External Nasal Valve Efficacy Index: a simple test to evaluate the external nasal valve

Abstract

Many methods and techniques have been proposed for the assessment of the nasal valve, most requiring special equipment. Furthermore the main focus has been on the internal valve, while the role of the external nasal valve (ENV) has usually been underestimated. An index to assess ENV is presented herein. Two photographs of the basal view of the nose are taken, one in the resting position and the other after deep inspiration. These two life-size views are used to calculate the External Nasal Valve Efficacy Index (ENVE Index). Using simple software, the surface area of the nostril in the resting view ( A ) and breathing view ( B ) is measured. The ENVE Index is calculated by dividing the deep inspiration surface area by the resting surface area ( B / A ). The clinical indications for the use of the ENVE Index include rhinoplasty treatment planning, postoperative evaluation to assess the effects of surgery with regard to improvement or deterioration of the airway, and orthognathic surgery and the planning of appropriate postoperative care (such as elastic or intermaxillary fixation) according to the airway patency. The ENVE Index is a relatively simple, reproducible, and documentable test. This index can help the surgeon to make better decisions during treatment planning and postoperative care.

The external nasal valve is a determinant part of the nasal airway. It is estimated that this part of the nose is responsible for 75% of nasal airway resistance.

A detailed examination of the nasal valves is a crucial part of the airway assessment prior to any procedure that is planned in the region of the nose. Many methods and techniques have been proposed for the assessment of the nasal valve, including rhinomanometry, acoustic rhinometry, and computed tomography (CT). Most of these methods require special equipment and skills, and nearly all of them are focused on the internal nasal valve. The role of the external valve is usually underestimated.

A simple index to assess the external nasal valve is presented herein. This index is based on simple photography, which is obtained routinely as part of the preoperative documentation. This test is easily repeated and documented at each stage of treatment and the authors recommend it for all rhinoplasty and orthognathic cases.

Materials and methods

External Nasal Valve Efficacy Index (ENVE Index)

This study was approved by the research and ethics committee of the study university. The guidelines of the Declaration of Helsinki were followed in this study.

The index is based on standard basal view photographs of the patient. The patient’s head is tilted backwards until the two pupils of the eyes and the nasal tip are seen in a single line. This provides an exact reproducible basal view of the nose. The first photograph is taken in the resting position ( Fig. 1 A). The patient is then asked to take in a deep breath and the second photograph is taken in the same position ( Fig. 1 B). These two life-size digital views are used to calculate the ENVE Index. Using simple software, the surface area of the nostril in the resting view ( A ) and breathing view ( B ) is measured. The ENVE Index is calculated by dividing the deep inspiration surface area by the resting surface area ( B / A ).

Fig. 1
(A) Preoperative basal view of the nose in the rest position in a 25-year-old male candidate for primary open rhinoplasty. (B) Preoperative basal view of the nose in the deep inspiration position in the same patient; a weak ENVE Index was documented for the left external nasal valve. (C) Postoperative basal view of the nose in the rest position. (D) Postoperative basal view of the nose in the deep inspiration position after reinforcement of the weak external nasal valve; a considerable improvement in the external nasal airway was obtained, while aesthetic demands were simultaneously met.

Clinical indications for the ENVE Index

The ENVE Index may be done as part of routine maxillofacial examinations, although it may be particularly beneficial for the indications listed below.

Rhinoplasty treatment planning

This test will provide a documented overview of the external nasal valve function. A weak nasal valve (ENVE Index < 1) will indicate that any reductive procedure over the external nasal valve components, such as cephalic trimming or dome splitting, must be avoided or compensated for with other reinforcing grafting techniques (such as an alar batten graft or alar contour graft).

Postoperative evaluations

This simple test is easily reproducible and for this reason the postoperative index may be compared easily with the preoperative index; in this way any improvement or deterioration can be detected and documented.

Orthognathic surgery

Orthognathic surgery is usually accompanied by a considerable amount of swelling and oedema in the oral and nasal airways. Training elastics or even intermaxillary fixation (IMF) are sometimes used immediately after surgery. A weak ENVE Index will indicate that an incompetent nasal airway already exists and any procedure over the oral airway should be performed with caution.

Results

Clinical examples

Case 1: Use of the ENVE Index for treatment planning

A 25-year-old man was a candidate for primary open rhinoplasty. During preoperative evaluation, a forced inspiration test was performed and the ENVE Index was found to be 0 on both sides, suggesting poor external nasal valves. This index indicated the need for a reinforcement treatment plan to provide an acceptable nasal airway after the rhinoplasty. A lateral crural strut graft was designed and made from septal cartilage for this purpose. At the 6-month follow-up, a considerable improvement in the nasal airway was evident, while the aesthetic demands had been met simultaneously ( Fig. 1 A–D).

Case 2: Use of the ENVE Index for postoperative evaluations

A 19-year-old woman was scheduled for an open approach rhinoplasty. The ENVE Index showed a major incompetency in the right nostril. This indicated that resection techniques could further damage the valve and that reinforcement techniques should be considered. Minimal cephalic trimming was done and an alar contouring graft was applied to strengthen the valve. At the 6-month follow-up, the ENVE Index was found to be improved, and both external nasal valves worked better postoperatively ( Fig. 2 A–D).

Fig. 2
(A) Preoperative basal view of the nose in the rest position in a 19-year-old female candidate for primary open rhinoplasty. (B) Preoperative basal view of the nose at deep inspiration; a weak ENVE Index was documented for the right external nasal valve. (C) Postoperative basal view of the nose in the rest position. (D) Postoperative basal view of the nose in the deep inspiration position after reinforcement of the weak external nasal valve with an alar contour graft; a considerable improvement in the external nasal airway was obtained, while aesthetic demands were simultaneously met.

Case 3: Use of the ENVE Index for orthognathic surgery

A 27-year-old woman with a mild class III deformity was a candidate for simultaneous orthognathic surgery and secondary rhinoplasty. The preoperative ENVE Index showed considerable bilateral valve collapse. This indicated that after the orthognathic surgery, elastics or IMF would need to be used carefully because a deep inspiration would completely block the nasal airway and compromise total breathing postoperatively. For this reason, external nasal valve reinforcement modalities were considered. After performing the bilateral sagittal osteotomy and fixation with three screws, nasotracheal intubation was switched to oral intubation and a reconstructive secondary rhinoplasty was started with an open approach. Conchal cartilage was harvested and two alar batten grafts were prepared and fixed over the lateral crural cartilages. Postoperative follow-up showed that the ENVE Index had improved considerably ( Fig. 3 A–D).

Fig. 3
(A) Preoperative basal view of the nose in the rest position in a 27-year-old female with a mild class III deformity who was a candidate for simultaneous orthognathic surgery and secondary rhinoplasty. (B) Preoperative basal view of the nose at deep inspiration; a weak ENVE Index was documented for the right and left external nasal valves. (C) Postoperative basal view of the nose in the rest position. (D) Postoperative basal view of the nose in the deep inspiration position after reinforcement of the weak external nasal valves with bilateral alar batten grafts; a considerable improvement in the external nasal airways was obtained.

A summary of the pre- and postoperative ENVE Index scores of the three patient cases described above is given in Table 1 .

Table 1
Summary of the pre- and postoperative ENVE Index scores of the three patient cases described in the text.
Patient 1 Patient 2 Patient 3
Left nostril Preoperative
Index (%) 39.4 65.7 52.4
Surface area, mm 2
Inspiration 31.5 34.2 27.6
Rest 79.8 52.0 52.6
Postoperative
Index (%) 98.8 83.9 92.0
Surface area, mm 2
Inspiration 111.9 56.3 51.0
Rest 113.2 67.1 55.4
Changes
Index (%) +59.4 +18.2 +39.6
Surface area, mm 2
Inspiration +80.4 +22.1 +23.4
Rest +33.4 +15.1 +2.8
Right nostril Preoperative
Index (%) 99.8 0 0
Surface area, mm 2
Inspiration 93.5 0 0
Rest 93.6 46.5 38.0
Postoperative
Index (%) 98.7 69.1 66.7
Surface area, mm 2
Inspiration 112.2 52.3 35.8
Rest 113.6 75.6 53.6
Changes
Index (%) −1.1 +69.1 +66.7
Surface area, mm 2
Inspiration +18.7 +52.3 +35.8
Rest +20 +29.1 +15.6
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Jan 17, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on External Nasal Valve Efficacy Index: a simple test to evaluate the external nasal valve
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