Airflow limitation

Breathlessness in asthma crises is one of the most distressing respiratory disorders. It has been clinically observed that some patients become very distressed with relatively little change in lung mechanics. The major mechanism occurring in asthma is increased elastic loading of the inspiratory muscle as a result of dynamic hyperinflation. The most objective changes contributing to breathlessness in acute bronchoconstriction are the decrease in inspiratory capacity, reflecting an increment in end-expiratory lung volume, and the change in esophageal pressure needed to produce the inspired tidal volume ( Lougheed.etal 1993).

Breathlessness may be caused by upper airway obstruction due to a foreign body, an infection, or trauma or allergic reaction in the hypopharynx, tongue, or soft tissue in this area.

The mechanical abnormality in chronic airway obstruction is expiratory flow limitation related to dynamic airway compression and dynamic hyperinflation. However, dynamic airway compression plays an indirect role in the sensation of breathlessness. Exertional breathlessness mainly depends on ventilatory demands and reserves, but dynamic hyperinflation contributes significantly and explains the intersubject variability in the sensation of breathlessness ( OlDoDD.ell...and We.b.b..„1993.). The disparity between mechanical impairment and the sensation of breathlessness confirms that other factors are involved in the generation of this sensation. The increase in minute ventilation is perceived differently by different patients, and it is difficult to determine whether this tolerance is an individual characteristic or a temporal adaptation to perception of respiratory load.

Coping with Asthma

Coping with Asthma

If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.

Get My Free Ebook

Post a comment