Lecture 9 Flashcards
What is weaning?
Refers to the reduction in the amount of ventilatory support (eg. IMV to SIMV to PSV) - pump and O2 support (O2 can be delivered other ways besides MV - nasal prongs, mask etc)
When is the patient ready to be weaned?
- Cause of RF has been reversed
- Can spontaneously breathe
- Low PEEP and FiO2 requirements
- CV is stable
What are 3 methods of weaning?
- Step down assistance (SIMV - PSV - CPAP)
- T piece (easy transition between MV and non vent; can be off the entire day and put on vent at night)
- NIV post extubation
What are the factors that affect weaning?
Energy supply (reduced) - nutrition, O2 supply (cardiac dysfunction affecting Q, or pulmonary edema affecting O2 diffusion), O2 utilisation, stealing theory (high O2 use by resp mm's)
Energy demand (increased)
- reduced pump efficiency
- increased resp load (airway resistance, chest and lung compliance)
Neuromm competence
- reduced resp drive
- mm weakness
- impaired neuromm transmission - permanent or reversible (spinal cord injury vs GBS)
- psychogenic (pt has come to rely on intubation esp if previous extubation hasn’t been successful)
What percentage of pt’s fail to wean and what are prognostic factors?
20% fail to wean
Worse outcome likely with:
- age
- COPD dx
- prolonged MV
What’s the role of the physio in the weaning process?
Basically:
- reduce the load
- improve the pump
- optimise O2 movement
- prevent deconditioning
RRASP N
Respiratory mm mechanics Reassure Atelectasis Secretion clearance assistance Peripheral deconditioning minimization
NIV/Tracheostomy
What is a flail segment?
4 consecutive rib #s in 2 or more places
What is the effect of a sternal and rib fracture/flail segment on O2 movement, CO2 movement, secretion movement?
- Reduced CO2 movement (so increased PaCO2)
- increased load and reduced ability to cope with load
- reduced pump efficiency - Reduced O2 movement (so increased PaO2)
- generalized bc of pain driven smaller tidal volumes
- localized bc of lung contusion - Reduced secretion movement
- reduced cough effectiveness d/t pain
*acute changes also include pain and reduced movement of ribs (or paradoxical movement)
What is a pulmonary contusion
Bruising of the lung NOT confined to anatomical segmients; gets worse over 48 hrs; can get contusion without rib # if the ribs are springy
What are the effects of pulmonary contusion?
- Coagulation cascade
- blood clots/fibrin - means that part of the lung can’t participate in gas exchange and the lung gets stiffer - Reduced O2 movement
- d/t reduced SA for gas exchange - Reduced CO2 movement
- d/t reduced lung compliance (from coagulation cascade and edema) - therefore increased LOAD
What is the physio management for pt’s with pulmonary contusion/rib fractures?
- Pain management
- Positioning
- Mobilisation
What is ARDS?
- non cardiogenic pulmonary edema
- bilateral + diffuse alveolar damage
- follows from an acute insult
- d/t endothelial damage/inflammation and increased microvascular permeability
What are the KEY features for dx with ARDS?
- Acute hypoxaemic RF (PaO2 < 60 no responding to increasing levels of FiO2)
- Bilat + diffuse infiltrate on CXR
- No evidence of heart or lung disease, or fluid overload
What are the severity levels for ARDS - what are the
on?
Severe - <100 PaO2
Moderate 100-200 PaO2
Mild 200-300 PaO2
*for ALL the above - PEEP > 5cmH2O
(Normal PaO2 = 450)
What are the 3 phases of ARDS? Explain them
- Exudative phase
> Damage to alveolar-capillary layer
- increased permeability
- damaged pulmonary capillary endothelium
- remember this is NON CARDIOGENIC
> Inflammatory infiltrates
> Surfactant dysfunction - changes in composition of surfactant predisposes to further collapse - Proliferative+fibrotic phase
- thickening (endothelium, interstitium, epithelium)
- interstitial fibrosis (affect lung compliance)
- vascular occlusion
- emphysematous type changes
