressure-controlled modification of SIMV that allows the patient to breathe spontaneously throughout the set ventilator pressures. APRV allows the clinician to set two levels of pressure and the time in which the ventilator provides the two pressures.
- PHigh/ low
- Thigh/low
The high pressure, Phigh, influences
the degree of lung inflation and the time spent at this pressure is Thigh.
The low pressure, P Low, influences
The level and duration of lung deflation is determined by the low-pressure setting, Plow, and the release time, termed Tlow.
During PRVC ventilation, pressure is the target variable. T/F
FALSE.
-a desired tidal volume is set and the ventilator monitors and adjusts the airway pressure needed to deliver the target volume.
Cut offs NIF Vc Vt Ve RSBI RR
NIF -20 Vc 10ml/kg Vt 5ml/kg Ve less than 5 or greater than 10 RSBI 105 RR 35bpm
Modes
CMV (A/C), SIMV, CPAP, PCV (breath type), PSV (most common)
Breath sequence
Continuous Mandatory Ventilation (CMV)- all mandatory,
Intermittent Mandatory Vent. (IMV)- Both,
Continuous Spontaneous Vent (CSV)- all spontaneous
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
PIP
Peak inspiratory Pressure, highest level of pressure applied to lungs during inhalation
Factors that impact PIP during VC ventilation
-Peak inspiratory flow setting
-Inspiratory flow pattern
-Auto-PEEP
-Tidal Volume
-Resistance
-Compliance
A higher set peak inspiratory flow results in higher PIP
–The decelerating flow pattern is associated with lower PIP
driving pressure
difference between PIP and PEEP
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
Gas distribution is better with what waveform
decelerating, there also may be improvements in synchrony between pt and vent
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.
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
triggering settings
Set as sensitive as possible
- Pressure: -0.5 to 2.0
- Flow: 2-3 below base flow (default)
Vt equation
Ti x flow
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
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) vent settings
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
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
FEV1
BE
Base Excess: represents the amount of an acid required to return pH to normal levels
Norm ranges -2 to 2
BD
Base Deficit represents the amount of a base required to return pH to normal levels.
SaO2
is a measure of the percentage of hemoglobin saturated with oxygen in arterial blood; it is a more accurate depiction of oxygenation than the noninvasive Spo2 provided through pulse oximetry.
Flow Volume Loop
help identify asynchrony
-also be used to evaluate the degree of airway obstruction and the response to a bronchodilator medication.
One of the main causes of oxygenation defects is
V/Q mismatch
Factors that contribute to Paw (MAP) during mech. ventilation, including
PIP
PEEP
I:E ratio
Flow
With a current Paco2 of 56 mm Hg and a RR of 16 bpm, we are close to the patient’s normal value, but the pH remains acidic. In an attempt to correct it, we can estimate what the Paco2 will be if we increase the RR to 18 bpm.
Current PaCO2 x Set RR = changed RR x X
56 x 16 = 18 x X
896 = 18x
x = 49.7
While a Pao2 of 110 mm Hg is great by most standards, remember that the patient is on 100% Fio2. We need to wean Fio2 as soon as possible, but we do not want the patient’s oxygenation to fall below acceptable standards. We can predict how much Fio2 is needed to obtain our minimum standard of a Pao2 of 55 mmHg.
Current PaO2/ Current FiO2 = Desired PaO2/ x
110/ 100% = 55/ x
110 x 55/ 100 = x
x = 60.5 or 60% FiO2
Alveolar Ventilation factor of
RR, Vt, Deadspace (Vd/Vt)
Desired RR
Known PaCO2 x known RR/ Desired PaCO2
Desired Vt
Known PaCO2 x known Vt/ Desired PaCO
Effects of PEEP
Increases FRC by recruiting alveoli increases lung compliance improves gas distribution improves oxygenation by reducing shunting
influction point seen on
pressure. vol loop
beaking= overdistention
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
Airway resistance equation
Peak - Plateau
Ranges for Airway Resistance
norm 0-10cmH2O/L/s
moderate 11-15
severe >15