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Airway resistance can also change over time. During an asthma attack the airways constrict causing an increase in airway resistance. Airway resistance can also vary between inspiration and expiration: In emphysema there is destruction of the elastic tissue of the lungs which help hold the small airways open. Therefore, during expiration ...
Obstructive conditions of the lower airway, including severe asthma or COPD episodes, can also lead to respiratory arrest. During these episodes, known as exacerbations, airway resistance is increased due to inflammatory changes in the lungs. This leads to increased work of breathing and decreased oxygen delivery to tissue.
Pulmonary compliance is calculated using the following equation, where ΔV is the change in volume, and ΔP is the change in pleural pressure: = For example, if a patient inhales 500 mL of air from a spirometer with an intrapleural pressure before inspiration of −5 cm H 2 O and −10 cm H 2 O at the end of inspiration.
Dynamic compression of the airways results when intrapleural pressure equals or exceeds alveolar pressure, which causes dynamic collapsing of the lung airways. It is termed dynamic given the transpulmonary pressure (alveolar pressure − intrapleural pressure) varies based on factors including lung volume, compliance, resistance, existing pathologies, etc. [1]
Bronchial hyperresponsiveness is a hallmark of asthma but also occurs frequently in people with chronic obstructive pulmonary disease (COPD). [2] In the Lung Health Study, bronchial hyperresponsiveness was present in approximately two-thirds of patients with non-severe COPD, and this predicted lung function decline independently of other ...
The airways have a tone baseline, and consequently a baseline level of contraction of their smooth musculature. Airway tone is a key determinant of lung function and the presence of respiratory symptoms in obstructive lung diseases such as asthma, where baseline airway tone is elevated. [2]
Airway remodelling is a multifaceted process involving multiple airway tissues. These include goblet cell hyperplasia, leading to increased mucus production, and airway smooth muscle hypertrophy (or smooth muscle cell hyperplasia), leading to the release of pro-inflammatory and pro-fibrotic messengers contributing to subepithelial fibrosis.
It is classically reduced in obstructive lung disorders such as asthma. Due to the wide range of 'normal' values and the high degree of variability, peak flow is not the recommended test to identify asthma. However, it can be useful in some circumstances. A small portion of people with asthma may benefit from regular peak flow monitoring. When ...