The purpose of this unit is to renew your understanding of basic anatomy and physiology concepts related to voice production. You probably learned many of these concepts in your undergraduate anatomy and speech science classes. We will also go beyond these basics to develop a more sophisticated understanding of voice production. In this slidecast, we will take a more in-depth look at respiration.
You will recall that there are three components to human voice: respiration, phonation, and resonance. If one or more of these aspects of voice production is inefficient or disordered, then the voice quality may be altered negatively. This is particularly true of respiration.
Note that there is an upper and a lower respiratory tract. As speech-language pathologists, we are mostly concerned with the upper tract, which contains the oral and nasal cavities as well as well as the pharynx and the larynx. The lungs and the lower half of the respiratory tract are very important, mostly for breathing for life but also for speech production in general.
In this picture you can imagine the path that air molecules take as they travel from the lungs up to the trachea and into the upper respiratory tract. The sound of the voice is shaped by each cavity that the air molecules pass through on their way up from the lungs. We will discuss this process more during our discussion about resonance.
You will remember from your speech science and anatomy and physiology classes that the respiratory system is generally incapable of independently exchanging air between the lungs and the external environment. External, musculoskeletal forces must act upon the various organs of the respiratory tract in order to achieve respiration. Remember that the lungs are attached to the thoracic cavity via the pleural membrane. When the ribcage expands and contracts, so do the lungs, and also the volume of air in the lungs. But you may wonder how the air actually gets into the lungs from the air outside the body. For this to occur, we need to remember Boyle’s law, which says that pressure and volume are inversely related. This means that when the ribcage expands, the lungs also expand, and the volume of air inside the lungs is less than that of the air outside the lungs. When this happens, the change in pressure causes the air molecules to rush into the lungs. When the ribcage contracts and the lung volume decreases, the air molecules are driven from the lungs by the excess pressure, and we exhale.
There are a number of muscles that help with respiration, particularly for speech. The most important muscle of inspiration is the diaphragm. Several muscles also aid in respiration. For deep breathing we use the external intercostal muscles to elevate and expand the rib cage. To a lesser extent, the internal intercostal muscles also help the external intercostals with ribcage elevation. Diaphragmatic breathing is the most effective in terms of taking in the lots of air upon inspiration. However, some people use other types of breathing. Thoracic (chest) breathing can result when people use their arm and shoulder muscles to assist with respiration. Clavicular (or shoulder) breathing results from the use of the neck muscles to aid in respiration. Breathing in this manner is highly ineffective, and is sometimes used by clients with severe respiratory breathing. On the other hand, some of us just get into the habit of not breathing deeply from the diaphragm. Take a minute to assess your own breathing. Are you breathing from down around your stomach, or are your chest and or shoulders rising a lot on each inhalation? A little chest/shoulder movement is okay, but if you have too much, you will need to work on your breathing to be a good model for your clients.
Expiratory muscles are generally employed during forced exhalations, like singing and some types of speaking. Otherwise, expiration is passive. The lungs are elastic and tend to want to snap back to their original resting position after they have been expanded by the ribcage. Physical properties such as the untwisting or “untorquing” of the ribs and gravity also contribute to passive expiration. But, when we want to get more bang for our buck, so to speak, we can extend or force an exhalation beyond that which is achieved by passive forces. We might do this during speech. In this case, the internal intercostal muscles are the most important muscle of forced expiration, and the transverse thoracic and abdominal muscles are also used. Take a minute to count as high as you can on a single breath of air. Don’t pass out or anything, but do take note of what happens as you count higher and higher. Can you feel your muscles working?
We all have certain quantities of air that we can breathe in, breathe out, and hold in our airways. Take a moment to focus on your breathing as I describe some of these measures of lung capacities. First, I’d like you to take a normal breath in, and then let it out. Don’t force it. This is your tidal volume. Now let’s discuss inspiratory reserve volume, or IRV. Take a regular breath in, and then inhale as much as you can beyond that point. This is the maximum amount of air you can inhale at the end of a tidal inspiration, and is your IRV. Your total lung capacity is the volume of air that can be held in the lungs and airways after a maximum inspiration. Now let’s focus on expiration. Take a normal breath in, then let it out. Now, keep forcing that air out, until you have exhaled all the air that you can. This is your expiratory reserve volume, or ERV. Even after you have exhaled all that you can, some air still remains in your lungs. This is your residual volume. The only time you may not have any air remaining in your lungs is if you have a punctured lung. In this case, you lung becomes separated from the ribcage, and it is a very painful thing, or so I’m told! Finally, I’d like you to take as much of a breath in as you can, just like you did for inspiratory reserve volume. Once you have inhaled as much as you can, exhale as much as you can, just like you did for expiratory reserve volume. The amount of air that you can exhale after inhaling as much as possible is your vital capacity. Why do we care about these measures? Well, it is quite possible that we may work with clients who have pulmonary disorders. We may need to work closely with pulmonologists, or at least know enough about these measures to understand their reports. Emphysema and Chronic Obstructive Pulmonary Disease are two such disorders in which breathing is disturbed and the patient may have poor voice quality. Can you think of any others?
In this slide I have listed some general information about how we breath for speech. Take a minute to pay attention to your own breathing. As you listen to me talk, you are most likely at rest, and the amount of air you exhale is probably a little longer than that you inhale. But as I am talking to you, I am having to use more forceful exhalations, and to exhale for longer in order to speak as much as I would like on one breath. So I am not relying on passive exhalation, but rather on the internal intercostals, transverse thoracic, and abdominal muscles. When we speak in general, if we are in good health and have good vocal habits, we use passive exhalation, then tidal volume, and then our expiratory reserve. If we try to speak on too much air or too little air, our vocal quality will seem weak or strained. For example, if I take in to much air, you can hear how my voice seems tense at first. But if I try to talk to long on a single breath of air, my voice will eventually sound strained, much like yours when you counted as high as you could.
Students often have some questions about respiration, particularly when it comes to actually measuring lung volumes. I encourage you to check out the Going Deeper page for some references and resources related to respiration. In particular, you can get instructions for how to make your own spirometer, a device that measures exhaled air volume. This is one such tool an SLP might use in clinical practice to encourage clients to use better breath support. Other links are related to learning about pulmonologists and Boyle’s law.
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