- Email: [email protected]
Forced Inspiratory Nasal Flow-Volume Curves: A Simple Test of Nasal Airflow
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Forced Inspiratory Nasal Flow–Volume Curves
Mayo Clin Proc, October 2001, Vol 76
Original Article
Forced Inspiratory Nasal Flow–Volume Curves: A Simple Test of Nasal Airflow ROBERT G. HOOPER, MD
• Objective: To observe and describe normal and abnormal inspiratory nasal flow–volume patterns. • Patients and Methods: In this observational case series, individuals with and without nasal symptoms underwent forced inspiratory nasal flow–volume (FINFV) curve measurements. The participants were volunteer adults from the staff and patients of a pulmonary subspecialty private practice office. To examine the flow patterns from the FINFV curves, definitions of normal and abnormal were established. Normal curves were defined as those from participants who had no nasal symptoms and a peak inspiratory nasal flow greater than 2.5 L/s. Abnormal curves were defined as those from participants who had 1 or more nasal symptoms, a peak inspiratory nasal flow lower than 2.5 L/s, and normal oral inspiratory flow.
• Results: Study participants consisted of 10 staff and 58 patients. Fourteen individuals (21%) met the definition of normal and had FINFV curves that mimicked the shapes of normal oral flow–volume curves; 39 (57%) met the definition of abnormal and had FINFV curves that mimicked the patterns of abnormal oral flow–volume curves. The abnormal curves showed both fixed (33/39 [85%]) and variable (6/39 [15%]) patterns of obstruction. Fifteen participants (22%) did not meet either established definition. • Conclusions: Forced inspiratory nasal flow–volume curves are a potentially useful clinical tool to measure nasal airflow. Normal and abnormal flow patterns are easily identifiable. Mayo Clin Proc. 2001;76:990-994
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during rhinomanometry requires only quiet breathing without effort. The technique has been studied and standardized. It correlates with peak inspiratory nasal flow.5 However, rhinomanometry is difficult to perform, relatively expensive specialized equipment is required, and results are not easily understood.1 Furthermore, the relationship of the results of rhinomanometry testing to clinical findings is not clear or uniformly accepted.6 The flow-volume relationship is used extensively in pulmonary function evaluations. Its widespread use evolved after flow, volume, and pressure relationships for the respiratory system were defined,7 after reports of its clinical usefulness first appeared,8,9 and after technology evolved to facilitate reliable measurements of flow. Although widely used as a measure of pulmonary function, the flow-volume relationship as a test of nasal airflow has been limited.10,11 The flow-volume relationship measured nasally has not been established for healthy subjects or for those with nasal or respiratory diseases. Additionally, a standard text in the field of otolaryngology does not mention the flow-volume relationship as a test of nasal function.1 The purposes of this observational report were to point out the usefulness of the FINFV curve as a technique for studying nasal obstruction, to describe the patterns of flow seen in normal and abnormal situations, and to relate the factors to be considered when FINFV curves are being measured.
asal symptoms are commonly encountered in clinical practice and frequently accompany respiratory problems, such as bronchial asthma and sleep apnea syndrome. No standard method for measuring nasal airflow has been widely accepted or used.1 I have used the forced inspiratory nasal flow–volume (FINFV) curve to assess nasal airflow and have found that it is an easy, reliable measurement for evaluating nasal airflow. Usually in clinical practice nasal patency is measured by either peak inspiratory nasal flow or rhinomanometry. Peak inspiratory nasal flow has been standardized, and normal values have been reported.2-4 It is an easy test to perform, and only simple equipment is needed. However, it is effort dependent, only a single measure of flow for the entire spectrum of vital capacity is obtained, and it does not visually represent flow. Furthermore, the correlation of changes in peak inspiratory nasal flow and symptoms has been debated.3,4 Rhinomanometry has advantages and disadvantages.1,5,6 The transnasal pressure and flow relationship developed From Arizona Lung and Critical Care Specialists, Scottsdale. Presented in part as a poster at the annual meeting of the American College of Chest Physicians, Chicago, Ill, October 31-November 4, 1999. Address reprint requests and correspondence to Robert G. Hooper, MD, PO Box 4100, Scottsdale, AZ 85261 (e-mail: [email protected]). Mayo Clin Proc. 2001;76:990-994
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© 2001 Mayo Foundation for Medical Education and Research
For personal use. Mass reproduce only with permission from Mayo Clinic Proceedings.
Mayo Clin Proc, October 2001, Vol 76
Techniques Nasal airflow was measured through a nasal constant positive airway pressure mask (Respironics) connected to 1 of 2 spirometers (MicroLoop II, Micro Medical Ltd or a Keystone Pulmonary Function Testing System, S & M Medical Supply, Inc). Neither instrument was designed to measure nasal flow. Both allowed measurement and recording of flow by using standard spirometry software programs supplied with the equipment. A test protocol was established through trial and error before tests reported in this article were initiated. The software programs of the spirometers dictated how nasal testing would be performed. To measure inspiratory flow, both instruments required the maneuver to begin at full inspiration, followed by full exhalation, and then completed with full inspiration. The test was performed by placing the mask on a participant’s nose and having it held in place by the technician or participant. Participants were instructed to keep their mouth closed during the test. All breathing was nasally. After full inspiration was performed, the testing sequence on the instrument was initiated. Then a nonforced full expiratory vital capacity was performed, followed by a forced inspiratory capacity to complete the test. Curves were accepted when repeated efforts demonstrated reproduction of the flow pattern on the FINFV curve. Peak forced inspiratory nasal flow was measured from the flow-volume curve. A flow greater than 2.5 L/s was considered normal oral inspiratory flow. Data Analysis A definition of normal and abnormal nasal flow situations was established to determine the appearance of the respective FINFV curves. Normal FINFV curves were defined as those from participants with no nasal symptoms who had a peak inspiratory nasal flow greater than 2.5 L/s. Abnormal curves were defined as those from participants
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Table 1. Characteristics of Participants’ Symptom Status, Nasal Airflow, and Oral Airflow Peak inspiratory nasal flow
Asymptomatic (No.)
Symptomatic (No.)
Total
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43 4 68
Normal Normal oral flow Reduced oral flow Reduced Normal oral flow Reduced oral flow Total
*Participants who met the definition of normal. †Participants who met the definition of abnormal.
with 1 or more nasal symptoms, a peak inspiratory nasal flow lower than 2.5 L/s, and normal oral inspiratory flow. Other situations included (1) symptoms with normal peak flows, (2) no symptoms and reduced peak flows, and (3) reduced nasal peak flows and reduced oral flows. RESULTS The 68 study participants consisted of 45 men and 23 women ranging in age from 22 to 87 years (mean, 53.9 years); 58 were patients, and 10 were staff members. No nasal symptoms were reported by 18 participants, whereas 50 had active complaints. Therefore, 68 FINFV curves formed the basis of this report. The separation of participants by the definitions used resulted in 14 (21%) who met the definition of normal, 39 (57%) who met the definition of abnormal, and 15 (22%) who did not meet either definition (Table 1). Of the 15 who did not meet the definition of normal or abnormal, 4 (27%) were asymptomatic with normal oral flow but had reduced peak inspiratory nasal flow, 7 (46%) were symptomatic with normal oral flow but had normal peak inspiratory nasal flow, and 4 (27%) had symptoms with reduced peak nasal flow but had reduced oral inspiratory flow. The normal FINFV curves had shapes that mimicked those of normal oral inspiratory flow–volume curves (Figure 1).7-9 Some variability in the shapes of the curves was
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PATIENTS AND METHODS Initially, techniques for performing nasal flow–volume curves were practiced on me and on a pulmonary technician until a suitable method was established. Once the technique was established, FINFV curves were performed on individuals recruited from patients and staff of a private practice pulmonary medicine office. Study participants included those with and those without nasal symptoms. The presence or absence of nasal symptoms was recorded. Participants were asked if they were currently having difficulty with breathing through the nose, nasal obstruction, nasal congestion, or nasal hay fever problems. Oral respiratory functions were measured. The records and curves were analyzed to form the basis of this report.
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Figure 1. Three forced inspiratory nasal flow–volume curves from the normal group (see text for definitions).
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Figure 2. Three forced inspiratory nasal flow–volume curves showing fixed airflow obstruction. Of the 39 abnormal curves, 33 (85%) showed this pattern of flow (see text for definitions).
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observed despite normal peak inspiratory flow being achieved. Two types of abnormal curves were recognized that mimicked the shapes of known abnormal oral flow–volume curves (fixed and variable obstruction).8,9 The most common type (33/39 [85%]) showed a long plateau of flow, characteristic of fixed airflow obstruction (Figure 2). The degree of flow limitation seen with the plateau pattern varied from mild (a peak inspiratory flow of 2.5 L/ s) to levels that were less than 1 L/s. An example of the degree of obstruction in the nasal passages is shown in Figure 3. The variable pattern of flow was noted less frequently (6 of 39 obstructions) and suggests changing obstruction (Figure 4). In this pattern the flow begins, peaks, and then reduces rapidly before full inspiration is completed. In all 6 variable patterns of flow, the inspiratory flow stopped long before the full inspiratory vital capacity had been reached. Four participants had abnormal nasal flow and abnormal oral airflow. They had symptoms of nasal obstruction and associated severe chronic obstructive pulmonary disease (Figure 5).
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Figure 3. Symptomatic patient with fixed nasal inspiratory airflow obstruction on forced inspiratory nasal flow–volume curve. Forced inspiratory flow is 1.2 L/s. Nasal passages on computed tomographic scan show enlarged turbinates with narrowed nasal lumen.
DISCUSSION Although symptoms of nasal obstruction are common in medical practice, clinical techniques to measure nasal airflow are limited.1-6 The FINFV curve, as demonstrated in this article, has the potential to be a useful tool to measure nasal airflow. Normal and abnormal flow patterns are recognizable, and the technique is easy to perform. In an attempt to establish a routine technique for nasal flow–volume curves, I noticed that both subjects and technicians preferred the forced inspiratory maneuver over a forced expiratory effort. The reason cited by both groups was that expiration of secretions during the expiratory effort was disagreeable and interfered with efforts. Although this reason should not prevent the performance of expiratory nasal flows, it impaired the efficiency and quality of the test efforts. In addition, inspiratory nasal symptoms seem to be far more frequent in clinical practice. For these reasons, the test selected for this study was the FINFV curve. Expiratory curves have been reported and can be performed. However, in my experience their use prolongs testing time and frequently results in nonreproducible curves. Although the appearance of both normal and abnormal FINFV curves can be anticipated based on a knowledge of normal oral flow, normal curves have not been defined.10,11 The expected appearance can be established by defining representative situations of normal and abnormal nasal flow. For this purpose, normal was defined as the absence of symptoms and the presence of a normal peak nasal flow for which established values are available.2 Abnormal was defined as the presence of symptoms, a reduced peak nasal flow rate, and normal oral inspiratory flow. These definitions were meant to be restrictive enough to include only normal individuals in the normal group and abnormal ones in the abnormal group. Grouping the curves in this manner helped define what shape of curve might be expected. However, further systematic study is needed to understand FINFV measurements fully. Inspiratory flow measurements have known limitations. All inspiratory flow is directly related to the inspiratory force provided by the respiratory muscles.7 The measurement of inspiratory flow requires attention to inspiratory effort, compliance with testing techniques, and followthrough by patients and technicians when testing is performed. Reductions in inspiratory flow should not be accepted without repeated duplication of the findings. Alternative methods to verify good inspiratory effort may be developed, but for now observations of apparent effort and reproducibility are the only clinical techniques available to confirm an adequate driving pressure. Measuring oral inspiratory flow at the same testing session as nasal inspiratory flow is necessary to assess the ability of the respiratory muscles to generate inspiratory
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Figure 4. Three forced inspiratory nasal flow–volume curves showing a variable pattern of obstruction to airflow. Of the 39 obstructions, 6 (15%) showed this pattern (see text for definitions).
muscles, tracheobronchial obstructions, or hypopharyngeal obstructions are possible reasons for low forced inspiratory nasal flow, rather than an obstruction of the nasal passage. Certainly, less-clear examples should be expected, and further definition of the expected differences in oral and nasal flow must be developed. The 2 groups of FINFV curves that were excluded from analysis require comment (individuals with symptoms and normal forced nasal inspiratory flow and those without symptoms and abnormal forced nasal inspiratory flow). They represent the problem of symptom perception or reporting as opposed to finding measurable abnormalities. I observed severe reduced inspiratory nasal flow (<1.0 L/s) without symptoms. In addition, severe nasal obstruction symptoms occurred with measured inspiratory nasal flow similar to normals (Figure 1). The implications of these situations could be important. They suggest that symptom awareness and measurable obstruction do not always accompany each other. The FINFV curves reported in this article were measured in a clinical practice in an observational manner, and therefore this study has several limitations. The FINFV curve is an alternative method for recording nasal flow by using a physical maneuver similar to the measurement of
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flow.10,11 A test of oral inspiratory flow provided the participant and the technician with a baseline experience with inspiratory testing and a baseline inspiratory flow curve for the respiratory system. Unfortunately, the best method to perform inspiratory flow testing is debatable.12 Most technicians are familiar with the oral inspiratory flow loop, and performing a baseline test allows technicians an opportunity to judge the patient’s ability to perform the maneuver. Not surprisingly, the flow pattern in the group that met our definition of normal mimicked the pattern of flow seen with orally measured flow.7-9 Nasal inspiratory flow in this group generally appeared as a rounded to somewhat flattened pattern of flow (Figure 1). A systematic measurement of the differences between nasal flow and oral flow was not performed but was seen to vary from 2 to 4 L/s in mid inspiration. Abnormal forced nasal inspiratory flows most commonly suggested a fixed airway obstruction (Figure 2).8,9 Fixed obstructive patterns would be expected with mechanical obstruction of the nasal passages. The nose primarily acts as a fixed limitation to airflow. Anatomical changes and diseases can narrow the air passages by reducing their cross-sectional area (Figure 3). Nasal septal deviation, nasal polyps, and swollen turbinates are all reasons for nasal obstructive symptoms. A pattern of variable flow obstruction was seen infrequently (Figure 4). The common diagnosis in these patients was allergic rhinitis, and the curves with variable flow were recorded during active symptoms. The mechanism of obstruction was unclear, but the pattern consisted of initially reduced flow, followed by sudden termination of flow before the full vital capacity was inspired. Although driving pressure is a concern with all abnormal inspiratory flow curves, the changes seen with the variable pattern raise the issue of adequate inspiratory driving pressure and patient effort most dramatically. The curves were reproducible, and the patients appeared to be giving full effort. However, physiologic confirmation of adequate driving pressure was not obtained, and more complete physiologic evaluation of this type of patient should be performed. Likewise, the reason for dynamic obstruction requires further study. Movements of nasal polyps, the soft palate, the uvula, the area of the nasal valve, and other dynamic mechanisms are all considerations. A pronounced reduction in the ability of the respiratory system to perform inspiratory efforts reduces the inspiratory nasal airflow. If a patient has both nasal and respiratory problems, measurements of nasal flow may be misleading without an oral flow for comparison. Because nasal flow does not exceed oral flow, a substantial reduction in oral inspiratory flow results in a decrease in nasal flow (Figure 5). In these situations, it is clear that respiratory
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Figure 5. Forced inspiratory flow–volume curves from a participant with symptoms of nasal obstruction and known severe chronic obstructive pulmonary disease. Note the similarity in the 2 curves and the reduction in inspiratory flow measured with the oral flow–volume curve. The nasal curve appears abnormal, and the peak inspiratory nasal flow is reduced. However, the nasal flow is only slightly less than the oral flow.
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Forced Inspiratory Nasal Flow–Volume Curves
peak inspiratory flow. I have demonstrated flow patterns in normal and abnormal situations. However, this work cannot and does not define normal nasal flow. My definitions were selected to identify populations that would generally be accepted as abnormal (symptoms, reduced peak nasal inspiratory flow, and normal oral inspiratory flow) and normal (no symptoms, normal peak nasal inspiratory flow, and normal oral inspiratory flow). Criteria that can clearly separate normals from abnormals are unknown, and defining the border, ie, defining the separation of abnormals from normals, is beyond the ability of my observations. Although symptoms were used to help define normal and abnormal curves, no attempt was made to correlate symptoms or severity of symptoms with the measured flow. The relationship of symptoms to forced inspiratory nasal flow measured with the FINFV curve remains to be determined. Additionally, nasal flow varies with time. The nose has expansible tissue; the nasal valve can collapse or open with forced inspiratory efforts. Intermittent inflammatory disease can cause swelling of the nasal passage. All these factors can cause changes in nasal airway size and potentially change nasal airflow. Carefully planned and timed evaluation of patient histories, peak inspiratory nasal flow rates, rhinomanometry, FINFV curves, and oral forced inspiratory flow–volume curves as well as structural evaluation of actual nasal airway sizes are necessary to address these issues. CONCLUSIONS The FINFV curve can be a valuable technique for evaluating the nasal airway for obstruction. It is easy to perform and well tolerated. Use of the technique requires a full understanding of the mechanisms of inspiratory flow because both reduced effort and reduced respiratory ability can affect the results. The technique requires repeated ef-
Mayo Clin Proc, October 2001, Vol 76
forts to ensure reproducibility and should be performed with an oral flow–volume loop. Although work remains to be done to refine the technique, to establish normal values, to assess variations over time, to explore the relationship between symptoms and nasal flow, and to define the effects of reduced nasal flow in various clinical situations, I have found that FINFV curves are clinically helpful for evaluating nasal airway obstruction. REFERENCES 1.
2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.
Pallanch JF, McCaffrey TV, Kern EB. Evaluation of nasal breathing function with objective airway testing. In: Cummings CW, Fredrickson JM, Harker LA, Krause CJ, Schuller DE, Richardson MA, eds. Otolaryngology—Head & Neck Surgery. Vol 2. 3rd ed. St Louis, Mo: Mosby; 1998:799-832. Cho SI, Hauser R, Christiani DC. Reproducibility of nasal peak inspiratory flow among healthy adults: assessment of epidemiologic utility. Chest. 1997;112:1547-1553. Enberg RN, Ownby DR. Peak nasal inspiratory flow and Wright peak flow: a comparison of their reproducibility. Ann Allergy. 1991;67:371-374. Fairley JW, Durham LH, Ell SR. Correlation of subjective sensation of nasal patency with nasal inspiratory peak flow rate. Clin Otolaryngol. 1993;18:19-22. Jones AS, Viani L, Phillips D, Charters P. The objective assessment of nasal patency. Clin Otolaryngol. 1991;16:206-211. Yaniv E, Hadar T, Shvero J, Raveh E. Objective and subjective nasal airflow. Am J Otolaryngol. 1997;18:29-32. Fry DL, Hyatt RE. Pulmonary mechanics: a unified analysis of the relationship between pressure, volume and gasflow in the lungs of normal and diseased human subjects. Am J Med. 1960;29:672-689. Miller RD, Hyatt RE. Obstructing lesions of the larynx and trachea: clinical and physiologic characteristics. Mayo Clin Proc. 1969;44: 145-161. Hyatt RE, Black LF. The flow-volume curve: a current perspective. Am Rev Respir Dis. 1973;107:191-199. Pertuze J, Watson A, Pride NB. Maximum airflow through the nose in humans. J Appl Physiol. 1991;70:1369-1376. Phagoo SB, Watson RA, Pride NB. Use of nasal peak flow to assess nasal patency. Allergy. 1997;52:901-908. Ewald FW Jr, Tenholder MF, Waller RF. Analysis of the inspiratory flow-volume curve: should it always precede the forced expiratory maneuver? Chest. 1994;106:814-818.
For personal use. Mass reproduce only with permission from Mayo Clinic Proceedings.
Forced Inspiratory Nasal Flow–Volume Curves
Mayo Clin Proc, October 2001, Vol 76
Original Article
Forced Inspiratory Nasal Flow–Volume Curves: A Simple Test of Nasal Airflow ROBERT G. HOOPER, MD
• Objective: To observe and describe normal and abnormal inspiratory nasal flow–volume patterns. • Patients and Methods: In this observational case series, individuals with and without nasal symptoms underwent forced inspiratory nasal flow–volume (FINFV) curve measurements. The participants were volunteer adults from the staff and patients of a pulmonary subspecialty private practice office. To examine the flow patterns from the FINFV curves, definitions of normal and abnormal were established. Normal curves were defined as those from participants who had no nasal symptoms and a peak inspiratory nasal flow greater than 2.5 L/s. Abnormal curves were defined as those from participants who had 1 or more nasal symptoms, a peak inspiratory nasal flow lower than 2.5 L/s, and normal oral inspiratory flow.
• Results: Study participants consisted of 10 staff and 58 patients. Fourteen individuals (21%) met the definition of normal and had FINFV curves that mimicked the shapes of normal oral flow–volume curves; 39 (57%) met the definition of abnormal and had FINFV curves that mimicked the patterns of abnormal oral flow–volume curves. The abnormal curves showed both fixed (33/39 [85%]) and variable (6/39 [15%]) patterns of obstruction. Fifteen participants (22%) did not meet either established definition. • Conclusions: Forced inspiratory nasal flow–volume curves are a potentially useful clinical tool to measure nasal airflow. Normal and abnormal flow patterns are easily identifiable. Mayo Clin Proc. 2001;76:990-994
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during rhinomanometry requires only quiet breathing without effort. The technique has been studied and standardized. It correlates with peak inspiratory nasal flow.5 However, rhinomanometry is difficult to perform, relatively expensive specialized equipment is required, and results are not easily understood.1 Furthermore, the relationship of the results of rhinomanometry testing to clinical findings is not clear or uniformly accepted.6 The flow-volume relationship is used extensively in pulmonary function evaluations. Its widespread use evolved after flow, volume, and pressure relationships for the respiratory system were defined,7 after reports of its clinical usefulness first appeared,8,9 and after technology evolved to facilitate reliable measurements of flow. Although widely used as a measure of pulmonary function, the flow-volume relationship as a test of nasal airflow has been limited.10,11 The flow-volume relationship measured nasally has not been established for healthy subjects or for those with nasal or respiratory diseases. Additionally, a standard text in the field of otolaryngology does not mention the flow-volume relationship as a test of nasal function.1 The purposes of this observational report were to point out the usefulness of the FINFV curve as a technique for studying nasal obstruction, to describe the patterns of flow seen in normal and abnormal situations, and to relate the factors to be considered when FINFV curves are being measured.
asal symptoms are commonly encountered in clinical practice and frequently accompany respiratory problems, such as bronchial asthma and sleep apnea syndrome. No standard method for measuring nasal airflow has been widely accepted or used.1 I have used the forced inspiratory nasal flow–volume (FINFV) curve to assess nasal airflow and have found that it is an easy, reliable measurement for evaluating nasal airflow. Usually in clinical practice nasal patency is measured by either peak inspiratory nasal flow or rhinomanometry. Peak inspiratory nasal flow has been standardized, and normal values have been reported.2-4 It is an easy test to perform, and only simple equipment is needed. However, it is effort dependent, only a single measure of flow for the entire spectrum of vital capacity is obtained, and it does not visually represent flow. Furthermore, the correlation of changes in peak inspiratory nasal flow and symptoms has been debated.3,4 Rhinomanometry has advantages and disadvantages.1,5,6 The transnasal pressure and flow relationship developed From Arizona Lung and Critical Care Specialists, Scottsdale. Presented in part as a poster at the annual meeting of the American College of Chest Physicians, Chicago, Ill, October 31-November 4, 1999. Address reprint requests and correspondence to Robert G. Hooper, MD, PO Box 4100, Scottsdale, AZ 85261 (e-mail: [email protected]). Mayo Clin Proc. 2001;76:990-994
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Mayo Clin Proc, October 2001, Vol 76
Techniques Nasal airflow was measured through a nasal constant positive airway pressure mask (Respironics) connected to 1 of 2 spirometers (MicroLoop II, Micro Medical Ltd or a Keystone Pulmonary Function Testing System, S & M Medical Supply, Inc). Neither instrument was designed to measure nasal flow. Both allowed measurement and recording of flow by using standard spirometry software programs supplied with the equipment. A test protocol was established through trial and error before tests reported in this article were initiated. The software programs of the spirometers dictated how nasal testing would be performed. To measure inspiratory flow, both instruments required the maneuver to begin at full inspiration, followed by full exhalation, and then completed with full inspiration. The test was performed by placing the mask on a participant’s nose and having it held in place by the technician or participant. Participants were instructed to keep their mouth closed during the test. All breathing was nasally. After full inspiration was performed, the testing sequence on the instrument was initiated. Then a nonforced full expiratory vital capacity was performed, followed by a forced inspiratory capacity to complete the test. Curves were accepted when repeated efforts demonstrated reproduction of the flow pattern on the FINFV curve. Peak forced inspiratory nasal flow was measured from the flow-volume curve. A flow greater than 2.5 L/s was considered normal oral inspiratory flow. Data Analysis A definition of normal and abnormal nasal flow situations was established to determine the appearance of the respective FINFV curves. Normal FINFV curves were defined as those from participants with no nasal symptoms who had a peak inspiratory nasal flow greater than 2.5 L/s. Abnormal curves were defined as those from participants
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Table 1. Characteristics of Participants’ Symptom Status, Nasal Airflow, and Oral Airflow Peak inspiratory nasal flow
Asymptomatic (No.)
Symptomatic (No.)
Total
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21 0
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43 4 68
Normal Normal oral flow Reduced oral flow Reduced Normal oral flow Reduced oral flow Total
*Participants who met the definition of normal. †Participants who met the definition of abnormal.
with 1 or more nasal symptoms, a peak inspiratory nasal flow lower than 2.5 L/s, and normal oral inspiratory flow. Other situations included (1) symptoms with normal peak flows, (2) no symptoms and reduced peak flows, and (3) reduced nasal peak flows and reduced oral flows. RESULTS The 68 study participants consisted of 45 men and 23 women ranging in age from 22 to 87 years (mean, 53.9 years); 58 were patients, and 10 were staff members. No nasal symptoms were reported by 18 participants, whereas 50 had active complaints. Therefore, 68 FINFV curves formed the basis of this report. The separation of participants by the definitions used resulted in 14 (21%) who met the definition of normal, 39 (57%) who met the definition of abnormal, and 15 (22%) who did not meet either definition (Table 1). Of the 15 who did not meet the definition of normal or abnormal, 4 (27%) were asymptomatic with normal oral flow but had reduced peak inspiratory nasal flow, 7 (46%) were symptomatic with normal oral flow but had normal peak inspiratory nasal flow, and 4 (27%) had symptoms with reduced peak nasal flow but had reduced oral inspiratory flow. The normal FINFV curves had shapes that mimicked those of normal oral inspiratory flow–volume curves (Figure 1).7-9 Some variability in the shapes of the curves was
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PATIENTS AND METHODS Initially, techniques for performing nasal flow–volume curves were practiced on me and on a pulmonary technician until a suitable method was established. Once the technique was established, FINFV curves were performed on individuals recruited from patients and staff of a private practice pulmonary medicine office. Study participants included those with and those without nasal symptoms. The presence or absence of nasal symptoms was recorded. Participants were asked if they were currently having difficulty with breathing through the nose, nasal obstruction, nasal congestion, or nasal hay fever problems. Oral respiratory functions were measured. The records and curves were analyzed to form the basis of this report.
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Figure 1. Three forced inspiratory nasal flow–volume curves from the normal group (see text for definitions).
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Figure 2. Three forced inspiratory nasal flow–volume curves showing fixed airflow obstruction. Of the 39 abnormal curves, 33 (85%) showed this pattern of flow (see text for definitions).
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observed despite normal peak inspiratory flow being achieved. Two types of abnormal curves were recognized that mimicked the shapes of known abnormal oral flow–volume curves (fixed and variable obstruction).8,9 The most common type (33/39 [85%]) showed a long plateau of flow, characteristic of fixed airflow obstruction (Figure 2). The degree of flow limitation seen with the plateau pattern varied from mild (a peak inspiratory flow of 2.5 L/ s) to levels that were less than 1 L/s. An example of the degree of obstruction in the nasal passages is shown in Figure 3. The variable pattern of flow was noted less frequently (6 of 39 obstructions) and suggests changing obstruction (Figure 4). In this pattern the flow begins, peaks, and then reduces rapidly before full inspiration is completed. In all 6 variable patterns of flow, the inspiratory flow stopped long before the full inspiratory vital capacity had been reached. Four participants had abnormal nasal flow and abnormal oral airflow. They had symptoms of nasal obstruction and associated severe chronic obstructive pulmonary disease (Figure 5).
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Figure 3. Symptomatic patient with fixed nasal inspiratory airflow obstruction on forced inspiratory nasal flow–volume curve. Forced inspiratory flow is 1.2 L/s. Nasal passages on computed tomographic scan show enlarged turbinates with narrowed nasal lumen.
DISCUSSION Although symptoms of nasal obstruction are common in medical practice, clinical techniques to measure nasal airflow are limited.1-6 The FINFV curve, as demonstrated in this article, has the potential to be a useful tool to measure nasal airflow. Normal and abnormal flow patterns are recognizable, and the technique is easy to perform. In an attempt to establish a routine technique for nasal flow–volume curves, I noticed that both subjects and technicians preferred the forced inspiratory maneuver over a forced expiratory effort. The reason cited by both groups was that expiration of secretions during the expiratory effort was disagreeable and interfered with efforts. Although this reason should not prevent the performance of expiratory nasal flows, it impaired the efficiency and quality of the test efforts. In addition, inspiratory nasal symptoms seem to be far more frequent in clinical practice. For these reasons, the test selected for this study was the FINFV curve. Expiratory curves have been reported and can be performed. However, in my experience their use prolongs testing time and frequently results in nonreproducible curves. Although the appearance of both normal and abnormal FINFV curves can be anticipated based on a knowledge of normal oral flow, normal curves have not been defined.10,11 The expected appearance can be established by defining representative situations of normal and abnormal nasal flow. For this purpose, normal was defined as the absence of symptoms and the presence of a normal peak nasal flow for which established values are available.2 Abnormal was defined as the presence of symptoms, a reduced peak nasal flow rate, and normal oral inspiratory flow. These definitions were meant to be restrictive enough to include only normal individuals in the normal group and abnormal ones in the abnormal group. Grouping the curves in this manner helped define what shape of curve might be expected. However, further systematic study is needed to understand FINFV measurements fully. Inspiratory flow measurements have known limitations. All inspiratory flow is directly related to the inspiratory force provided by the respiratory muscles.7 The measurement of inspiratory flow requires attention to inspiratory effort, compliance with testing techniques, and followthrough by patients and technicians when testing is performed. Reductions in inspiratory flow should not be accepted without repeated duplication of the findings. Alternative methods to verify good inspiratory effort may be developed, but for now observations of apparent effort and reproducibility are the only clinical techniques available to confirm an adequate driving pressure. Measuring oral inspiratory flow at the same testing session as nasal inspiratory flow is necessary to assess the ability of the respiratory muscles to generate inspiratory
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Figure 4. Three forced inspiratory nasal flow–volume curves showing a variable pattern of obstruction to airflow. Of the 39 obstructions, 6 (15%) showed this pattern (see text for definitions).
muscles, tracheobronchial obstructions, or hypopharyngeal obstructions are possible reasons for low forced inspiratory nasal flow, rather than an obstruction of the nasal passage. Certainly, less-clear examples should be expected, and further definition of the expected differences in oral and nasal flow must be developed. The 2 groups of FINFV curves that were excluded from analysis require comment (individuals with symptoms and normal forced nasal inspiratory flow and those without symptoms and abnormal forced nasal inspiratory flow). They represent the problem of symptom perception or reporting as opposed to finding measurable abnormalities. I observed severe reduced inspiratory nasal flow (<1.0 L/s) without symptoms. In addition, severe nasal obstruction symptoms occurred with measured inspiratory nasal flow similar to normals (Figure 1). The implications of these situations could be important. They suggest that symptom awareness and measurable obstruction do not always accompany each other. The FINFV curves reported in this article were measured in a clinical practice in an observational manner, and therefore this study has several limitations. The FINFV curve is an alternative method for recording nasal flow by using a physical maneuver similar to the measurement of
Oral 1
Flow (L/s)
flow.10,11 A test of oral inspiratory flow provided the participant and the technician with a baseline experience with inspiratory testing and a baseline inspiratory flow curve for the respiratory system. Unfortunately, the best method to perform inspiratory flow testing is debatable.12 Most technicians are familiar with the oral inspiratory flow loop, and performing a baseline test allows technicians an opportunity to judge the patient’s ability to perform the maneuver. Not surprisingly, the flow pattern in the group that met our definition of normal mimicked the pattern of flow seen with orally measured flow.7-9 Nasal inspiratory flow in this group generally appeared as a rounded to somewhat flattened pattern of flow (Figure 1). A systematic measurement of the differences between nasal flow and oral flow was not performed but was seen to vary from 2 to 4 L/s in mid inspiration. Abnormal forced nasal inspiratory flows most commonly suggested a fixed airway obstruction (Figure 2).8,9 Fixed obstructive patterns would be expected with mechanical obstruction of the nasal passages. The nose primarily acts as a fixed limitation to airflow. Anatomical changes and diseases can narrow the air passages by reducing their cross-sectional area (Figure 3). Nasal septal deviation, nasal polyps, and swollen turbinates are all reasons for nasal obstructive symptoms. A pattern of variable flow obstruction was seen infrequently (Figure 4). The common diagnosis in these patients was allergic rhinitis, and the curves with variable flow were recorded during active symptoms. The mechanism of obstruction was unclear, but the pattern consisted of initially reduced flow, followed by sudden termination of flow before the full vital capacity was inspired. Although driving pressure is a concern with all abnormal inspiratory flow curves, the changes seen with the variable pattern raise the issue of adequate inspiratory driving pressure and patient effort most dramatically. The curves were reproducible, and the patients appeared to be giving full effort. However, physiologic confirmation of adequate driving pressure was not obtained, and more complete physiologic evaluation of this type of patient should be performed. Likewise, the reason for dynamic obstruction requires further study. Movements of nasal polyps, the soft palate, the uvula, the area of the nasal valve, and other dynamic mechanisms are all considerations. A pronounced reduction in the ability of the respiratory system to perform inspiratory efforts reduces the inspiratory nasal airflow. If a patient has both nasal and respiratory problems, measurements of nasal flow may be misleading without an oral flow for comparison. Because nasal flow does not exceed oral flow, a substantial reduction in oral inspiratory flow results in a decrease in nasal flow (Figure 5). In these situations, it is clear that respiratory
Forced Inspiratory Nasal Flow–Volume Curves
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2 4
2
Nasal 3
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2
3
2 4
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Figure 5. Forced inspiratory flow–volume curves from a participant with symptoms of nasal obstruction and known severe chronic obstructive pulmonary disease. Note the similarity in the 2 curves and the reduction in inspiratory flow measured with the oral flow–volume curve. The nasal curve appears abnormal, and the peak inspiratory nasal flow is reduced. However, the nasal flow is only slightly less than the oral flow.
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peak inspiratory flow. I have demonstrated flow patterns in normal and abnormal situations. However, this work cannot and does not define normal nasal flow. My definitions were selected to identify populations that would generally be accepted as abnormal (symptoms, reduced peak nasal inspiratory flow, and normal oral inspiratory flow) and normal (no symptoms, normal peak nasal inspiratory flow, and normal oral inspiratory flow). Criteria that can clearly separate normals from abnormals are unknown, and defining the border, ie, defining the separation of abnormals from normals, is beyond the ability of my observations. Although symptoms were used to help define normal and abnormal curves, no attempt was made to correlate symptoms or severity of symptoms with the measured flow. The relationship of symptoms to forced inspiratory nasal flow measured with the FINFV curve remains to be determined. Additionally, nasal flow varies with time. The nose has expansible tissue; the nasal valve can collapse or open with forced inspiratory efforts. Intermittent inflammatory disease can cause swelling of the nasal passage. All these factors can cause changes in nasal airway size and potentially change nasal airflow. Carefully planned and timed evaluation of patient histories, peak inspiratory nasal flow rates, rhinomanometry, FINFV curves, and oral forced inspiratory flow–volume curves as well as structural evaluation of actual nasal airway sizes are necessary to address these issues. CONCLUSIONS The FINFV curve can be a valuable technique for evaluating the nasal airway for obstruction. It is easy to perform and well tolerated. Use of the technique requires a full understanding of the mechanisms of inspiratory flow because both reduced effort and reduced respiratory ability can affect the results. The technique requires repeated ef-
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forts to ensure reproducibility and should be performed with an oral flow–volume loop. Although work remains to be done to refine the technique, to establish normal values, to assess variations over time, to explore the relationship between symptoms and nasal flow, and to define the effects of reduced nasal flow in various clinical situations, I have found that FINFV curves are clinically helpful for evaluating nasal airway obstruction. REFERENCES 1.
2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.
Pallanch JF, McCaffrey TV, Kern EB. Evaluation of nasal breathing function with objective airway testing. In: Cummings CW, Fredrickson JM, Harker LA, Krause CJ, Schuller DE, Richardson MA, eds. Otolaryngology—Head & Neck Surgery. Vol 2. 3rd ed. St Louis, Mo: Mosby; 1998:799-832. Cho SI, Hauser R, Christiani DC. Reproducibility of nasal peak inspiratory flow among healthy adults: assessment of epidemiologic utility. Chest. 1997;112:1547-1553. Enberg RN, Ownby DR. Peak nasal inspiratory flow and Wright peak flow: a comparison of their reproducibility. Ann Allergy. 1991;67:371-374. Fairley JW, Durham LH, Ell SR. Correlation of subjective sensation of nasal patency with nasal inspiratory peak flow rate. Clin Otolaryngol. 1993;18:19-22. Jones AS, Viani L, Phillips D, Charters P. The objective assessment of nasal patency. Clin Otolaryngol. 1991;16:206-211. Yaniv E, Hadar T, Shvero J, Raveh E. Objective and subjective nasal airflow. Am J Otolaryngol. 1997;18:29-32. Fry DL, Hyatt RE. Pulmonary mechanics: a unified analysis of the relationship between pressure, volume and gasflow in the lungs of normal and diseased human subjects. Am J Med. 1960;29:672-689. Miller RD, Hyatt RE. Obstructing lesions of the larynx and trachea: clinical and physiologic characteristics. Mayo Clin Proc. 1969;44: 145-161. Hyatt RE, Black LF. The flow-volume curve: a current perspective. Am Rev Respir Dis. 1973;107:191-199. Pertuze J, Watson A, Pride NB. Maximum airflow through the nose in humans. J Appl Physiol. 1991;70:1369-1376. Phagoo SB, Watson RA, Pride NB. Use of nasal peak flow to assess nasal patency. Allergy. 1997;52:901-908. Ewald FW Jr, Tenholder MF, Waller RF. Analysis of the inspiratory flow-volume curve: should it always precede the forced expiratory maneuver? Chest. 1994;106:814-818.
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