Effects of reduced mouth opening capacity (trismus) on pulmonary function

Copyright © Munksgaard2000

Int. J. Oral Maxillofae. Surg. 2000;29:351-354 Printed in Denmark. All rights reserved

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Oral& MaxillofacialSurgery ISSN 0901-5027

Effects of reduced mouth

opening capacity (trismus)

G. Krennmair 1, C. W, Ulm 2, F. Lenglinger 3 1Oral and Maxillofacial Surgery, Privat Hospital Wels; 2Departmentof Oral Surgery University of Vienna; aDepartmentof Medicine, General Medical Hospital Wels, Austria

on pulmonary function G. Krennmair, C. W. Ulm, F LengIinger. Effects of reduced mouth opening capacity (trismus) on pulmonary function. Int. J. Oral Maxillofac. Surg. 2000; 29: 351-354. © Munksgaard, 2000 Abstract. In this study, pulmonary function test data were obtained from 15

healthy volunteers and 15 patients with slightly impaired ventilation during both normal and maximally reduced opening of the mouth (trismus, intercuspal position). The aim of the study was to examine the effects of complete trismus on pulmonary function using objective and subjective parameters. In maximally reduced mouth opening, both groups showed an impairment of all subjective and objective pulmonary function test data. In healthy volunteers, the significant changes in test data (P<0.05) stimulated mild to moderate pulmonary impairment, whereas patients with an already impaired pulmonary function showed a marked deterioration of their initial respiratory condition. The results of the subjective and objective parameters examined indicate that an intercuspal position (trismus) further aggravates pulmonary functional impairment. Complete trismus can be considered a risk factor to pulmonary function in patients using mouth breathing as a primary or supportive mode of respiration.

As the principles of rigid internal fixation and compression osteosynthesis have been adopted by maxillofacial surgeons during recent years, the timehonoured methods of intermaxillary fixation and intraosseous wiring have been gradually abandoned 7,9,1°. Nevertheless, a rigid connection of maxilla and mandible (intermaxillary fixation) is still a traditional treatment modality for complex fractures of the middle part of the face and the mandible, and is also often used in maxillofacial surgery4A0,13 15,19. Temporary intermaxillary fixation is also frequently carried out in special cases of orthodontic treatment and orthodontic surgery 17. Apart from these mainly surgically induced methods of connecting the maxilla with the mandible, a reduced mouth opening capacity may also be caused by local inflammatory processes. Advanced inflammation either caused by

primary infection or due to postoperative infection following oral surgery often causes myofunctionally induced trismus. Analogous to intermaxillary fixation, complete trismus constitutes the most extreme form of a reduced mouth opening capacitf ,5,12. As is known, most people breathe through the nose. Nevertheless, it is possible that normal nasal breathing is impeded or completely restricted due to anatomical or pathological causes, such as adenoid vegetations or deviations of the septum. Due to these pathological conditions, mouth breathing is used instead of or in addition to normal nasal breathing 6,8,11,2°. Apart from restricted nasal breathing, mouth breathing is also used as auxiliary respiration for compensation of dyspnoea in cases of severe pulmonary disorders 3,6,16. A rigid connection of the maxilla and the mandible - regardless of aetiology -

Key words: trismus; mouth breathing; pulmonary function. Accepted for publication 1 March 2000

results in an impairment of oral inspiration and expiration 12-a5,17,23. A maximally restricted mouth opening capacity, such as complete trismus, may thus prevent additionally required supportive mouth breathing. There is still a lack of information regarding the impact of trismus on pulmonary function. The aim of this study was to assess the pulmonary function of healthy volunteers and patients with a mild obstructive ventilation disorder at both normal and maximally restricted mouth opening (complete trismus, intermaxillary fixation) and to examine the effect of complete trismus on pulmonary function by means of objective and subjective parameters. Material and methods

A total of 30 test subjects (subdivided into two groups: 15 healthy volunteers and 15 pa-

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e t al.

T a b l e 1. Pulmonary function data of healthy volunteers (HV) and patients with pulmonary impairment (PI) at normal (NM) and maximally reduced mouth opening capacity (ICP)

t-value

P

VC

HV: PI:

4.82_+0.76 2.43-+0.68

NM

4.48-+0.70 3.48-+0.68

2.77 1.54

<0.02 n.s.

FEV1

HV: PI:

3.99-+0.92 2.43-+0.68

3.78+0.71 2.16_+0.61

2.59 2.45

<0.05 <0.05

FEV%

HV: PI:

93.6_+6.8 65.5-+4.4

68.6-+8.1 61.6-+3.1

5.24 1.55

<0.01 n.s.

MEF 50%

HV PI:

5.14-+2.12 1.77-+0.73

4.18-+1.28 1.83_+0.81

3.08 0.51

<0.05 n.s.

MIF 50%

HV PI:

1.66-+0.57 1.55-+0.49

0.87_+0.41 0.96_+0.42

8.43 5.31

<0.01 <0.01

PEF

HV: PI:

9.53_+ 1.68 6.57_+ 1.85

7.66-+ 1.89 4.87-+ 1.68

4.14 2.40

<0.01 <0.05

Rin

HV: PI:

0.218-+0.054 0.397-+0.148

0.508-+0.219 0.828_+0.505

13.86 2.59

<0.01 <0.05

Rto t

HV" PI:

0.223-+0.053 0.401-+0.131

0.538_+0.201 0.814-+0.386

5.37 3.20

<0.01 <0.01

tients with obstructive ventilation disorder) were included in this study. There were no differences in age (36.1+4.7 years vs 37.8-+5.4 years), sex (5 women/10 men vs 6 women/9 men), height (174.2-+10.4 cm vs 177.8-+13.21 cm), weight (76.3-+14.7 kg vs 73.8-+12.3 kg) or possible risk factors (e.g. smokers 5 vs 6) between healthy volunteers and patients with ventilation disorders. The group of test subjects with pulmonary impairment only included patients with a mild obstructive ventilation disorder. This was defined as a forced expiratory volume during the first second (FEV%) greater than 60% and less than 70%, and a total airway resistance (Rtot) greater than 0.3 kPa s/1. Patients with more severe respiratory disorders and patients with restrictive ventilation disorders were excluded from this study (they could not be expected to undergo a pulmonary function test in the trismus position). Both objective and subjective examination methods were used for evaluation of the respiratory condition. In the objective pulmonary function test, the following functional data of maximum inspiration and subsequent maximum expiration were recorded: VC: vital capacity; 1, FEVa: forced expiratory volume during the first second; 1, FEV%: FEV1/VC× 100, MEF 50%: mid-expiratory flow; l/s, at 50% of VC ex, MIF 50%: mid-inspiratory flow, l/s, at 50% of VC in, Rtot: total airway resistance; kPa s/l, Rin: inspiratory airway resistance; kPa s/l, PEF: peak expiratory flow; l/s. Both the healthy volunteers and the patients with pulmonary impairment underwent pulmonary function tests in two mouth opening positions: at unrestricted (normal) mouth opening [maximum mouth opening =

ICP

distance between the incisal edges of the maxillary and mandibular anterior teeth (incisal edge distance, IED); mean (x_+SD): 49-+6.8 ram; range 44-58 mm] and at an intercuspal position simulating intermaxillary fixation (IED 0 mm, maximally reduced mouth opening). The healthy volunteers underwent three measurements in each of the two mouth opening positions, while patients with pulmonary impairment underwent 3 to 5 measurements (3.5+0.7) at unrestricted mouth opening and 3 to 5 measurements (3.2-+0.4) at maximally reduced mouth opening. The truth table with the most favourable functional values was evaluated. The respiratory condition in the different mouth opening positions was also evaluated subjectively by the test subjects, using a clinical scoring system (dyspnoea scale: l = n o dyspnoea, 2=mild, 3=moderate, 4=severe, 5=very severe dyspnoea). All objectively and subjectively evaluated data were tabulated and mean values and standard deviations were calculated. The data obtained in an um-estricted and a maximally reduced mouth opening position, respectively, were compared across the two groups of test subjects. Differences in mean values were assessed by means of the paired Student's t-test. P-values <0.05 were considered statistically significant.

clear deterioration of the examined respiratory parameters. Significant decreases (P<0.01, P<0.05, P<0.01, respectively) in the values obtained for FEV%, M E F 50% and M I F 50% were observed between n o r m a l m o u t h opening (NM) and reduced m o u t h opening (ICP). Furthermore, a significant (P<0.01) increase in respiratory airway resistance (Rto t and Rin ) was observed in the intercuspal position (Table 1). In contrast, the F E V % and M E F 50% values of patients with an initial pulm o n a r y disorder did not differ significantly between n o r m a l and maximally reduced m o u t h opening (Table 1). Only M I F 50% differed significantly between normal and maximally reduced m o u t h opening (P<0.01). In patients with pulm o n a r y impairment, complete trismus resulted in a significant increase in total (Rtot; P<0.05) and inspiratory (Rin; P<0.01) airway resistance (Table 1). Fig. 1 shows the subjectively given dyspnoea scores of the two groups of test subjects at both n o r m a l and reduced m o u t h opening capacity. In both groups, maximally reduced m o u t h opening resulted in a significant deterioration of the subjectively evaluated respiratory condition (healthy volunteers: score 1.0 v s 1.6-+0.5, t=4.58, P<0.01; patients with p u l m o n a r y impairment: score 2.3+0.48 v s 3.0-+0.6, t=5.19, P<0.01). The subjectively and objectively assessed values showed that an intercuspal position imitates a m o d erate p u l m o n a r y functional disorder in healthy test subjects and causes an aggravation of the existing p u l m o n a r y

5-

s 4,

Results Table 1 shows the objectively measured respiratory parameters of healthy volunteers and patients with (obstructive) p u l m o n a r y disorder, at n o r m a l and completely reduced m o u t h opening [complete trismus, intercuspal position (ICP), I E D = 0 mm]. In the position of complete trismus (ICP), healthy volunteers showed a

Healthy vol. NM ICP

NM

Patients ICP

Subjectively given dyspnoea values of healthy volunteers and patients with (obstructive) pulmonary impairment at normal (NM) and maximally reduced mouth opening capacity (ICP). Fig. 1.

Effects of mouth opening capacity on pulmonary function functional disorder in patients with pulmonary impairment. Discussion

Deviations of the nasal septum and adenoid vegetations are pathological or anatomical conditions which lead to a severe impairment of normal nasal breathing and may even make nasal breathing impossible in some cases. As a result of the nasopharyngeal impairment, mouth breathing is used instead of or in addition to nasal breathing 2'8'16'18'21. Apart from rhinological causes of mouth breathing, there are also persons who are habitual mouth breathers 2'18, mostly children and adolescents who breathe through their mouth even if the nasal passage is normal. As is known, habitual mouth breathing often results in severe abnormal positioning of the jaws, so that orthodontists and speech therapists play an increasingly important role in the diagnosis and treatment of this habit. An open mouth position and the specific dolichofacial skeletal pattern are typical features of the craniofacial morphology of patients who are habitual mouth breathers 2. Patients with primary pulmonary disorders, such as obstructive ventilation disorders, also use mouth breathing as auxiliary breathing for compensation of the often subjectively felt ventilation deficit. In patients with obstructive ventilation disorders, mouth breathing is used partly as a special kind of treatment and partly for its supportive psychological value 6,8,11,16,20. In all cases of primary or additional secondary mouth breathing, a reduction of the mouth opening capacity constitutes an impairment of the normal breathing capability. A reduction of the mouth opening capacity may either be caused intentionally or unintentionally I'4'5'12-14'2°'23. An example of intentionally induced trismus is intermaxillary fixation. Although it is a wellknown fact that rigid internal fixation and compression osteosynthesis has largely replaced intermaxillary fixation 7, this rigid connection of maxilla and mandible is still a traditional part of several treatment modalities in maxillofacial traumatology4,7,13,19. Intermaxillary fixation is now the exception rather than the rule 7, but is often considered the treatment of choice for complex fractures of the middle part of the face 13 as well as for several forms of condylar fractures of the mandible 14,22

and for mandibular fractures in children 1°. Unintentionally induced trismus may occur after oral surgical procedures, such as removal of unerupted wisdom teeth, or as a result of advanced inflammation. In the latter case, oedema caused by inflammation and muscle spasms results in the formation of trismus 1'5. The findings of this study indicate that this terminal oral resistance causes a change in objectively and subjectively measured respiratory parameters in both healthy volunteers and patients with an initial pulmonary impairment. In the study carried out by WILLIAMS • CAWOOD23, complete trismus in healthy volunteers simulated the kind of pulmonary function data as may be found in a case of mild to moderate pulmonary functional impairment. Although a condition of trismus produces pathological pulmonary functional values, clinical experience has shown that trismus has no significant effect on the pulmonary function of healthy nose breathers3,11,20. Unimpaired nasal breathing guarantees a sufficient ventilation. Only in cases of impaired nasal breathing and resultant mouth breathing does trismus gain clinical relevance. WILLIAMS & CAWOOD23 concluded from their data that trismus would further aggravate the respiratory condition of persons with pulmonary impairment. Their hypothesis was confirmed by our detailed examinations. Although patients with obstructive ventilation disorders did not show a significant deterioration of all evaluated objective parameters, an increase in dyspnoea was observed when subjective data were taken into account. The inability to breathe in and out additionally through the mouth mainly has an effect on the psychological and subjectively evaluated component of dyspnoea. In view of the examined group of patients, it may also be assumed that patients with more severe pulmonary disorders would also show a deterioration of objective parameters. The findings of our study indicate that trismus constitutes a considerable risk factor for the deterioration of pulmonary function in both mouth breathers and patients with obstructive pulmonary defects. Before applying treatment methods inducing trismus, such as intermaxillary fixation4,17,I9, patients should therefore be examined for the type of respiration used and existing primary pulmonary disorders.

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It is particularly important to examine them for a possible coexistence of existing and developing risk factors. In the case of suspected risk factors, pulmonary function tests should also be carried out by means of bronchial inhalational provocation 3,s,s'll. In combination with complete trismus, a predisposition to allergy which manifests itself as pulmonary impairment upon exposure, may result in a massive further increase in dyspnoea in healthy mouth breathers. If such risk factors exist, it is necessary to discuss possible alternative treatment modalities. References

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Address: Univ.Doz. Dr. G. Krennmair Trauneggsiedlung 8 A-4600 Wels Austria