Breathlessness and Disease (DISEASE MECHANISMS) Flashcards
What causes breathlessness?
heart failure Asthma and lung disease PE Angina equivalent Hyper-ventilation syndrome Anaemia
What are the anatomical categories of breathlessness?
Muscles, nerves, bones Vascular, ventricular failure Obesity, diaphragm Brain Airways Parenchyma Pleura
What are the functional categories of breathlessness?
Oxygen transport
Mechanical disadavatage
Respiratory drive (in the medulla)
Perception of breathing
Which functional issue would respiratory muscle weakness cause leading to breathlessness?
Mechanical disadvantage
How can a stroke cause breathlessness?
Interferes with respiratory drive
What is Fick’s equation?
VO2 = CO x (CaO2 - CvO2)
What does Fick’s equation measure?
How much blood you pump vs absorb
When is VO2 max reached according to Fick?
When oxygen consumption remains at steady state despite and increased workload
What is the average VO2 in a male?
45 ml/kg/min
Breathlessness _____ hypoxia
does not equal
Hypoxia _____ breathlessness
does not equal
Ho can obesityy reduce mechanical ventilation
Creating pressure from outside –> weakness on chest wall
What are examples of mechanical restrictions?
Motor neurone disease Obesity Pleural effusion Guillan-Barre syndrome Hyperventilation ILD
What can decrease the respiratory drive?
COPD
Ondine’s curse / CCHS
What is CCHS?
Congenital central hypoventilation syndrome
aka Ondine’s curse
How does COPD lead to type II respiratory failure?
Retain CO2
CO2 increases
Increases CO2 dependence
Lose hypoxic drive if oxygen given up
Why do patients with CCHS/Ondine’s curse need to ventilated overnight?
Hypoxic drive stops when they sleep - respiratory arrest
What is the normal breathing rate and volume?
12 breaths per minute and 6 L per minute
Hyperventilation causes what in terms of perception of breathing?
Constriction of airways and possible airway obstruction
How do you assess a patient with breathlessness?
History
Probability
Exam
Test
What needs to be asked in the history of a breathless patient?
Exacerbating or relieving factors
Time of onset and duration
Timing (throughout)
Exercise capacity / severity assessment - ADLs
Associated symptoms
Personal / family history of respiratory disease
Social: job, smoking, other exposures
What does an instant onset of breathlessness indicate?
Pneumothorax
PE
What does an acute (min-hours) onset of breathlessness indicate?
Asthma
Pneumonia
Acute MI
Cardiac tamponade
What does a subacute (days) onset of breathlessness indicate?
Pleural effusion
Pulmonary vasculitis
SVCO
What does chronic breathlessness (months-years) indicate?
COPD
ILD
Pulmonary hypertension
Anaemia
What are the options for investigation of breathlessness?
Spirometry
Measure gas transfer
Peak flow meter
CXR / CT / V/Q scan
What is meant by using probability to diagnose?
Ween down number of likely outcomes using history
