4 The breathless patient Flashcards
Define breathlessness or DYSPNOEA
- Dyspnoea, the sensation of feeling breathless, is a symptom experienced under conditions in which there is an inordinately high ventilatory demand relative to the ability to breathe, ‘air hunger’, and a heightened level of awareness of respiratory sensation and often a strong emotional component.
Its major physical sign is tachypnoea (abnormally rapid breathing)
What things to keep in mind when assessing the level of dyspnoea?
An important assessment is whether the dyspnoea is related only to exertion and how far the patient can walk at a normal pace on flat ground
Other clarifications:
- variability in symptoms
- good/bad days?
- importantly; any times of day/night that are worse than others
Discuss how one may encounter shortness of breath (SoB)
Can be caused by anything that reduces PaO2 or increases PaCO2
You can have issues with:
- Ventilation - the amount of air brought into alveoli
- Perfusion - the amount of blood brought to alveoli for gas exhange
- Diffusion - (exchange surface) - defects include interstitial fibrosis, pulmonary oedema
Describe the problems that may occur to an ideal gas exchange unit
- Poor blood flow from the right side of the heart (clot)
- Too much CO2
- Abnormal tissue between alveolus and capillary (barrier to O2 transfer)
- Anaemia (lack of Hb)
- Faulty Hb (barrier to HbO2 complex)
- Poor backflow to heart e.g. failing left ventricle (hence, blockage in pulmonary vein)
How to distinguish between respiratory and cardiovascular causes of SoB?
Can be done using patient history and examination
- It is based on taking full history + full examination, then selecting tests to rule differential diagnoses in or out
Describe the various causes of dyspnoea
- LVF or Mitral Stenosis: slow or sudden (pulmonary oedema); cause: increased pressure in pulmonary capillaries
- Chronic bronchitis: chronic productive cough, with slowly progressive dyspnoea; Cause: excess mucus production
- COPD: overdistention of airspaces distal to terminal bronchioles; slowly progressive with features of bronchitis, asthma, and emphysema leading to progressive dyspnoea
- Asthma: problem with ventilation, (reversible airway disease - difficult to breathe out); acute episodes, separated by symptom-free breaks
Describe congestive heart failure (CHF)
Definition: the heart fails when it is unable to eject blood delivered to it by the venous system
- Blood builds behind the heart
- Most common type is LHF (Left-sided heart failure)
- In LHF, blood backs up in the lungs (pulmonary congestion)
> LHF - pulmonary oedema (to raised hydrostatic forces in pulmonary vasculature)
History taking (for breathlessness)
- Age?
- Onset of symptoms?
- Variability?
- Drug history
- Occupation? Pets?
- Associated symptoms?
Describe orthopnoea
Defined as breathlessness on lying down.
- While it is classically linked to heart failure, it is partly due to the weight of the abdominal contents pushing the diaphragm up into the thorax.
- Such patients may also become breathless on bending over
Describe the signs of breathlessness
Digital clubbing
- (can be due to lung cancer, bronchiectasis, pulmonary fibrosis, cyanotic heart disease)
- Cyanosis
> Central: reduced O2 saturation (>80%), blueish tongue and lips
> Peripheral: bluing of extremities like fingers
Describe a physical examination you would to a patient suspected of breathlessness
- Inspection
- Palpation
- Percussion
- Auscultation
Describe what you may hear upon auscultation of a patient with suspected breathlessness
- Wheeze: expiration, limitations of flow in asthma and COPD
- Crackles: opening of closed bronchioles
> Early inspiration associated with diffuse airflow limitation (e.g. bronchiolitis)
> Late inspiration associated with pulmonary oedema, fibrosis, bronchiectasis - Pleural rub: inflammation of pleural surfaces
- Stridor: high pitched breath sounds resulting from airflow through the obstructed airway
List some respiratory causes of breathlessness
- Asthma (reversible)
- COPD
- Pneumonia
- Lung cancer
- Pneumothorax
- Foreign bodies
- most other respiratory diseases
List some cardiovascular causes of breathlessness
- Heart failure: pulmonary oedema
- Pulmonary embolism
- Valvular disease
List some other causes of breathlessness
- Functional breathlessness (e.g. obesity)
- Anaemia (PaO2 and SaO2 are normal)
- Anxiety
- Thyroid Disease
- Some muscle disorders
Describe causes of hypoxemia
- Decreased inspired pO2 [high altitude]
- Respiratory acidosis, caused by CO2 retention in lungs, always produces a corresponding decrease in Alveolar pO2, which in turn decreases both PaO2 and Sa O2
> Lots of causes of respiratory acidosis: depression of the medullary respiratory centre (barbiturates), paralysis of the diaphragm (e.g. amyotrophic lateral sclerosis), chronic bronchitis - Ventilation defect
- Perfusion defect
Describe how V/Q mismatch causes SOB, and why physiological compensation is limited
- Ventilation (V) refers to the flow of air into and out of the alveoli
- Perfusion (Q) refers to the flow of blood to alveolar capillaries
- Normal V/Q ratio is 0.8
- Changes to V/Q can lead to hypoxemia (decreases in PaO2 on ABG)
There are various mechanisms of hypoxemia:
- V/Q mismatch, right-to-left shunt, diffusion impairment hypoventilation, and low inspired pO2
List some routine investigation for SOB:
- Blood gas and pulse oximetry
- Haematology (FBC)
- Lung function testing (FEV1, FVC and FEV1:FVC)
- Chest X-ray
Other tests:
- Peak flow
- High-resolution CT
- More extensive lung function tests (gas transfer)
- 6-minute walk/shuttle walk test
- Sputum culture
- Lung biopsy
- Bronchoscopy
Describe a blood gas and pulse oximetry test for breathlessness
- Arterial blood gas monitoring: gives pH (normal 7.35-7.45), PaO2 (10.5 - 13.5kPa), and PaCO2 (5.1 - 5.6 kPa)
- Pulse oximetry: Measures blood redness; normal blood oxygen saturation level should be >94%
Describe haematology (FBC) tests for breathlessness
Important as if anaemia is the cause of SOB, saturations can show up normal
- Haemoglobin (Hb)
- Haematocrit
- Mean corpuscular volume
Describe lung function testing for breathlessness
- FEV1: forced expiratory volume in 1 second
- FVC - forced vital capacity: maximum amount of air a person can expel from the lungs after a maximum inhalation
- FEV1/FVC: normal is >80%
What is confirmation bias?
It is our tendency to cherry-pick information that confirms our existing beliefs or ideas
- Confirmation bias is the tendency to acquire or evaluate new information in a way that is consistent with one’s pre-existing beliefs
Overview of breathlessness in a clinic
- Take a good history
- Examine the patient
- Analyse the information
- Concept of differential diagnosis
- Logical line of investigation and treatment
