The cause of brachycephalic syndrome in dogs is usually unknown. It is speculated that an increase in RNA is the underlying cause,1,2 although the final proof of this hypothesis has not been provided. It is assumed that increased RNA causes various soft tissues to be drawn into the lumen by the air stream, which leads to airway obstruction. Typical clinical findings of dogs with brachycephalic syndrome are stenotic nostrils, an elongated soft palate, enlarged tonsils, everted lateral saccules of the larynx, narrowed rima glottidis, and laryngeal collapse.3,4 Each of these findings may be detected alone or in combination and, depending on the degree of severity, may be manifested as light snoring, inspiratory stridor, or even as fatal asphyxiation.
Brachycephalic syndrome is nearly exclusively limited to brachycephalic dogs. However, the development of clinical signs varies considerably among breeds and among dogs of the same breed. There are also reports5–8 of brachycephalic syndrome in nonbrachycephalic breeds.
Rhinomanometry is the method commonly used to determine RNA calculated from simultaneous measurement of Qv and PNA. The pressure immediately in front of the nostrils and the pressure in the nasopharynx are measured to determine PNA. Airflow is measured by use of a flow meter attached to a breathing mask that has been placed tightly over the nose. Two methods can be used (posterior and anterior rhinomanometry). When Qv is generated by the respiratory cycle, the method is referred to as active rhinomanometry, whereas when Qv is driven by an extrinsic source, the method is referred to as passive rhinomanometry.
For posterior rhinomanometry, nasopharyngeal pressure is measured by a pressure-sensing tube placed into the nasopharynx (transorally or through one of the nasal airways). Alternatively, in experimental settings, the tube may be placed directly into the nasopharynx by use of a piercing canula. With posterior rhinomanometry, both airways are investigated simultaneously and combined RNA assessed directly.9 In dogs, the mouth may remain open, which allows transoral intubation and surveillance of the tip of the pressure sensor to ensure it does not come in contact with the soft tissues of the nasopharynx.
In anterior rhinomanometry, the nasal passages are investigated unilaterally. Air is fed into 1 nostril (ie, the airway being investigated) while a pressure probe placed in the contralateral nostril tightly closes that nasal passage. In this manner, pressure measured at the seal of the closed passage equals the pressure at the unification of the 2 nasal passages in the nasopharynx. Thus, the pressure difference measured between the entrance of the active passage and the closed nostril is the decisive pressure difference of the passage being investigated. Both nasal passages are measured successively, and combined RNA is calculated by use of a standard equation for parallel resistors.9,10 Determination of nasal resistance by use of anterior rhinomanometry results in a value for total resistance, which does not include resistance of the nasopharynx.11
Active anterior rhinomanometry is widely used in humans and relies on cooperation of the patient.9,10,12 The primary uses are to objectively evaluate impairment of the airflow attributable to pathologic changes in the nasal ducts, monitor the success of surgical or conservative treatments,13,14 quantify allergic reactions,15 document reactive mucosal swelling during challenge-exposure tests,16 or assess apnea during sleep.17
Nasal resistance is the sum of at least 3 components (ie, nostril orifice, nasal passages, and nasopharynx).11 Short-headed dogs of the brachycephalic type often have extremely narrow nostrils that dominantly contribute to total resistance. A method to quantify total RNA should measure these 3 components as undistortedly as possible. Inserting a pressure probe into the passive nostril for active anterior rhinomanometry in dogs is not possible without distorting the geometry of the closely adjacent nostril. Another study18 in which investigators used passive anterior rhinomanometry to evaluate allergic rhinitis in dogs by the use of nasal catheters inserted bilaterally into both nostrils ignored this important influence of the nasal entrance.
For all the aforementioned reasons, passive posterior rhinomanometry performed in anesthetized animals appears to be the best method for nasal investigations, even for dogs with brachycephalic syndrome. We assume that this investigation technique can be applied to dogs because this species has often been used in the development19,20 and research for possible applications in humans.12,13,16 Repeatability of this method in humans has been proven.21
The objective of the study reported here was to examine the short- and long-term repeatability of posterior rhinomanometry in dogs. Examinations were performed in Beagles, a breed in which brachycephalic syndrome has not been observed and that belongs to the group of mesaticephalic dogs.22 To determine the level at which pathologic changes are detected, a small group of brachycephalic dogs (ie, Bulldogs), with and without evidence of brachycephalic syndrome, were also examined.
Transnasal pressure difference
Airflow of ventilation
PNA during inspiration
PNA during expiration
RNA during inspiration
RNA during expiration
Partial SD value for repeated measurements obtained on 2 days
Partial SD value for repeated measurements obtained for repeated measurements on the same day
SD for within-day measurements
SD for between-day measurements
RC for within-day measurements
RC for between-day measurements
Coefficient of variation
Spiroson, Eco Medics AG, Duernten, Switzerland.
Model S-500, Hamilton Co, Reno, Nev.
Temgesic, Essex Chemie AG, Luzern, Switzerland.
Prequillan, FATRO S.p.A., Ozzano Emilia, Italy.
Propofol-Lipuro 1%, Braun Medical AG, Emmenbruecke, Switzerland.
Halotano, Rhodia Ltd, Avonmouth, Bristol, UK.
ΔP-04, Equine Clinic, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
Type 163PC01D36, FS, Honeywell, Morristown, NJ.
Exhalizer-D with Spiroware software, Eco Medics AG, Duernten, Switzerland.
Excel 2003, Microsoft Corp, Redmond, Wash.
Orsher RJ. Brachycephalic airway disease. In: Bojrab J, ed. Disease mechanisms in small animal surgery. 2nd ed. Philadelphia: Lea & Febiger, 1993;369–370.
Harvey CE. Upper airway obstruction surgery 1: stenotic nares surgery in brachycephalic dogs. J Am Anim Hosp Assoc 1982;18:535–537.
Aron DN, Crowe DT. Upper airway obstruction. General principles and selected conditions in the dog and cat. Vet Clin North Am Small Anim Pract 1985;15:891–917.
Pallanch JF, McCaffrey TV, Kern EB. Evaluation of nasal breathing function. In: Cummings CW, ed. Otolaryngology—head and neck surgery. 2nd ed. St Louis: Mosby Year Book Inc, 1993;665–686.
Jones AS, Lancer JM, Stevens JC, et al. Rhinomanometry: do the anterior and posterior methods give equivalent results? Clin Otolaryngol Allied Sci 1987;12:109–114.
Hagemann H, Bauer PC, Costabel U. Comparability of various measurement methods in nasal provocation with allergens. Pneumologie 2002;56:363–368.
Cuddihy PJ, Eccles R. The use of nasal spirometry as an objective measure of nasal septal deviation and the effectiveness of septal surgery. Clin Otolaryngol Allied Sci 2003;28:325–330.
Gehring JM, Garlick SR, Wheatly JR, et al. Nasal resistance and flow resistive work of nasal breathing during exercise: effects of a nasal dilator strip. J Appl Physiol 2000;89:1114–1122.
Haavisto L, Sipila J, Suonpaa J. Nonspecific nasal mucosal reactivity, expressed as changes in nasal airway resistance after bilateral saline provocation. Am J Rhinol 1998;12:275–278.
Grutzenmacher S, Mlynski G, Mlynski B, et al. Objectivation of nasal swelling—a comparison of four methods. Laryngorhinootologie 2003;82:645–649.
Virkkula P, Maasilta P, Hytonen M, et al. Nasal obstruction and sleepdisordered breathing: the effect of supine body position on nasal measurements in snorers. Acta Otolaryngol 2003;123:648–654.
Tiniakov RL, Tiniakova OP, McLeod RL, et al. Canine model of nasal congestion and allergic rhinitis. J Appl Physiol 2003;94:1821–1828.
Amis TC, O’Neill N, Van der Touw T, et al. Supraglottic airway pressure-flow relationships during oronasal airflow partitioning in dogs. J Appl Physiol 1996;81:1958–1964.
Silkoff PE, Chakravorty S, Chapnik J, et al. Reproducibility of acoustic rhinometry and rhinomanometry in normal subjects. Am J Rhinol 1999;13:131–135.
Neter J, Kutner M, Nachtsheim C, et al. Study designs: repeated measures. In: Neter J, Kutner M, Nachtsheim C, et al, eds. Applied linear statistical models. 4th ed. New York: McGraw-Hill Book Co, 1996;1164–1194.
Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986;1:307–310.
Bachmann W, Legler U. Studies on the structure and function of the anterior section of the nose by means of luminal impressions. Acta Otolaryngol 1972;73:433–442.
Ghaem A, Martineaud JP. Determination of nasal resistance in healthy subjects using 2 technics of rhinomanometry. Bull Eur Physiopathol Respir 1985;21:11–16.
Ohnishi T, Ogura JH, Nelson JR. Effects of nasal obstruction upon the mechanics of the lung in the dog. Laryngoscope 1972;82:712–736.
Lung MA, Phipps RJ, Wang JC, et al. Control of nasal vasculature and airflow resistance in the dog. J Physiol 1984;349:535–551.
McCaffrey TV, Kern EB. Response of nasal airway resistance to hypercapnia and hypoxia in the dog. Acta Otolaryngol 1979;87:545–553.
Lindemann J, Leiacker R, Rettinger G, et al. The relationship between water vapour saturation of inhaled air and nasal patency. Eur Respir J 2003;21:313–316.
Rozanski EA, Greenfield CL, Alsup JC, et al. Measurement of upper airway resistance in awake untrained dolichocephalic and mesaticephalic dogs. Am J Vet Res 1994;55:1055–1059.
Flanagan P, Eccles R. Spontaneous changes of unilateral nasal airflow in man. A re-examination of the ‘nasal cycle.’ Acta Otolaryngol 1997;117:590–595.
Davies AM, Eccles R. Reciprocal changes in nasal resistance to airflow caused by pressure applied to the axilla. Acta Otolaryngol 1985;99:154–159.