Lung Sounds and Respiratory Assessment
Introduction
Lung sounds, chest radiographs, arterial blood gases and their interpretation, can all be tricky. What’s more, they are often explored in isolation and seldom interpreted in the context of the history. As a student, this can be misleading and off putting. So how do you go about learning this?
The Hands-on Guide to Clinical Reasoning in Medicine does all this and more. It has been written keeping its audience in mind in a friendly, easy-to understand, easy to use, practical, hands-on style for students, junior doctors and nurse practitioners.
History taking, pulmonary examination, investigations, common presentations… we have them all covered.
For instance, have you ever considered integrating simple anatomy, physics and your imagination to not only understand but also predict the signs that occur in various pulmonary disorders?
Take lower lobe consolidation. Most of the lower lobe lies posteriorly on the chest wall (surface anatomy). Therefore all pathological signs will be found here! Consolidation is just a fancy name for solidification of the lung (imagination). Sound travels better in solids (physics), hence the vocal cord vibrations of “99” will be heard very clearly here causing increased vocal resonance. See how easy it was? Once you get the hang of this, you can start interpreting the signs all by yourself!
Topics covered include:
A novel and simple approach to history taking is illustrated where you start with concept maps of respiratory symptoms based on an anatomical or pathophysiological model. Figure 1 shows you an example for aetiology of chest pain.
Figure 1
Credit source: Irfan M, Hands-on Guide to clinical Reasoning in Medicine, Wiley-Blackwell; 1 edition (1 Feb. 2019)
Using this knowledge, you will then be shown how to come up with the differentials as you are collecting data in a very practical way.
This is also illustrated in action in all the clinical presentations in a workbook format. You will have space to record your thoughts or just have a pause to think it through, as you solve the problems with the author.
To a novice learning all the sounds, percussion notes and lists of conditions that they occur in, can be daunting. Trying to memorise lists separated from their clinical context is in fact pointless. So let me give you an introduction to how these signs and sounds are produced.
The book then puts all of them in the clinical context which makes it a lot easier to remember without having to memorise. A number of illustrations highlight the anatomy and rekindle your imagination to interpret the signs.
Lung sounds
- Vesicular breath sounds
The normal vesicular breath sounds are produced owing to turbulent airflow in the larger airways (tubes). It sounds like leaves rustling in a gentle breeze. In smaller airways the flow becomes more laminar and therefore does not produce any sound. In fact the term is misleading, since this sound does not arise from the ‘vesicles’ = alveoli.
Why don’t you try putting the stethoscope over your chest (or a friend’s… with consent) on the sides? Ask them to breathe through their mouth and take in “big deep breaths without holding their breath at any point”. You will notice that the inspiration sounds longer than expiration and there is no gap between the two.
If the intensity of vesicular breath sounds is reduced, it represents blockage in the respective larger bronchi or bronchioles supplying that part of the lung. For example, peri-bronchial oedema and alveolar exudates in right lower lobe consolidation cause diminished breath sounds in the lower posterior chest wall (remember the surface anatomy?). This can also happen in severe asthma when air is not at all being shifted owing to severe bronchospasm.
- Bronchial breath sounds
Now place the stethoscope over the manubrium or the interscapular region posteriorly. You can hear harsher sounds like blowing across the mouth of a bottle or pipe. The inspiration and expiration are equal in length with no gap in-between. This is called bronchial breathing. If it is heard in areas other than the aforementioned it is pathological.
For instance in left lower lobe consolidation, the affected lobe turns solid. We know that sound is better conducted in solids than air. Therefore turbulent airflow in the larger airways gets conducted better through the intervening solid lung tissue in the left lower posterior chest wall. This is heard as bronchial breathing.
The same explanation applies to the increased vocal resonance and egophony seen in consolidation.
- Adventitious sounds (as opposed to normal breath sounds)
In 2016, the European Respiratory Society Task Force, suggested a common nomenclature for lung sounds in order to eliminate confusion among clinicians (Pasterkamp et al., 2016). Table 1 gives a brief overview.
Table 1: ERS Proposed Lung Sound Nomenclature.
Credit Source: Pasterkamp, H. et al. (2016)
| Term | Pitch | Amplitude (Loudness) | Duration | Replacement for |
|---|---|---|---|---|
|
Coarse crackles
e.g. bronchiectasis |
Discontinuous low |
High |
Longer compared to fine |
Rales |
|
Fine crackles
e.g. Interstitial lung disease |
Discontinuous high |
Low |
Brief |
Crepitations |
|
Wheezes |
Continuous Low |
Musical quality |
80+ ms |
Rhonchus |
|
Wheezes |
Continuous High |
Musical quality |
80+ ms |
Also simply called wheezes – polyphonic or monophonic |
Fine crackles are further sub-divided according to their timing i.e. inspiratory or expiratory. Small airways disease like COPD causes early inspiratory crackles and alveolar disease like ILD or pulmonary edema causes late or pan-inspiratory crackles.
Chest radiographs can be easily understood in terms of white areas and black areas. Did you know there are three main differentials for white areas and black areas are due to more air or less blood flow?
Arterial blood gases, the bane of everyone’s life! Type 1 or type 2, hypoxic or hypercapnic, respiratory failure, so much confusion. Honestly, it does not have to be this way. All you need to know is that one is due to a problem with oxygenation and the other is to do with ventilation. Beautiful illustrations and an intuitive flow chart will solve this vexing problem once and for all!
These include topics like:
- Chronic cough
- Acute breathlessness
- Acute chest pain
- Acute haemoptysis
Plenty of clinical scenarios will seamlessly integrate medical knowledge with the principles of decision-making, ensuring that you become a thinking clinician. These scenarios are played out in an engaging conversational style with two imaginary students while the reader solves the problems with them.
Ready for a helping hand? You can find out all about Pulmonology right now and buy the Hands-on Guide to Clinical Reasoning in Medicine here.
Not quite sure yet?
See all the other sections here..
- Cardiology
- Neurology
- Gastroenterology
- Endocrinology and Diabetes Mellitus
- Geriatric Medicine
- Nephrology
- Rheumatology
- Common Clinical Conditions
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