Starting Mechanical Ventilation Flashcards
When to move from CPAP to MV
When on CPAP move to mechanical ventilation when
SaO2< 85% at an
FiO2< 40-70%
and PEEP of 5-10 cmH2O
Indications for Mechanical Ventilation in Adults
ASIA
Apnea
Severe Refractory Hypoxemia
Impending ventilatory Failure
Acute Ventilatory Failure
Indications for Mechanical Ventilation in Adults
Severe Refractory Hypoxemia
A-a Gradient (mmHg)
- Normal
- 25-65 On FiO2 1.0
- 5-20 On Room Air
- Critical
- >350 On FiO2 1.0
PF Ratio
- Normal
- 350-450
- Critical
- <200
PaO2/PAO2
- Normal
- 0.75-0.85
- Critical
- <0.15
Indications for Mechanical Ventilation in Adults
Impending Respiratory Failure
Assess WOB and other relevant parameters
MIP (cmH2O)
VC (mL/kg)
Vt (mL/kg)
RR (bpm)
Vd/Vt
MIP (cmH2O)
Normal -80 to -100
Critical 0 to -20
VC (mL/kg)
Normal 65-75
Critical <10
Vt (mL/kg)
Normal 4-8
Critical <4
RR (bpm)
Normal 12-20
Critical >35
Vd/Vt
Normal 0.25-0.4
Critical >0,6
Indications for Mechanical Ventilation in Adults
Acute Ventilatory Failure
PaCO2> 55 mmHg and a pH >7.25
Indications for Mechanical Ventilation in Adults
- Apnea
- Respiratory Failure
- pH < 7.20
- PaO2< 50 mmHg
- PaCO2>65 mmHg
- We will seldom wait for this clinically and instead initiated mechanical ventilation sooner
- Pulmonary Disease
- Neurological and Neuromuscular
- Congenital Abnormalities
- Post Surgery
Classic Indications for Mechanical Ventilation in Infants
- Classic indications of mechanical ventilations in infants with respiratory failure or persistent apnea
- Respiratory Failure
- Arterial blood pH <7.20
- PaCO2 of 60 mmHg
- Oxygen saturation of 85% at oxygen concentration of 40-70% and CPAP of 5-10 cmH2O
Extremely low body weight infants and mechanical ventilation
In extremely low body weight (ELBW) infants (weighing <1000g) intubation and positive pressure ventilation (PPV) may be necessary immediately after birth
Infants with Mechanical Ventilation just admitted to NICU
- Generally once the infant is stabilized in the NICU a pressure limited ventilator using a sinusoidal flow pattern is used. The settings that are commonly used are the following
- If a longer Ti is required before surfactant administration, it should be lowered to 0.3 seconds after surfactant is administered
Infants Mechanical Ventilator Modes
Ventilator modes such as synchronized intermittent mandatory ventilation (SIMV) or assist control modes can reduce WOB and blood pressure fluctuations if the sensitivities are properly set
Modes that maintain a consistent Vt can reduce risk of volutrauma (damage caused by overdistention by mechanical ventilation set for excessively high Vt) particularly after the administration of surfactant
High frequency ventilation may be indicated in infants who cannot be ventilated with the usually effective FiO2 levels, ventilator pressures, and rates
Sponataneous Parameters in Adults
RR (bpm) 12-20
Vt (ml/kg) 4-8
VC (ml/kg) 65-75
Resistance (cmH20/L/sec) 0.6-2.4
Compliance (mL/cmH2) 50-170
Sponataneous Parameters in Neonates
RR (bpm) 30-60
Vt (ml/kg) 5-7
VC (ml/kg) 35
Resistance (cmH20/L/sec) 25-50
Compliance (mL/cmH2) 1-2
What is different between neonates and pediatrics
- Faster RR
- Smaller VC
- Much, much higher airway resistance
- Think of how small the diameter is and this will increase resistance to the 4th power
- Much, much lower compliance
- This is normal
- Preemies will have even worse compliance as they develop RDS
GOALS OF MECHANICAL VENTILATION
Improve oxygenation to meet the metabolic demands of the body
Eliminate CO2
Reduce work of breathing
INITIAL VENTILATOR SETTINGS
Infant
- Peak Inspiratory Pressure should be set to 15-25 cmH2O
- PIP Limit should be set to 30
- Tidal Volume should be set between 3-5 ml/kg
- What about deadspace
- Ex. Flow transducers, ETCO2
- What about deadspace
- Positive End Expiratory Pressure (PEEP) should be set to 3-6 cmH2O
- A proper set PEEP is used to prevent further alveolar collapse
- Increases typically made in increments of 1-2 cmH2O. PEEP may be 8 before alternative modes trialled.
- Respiratory Rate should be set 20-50
- Start at 50
- Used to treat hypercapnia
- Inspiratory time should be set to 0.3-0.4
- Start at 0.3
- Adjust to reach equilibrium
- Mode
- Begin with Pressure Control Volume Targeted Ventilation
- If leak is > 40%
- Consider a larger ETT, extubation to NIPPVS, or A/C PC ventilation
- The trend towards using NeoPuff and/or setting up on ventilator sooner. Goal is to minimize inadvertent inverse ratio and high pressures.
VENTILATORY CHANGE PARAMETERS
*These goals do not apply when CHD or PPHN is present
VLBW (28-40 Weeks)
Goal PaCO2-Emphasize point that regardless of reference it is a permissive hypercapnia strategy overall
- pH
- ≥ 7.25
- PaCO2 (mmHg)
- 45-55
- PaO2 (mmHg)
- 50-70
- HCO3- mmol/L
- 18-20
- SpO2
- 85-92
VENTILATORY CHANGE PARAMETERS
*These goals do not apply when CHD or PPHN is present
ELBW (<28 Weeks)
Goal PaCO2-Emphasize point that regardless of reference it is a permissive hypercapnia strategy overall
- pH
- ≥ 7.25
- PaCO2 (mmHg)
- 45-55
- PaO2 (mmHg)
- 45-65
- HCO3- mmol/L
- 15-18
- SpO2
- 85-92
Initial Setting of Peds Vent
Tidal Volume
6-8 mL/kg
May be as low as 4mL/kg
May be as high as 10 mL/kg
Will depend upon the size of the pediatric population
For testing I say that goal range of VT is same as adults 6-10 ml/kg normally, 5-7 for protective=this makes whole table similar/same as adults!
Remind that if a small pediatrics (e.g. 10 kg) then think closer to neonatal strategies
Initial Setting of Peds Vent
PEEP
Start at 4-5 cmH2O
Aim for optimal PEEP
Increase typically made in increments of 1-2 cmH2O
Watch for CV compromise with increasing PEEP
Optimal PEEP is that which achieves the best lung compliance and oxygenation with the fewest CV side effects
Initial Setting of Peds Vent
Circuit
<25 kg for a neonate
>25 kg Adult
Neo circuit is always heated
Adult circuit will depend upon the size of the pediatric
Initial Setting of Peds Vent
Inspiratory Time
Smaller child 1.0 seconds
Longer for a larger child
Initial Ventilatory Settings for Toddler
- RR (breath/min)
- 20-35
- Vt (ml/kg)
- 5-8
- Inspiratory Time
- 0.6-0.7
- PEEP
- 5
Initial Ventilatory Settings for Small Child
- RR (breath/min)
- 20-30
- Vt (ml/kg)
- 6-9
- Inspiratory Time
- 0.7-0.8
- PEEP
- 5
Initial Ventilatory Settings for Child
- RR (breath/min)
- 18-25
- Vt (ml/kg)
- 7-10
- Inspiratory Time
- 0.8-1
- PEEP
- 5
Initial Ventilatory Settings for Adolescence
- RR (breath/min)
- 12-20
- Vt (ml/kg)
- 7-10
- Inspiratory Time
- 1-1.2
- PEEP
- 5
PEDIATRIC ABG
- pH
- 7.35-7.45
- PaCO2(mmHg)
- 35-45
- PaO2(mmHg)
- 80-100
- *May be less on capillary gas
- HCO3- (mmol/L)
- 22-26
- SpO2
- 95-100%
- Goal is just higher than 90%
Initial Ventilatory Settings for Adult
Tidal Volume
6-10 mL/kg
May be as high as 10ml/kg for patients with neuromuscular and post op patients
Lung protective strategies will be 4-6 ml/kg
Initial Ventilatory Settings for Adult
RR
12-16
Higher rates run the risk of air trapping
Initial Ventilatory Settings for Adult
Inspiratory Time
0.8-1.2 seconds
Targeting an I:E of 1:2 or lower
Initial Ventilatory Settings for Adult
PEEP
Typically start at 5 cmH20
Aim for an optimal PEEP
Increase typically made in increments of 2-3 cmH2O
Watch for CV compromise
Contraindications to PEEP- Increased ICP, untreated pneumothorax, hypotension*
Initial Ventilatory Settings for Adult
Minute Ventilation
~100 mL/kg to start
80-100ml/kg IBW
Can also use ♂- 4 x BSA
♀-3.5 X BSA
Febrile patient will require a higher MV
Will be adjusted based on PaCO2
PEEP and Hemodynamics
- The beneficial effects of PEEP may be outweighed by the effects that PEEP has on hemodynamics.
- PEEP will result in a reduction in venous return due to the elevated intrathoracic pressure, and by an increased right ventricular afterload that is secondary to the rise of pulmonary vascular resistance.
- PEEP redistributes cardiac output in favor of brain, heart, adrenals and intestines, whereas the perfusion of stomach, pancreas and thyroid is diminished
- Reduction of hepatic artery flow, at higher levels of PEEP, may jeopardize liver tissue oxygenation.
- Under clinical conditions, individual differences regarding pre-existing cardiopulmonary and peripheral-vascular diseases may modify the PEEP-induced hemodynamic alterations in a wide range out of proportion to the fall of cardiac output.
Adult ABG
pH- 7.35-7.45
PaCO2: 35-45
PaO2: 80-100 (goal 60-100)
HCO3: 22-26
SaO2: 95-100% (Goal >90%)
TBI Protocol
Head injury-PaO2 80-120 (CHR TBI protocol), PaCO2 on low side normal
TIME CONSTANTS
Time constants represent how fast pressures equilibrate between the circuit and the alveoli
It represents the maximal rate at which exhalation occurs
Time constant is calculated through multiplying compliance and resistance
The time constant related to inspiratory filling and expiratory emptying of the lungs
Mouth pressure or proximal airway pressure will equilibrate with alveolar pressure in 3-5 time constants (this will be ~0.33 seconds in a newborn and 0.25 seconds in adults)
TIME CONSTANTS VALUES
1stTime Constant- 63% of the volume is delivered or exhaled
2ndTime Constant- 86.5 % of the volume is delivered or exhaled
3rdTime Constant- 95% of the volume is delivered or exhaled
4th Time Constant- 98.2% of the volume is delivered or exhaled
5th Time Constant- 99.3% of the volume is delivered or exhaled
Time Constants and Severe Respiratory Distress
In babies with severe respiratory distress and decreased lung compliance one time constant can equal 0.05 seconds
This means that pressure equilibrium occurs in 0.15-0.20 seconds which is the minimum inspiratory time required to ensure complete delivery of tidal volume
Time Constants and MAS
When airway resistance is high such as in MAS the time constant will become longer meaning we have to use a longer inspiratory time, lower inspiratory flow, and longer exhalation times to ventilate these infants
Time Constants and Respiratory System Mechanics
Monitoring respiratory system mechanics to derive time constants can assist in properly adjusting adequate inspiratory time and expiratory time during ventilation
The time component is important when using rapid rates to allow for adequate exhalation without developing breath stacking and automatic positive end expiratory pressure (auto PEEP) and to minimize lung damage
PRESSURE CONTROL VOLUME REGULATED
- You will set on the ventilator the following parameters
- Tidal Volume
- Rate
- Inspiratory Time
- PEEP
- In PRVC rememeber that Pplat and PIP will be the same
PRESSURE CONTROL VOLUME REGULATED
AS COMPLIANCE DECREASES
- Because your tidal volume will stay the same you will need to have an increase in PIP and Pplat
- There will also be an overall increase in Pmean
- Will change the time constant
- Your minute ventilation will not change because you control both rate and tidal volume
- As compliance decreases your Tidyanwill decrease Tistatic will increase and flow will increase
- The Titotal will not change which means that your Te and I:E will not change
PRESSURE CONTROL VOLUME REGULATED
AS RESISTANCE INCREASES
Your pressures will remain the same it will be the speed of the flow that will be changing due to the change in the airway diameter Because it is flow is changing it will be the Ti dynamic and Ti static that will change
As resistance increases Tidyn will increase and Tistatic will decrease (Titotal will not change)
Peak flow will be directly proportional to resistance but overall flow will not change (and we can not measure)
PRESSURE CONTROL VOLUME REGULATED
AS TI DECREASES
- Your Ti total will decreased and it might be decreased to the extent that we do not reach equilibrium before exhalation starts.
- Because Ti total is shorter it means that Te is longer. So I:E will decrease
- As Ti is shorter there will be a higher pressure (PIP) needed in order to deliver the set tidal volume
- However because of the time that we are delivering that pressure there will be an overall decrease in Pmean
- Note that there is a larger change in PIP (increase) than there is in Pmean (decrease)
- In the mode of PRVC if we decrease Ti resulting in a truncation of inspiratory flow what is the affect on peak pressure and the plateu pressure in the lungsPeak pressures will go up but plateau pressures (in the lungs) will not change
- Ventilator Pplat will go up as it will be the same as PIP in PRVC
PRESSURE CONTROL
You will set on the ventilator the
PC Absolute/PIP
Rate
Ti
PEEP
PRESSURE CONTROL
COMPLIANCE INCREASES
- Tidal volume will increase as we can increase the volume delivered at a certain pressure
- Because our tidal volume is increasing our minute ventilation will increase as well
- Ti dyn will increase and Ti pause will decrease
- Because Ti dyn will increase flow will decrease also your Pmean will increase with an increased Ti dyn
- You Ti total will not change (so I:E will not change)
PRESSURE CONTROL
RESISTANCE INCREASES
The only thing that will change is that your Ti dyn will get longer
Remember as resistance increase your flow will decrease making a longer Ti dyn and a short Ti static
MANAGING THE VENTILATOR IN INFANTS
-
Prevent Hypoxia (SpO2 88-92)
- Manipulate the FiO2
- If FiO2 is >0.60 increase the PEEP
- Manipulate the mean airway pressure
- Do this through manipulation of Ti (increase in Ti will increase MAP), I:E, or PEEP
- Manipulate the FiO2
-
Prevent Lung Injury
- Limit FiO2 with PEEP
- Wean FiO2 if possible
- Limit Pplat (<30 cmH2O)
-
Prevent Acidosis
- Increase rate in order to decrease WOB
- Increase rate to keep pH above 7.25
- Cause of acidosis
- Hypoxemia, hypoxemia, hypoxemia
WEANIGN INFANTS FROM VENTILATOR
Try decreasing rate and watch WOB (SBT)
Wean FiO2 (decrease when SpO2 >93%)
Wean PEEP when FiO2 is below 0.4 – 0.5
We don’t wean aggressively on babies that are losing weight or having huge apneic periods
The keys to the management of infants with RDS
- To prevent hypoxemia
- Allow for normal tissue metabolism
- Optimize surfactant production
- Prevent R to L shunting
- Optimize fluid management
- Balance between avoiding hypovolemia and shock and on the other side also trying to avoids edema
- Reduce Metabolic Demands
- Prevent worsening atelectasis and pulmonary edema
- Minimize oxidant lung injury
- Minimize lung injury cause by mechanical ventilation
Mechanical Ventilation and CHD
Rule out you differential diagnosis before you CHD cause they are very rare
PGE you have to intubate because a side effect of PGE is associated with central apneas
Mechanical Ventilation and Non-Cyanotic CHD
Minimal ventilator parameters to decrease WOB if needed.
Mechanical Ventilation and Cyanotic CHD
Minimal ventilator parameters to decrease WOB if needed with minimal FiO2 as SpO2 is not improved and due to the danger of closing the PDA.
Mechanical Ventilation and BPD with a PDA
Normally a PDA is not a big problem, but when there is a left to right shunt the problem is that this leads to chronic pulmonary edema and it is this edema which is why babies are oxygen dependent
This leads to BPD and when you touch the baby and they cry it will create pressure in their lungs which will increase pressures creating a right to left shunt, which will decrease saturations as the deoxygenated blood being dumped into the aorta and being delivered to the body.
So as a RT you will want to increase FiO2 but you should not touch the FiO2 because as soon as the baby relaxes it will return to being a left to right shunt and we will have an increase in saturations again.
If there is major fluctuations in saturations will be used to determine whether there is a problematic PDA
Chronic Lung Disease Pathogenesis
Prematurity-Respirtory Failure Mechanical Ventilation
-
Excessive tidal volume and decreased lung compliance
- Volutrauma
-
Increase inspired oxygen, defifcent antioxidant system, nutritional defiecnies
- Oxygen toxcicty
- Pre/postnatal infections, PMN activation
- inflammatory mediators, elestase/proteinase, inhibitor imbalance
-
PDA, excessive fluid intake
- increase pulmonary edema and lung edema
All will lead to acute lung injury inflammatory response
Acute Lung Injury Inflammatory Response
-
Airway Damage
- Metaplasia, smooth muscle hypertrophy, increase mucus secretiosn
- Airway obstruction and emphysema atelectasis
-
Vascular Injury
- Increased permeability, smooth muscle hypertrophy, decreased vascularization
- Pulmonary edema and hypertension
-
Intersitial Damage
- Increased fibronectin and elastase, decreased alveolar septation
- Fibrosis and decreased number of alveoli-capillaries
All lead to Chronic Lung Disease
BPD AND OXYGENATION
Supplemental oxygen is the main therapy for infants with BPD but the appropriate target remains controversial
Oxygen saturations are accepted at 85-90% after preterm birth
Keep in mind though that patients with severe BPD usually are <36 weeks which is past the time when ROP is a major concern
For BPD, growth failure, respiratory exacerbations and PPHN however we accept saturations of 92-95%
BPD VENTILATOR STRATEGIES
EARLY PREVENTION
- Strategies to prevent acute lung injury
- Low Vt (5-8 ml.kg)
- Short inspiratory time
- Increase PEEP at needed lung recruitment without overdistension or reflection at high peak airway pressure
- Achieve lower FiO2
- Goals for Gas Exchange
- Adjust FiO2 to target lower O2 saturations (85-90%)
- Permissive hypercapnia
BPD VENTILATOR STRATEGIES
LATE (EASTABLISHED BPD)
- Marked regional heterogenely
- Larger Vt (10-12 ml/kg)
- Longer inspiratory time (>/= 0.6 sec)
- Airway Obstruction
- Slower rates allow for better emptying especially with larger Vt
- Complex roles for PEEP with dynamic airway collapse
- Interactive effects of vent strategies
- Changes in RR, Vt, inspiratory and expiratory time, pressure support are highly interdependent
- Overdistention can increase agitation and paradoxically worsen ventilation
- Permissive hypercapnia to facilitate settings
PDA
Right to left shunting
Chronic pulmonary edema
Incidence of greater hypoxemia and possibly metabolic acidosis
If failure to spontaneously close or with drug treatment (indomethacin), may require surgical closure.
Note to clinicians: be wary of increasing FiO2 to compensate as it will not improve SpO2 but may expose patient to toxically high FiO2
Reasons to Mechanical Ventilation in Neonates
- Apnea-Only absolte indication
Acute Ventilatory Failure
Impending Ventilatory Failure
Severe Refractory Hypoxemia
Acute Ventilatory Failure in Neonates
Type 2 Respiratory Failure (hypercapnic)
pH<7.25 despite use of CPAP and supplemental oxygen of FiO2 >0.60
Impending Ventilatory Failure
When signs and symptoms of respiratory distress are exhibited, non-invasive CPAP may be trialled prior to intubating and mechanically ventilating (assuming pH > 7.25)
Severe Refractory Hypoxemia in Neonates
Hypoxemic respiratory failure (PaO2<50 mmHg) despite the use of CPAP and supplemental oxygen (FiO2³0.60)
Associated with:
- Any kinds of shunt
- Intrapulmonary shunting
- Due to MAS, sepsis, pneumonia (not effective opening up the lungs
- Intrapulmonary shunting
- Intracardiac shunting
- PDA, PFO
Congenital Abnormalities that require Ventilation
- Lung hypoplasia
- CDH
- Tracheal anomalies
- Cardiac defects
Surfactant and Mechanical Ventilation
The need for surfactant require intubation and ventilation
After meconium aspiration
Surfactant deficiency associated with prematurity
The neonate may be intubated to administer surfactant but then, depending on the gestational age and respiratory status, may be extubated to CPAP/SiPAP
Signs & Symptoms of Respiratory Distress in the Neonate
- Retractions
- Intercostal, suprasternal, substernal
- Grunting
- Nasal flaring
- Increasing oxygen requirements
- Cyanosis
- Tachypnea
- RR > 60 bpm
Silverman Index
Similar to the ones on the adult but more evident in kids
The higher the silverman score the high the distress
Score 10=Severe respirtory distress
Score >/=7 Impending respirtroy failure
Score 0 No respirtory distress
Pediatrics Indication for Ventilation
- Apnea
- Acute ventilatory failure- Hypercapnia with a pH < 7.25
- Impending ventilatory failure- Clinical signs: Tachypnea, substernal and intercostal retractions, expiratory grunting, nasal flaring, cyanosis, head bobbing
- Severe refractory hypoxemia
What Influences Mean Airway Pressure
PIP
PEEP
I:E Ratio
Flow
Why Does PEEP help oxygenation
We tend to spend more time in exhalation than inspiration which is why PEEP helps improve oxygenation
How will changing from a square waveform to a decelerating waveform influence MAP
Decrease MAP
Tidal Volume Goals for Adults
6-8 ml/kg
May be as high as 10ml/kg for neuromuscular and post op pts.
Lung protective 4-6 ml/kg.
RR Goals for Adults
12-16 bpm
Higher rate run the risk of air trapping
Inspiratory Time Goals for Adults
0.8-1.2 s