Transcutaneous PCO 2 monitoring with hyperventilation during phonation in vocal cord paralysis Hiroshi Miyazaki *, Toshiro Umezaki, Hiroyuki Yamashita, Tomoya Yamamoto, Sohtaro Komiyama Department of Otorhinolaryngology, Faculty of Medicine, Kyushu University, 3-1-1 Maidashi, Higashiku, Fukuoka 812-8582, Japan Received 20 June 2001; received in revised form 4 February 2002; accepted 15 March 2002 Abstract Objective: Hyperventilation during phonation is one of the causes of fatigue in-patients with vocal disorders. Methods: The transcutaneous (tc) PCO 2 during phonation in 8 normal subjects and 12 patients with unilateral vocal cord paralysis was measured. Cases were further divided into two groups by the degree of the tcPCO 2 decrease during phonation. Patients with a tcPCO 2 decrease less than 3.4 mmHg during phonation were classified as group 1 (G1). Patients with a tcPCO 2 decrease larger than or equal to 3.4 mmHg during phonation were classified into group 2 (G2). Results: The average changes in tcPCO 2 in the G1 cases was not significantly different from that in normal subjects. The decrease in tcPCO 2 during phonation in the six G2 cases was 10.79 /6.2 mmHg, and was significantly different from that in normal subjects (P B/0.01, t -test). The decrease of tcPCO 2 during phonation in both G1 and G2 cases improved significantly after surgical treatment. Easy fatigability during phonation in two G1 cases and five G2 cases improved. Conclusions: The decrease in tcPCO 2 during phonation in cases of unilateral vocal cord paralysis is well correlated with easy fatigability. It is clinically useful to classify cases into two groups using the criteria of a less than 3.4 mmHg or larger than or equal to 3.4 mmHg decrease in tcPCO 2 . These results also suggest that hyperventilation is one major cause for easy fatigability during phonation in cases with unilateral vocal cord paralysis. TcPCO 2 changes during phonation are useful in evaluating hyperventilation and the effect of treatment. # 2002 Published by Elsevier Science Ireland Ltd. Keywords: Vocal disorder; Hyperventilation; Transcutaneous PCO 2 ; Vocal cord paralysis 1. Introduction Patients with vocal cord paralysis frequently complain of easy fatigability during phonation. Hyperventilation due to the vocal disorder may be one of the cause for easy fatigability. However, a correlation has not been proven. In a previous report, using real time Transcu- taneous (tc) partial pressure of carbon dioxide (PCO 2 ) monitoring, one cause of easy fatigability during phona- tion in patients with vocal cord paralysis was shown to be hyperventilation accompanied by a decrease in the tcPCO 2 level [1]. In this study, tcPCO 2 during phonation was evaluated statistically to compare the effect of hyperventilation on easy fatigability between patients with unilateral vocal cord paralysis versus its effect on normal subjects. The feasibility of using real time tcPCO 2 recordings as a clinical indicator of vocal cord dysfunction was also examined. 2. Materials and methods 2.1. Patients and normal subjects Twelve cases of unilateral vocal cord paralysis (3 males and 9 females; Ages 36  /77 years; mean age 60) were studied (Table 1). Three out of twelve cases were idiopathic, and nine included one thyroid cancer case (no surgery), three thyroid cancer cases (a complication of surgery), two benign thyroid tumor cases (a compli- cation of surgery), one esophageal cancer case (a complication of surgery), one thoracic aneurysm case (a complication of surgery), one neurinoma case (a complication of surgery). All etiologies of vocal cord * Corresponding author. Tel.:  /81-92-642-5668; fax:  /81-92-642- 5685 E-mail address: hmiyazak@ymg.urban.ne.jp (H. Miyazaki). Auris, Nasus, Larynx 29 (2002) 277 /282 www.elsevier.com/locate/anl 0385-8146/02/$ - see front matter # 2002 Published by Elsevier Science Ireland Ltd. PII:S0385-8146(02)00017-2