resp failure Flashcards
what is resp failure
syndrome of inadequate gas exchange due to dysfunction to 1+ of
[nervous system, resp muscle, pulmonary]
example of issue with [nervous system, resp muscle, pulmonary]
[nervous system= CNS
resp muscle=diaphragm
pulmonary=airway disease/circulation
risk factors to resp failure
chronic vs acute
chronic= COPD/CF
acute=infection/pancreatitis
what is ARDS
Acute respiratory distress syndrome
how to diagnose ARDS
Berlin definition
timing- within 1 week
chest imaging- bilateral opacities (lung more white)
origin of edema -not due to cardiac failure
oxygenation(P/F) (PaO2/FIO2) mmHg-
mild= 200-300
moderate= 100-200
severe= <100
Ventilation and perfusion across the lung- bottom on lung
bottom lung:
-ventilation (increased)
-alveoli smaller and more compliant
perfusion (increased)
-more recruitment
-less resistance
-high flow rate
what are the different zones of the lungs and ventilation
perfusion matching
Zone 1=apex
PA>Pa>Pv
Zone 2
Pa>PA>Pv
Zone 3=base
Pa>Pv>PA
PA=alveoli pressure
ventilation/perfusion
define compliance and elastance
compliance= tendency to distort under pressure
△v/△p
elastance = tendency to recoil to original volume
△P/△V
-think PEV
how to calculate minute ventilation (L/min) and what it is
gas entering and leaving lungs
tidal volume x breathing frequency (breaths/min)
how to calculate alveolar ventilation (L/min) and what it is
gas entering and leaving the alveoli
[tidal volume- dead space] x breathing frequency (breaths/min)
what is type 1/hypoxemic resp failure and cause
PaO2 <60
Failure of O2 exchange
-Increased shunt fraction (QS/QT )
- Due to alveolar flooding
- Hypoxemia refractory=no improvement to supplemental oxygen administration
Pulmonary HOE
-hypertension
-oedema
-embolism
what is type 2/hypercapnic resp failure and cause
(PaCO2 >45):
Failure to exchange or remove CO2
-Decreased alveolar minute ventilation (V A )
- Dead space ventilation
airway obstruction/weak muscles
what is type III resp failure (perioperative resp failure)
Increased atelectasis (incomplete lung inflation) due to low functional residual capacity
-can be hypoxaemia / hypercapnoea
-Prevention: anesthetic or operative technique
what is Type IV Respiratory Failure: Shock
pt- intubated and ventilated
during (Septic) shock
Ventilation increases thoracic pressure which affects the heart
Reduces LV afterload, Increased RV pre and after load
cause of ARDS pulmonary vs extra-pulmonary
pulmonary- trauma/aspiration
extra-pulmonary- pancreatitis/transfusion
both: INFECTION
what is the issue with lung injury in relation to gas exchange
Alveolar-capillary units become damaged and leaky,
distance for gas exchange increases,
reducing efficiency of gas exchange.
Reduced O2 available.
exacerbate by inflammatory response
resp failure- therapeutic intervention
- treat underlying disease
bronchodilators/steroids/Ab - resp support
- multi organ support
resp support in clinical management for ARDS from mild to severe
All:
-fluid management
-low volume ventilation
-increasing PEEP
Mod/Sev=
-prone positioning
-neuromuscular blockade
severe:
ECMO
what is ecmo
extracorporeal membrane oxygenation
ARDS pathogenesis
- Poor gas exchange
Inadequate oxygenation
Poor perfusion
Hypercapnoea
2.Infection-Sepsis
3.Inflammation
- Systemic effects
ventilation- cons
-Minute ventilation- PaCO2 control
-Alveolar recruitment (PEEP)
-V/Q mismatch -Ventilation without gas exchange vice-versa
-VENTILATOR INDUCED LUNG INJURY-> DRIVING PRESSURE
what is the Murray score and what each would mean
guiding escalation of therapy
0 = normal
<2.5 =Mild
>2.5 = Severe ARDS
3= ECMO
(averagescore on all 4 parameters:
P/F ratio, CXR, PEEP, Compliance
national ARDS approach
1.telephone/online referral
murray score 3+ or
pH<7.2
2.consultant case review
3. transfer imaging
4. advice
5. retrieval and transfer
6.ongoing management
ECMO issues
-time to access/consideration of referral
-obtaining access-subclavian/femoral
-clotting/bleeding
who to treat vs exclusion criteria
inclusion
-Murray 3+,
positive pressure ventilation not appropriate (eg. sig tracheal injury)
exclusion
-sign co-morbidity (dependency to ECMO
