The purpose of this brief article is to consider the significance of the research conducted by Iwarsson and Sundberg (1998), Iwarsson et al (1998) and Iwarsson (2001). Reading these three research reports in conjunction with one another may provide us with an insight into breathing methodology relevant to both speech therapy and singing teaching.
Iwarsson and Sundberg (1988) first examined the effects of lung volume on the vertical larynx position during phonation. This study reinforces the importance of understanding the interrelationship between breathing and the larynx as lung volume may well impact on vocal function. Of particular relevance is the existence of ‘tracheal pull’ and this study clearly explains the physiological impact of inhalation. ‘During inhalation, the lungs expand, not only laterally but also caudally, thus inducing a lowering in the torso of the bronchial tree as well as the diaphragm.’ (1988:159). This lowering of the bronchial tree is highly significant and Iwarsson and Sunberg (1998) cite earlier research by Macklin (1925) which found that the vertical position of the carina, (the point at which the trachea branches into the two mainstem bronchi) changed by 21mm between high and low lung volumes. This is a significant force exerted on the larynx and explains Zencker’s term ‘tracheal pull.’
Having synthesised this research, Iwarsson and Sundberg (1988) hypothesise that the degree of ‘tracheal pull’ will vary with lung volume. The researchers examined 33 non-singer subjects and asked them to expand their abdominal wall on the inhalation. Visual feedback was provided on a screen. The results showed that high lung volumes were associated with a lower larynx compared to lower lung volumes.
Building on this study further, Iwarsson et al (1998) by examining the impact of the ‘tracheal pull’. on the glottal source. The study cites Zenker et al (1964) which states that the tracheal pull is associated with a glottal abduction force. This was confirmed by the study of 24 non-singer subjects where it was shown that an increase in lung volume resulted in a higher degree of glottal abduction and glottal leakage.
Iwarsson (2001) then carried out another study looking at the impact of different breathing strategies on the degree of tracheal pull. In the Iwarsson et al study (1998) the subjects were asked to engage in abdominal breathing because it was believed that maximal lowering of the diaphragm would be facilitated as a result which in turn would create a greater degree of tracheal pull. In the (2001) study, Iwarsson compared two inhalatory positions; one with the abdominal wall tucked in on the inhalation and one with the abdominal wall ‘stuck out.’ Surprisingly, the abdomen out (abdominal breathing) position was associated with a higher laryngeal position than the abdominal wall tucked in.
Conclusion and Implications
We can cautiously conclude from these three studies that variations in lung volume can have a significant impact upon the glottal source with higher lung volumes triggering a greater degree of tracheal pull. This in turn results in a higher degree of glottal abduction and glottal leakage. With regards to hyperfunctional voices, this has implications for treatment and in singing voices it is relevant where hyperfuntionality can be heard in the singing tone. Although Iwarsson et al (1998) established a clear link between lung volume, tracheal pull and resultant laryngeal position, she was unable to establish a link between a specific breathing strategy and larynx position.