Name That Tune: An Introduction to Auscultating, Differentiating and Assessing Lung Sounds

It’s a hot summer night, and your unit has been working nonstop when a call comes in: “Unit 172, respond to 3317 Court Street, 1st floor; 62-year-old male, chest pain, difficulty breathing.” On arrival, you and your partner find an obese gentleman in the tripod position, gasping for breath. He has a nasal cannula on, with 30 feet of tubing going to an oxygen tank in an adjacent room. On the table beside him, you notice three different types of inhalers and an ashtray full of cigarette butts. Your partner begins to place the bell of his stethoscope in various places around the man’s expansive, fat-padded chest. Just as you are beginning to doubt that he is hearing anything, a perplexed look crosses his face, and he asks: “Does this sound like rales to you, or rhonchi?”

One of the most important and difficult skills that an EMS provider must learn and master is assessment of lung sounds. This includes not only becoming skilled at knowing where to place a stethoscope to listen correctly to the lungs and identify the various sounds, but also what potential problems they indicate and how to properly address their presence in the field. Correct recognition of lung sounds and the subsequent appropriate treatment can make all the difference in managing patients with respiratory compromise.

From the early 1800s, when René T. H. Laënnec invented the first crude stethoscope, medical providers have used auscultation of the chest to enhance their ability to properly examine patients.1 Prior to that, doctors placed their ears directly on patients’ chests to hear lung sounds.

EMS providers now have access to cutting-edge technology to help them better recognize and differentiate lung sounds. Stethoscopes have advanced significantly since the early days of Laënnec. Current models are available with enhanced acoustics and built-in microphones designed to amplify sounds several times louder than traditional scopes. Bell-head configurations allow the user to alternate between low, middle and high tones by simply adjusting the pressure used to hold the scope to the skin. In addition to enhanced equipment, EMS providers are also armed with advanced resources to better train themselves in lung sound recognition. A wide variety of sample breath sounds can be found on media ranging from audio CDs distributed with textbooks to Internet-based downloadable WAV files. As computer-programmable training manikins become more affordable, greater numbers of prehospital providers can gain invaluable practice locating and identifying critical changes in patients’ respiratory patterns in a classroom setting.

Appropriate Placement

Webster defines auscultation as “the act of listening to sounds arising within organs [as the lungs] as an aid to diagnosis and treatment.” The stethoscope not only amplifies sounds, it also filters out unwanted noise, if positioned correctly. Of primary importance in properly auscultating a patient’s lung sounds is the placement of the stethoscope on the chest wall. If it is incorrectly placed, you may hear body processes other than breath sounds, such as gastrointestinal activity, or nothing at all, especially if it is placed over bone.

Knowing your way around the thoracic cavity and its organs is most helpful in remembering the locations to best assess lung function. Some fundamentals of anatomy to remember include:

• Although of similar size, the right lung has three lobes and the left has two.

• From the anterior (front) perspective, the lungs extend from the top of the rib cage, just above the clavicle (collarbone), down to about the level of the sixth intercostal space (6th ICS).

• The diaphragm defines the bottom of the thoracic cavity. To allow for the space needed by the abdominal organs, the shape of this muscular wall is normally concave when relaxed, pressing up against the lungs.

• Moving from anterior to posterior (front to back), the diaphragm follows the curvature of the rib cage and allows the lungs to reach the level of the 10th thoracic vertebra (T-10) on the back or dorsal side of the torso (see Figure 1 on page 78).

• While both lungs should extend equally to the lateral (side) walls of the chest, their medial (center) surfaces are more irregular. The left lung bears a space (the cardiac notch), and both sides have grooves for the arteries and veins leading into and out of the heart. The mediastinum—the area that contains the heart and great vessels—separates the lungs and places each into its own pleural cavity.

• The scapulae (shoulder blades) cover the upper right and left “corners” of both lungs, and the spinal column forms an approximately 1-inch-wide bony border straight down the middle line of the back.

While the shape and size of the lungs will change, especially during the inhalation phase of respiration as the lung tissue expands to fill whatever areas it can as the pressure gradient decreases, the above parameters do not change. With this in mind, you should not place the bell of your stethoscope over the sternum, unless you want to hear heart tones, or below the 6th ICS, where you will hear intestinal sounds.

Ideally, it is recommended that the posterior chest (back) be used for auscultation, as there is less muscle and bone to dissipate the sounds.2 Locating the positions numbered in Figure 2 (see page 79) on the patient’s back will provide a complete evaluation of lung sounds. Working in this pattern will ensure that you have not missed a section.

Some additional tips regarding the mech-anics of listening to the patient’s lungs are:

• Instruct patients to breathe with their mouth open to decrease upper airway resistance and allow for better transmission of breath sounds. Make sure the patient doesn’t breathe too fast when taking deep breaths, as it may cause them to hyperventilate.

• The stethoscope must be in firm contact with the skin. Listening over clothing, or even a lot of chest hair, can sound like fluid in the lungs.

• Remember that during inspiration, the lungs only go down to the level of approximately the mid-back.

• When listening on the back, place the stethoscope head between and below the scapulae, not over them.

• Make sure that you listen throughout the full respiratory cycle, as some adventitious lung sounds are heard at the end of either the inspiratory or expiratory phases.

• Sit your patient up, if possible, and pay special attention to the lower lung fields when assessing for fluid collection. In addition to making it easier for your patient to take a deep breath, unless the edema is severe enough, someone who has been supine for a while may not have enough fluid in any lobe to be noticeable. Let gravity work for you.

Types of Lung Sounds

Lung sounds are typically broken down into three categories:

• Normal (vesicular)

• Decreased or absent

• Abnormal (adventitious)

Normal lung sounds have no sign of any impedance in respiration. These sounds generally can be heard from the collarbones to below the rib cage.

Decreased lung sounds are typically due to a reduction in the volume of airflow in the lungs. This can be caused by several different factors, including: increasing thickness of the chest wall, air or fluid around the lungs, and/or overinflation of the lung.

There are several types of abnormal lung sounds, but the most common are wheezes, rales (crackles), rhonchi and pleural (friction) rub. These sounds are often audible to the unaided ear, but should be assessed with the aid of a stethoscope.

Wheezes are caused by air flowing rapidly through narrowed airway passages, commonly in the upper airways, either due to bronchospasm, which is constriction of smooth muscle that surrounds the airways, or inflammation of the airways themselves. Wheezes are usually attributed to asthma, bronchiolitis or bronchitis, but can also be seen in emphysema patients, especially when an infection is present. Wheezes may also accompany viral infections, allergic reactions, cystic fibrosis and tuberculosis. This narrowing of the airways causes high-pitched sounds, most commonly on expiration, but that are sometimes audible on inspiration as well. Wheezing can be heard over all lung fields or be isolated to specific lobes.

Rales are small bubbling or fine clicking sounds made when air is forced into collapsed alveoli and/or in the presence of fluid in the alveoli and/or bronchioles. Rales are most commonly compared to the sound made when rubbing hair between your fingers. Rales usually occur at the peak of inspiration; however, crackles may also occur throughout the respiratory cycle if there is a significant amount of fluid present in the airways. They may not appear with each inspiration/expiration, and may be mild, or even clear with coughing. Moderate or severe crackles may be a symptom of bronchitis, pneumonia, pulmonary edema or congestive heart failure (CHF). Rales may also present as fine crackles (higher pitched), but will become increasingly coarse (lower pitched) as the patient’s condition worsens.

Rhonchi are low-pitched, sonorous, rumbling, bubbling or gurgling sounds. These types of sounds are most commonly attributed to air being forced through fluid obstructions of the large airways. Rhonchi can occur during any phase of the respiratory cycle, and can possibly clear themselves with effective coughing. Rhonchi are commonly heard in patients with chronic obstructive pulmonary disease (COPD)/chronic bronchitis and pneumonia.3

Pleural rub, or friction rub, occurs when there is fluid in the pleural space between the lung tissue and the interior chest wall. The collection of fluid in this “potential space” decreases the amount of room needed by the lungs for expansion during the inspiratory phase of respiration. There is commonly a grating, rubbing type of sound as the visceral (lung) and parietal (chest wall) pleura rub against each other. This sound may be heard in patients with pleurisy, tuberculosis, pneumonia and cancer of the lung, as well as after a lobectomy or other thoracic surgery. Pleural rub is often associated with increasing pain on deep inspiration.

Special Situations

Some patient populations can prove challenging with regard to proper auscultation and assessment of their lung sounds. These are examined below.

Clinically obese patients

In addition to other health issues related to their size, these patients are often susceptible to respiratory problems due to the increased weight on their chests and increased respiratory effort required to accomplish normal tasks. Remember that breath sounds may be diminished or muffled due to the patient’s size. If possible, placing the patient in an upright and forward posture will help to prevent the extra weight of the patient’s chest and abdomen from inhibiting lung expansion. Auscultation should be completed from the back, as there is less fat padding there than in the anterior chest.

Geriatric patients

An aging respiratory system experiences a loss of lung elasticity and a decrease in chest wall flexibility. Make sure you ask about and look for evidence of pulmonary surgeries before assuming absent lung sounds are an acute condition. Some disease processes, especially cancer and tuberculosis, may have necessitated the removal of a lobe or two. Older patients tend to have a higher susceptibility for pneumonia and worsening of COPD or asthma. Because cardiac conditions can often mimic COPD, do not be fooled into thinking that your elderly patient’s inhaler is just not working when she continues to wheeze.

Pediatric patients

The idiosyncrasies of anatomy in the younger pediatric population (a larger epiglottis, larger tongue, narrower airway, etc.), as well as some of the maladies that may specifically affect them (croup, epiglottitis, etc.), can test the most experienced prehospital providers. As a pediatric patient matures and grows, the methods for evaluating respiratory function are somewhat dependent on the age and severity of the patient’s condition.

Complete your assessment on sleeping infants before waking them. Smaller chest cavities allow sound waves to travel more quickly and make the location and differentiation of adventitious lung sounds more difficult. Using a pediatric stethoscope and listening at the axillary chest wall will help combat the potential for mistaken identification.

Older toddlers and preschoolers may be reluctant to allow an EMS provider to listen to their lungs. You may have to resort to using the parent’s hand, or even the patient’s hand, to “assist” you in placing the stethoscope. Demonstrating the nonpainful nature of the procedure on a willing family member will also go a long way to ensuring cooperation.

School-age children and adolescents will require more explaining as to why the assessment is necessary. The older the child, the more modesty becomes an issue. If the patient’s complaints are not medically urgent, try to respect the need for discreet moving and removing of clothing.

Conclusion

From the days preceding the invention of the stethoscope, auscultation and recognition of lung sounds have been essential diagnostic tools. Today, accurate assessment of lung sounds is an integral component of the prehospital medical evaluation process for all levels of care. As an EMS provider, you should not only use this tool to obtain a better impression of the patient presenting with acute respiratory difficulty, but for every patient you encounter, especially in patients where auscultation may be a unique challenge. Recognizing and addressing the special needs of these patients when not in distress can help ensure that you adequately diagnose and treat their condition(s) when faced with a true emergency.

The dedicated routine of auscultating every patient’s lungs, no matter what their chief complaint may be, is one of the best ways to become more proficient and better able to discern the various forms of adventitious lung sounds. Prompt and accurate recognition of these sounds can make all the difference in your overall assessment and treatment modalities.

References

1. National Library of Medicine. Breath of Life: Asthma Under the Skin, 1999. www.nlm.nih.gov/md/breath/breath_exhibit/Asthma/asthmaskin/IIIBs1.html).
2. York Region Base Hospital Program, Ontario, CA. Advanced Chest Assessment, 2002. www.yrbhp.markham.on.ca/pdfs/Adv_Chest/ChestCME_06-02.pdf.
3. Health Central (excerpts from A.D.A.M. Software, Inc, 1998) www.healthcentral.com/mhc/top/003323.cfm.

Online Lung Sound Resources

• MedStudents Lung Sounds: www.medstudents.com.br/pneumo/lungsounds/lungsou.htm

• Pulmonary Rehabilitation Associates, LLC: www.pulmonaryrehab.com/lung_sounds.htm

• University of Iowa Health Care:www.vh.org/adult/provider/internalmedicine/LungSounds/LungSounds.html

• National Library of Medicine-Medline: www.nlm.nih.gov/medlineplus/ency/article/003323.htm

• University of California Davis Health System: http://alice.ucdavis.edu/IMD/420C/sounds/lngsound.htm

• The R.A.L.E. Repository: http://www.rale.ca/

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