Bronchial asthma is charaterised by hyperresponsiveness of tracheobronchial smooth muscle to a variety of stimuli, resulting in narrowing of air tube, often accompanied by increased secretion , muscle edema and muscle plugging.
Signs and symptoms;
• Asthma is characterised by variable, intermittent and recurrent episodes of wheezing, SOB, chest tightening and coughing.
• Sputum may also be produced, but difficult to bring up.
• Symptoms are often worse at night, disturbing sleep, and in the mornings.
• Can also be exacerbated by cold air or from exercise.
Asthma is a complex respiratory disease characterised by;
• Airways inflammation
• Hyper responsiveness of bronchial smooth muscle (undue responsiveness to stimuli that would usually be innocuous)
• This leads to bronchospasm. Can be reversible either spontaneously or with treatment.
Airway narrowing during an asthma attack is caused by interlinked physical and inflammatory mechanisms;
o Bronchospasm –
Contraction of the airway smooth muscle reduces the size of the airway lumen
o Oedema –
Inflammation response induces mucus secreting cells, making them grow larger and secrete thicker and dryer mucus – further reducing the size of the airway lumen
o Plugging –
Tenacious secretions enter the airway lumen, obstructing airflow
Bronchospasm and inflammation in the airways lead to;
o Airway obstruction (characterised by an audible wheeze)
o Interruption to normal airflow (patients feel as if they are struggling to breathe through a narrow straw.)
o Decreased oxygen getting into the alveoli therefore decreased PaO2 (hypoxemia)
o Initially decreased PaCo2 as patient hyperventilates to try and compensate from the airway tightness, as patient tires they may progress to increased PaCo2 as they can’t breathe out the Co2.
o Sputum plugging due to inflammation and/or any underlying chest infections that may have triggered the attack.
o Increased work of breathing and consequent fatigue
o Persistent inflammation as seen in chronic asthma leads to fibrosis of the airway walls and irreversibility of the bronchospasm.
• The physio can teach breathing control to allow the patient to prevent dyspnoea from worsening due to anxiety. Relaxation reduces energy consumption and decreases the work of breathing. Positions of ease can also reduce the work of breathing.
• If the patient has retained secretions the physio can teach ACBT and assess
the need for further techniques if necessary, such as PEP or Manual clearance techniques.
• Drug therapy – bronchospasm can be controlled by using “reliever” inhalers which contain Salbutamol/Ventolin. Inflammation can be controlled with “preventer” inhalers which contain cortico-steroids.
• The physio can also enable the patient to undertake regular aerobic exercise to maintain their exercise tolerance. They can monitor and advise regarding the level of exercise and ensure patient know when they are and are not safe to exercise through monitoring and warm up.