Breathlessness Flashcards
What co-morbidities contribute to shortness of breath?
- Pneumothorax
- Cardiac problems/ heart disease/ heart failure
- pulmonary hypertension caused by embolism
- anaemia
- pneumonia
- anxiety
- lung cancer
- COPD
What can cause an acute exacerbation of COPD?
- respiratory infection
- exposure to smoke/ pollution
What are symptoms of infective exacerbations?
- coughing up yellow/green sputum
- lack of appetite
- swelling in both ankles
- pyrexia
- low O2 sats
- difficulty breathing
What tests are used to diagnose the cause of exacerbations?
- Chest X-ray
- Blood/ arterial blood gas tests (to test Hb, pH, pCO2, pO2)
- ECG
- Sputum test
What is acidosis and what are the 2 types?
Acidosis is a disorder that leads to acidaemia (when pH <7.35) .
- Respiratory acidosis
- Metabolic acidosis
How can the 2 types of acidosis be differentiated?
- Respiratory acidosis: ⬆️ CO2 –> ⬆️ HCO3- —-> ⬇️ pH (more acidic)
- Metabolic acidosis: Too much acid which consumes HCO3- (⬇️ in bicarbonate) –> ⬇️ pH (not related to CO2 but more to do with the inability of the intercalated cells in the kidney collecting ducts to maintain acid/base balance)
What are the 2 types of respiratory acidosis/failure?
- Type 1 Respiratory failure
- Type 2 Respiratory failure
What is the mechanism behind Type 1 respiratory failure?
Failure of the heart/lungs to provide adequate O2 to meet metabolic demands (hypoxemia). The CO2 is usually normal/low.
What are some causes of Type 1 RF?
- R-L cardiac shunt (allows blood from R/L sides to mix)
- Alveolar hypoventilation
- Pulmonary embolism
- Asthma
- Pneumothorax
- Lung collapse
- Acute Respiratory Distress Syndrome
What is the mechanism behind Type 2 RF?
The failure of the lungs to remove CO2 (hypercapnia). O2 levels will also be affected.
What are some causes of Type 2 RF?
- drug overdose
- head injury
- upper airway obstruction (oedema, infection)
- COPD
What test is used to evaluate Metabolic acidosis?
Anion gap:
(Na+) -(HCO3-)- (Cl-)= Anion gap (8-16mmol/l)
(Na+) +(K+) -(HCO3-)- (Cl-)= Anion gap (12-20mmol/l)
What does a high anion gap suggest?
(>30mmol/l) Metabolic acidosis
- High anions (bicarbonate)
What can cause a high anion gap?
- Lactic acidosis
- Ketoacidosis
- Renal failure
What causes normal anion gap metabolic acidosis?
- The bicarbonate ions are replaced by excess Cl-
- Can be caused by diarrhoea + renal tubular acidosis
What is alkalosis and what are the 2 types?
Alkalosis is a disorder that leads to alkaemia (when pH >7.45) .
- Metabolic
- Respiratory
What happens in metabolic alkalosis? What can cause it?
⬆️ Bicarbonate ions -> ⬆️ pH
Caused by…
- excess antacid consumption
- kidney diseases
What happens in respiratory alkalosis? What can cause it?
⬇️ CO2 -> ⬇️ Bicarbonate ions -> ⬆️ pH
Caused by…
- hyperventilation
- high altitude
What is the compensatory mechanism for respiratory acidosis?
Metabolic alkalosis:
1) More CO2 + H20 -> HCO3- + H+ by carbonic anhydrase
2) Kidney excretes H+ and retains HCO3-.
3) ⬆️ pH
What is the compensatory mechanism for metabolic acidosis?
Respiratory alkalosis:
1) More ventilation to ⬇️ CO2
2) ⬇️ Carbonic acid, ⬇️ H+
3) ⬆️ pH
What can be seen on a Chest X ray, in an infective exacerbation of COPD?
Opacification of parts of the lung (area of whiteness) -> air in alveoli have been replaced by bacteria
How would the chest X-ray be different for a pleural effusion?
In a pleural effusion, fluid builds up between the pleura of the lungs.
There will be opacification but it will be more contained in a certain area.
With infections, the whiteness will generally be more spread out.
What is the initial drug management of an infective exacerbation of COPD?
- Bronchodilators (SABA/LAMA inhalers with nebulisers)
- Corticosteroids (to help relieve breathlessness)
- Broad-spectrum antibiotics
- Oxygen therapy
(mucolytics -> carbocisteine, antivirals)
What are the initial non-drug management options for an infective exacerbation of COPD/ Type 2 RF?
- BiPAP
- Encouraging them to sit upright
- Chest physiotherapy
What is BiPAP/NIV (non-invasive ventilation)?
Bilevel Positive airway pressure machine.
- It delivers 2 different pressures: a higher inspiratory and a lower expiratory pressure
Why is the inspiratory pressure lower than the expiratory pressure in BiPAP?
To reduce the work the patient needs to do to exhale (bigger pressure gradient).
What is the purpose of the expiratory pressure (EPAP)?
It helps to recruit the under-ventilated alveoli by splinting the airways open. It increases the Functional Residual Capacity.
What is the purpose of inspiratory pressure (IPAP)?
It increases the tidal volume (total volume of air breathed in and out).
How is CPAP different?
It delivers a fixed, single continuous positive airway pressure which keeps the airways open.
What can it be used to treat?
- Mild Obstructive Sleep Apnoea
- Type 1 RF
What does CPAP increase?
- Tidal volume
- Functional residual capacity
Why does residual volume decrease after being put on these mechanical ventilators?
Lungs are usually hyperinflated in COPD due to the reduction in elasticity. This traps a lot of air.
- CPAP/BiPAP reduces the hyperinflation, thus reducing the residual volume.
Why is non-invasive ventilation preferred to endotracheal intubation?
Muscle paralysis + sedation aren’t required for NIVs because they are non-invasive.
What is PEEP?
Positive End Expiratory Pressure -> pressure at the end of expiration, that’s exerted on the lungs.
Why is swelling in the ankles/ oedema common in COPD exacerbations? (alveoli in lungs)
1) Alveolar hypoxia (insufficient O2)
2) This causes hypoxic pulmonary vasoconstriction.
Why does pulmonary vasoconstriction occur?
The lungs want to maximise gaseous exchange so they divert blood (+O2) to well-ventilated areas.
It would be a waste for the blood to go to the hypoventilated alveoli because little gas exchange would occur there.
Why is swelling in the ankles/ oedema common in COPD exacerbations? (lungs + arteries + heart)
1) Alveolar hypoxia (insufficient O2)
2) This causes hypoxic pulmonary artery vasoconstriction.
3) Vasoconstriction increases vascular resistance.
4) This results in pulmonary hypertension.
5) Increase in Right ventricular afterload.
Why is there an increase in Right Ventricular afterload?
Due to the increased vascular resistance-> heart has to work harder to pump blood to the lungs.
Why is swelling in the ankles/ oedema common in COPD exacerbations? (heart)
1) Alveolar hypoxia (insufficient O2)
2) This causes hypoxic pulmonary artery vasoconstriction.
3) Vasoconstriction increases vascular resistance.
4) This results in pulmonary hypertension.
5) Increase in Right ventricular afterload.
6) Right Ventricular failure
7) Peripheral oedema
What is the cause of peripheral oedema?
The Right side of the heart can’t pump blood to the lungs so blood backs up and fluid enters the interstitial space in tissues.
Why does peripheral oedema lead to swelling in the feet/ankles?
Due to gravity, fluid from blood enters tissues in the ankle/feet.
