|Acute Severe Asthma
|Exacerbation of COPD
|Cardiogenic Pulmonary Oedema
|Acute Respiratory Distress Syndrome (ARDS)
|Respiratory Failure |
It is quite possible for a patient with COPD to also have a PE. Patients may go from Type 1 to become Type 2 when they tire and hypoventilate or receive sedation. Intubation and ventilation treat both types.
- Respiratory failure (PaO2 < 8 kPa) is a common medical emergency,
- Respiratory failure is a syndrome in which the respiratory system fails in one or both of its gas exchange functions: oxygenation and carbon dioxide elimination.
- It may be classified as either hypoxaemic with or without hypercapnia.
- Oximeters estimate arterial oxygen saturation are useful in assessment or monitoring.
- Oximeters tell us nothing about Carbon dioxide levels. For that we need an ABG.
| 1||PaO2 < 8 Kpa||PaCO2 levels < 6 Kpa.
| 2||PaO2 < 8 Kpa|| PaCO2 levels > 6 Kpa.
How much Oxygen should I give
- Normally Patients should have enough oxygen to achieve Sats 94-98%
- In COPD/T2 RF Patients should have enough oxygen to achieve Sats 88-92% and PO2 > 7 Kpa
- Generally If O2 sats > 98% then wean back on oxygen
- Generally If O2sats < 94% then consider increasing oxygen
- There are always exceptions to this e.g. In COVID we initially changed target to > 90% to conserve oxygen stocks. take advice if unsure.
- Type 1:Is the commonest form and usually due to alveolar fluid and similar pathologies. Often due to mismatch of ventilation and perfusion in the pulmonary alveolar bed.
- Pulmonary oedema,
- Pulmonary embolism
- High altitude
- Upper airways obstruction
- Type 2: It is usually due to ventilatory weakness, sedation or diseases that impair ventilation Hypercapnia causes acidosis for which there is over days a corresponding rise in renal retention of bicarbonate.
- Causes of Type 1 when tired, sedation, hypoventilating
- CNS disease e.g. stroke, tumour
- Exacerbation of COPD
- Neuromuscular weakness (Polio, GBS, MND, Spinal muscular atrophy)
- Muscle weakness (Muscular dystrophy, Myotonic dystrophy, Pompe disease)
- Flail chest, Rib#, Kyphoscoliosis
- Obesity, sedation, hypercarbia, alcohol
- Sputum and mucus plugs
- Oxygen saturation probe: does not detect CO2 levels.
- ABG: can tell pH, PO2, PCO2, HCO3 and base excess
- ECG: STEMI, AF, S1Q3T3 PE, RV Changes of COPD
- CXR: may show COPD changes, pneumonia, pneumothorax but will not show PE
- CTPA: if T1RF and Wells score suggest possible PE
Management of Type 1 RF
- ABC, High flow oxygen unless suspected COPD - see below
- Make a diagnosis and manage cause
- Diuretics if fluid, Chest drain if PTX, Antibiotics if infection
- Bronchodilators/Steroids if Asthma/COPD
- Thrombolysis/Anticoagulation if PE
- May need CPAP or NIV depending on cause
- May need intubation or ventilation or ECMO
Management of Type 2 RF
- ABC, Controlled Oxygen therapy start with 24% venturi mask aim for PaO2 > 7 kPa. The goal of treatment in acute on chronic type II respiratory failure is to achieve a PaO2 (> 7.0 kPa or 52 mmHg) without increasing PaCO2 and acidosis, while identifying and treating the precipitating condition.
- CO2 retention is seen with warm dilated peripheries and the patient is sleep and has bounding pulses and may have a flapping tremor
- Often with COPD the patients have prolonged expiration phase and wheeze as well as inflated lungs and intercostal indrawing. lips are pursed to help keep collapsed small airways open
- if there is significant right heart failure then there will be signs of peripheral oedema, raised jugular venous pressure, hepatomegaly, ascites.
- Make a diagnosis and manage cause
- Frequent physiotherapy Â± pharyngeal suction if mucus plugs or sputum to expectorate
- COPD+/- Pneumonia: Treat exacerbation if present.
- See other causes of Type 1 which may need addressed
- Non invasive ventilation and if this fails to work then escalate to ITU
- CPAP nasal or mask: Start at 5 cm H2O
- BiPAP Nasal or mask:Start at 10 cm H2O inspiration/5 cm H2O expiration
- May need intubation or ventilation : Initial ventilator settings:
- FiO2 1.0
- Tidal Volume- 6–10 ml/kg
- RR 10 -12
- PEEP- 5 cmH2O
- Pressure Support - 5 cmH2O
- ECMO may be considered
- Drug-induced Hypoventilation: consider naloxone for opiates and flumazenil for benzodiazepines if drugs recently taken. May need Naloxone infusion.
Important scenarios to recognise
- Impending Respiratory arrest: HR> 120/min. RR >30. Low BP, Pale and sweaty, agitation, confusion. Rising PaCO2 or fall in PaO2. Needing higher FiO2, rapid desaturation on disconnection from O2
- Masks may be poorly tolerated leading to Hypoxia in confused patients. Might be best to see if Oxygen via nasal prongs at 1 or 2 L/min is more effective and continuous with less interruptions if it gives a satisfactory PaO2.
- If a patient has normal PaO2 on high flow oxygen this is abnormal as you would expect the patient to have a PaO2 well above the normal range. This needs investigating as high FiO2 can hide worsening pathology. Patients should have only enough oxygen to achieve Sats 94-98%.
- If a hypoxic asthmatic patient has an ABG with a normal paCO2 (it should be low) this is a sign that they are tiring or worsening for some other reason and they need urgent ITU review
- A very low PaO2 in a patient who looks completely well, is not short of breath and has normal O2 saturations is likely a venous sample