Expiratory wheeze
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Summary
10 papers analyzed
These studies suggest that expiratory wheeze is associated with airway flow limitation, obstructive disease, viral infections, severe airflow limitation in asthma, and can be influenced by factors such as obesity, atopy, and early childhood respiratory infections.
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Understanding Expiratory Wheeze: Mechanisms, Detection, and Clinical Implications
Mechanisms of Expiratory Wheeze in Airway Flow Limitation
Expiratory wheeze, a high-pitched whistling sound during exhalation, is primarily a manifestation of airway flow limitation. Research indicates that forced expiratory wheezes (FEW) occur when there is a significant change in transpulmonary pressure (Ptp) and a small change in flow rate (V), marking the onset of flow limitation in the lungs. This phenomenon is closely related to the "equal pressure point" (EPP) in the larger airways, where the pressure inside the airway equals the pressure outside, leading to airway collapse and subsequent wheezing. The frequency spectra of FEW are similar to those found in obstructive airway diseases, suggesting a common underlying mechanism.
Detection and Analysis of Wheezing in Obstructed Airways
Wheezing is a common clinical finding in patients with asthma and chronic obstructive pulmonary disease (COPD) during episodes of severe airway obstruction. A novel technique involving a contact sensor on the trachea and fast Fourier transform analysis has been developed to record and analyze wheezing during forced expiratory maneuvers. This method has shown that patients with obstructed airways exhibit more wheezes compared to healthy subjects, with a higher mean frequency of wheezes in control subjects. This technique provides a clear and objective identification of obstructive disease by analyzing the number and frequency of wheezes.
Viral Etiology of Acute Expiratory Wheezing in Children
Acute expiratory wheezing in children is often associated with viral infections. A study in Finland found that respiratory syncytial virus (RSV), enteroviruses, and rhinovirus are the most common causative agents of wheezing in hospitalized children. RSV was particularly prevalent in infants, while respiratory picornaviruses were more common in older children. This highlights the importance of focusing on these viral infections for the prevention and treatment of wheezing illnesses in children.
Wheezing and Lung Mechanics in Asthmatic Subjects
In asthmatic individuals, wheezing is a sign of severe airflow limitation, often occurring late in the respiratory cycle during methacholine-induced bronchoconstriction. Expiratory wheezes typically fall in pitch during a breath and occur at a mean of 58% of the maximal tidal expiratory flow, indicating a strong correlation with severe airflow obstruction. This suggests that the presence of wheeze during tidal breathing is indicative of significant airway limitation in asthmatic patients.
Impact of Inhaled Corticosteroids on Wheezing in Children
Inhaled corticosteroids, commonly used to manage asthma, have been studied for their effect on wheezing episodes associated with viral infections in children. While regular use of beclomethasone dipropionate improved lung function and decreased bronchial responsiveness, it did not significantly affect the frequency, severity, or duration of wheezing episodes. This indicates that inhaled corticosteroids may offer limited clinical benefit for children with episodic wheezing linked to viral infections.
Long-term Respiratory Outcomes in Wheezing Infants
Wheezing in infants, particularly those with acute lower respiratory tract infections (ALRTI), is associated with impaired lung function that can persist over time. Infants with wheezing showed significantly decreased time to peak tidal expiratory flow as a percentage of total expiratory time (TPTEF/TE) and increased peak tidal expiratory flow (PTEF) compared to non-wheezing infants and controls. These lung function deficits were linked to a higher risk of recurrent wheezing and pneumonia, underscoring the need for close monitoring and management of wheezing infants.
Conclusion
Expiratory wheeze is a critical indicator of airway flow limitation and severe airflow obstruction, particularly in conditions like asthma and COPD. Advanced detection techniques and understanding the viral etiology in children can aid in better diagnosis and management. While inhaled corticosteroids improve lung function, their role in treating viral-induced wheezing in children remains limited. Persistent wheezing in infants can lead to long-term respiratory issues, highlighting the importance of early intervention and continuous monitoring.
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