Advanced Ventilation Flashcards
List the complications of mechanical ventlation by ABCD
A:
- Airway malposition (hold ETT, teeth level, secure, CXR)
- Airway obstruction (from resistance/compliance, sputum, citcut)
- Airway trauma eg tracheal stenosis/trachomalacia (from cuff pressure)
B:
- Ventilator aquired pnemonia
- Dependence
- Acute lung injury
- Altered V/Q ratio (increased ventilation to areas with less perfusion, overstretching reducing perfuson)
- Oxygen toxicity
C:
Decreased CO due to:
- Reduced ventricular filling and venous return
- Increased PVR
- Reduced LV compliance
- Increased RV afterload
- Decreased MAP
- Flud retention/oedema (increased ADH, decreased RBF and GFR)
D:
- Increased ICP -> Decreased CPP
- Oedema, hypoxa, pain and anxiety
Other:
- Facial and pressure lesions
- Liver malfunction
- Gastric mucosal ischemia and ulcers
Lst the mechanisms of traumatic injury to the lungs from mechanical ventilaton
- Volutrauma
- Barotrauma
- Alectotrauma
- Biotrauma
Describe volutrauma
High tidal volumes causng overstretching and damage to the alvioli
Describe Barotrauma
Gas under pressure causes alviolar rupture.
Air is then forced into the interstititium of the adjacent broncho-vascular sheath and there is formation of extra alviolar gas.
Increased risk from:
- High PIP and low end expratory pressure
- Emphysema
- High Vt and high PEEP
- Aspiration of gastric acd
Describe alectotrauma
Sheer stress injury to the lung tissue from the repeated opening and closing of lung units.
May occur at times of low Vt +/- inadequate PEEP
*can increase cytokines in lung tissue, then entering the systemic circulation causing MODS.
Describe biotrauma
The release of inflammatory mediators due to injury from mechancal ventilaton (barotrauma/volutrauma/alectotrauma).
Epithelal and endothelal damage causes neutrphils to release cytokines and increase alviolar capillary permeabilty. Increased capillary permeability causes fluid build up between the alvioli and lung capillaries, impairing gas exchange. Also oedema and prurulent meterial build up inside alvioli, decreasing surface area for gas exchange to take place.
Can increase systemc cytokine levels and lead to SIRS and MODS.
Oxygen toxicity is also a form of biotrauma
Define restrictive vs obstructive lung disease
Restrictive
Poor lung compliance - restriction of lung expanson
(can’t breathe in)
Obstrictive
Increased resistance to airflow
(can’t breathe out)
What are examples of obstructive and restrictive lung disease?
Obstructive
Asthma (oedema, hypersecretion, bronchoconstriction)
Emphysema (loss of elastc recoil reduces radius of conducting airways)
Restrictive
Pulmonary fibrosis
ARDS
Fibrosis
Atelectasis
APO
Pneumothorax
Distended abdo
Ventilation management of restrictive lung disease
- Look at pt position
- Increase inspiratory time
- Reduce PIP’s
- Change to pressure control vent
- PEEP to recruit alvioli
- Permissive hypercapnoea
Ventilation management of restrictive lung disease
TBA
Define peak inspratory pressure?
(P peak / PIP)
The maximum pressure in the lung during inspiration
*change in peak pressure with normal Pplat indicates change in airway resistance
Define plateau pressure
End expiratory alviolar pressure - reflects pressure on the volume of gas in the lung at the end of inspiration.
It indicates the compliance of the lungs
It should be <30cmH2O.
>30mH20 can indicate hyperinflation
How do you perform a ‘breath hold’
Perform an ‘end inspiratory pause’ on the ventilator to prevent air moving in or out.
When can you have an obstructive and restrictive lung issue?
In asthma - bronchospasm and gas trapping (auto-PEEP)
Increased PIP/P.plateau difference and an increased P/Plateau
Interperate:
PIP - increased
PPlat - Unchanged or increased
What are some strategies for high PIP management?
- Lower tidal volumes
- Review RR and inspiratory times
- Pressure control ventilation
- Permissive hypercapnia
- Encourage spont breathing
- PEEP
What s intrinsic PEEP?
The amount of pressure in the lungs at the end of exhalation, preventing the lungs from reaching an elastc equilibrium point ‘gas trapping’.
It reflects hyperdynamic inflation.
ARDS = low levels (3-4cmH20)
Atsthma/COPD = high levels (10-15cmH20)
How is intrinsic PEEP measured?
Expiratory hold maneuver
Intrinsic PEEP = Total PEEP - Extrinsic PEEP
How is intrinsic PEEP managed to prevent dynamc hyperinflation?
- Increase expiratory time
- Reduce tidal volume to 6ml/kg
- Sedation and peralysis
- Increase flow rate
- PEEP set at 60-80% of auto-PEEP (augments distal airway emptying)
Determine appropriate ventilator settings for a paediatric patient
?
Mechanical ventilation strategies for Asthma
Aim:
- Prevent lung damage from barotrauma
- Prevent gas trapping and dynamic hyperinflation
- Increase expiratory time
Strategies:
- Slow RR
- Fast flow
- No unnecessary inspratory pauses
- Decrease Vt if Pplat is rising
- Permissive hypercapnia
- Aim MV approx 6L/min
Mechanical ventilation strategies for COPD
Similar to asthmatics but..
PEEP helpful to:
- Decrease WOB
- Stent collapsible airways
- Increase expiratory flow
Mechanical ventilation strategies for Pneumonia
Ventilate as per Restrictive LD
- Wet curcuit
- Monitor Pplat <35cm H20
- Vt 5/7mls/kg
- Pressure control
- Longer I tme
- Increased PEEP
- Encourage spont breaths
- Prone
- ?ECMO
Define permissve hypercapnia.
What are its advantages/disadvantages?
Deliberately low Vt (5ml/kg)/RR in order to decrease alviolar overdistention. Causes increased PaCO2.
- *Advantages:**
- Reduces the risk of barotrauma/volutrauma
- Increased PaCO2 enhances oxygen unloading at the tissue level
- Metabolc compesation can minimise adverse effects of acidosis
- *Disadvantages:**
- Acute rise in PaCO2 causes CNS and CVS depression
- Reduces the affinity of Hb to O2 at the lungs
- Rapid rise in PaCO2 leads to respiratory acidosis
Discuss the advantages of prone ventilaton
Aims to improve alviolar ventlation and decrease the degree of O2 shunt (improved V/Q match).
Improvement of 10mmHg withn 30 minutes helps to dstinguish responders.
ALVIOLAR VENTILATION:
- ARDS = heavier lungs, therefore will compress dorsal lung alvioli and decrease ventilation of alvioli.
- Lungs are cone shaped - oedema will collect and organs such as the heart wil compress alvioli on the dorsal lung when supine
VQ MISSMATCH:
Perfusion - better perfusion and larger vessels on dorsal side of lung regardless of supine or prone. Therefore, ventilation goes to alvioli with better perfusion.
Other physiological benefits:
Improved haemodynamics
- Improved R and L sided preload and reduced afterload
- Less compression of lung tissue making it easier for R ventricle to perfuse the lung tissue and decreases risk of ARDS induced R sided heart failure
Better secretion clearance
Increased compliance - decreased PEEP requirement - decreased risk of barotrauma
*the longer we prone the better, at least prone for 12 hours a day, may need increased sedaton, early awake proning shows benefit to patients - may decrease need to ventilate*
Dscuss the risks of prone ventilaton
- pressure injuries/facial oedema
- airway oclusion (due to positioning)
- loss of airway (ETT dislodgement)
- loss of/difficulty with lines/tubes (eg ECG’s (can move to back), CVC’s)
- increased intracranial pressure
- difficulty to perform procedures/reintubate
Outline the principals of weaning a patient from mechanical ventilation
- Can the pt ventilate?
- Can the pt oxyygenate?
- Does the patient have a gag reflex?
- Is there a resolution of the process necessitating intubation?
- Are the patient’s vital signs within normal limits?
- Was the patient a difficult intubation?
- *intubated patients who are often extubated in ED:
- Alcohol induced head injury (wth normal CT)
- Short term airway protection for procedure
- Overdose with short term CNS effects
- Palliation*
Demonstrate the safe extubation of a patient
