Orthognathic surgery has varying effects on respiratory parameters. The authors undertook a prospective study of patients requiring mandibular advancement, mandibular setback and maxillary Le Fort I advancement, and surgically assisted rapid maxillary expansion (SARME). Breathing parameters were monitored in a sleep laboratory the night before the operation and in a mean of 9.5 months after the operation. In patients treated with mandibular advancement, the respiratory disturbance index (RDI), oxygen desaturation index (ODI), and number of obstructive apnoeas (OAs) improved significantly. In patients treated with mandibular setback and maxillary Le Fort I advancement, the RDI, ODI, index of flow limitations (IFL), number of obstructive hypopnoeas (OHs), OA, and oxygen saturation deteriorated. In contrast, patients treated with SARME improved only mildly. These results indicate that bimaxillary surgery for Class III malocclusion increased upper airway resistance, probably because of a more dorsal positioning of the base of the tongue, representing an iatrogenic obstructive sleep apnoea (OSA). A young person would probably be able to balance such a decline in respiratory function using different adaptative mechanisms. Mandibular advancement significantly improved respiratory parameters during sleep. The possible effect of orthognathic surgery on the upper airways should be incorporated into the treatment plan.
Orthognathic surgery aims to correct congenital or acquired jaw deformities . Aside from changing the bite and facial aesthetic parameters, orthognathic surgery has a marked impact on upper airway dimensions. Numerous reports have described anatomic changes in the upper airways resulting from orthognathic surgery, demonstrated in vivo using lateral cephalograms, computed tomography, and magnetic resonance imaging . Generally, maxillary or mandibular advancement leads to dilatation of the upper airways, and is similar to surgically assisted rapid maxillary expansion (SARME), while mandibular setback leads to narrowing of the upper airways . Such a situation can occasionally occur in combination with Le Fort I osteotomy advancement .
These beneficial changes brought about by orthognathic surgery are well described in patients with congenital or acquired sleep disorders , but the effect of such surgery on patients without nocturnal breathing disorders is a controversial topic. Some authors describe these changes as temporary, others say they are permanent, and may worsen in the future . Scientific evidence on the functional effect of these anatomic changes on the upper airways is scarce. Owing to the voluntary upper airway patency during the waking state, the only possibility of examining upper airway function is during sleep. The method of choice is more-or-less limited to all-night polysomnography (polygraphy), together with pulse transient time. The hypothesis presumes that bilateral sagittal split osteotomy (BSSO) advancement enlarges the upper airways by an anterior shift of the mandibular bone and extrinsic tongue muscles, thus improving breathing parameters. On the other hand, the BSSO setback narrows the upper airways and worsens ventilation parameters during sleep. The authors hypothesize that SARME has minimal effects on breathing parameters during sleep, because the nose has little effect on upper airway patency during sleep.
Materials and methods
Three groups of patients were studied, those having: Class II skeletal deformity requiring BSSO (mandibular) advancement; Class III skeletal deformity requiring BSSO setback and Le Fort I (maxillary) advancement; and maxillary transverse compression requiring SARME, where the sagittal position of the mandible remained the same. In each group, six patients (three males and three females) were randomly selected and included in the study. Every patient underwent a clinical ENT examination, including indirect laryngoscopy and rigid endoscopic nasopharyngoscopy. The inclusion criteria were: non-syndromic patients requesting surgery in order to improve occlusion and facial balance; and the absence of any breathing disorder. Exclusion criteria include: the presence of any other disease beside jaw abnormity; history of any breathing disorder; patients using hypnotics, drugs, or alcohol on a daily basis, as evidenced by medical history; incomplete documentation; the presence of any pathology observed during ENT examination (e.g. hypertrophic adenoid vegetation, deviation of the nasal septum, and chronic inflammatory or allergic damage of the nasal and nasopharyngeal mucosa); inability to attend follow-up for the whole study period; and any additional surgical procedures, including genioplasty, turbinectomy or aesthetic rhinoplasty.
Breathing parameters were monitored in the sleep laboratory the night before surgery and 9.5 months (range 8.4–12.7 months) afterwards using the Hypno PTT (Tyco Health-care Ltd., UK). The following parameters were measured: nasal air flow by the index of flow limitations (IFL); respiratory disturbance index (RDI); oxygen desaturation index (ODI); obstructive apnoeas (OAs); obstructive hypopnoeas (OHs); central apnoeas (CAs); central hypopnoeas (CHs); average oxygen saturation; snoring; microarousal; an ECG; and position of the body. According to the Chicago criteria, apnoea was recognized as stop in airflow for >10 s, and hypopnea as: those with a >50% decrease in a valid measure of airflow without a requirement for associated oxygen desaturation or arousal; and those with a lesser airflow reduction in association with oxygen desaturation of >3% of arousal .
Data are reported as mean ± SEM. All parameters were analysed using the Wilcoxon signed rank test for pairs comparison ( p < .05). For comparison of data among all three groups 1-way ANOVA with a post hoc LSD test ( p < .05) was used.
Mean age of patients was 22.4 ± 0.8 years (range 16–28 years), but was not significantly different among particular groups or between males and females. In the skeletal Class II patients, the mandible was advanced a mean distance of 7.1 ± 0.4 mm (range 5.5–8.2 mm). In the skeletal Class III patients, the mandible was set back a mean distance of 4.1 ± 0.2 mm (range 3.7–5.2 mm), and the maxilla advanced a mean distance of 5.9 ± 0.4 mm (range 4.8–7.2 mm). In the patients requiring SARME, the mean distance between the upper first molars was increased 7.5 ± 0.3 mm (range 6.5–8.2 mm). There were no significant differences in body mass index (BMI) and time of measurement among groups ( Table 1 ).
|Class II||Class III||SARME|
|BMI||22.88 ± 1.16||22.34 ± 1.54||21.84 ± 1.19|
|Operation time||435.50 ± 16.24||426.50 ± 30.04||463.67 ± 28.71|
|RDI||6.75 ± 1.98||1.95 ± 0.57*||3.85 ± 0.58||5.02 ± 0.65*||4.02 ± 0.76||2.65 ± 0.45*|
|ODI||3.18 ± 0.50||1.18 ± 0.70*||0.50 ± 0.16||3.13 ± 0.42*||0.45 ± 0.16||0.27 ± 0.15|
|OA||3.75 ± 1.68||1.03 ± 0.42*||1.22 ± 0.20||3.48 ± 1.20*||1.43 ± 0.38||0.68 ± 0.33*|
|IFL||0.45 ± 0.27||0.27 ± 1.18||1.80 ± 1.00||5.97 ± 1.79*||2.55 ± 1.51||1.05 ± 0.65|
|OH||2.22 ± 1.18||0.92 ± 0.46||2.32 ± 0.60||5.03 ± 1.22*||1.78 ± 0.70||0.65 ± 0.42|
|Saturation||96.50 ± 0.72||98.13 ± 0.31||96.83 ± 0.54||94.17 ± 0.79*||98.17 ± 0.31||98.33 ± 0.21|
|CA||0.48 ± 0.28||0.35 ± 0.26||0.18 ± 0.07||0.45 ± 0.18||0.32 ± 0.11||0.62 ± 0.30|
|CH||0.23 ± 0.11||0.03 ± 0.03||0.28 ± 0.08||0.20 ± 0.09||0.47 ± 0.14||0.32 ± 0.18|
In patients with skeletal Class II abnormality treated with mandibular advancement, three of eight respiratory parameters improved. Mean RDI decreased significantly from 6.8 ± 2.0 to 2.0 ± 0.6 (i.e. to 29% of its original value). Mean ODI decreased significantly from 3.2 ± 0.5 to 1.2 ± 0.7 (to 38% of its original value). Mean number of OAs decreased significantly from 3.8 ± 1.7 to 1.0 ± 0.4 (to 26% of its original value). In other respiratory parameters, the authors did not observe any significant differences between the pre- and postoperative Class II groups ( Table 1 ). In general, mandibular advancement has a positive impact on respiratory parameters during sleep.
In patients with skeletal Class III abnormality treated with mandibular setback and maxillary Le Fort I advancement, six of eight respiratory parameters decreased significantly after the operation ( Table 1 ). Mean RDI increased from 3.9 ± 0.6 to 5.0 ± 0.6 (to 130% of its original value). Mean ODI increased from 0.5 ± 0.2 to 3.1 ± 0.4 (to 620% of its original value). Mean IFL increased from 2.3 ± 0.6 to 5.0 ± 1.2 (to 217% of its original value). Mean number of OHs increased from 1.8 ± 1.0 to 6.0 ± 1.8 (to 333% of its original value). Mean number of OAs increased from 1.2 ± 0.2 to 3.5 ± 1.2 (to 291.7% of its original value). The significant decrease of mean oxygen saturation from 96.8 ± 0.5 to 94.2 ± 0.8 (to 97.3% of its original value) is not surprising. The authors did not observe any significant changes in CAs or CHs ( Table 1 ). In general, mandibular setback with maxillary Le Fort I advancement significantly impairs respiratory parameters during sleep.
In patients treated with SARME, two of eight respiratory parameters improved ( Table 1 ). Mean RDI decreased from 4.0 ± 0.8 to 2.7 ± 0.5 (to 67.5% of its original value). Mean number of OAs decreased from 1.4 ± 0.4 to 0.7 ± 0.3 (to 50.0% of its original value). Other parameters were generally improved, but the difference between preoperative and postoperative values did not reach statistical significance. It can be concluded that SARME has a mild positive effect on respiratory parameters during sleep.