21 Respiratory Failure and Assisted Ventilation Flashcards
what is the clinical definition of respiratory failure?
PaO2 < 8.0 kPa while breathing on air, or PaCO2> 6.5kPa
What ways can the body compensate for increased Oxygen demand?
lungs (increasing ventilation or V/Q mismatch)
blood (increasing Hb)
tissues (increasing cardiac output)
cells (change position of O2 dissociation curve)
What are the 2 types of respiratory failure?
1 - hypoxaemic respiratory failure
2 -hypercapnic respiratory failure
What is the physiological cause and effect of type 1 respiratory failure?
V/Q mismatch leads to a shunt as the body tries to compensate for a lack of oxygen
PaO2 < 8.0kPa with normal or a lil low PaCO2
(normal or high pH)
What is the physiological profile of type 2 respiratory failure?
PaCO2 > 6.5kPa
hypoxaemia is always present
pH and HCO3 are dependent on level of hypercapnia
decreased minute ventilation relative to demand
increased dead space ventilation
How might sepsis or a pulmonary embolus present?
hypotension with poor perfusion
also the case for cardiogenic airway obstruction
What might stridor suggest?
upper aiways obstruction
What might elevated jugular venous pressure suggest?
right ventricular pulmonary hypertension
What disease should not be ruled out by a normal CXR?
pulmonary embolism
what are the aims in treating respiratory failure?
primary - reverse and prevent hypoxaemia
secondary- control PaCO2 and respiratory acidosis
treatment of underlying disease
What is the goal with oxygen thearpy?
to prevent tissue hypoxia
venous SaO2 < 40%
arterial SaO2 < 70%
What is the FiO2 range usually used with nasal canula?
24 to 44% or 1 to 6 litres
What are the advantages of Nasal Cannula therapy?
safe, comfortable, well tolerated
eating, talking, and ambulation
What are the disadvantaged of Nasal Cannula therapy?
FiO2 varies with flow rate of breathing
extended use can break down skin and mucous membranes
tubing may be dislodged
What are the ranges of FiO2 delivered with a face mask?
40-60%
minimum flwo rate is 5L to ensure flushing of CO2 from the mask
What flow rates are given using a non re-breather mask?
80-90% (10 to 15L/min) to keep reservoir bag 2/3 full during inspiration and expiration
What are the advantages of non re-breather mask?
delivers the highest O2 concentration
one way valve allows client to inhale maximum O2 from reservoir bag
2 exhalation ports have flaps preventing room air from entering
What are the disadvantages of non re-breather masks
valve and flap must be functional
poorly tolerated by anxious or claustophobic patients
eating and drinking no no
What flow rates are delivered using a Venturi mask?
24-55%
What are the advantages of using a Venturi mask?
delivers precise oxygen conc.
no humidification required
good for those with chronic lung disease
What are the forms of mechanical ventilation?
non invasive with mask
invasive with endobronchial tube
What does mechanical ventilation do for hypercapnia?
increases alveolar ventilation and lowers PaCO2, correcting pH
rests fatigues muscles
What does MV do for hypoxaemia?
O2 therapy alone won’t correct hypoxaemia caused by shunt
What is the most common cause of shunt?
fluid filled or collapsed alveoli (pulmonary edema)
What is BiPAP?
Non-invasive bilateral positive airway pressure ventilation
provided by a nasal mask or nasal prongs, or a full face mask
What is the advantage of a BiPAP?
2 levels of positive pressure support
Ipap - inspiratory
Epap - expiratory (or CAP, PEEP)
In what settings should non-invasive measures be considered?
COPD exacerbation Cardiogenic pulmonary eddema obesity hypoventilation syndrome NMD to facilitate weaning frrom invasive ventilation
What does PEEP stand for?
Patient End Expiratory Pressure
What does CPAP stand for?
Continuous Positive Airway Pressure
What are the main uses of PEEP and CPAP?
treating/preventing atelactasis or alveoli collapse
improve gas exchange
treat hypoxemia
treat pulmonary oedema
