Respiratory Failure Flashcards
Define dyspnoea
Dyspnoea is the sensation of breathlessness. ^[subjective, discomfort: qualitatively distinct sensations that vary in intensity]
How to determine the cause of dypnoea
- If in doubt, ask the patient!
- Determine the differential diagnosis and order appropriate tests.
- Observe the patient’s clinical condition.
- Perform CXR and ECG.
- Assess if the patient is in respiratory failure.
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Define respiratory failure and list the types and their features
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Respiratory failure occurs when the pulmonary system cannot meet the metabolic demands of the body.
Types of Respiratory Failure
- Type 1: Hypoxaemic respiratory failure
- Arterial partial pressure of oxygen (PaO2) ≤ 60mmHg on room air.
- Type 2: Hypercapneic respiratory failure
- Arterial partial pressure of carbon dioxide (PaCO2) ≥ 45mmHg.
Hypoventilation
- Total ventilation = tidal volume x respiratory rate.
- Hypoventilation can be due to inadequate tidal volume or respiratory rate.
- Causes of inadequate tidal volume
- RLD
- Muscle weakness or neuromuscular disease
- kyphoscoliosis
- Causes of inadequate respiratory rate
- opioids and benzodiazepines
hypoventilation–ventilatory defect: feature of type 2
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Describe the clinical signs of respiratory failure and respiratory compensation
Clinical Signs of Respiratory Failure
- Paradoxical breathing ^[obstruction leads to see-saw of chest and abdominal movements on inspiration] due to ineffective ventilation
- Increased sympathetic tone= tachycardia, hypertension and sweating
Clinical Signs of Respiratory Failure (cont.)
- End-organ hypoxia:
- Altered mental status.
- Bradycardia and hypotension (late signs).
- Haemoglobin desaturation:
- Cyanosis.
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Clinical signs of respiratory compensation:
- Tachypnoea.
- stridor or wheezing
- Use of accessory muscles.
- Nasal flaring.
- Intercostal, suprasternal, or supraclavicular recession.
Describe pulse oximetry and limitations
- Estimates arterial saturation (SaO2) using absorption of two different IR wavelengths
- Note -sigmoidal relationship of O2-Hb
- Sources of SaO2 error. Many:
- poor peripheral perfusion.
- dark skin (oximeter over-reads slightly)
- false nails or nail varnish
- bright ambient light
- poorly adherent probe
- excessive motion
- carboxyhaemoglobin (SpO2 > SaO2 )
- hyperlipidaemia
- lipid infusion for TPN
- propofol infusion
If in doubt, get ABG
List typical values on ABG
- pH: 7.35-7.45.
- PaO2: 83-105 mm Hg.
- PaCO2: 35-45 mm Hg.
- Bicarbonate: 22-28 mmol/L.
Distinguish between acute and chronic respiratory failure
- Acute RF develops rapidly with no time for compensation.
- Chronic RF leads to compensation.
- Increased HCO3- with type 2 RF.
- Decreased HCO3- with type 1 RF.
Describe management and correction of respiratory failure
Management of Respiratory Failure
- Determine the appropriate care setting - clinical circumstances (facilities, severity, and early response to treatment in ED) will determine what is required
- **Adequate airway patency is key. (i.e. ABCDE)
- Essential to monitor blood gases and early response to treatment
Correction of respiratory failure
- Correction of underlying cause.
- Choose the appropriate supplemental oxygen delivery mode.
- Target PaO2 of 60 mmHg for tissue oxygenation.
- Continuous monitoring of PaO2 and PaCO2.
Describe oxygen therpay and non-invasive ventilation and indcations
Oxygen Therapy
- Different interfaces deliver different FiO2.
- e.g. prongs up to Q 4l/min
- venturi mask: uses air and O2 to get precise FiO2
- non re breather mask in acute
- high flow nasal prongs
- long term home O2
- Choose the interface based on clinical need.
Non-Invasive Ventilation (NIV) ^[hypoventilation]
- Delivery of ventilatory support without invasive airway.
- Treatment for type 2 respiratory failure.
Indications for NIV
- Acute exacerbation of COPD.
- Bronchiectasis with type 2 respiratory failure.
- OSA/Obesity hypoventilation.
- Neuromuscular disorders.
- Chest wall deformities.
- Type 1 RF due to pneumonia in immuno-suppressed patients.
Which patients need NIV
- signs and symptoms of ARDS: tachypnoea > 24, accessory muscle use and paradoxical breathing
- gas exchange abnormalities i.e. > 45 mmHg, and pH <7.35
Contraindications to NIV
- Untreated pneumothorax.
- Imminent cardiac/respiratory arrest.
- Medically unstable patients.
- Sepsis with hypotension. ^[niv in icu]
- Inability to protect upper airways.
- Decreased conscious state.
- Vomiting.
Other contraindications include confusion or agitation, facial burns and trauma, or copious respiratory secretions.
(comes in different sizes, suited for in-patient or home care settings).
Describe NIV assessment of
treatment response
- Pulse oximetry, RR, HR, BP, accessory muscle use.
- Blood gas 1-2 hours after starting NIV.
- If improving, repeat after 6 hours.
- If not improving, medical assessment and repeat ABG in 1-2 hours.
List causes of hypoventilation
- Causes of inadequate tidal volume
- RLD
- Muscle weakness or neuromuscular disease
- kyphoscoliosis
- Causes of inadequate respiratory rate
- opioids and benzodiazepines
