1. Respiratory Failure
Dr. Nick Weatherley Respiratory Registrar

2. Aims Control of breathing review Classification of respiratory failure
Causes of respiratory failure
Treatment options

3. Question 1
Annie is a 65 year old lady with a long history of heavy smoking. She feels breathless and wheezy.
You perform an arterial blood gas.

4. pH: 7. 31 (7. 35 - 7. 45) paO2: 7. 5 kPa (10 – 14) paCO2: 7. 2 kPa (4
pH: 7.31 ( ) paO2: 7.5 kPa (10 – 14) paCO2: 7.2 kPa (4.5 – 6.0) HCO3: 27 mmol/L (22 – 26)

5. What type of respiratory failure does this represent?
What is the cause of this event?
What treatment will you initiate?

6. Control of breathing

7. CO2 + H2O <--> HCO3- + H+

8. What is the partial pressure of oxygen at 4000 ft?
~ 16kPa (vs. 19.5kPa at ground level)
How long can you hold your breath underwater?
Try holding your breath with an O2 sats monitor – your spO2 won’t fall!

9. Classification of respiratory failure

10. Type 1 : low paO2, normal (or low) paCO2, normal or high A-a gradient
Limitation of ventilation, perfusion or diffusion
Type 2 : low paO2, high CO2, usually normal A-a gradient (acute or chronic)
Alveolar hypoventilation
CO2 enters alveoli, but not removed

11. CO2
CO2
CO2

12. Signs of hypercapnoea:
Bounding pulse
Flapping tremor
Confusion
Drowsiness
Reduced conciousness

13. Causes of respiratory failure
Failure to maintain patent airway (obstruction) – type 1 (if severe type 2)
Failure to ventilate alveoli – type 1 or 2
Failure to diffuse oxygen into blood – type 1
Perfusion – usually type 1

14. 1. Airflow Obstruction

16. Obstructive sleep apnoea
Relaxation of pharynx during sleep
Occlusion causes stimulation and wakening

18. 2. Alveolar hypoventilation

19. CO2
CO2
CO2

20. CO2 + H2O <--> HCO3- + H+

21. Radiopaedia

22. Obesity hypoventilation Chest wall deformity
Neuromuscular weakness
Myaesthenia gravis
Motor neurone disease
Guillan-Barre syndrome

23. Volume Time Inspiratory Reserve Volume (IRV) Vital Capacity (VC) Tidal
(TV)
Volume
Total
Lung
Capacity (TLC)
Expiratory
Reserve
Volume
(ERV)
Functional
Residual
Capacity
(FRC)
Residual
Volume
(RV)
Residual
Volume
(RV)
Time

24. 3. Diffusion limitation

25. Interstitial lung disease
Emphysema
Interstitial lung disease
IPF
Sarcoidosis
Pneumoconiosis etc.
Drug-induced lung disease (bleomycin, methotrexate)

26. O2
CO2 O2
CO2

27. 4. V/Q (mis)matching

29. Obstruction Hypo-ventilation Diffusion Perfusion
Asthma
COPD (emphysema)
IPF
Pulmonary embolism
COPD
Neuromuscular weakness
Other ILDs
Cardiac failure
OSA
Obesity (OHS)
Emphysema
Shunt (e.g. VSD)
Pneumonia
Chest wall deformity
Pulmonary hypertension
Reduced drive (e.g. narcotics)

30. Treatment Underlying cause
E.g. bronchodilators for COPD, antibiotics for pneumonia
Specific treatments for ventilation support

31. CPAP (Continuous positive airways pressure)
Acutely : Pulmonary oedema
Chronic: Obstructive sleep apnoea
Expanding into other areas

34. BIPAP (Bi-level positive airways pressure
Causes of type two respiratory failure e.g.
Acute: COPD exacerbation
Chronic: Motor neuron disease / OHS

35. Spontaneous
CPAP
Bipap
Pressure
Time

37. Question 1
Annie is a 65 year old lady with a long history of heavy smoking. She feels breathless and wheezy. You perform an arterial blood gas.

38. pH: 7. 31 (7. 35 - 7. 45) paO2: 7. 5 kPa (10 – 14) paCO2: 7. 2 kPa (4
pH: 7.31 ( ) paO2: 7.5 kPa (10 – 14) paCO2: 7.2 kPa (4.5 – 6.0) HCO3: 27 mmol/L (22 – 26)

39. What type of respiratory failure does this represent?
What is the cause of this event?
What treatment will you initiate?

40. pH: 7. 31 (7. 35 - 7. 45) paO2: 7. 5 kPa (10 – 14) paCO2: 7. 2 kPa (4
pH: 7.31 ( ) paO2: 7.5 kPa (10 – 14) paCO2: 7.2 kPa (4.5 – 6.0) HCO3: 27 mmol/L (22 – 26) Type 2 – note the low O2 and high CO2 The low pH suggests an acute event, though it may be an acute on chronic process given slightly high HCO3-

41. What type of respiratory failure does this represent?
What is the cause of this event?
What treatment will you initiate?

42. Obstruction Hypo-ventilation Diffusion Perfusion
Asthma
COPD (emphysema)
IPF
Pulmonary embolism
COPD
Neuromuscular weakness
Other ILDs
Cardiac failure
OSA
Obesity (OHS)
Emphysema
Shunt (e.g. VSD)
Pneumonia
Chest wall deformity
Pulmonary hypertension
Reduced drive (e.g. narcotics)
Almost certainly alveolar hypoventilation given type 2 RF
Probably COPD given history

43. What type of respiratory failure does this represent?
What is the cause of this event?
What treatment will you initiate?

44. Bronchodilators, steroids
Cautious oxygen to maintain spO %.
Consider BIPAP (NIV) or invasive ventilation

45. Summary
Break down causes into broad categories – all may cause type 1 RF
Alveolar hypoventilation may lead to type 2 RF
ABG crucial for determining type and chronicity