Clin. Otolarjngol. 1992, 17, 497-500
Teflon injection for unilateral vocal cord paralysis and its effect on lung function JOHN K.S.WOO*, C.A.VAN HASSELT* & H.S.CHANT *Division of Otorhinolaryngol(~~~1, Departmenr of Surgery, and ?Department of Medicine. Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, N T . Hong Kong Accepted for publication 10 June 1992 WOO J . K . S . , V A N IIASSELT C . A . & C H A N
H.S.
(1992) Clin. Otolaryngol. 17, 497-500
Teflon injection for unilateral vocal cord paralysis and its effect on lung function We present a prospective analysis of the lung function of 22 patients with unilateral vocal cord paralysis before and after Teflon injection. In the majority of patients the vocal cord paralysis was caused by an underlying malignant condition. Full spirometric and flow-volume loop studies demonstrated an increase in airway resistance after Teflon injection which was not clinically evident. The improvement in symptom score for aspiration was greater than that for dysphonia. Keywords unilareral vocal cord paralysis
Teflon injection
Unilateral vocal cord paralysis can cripple an individual by rendering the larynx incompetent. When compensation by the unparalysed cord is incomplete, Teflon injection of the paralysed cord is a simple and effective treatment.' The majority of patients requiring Teflon injection are elderly with poor lung function and suffer from an underlying malignant condition. While improving laryngeal competence. Teflon injection will inevitably narrow the glottic opening and thereby might be expected to increase airway resistance. Moreover, the procedure is most often performed under general anaesthesia which may further compromise lung function. While several large series have reported a minimal complication rate, isolated cases of respiratory obstruction after Teflon i n j e ~ t i o n ,or ~ , ~complications related to general anaesthesia4have been reported from time to time. This study investigates the effects of Teflon injection on symptoms and respiratory function, and examines the safety of the technique in a typical group of patients.
Materials and methods In order to determine the efficacy of Teflon injection for alleviating symptoms and its effect on lung function, a prospective study was designed jointly by the Division of Otolaryngology of the Department of Surgery and the Respiratory Unit of the Department of Medicine in the Correspondence: C.A.van Hasselt, Division of Otolaryngology, Department of Surgery. Chinese University of Hong Kong, Prince of Wales Iiospital, Shatin, NT, Hong Kong.
airway resistance
Prince of Wales Hospital, Hong Kong. The study included all patients who underwent Teflon injection for a unilateral vocal cord palsy between February 1990 and May 1991. Each subject had full spirometric and flow-volume loop studies performed within the 48 hours preceding Teflon injection and repeated within a 24-hour period after the procedure. Standard spirometric and flow-volume loop studies were performed using the Gould 5OOOiv Computerized Pulmonary Function Laboratory. Additional data on airway resistance (Raw) was obtained in cooperative patients using the Gould 2800 Autobox-computerized whole body plethysmograph. Each expiration-inspiration manoeuvre was performed at least 3 times. The best result achieved was recorded for analysis. A tubeless technique of general anaesthesia was utilized, sedation being maintained via an intravenous infusion of p r ~ p o f o l This . ~ technique, coupled with suspension microlaryngoscopy, offers an unobstructed view of the larynx. A Brunings Syringe was used to inject the Teflon paste. All the procedures were performed by one surgeon (JKSW). The symptom scores for aspiration and dysphonia were graded by the patients before and after the injection (Table 1). The flow, volume and resistance parameters before and after injection were statistically analysed using a paired t-test.
Results During the study period, 24 patients with unilateral vocal cord palsy were scheduled to undergo Teflon injection. Two
491
498 J.K.S. Woo et a1
Table 1. Method of scoring symptoms Aspiration No aspiration Aspiration occasionally with fluid Aspiration frequently with fluid Aspiration frequently even with semisolid food
0
I 2 3
r
\
Dysphonia
0
2
I
3
Aspi ration scores
Normal voice Mild hoarseness Moderate hoarseness Aphonia
0 1 2 3
/
Figure 2. Aspiration scores A,before and 0, after injection.
after injection. One patient required a second Teflon injection in order to achieve improved glottic closure.
Table 2. Aetiology of vocal cord paralysis Aetiology
Number
Discussion
Oesophageal carcinoma Bronchogenic carcinoma Nasopharyngeal carcinoma* Carcinoma of thyroidt Carcinoma of breast with lung metastasis Posterior fossa meningioma (post-surgery) Right innominate artery aneurysm Aortic arch aneurysm
I1 7
Most patients were elderly males suffering from a left cord palsy with oesophageal carcinoma being the commonest cause for the paralysis followed by bronchogenic carcinoma
Total
24
1 1 1 1 1 1
Table 3. Difference in lung function before and after injection Indicates
Parameter
Trend
P-value
Flow
FEV, FEVJFVC FEF25Yo FEFSOYo FEF75% PEF F1F50% PI F
Decrease Decrease Decrease Decrease Decrease Decrease Decrease Decrease
0.0067 0.0049 0.0046 0.0186 0.4667 0.0003 0.01 1 I 0.0002
FVC
TLC RV RVITLC FRC ERC IC
Nil Nil Nil Nil Nil Nil Nil Decrease
0.710 0.428 0.440 0.530 0.668 0.864 0.354 0.043
Raw
Increase
0.0 164
*Excluded-failed to be injected due to severe trismus. tExcluded-failed to cooperate with the flow-volume loop study.
patients were excluded (Table 2 ) leaving only 22 patients for analysis. The age and sex distributions of the subjects are shown in Figure I . The underlying causes of the vocal cord paralyses are listed in Table 2. There were 20 left and 4 right cord palsies in the study group. Symptom scores improved for both aspiration (Figure 2) and dysphonia (Figure 3 ) as a result of the injection. No patient complained of dyspnoea after the procedure. Lung function parameters, before and after Teflon injection, are shown in Tables 3-5. There were no complications associated with the procedure. All patients were able to leave hospital 2 or 3 days
+ m
e
7
+
E 6 B 5 b
4
5 2
3 2
n
31-40
41-50
51-60
61-70
71-80
81-90
Age group
Figure 1. Sex and age distribution. Male : female 16 : 6; age range 39-84, median 65.
vc
(Analysed using paired f-test).
vc
I n "
Airway resistance
FEV, FVC FEF25% FEFSOYo FEF75Yo PEF FIF50Yo PIF
10 9 ._5
Volume
TLC RV FRC ERC IC Raw
Forced expiratory flow in 1 second. Forced vital capacity. Forced expiratory flow at 25% expiration. Forced expiratory flow at 50% expiration. Forced expiratory flow at 75% expiration. Peak expiratory flow. Forced inspiratory flow at 50% inspiration. Peak inspiratory flow. Vital capacity. Total lung capacity. Residual volume. Functional residual capacity. Expiratory reserve capacity. Inspiratory capacity. Airway resistance.
Teflon injection for vocal cord paralysis and its effect on lung 499
Table 4. Preoperative and post-operative FEVl, FVC, FEVl/FVC values
Table 5. Preoperative and post-operative RV, TLC, RViTLC values
Post-operative TLC (1)
Preoperative Case
__
1.33 1.51 1.11 3.25 1.20 1.41 0.99 0.58 1.18 1.42 0.92 1.11 1.00 0.87 1.75 1.73 1.62 1.04 1.66 2.07 1.88 1.97
1 2 3 4 5 6 7 8 9 10 I1 12 13 14 15 16 17 18 19 20 21 22
1.70 1.91 1.63 3.60 1.60 1.90 2.25 0.80 1.57 1.83 1.90 1.41 2.24 1.09 2.20 2.21 2.10 1.29 2.30 3.00 2.74 2.19
1.06 1.42 1.05 2.95 0.98 1.63 0.71 0.48 1.24 1.49 0.88 1.15 0.89 0.95 1.55 1.68 1.59 1.14 1.68 1.88 1.72 1.97
78 79 68 90 75 74 43 72 75 78 48 78 44 79 78 78 77 80 72 69 68 90
1.54 1.79 1.67 3.71 1.34 1.89 2.17 0.68 1.71 1.90 1.87 1.43 2.05 1.31 2.30 2.00 2.16 1.32 2.35 2.98 2.67 2.30
1
67 78 63 79 73 85 33 71 72 78 47 81 43 73 67 83 73 86 71 63 64 70
2 3 4 5 6 7 8 9 10
II 12 13 14 15 16 17 18 19 20 21 22
(Table 2 ) . It is not surprising that most of the patients were smokers, and a majority had chronic obstructive airways disease and compromised lung function preoperatively (Table 3 and 4). If the larynx regains competence after Teflon injection, aspiration will be prevented and dysphonia improved. However, in some cases dysphonia may persist because of mucosal damage from the injection. There was greater symptomatic improvement for aspiration than for dysphonia in this group of patients (Figures 2 and 3). A statistically significant decrease in all flow parameters except F E F 75% (Forced Expiratory Flow at 75% expiration) was observed in the post-injection results. These results reflect a definite increase in airway resistance after Teflon injection of the paralysed cord. This might be expected as Teflon injection narrows the glottis. In contrast
P
0
I
2 Dysphonio scores
Figure 3. Dysphonia scores A, before and
0, after injection.
3
0.65 1.63 1.44 0.85 1.32 1.06 1.09 0.69 1.67 1.37 2.40 1.79 2.90 2.00 3.22 1.97 2.34 1.68 2.58 4.28 3.51 2.94
2.40 3.67 3.07 4.69 2.92 2.97 3.39 1.50 3.35 3.20 4.30 3.25 5.30 3.16 5.55 4.23 4.49 3.00 4.89 7.44 6.29 5.18
27 44 47 18
45 36 32 46 50 43 56 55 55 63 58 47 52 56 53 58 56 57
0.66 1.52 0.64 1.62 0.99 I .47 1.28 0.99 2.25 2.95 2.60 1.99 2.33 2.14 2.60 2.06 1.84 2.29 2.67 2.67 3.18 1.85
2.20 3.40 2.39 2.33 2.33 3.36 3.45 1.71 3.98 4.85 4.49 3.50 4.45 3.45 4.94 4.06 4.09 3.61 5.04 5.88 5.85 4.17
RViTLC
(%I 30 45 27 42 42 44 37 58 57 61 58 57 52 62 53 51 45 63 53 45 54 44
to our findings, Kashima observed improvement in inspiratory as well as expiratory flow rates following Teflon injection.6 It is interesting to note that the parameters which are indicators of large airway resistance show a highly significant change. Volume parameters on the other hand, which do not necessarily vary with airway resistance, remained unchanged. The increase in overall airway resistance as reflected by the Raw value (Table 3), is the most accurate clinical method of measuring airway resistance, and provided an excellent counter check for the reliability of the results. M o s t patients in this study had incurable disease with a limited life expectancy. Therefore we did not subject them to subsequent spirometric studies to evaluate the long-term effects of Teflon injection, as the intention was to disturb the patients as little as possible.
Conclusion Vocal cord palsy treated by Teflon injection under general anaesthesia is a safe, effective and worthwhile procedure even for elderly patients with terminal malignancy. By improving laryngeal function, this simple procedure enhances the quality of life of these unfortunate patients. Although a significant increase in airway resistance was shown after Teflon injection, the change was not sufficient to cause symptomatic airway obstruction.
500
J.K.S. Woo et a1
Acknowledgements The authors would like thank the staff of the Pulmonary Function Laboratory of the Princc of Wales Hospital for their help with the pulmonary function testing and Miss Elsie Chu for preparing the manuscript.
References I GRIFFINS.M.. CHIJNC S.C.S., VAS HASSELTC.A. & LI A.K.C. (1992) Late swallowing and aspiration problems after oesophagectomy for cancer: malignant infiltration of the recurrent laryngeal nerves and its management. Surgery (in press)
2 BATESG.J., CURLEYJ.W. & WAKIIM.E. (1984) Respiratory obstruction following vocal cord injection of Teflon paste. Anaesthesia 39, 1232-1234 3 EJNELLH . , MANSSONI., BAKEB. & STENEIORG R. (1984) Laryngeal obstruction after Teflon injection. Acfa Ofolaryngol. 98, 374-379 4 BODENHAM A,, LATIMER R . & BETHUNE D. (1987) Respiratory obstruction following vocal cord injection. A complication on induction of anaesthesia. Anaesthesia 42, 289-292 5 AUN C.S.T., I IOUCHTON I.T., So H.Y ., VAN HASSELT C.A. & OH T.E. (I 990) Tubeless anaesthesia for microlaryngeal surgery. Anaesthesia Intensive Care 18, 497-503 6 KASHIMAH . K . (1984) Documcntation of upper airway obstruction in unilateral vocal cord paralysis: flow-volume loop studies in 43 subjects. Laryngoscope 94, 923-937
Teflon injection for unilateral vocal cord paralysis and its effect on lung function JOHN K.S.WOO*, C.A.VAN HASSELT* & H.S.CHANT *Division of Otorhinolaryngol(~~~1, Departmenr of Surgery, and ?Department of Medicine. Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, N T . Hong Kong Accepted for publication 10 June 1992 WOO J . K . S . , V A N IIASSELT C . A . & C H A N
H.S.
(1992) Clin. Otolaryngol. 17, 497-500
Teflon injection for unilateral vocal cord paralysis and its effect on lung function We present a prospective analysis of the lung function of 22 patients with unilateral vocal cord paralysis before and after Teflon injection. In the majority of patients the vocal cord paralysis was caused by an underlying malignant condition. Full spirometric and flow-volume loop studies demonstrated an increase in airway resistance after Teflon injection which was not clinically evident. The improvement in symptom score for aspiration was greater than that for dysphonia. Keywords unilareral vocal cord paralysis
Teflon injection
Unilateral vocal cord paralysis can cripple an individual by rendering the larynx incompetent. When compensation by the unparalysed cord is incomplete, Teflon injection of the paralysed cord is a simple and effective treatment.' The majority of patients requiring Teflon injection are elderly with poor lung function and suffer from an underlying malignant condition. While improving laryngeal competence. Teflon injection will inevitably narrow the glottic opening and thereby might be expected to increase airway resistance. Moreover, the procedure is most often performed under general anaesthesia which may further compromise lung function. While several large series have reported a minimal complication rate, isolated cases of respiratory obstruction after Teflon i n j e ~ t i o n ,or ~ , ~complications related to general anaesthesia4have been reported from time to time. This study investigates the effects of Teflon injection on symptoms and respiratory function, and examines the safety of the technique in a typical group of patients.
Materials and methods In order to determine the efficacy of Teflon injection for alleviating symptoms and its effect on lung function, a prospective study was designed jointly by the Division of Otolaryngology of the Department of Surgery and the Respiratory Unit of the Department of Medicine in the Correspondence: C.A.van Hasselt, Division of Otolaryngology, Department of Surgery. Chinese University of Hong Kong, Prince of Wales Iiospital, Shatin, NT, Hong Kong.
airway resistance
Prince of Wales Hospital, Hong Kong. The study included all patients who underwent Teflon injection for a unilateral vocal cord palsy between February 1990 and May 1991. Each subject had full spirometric and flow-volume loop studies performed within the 48 hours preceding Teflon injection and repeated within a 24-hour period after the procedure. Standard spirometric and flow-volume loop studies were performed using the Gould 5OOOiv Computerized Pulmonary Function Laboratory. Additional data on airway resistance (Raw) was obtained in cooperative patients using the Gould 2800 Autobox-computerized whole body plethysmograph. Each expiration-inspiration manoeuvre was performed at least 3 times. The best result achieved was recorded for analysis. A tubeless technique of general anaesthesia was utilized, sedation being maintained via an intravenous infusion of p r ~ p o f o l This . ~ technique, coupled with suspension microlaryngoscopy, offers an unobstructed view of the larynx. A Brunings Syringe was used to inject the Teflon paste. All the procedures were performed by one surgeon (JKSW). The symptom scores for aspiration and dysphonia were graded by the patients before and after the injection (Table 1). The flow, volume and resistance parameters before and after injection were statistically analysed using a paired t-test.
Results During the study period, 24 patients with unilateral vocal cord palsy were scheduled to undergo Teflon injection. Two
491
498 J.K.S. Woo et a1
Table 1. Method of scoring symptoms Aspiration No aspiration Aspiration occasionally with fluid Aspiration frequently with fluid Aspiration frequently even with semisolid food
0
I 2 3
r
\
Dysphonia
0
2
I
3
Aspi ration scores
Normal voice Mild hoarseness Moderate hoarseness Aphonia
0 1 2 3
/
Figure 2. Aspiration scores A,before and 0, after injection.
after injection. One patient required a second Teflon injection in order to achieve improved glottic closure.
Table 2. Aetiology of vocal cord paralysis Aetiology
Number
Discussion
Oesophageal carcinoma Bronchogenic carcinoma Nasopharyngeal carcinoma* Carcinoma of thyroidt Carcinoma of breast with lung metastasis Posterior fossa meningioma (post-surgery) Right innominate artery aneurysm Aortic arch aneurysm
I1 7
Most patients were elderly males suffering from a left cord palsy with oesophageal carcinoma being the commonest cause for the paralysis followed by bronchogenic carcinoma
Total
24
1 1 1 1 1 1
Table 3. Difference in lung function before and after injection Indicates
Parameter
Trend
P-value
Flow
FEV, FEVJFVC FEF25Yo FEFSOYo FEF75% PEF F1F50% PI F
Decrease Decrease Decrease Decrease Decrease Decrease Decrease Decrease
0.0067 0.0049 0.0046 0.0186 0.4667 0.0003 0.01 1 I 0.0002
FVC
TLC RV RVITLC FRC ERC IC
Nil Nil Nil Nil Nil Nil Nil Decrease
0.710 0.428 0.440 0.530 0.668 0.864 0.354 0.043
Raw
Increase
0.0 164
*Excluded-failed to be injected due to severe trismus. tExcluded-failed to cooperate with the flow-volume loop study.
patients were excluded (Table 2 ) leaving only 22 patients for analysis. The age and sex distributions of the subjects are shown in Figure I . The underlying causes of the vocal cord paralyses are listed in Table 2. There were 20 left and 4 right cord palsies in the study group. Symptom scores improved for both aspiration (Figure 2) and dysphonia (Figure 3 ) as a result of the injection. No patient complained of dyspnoea after the procedure. Lung function parameters, before and after Teflon injection, are shown in Tables 3-5. There were no complications associated with the procedure. All patients were able to leave hospital 2 or 3 days
+ m
e
7
+
E 6 B 5 b
4
5 2
3 2
n
31-40
41-50
51-60
61-70
71-80
81-90
Age group
Figure 1. Sex and age distribution. Male : female 16 : 6; age range 39-84, median 65.
vc
(Analysed using paired f-test).
vc
I n "
Airway resistance
FEV, FVC FEF25% FEFSOYo FEF75Yo PEF FIF50Yo PIF
10 9 ._5
Volume
TLC RV FRC ERC IC Raw
Forced expiratory flow in 1 second. Forced vital capacity. Forced expiratory flow at 25% expiration. Forced expiratory flow at 50% expiration. Forced expiratory flow at 75% expiration. Peak expiratory flow. Forced inspiratory flow at 50% inspiration. Peak inspiratory flow. Vital capacity. Total lung capacity. Residual volume. Functional residual capacity. Expiratory reserve capacity. Inspiratory capacity. Airway resistance.
Teflon injection for vocal cord paralysis and its effect on lung 499
Table 4. Preoperative and post-operative FEVl, FVC, FEVl/FVC values
Table 5. Preoperative and post-operative RV, TLC, RViTLC values
Post-operative TLC (1)
Preoperative Case
__
1.33 1.51 1.11 3.25 1.20 1.41 0.99 0.58 1.18 1.42 0.92 1.11 1.00 0.87 1.75 1.73 1.62 1.04 1.66 2.07 1.88 1.97
1 2 3 4 5 6 7 8 9 10 I1 12 13 14 15 16 17 18 19 20 21 22
1.70 1.91 1.63 3.60 1.60 1.90 2.25 0.80 1.57 1.83 1.90 1.41 2.24 1.09 2.20 2.21 2.10 1.29 2.30 3.00 2.74 2.19
1.06 1.42 1.05 2.95 0.98 1.63 0.71 0.48 1.24 1.49 0.88 1.15 0.89 0.95 1.55 1.68 1.59 1.14 1.68 1.88 1.72 1.97
78 79 68 90 75 74 43 72 75 78 48 78 44 79 78 78 77 80 72 69 68 90
1.54 1.79 1.67 3.71 1.34 1.89 2.17 0.68 1.71 1.90 1.87 1.43 2.05 1.31 2.30 2.00 2.16 1.32 2.35 2.98 2.67 2.30
1
67 78 63 79 73 85 33 71 72 78 47 81 43 73 67 83 73 86 71 63 64 70
2 3 4 5 6 7 8 9 10
II 12 13 14 15 16 17 18 19 20 21 22
(Table 2 ) . It is not surprising that most of the patients were smokers, and a majority had chronic obstructive airways disease and compromised lung function preoperatively (Table 3 and 4). If the larynx regains competence after Teflon injection, aspiration will be prevented and dysphonia improved. However, in some cases dysphonia may persist because of mucosal damage from the injection. There was greater symptomatic improvement for aspiration than for dysphonia in this group of patients (Figures 2 and 3). A statistically significant decrease in all flow parameters except F E F 75% (Forced Expiratory Flow at 75% expiration) was observed in the post-injection results. These results reflect a definite increase in airway resistance after Teflon injection of the paralysed cord. This might be expected as Teflon injection narrows the glottis. In contrast
P
0
I
2 Dysphonio scores
Figure 3. Dysphonia scores A, before and
0, after injection.
3
0.65 1.63 1.44 0.85 1.32 1.06 1.09 0.69 1.67 1.37 2.40 1.79 2.90 2.00 3.22 1.97 2.34 1.68 2.58 4.28 3.51 2.94
2.40 3.67 3.07 4.69 2.92 2.97 3.39 1.50 3.35 3.20 4.30 3.25 5.30 3.16 5.55 4.23 4.49 3.00 4.89 7.44 6.29 5.18
27 44 47 18
45 36 32 46 50 43 56 55 55 63 58 47 52 56 53 58 56 57
0.66 1.52 0.64 1.62 0.99 I .47 1.28 0.99 2.25 2.95 2.60 1.99 2.33 2.14 2.60 2.06 1.84 2.29 2.67 2.67 3.18 1.85
2.20 3.40 2.39 2.33 2.33 3.36 3.45 1.71 3.98 4.85 4.49 3.50 4.45 3.45 4.94 4.06 4.09 3.61 5.04 5.88 5.85 4.17
RViTLC
(%I 30 45 27 42 42 44 37 58 57 61 58 57 52 62 53 51 45 63 53 45 54 44
to our findings, Kashima observed improvement in inspiratory as well as expiratory flow rates following Teflon injection.6 It is interesting to note that the parameters which are indicators of large airway resistance show a highly significant change. Volume parameters on the other hand, which do not necessarily vary with airway resistance, remained unchanged. The increase in overall airway resistance as reflected by the Raw value (Table 3), is the most accurate clinical method of measuring airway resistance, and provided an excellent counter check for the reliability of the results. M o s t patients in this study had incurable disease with a limited life expectancy. Therefore we did not subject them to subsequent spirometric studies to evaluate the long-term effects of Teflon injection, as the intention was to disturb the patients as little as possible.
Conclusion Vocal cord palsy treated by Teflon injection under general anaesthesia is a safe, effective and worthwhile procedure even for elderly patients with terminal malignancy. By improving laryngeal function, this simple procedure enhances the quality of life of these unfortunate patients. Although a significant increase in airway resistance was shown after Teflon injection, the change was not sufficient to cause symptomatic airway obstruction.
500
J.K.S. Woo et a1
Acknowledgements The authors would like thank the staff of the Pulmonary Function Laboratory of the Princc of Wales Hospital for their help with the pulmonary function testing and Miss Elsie Chu for preparing the manuscript.
References I GRIFFINS.M.. CHIJNC S.C.S., VAS HASSELTC.A. & LI A.K.C. (1992) Late swallowing and aspiration problems after oesophagectomy for cancer: malignant infiltration of the recurrent laryngeal nerves and its management. Surgery (in press)
2 BATESG.J., CURLEYJ.W. & WAKIIM.E. (1984) Respiratory obstruction following vocal cord injection of Teflon paste. Anaesthesia 39, 1232-1234 3 EJNELLH . , MANSSONI., BAKEB. & STENEIORG R. (1984) Laryngeal obstruction after Teflon injection. Acfa Ofolaryngol. 98, 374-379 4 BODENHAM A,, LATIMER R . & BETHUNE D. (1987) Respiratory obstruction following vocal cord injection. A complication on induction of anaesthesia. Anaesthesia 42, 289-292 5 AUN C.S.T., I IOUCHTON I.T., So H.Y ., VAN HASSELT C.A. & OH T.E. (I 990) Tubeless anaesthesia for microlaryngeal surgery. Anaesthesia Intensive Care 18, 497-503 6 KASHIMAH . K . (1984) Documcntation of upper airway obstruction in unilateral vocal cord paralysis: flow-volume loop studies in 43 subjects. Laryngoscope 94, 923-937
