APPLIED PH~sroLocy Vol. 39, No. 5, November 1975.
JOURNALOF
Glottal
Printed
aperture
ANDREW Department
in U.S.A.
during
C. JACKSON, of Physiology,
panting
with voluntary
C., PHILIP J. GULESIAN, JR., AND JERE during panting with voluntary limitation of tidal volume. J. Appl. Physiol. 39(5): 834-836. 1975.-A disadvantage of the forced oscillatory technique for measuring total respiratory resistance (namely, that it is usually done during quiet breathing breathing patterns where the glottic aperor breathing holdingture may be highly variable) was overcome by making the measurement during panting. The imposed forced oscillations (7 Hz) were distinguished from the spontaneous quiet breathing and panting frequencies by ensemble averaging. However, when panting was voluntarily restricted so as to standardize the quiet breathing and panting flow amplitudes, resistance values frequently increased. The suggestion that partial glottal closure occurred during voluntarily restricted panting was confirmed by simultaneous inspection of the glottis with a fiberoptic bronchoscope. Thus, maximal opening of the glottis is assured only during unrestricted panting.
forced
oscillations;
ensemble
averaging;
vocal
cords
AREA OF THE GLOTTIS has been shown to be highly variable during quiet breathing, increasing during inspiration and decreasing during expiration (4, 6). These glottal movements cause the upper airway resistance to be increased in magnitude and variability, resulting in a loss of precision with which airway resistance measurements can detect small changes in pulmonary flow resistance caused by disease. The signal-to-noise ratio can be improved if resistance is measured during panting, a maneuver which maximizes glottal area and minimizes the variability in its area (1). A major criticism of the forced oscillation technique for measuring resistance is that it is difficult to use during panting (2). This technique is applied only during quiet breathing because it is essential that the signal representing the response to the forced oscillations be separated from the signal due to spontaneous breathing. Adequate discrimination between these two signals is difficult to accomplish during panting since their frequencies are nearly equal. To achieve separation of these signals, we utilized a technique for filtering by ensemble averaging (5) which is commonly used in neurophysiology. In brief, we sample the flow and pressure signals at numerous points during the imposed, or forced oscillatory, cycle. The ensemble average over several of those cycles is then found. When sampling extends over several breaths, the fluctuation due to breathing averages to zero so that, in effect, ideal filtering is achieved; only the flow variation due to the imposed pressure remains. But this average includes samples at different flow rates and, since the flow resistance increases with flow, the result is sensitive to the amplitude of flow produced by breathingthe higher the flow amplitude, the lower the average fluctuation in flow for a given imposed pressure, and the higher the resistance value obtained. To standardize and also minimize these effects, we asked the subjects to voluntarily restrict their tidal volumes during panting so as to achieve peak flows equivalent to those during quiet breathing. It has been reported that glottal area during panting at THE
of tidal volume
PHILIP J. GULESIAN, JR., AND JERE MEAD Harvard School of Public Health, Boston, Massachusetts 02115
JACKSON, ANDREW MEAD. Glottal aperture
resistance;
limitation
a constant frequency increases with panting volume (6). However, it was not shown to what extent these glottal movements affected resistance. The present study was undertaken to determine whether or not voluntary restriction of panting volume in itself significantly affects respiratory resistance. Further, the technique enabled us to view the glottis to see if this breathing pattern can in fact be used to minimize flow effects while still maintaining maximal glottal opening. METHODS
A group of three healthy, nonsmoking male volunteer subjects was studied in the sitting position. The experimental apparatus is shown schematically in Fig. 1. Respiratory resistance was measured by the forced oscillatory technique. The oscillations in pressure and flow were produced by a method similar to one described by Goldman et al. (3) consisting of a 12-in loudspeaker (Acoustic Research) driven by a fixed frequency (7 Hz) sine-wave generator and power amplifier. A large-diameter branch in the loudspeakermouthpiece tubing allowed the subjects to breathe room air. This tube, since it is essentially a large inertance, represents a relatively low impedance pathway to the subjects’ breathing effort (at the lower, quiet breathing frequencies) and a relatively high impedance to the higher frequency forced oscillations (7 Hz). In this way we were able to produce pressure and flow oscillations with sufficient amplitude. The added dead space was cleared by a constant bias flow. During the panting maneuvers, where the frequency of the spontaneous breathing effort was nearly equal to that of the forced oscillations, the side tube was not useful and it was removed. Mouth pressure was sensed by a pressure transducer (Validyne, model MP 45). Airflow was measured by a pneumotachograph (Fleisch no. 3) and a differential pressure transducer (Validyne, model MP 45). The pressure and flow signals were amplified and recorded on a strip-chart recorder. The flow signal was integrated to provide a signal proportional to changes in lung volume. This volume signal was recorded and displayed on the vertical axis of an oscilloscope which was visible to the subject. Ensemble averaging (5), based on the forcing frequency, was used to filter the pressure and flow signals. This technique was selected because it is theoretically an ideal filtering process allowing separation of the components even though their frequencies are nearly equal, as is the case during panting. The process of filtering by ensemble averaging, as well as the method used to calculate resistance, is illustrated in Fig. 2. Idealized flow and pressure tracings during one respiratory cycle are shown on the left. In the ensemble averaging process the pressure and flow signals, P(t) and V(t), respectively, are digitized at a rate such that M samples are taken during each forced oscillatory cycle. These signals are then broken into segments (as shown in the middle illustration) where where the period, 7’, is equal to that of the forced oscillation. The ensemble averages of each mth point within all segments are then found by the equations $?a)
=N+
gP(t,+nT) n-1
Downloaded from www.physiology.org/journal/jappl by ${individualUser.givenNames} ${individualUser.surname} (132.210.236.020) on January 10, 2019.
GLOTTAL
APERTURE
DURING
CONTROLLED ,
TV MONITORS
r
TV $AMERA -
/ v SPECIAL EFFECTS
6
x--
-c== ===-.
835
BREATHING FIBER OPTIC BRONCHOSCOPE
FIG. 1. METHODS).
. I I cl/
c
Schematic diagram of apparatus (see,
.
’
-&ENERATOR VIDEO
I
TAPE
I
I
Y f
f
7
f
RECORD
PDP II DIBITAL
~(1). Pa&),
I
and
V(t)
for m = 1,2,3--,M
h?J =
N-l
2
V(t,
+ nT>
n-1
where N = total number of forced oscillations, or segments, used in the averaging process. The resulting pressure and flow curves represent a single “average” response curve where that portion of the signal due to the breathing effort is eliminated (as shown on the right). From these “average” pressure and flow response curves, the resistance is calculated by dividing the magnitude of pressure by the magnitude of flow at the point where flow is at a maximum. The subject’s glottis was viewed by a fiberoptic bronchoscope (Olympus, type 5B2) while resistance was being measured. The bronchoscope was passed through the nasal passage, without anesthetic, over the epiglottis and to a point where the vocal folds were in full view. The bronchoscope was directly coupled to a closedcircuit television camera (Panasonic, model WV-360P) and displayed on a television monitor. A second television camera recorded the face of an oscilloscope displaying the pressure and flow sigmas. The video signals from both cameras were mixed on a special effect generator (Sony) and recorded on a videotape rerecorder (Sony, AV-3650). In this way we were able to obtain a record both of the glottal movements and of the simultaneous pressures and flows during the entire run. Experimental procedure. Resistance was measured during three different breathing patterns : I) quiet breathing, 2) panting at 2 Hz, and 3) controlled panting at 2 Hz (the subjects were coached to take tidal volumes small enough so that the peak flow rates did not exceed those during quiet breathing). To standardize the volume history, each run was preceded by a relatively slow vital capacity maneuver. In the initial run the subject was instructed to breathe quietly near his normal functional residual capacity (FRC) after the vital capacity maneuver. The end-expiratory position was indicated on the oscilloscope face and the subject was instructed to perform all subsequent runs near this same FRC. Once the subjects’ FRC and breathing pattern stabilized (usually 2-3 breaths), ensemble averaging was initiated and lasted for approximately 15-20 s. The subject again performed a vital capacity maneuver so that integrator drift could be checked. Between three and five determinations were made for each of the three breathing patterns which were performed in no specific order. RESULTS
AND
A typical volume (V)
DISCUSSION
recording for each
of flow (V), mouth of the three breathing
pressure patterns
(Pao), and is shown in
t,t
2T
t,‘+4T I
I
T
2T
3T
4T
tm I
‘m
ST
TIME FIG. 2. Illustration of filtering by ensemble averaging. In this example the ensemble average of only one point (at t = t, + nT, where n = 0, 1, 2, 3, 4) is illustrated. In this study M = 150 and typically N > 100. Curves on the right are made from ensemble average of each mth point (see also METHODS).
Fig. 3. During quiet breathing, the peak flows were approximately 0.8 l/s. The peak flow rate increased to over 2.0 l/s when the subject shifted to a panting breathing pattern. Similar increases in peak flows were observed in all three subjects. In the third maneuver, the subjects’ peak flows were similar in magnitude to those during quiet breathing. Figure 4 shows sketches made from the television monitor of one subject’s (AJ) glottal opening during quiet breathing (Fig. 4;A), panting (Fig. 4@, and restricted panting (Fig. 4C). This subject’s glottic aperture was significantly narrowed during quiet breathing and glottal area was highly variable. When he panted his vocal folds became maximally abducted and remained in this position throughout the cycle. However, when asked to voluntarily restrict his tidal volume, this subject’s glottis again became partially closed. But, during restricted panting, cyclical variations in the area were not seen. The resistance measurements during these quiet breath-
Downloaded from www.physiology.org/journal/jappl by ${individualUser.givenNames} ${individualUser.surname} (132.210.236.020) on January 10, 2019.
836
JACKSON,
AND
MEAD
FIO. 3. Typical recording of flow (upper curves), mouth pressure (middle curves), and volume (lower curves) during the three breathing maneuvers. In the quiet breathing flow and pressure tracings, high-frequency (7 Hz) forced oscillations can be distinguished from spontaneous breathing. Horizontal bars at bottom of each set of curves indicate time during which resistance was measured.
2
*.-_ ”
GULESIAN,
9°C *,
.’ P
#‘
A
5
FIG. 4. Sketches of glottal opening in subject AJ made from television monitor during quiet breathing (A) panting at 2 Hz (B), and panting at 2 Hz while panting volumes are voluntarily restricted (C). Glottal area represented in A is that which existed throughout the majority of the quiet breathing cycle. During both panting maneuvers, there was no cyclical variations in area.
1. Respiratory resistance during quiet breathing, panting, and restricted panting
TABLE
Subj AJ MM LJ
Respiratory Quiet breathing 1.70 1.49 2.25
f f f
.15 .08 .ll
Resistance, cmHzO/l per s Restricted panting Panting 1.77 2.01 2.55
f f f
.14 .36 .35
1.56 1.64 2.44
f f f
.13 .16 .38
ing, and
panting, and restricted panting maneuvers were 1.73, 1.88, 1.43 cmHsO/l per s, respectively. Of the three subjects studied, both AJ and LJ showed narrowing of the glottic aperture during the restricted panting maneuver. These two subjects had reduced glottic area during quiet breathing with a great deal of cyclical variation and maximal abduction during panting. The third subject’s (MM) glottis appeared to be maximally open during all three maneuvers with no cyclical variation, even during the quiet breathing.
The resistances measured during these breathing patterns for all subjects are given in Table 1. Subject MM had similar glottal area during all three procedures. When he voluntarily restricted his panting volume and thus reduced peak flows, his resistance decreased, and this reduction in resistance may be attributed to reduced flow. During quiet breathing and restricted panting, the flow was of similar magnitude, as was the glottal area; as expected, there was no significant difference between the resistance during these breathing patterns. In subjects AJ and LJ, when the flow effects were reduced by voluntary restriction of panting volumes, the glottal effects were reintroduced. Subject LJ’s increase in resistance due to reduced glottal area was apparently offset by the decrease in resistance due to the reduced flows. The reduction in resistance due to reduced flows in subject AJ during restricted panting was apparently larger in magnitude than the elevation in resistance due to decreased glottal area. Thus there was a net decrease in resistance when the flows were voluntarily restricted. To summarize, unrestricted panting has the advantage of leading to an open glottis, but the disadvantages of resulting in flows which in themselves contribute to the variability of resistance measurements. When subjects voluntarily restrict their panting so as to standardize flow, two of three exhibited glottal narrowing. Although through ensemble averaging the method of forced oscillations can be extended to panting, the fact that the result is sensitive to flow per se, together with our present observation that when flow is then voluntarily restricted glottal narrowing occurs, limits the usefulness of the technique. The authors thank Michael PhD for their assistance with This study was supported Heart and Lung Institutes. Received
for publication
S. Morgan PhD and Larry R. Johnson this study. by Grant HL-14580 from the National
22 January
1975.
REFERENCES 1. BUTLER, J., C. G. CARO, R. ALCALA, AND A. B. DuBois. Physiological factors affecting airway resistance in normal subjects and in panting with obstructive respiratory disease. J. Clin. Invest. 39: 584-591, 1960. 2. FISHER, A. G., A. B. DUBOIS, AND R. W. HYDE. Evaluation of the forced oscillation technique for the determination of resistance to breathing. J. Clin. Invest. 47: 2045-2057, 1968. 3. GOLDMAN, M., R. J. KNUDSON, J. MEAD, N. PETERSON, J. R. SCHWABER, AND M. E. WOHL. A simplified measurement of respira-
tory resistance by forced oscillations. J. ApPl. Physiol. 28: 113-l 16, 1970. 4. HOOPER, F. H. The respiratory function of the human larynx. N. Y. State J. Med. 42 : 2-8, 1885. 5. ROSENBLITH, W. A. (Editor). Processing Neuroelectric Data. Cambridge, Mass.: MIT, 1962, p. 21-22. 6. ST;~NESCU, D. C., J. PAXTIJN, J. CLEMENT, AND K. P. VAN DE WOESTIJNE. Glottis opening and airway resistance. J. A#. Physiol. 34: 460-466, 1972.
Downloaded from www.physiology.org/journal/jappl by ${individualUser.givenNames} ${individualUser.surname} (132.210.236.020) on January 10, 2019.
JOURNALOF
Glottal
Printed
aperture
ANDREW Department
in U.S.A.
during
C. JACKSON, of Physiology,
panting
with voluntary
C., PHILIP J. GULESIAN, JR., AND JERE during panting with voluntary limitation of tidal volume. J. Appl. Physiol. 39(5): 834-836. 1975.-A disadvantage of the forced oscillatory technique for measuring total respiratory resistance (namely, that it is usually done during quiet breathing breathing patterns where the glottic aperor breathing holdingture may be highly variable) was overcome by making the measurement during panting. The imposed forced oscillations (7 Hz) were distinguished from the spontaneous quiet breathing and panting frequencies by ensemble averaging. However, when panting was voluntarily restricted so as to standardize the quiet breathing and panting flow amplitudes, resistance values frequently increased. The suggestion that partial glottal closure occurred during voluntarily restricted panting was confirmed by simultaneous inspection of the glottis with a fiberoptic bronchoscope. Thus, maximal opening of the glottis is assured only during unrestricted panting.
forced
oscillations;
ensemble
averaging;
vocal
cords
AREA OF THE GLOTTIS has been shown to be highly variable during quiet breathing, increasing during inspiration and decreasing during expiration (4, 6). These glottal movements cause the upper airway resistance to be increased in magnitude and variability, resulting in a loss of precision with which airway resistance measurements can detect small changes in pulmonary flow resistance caused by disease. The signal-to-noise ratio can be improved if resistance is measured during panting, a maneuver which maximizes glottal area and minimizes the variability in its area (1). A major criticism of the forced oscillation technique for measuring resistance is that it is difficult to use during panting (2). This technique is applied only during quiet breathing because it is essential that the signal representing the response to the forced oscillations be separated from the signal due to spontaneous breathing. Adequate discrimination between these two signals is difficult to accomplish during panting since their frequencies are nearly equal. To achieve separation of these signals, we utilized a technique for filtering by ensemble averaging (5) which is commonly used in neurophysiology. In brief, we sample the flow and pressure signals at numerous points during the imposed, or forced oscillatory, cycle. The ensemble average over several of those cycles is then found. When sampling extends over several breaths, the fluctuation due to breathing averages to zero so that, in effect, ideal filtering is achieved; only the flow variation due to the imposed pressure remains. But this average includes samples at different flow rates and, since the flow resistance increases with flow, the result is sensitive to the amplitude of flow produced by breathingthe higher the flow amplitude, the lower the average fluctuation in flow for a given imposed pressure, and the higher the resistance value obtained. To standardize and also minimize these effects, we asked the subjects to voluntarily restrict their tidal volumes during panting so as to achieve peak flows equivalent to those during quiet breathing. It has been reported that glottal area during panting at THE
of tidal volume
PHILIP J. GULESIAN, JR., AND JERE MEAD Harvard School of Public Health, Boston, Massachusetts 02115
JACKSON, ANDREW MEAD. Glottal aperture
resistance;
limitation
a constant frequency increases with panting volume (6). However, it was not shown to what extent these glottal movements affected resistance. The present study was undertaken to determine whether or not voluntary restriction of panting volume in itself significantly affects respiratory resistance. Further, the technique enabled us to view the glottis to see if this breathing pattern can in fact be used to minimize flow effects while still maintaining maximal glottal opening. METHODS
A group of three healthy, nonsmoking male volunteer subjects was studied in the sitting position. The experimental apparatus is shown schematically in Fig. 1. Respiratory resistance was measured by the forced oscillatory technique. The oscillations in pressure and flow were produced by a method similar to one described by Goldman et al. (3) consisting of a 12-in loudspeaker (Acoustic Research) driven by a fixed frequency (7 Hz) sine-wave generator and power amplifier. A large-diameter branch in the loudspeakermouthpiece tubing allowed the subjects to breathe room air. This tube, since it is essentially a large inertance, represents a relatively low impedance pathway to the subjects’ breathing effort (at the lower, quiet breathing frequencies) and a relatively high impedance to the higher frequency forced oscillations (7 Hz). In this way we were able to produce pressure and flow oscillations with sufficient amplitude. The added dead space was cleared by a constant bias flow. During the panting maneuvers, where the frequency of the spontaneous breathing effort was nearly equal to that of the forced oscillations, the side tube was not useful and it was removed. Mouth pressure was sensed by a pressure transducer (Validyne, model MP 45). Airflow was measured by a pneumotachograph (Fleisch no. 3) and a differential pressure transducer (Validyne, model MP 45). The pressure and flow signals were amplified and recorded on a strip-chart recorder. The flow signal was integrated to provide a signal proportional to changes in lung volume. This volume signal was recorded and displayed on the vertical axis of an oscilloscope which was visible to the subject. Ensemble averaging (5), based on the forcing frequency, was used to filter the pressure and flow signals. This technique was selected because it is theoretically an ideal filtering process allowing separation of the components even though their frequencies are nearly equal, as is the case during panting. The process of filtering by ensemble averaging, as well as the method used to calculate resistance, is illustrated in Fig. 2. Idealized flow and pressure tracings during one respiratory cycle are shown on the left. In the ensemble averaging process the pressure and flow signals, P(t) and V(t), respectively, are digitized at a rate such that M samples are taken during each forced oscillatory cycle. These signals are then broken into segments (as shown in the middle illustration) where where the period, 7’, is equal to that of the forced oscillation. The ensemble averages of each mth point within all segments are then found by the equations $?a)
=N+
gP(t,+nT) n-1
Downloaded from www.physiology.org/journal/jappl by ${individualUser.givenNames} ${individualUser.surname} (132.210.236.020) on January 10, 2019.
GLOTTAL
APERTURE
DURING
CONTROLLED ,
TV MONITORS
r
TV $AMERA -
/ v SPECIAL EFFECTS
6
x--
-c== ===-.
835
BREATHING FIBER OPTIC BRONCHOSCOPE
FIG. 1. METHODS).
. I I cl/
c
Schematic diagram of apparatus (see,
.
’
-&ENERATOR VIDEO
I
TAPE
I
I
Y f
f
7
f
RECORD
PDP II DIBITAL
~(1). Pa&),
I
and
V(t)
for m = 1,2,3--,M
h?J =
N-l
2
V(t,
+ nT>
n-1
where N = total number of forced oscillations, or segments, used in the averaging process. The resulting pressure and flow curves represent a single “average” response curve where that portion of the signal due to the breathing effort is eliminated (as shown on the right). From these “average” pressure and flow response curves, the resistance is calculated by dividing the magnitude of pressure by the magnitude of flow at the point where flow is at a maximum. The subject’s glottis was viewed by a fiberoptic bronchoscope (Olympus, type 5B2) while resistance was being measured. The bronchoscope was passed through the nasal passage, without anesthetic, over the epiglottis and to a point where the vocal folds were in full view. The bronchoscope was directly coupled to a closedcircuit television camera (Panasonic, model WV-360P) and displayed on a television monitor. A second television camera recorded the face of an oscilloscope displaying the pressure and flow sigmas. The video signals from both cameras were mixed on a special effect generator (Sony) and recorded on a videotape rerecorder (Sony, AV-3650). In this way we were able to obtain a record both of the glottal movements and of the simultaneous pressures and flows during the entire run. Experimental procedure. Resistance was measured during three different breathing patterns : I) quiet breathing, 2) panting at 2 Hz, and 3) controlled panting at 2 Hz (the subjects were coached to take tidal volumes small enough so that the peak flow rates did not exceed those during quiet breathing). To standardize the volume history, each run was preceded by a relatively slow vital capacity maneuver. In the initial run the subject was instructed to breathe quietly near his normal functional residual capacity (FRC) after the vital capacity maneuver. The end-expiratory position was indicated on the oscilloscope face and the subject was instructed to perform all subsequent runs near this same FRC. Once the subjects’ FRC and breathing pattern stabilized (usually 2-3 breaths), ensemble averaging was initiated and lasted for approximately 15-20 s. The subject again performed a vital capacity maneuver so that integrator drift could be checked. Between three and five determinations were made for each of the three breathing patterns which were performed in no specific order. RESULTS
AND
A typical volume (V)
DISCUSSION
recording for each
of flow (V), mouth of the three breathing
pressure patterns
(Pao), and is shown in
t,t
2T
t,‘+4T I
I
T
2T
3T
4T
tm I
‘m
ST
TIME FIG. 2. Illustration of filtering by ensemble averaging. In this example the ensemble average of only one point (at t = t, + nT, where n = 0, 1, 2, 3, 4) is illustrated. In this study M = 150 and typically N > 100. Curves on the right are made from ensemble average of each mth point (see also METHODS).
Fig. 3. During quiet breathing, the peak flows were approximately 0.8 l/s. The peak flow rate increased to over 2.0 l/s when the subject shifted to a panting breathing pattern. Similar increases in peak flows were observed in all three subjects. In the third maneuver, the subjects’ peak flows were similar in magnitude to those during quiet breathing. Figure 4 shows sketches made from the television monitor of one subject’s (AJ) glottal opening during quiet breathing (Fig. 4;A), panting (Fig. 4@, and restricted panting (Fig. 4C). This subject’s glottic aperture was significantly narrowed during quiet breathing and glottal area was highly variable. When he panted his vocal folds became maximally abducted and remained in this position throughout the cycle. However, when asked to voluntarily restrict his tidal volume, this subject’s glottis again became partially closed. But, during restricted panting, cyclical variations in the area were not seen. The resistance measurements during these quiet breath-
Downloaded from www.physiology.org/journal/jappl by ${individualUser.givenNames} ${individualUser.surname} (132.210.236.020) on January 10, 2019.
836
JACKSON,
AND
MEAD
FIO. 3. Typical recording of flow (upper curves), mouth pressure (middle curves), and volume (lower curves) during the three breathing maneuvers. In the quiet breathing flow and pressure tracings, high-frequency (7 Hz) forced oscillations can be distinguished from spontaneous breathing. Horizontal bars at bottom of each set of curves indicate time during which resistance was measured.
2
*.-_ ”
GULESIAN,
9°C *,
.’ P
#‘
A
5
FIG. 4. Sketches of glottal opening in subject AJ made from television monitor during quiet breathing (A) panting at 2 Hz (B), and panting at 2 Hz while panting volumes are voluntarily restricted (C). Glottal area represented in A is that which existed throughout the majority of the quiet breathing cycle. During both panting maneuvers, there was no cyclical variations in area.
1. Respiratory resistance during quiet breathing, panting, and restricted panting
TABLE
Subj AJ MM LJ
Respiratory Quiet breathing 1.70 1.49 2.25
f f f
.15 .08 .ll
Resistance, cmHzO/l per s Restricted panting Panting 1.77 2.01 2.55
f f f
.14 .36 .35
1.56 1.64 2.44
f f f
.13 .16 .38
ing, and
panting, and restricted panting maneuvers were 1.73, 1.88, 1.43 cmHsO/l per s, respectively. Of the three subjects studied, both AJ and LJ showed narrowing of the glottic aperture during the restricted panting maneuver. These two subjects had reduced glottic area during quiet breathing with a great deal of cyclical variation and maximal abduction during panting. The third subject’s (MM) glottis appeared to be maximally open during all three maneuvers with no cyclical variation, even during the quiet breathing.
The resistances measured during these breathing patterns for all subjects are given in Table 1. Subject MM had similar glottal area during all three procedures. When he voluntarily restricted his panting volume and thus reduced peak flows, his resistance decreased, and this reduction in resistance may be attributed to reduced flow. During quiet breathing and restricted panting, the flow was of similar magnitude, as was the glottal area; as expected, there was no significant difference between the resistance during these breathing patterns. In subjects AJ and LJ, when the flow effects were reduced by voluntary restriction of panting volumes, the glottal effects were reintroduced. Subject LJ’s increase in resistance due to reduced glottal area was apparently offset by the decrease in resistance due to the reduced flows. The reduction in resistance due to reduced flows in subject AJ during restricted panting was apparently larger in magnitude than the elevation in resistance due to decreased glottal area. Thus there was a net decrease in resistance when the flows were voluntarily restricted. To summarize, unrestricted panting has the advantage of leading to an open glottis, but the disadvantages of resulting in flows which in themselves contribute to the variability of resistance measurements. When subjects voluntarily restrict their panting so as to standardize flow, two of three exhibited glottal narrowing. Although through ensemble averaging the method of forced oscillations can be extended to panting, the fact that the result is sensitive to flow per se, together with our present observation that when flow is then voluntarily restricted glottal narrowing occurs, limits the usefulness of the technique. The authors thank Michael PhD for their assistance with This study was supported Heart and Lung Institutes. Received
for publication
S. Morgan PhD and Larry R. Johnson this study. by Grant HL-14580 from the National
22 January
1975.
REFERENCES 1. BUTLER, J., C. G. CARO, R. ALCALA, AND A. B. DuBois. Physiological factors affecting airway resistance in normal subjects and in panting with obstructive respiratory disease. J. Clin. Invest. 39: 584-591, 1960. 2. FISHER, A. G., A. B. DUBOIS, AND R. W. HYDE. Evaluation of the forced oscillation technique for the determination of resistance to breathing. J. Clin. Invest. 47: 2045-2057, 1968. 3. GOLDMAN, M., R. J. KNUDSON, J. MEAD, N. PETERSON, J. R. SCHWABER, AND M. E. WOHL. A simplified measurement of respira-
tory resistance by forced oscillations. J. ApPl. Physiol. 28: 113-l 16, 1970. 4. HOOPER, F. H. The respiratory function of the human larynx. N. Y. State J. Med. 42 : 2-8, 1885. 5. ROSENBLITH, W. A. (Editor). Processing Neuroelectric Data. Cambridge, Mass.: MIT, 1962, p. 21-22. 6. ST;~NESCU, D. C., J. PAXTIJN, J. CLEMENT, AND K. P. VAN DE WOESTIJNE. Glottis opening and airway resistance. J. A#. Physiol. 34: 460-466, 1972.
Downloaded from www.physiology.org/journal/jappl by ${individualUser.givenNames} ${individualUser.surname} (132.210.236.020) on January 10, 2019.
