The energy of phonation is supplied by expiration. Since the purpose of respiration is gas exchange, the phonatory function will be affected by this factor under certain conditions, such as sustained phonation with effort.
In order to study this, two experiments were performed.
(1) Measurement of the phonation time, sound pressure level, volume of expired air, F_EO₂ (fractional O₂ concentration of expired air) and F_ECO₂ (fractional CO₂ conce of ntrationexpired air) during sustained phonation.
(2) Mesurement of the PaO₂ (arterial O₂ etnsion), PaCO₂ (arterial CO₂ tension), pH, B. E. (Base Excess), HCO₃^- in the arterial blood during sustained phonation and during breath holding.
The following results were obtained:
(1) Continuous decrease of F_EO₂ and increase of F_ECO₂ were observed during sustained phonation.
(2) In the terminal stage of sustained phonation, the value of F_ECO₂ was similar to P_ACO₂ at the breaking point of breath holding.
(3) In easy phonation, phonation time and maximum F_ECO₂ as well as minimum F_EO₂ were correlated.
In falsetto phonation, however, such a correlation was not obtained.
(4) Decrease of PaO₂ and increase of PaCO₂ in the course of sustained phonation and breath holding.
(5) At the same point after initiation, PaCO₂ is higher and PaO₂ is lower in sustained phonation than in breath holding.
(6) In sustained phonation, B. E. was lower initially than at the terminal part of phonation, and sometimes HCO₃^- value was out of the “significance band”. This result suggests that in addition to respiratory factor, metabolic factor might also function during sustained phonation.
(7) Both in sustained phonation and in breath holding, alkalemia was present in the initial stage and acidemia in the terminal stage.
The results of the present study show that the respiratory factor in terms of gas exchange, influence sustained phonation to some extent.

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