Respiratory Failure Flashcards
Oxygen cascade
Decrease in oxygen as it passes from the atmosphere into the body and into arterial circulation
Concentration of O2 in air
20.94%
Barometric pressure
101.3kPa
PO2 dry air at sea level
21.2kPa
Tracheal gas
PO2 after humidification
19.9kPa
Alveolar PO2 affected by
Hypo or hyper ventilation
Oxygen consumption
CO2 production
PAO2 equation
PAO2= dry barometric pressure x (FiO2-VO2/VA)
PAO2 equation 2
PiO2-(PaCO2/R)
Normal PaO2
13.6kPa
Shunting
An area of the lung that is perfused but not ventilated
Increases in disease
Oxygen Delivery
[Hb] x O2 saturation of Hb x 1.34 x 10 x CO
Signs of Resp Failure
Resp Compensation Increased Sympathetic tone End organ hypoxia Haemoglobin desaturation CO2 retention
Resp Compensation
Tachypnoea
Use of accessory muscles
nasal flaring
Intercostal or suprasternal recession
Increased Sympathetic Tone
Tachycardia
Hypertension
Sweating
End Organ Hypoxia
Altered mental status
Bradycardia
Hypotension
Haemoglobin desaturation
Cyanosis
CO2 retention
Flap
Bounding Pulse
Resp Failure
Syndrome where respiratory system fails in one of both of its gas exchange functions- oxygenation + CO2 elimination
Type 1 Resp Failure
Hypoxaemia only
PaO2 < 8kPa
Type 1 Resp Failure MOA
Damage to lung tissue
Prevents adequate oxygenation of blood (hypoxaemia)
Remaining lung tissue sufficient to excrete the CO2 produced
Type 1 Resp Failure examples
Pneumonia Obesity P. oedema Asthma/COPD pulmonary embolism pneumothorax
Type 2 Resp Failure
Hypoxaemia + Hypercapnia
PaO2<8kPa
PaCO2>6.5kPa
Type 2 Resp Failure MOA
Ventilatory Failure
Alveolar ventilation insufficient to excrete CO2 produced
Reduced ventilatory effort or inability to overcome increased resistance to ventilation
Type 2 Resp Failure examples
Type 1 with fatigue
hypoventilation
First line treatment
OXYGEN
Oxygen masks with nasal cannula
Face masks with reservoir bags
Venturi masks
Low flow masks
Nasal cannulas etc.
Deliver variable concentration depending on how the patient is breathing
Treatment sequence for Resp Failure
Oxygen
Pulse Oximetry
ABG
Pulse Oximetry
Started immediately
Pulse Oximetry saturation (SpO2) of 94% is a critical threshold- below this, small fall in PaO2 produces sharp fall in SpO2
ONLY TELLS US ABOUT OXYGENATION NOT VENTILATION
ABG
Used to keep fraction of inspired O2 to the minimum required to achieve adequate oxygenation
Used to evaluate pH changes + changes in PaCO2
If SpO2 >94%, PaO2 should be
> 10kPa
High levels O2
Dangerous + toxic
Produces free radicals
CO2 retention
10% of COPD patients- CO2 will go up if given oxygen
Ventilation
Not for hypoxia
Used for hypercapnia
Oxygen vs Ventilation
O2 for hypoxia
Ventilate in hypercapnia (hypoventilation)
COPD/Asthma
Bilateral hyper-expansion of the chest
