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Transition from Nasal to Mouth Breathing with Increasing Nasal Obstruction Estimated by Airflow Resistance Measurement
Auris· Nasus· Larynx (Tokyo) 4, 83-95, 1977
TRANSITION FROM NASAL TO MOUTH BREATHING WITH INCREASING NASAL OBSTRUCTION ESTIMATED BY AIRFLOW RESISTANCE MEASUREMENT Nobuo USUI, M. D. Department of Otorhinolaryngology, Toho University School of Medicine, Tokyo
There have been numerous attempts to evaluate the relationships between the upper and lower airways. However, there are no available data indicating when the shift from nasal to oral breathing takes place as a subject's nasal obstruction increases. In this experiment twenty-four subjects, each with varying degrees of nasal obstruction, were examined. Their nasal and pulmonary resistances were measured for both nasal and oral breathing. Each airflow resistance was analyzed according to the Rohrer's equation. The examination results of those subjects who fell into the fourth degree classification of nasal obstruction showed transition from nasal to oral breathing. The pressure-flow curves of the nasal passages and the pleural surface during oral breathing had a same pattern. For the fourth degree cases, the nasal resistance was approximately onehalf of the total pulmonary resistance. In these circumstances the results from our study indicated that at the flow rate of 0.5 liter/sec the nose contributes about 53 % of the total pulmonary resistance. Nasal pathology has been known to cause changes in the pulmonary mechanics to a certain extent. The existence of such relationship between the nasal pathology and the pulmonary mechanics suggests that nasal resistance may have more importance than has been so far assumed in influencing the condition of the pulmonary mechanics. In our previous works (USUI et a/., 1972; USUI, 1976) we demonstrated the abnormalities of pulmonary mechanics that were found among the results of several physiological respiratory tests given to subjects with nasal obstruction during both nasal and oral breathing. The abnormalities included a shift from nasal to oral breathing. However, there are no available data indicating when shift from nasal to oral breathing takes place as a subject's nasal obstruction increases. Received for publication January 26, 1977 83
N. USUI
84
The measurements taken from the alterations in the mechanical properties of the lung, from the rhinophysiological point of view, enable us to analyze the characteristics of the organic, as well as the functional, changes in the respiratory system. The results of the studies dealt with here indicate that it is possible to evaluate the airflow resistance separately at different sites in the airway. MATERIALS AND METHODS
Twenty-four unselected subjects (17 males and 7 females) with varying degrees of nasal obstruction were examined. Out of the twenty-four subjects, six were classified as normal nose cases (first and second degree) and eighteen as abnormal nose cases according to OGURA'S (1964) anatomical and physiological classification of nasal obstruction (Table 1). Six of the eighteen abnormal nose cases belonged Table 1. Anatomical and physiological classification of nasal obstruction described by OGURA. Classification Normal nose
Description of the nose 0 1 2
Straight septum, perfectly good airway. Straight septum, slight enlargement of turbinates, no nasal obstruction. Deviated septum, with or without minimal nasal obstruction. *
3
Moderately deviated septum, septal spur, unilateral narrowing of middle meatus, fixed unilateral nasal obstruction. Anterior deviation of nasal septum, unilateral impaction by the septum, and unilateral upper lateral cartilage collapse, with an open airway on the other side. Moderate obstruction. t Same as Classification 4, but with bilateral upper lateral cartilage collapse, and moderate bilateral nasal obstruction. Severe anatomic bilateral septal deviation of the nose, with severe bilateral nasal obstruction from septal and upper lateral cartilage impingement. tt
4
Abnormal nose
5 6
* Minimal nasal obstruction means mild symptomatic unilateral or bilateral, and intermitt
tt
tent. Moderate nasal obstruction: means obstruction is frequent or complete on one side, and incomplete and good airway on other side. Severe nasal obstruction: means nearly constant and bilateral.
to the third degree, another six to the fourth degree, and the last six to the fifth degree classification of nasal obstruction. The subjects belonging to the first and second degrees were analyzed as one group. No cases of extreme nasal obstruction belonging to the sixth degree classification were included in this paper. Physical examination revealed no obvious pathological changes in the lung. The mean ages were 32.8 (range 17 to 62) and 32.6 (range 17 to 52) for men and women respectively. All measurements were taken while the subjects were quietly breathing in a
TRANSITION FROM NASAL TO MOUTH BREATHING
85
sitting position in the laboratory atmosphere. Simultaneous measurements of flow rate and pressure gradient were necessary to determine the resistance to air flow. All pressure differences and simultaneous measurements of flow rate and lung volume were recorded in the same manner described in our previous report (1976). Measurements were first taken during oral breathing, followed by simultaneous measurements of nasal resistance and total pulmonary resistance including the nose. Pleural surface pressure was measured indirectly by using the esophageal balloon method. Pressure at the outside of the facial mask was sensed by the machine with a No. 17 gauge needle inserted into the connecting tube between the facial mask and the pneumotachograph. One cubic centimeter of air was introduced into the balloon by means of polyethylene tube, which was in turn connected to a pressure transducer (Sanborn 268B) in order to obtain the pressure differences between outside and oesophagus. Nasopharyngeal pressure was sampled via a small openended polyethylene tube. The flows of the inspired and expired air were measured with a pneumotachograph (Lilly) coupled to another sensitive electrical transducer (Sanborn 270). The air was gradually heated to 26°C during its passage through the pneumotachograph. All pressure differences were recorded on a Sanborn writeout system (Model 7700) along with simultaneous measurements of flow rate and lung volume, and at the same time they were displayed on a cathode ray oscilloscope (Sanborn 569A). Transnasal pressure, transpulmonary pressure during both nasal and oral breathing, and the rate of gas flow were the principal parameters obtained from this study. The pressure-flow relationships of each two points of the respiratory tract were expressed in the Rohrer's equation (P=kJ' +k2 V2) where P stands for pressure drop between the two points in cmH 20 and V stands for the flow rate in liters per second. The Rohrer's constants, kl and k2' were calculated from about ten cycles of these tracings by using the least square method. For each of them the mean and the standard deviation for kl and k2 were determined. Elastic pressure in the lower airway was removed from the transpulmonary pressure before the calculation. A new polynomial was formed by the means of the constants. By also separating the nasal and oral breathing studies, three curve populations were obtained. The resistances were calculated at the flow rate of 0.5 liters per second. RESULTS
Under a precise, rhinoscopic examination, the subjects were classified cording to the Ogura's anatomical and physiological classification of nasal struction (Table 1). Out of the twenty-four subjects, six were classified into first and second degrees, another six into the third degree, the next six into
acobthe the
6
6
6
6
3
4
5
No. of cases
1&2
Grade of obstruct
k2
1.54 7.09 0.87 2.36
4.32 2.15
0.65 0.61 1.42 6.82 0.58
Mean
±S.D.
Mean
±S.D.
2.64
0.40 2.57
0.46
0.55
±S.D. 1.37
3.62
0.84 0.53
1.37
3.76
0.86
2.04
0.84
2.33
1.16 2.15
2.15
0.69
0.19
Mean
Insp.
k2
2.55
7.22
4.57
6.74
2.25
4.23
0.82
0.78
1.81
3.07
0.66
2.10
0.78
3.60
9.82
4.94
7.81
2.16
2.04 4.43
0.31
k2 2.46
Exp.
1.49
kl
Between nose and pleural surface
1.14 2.43
kl
0.19 0.64
0.57
0.12
1.40
Exp.
0.35
kl
±S.D.
k2
1.15
Insp.
0.31
kl
Between nose and pharynx
0.75
1. 76
0.79
2.04
1.09
1.83
0.70
k2
1.18
2.29
1.12
1.56
1.26
1.43
1.16
1.32
Insp. 1.10
kl
1.88
3.57
1.58
2.60
1.28
0.63
1.01
1.60 3.32
0.68
1.40
1.35
1. 51
0.44
k2 1.83
Exp. 1.01
kl
Between mouth and pleural surface
Mean Rohrer's constants for classification of nasal obstruction through nose and mouth.
Mean
Table 2.
-
;Z c::: til c:::
a-
00
TRANSITION FROM NASAL TO MOUTH BREATHING
87
fourth degree, and the last six into the fifth degree. In all of the subjects the relationship between pressure and flow was curvilinear. The Rohrer's constants and resistance values were calculated separately for both the inspiratory and expiratory phases. Table 2 presents the Rohrer's constants between nose and pharynx, between nose and pleural surface, and between mouth and pleural surface of the twentyfour subjects divided into four groups. The least variation was found in the nasal passages of the normal nose group (first and second degrees) and the greatest in the one between nose and pleural surface of the abnormal nose group (fifth degree). Pressure-flow relations in each group
The data obtained from the dynamic changes of the respiratory system were unified in order to evaluate the pressure-flow relationships at certain flow rates. The pressure difference for flow rates from zero flow to 0.5 liters per second flow was calculated for all subjects during resting ventilation. The mean curves for each group were then transposed to a common scale. Flow was shown on the ordinate and pressure on the abscissa in such a way that the curve for inspiration occupied the upper righthand quadrant and the one for expiration, the lower lefthand quadrant. Pressure-flow relations in the first two degrees
Figure 1 shows the pressure-flow curves of the six normal subjects obtained in this investigation. It is apparent that the three curves have similar shapes. The distribution of pressure depends on the flow rate: there is an increased contribution from the upper airways as flow increased.
v
(LPS)
4
Insp.
2
~--------~-------4--------,-------~--P(cmH20)
Exp.
"
2
4
h
1/
// // , I
I
I
/,/
- - Nose - - - Nose-PI. ----- Mouth-PI.
Fig. 1. Pressure-flow relations in Grade 1 and 2.
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88
As might be expected, pressure-flow curve was more curvilinear during nasal breathing than during oral breathing between the upper airway and the pleural surface. Also, pressure-flow curve was less steeper between mouth and pleural surface than in the nasal passages. At the same flow rate the pressure differences fall within a narrow range for all three pressure-flow curves. In these cases normal pressure-flow curves appear to indicate that there is no disturbance in the breathing mechanics; therefore, the respiratory function is assumed to be normal. Pressure-flow relations in the third degree
In these cases, increased resistance to air flow rotated each pressure-flow curve clockwise, but it was a consistent increase (Fig. 2). It is evident from the figure that the shapes of the pressure-flow curves were inclined approximately twofold those of the normal state.
v
(LPS)
0.4
4
/1
'
'
II
2
,
// / I
I
/ /'" ,/ /"
" I
Insp.
----L----...L..----J~---_,_---___,r_p
2
Exp.
4
(cmH20)
- - Nose
0.4
Fig. 2.
- - - Nose-PI. ----- Mouth-PI.
Pressure-flow relations in Grade 3.
Pressure-flow relations in the fourth degree
Obvious changes were noted in this group during both nasal and oral breathing (Fig. 3). In addition to the different nasal pressure-flow curve, concurrent changes in the pressure-flow curve below the nose were observed. The nasal pressure-flow curve was approximately one-half the total pulmonary pressure-flow curve during nasal breathing. However, a comparison of the pressure-flow curves between the nasal passages and the pleural surface during oral breathing showed little difference in their values. Pressure-flow relations in the fifth degree
A tendency toward higher value in pressure difference between nose and
TRANSITION FROM NASAL TO MOUTH BREATHING
89
v
(LPS)
0.4
4
2
~---------L--------4---------r--------.-P(cmH20) 4 2 Exp.
- - Nose - - - Nose-PI.
0.4
----- Mouth-PI.
Fig. 3. Pressure-flow relations in Grade 4.
pleural surface during nasal breathing was noted in Fig. 4. Nasal pressure-flow curve was more curvilinear than pressure-flow curve between mouth and pleural surface during oral breathing. Here the former two curves' order of placement switches.
v
(LPS)
0.4
0.2 4
2
~---------L--------T---------r--------.-P(cmH20)
2
Exp.
0.2 0.4
4
--Nose - - - Nose-PI. ----- Mouth-PI.
Fig. 4. Pressure-flow relations in Grade 5.
In the four groups, an increased nasal obstruction rotated each pressure-flow curve clockwise. Changes in flow resistance for each degree of nasal obstruction The simultaneous changes in nasal and total pulmonary resistance were
6
6
6
6
3
4
5
No. of cases
1&2
Grade of obstruct.
0.90 2.01
4.96 1.16
0.34 2.24 0.76 3.18 1.23 5.08 1.80
0.23 1. 77 0.48 2.81 0.81 4.84 0.94
±S.D.
Mean
±S.D.
Mean
±S.D.
Mean
±S.D.
1.67
0.90
1.28
7.37
5.41
1.35
4.44
0.86
2.35
Insp.
3.0
0.52
0.97
1.05
0.89
Mean
Avg.
Exp.
Insp.
1.82
7.98
2.38
6.01
0.98
4.26
0.31
2.72
Exp.
1.40
7.68
1.80
5.71
0.95
4.35
1.41
2.54
Avg.
Between nose and pleural surface
0.85
2.91
0.86
2.82
1.72
2.55
1.23
1. 76
Insp.
0.65
3.26
0.93
3.19
1.88
2.81
1.03
1.92
Exp.
0.59
3.09
0.94
3.01
1.64
2.68
1.02
1.84
Avg.
Between mouth and pleural surface
Airflow resistance for classification of nasal obstruction through nose and mouth at a flow rate of 0.5 liter/sec.
Between nose and pharynx
Table 3.
0.31
0.80
0.13
0.85
0.33
0.91
0.32
1.0
Vt.
(L)
5.87
16.2
3.59
18.4
5.97
16.7
4.33
14.0
F. (c/m)
~ C I:Il C .....
)g
91
TRANSITION FROM NASAL TO MOUTH BREATHING
studied. During nasal breathing, the total pulmonary resistance in the alveoli is the sum of the resistances in the nasal passages and the lower airway. Therefore, in addition to the variation in nasal resistance, concurrent changes in the resistance between the nose and the pleural surface were observed. Means and standard deviations were calculated. A comparison of the nasal resistances at the flow rate of 0.5 liters per second along with the calculated values between the nose and the pleural surface and between the mouth and the pleural surface at this same flow rate are shown in Table 3. Nasal resistance and total pulmonary resistance during nasal breathing were greater during expiration than during inspiration in almost all of these groups. We computed the ratio of nasal resistance to the total pulmonary resistance at a flow rate of 0.5 liters per second during both nasal and oral breathing; inspiratory and expiratory values were averaged in each degree (Table 4). Table 4. Average resistance and ratio for various parts of the respiratory tract at a flow of 0.5 liter/sec in each Grade of nasal obstruction. Grade of obstruct I.
1&2
3
4
5
2.01 0.46 0.75
3.0 0.53 1.0
4.96 0.64 1.61
4.35 2.16 1.62
5.71 1.90 1.90
7.68 1.55 2.49
2.68 1.33 0.62
3.01 1.0 0.53
3.09 0.62 0.40
Between nose and pharynx: Avg. resistance Ratio (1/11) Ratio (l/lIJ)
0.97 0.38 0.53
II. Between nose and pleural surface: Avg. resistance Ratio (II/I) Ra ti 0 (II/III)
2.54 2.62 1.38
III. Between mouth and pleural surface: A vg. resistance Ratio (III/I) Ratio (III/II)
1.84 1.90 0.72
The ratio of the average resistance found between nose and pharynx to the resistance found between nose and pleural surface (1/11) was 0.38 for the first two degrees, 0.46 for the third degree, 0.53 for the fourth degree, and 0.64 for the fifth degree. Therefore, the relative contribution of the nasal passages and lower airway to these changes were 38 % for the first two degrees, 46 % for the third degree, 53 % for fourth degree, and 64 % for the fifth degree. On the contrary, the ratio of the average resistance found between nose and pharynx to the resistance found between mouth and pleural surface (1/111) was 0.53 for the first two degrees, 0.75 for the third degree, 1.0 for the fourth degree, and 1.61 for the fifth degree. Therefore, the nasal resistance was 0.5-fold in the normal group, 0.75-fold in the third degree, 1.0-fold in the fourth degree, and
92
N. USUI
approximately 1.5-fold in the fifth degree the resistance found between mouth and pleural surface. DISCUSSION
Physiologically, the restricted air flow in the upper airway obstruction shows a curved pressure-flow relationship similar to that of the air flow through an orifice. However, with an increasing rate of air flow the pressure gradient increases disproportionately to the rate of air flow, and resistance increases with the flow rate. This is because air flow is partly laminar and partly turbulent. Some investigators (FERRIS et al., 1964; CRAIG et al., 1965) express resistance in terms of the two coefficients, kl and k2' in the equation, P=kJ' +k2J?2, where the first and the second terms represent the laminar and the turbulent flow, respectively. We analyzed the pressure-flow relationships for each degree of nasal obstruction during both nasal and oral breathing. The studies on pressure-flow relations of human nose carried out by BUTLER (1960), FERRIS et al. (1964), SPEIZER et al. (1964), and CRAIG et al. (1965) show a distinct picture of nonlinearity. As is true for the nose, the pressure-flow relations between nose and pleural surface and between mouth and pleural surface are markedly nonlinear. The most outstanding change in flow resistance during quiet respiration was observed in the nasal passages, and so the pulmonary resistance during nasal breathing was varied concurrently. In addition, the pulmonary resistance during oral breathing was also increased among subjects with nasal obstruction, but it has a slightly increasing tendency. Our interpretation of this phenomenon would seem to indicate that probably a reflex and possibly some mechanical factors are involved (OGURA et al., 1964, 1966, 1968a; TOGAWA and OGURA, 1966; UNNO et a!., 1968). A long term study of nasal obstruction in relation to pulmonary function convinces us that subjects who fall into the anatomical classification of the fourth degree are usually "transition from nasal to mouth breathing" cases (OGURA et al., 1968b). Although the nasal pressure-flow curve had approximately the same value as the pulmonary pressure-flow curve during oral breathing in the fourth degree classification, the pulmonary pressure-flow curve during nasal breathing was much higher degree of clockwise rotation. Greater pressure gradient is necessary to inhale the air into the lungs in order to overcome the higher resistance in the nose, and thus more energy is required for breathing by this group than by the normal subjects. Such pressure required to move air into the lungs during nasal breathing for the fourth degree cases is approximately 3 cmH 2 0 (P=2.04V +6.74 V2) at a
TRANSITION FROM NASAL TO MOUTH BREATHING
93
flow rate of 0.5 liters per second. Therefore, air flow resistance of approximately 6.0 cmH 20/liter/sec causes a considerable amount subjective complaints. We consider that symptomatic difficulties observed among the patients with nasal obstruction are explained by the latent disturbance of the pulmonary function. Nasal obstruction is compensated by utilization of oral breathing. The observed value of the resistance in the lungs during oral breathing in the fourth degree thus was approximately 3.0 cmH 20/liter/sec at a flow rate of 0.5 liters per second. Therefore, the airflow resistance found between mouth and pleural surface was approximately one-half the airflow resistance found between nose and pleural surface. At a flow of 0.5 liters per second, the nasal resistance was 0.5-fold in the normal group, 0.75-fold in the third degree, l.O-fold in the fourth degree, and approximately 1.5-fold in the fifth degree the resistance found between mouth and pleural surface. The subjects in this category who display such adverse changes in the pressureflow relationships between nasal passages and pleural surface during oral breathing are considered to be definite candidates for nasal surgery. Fixed nasal obstruction causes a marked increase in nasal resistance, and such an increased nasal resistance is the greatest single component affecting the total pulmonary resistance. ROHRER (1915), after studying the various aspects of aerodynamics and flow resistance, assessed that the nose accounts for 47 % of the total airway resistance during quiet breathing. According to the results of a study by CRAIG et al. (1965), the measurements of the pressure-flow relationships in the lower airway indicated that during nasal breathing, the nose accounts for 40 % of the total airway resistance. The results of our study indicated that at 0.5 liters per second, the nose of the normal nose group contributes about 38 % of the total pulmonary resistance. The pronounced alinearity of nasal resistance reflected conspicuously its percentage contribution to the total pulmonary resistance. During nasal breathing of the subjects who belonged to the fourth degree classification, the mean nasal resistance was 53 % of the total pulmonary resistance. At rest, a human being normally breathes through the nose and not the mouth. In these circumstances an increase in nasal resistance may be compensated by reserve respiratory ability while at rest, but an increased consumption of energy may produce tendencies toward shortness of breath or fatigue. Pathological and anatomical changes in the upper airway may not produce changes great enough to cause pulmonary symptomatology because of the reserve ability of the lung. However, it is important to examine these changes in order to determine how a compensatory effort in respiration is operating, and in doing so, to examine the efficiency of the breathing mechanics.
94
N. USUI SUMMARY
Examinations were made on twenty-four unselected subjects with varying degrees of nasal obstruction. Out of the twenty-four subjects, six were classified as belonging to the first two degrees, another six as belonging to the third degree, the next six as belonging to the fourth degree, and the last six as belonging to the fifth degree. Measurements were first taken during oral breathing, followed by simultaneous measurements of the nasal and total pulmonary resistances during nasal breathing. Three curve populations were obtained for each group. An increase in nasal obstruction rotated each pressure-flow curve clockwise; however, the pulmonary resistance curve during oral breathing rotated much slowly and less markedly. The results of the studies of the subjects who fell into the fourth degree classification of nasal obstruction were "transition to mouth breathing" cases. For the fourth degree cases, the pressure-flow curves of airflow through the nasal passages and those between the pleural surface and atmosphere during oral breathing had the same pattern. The total pulmonary pressure-flow curve during nasal breathing was inclined approximately twofold in the nasal pressure-flow curve. The nasal contribution at a flow rate of 0.5 liters per second was 53 % of the total pulmonary resistance in the fourth degree classification. The method presented here is well-suited for evaluating the resistance to airflow between nose and pleural surface of patients with anatomical, as well as functional, nasal obstruction. This study was made while the author was a research fellow of Washington University School of Medicine. The author gratefully acknowledges the invaluable suggestions and criticisms of Dr. J. R. Ogura, the professor of the Department of Otolaryngology, Washington University School of Medicine. REFERENCES BUTLER, J.: Work of breathing through the nose. Clin. Sci. 19: 55-62, 1960. CRAIG, A. B., Jr., DVORAK, M., and MclLREATH, F. J.: Resistance to airflow through the nose. Ann. Otol., Rhinol. and Laryngol. 47: 589-603, 1965. FERRIS, B. G., MEAD, J., and OPIE, L. R.: Partitioning of respiratory flow resistance in man. J. Appl. Physiol. 19: 653-658, 1964. OGURA, J. R., NELSON, J. R., DAMMKOEHLER, R., KAWASAKI, M., and TOGAWA, K.: Experimental observations on the relationships between upper airway obstructions and pulmonary function. Ann. Otolaryngol. 73: 381-403, 1964. OGURA, J. R., TOGAWA, K., DAMMKOEHLER, R., NELSON, J. R., and KAWASAKI, M.: Nasal obstruction and the mechanics of breathing. Arch. Otolaryngol. 83: 135-150, 1966. OGURA, J. R., UNNO, T., and NELSON, J. R.: Nasal surgery. Physiological considerations of nasal obstruction. Arch. Otolaryngol. 88: 288-295, 1968a. OGURA, J. R., UNNO, T., and NELSON, J. R.: Baseline values in pulmonary mechanics for physiologic surgery of the nose. Preliminary report. Ann. Otol., Rhinol. and Laryngol. 77: 367-397, 1968b.
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ROHRER, F.: Der Stromungswiderstand in den Menshlichen Atemwegen und der Einfluss der unregelmassigen Verzweigung des Bronchialsystems auf den Atmungsverlauf in verscheidenen Lungenbezirken. Arch. ges. Physiol. 162: 225-299, 1915. SPEIZER, F. E. and FRANK, N. R.: A technique for measuring nasal and pulmonary flow resistance simultaneously. J. Appl. Physiol. 19: 176-178,1964. TOGAW A, K. and OGURA, J. H. : Physiologic relationships between nasal breathing and pulmonary function. The Laryngoscope 76: 30-63, 1966. UNNO, T., NELSON, J. R., and OGURA, J. H.: The effects of nasal obstruction on pulmonary, airway and tissue resistance. The Laryngoscope 78: 1119-1139, 1968. USUl, N., NAGOSHI, Y., HAYAKAWA, K., ISHIZUKA, Y., SUEMITSU, M., and KONNO, A.: The influence of nasal obstruction on pulmonary mechanics. J. Med. Soc. Toho 19: 695-701, 1972. USUl, N.: Effect of neo-synephrine nasal spray on pulmonary resistance in man. Auris· Nasus·Larynx (Tokyo) 3: 53-63, 1976.
Request reprints from: Dr. Nobuo Usui, Department of Otorhinolaryngology, Toho University School of Medicine, 6-11-1, Ohmori-nishi, Ohta-ku, Tokyo 143, Japan
TRANSITION FROM NASAL TO MOUTH BREATHING WITH INCREASING NASAL OBSTRUCTION ESTIMATED BY AIRFLOW RESISTANCE MEASUREMENT Nobuo USUI, M. D. Department of Otorhinolaryngology, Toho University School of Medicine, Tokyo
There have been numerous attempts to evaluate the relationships between the upper and lower airways. However, there are no available data indicating when the shift from nasal to oral breathing takes place as a subject's nasal obstruction increases. In this experiment twenty-four subjects, each with varying degrees of nasal obstruction, were examined. Their nasal and pulmonary resistances were measured for both nasal and oral breathing. Each airflow resistance was analyzed according to the Rohrer's equation. The examination results of those subjects who fell into the fourth degree classification of nasal obstruction showed transition from nasal to oral breathing. The pressure-flow curves of the nasal passages and the pleural surface during oral breathing had a same pattern. For the fourth degree cases, the nasal resistance was approximately onehalf of the total pulmonary resistance. In these circumstances the results from our study indicated that at the flow rate of 0.5 liter/sec the nose contributes about 53 % of the total pulmonary resistance. Nasal pathology has been known to cause changes in the pulmonary mechanics to a certain extent. The existence of such relationship between the nasal pathology and the pulmonary mechanics suggests that nasal resistance may have more importance than has been so far assumed in influencing the condition of the pulmonary mechanics. In our previous works (USUI et a/., 1972; USUI, 1976) we demonstrated the abnormalities of pulmonary mechanics that were found among the results of several physiological respiratory tests given to subjects with nasal obstruction during both nasal and oral breathing. The abnormalities included a shift from nasal to oral breathing. However, there are no available data indicating when shift from nasal to oral breathing takes place as a subject's nasal obstruction increases. Received for publication January 26, 1977 83
N. USUI
84
The measurements taken from the alterations in the mechanical properties of the lung, from the rhinophysiological point of view, enable us to analyze the characteristics of the organic, as well as the functional, changes in the respiratory system. The results of the studies dealt with here indicate that it is possible to evaluate the airflow resistance separately at different sites in the airway. MATERIALS AND METHODS
Twenty-four unselected subjects (17 males and 7 females) with varying degrees of nasal obstruction were examined. Out of the twenty-four subjects, six were classified as normal nose cases (first and second degree) and eighteen as abnormal nose cases according to OGURA'S (1964) anatomical and physiological classification of nasal obstruction (Table 1). Six of the eighteen abnormal nose cases belonged Table 1. Anatomical and physiological classification of nasal obstruction described by OGURA. Classification Normal nose
Description of the nose 0 1 2
Straight septum, perfectly good airway. Straight septum, slight enlargement of turbinates, no nasal obstruction. Deviated septum, with or without minimal nasal obstruction. *
3
Moderately deviated septum, septal spur, unilateral narrowing of middle meatus, fixed unilateral nasal obstruction. Anterior deviation of nasal septum, unilateral impaction by the septum, and unilateral upper lateral cartilage collapse, with an open airway on the other side. Moderate obstruction. t Same as Classification 4, but with bilateral upper lateral cartilage collapse, and moderate bilateral nasal obstruction. Severe anatomic bilateral septal deviation of the nose, with severe bilateral nasal obstruction from septal and upper lateral cartilage impingement. tt
4
Abnormal nose
5 6
* Minimal nasal obstruction means mild symptomatic unilateral or bilateral, and intermitt
tt
tent. Moderate nasal obstruction: means obstruction is frequent or complete on one side, and incomplete and good airway on other side. Severe nasal obstruction: means nearly constant and bilateral.
to the third degree, another six to the fourth degree, and the last six to the fifth degree classification of nasal obstruction. The subjects belonging to the first and second degrees were analyzed as one group. No cases of extreme nasal obstruction belonging to the sixth degree classification were included in this paper. Physical examination revealed no obvious pathological changes in the lung. The mean ages were 32.8 (range 17 to 62) and 32.6 (range 17 to 52) for men and women respectively. All measurements were taken while the subjects were quietly breathing in a
TRANSITION FROM NASAL TO MOUTH BREATHING
85
sitting position in the laboratory atmosphere. Simultaneous measurements of flow rate and pressure gradient were necessary to determine the resistance to air flow. All pressure differences and simultaneous measurements of flow rate and lung volume were recorded in the same manner described in our previous report (1976). Measurements were first taken during oral breathing, followed by simultaneous measurements of nasal resistance and total pulmonary resistance including the nose. Pleural surface pressure was measured indirectly by using the esophageal balloon method. Pressure at the outside of the facial mask was sensed by the machine with a No. 17 gauge needle inserted into the connecting tube between the facial mask and the pneumotachograph. One cubic centimeter of air was introduced into the balloon by means of polyethylene tube, which was in turn connected to a pressure transducer (Sanborn 268B) in order to obtain the pressure differences between outside and oesophagus. Nasopharyngeal pressure was sampled via a small openended polyethylene tube. The flows of the inspired and expired air were measured with a pneumotachograph (Lilly) coupled to another sensitive electrical transducer (Sanborn 270). The air was gradually heated to 26°C during its passage through the pneumotachograph. All pressure differences were recorded on a Sanborn writeout system (Model 7700) along with simultaneous measurements of flow rate and lung volume, and at the same time they were displayed on a cathode ray oscilloscope (Sanborn 569A). Transnasal pressure, transpulmonary pressure during both nasal and oral breathing, and the rate of gas flow were the principal parameters obtained from this study. The pressure-flow relationships of each two points of the respiratory tract were expressed in the Rohrer's equation (P=kJ' +k2 V2) where P stands for pressure drop between the two points in cmH 20 and V stands for the flow rate in liters per second. The Rohrer's constants, kl and k2' were calculated from about ten cycles of these tracings by using the least square method. For each of them the mean and the standard deviation for kl and k2 were determined. Elastic pressure in the lower airway was removed from the transpulmonary pressure before the calculation. A new polynomial was formed by the means of the constants. By also separating the nasal and oral breathing studies, three curve populations were obtained. The resistances were calculated at the flow rate of 0.5 liters per second. RESULTS
Under a precise, rhinoscopic examination, the subjects were classified cording to the Ogura's anatomical and physiological classification of nasal struction (Table 1). Out of the twenty-four subjects, six were classified into first and second degrees, another six into the third degree, the next six into
acobthe the
6
6
6
6
3
4
5
No. of cases
1&2
Grade of obstruct
k2
1.54 7.09 0.87 2.36
4.32 2.15
0.65 0.61 1.42 6.82 0.58
Mean
±S.D.
Mean
±S.D.
2.64
0.40 2.57
0.46
0.55
±S.D. 1.37
3.62
0.84 0.53
1.37
3.76
0.86
2.04
0.84
2.33
1.16 2.15
2.15
0.69
0.19
Mean
Insp.
k2
2.55
7.22
4.57
6.74
2.25
4.23
0.82
0.78
1.81
3.07
0.66
2.10
0.78
3.60
9.82
4.94
7.81
2.16
2.04 4.43
0.31
k2 2.46
Exp.
1.49
kl
Between nose and pleural surface
1.14 2.43
kl
0.19 0.64
0.57
0.12
1.40
Exp.
0.35
kl
±S.D.
k2
1.15
Insp.
0.31
kl
Between nose and pharynx
0.75
1. 76
0.79
2.04
1.09
1.83
0.70
k2
1.18
2.29
1.12
1.56
1.26
1.43
1.16
1.32
Insp. 1.10
kl
1.88
3.57
1.58
2.60
1.28
0.63
1.01
1.60 3.32
0.68
1.40
1.35
1. 51
0.44
k2 1.83
Exp. 1.01
kl
Between mouth and pleural surface
Mean Rohrer's constants for classification of nasal obstruction through nose and mouth.
Mean
Table 2.
-
;Z c::: til c:::
a-
00
TRANSITION FROM NASAL TO MOUTH BREATHING
87
fourth degree, and the last six into the fifth degree. In all of the subjects the relationship between pressure and flow was curvilinear. The Rohrer's constants and resistance values were calculated separately for both the inspiratory and expiratory phases. Table 2 presents the Rohrer's constants between nose and pharynx, between nose and pleural surface, and between mouth and pleural surface of the twentyfour subjects divided into four groups. The least variation was found in the nasal passages of the normal nose group (first and second degrees) and the greatest in the one between nose and pleural surface of the abnormal nose group (fifth degree). Pressure-flow relations in each group
The data obtained from the dynamic changes of the respiratory system were unified in order to evaluate the pressure-flow relationships at certain flow rates. The pressure difference for flow rates from zero flow to 0.5 liters per second flow was calculated for all subjects during resting ventilation. The mean curves for each group were then transposed to a common scale. Flow was shown on the ordinate and pressure on the abscissa in such a way that the curve for inspiration occupied the upper righthand quadrant and the one for expiration, the lower lefthand quadrant. Pressure-flow relations in the first two degrees
Figure 1 shows the pressure-flow curves of the six normal subjects obtained in this investigation. It is apparent that the three curves have similar shapes. The distribution of pressure depends on the flow rate: there is an increased contribution from the upper airways as flow increased.
v
(LPS)
4
Insp.
2
~--------~-------4--------,-------~--P(cmH20)
Exp.
"
2
4
h
1/
// // , I
I
I
/,/
- - Nose - - - Nose-PI. ----- Mouth-PI.
Fig. 1. Pressure-flow relations in Grade 1 and 2.
N. USUI
88
As might be expected, pressure-flow curve was more curvilinear during nasal breathing than during oral breathing between the upper airway and the pleural surface. Also, pressure-flow curve was less steeper between mouth and pleural surface than in the nasal passages. At the same flow rate the pressure differences fall within a narrow range for all three pressure-flow curves. In these cases normal pressure-flow curves appear to indicate that there is no disturbance in the breathing mechanics; therefore, the respiratory function is assumed to be normal. Pressure-flow relations in the third degree
In these cases, increased resistance to air flow rotated each pressure-flow curve clockwise, but it was a consistent increase (Fig. 2). It is evident from the figure that the shapes of the pressure-flow curves were inclined approximately twofold those of the normal state.
v
(LPS)
0.4
4
/1
'
'
II
2
,
// / I
I
/ /'" ,/ /"
" I
Insp.
----L----...L..----J~---_,_---___,r_p
2
Exp.
4
(cmH20)
- - Nose
0.4
Fig. 2.
- - - Nose-PI. ----- Mouth-PI.
Pressure-flow relations in Grade 3.
Pressure-flow relations in the fourth degree
Obvious changes were noted in this group during both nasal and oral breathing (Fig. 3). In addition to the different nasal pressure-flow curve, concurrent changes in the pressure-flow curve below the nose were observed. The nasal pressure-flow curve was approximately one-half the total pulmonary pressure-flow curve during nasal breathing. However, a comparison of the pressure-flow curves between the nasal passages and the pleural surface during oral breathing showed little difference in their values. Pressure-flow relations in the fifth degree
A tendency toward higher value in pressure difference between nose and
TRANSITION FROM NASAL TO MOUTH BREATHING
89
v
(LPS)
0.4
4
2
~---------L--------4---------r--------.-P(cmH20) 4 2 Exp.
- - Nose - - - Nose-PI.
0.4
----- Mouth-PI.
Fig. 3. Pressure-flow relations in Grade 4.
pleural surface during nasal breathing was noted in Fig. 4. Nasal pressure-flow curve was more curvilinear than pressure-flow curve between mouth and pleural surface during oral breathing. Here the former two curves' order of placement switches.
v
(LPS)
0.4
0.2 4
2
~---------L--------T---------r--------.-P(cmH20)
2
Exp.
0.2 0.4
4
--Nose - - - Nose-PI. ----- Mouth-PI.
Fig. 4. Pressure-flow relations in Grade 5.
In the four groups, an increased nasal obstruction rotated each pressure-flow curve clockwise. Changes in flow resistance for each degree of nasal obstruction The simultaneous changes in nasal and total pulmonary resistance were
6
6
6
6
3
4
5
No. of cases
1&2
Grade of obstruct.
0.90 2.01
4.96 1.16
0.34 2.24 0.76 3.18 1.23 5.08 1.80
0.23 1. 77 0.48 2.81 0.81 4.84 0.94
±S.D.
Mean
±S.D.
Mean
±S.D.
Mean
±S.D.
1.67
0.90
1.28
7.37
5.41
1.35
4.44
0.86
2.35
Insp.
3.0
0.52
0.97
1.05
0.89
Mean
Avg.
Exp.
Insp.
1.82
7.98
2.38
6.01
0.98
4.26
0.31
2.72
Exp.
1.40
7.68
1.80
5.71
0.95
4.35
1.41
2.54
Avg.
Between nose and pleural surface
0.85
2.91
0.86
2.82
1.72
2.55
1.23
1. 76
Insp.
0.65
3.26
0.93
3.19
1.88
2.81
1.03
1.92
Exp.
0.59
3.09
0.94
3.01
1.64
2.68
1.02
1.84
Avg.
Between mouth and pleural surface
Airflow resistance for classification of nasal obstruction through nose and mouth at a flow rate of 0.5 liter/sec.
Between nose and pharynx
Table 3.
0.31
0.80
0.13
0.85
0.33
0.91
0.32
1.0
Vt.
(L)
5.87
16.2
3.59
18.4
5.97
16.7
4.33
14.0
F. (c/m)
~ C I:Il C .....
)g
91
TRANSITION FROM NASAL TO MOUTH BREATHING
studied. During nasal breathing, the total pulmonary resistance in the alveoli is the sum of the resistances in the nasal passages and the lower airway. Therefore, in addition to the variation in nasal resistance, concurrent changes in the resistance between the nose and the pleural surface were observed. Means and standard deviations were calculated. A comparison of the nasal resistances at the flow rate of 0.5 liters per second along with the calculated values between the nose and the pleural surface and between the mouth and the pleural surface at this same flow rate are shown in Table 3. Nasal resistance and total pulmonary resistance during nasal breathing were greater during expiration than during inspiration in almost all of these groups. We computed the ratio of nasal resistance to the total pulmonary resistance at a flow rate of 0.5 liters per second during both nasal and oral breathing; inspiratory and expiratory values were averaged in each degree (Table 4). Table 4. Average resistance and ratio for various parts of the respiratory tract at a flow of 0.5 liter/sec in each Grade of nasal obstruction. Grade of obstruct I.
1&2
3
4
5
2.01 0.46 0.75
3.0 0.53 1.0
4.96 0.64 1.61
4.35 2.16 1.62
5.71 1.90 1.90
7.68 1.55 2.49
2.68 1.33 0.62
3.01 1.0 0.53
3.09 0.62 0.40
Between nose and pharynx: Avg. resistance Ratio (1/11) Ratio (l/lIJ)
0.97 0.38 0.53
II. Between nose and pleural surface: Avg. resistance Ratio (II/I) Ra ti 0 (II/III)
2.54 2.62 1.38
III. Between mouth and pleural surface: A vg. resistance Ratio (III/I) Ratio (III/II)
1.84 1.90 0.72
The ratio of the average resistance found between nose and pharynx to the resistance found between nose and pleural surface (1/11) was 0.38 for the first two degrees, 0.46 for the third degree, 0.53 for the fourth degree, and 0.64 for the fifth degree. Therefore, the relative contribution of the nasal passages and lower airway to these changes were 38 % for the first two degrees, 46 % for the third degree, 53 % for fourth degree, and 64 % for the fifth degree. On the contrary, the ratio of the average resistance found between nose and pharynx to the resistance found between mouth and pleural surface (1/111) was 0.53 for the first two degrees, 0.75 for the third degree, 1.0 for the fourth degree, and 1.61 for the fifth degree. Therefore, the nasal resistance was 0.5-fold in the normal group, 0.75-fold in the third degree, 1.0-fold in the fourth degree, and
92
N. USUI
approximately 1.5-fold in the fifth degree the resistance found between mouth and pleural surface. DISCUSSION
Physiologically, the restricted air flow in the upper airway obstruction shows a curved pressure-flow relationship similar to that of the air flow through an orifice. However, with an increasing rate of air flow the pressure gradient increases disproportionately to the rate of air flow, and resistance increases with the flow rate. This is because air flow is partly laminar and partly turbulent. Some investigators (FERRIS et al., 1964; CRAIG et al., 1965) express resistance in terms of the two coefficients, kl and k2' in the equation, P=kJ' +k2J?2, where the first and the second terms represent the laminar and the turbulent flow, respectively. We analyzed the pressure-flow relationships for each degree of nasal obstruction during both nasal and oral breathing. The studies on pressure-flow relations of human nose carried out by BUTLER (1960), FERRIS et al. (1964), SPEIZER et al. (1964), and CRAIG et al. (1965) show a distinct picture of nonlinearity. As is true for the nose, the pressure-flow relations between nose and pleural surface and between mouth and pleural surface are markedly nonlinear. The most outstanding change in flow resistance during quiet respiration was observed in the nasal passages, and so the pulmonary resistance during nasal breathing was varied concurrently. In addition, the pulmonary resistance during oral breathing was also increased among subjects with nasal obstruction, but it has a slightly increasing tendency. Our interpretation of this phenomenon would seem to indicate that probably a reflex and possibly some mechanical factors are involved (OGURA et al., 1964, 1966, 1968a; TOGAWA and OGURA, 1966; UNNO et a!., 1968). A long term study of nasal obstruction in relation to pulmonary function convinces us that subjects who fall into the anatomical classification of the fourth degree are usually "transition from nasal to mouth breathing" cases (OGURA et al., 1968b). Although the nasal pressure-flow curve had approximately the same value as the pulmonary pressure-flow curve during oral breathing in the fourth degree classification, the pulmonary pressure-flow curve during nasal breathing was much higher degree of clockwise rotation. Greater pressure gradient is necessary to inhale the air into the lungs in order to overcome the higher resistance in the nose, and thus more energy is required for breathing by this group than by the normal subjects. Such pressure required to move air into the lungs during nasal breathing for the fourth degree cases is approximately 3 cmH 2 0 (P=2.04V +6.74 V2) at a
TRANSITION FROM NASAL TO MOUTH BREATHING
93
flow rate of 0.5 liters per second. Therefore, air flow resistance of approximately 6.0 cmH 20/liter/sec causes a considerable amount subjective complaints. We consider that symptomatic difficulties observed among the patients with nasal obstruction are explained by the latent disturbance of the pulmonary function. Nasal obstruction is compensated by utilization of oral breathing. The observed value of the resistance in the lungs during oral breathing in the fourth degree thus was approximately 3.0 cmH 20/liter/sec at a flow rate of 0.5 liters per second. Therefore, the airflow resistance found between mouth and pleural surface was approximately one-half the airflow resistance found between nose and pleural surface. At a flow of 0.5 liters per second, the nasal resistance was 0.5-fold in the normal group, 0.75-fold in the third degree, l.O-fold in the fourth degree, and approximately 1.5-fold in the fifth degree the resistance found between mouth and pleural surface. The subjects in this category who display such adverse changes in the pressureflow relationships between nasal passages and pleural surface during oral breathing are considered to be definite candidates for nasal surgery. Fixed nasal obstruction causes a marked increase in nasal resistance, and such an increased nasal resistance is the greatest single component affecting the total pulmonary resistance. ROHRER (1915), after studying the various aspects of aerodynamics and flow resistance, assessed that the nose accounts for 47 % of the total airway resistance during quiet breathing. According to the results of a study by CRAIG et al. (1965), the measurements of the pressure-flow relationships in the lower airway indicated that during nasal breathing, the nose accounts for 40 % of the total airway resistance. The results of our study indicated that at 0.5 liters per second, the nose of the normal nose group contributes about 38 % of the total pulmonary resistance. The pronounced alinearity of nasal resistance reflected conspicuously its percentage contribution to the total pulmonary resistance. During nasal breathing of the subjects who belonged to the fourth degree classification, the mean nasal resistance was 53 % of the total pulmonary resistance. At rest, a human being normally breathes through the nose and not the mouth. In these circumstances an increase in nasal resistance may be compensated by reserve respiratory ability while at rest, but an increased consumption of energy may produce tendencies toward shortness of breath or fatigue. Pathological and anatomical changes in the upper airway may not produce changes great enough to cause pulmonary symptomatology because of the reserve ability of the lung. However, it is important to examine these changes in order to determine how a compensatory effort in respiration is operating, and in doing so, to examine the efficiency of the breathing mechanics.
94
N. USUI SUMMARY
Examinations were made on twenty-four unselected subjects with varying degrees of nasal obstruction. Out of the twenty-four subjects, six were classified as belonging to the first two degrees, another six as belonging to the third degree, the next six as belonging to the fourth degree, and the last six as belonging to the fifth degree. Measurements were first taken during oral breathing, followed by simultaneous measurements of the nasal and total pulmonary resistances during nasal breathing. Three curve populations were obtained for each group. An increase in nasal obstruction rotated each pressure-flow curve clockwise; however, the pulmonary resistance curve during oral breathing rotated much slowly and less markedly. The results of the studies of the subjects who fell into the fourth degree classification of nasal obstruction were "transition to mouth breathing" cases. For the fourth degree cases, the pressure-flow curves of airflow through the nasal passages and those between the pleural surface and atmosphere during oral breathing had the same pattern. The total pulmonary pressure-flow curve during nasal breathing was inclined approximately twofold in the nasal pressure-flow curve. The nasal contribution at a flow rate of 0.5 liters per second was 53 % of the total pulmonary resistance in the fourth degree classification. The method presented here is well-suited for evaluating the resistance to airflow between nose and pleural surface of patients with anatomical, as well as functional, nasal obstruction. This study was made while the author was a research fellow of Washington University School of Medicine. The author gratefully acknowledges the invaluable suggestions and criticisms of Dr. J. R. Ogura, the professor of the Department of Otolaryngology, Washington University School of Medicine. REFERENCES BUTLER, J.: Work of breathing through the nose. Clin. Sci. 19: 55-62, 1960. CRAIG, A. B., Jr., DVORAK, M., and MclLREATH, F. J.: Resistance to airflow through the nose. Ann. Otol., Rhinol. and Laryngol. 47: 589-603, 1965. FERRIS, B. G., MEAD, J., and OPIE, L. R.: Partitioning of respiratory flow resistance in man. J. Appl. Physiol. 19: 653-658, 1964. OGURA, J. R., NELSON, J. R., DAMMKOEHLER, R., KAWASAKI, M., and TOGAWA, K.: Experimental observations on the relationships between upper airway obstructions and pulmonary function. Ann. Otolaryngol. 73: 381-403, 1964. OGURA, J. R., TOGAWA, K., DAMMKOEHLER, R., NELSON, J. R., and KAWASAKI, M.: Nasal obstruction and the mechanics of breathing. Arch. Otolaryngol. 83: 135-150, 1966. OGURA, J. R., UNNO, T., and NELSON, J. R.: Nasal surgery. Physiological considerations of nasal obstruction. Arch. Otolaryngol. 88: 288-295, 1968a. OGURA, J. R., UNNO, T., and NELSON, J. R.: Baseline values in pulmonary mechanics for physiologic surgery of the nose. Preliminary report. Ann. Otol., Rhinol. and Laryngol. 77: 367-397, 1968b.
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ROHRER, F.: Der Stromungswiderstand in den Menshlichen Atemwegen und der Einfluss der unregelmassigen Verzweigung des Bronchialsystems auf den Atmungsverlauf in verscheidenen Lungenbezirken. Arch. ges. Physiol. 162: 225-299, 1915. SPEIZER, F. E. and FRANK, N. R.: A technique for measuring nasal and pulmonary flow resistance simultaneously. J. Appl. Physiol. 19: 176-178,1964. TOGAW A, K. and OGURA, J. H. : Physiologic relationships between nasal breathing and pulmonary function. The Laryngoscope 76: 30-63, 1966. UNNO, T., NELSON, J. R., and OGURA, J. H.: The effects of nasal obstruction on pulmonary, airway and tissue resistance. The Laryngoscope 78: 1119-1139, 1968. USUl, N., NAGOSHI, Y., HAYAKAWA, K., ISHIZUKA, Y., SUEMITSU, M., and KONNO, A.: The influence of nasal obstruction on pulmonary mechanics. J. Med. Soc. Toho 19: 695-701, 1972. USUl, N.: Effect of neo-synephrine nasal spray on pulmonary resistance in man. Auris· Nasus·Larynx (Tokyo) 3: 53-63, 1976.
Request reprints from: Dr. Nobuo Usui, Department of Otorhinolaryngology, Toho University School of Medicine, 6-11-1, Ohmori-nishi, Ohta-ku, Tokyo 143, Japan