Management of Breathlessness Flashcards
Tachypnoea is:
Rapid breathing
Hyperpnoea is:
Increased ventilation in response to increased metabolic requirements
Hyperventilation is:
Ventilation in excess of metabolic requirements (HR increased and checked via ECG)
Tachypnoea, hyperpnoea, hyperventilation describe:
increases in ventilation in response to different stimuli. They may represent normal physiological response
Dyspnoea is:
subjective term generally applied to the unpleasant sensation of an awareness of breathing discomfort
Dyspnoea is breathing that is laboured or distressing
Breathlessness is:
one of many descriptions used by patients to convey their experience of dyspnoea: is an awareness of the intensity of breathing or suggests unrewarding respiration/ “chest tightness” or inability to get “air in”
Breathlessness, dyspnoea and shortness of breath are:
often used interchangeably. In chronic patients SOB may be normal so have to check with them if it is changing. Dyspnoea /Breathlessness is the most common symptom in advanced cardiopulmonary disease
Work of breathing (WOB) is:
The Work done to overcome the resistive forces of the airways, lungs and chest wall. Occurs in 2 ways:
- The pressure required to move a volume of gas (Transpulmonary pressure x tidal volume)
- The rate of oxygen consumption by the respiratory muscles, i.e. the oxygen cost of breathing
In health WOB uses 2-5% of total consumption at rest. This can increase to 40% in patients with COPD
During quiet respiration the WOB is performed:
- entirely by the inspiratory muscles
Expiration is passive, powered by the elastic recoil of the lungs - As breathing becomes more difficult the muscles work harder and thus the WOB increases
- The efficiency of the respiratory muscles can be reduced in patients presenting with many different conditions, i.e. COPD (E, CB), IPF
- Many patients cope with reduced respiratory muscle efficiency until something happens e.g. a chest infection and then they deteriorate more rapidly
In health breathing normally occurs:
- Subconsciously and is monitored by multiple sensory systems
- When excessively stimulated this provides sensory feedback which is interpreted as a sense of effort or perceived as dyspnoea
- The perception of increased effort or dyspnoea does not usually elicit distress in health as extra respiratory drive is rewarded by increased mechanical output and ventilation
Those with respiratory or CV disease become aware of:
unpleasant breathing sensations at very low levels of activity, at rest or in response to stress or emotion
Dyspnoea is affected by:
Psychological state Experiences Memory Fear Anxiety Depression Anger/frustration Effort Discomfort
Outcome measures of dyspnoea/SOB:
- Modified Borg scale of perceived breathlessness
- Medical Research Council Quantifies the functional limitations and can provide useful outcome measures, usually done over weeks.
Other causes of ↑WOB and Dyspnoea:
- Increased metabolic rate: Increases ventilation, e.g. fever, exercise
- Cardio-vascular issues: inadequate cardiac output, anaemia
- Deconditioning: Lactate accumulates at low exercise levels causing ↑ ventilation
- Perfusion limitation: Large V/Q mismatch due to wasted ventilation e.g. PE
Anaemia symptoms are:
SOB, fatigue, pallor. Check not bleeding from elsewhere.
Mechanical causes of ↑WOB and Dyspnoea:
- Increased airway resistance
- Increased elastic load
- Decreased energy supply
- Respiratory muscle dysfunction, i.e. reduced power or endurance
- Increased drive to breathe
- Increased alveolar surface tension
Increased airway resistance/resistive load pathologies include:
- Obstructive airways disease - increased secretions
- Asthma - inflammation in the airways
- Chest infection - bronchospasm
- Lung tumour - obstruction in the airway
Increased elastic load pathologies include:
- Fibrotic lungs, Surfactant depletion, Hyperinflation: ↑ alveolar surface tension and reduction in lung compliance increasing the inspiratory muscle work required to overcome the elastic recoil of the lungs.
- Kyphoscoliosis, Ankylosing spondylitis, Pregnancy, Distended abdomen, Obesity, Abdominal surgery: Reduction in chest wall compliance or compliance of abdominal compartment increases insp. Muscle work
Decreased energy supply pathologies includes:
- Eating difficulties: malnutrition (cechexia?)
- Hypovolemic shock: lack of perfusion to the respiratory muscles
Increased drive to breathe pathologies include:
Parenchymal disorders (pneumonia or fibrosis), Acidosis, Anaemia: stimulates nerve impulses from interstitial receptors increasing drive to breathe
Increased alveolar surface tension pathologies include:
Pulmonary oedema, Acute respiratory distress syndrome (ARDS), Surfactant depletion: increased resistance to expansion/reduced compliance increasing insp. muscle work to overcome elastic recoil of lungs
Rib #/flail segment causes high WOB because:
Disrupted mechanics of thoracic cage
A segment of the chest wall which is flail is unable to contribute to lung expansion
What causes high WOB in emphysema:
- Increase in expiratory airflow resistance increases expiratory muscle work
- Severe hypoxaemia may contribute to WOB by stimulating drive to breathe
- Muscles and joints are at a mechanical disadvantage due to passive (trapped air) and dynamic hyperinflation
- Increased inspiratory muscle work occurs to hold open floppy airways (dynamic HI), even during exhalation
Signs of hyperinflation and WOB in emphysema:
Observation - hoovers sign (up on inspiration due to flat diaphragm), intercostal recession, tracheal tug, use of accessory muscles (pec minor/major, serratus ant, scalene, SCM) and pursed lip breathing
CXR - flattened diaphragm/loss of costophrenic angles, horizontal ribs
