Numerical simulation of intranasal airflow after radical sinus surgery

PURPOSE: Radical sinus surgery disturbs intranasal humidification and heating of inspired air, resulting in reduced air conditioning mainly caused by a disturbed airflow. Therefore, the aim of this study was to simulate the intranasal airflow after radical sinus surgery during inspiration by means of numerical simulation. MATERIAL AND METHODS: A bilateral model of the human nose with maxillectomy, ethmoidectomy, and resection of the lateral nasal wall and the turbinates on one side based on a multislice computed tomographic scan was reconstructed. An unsteady numerical simulation displaying the intranasal airflow patterns applying the computational fluid dynamics solver Fluent 6.1.22 was performed. RESULTS: Spacious vortices throughout the entire nasal cavity and the paranasal sinuses caused by the radical resections occurred, causing a less-intense contact between air and the surrounding nasal wall. An enlargement of the nasal cavity volume and a reduction of the nasal surface area in ratio to the nasal cavity volume could be observed. CONCLUSIONS: Aggressive sinus surgery leads to disturbed intranasal air conditioning caused by disturbed intranasal airflow patterns and a reduction of the surface area in relation to the nasal volume. The presented numerical simulation demonstrates the close relation between air conditioning and intranasal airflow. It can be helpful to understand and interpret in vivo measured data of intranasal temperature and humidity.     

Numerical simulation of airflow patterns and air temperature distribution during inspiration in a nose model with septal perforation

BACKGROUND: The most typical symptoms of patients with nasal septal perforation (SP) are crusting and recurrent nosebleed. The objective of the study was to determine the influence of SP on intranasal temperature profile and airflow patterns during inspiration by means of numerical simulation. METHODS: Two realistic bilateral models of the human nose with and without SP were reconstructed based on computed tomography (CT). A numerical simulation was performed. The intranasal air temperature distribution and airflow patterns during inspiration were displayed, analyzed, and compared. RESULTS: SP causes a highly disturbed airflow in the area of perforation. A spacious vortex within the perforation including various localized vortices was detected. A disturbed intranasal temperature distribution between the right and left nasal cavities developed. CONCLUSIONS: The numerical simulation demonstrates the interaction between airflow patterns and heating of respiratory air. The disturbed airflow causes reduced air conditioning. This fact may contribute to crusting and recurrent nosebleed.     

A numerical simulation of intranasal air temperature during inspiration

OBJECTIVES/HYPOTHESIS: In vivo measurements of the intranasal air temperature are feasible. The present study was designed to reproduce temperature distributions within the human nasal cavity by means of numerical simulation. STUDY DESIGN: Numerical simulation. METHODS: Based on computed tomography (CT), a steady-state computational fluid dynamics (CFD) simulation was performed displaying the temperature distribution throughout the human nasal cavity during inspiration. The results of the numerical simulation were compared with in vivo temperature measurements. RESULTS: The numerical simulation demonstrated that the major increase of the inspiratory air temperature can be found in the anterior nasal segment, especially within the nasal valve area, which is comparable to in vivo measurements. Intranasal areas of high temperature were characterized by turbulent airflow with vortices of low velocity. The results of numerical simulation showed an excellent comparability to the results of previous in vivo measurements in the entire nasal cavity. CONCLUSION: The anterior nasal segment is the most effective part of the nose in heating of the ambient air. The findings demonstrated the complexity of the relationship between airflow patterns and heating of inspired air. A numerical simulation of the temperature distribution using CFD is practicable.     

Nasal air temperature and airflow during respiration in numerical simulation based on multislice computed tomography scan

BACKGROUND: Adequate nasal air-conditioning is of greatest importance. Because detailed processes of nasal air-conditioning still are not completely understood, numerical simulations of intranasal temperature distribution and airflow patterns during inspiration and expiration were performed. METHODS: A three-dimensional model of the human nose based on computed tomography scans was reconstructed. A computational fluid dynamics application was used displaying temperature and airflow during respiration based on time-dependent boundary conditions. RESULTS: Absolute air temperature and velocity values vary depending on detection site and time of detection. Areas of low velocities and turbulence show distinct changes in air temperature. The turbinate areas prove to be the main regions for heat exchange. The numerical results showed excellent comparability to our in vivo measurements. CONCLUSION: Numerical simulation of temperature and airflow based on computational fluid dynamics is feasible providing entirely novel information and an insight into air-conditioning of the human nose.     

Impact of unilateral sinus surgery with resection of the turbinates by means of midfacial degloving on nasal air conditioning

OBJECTIVE/HYPOTHESIS: One of the most important functions of the nose is the climatization of inspired air. The aim of the investigation was to determine the influence of radical sinus surgery with complete resection of the turbinates and the lateral nasal wall by means of midfacial degloving as treatment for inverted papilloma on the nasal humidification and heating of inspired air. STUDY DESIGN: Retrospective study. METHODS: Humidity and temperature were measured in the nasopharynx during normal respiration by means of a miniaturized thermocouple device and a humidity sensor for continuous detection. Eight patients after prior unilateral sinus surgery by means of midfacial degloving for a one-sided inverted papilloma were enrolled into the study. The humidity and temperature data of the surgically treated side were compared to the values of the healthy side that was not surgically treated. Active anterior rhinomanometry and acoustic rhinometry were performed. RESULTS: At the end of inspiration, absolute humidity and temperature values in the nasopharynx were statistically significantly lower on the surgically treated side compared with the side that was not surgically treated. CONCLUSIONS: Radical sinus surgery with resection of the turbinates by means of midfacial degloving seems to disturb the climatization of the inspiratory air in the nasal cavity. Reduced absolute humidity and temperature may contribute to crusting, bleeding, and nasal dryness as frequent complaints of patients after aggressive sinus surgery with resection of the turbinates.     

A dynamic and direct visualization model for the study of nasal airflow.

OBJECTIVE: To evaluate nasal airflow characteristics during physiologic breathing in normal and pathologic conditions. DESIGN: The choana of an anatomical human model was connected to a pump that simulated physiological pressure changes in the upper airway system. Normal ambient air was used as medium. The airstream was marked with aerosolized water particles, and was observed through an exact but translucent replica of the original nasal septum. RESULTS: In physiologic conditions the airflow is mixed. Turbulence is clearly visible even with low flow velocities. There is less turbulence with lower flow rates. The nasal airflow follows a triphasic pattern of acceleration, near-steady state, and deceleration. Turbulence is prominent in the first and third phases. The main flow stream passes through the middle meatus at all rates. Hypertrophic mucosal membranes and turbinates increase the proportion of air passing the middle meatus. With decongested turbinates, flow distribution is more even. After turbinectomy there is a significant amount of airflow passing along the floor of the nose. The olfactory region is aerated only toward the end of inspiration and during the entire expiration phase. CONCLUSIONS: This model allows the investigation of airflow distribution and turbulence under physiologic conditions and the examination of the influence of pathologic conditions on these parameters. Overzealous trimming of turbinates results in an unphysiologic distribution of airflow.     

A comparative analysis of intranasal volume and olfactory function using a three-dimensional reconstruction of paranasal sinus computed tomography, with a focus on the airway around the turbinates

The aim of this study was to investigate the relationship between the intranasal airway around the turbinates and olfactory function. In total, 32 nostrils of 16 patients who were awaiting septal surgery were involved in this study. For measurements of the volume of the nasal cavity, paranasal sinus computed tomography scans were performed and reconstructed into three-dimensional images. The Butanol Threshold Test and Cross-Cultural Smell Identification Test were used to evaluate olfactory function. The results were analyzed with Pearson’s test. The volume around the turbinates was significantly correlated with the olfactory threshold. However, olfactory identification had no significant correlation with each volume. The airway around the turbinates is very important for nasal airflow and its volume influences olfactory function. Understanding such relationships may help in preserving or improving olfactory function in septal, turbinate or sinus surgery. Further studies are needed regarding the relationships between not only the volume of the nasal cavity and nasal airflow, but also between nasal volume changes and olfactory function.     

Oronasal reconstruction with local mucoperiosteal and free latissimus dorsi flaps.

We describe the use of maxillary sinus mucoperiosteum as a pedicled flap to reconstruct the floor of the nose following resection of cancer involving the palate, buccal mucosa, and mandible. Complete inferior turbinectomy allows access to the roof of the maxillary sinus to harvest the mucoperiosteum as a vascularized flap pedicled under the remaining middle turbinate. A free latissimus dorsi myocutaneous flap suspended from the floor of the orbit and nasal septum is then used to obliterate the maxillary sinus, reconstruct the palate, and support the floor of the nose. A reconstruction employing this combination of flaps is presented, including postoperative endoscopic intranasal photography and magnetic resonance imaging. Despite the elevated level of the floor of the nose and the absence of the inferior turbinates, rhinomanometry performed 3 months postoperatively demonstrates adequate nasal airflow with normal responses to nasal decongestants.     

Nasal turbinate resection for relief of nasal obstruction

Surgical correction of mechanical nasal airway obstruction is commonly attempted by means of septoplasty or submucous resection. In spite of these procedures, patients continue to present postoperatively with inadequate nasal airflow due to hypertrophied turbinates. Partial resection of turbinate mucosa, submucous turbinate resection, electrocautery and outfracture of turbinates provide additional improvement but are incomplete procedures. Total inferior turbinectomies have been performed on 40 patients over the past 5 years; 29 of these patients have been followed from 2 to 60 months postoperatively by clinical examination and by formal questionnaire. Twenty-five patients described a marked improvement of their nasal breathing, 3 had mild improvement, and 1 had no improvement at all. Only 1 patient, 1 year postoperatively, described excessive dryness, 2 described mild dryness, 3 described excessive secretions and none complained of foul smell or pain postoperatively. All patients had patent airways by clinical examination by at least 2 otolaryngologists. The inferior turbinates play a role in humidification and temperature regulation of inspired air. The removal of them, however, does not seem to be fraught with the morbidity which has heretofore been attributed to this procedure.     

The impact of septorhinoplasty and anterior turbinoplasty on nasal conditioning

BACKGROUND: Septorhinoplasty and turbinoplasty is a frequently performed operation in facial plastic surgery. The aim of this study was to investigate nasal conditioning after septorhinoplasty and inferior turbinoplasty in patients with internal and external nasal deformities and hypertrophy of the inferior turbinates and to determine its relation to nasal patency. METHODS: Ten patients and 10 volunteers as controls were enrolled into this study. Measurement of nasal conditioning and active anterior rhinomanometry were performed before and 4-6 months after functional-esthetic septorhinoplasty and inferior turbinoplasty. RESULTS: Nasal airflow was significantly higher postoperatively than preoperatively. The preoperative nasal temperature (TEMP) and heat increase (HI) was lower in the patients compared with the controls. The postoperative TEMP, HI, total water content, and water gradient were significantly higher than the preoperative values. CONCLUSION: Based on this relatively small series, functional-esthetic septorhinoplasty in combination with inferior turbinoplasty may be associated with improved nasal conditioning.     

Trimming of the inferior turbinates: a prospective long-term study

The aim of this study was to determine whether the initial benefits of radical trimming and anterior trimming of the inferior turbinates on nasal airflow persisted in the long term. Radical trimming significantly reduced nasal resistance at 2 months following operation (n = 12) (P less than 0.005). There was no significant change in nasal resistance over the next 20 months. Symptom scores for nasal obstruction also showed a significant reduction (n = 16) (P less than 0.005), at 2 months, and did not change significantly over the next 20 months. Radical trimming of the inferior turbinates is a highly effective operation in patients with hypertrophy of the inferior turbinates with few initial complications. However, further analysis of the data revealed that up to 20% of patients lose the initial subjective benefit of relief of nasal obstruction within 2 years of follow-up. Late onset crusting occurs in some patients though this is not directly attributable to an increase in nasal airflow. This study also concludes that anterior trimming of the inferior turbinates cannot be recommended as a form of treatment.     

不同部位和大小的鼻中隔穿孔对鼻腔气流影响的数值模拟分析

目的运用数值模拟的方法探讨不同部位和大小的鼻中隔穿孔对鼻腔气流的影响。方法选取2名健康成年人的鼻腔CT数据,例1为45岁男性,例2为36岁女性,分别构建出不同部位(前端低位、中部低位、后端低位和前端高位)和尺寸(直径分别为10 mm和5 mm)的鼻中隔穿孔的鼻腔气流模型,数值模拟分析不同部位和大小的鼻中隔穿孔鼻腔数值模型的鼻腔容积、鼻腔壁面积、压强、鼻阻力、温度、气流速度、壁面剪切力、双侧鼻腔气流分配比、涡流等情况。分别将鼻阻力和气流温度差与鼻腔壁面积作Pearson相关性分析。结果在压强和鼻阻力方面,位于前端低位且较大尺寸的鼻中隔穿孔对局部的压强梯度影响更明显;前中部低位的鼻中隔穿孔可导致鼻腔阻力增加。在温度方面,前端低位和高位较大尺寸以及前端高位较小尺寸的鼻中隔穿孔对局部温度影响更明显;位于前端且具有较大尺寸的鼻中隔穿孔模型的鼻加热效率低于正常模型;前鼻孔至鼻中隔后缘的温度差与鼻腔壁面积之间存在正相关关系(例1和例2的R2值分别为0.69、0.41,P值均<0.01)。在气流平均速度方面,位于鼻腔前端低位和高位的不同尺寸穿孔相对于其他部位穿孔,对鼻腔局部的气流平均速度影响更明显。在气流的分配和涡流方面,前中部低位的鼻中隔穿孔可使原本气流分布不对称的双侧鼻腔内的气流分布更加趋于不均衡;位于鼻腔前端和中部的穿孔较鼻腔后端的穿孔会导致更加明显的涡流分布。结论鼻中隔穿孔所造成的影响与其发生的部位和大小有关,偏前端和较大的鼻中隔穿孔相对于偏后端和较小的穿孔对鼻腔内压强、鼻阻力、温度调节、气流分配等方面表现出更多的负面影响。     

Impact of resection of the turbinates and the lateral nasal wall on particle deposition

OBJECTIVES/HYPOTHESIS: The aim of the investigation was to determine the influence of complete resection of the turbinates and the lateral nasal wall on nasal deposition of particulate matter with an aerodynamic diameter of 10 microm or less (pm10) and its relation to nasal patency and geometry. STUDY DESIGN: Retrospective study. METHODS: Eight patients were enrolled in the study after unilateral sinus surgery for a unilateral inverted papilloma of the sinuses. Particle deposition from the inhaled and exhaled air was measured by means of a laser particle counter in the nasal valve area and the nasopharynx during nose-only breathing and nose-in, mouth-out breathing. The data on deposited fraction for the operated side were compared with the data for the untreated, healthy side. Rhinomanometry and acoustic rhinometry were performed. RESULTS: Particle deposition did not differ significantly between the operated and untreated sides of the nose at both detection sites. No correlation between the deposited fraction and rhinomanometric and rhinometric values was found. CONCLUSION: Radical resection of the turbinates does not seem to disturb particle deposition (pm10) measured in the nose to a significant degree. Factors other than impaction and sedimentation onto the mucosal surface of the turbinates seem to be sufficient for effective particle deposition after radical removal of the turbinates.     

Numerical study of the aerodynamic effects of septoplasty and partial lateral turbinectomy

OBJECTIVES: To investigate, first, the effects of septal deviation and concha bullosa on nasal airflow, and second, the aerodynamic changes induced by septoplasty and partial lateral turbinectomy, using computational fluid dynamics (CFD). METHODS: A three-dimensional model of a nasal cavity was generated using paranasal sinus computed tomography images of a cadaver with concha bullosa and septal deviation. Virtual septoplasty and partial lateral turbinectomy were performed on this model to generate a second model representing the postoperative anatomy. Aerodynamics of the nasal cavity in the presence of concha bullosa and septal deviation as well as postoperative changes due to the virtual surgery were analyzed by performing CFD simulations on both models. Inspiratory airflow with a constant flow rate of 500 mL/second was used throughout the analyses. RESULTS: In the preoperative model, the airflow mostly pass through a narrow area close to the base of the nasal cavity. Following the virtual operation, a general drop in the maximum intranasal air speed is observed with a significant increase of the airflow through right middle meatus. While in the preoperative model the greatest reduction in pressure is found to be in the localization of anterior septal deviation on the right side and confined to a very short segment, for the postoperative model, it is observed to be in the nasal valve region in both nasal cavities. Following septoplasty and partial lateral turbinectomy, total nasal resistance is reduced significantly. CONCLUSIONS: CFD simulations promise to make great contributions to understand the airflow characteristics of healthy and pathologic noses. Before surgery, planning for any specific intervention using CFD techniques on the nasal cavity model of the patient may help foreseeing the aerodynamic effects of the operation and might increase the success rate of the surgical treatment.     

Nasal airflow receptors: the relative importance of temperature and tactile stimulation.

The receptors responsible for the nasal sensation of airflow have not been identified with certainty. Although both mechanoreceptors and thermoreceptors have been implicated, evidence suggests that the nose is more sensitive to cold air than to air at body temperature. The present study was designed to investigate the relationship between the velocity and the temperature of an airjet as regards its ability to stimulate the nasal lining. Both the nasal vestibule and the nasal cavum are more sensitive to cold air than to air at mean intranasal temperature (P < 0.001). A similar effect is seen with warm air which is as stimulating as cold air. The nasal vestibule is twice as sensitive as the nasal cavum to an airjet at mean intranasal temperature (P < 0.001). It is concluded that the nasal vestible is very sensitive to the tactile stimulation of an airjet. This effect is highly temperature dependent being much more pronounced for air temperatures above or below the mean intranasal temperature. The temperature effect is relatively more important in the nasal cavum which is very much less sensitive to stimulation than the vestibule.     

A comparison of anterior and radical trimming of the inferior nasal turbinates and the effects on nasal resistance to airflow

A study of 18 patients with chronic rhinitis who underwent anterior or radical trimming of the inferior turbinates is presented. Radical trimming produced a significant decrease in both total nasal resistance to airflow and subjective nasal obstruction (P less than 0.005). Anterior trimming produced a significant decrease in total nasal resistance to airflow (P less than 0.05), but had no significant effect on subjective nasal obstruction. These results suggest that the main site of nasal resistance in patients with chronic rhinitis is the same as in the normal nose. On the basis of this study, adoption of anterior trimming in place of radical trimming of the inferior turbinates cannot be recommended.     

Nasal airflow receptors: the relative importance of temperature and tactile stimulation

The receptors responsible for the nasal sensation of airflow have not been identified with certainty. Although both mechanoreceptors and thermoreceptors have been implicated, evidence suggests that the nose is more sensitive to cold air than to air at body temperature. The present study was designed to investigate the relationship between the velocity and the temperature of an airjet as regards its ability to stimulate the nasal lining. Both the nasal vestibule and the nasal cavum are more sensitive to cold air than to air at mean intranasal temperature (P < 0.001). A similar effect is seen with warm air which is as stimulating as cold air. The nasal vestibule is twice as sensitive as the nasal cavum to an airjet at mean intranasal temperature (P < 0.001). It is concluded that the nasal vestible is very sensitive to the tactile stimulation of an airjet. This effect is highly temperature dependent being much more pronounced for air temperatures above or below the mean intranasal temperature. The temperature effect is relatively more important in the nasal cavum which is very much less sensitive to stimulation than the vestibule.     

Influence of nasal structure on the distribution of airflow in nasal cavity

STATEMENT OF PROBLEM: Numerical simulation of the nasal cavity is essential in order to understand the relationship between nasal structure and airflow characteristics. Since the structure of the nasal cavity varies significantly, the relationship between nasal structure and airflow characteristics will be investigated by numerical simulation of airflow in twenty-four nasal models in this paper. METHODS OF STUDY: Twenty-four three-dimensional models of the nasal cavity structure have been reconstructed on the basis of Computed Tomography medical images collected from twenty-four healthy volunteers. Modification of the turbinate has been applied to one of these models in order to simulate an operation. The results from this variant model have been compared with the original model. The numerical simulation for the airflow in the nasal cavity was performed by the finite element method. MAIN RESULTS: Pressure drop and the airflow distribution in nasal models are presented quantitatively in flow field. Main airflow will pass through the common nasal meatus. The nasal airway resistance in the region of nasal valve and nasal vestibule (flow limiting structure) accounts for 52.6%-78.3% of total nasal airway resistance. PRINCIPAL CONCLUSIONS: The numerical results show that differences in patients' nasal cavity structure may lead to different airflow distributions. Changes of nasal structure lead to variation of airflow in both sides of the nasal cavity as well as airflow redistribution in each side of the nasal cavity.     

鼻腔气流测定在鼻中隔偏曲矫正术中的应用

探讨鼻腔气流测定在鼻中隔偏曲矫正术中的应用价值。方法在鼻腔减充血状态下,采用前鼻测压法对２１例患者鼻中隔粘膜下切除术前后的双鼻腔阻力及气流进行测定并予比较。结果：发现双鼻腔气流差异率比鼻气道阻力更能反鼻通气功能,术前双鼻腔气流差异率绝对值大于５０％的患者后差,术后患者主观疗效评价与双鼻腔气流差异相关。     

Temperature profile in the nasal cavity

OBJECTIVES/HYPOTHESIS: Inspired air is heated and moistened as it passes the nasal cavity. The temperature increase should be similar to a heated tube model, depending on the airflow. STUDY DESIGN: Intranasal temperature values of 50 volunteers were measured after inspiration at different locations: nasal vestibule, nasal valve area, anterior to the head of the middle turbinate, and the nasopharynx. Temperature values were related to nasal airway resistance data. METHODS: Intranasal temperature measurements were made with a miniaturized thermocouple. Nasal airway resistance was detected by active anterior rhinomanometry. RESULTS: A logarithmic increase of air temperature from the anterior segment of the nose to the posterior part was noted. In the nasopharynx temperature was approximately 34 degrees C. The highest increase in temperature was observed in the nasal valve area. CONCLUSIONS: The temperature increase of ambient air in the nasal airways can be compared with a logarithmic curve of the heating of air passing a heated tube. As the heating of air is important for water transport, the space between the nasal valve and the middle turbinate is of special functional importance. No correlation to the results of rhinomanometry was found.