NVBS in Respiratory Examination
NVBS stands for Normal Vesicular Breath Sounds in respiratory systemic examination.
Definition and Acoustic Characteristics
Normal vesicular breath sounds represent the characteristic sound pattern heard over healthy lung parenchyma during auscultation. 1
Key acoustic features include:
- Exponential decay pattern: Power decreases exponentially as frequency increases, with a characteristic log amplitude vs. log frequency relationship 2
- Frequency range: Maximal frequencies average 446 ± 143 Hz during inspiration and 286 ± 53 Hz during expiration over the lung bases 2
- Slope characteristics: The power spectrum slope averages 13.0 ± 1.4 dB/octave over the right lung base and 12.6 ± 2.4 dB/octave over the left lung base 2
- Phase differences: Inspiratory sounds have significantly higher maximal frequencies than expiratory sounds (p < 0.01) 2
Clinical Significance in Examination
Normal vesicular breath sounds indicate:
- Intact airways without significant obstruction 1
- Normal lung parenchyma without consolidation or effusion 1
- Adequate air movement through the respiratory system 2
Distinguishing from Abnormal Breath Sounds
Critical distinctions that must be recognized:
- Wheezes: High-pitched whistling sounds (80-1,600 Hz range) indicating airway obstruction, commonly in asthma and COPD 1, 3
- Rhonchi: Low-pitched continuous sounds (≤200 Hz) that typically clear with coughing 1
- Crackles: Discontinuous explosive sounds heard during inspiration in conditions like pneumonia and bronchiolitis 1
- Absent exponential decay: Loss of the characteristic exponential pattern suggests severe airway disease, as seen in severe asthma 3
Documentation Standards
When documenting respiratory examination findings, the American Thoracic Society and European Respiratory Society emphasize that physical examination findings alone, including breath sound characteristics, are insufficient for diagnosis and must be confirmed with objective testing such as spirometry. 1, 4
The presence of quiet breath sounds combined with prolonged expiratory duration has a positive likelihood ratio greater than 5.0 for COPD when combined with hyperresonance. 1