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Dynamic hyperinflation is a phenomenon that occurs when a new breath begins before the lung has reached the static equilibrium volume. [1] In simpler terms, this means that a new breath starts before the usual amount of air has been breathed out, leading to a build-up of air in the lungs, and causing breathing in and out to take place when the lung is nearly full.
HIV associated emphysema occurs over a much shorter time than that associated with smoking; an earlier presentation is also seen in emphysema caused by alpha-1 antitrypsin deficiency. Both of these conditions predominantly show damage in the lower lungs, which suggests a similarity between the two mechanisms. [31]
Typically, infections cause 75% or more of the exacerbations; bacteria can roughly be found in 25% of cases, viruses in another 25%, and both viruses and bacteria in another 25%. Airway inflammation is increased during the exacerbation resulting in increased hyperinflation, reduced expiratory air flow and decreased gas exchange. [1] [2]
This leads to hyperinflation of the alveoli and, thus, the lungs. When this occurs asymmetrically, one lung can be larger than the other. [23] A severe variant of this condition is called giant bullous emphysema. On chest x-ray, one lung will be significantly more inflated than the other, causing a mediastinal shift.
Following are terms that specify a type of lung size and/or activity. More specific definitions may be found in individual articles. Eupnea – normal breathing; Apnea – absence of breathing
Hyperinflation therapy (HIT) is a very common [1] therapy performed on patients who have some sort of respiratory distress. The therapy involves applying volumes greater than normal to reinflate the collapsed alveoli in the lungs. There are many different techniques used to administer hyperinflation therapy. [2]
The increased total lung capacity (hyperinflation) can result in the clinical feature of a barrel chest – a chest with a large front-to-back diameter that occurs in some individuals with emphysematous COPD. Hyperinflation can also be seen on a chest X-ray as a flattening of the diaphragm. [citation needed]
Activation of α 1-adrenergic receptors produces anorexia and partially mediates the efficacy of appetite suppressants like phenylpropanolamine and amphetamine in the treatment of obesity. [10] Norepinephrine has been shown to decrease cellular excitability in all layers of the temporal cortex , including the primary auditory cortex .