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Physiologic Features of Upper Airway Obstruction
Physiologic Features of Upper Airway Obstruction * .\Jarvin A. Sackner, M.D., F.C.C.P. o o
In seven patients with upper airway obstruction caused by tracheal or vocal cord lesions, pulmonary function tests revealed normal distribution of ventilation and a moderate to marked elevation in airway resistance unresponsive to bronchodilators. Such findings ought to be highly specific for this condition, a diagnosis which often is unsuspected cUnically.
As a cause of dyspnea and wheezing in the adult,
obstructive lesions of the larynx and trachea are rarely considered in such differential diagnoses as asthma, chronic bronchitis and emphysema. However, the strategic site of such lesions produces predictable abnormalities in pulmonary function which serve as a guide to definitive endoscopic or roentgenographic confirmation. Thus, one might expect a narrowed trachea to cause obstruction, but °From the Division of Pulmonary Diseases, Department of Internal Medicine, Mount Sinai Medical Center, Miami Beach, Florida. oOChief, Division of Pulmonary Diseases. Reprint requests: Dr. Sackner, Mt. Sinai Medical Center, 4300 Alton Road, Miami Beach 33140
not to create asynchronous emptying of air from the lungs during expiration as detected by tests of the distribution of ventilation because both lungs would be affected to the same degree. However, in obstructive lung diseases, significant lower airways obstruction would give rise to different degrees of obstruction throughout the lungs with attendant uneven distribution of ventilation (Fig 1). Simonsson and Malmberg! confirmed this hypothesis in two patients with tracheal stenosis who had marked reduction in FEV 1.0 and normal single breath nitrogen elimination curves. This article reports seven cases of upper airway obstruction which showed similar physiologic features. In these patients, markedly
A.
B.
FIGURE 1. The schematic figures represent the lungs - the trachea, the branching airways and the alveoli. A. Obstructive lung disease in which the degree of obstruction varies in different airways such that inspired air is not evenly distributed to the alveoli. B. Tracheal obstruction in which air is distributed evenly to the branching airways.
414
CHEST, VOL. 62, NO.4, OCTOBER, 1972
415
PHYSIOLOGIC FEATURES OF UPPER AIRWAY OBSTRUCTION Table I-Characteri.tic. 0/ Patient. with Upper AiTlClay Ob.'TUction. ClI8e Age
Sex
pulmonary function tests in upper airway obstruction. Lung volumes were variable from patient to patient. Tests of distribution of ventilation, the single breath nitrogen elimination curve and the pulmonary nitrogen clearance delay were normal. Maximum breathing capacity and FEV t .n were moderately to markedly reduced. Airway resistance was markedly elevated, ranging from 5 to 18 times the normal values. Diffusing capacity of the lung was normal in those patients measured. Arterial blood gas analysis showed mild hypoxemia in three patients, respiratory alkalosis in four patients and a combined respiratory acidosis and metabolic alkalosis in one patient. No significant change was noted in pulmonary mechanics after administration of bronchodilators.
Lesion
7l
F
Pedunculated polyp of vocal cords following endotracheal intubation
2
61
F
Lymphoma invading and compressing trachea
3
23
F
Squamous cell carcinoma of trachea
4
70
M
Squamous cell carcinoma of trachea
5
58
M
Tracheal stenosis following prolonged intubation and tracheostomy
6
72
F
Undifferentiated carcinoma of thyroid compressing trachea
7
76
M
Tracheal stenosis following tracheostomy of three days' duration
CASE SUMMARIES CASE
This 71-year-old woman was admitted to the hospital after taking an overdose of barbiturates. Endotracheal intubation and mechanical ventilation were required for two days and she was later discharged. She was readmitted two weeks later because of dyspnea, stridor and a croupy cough. Inspiratory and expiratory tracheal wheezing were present. Bronchofiberoscopy revealed a pedunculated polyp at the anterior commissure of the vocal cords. Passage beyond the polyp into the trachea was associated with extreme dyspnea and the instrument was immediately withdrawn. Granulomatous tissue of the vocal cords was removed under direct laryngoscopy with a good clinical result.
elevated values for airway resistance made the dichotomy between the magnitude of obstruction and the normal distribution of ventilation even more striking. METHODS
Displaceable lung volumes were measured with a spirometer. Functional residual capacity was determined by a body plethysmographic technique.s Tests of distribution of ventilation included a single breath nitrogen elimination test3 and a nitrogen washout test with graphic analysis of the washout curve to calculate pulmonary nitrogen clearance delay.! Airway resistance was obtained during panting at one to two cycles per second between 0.25 liter per second inspiratory and expiratory How rate, by the body plethysmographic teehnique.s Diffusing capacity of the lung for carbon monoxide was determined by steady state6 and single breath methods." Arterial blood gases and pH were determined with an Instrumentation Laboratory pH blood gas analyzer. UPPER
Amw AY
I
CASE
2
This 61-year-old woman was admitted to the hospital because of increasing dyspnea of six months' duration. Ten days prior to admission, she developed wheezing, stridor and an uncomfortable sensation in her throat. Bronchoscopy revealed a subglottic bulging which narrowed this region to a small slit. Biopsy of this region was consistent with lymphoma. Bone marrow examination was consistent with chronic lymphatic leukemia. CASE
OBSTRUCTION
3
This 23-year-old woman was hospitalized elsewhere six months prior to admission to our hospital. At that time,
Table I lists the patient characteristics and Table 2 the
Table 2-Pulmonary Function Ted. in Upper AiTlClay Ob,'ruction.* Case VC liters RV liters TLC liters RV/TLC% SBN, % Pulm N, clearance delay % MBC liters/min FEV l.I liters Airway resistance cmH,O/liters/sec Deoss ml/mm Hg x min DeoSB ml/mm Hg x min PO,mm Hg Pco, mm Hg pH units B.E. mEq/liters
2 1.65 1.55 3.15 49
(86)
(Ill)
(95) (117)
88 ( < 1(0)
2.25 1.74 3.99 44 2.0
(78) (105) (88) (119) «2.5)
3.15 0.77 3.92 20 1.6
(88) (58) (SO) (74) «2.5)
17 (35) .84 (63) 17.7 (1053)
30 (45) 1.59 (64) 8.9 (594)
51 (52) 2.20 (65) 9.6 (589)
10.9 (160)
12.6 (129)
21.8 (120) 19.9 (77)
79 24 7.54 0
86
36 7.40 -2
4
3
68
42 7.43 +3
1.07 1.90 2.98 64
(38) (94) (62) (152)
53 ( < 1(0)
5 3.04 4.78 7.92 61 1.6 43
(75) (206) (123) (169) «3.5) ( < 1(0)
15 (23) .47 (20) 22.0 (1667)
23 (24) 1.39 (43) 10.6 (1831)
55 50 7.47 +10
10.5 (90) 28.1 (117) 64 23 7.55 0
6 1.95 2.26 4.21 54 2.2
(90) (155) (116) (135) «3.5)
28 (54) 1.03 (68) 6.5 (501) 9.8 (140) 86 30 7.48 0
7 3.17 2.59 5.76 45 1.5 46
(102) (119) (l09) (110) «3.5) «100)
42 (60) 1.56 (61) 4.1 (469) 24.3 (149) 83 32 7.46 0
*Values within parentheses indicate percent of predicted normal except for tests of distribution where highest normal value is listed.
CHEST, VOL. 62, NO.4, OCTOBER, 1972
416
MARVIN A. SACKNER
she had an enlarged thyroid which compressed the trachea. A thyroidectomy was carried out and squamous cell carcinoma was found within the gland. Postoperatively, a tracheostomy was left in situ for two months. Two months following decannulation, she noted dyspnea and a feeling of obstruction to breathing low in her throat but denied wheezing. Physical examination at our hospital revealed tracheal wheezing during forced inspiration and expiration. Bronchofiberscopy revealed narrowing of the trachea in its midportion to about 6 mm in diameter. The neck was reexplored and squamous cell carcinoma was found within the trachea, neck and mediastinum. The patient died eight months later with an inoperable stenosis of the thoracic portion of the trachea. CASE
4
This 70-year-old man was admitted to our hospital for evaluation of dyspnea and stridor of one year's duration. He had a ten-year history of pulmonary lymphoma which was treated with three courses of cobalt radiotherapy to the mediastinum and lung fields. Recurrent pleural effusions required multiple thoracenteses. The physical appearance of his neck suggested a superior vena cava syndrome. He was extremely hoarse and could speak only with a whisper. A tracheal wheeze was present during both quiet inspiration and expiration. Bronchofiberoscopy revealed a large multinodular fleshy tumor in the cervical trachea. The tracheal lumen through this tumor was only a few millimeters in diameter. A minimal resection of the tumor was carried out under direct bronchoscopy because of a great deal of bleeding. Endotracheal intubation for four days was necessary until the edema around the tumor subsided. The biopsy was consistent with an undifferentiated squamous cell carcinoma. He was given a course of cyclophosphamide and improved. Pulmonary function tests repeated two months following surgery revealed an increase in VC to 1.46 liters, MBC to 30 liters per minute and FEV1 .0 to 1.02 liters. The airway resistance dropped from 22.0 cm H20 per liters per second ( 1667 percent of predicted normal) to 5.9 em H20 per liters per second (268 percent of predicted normal). CASES
This 58-year-old man was admitted to the hospital with a right lower lobe pneumonia and congestive heart failure. On the day following admission, he suffered a cardiac arrest and required endotracheal intubation. He was intubated for four days and then tracheostomized. Continuous mechanical ventilation for three weeks was necessary for respiratory failure. He developed renal shutdown which required multiple dialyses. Six weeks after admission, the tracheostomy tube was removed. Three weeks later, he developed increasing dyspnea and wheezing. Physical examination revealed a tracheal wheeze and bronchofiberscopy showed marked tracheal stenosis at the tracheostomy site. The lumen was estimated at approximately 6 to 7 mm in diameter. After bougie dilatation the airway resistance fell from 10.6 cm H20 per liters per second (1831 percent predicted normal) to 9.4 cm H20 per liters per second (1382 percent predicted normal). CASE
6
This 72-year-old woman was admitted because of pain in the throat and a nonproductive cough of one week's duration. Wheezing was present over the trachea; it was also transmitted to the chest. An enlarged thyroid gland was present.
Chest roentgenogram revealed a large mediastinal mass which upon radioisotopic scanning was indicative of thyroid tissue. An incisional biopsy revealed an undifferentiated carcinoma of the thyroid gland. CASE
7
This 76-year-old man with carcinoma of the tongue underwent hemiglossectomy along with an elective tracheostomy. The latter was terminated after three days. Two weeks following surgery, he noticed dyspnea and noisy breathing. This progressed in severity and he was admitted two months later for evaluation. A tracheal wheeze was heard during forced inspiration and expiration. Bronchoflberscopic cine revealed an edematous subglottic membrane which reduced the tracheal lumen to about 20 percent of the original area. Pulmonary function tests revealed an elevation in airway resivtance to 469 percent of predicted normal. He was placed upon prednisone 60 mg a day and had marked subjective improvement within six days. No wheeze could be heard on auscultation over the trachea. Airway resistance fell to within normal limits of 1.2 cm H20 per liters per second (148 percent predicted normal) and bronchoflberscopic cine revealed shrinkage of the subglottic membrane such that the lumen was reduced to about 40 percent of its original area. DISCUSSION
The present study confirms the work of Simonsson and Malmberg! who pointed out that tracheal obstruction is associated with a normal distribution of ventilation and reduced FEV 1.0. Airway resistance in our cases was moderately to markedly elevated and made the dichotomy between the severe obstruction to air How and the normal distribution of ventilation even more striking. As a further test of fixed upper airway obstruction, there was no improvement of airway resistance after administration of bronchodilators. Other tests of pulmonary function have been advocated to detect upper airway obstruction. Thus, the ratio of peak expiratory to inspiratory Howat the midvolume point of the vital capacity is said to be unity in fixed tracheal obstruction, whereas this ratio will be less than unity in chronic obstructive pulmonary diseases.v" However, if there is an inconstant upper airway obstruction, the location becomes important because of transmural pressure gradients. The extrathoracic lesion causes slowing predominantly in inspiration and the intrathoracic lesion causes slowing predominantly in expiration. These transmural gradients only become significant during forced ventilatory maneuvers when there are large swings in transpulmonary pressure. The How rate over which airway resistance was calculated in the present study was low, ie, between 0.25 liters per second inspiratory and expiratory How. Thus, airway resistance estimated under these circumstances would be relatively insensitive to inconstant upper airway obstructions. For example, in emphysema, a CHEST, VOL. 62, NO.4, OCTOBER, 1972
PHYSIOLOGIC FEATURES OF UPPER AIRWAY OBSTRUCTION
marked reduction in FEV 1.0 is associated with a normal or slightly elevated expiratory airway resistance at these low How rates.'? Furthermore, in such patients who have tracheobronchial collapse during forced expiration, the inspiratory airway resistance is normal, The spotty nature of the destruction and dilatation of the acinus in emphysema produces uneven distribution of ventilation. In contrast to such findings, patients with fixed tracheal obstructions show an increase in airway resistance over both the inspiratory and expiratory phases of respiration even at low How rates and distribution of ventilation is normal. False positive diagnoses ought not to occur but if coexistent obstructive or restrictive lung diseases are present, then distribution of ventilation might be uneven. ADDENDUM
417 !U:FERENCES
Simonsson BG, Malmberg R: Differentiation between localized and generalized airway obstruction. Thorax 19:416, 1964 2 DuBois AB, Botelho SY, Bedell GN, et al: A rapid plethysmographic method for measuring thoracic gas volume: A comparison with the nitrogen washout method for measuring functional residual capacity in normal subjects. J Clin Invest 35:322, 1956 3 Sandqvist L, Kjellmer I: Normal values for the single breath nitrogen elimination test in different age groups. Scand J Clin Lab Invest 12: 131, 1960 4 Fowler WS, Cornish ER jr, Kety SS: Lung function studies. Analysis of alveolar ventilation by pulmonary N2 clearance curves. J Clin Invest 31 :40, 1952 5 DuBois AB, Botelho SY, Comroe JH Jr: A new method for measuring airway resistance in man using a body plethysmograph: Values in normal subjects and in patients with respiratory disease. J Clin Invest 35:327, 1956
Since submission of this paper, I studied a patient with partial tracheal obstruction and almost complete obstruction of the left bronchus by carcinoma. Airway resistance was elevated five-fold above normal values and nitrogen clearance delay was normal at 12 breaths per minute, but prolonged at 26 breaths per minute. This test is affected by respiratory frequency when different time constants are present within the lung (unpublished data). Thus, false positive diagnoses by my criteria can occur in unilateral bronchial obstruction if the nitrogen washout test is measured at slow respiratory rates.
9 Miller RD, Hyatt RE: Obstructing lesions of the larynx and trachea: clinical and physiologic characteristics. Mayo Clinic Proc 44:161,1969
ACKNOWLEDGMENT: Dr. J. Landa performed the bronchoBberscopic examination and Dr. D. Fonseca referred two of the patients with tracheal stenosis to us.
10 Herzog H, Keller R, Allgower M: Special methods of diagnosing and treating obstructive diseases of the central airways. Chest 60:49, 1971
6 Bates DV, Boucot NG, Donner AE: The pulmonary diffusing capacity in normal subjects. J Physiol (Lond) 129:137,1955 7 Ogilvie CM, Foster RE, Blakemore WS, et al: A standardized breath holding technique for the clinical measurement of the diffusing capacity of the lung for carbon monoxide. J Clin Invest 36:1, 1957 8 Jordanoglou J, Pride NB: A comparison of maximum, inspiratory and expiratory flow in health and in lung disease. Thorax 23:38, 1958
Editorial Expression The increasing incidence of central airway obstruction by strictures from trauma, irritation of cuffed tubes, and neoplasms makes this report particularly timely. The physician seeing a patient with increasing dyspnea must consider major airway obstruction among the more common pulmonary and cardiac causes. Hearing a two-way stridor, observation of an unusual set of pulmonary function tests herein described, and timely endoscopy all may contribute to the identification of one of these unusual central airway lesions. The pulmonary function laboratory may trigger the correct diagnosis in the face of high airway resistance with relatively normal intrapulmonary mixing, or a peculiar How volume loop with a plateau in either or both the expiratory and inspiratory loop. The lack of reo CHEST, VOL. 62, NO.4, OCTOBER, 1972
sponse to bronchodilator described here does not, in itself, separate these unusual cases from up to one-third of patients with COPD who likewise do not demonstrate a measurable response to aerosol bronchodilator. The clinical lesson is to be aware of the increasing frequency of this type of problem with more frequent occurrence of vehicular trauma and aggressive resuscitation measures with tracheal intubation and tracheostomy. Use of pulmonary function tools of any of the variety mentioned above, and endoscopy, can localize the obstruction, and corrective measures may be dramatically effective in situations where tracheal narrowing can be lifethreatening. R. Drew Miller, M.D., F.C.C.P. Rochester, Minnesota
In seven patients with upper airway obstruction caused by tracheal or vocal cord lesions, pulmonary function tests revealed normal distribution of ventilation and a moderate to marked elevation in airway resistance unresponsive to bronchodilators. Such findings ought to be highly specific for this condition, a diagnosis which often is unsuspected cUnically.
As a cause of dyspnea and wheezing in the adult,
obstructive lesions of the larynx and trachea are rarely considered in such differential diagnoses as asthma, chronic bronchitis and emphysema. However, the strategic site of such lesions produces predictable abnormalities in pulmonary function which serve as a guide to definitive endoscopic or roentgenographic confirmation. Thus, one might expect a narrowed trachea to cause obstruction, but °From the Division of Pulmonary Diseases, Department of Internal Medicine, Mount Sinai Medical Center, Miami Beach, Florida. oOChief, Division of Pulmonary Diseases. Reprint requests: Dr. Sackner, Mt. Sinai Medical Center, 4300 Alton Road, Miami Beach 33140
not to create asynchronous emptying of air from the lungs during expiration as detected by tests of the distribution of ventilation because both lungs would be affected to the same degree. However, in obstructive lung diseases, significant lower airways obstruction would give rise to different degrees of obstruction throughout the lungs with attendant uneven distribution of ventilation (Fig 1). Simonsson and Malmberg! confirmed this hypothesis in two patients with tracheal stenosis who had marked reduction in FEV 1.0 and normal single breath nitrogen elimination curves. This article reports seven cases of upper airway obstruction which showed similar physiologic features. In these patients, markedly
A.
B.
FIGURE 1. The schematic figures represent the lungs - the trachea, the branching airways and the alveoli. A. Obstructive lung disease in which the degree of obstruction varies in different airways such that inspired air is not evenly distributed to the alveoli. B. Tracheal obstruction in which air is distributed evenly to the branching airways.
414
CHEST, VOL. 62, NO.4, OCTOBER, 1972
415
PHYSIOLOGIC FEATURES OF UPPER AIRWAY OBSTRUCTION Table I-Characteri.tic. 0/ Patient. with Upper AiTlClay Ob.'TUction. ClI8e Age
Sex
pulmonary function tests in upper airway obstruction. Lung volumes were variable from patient to patient. Tests of distribution of ventilation, the single breath nitrogen elimination curve and the pulmonary nitrogen clearance delay were normal. Maximum breathing capacity and FEV t .n were moderately to markedly reduced. Airway resistance was markedly elevated, ranging from 5 to 18 times the normal values. Diffusing capacity of the lung was normal in those patients measured. Arterial blood gas analysis showed mild hypoxemia in three patients, respiratory alkalosis in four patients and a combined respiratory acidosis and metabolic alkalosis in one patient. No significant change was noted in pulmonary mechanics after administration of bronchodilators.
Lesion
7l
F
Pedunculated polyp of vocal cords following endotracheal intubation
2
61
F
Lymphoma invading and compressing trachea
3
23
F
Squamous cell carcinoma of trachea
4
70
M
Squamous cell carcinoma of trachea
5
58
M
Tracheal stenosis following prolonged intubation and tracheostomy
6
72
F
Undifferentiated carcinoma of thyroid compressing trachea
7
76
M
Tracheal stenosis following tracheostomy of three days' duration
CASE SUMMARIES CASE
This 71-year-old woman was admitted to the hospital after taking an overdose of barbiturates. Endotracheal intubation and mechanical ventilation were required for two days and she was later discharged. She was readmitted two weeks later because of dyspnea, stridor and a croupy cough. Inspiratory and expiratory tracheal wheezing were present. Bronchofiberoscopy revealed a pedunculated polyp at the anterior commissure of the vocal cords. Passage beyond the polyp into the trachea was associated with extreme dyspnea and the instrument was immediately withdrawn. Granulomatous tissue of the vocal cords was removed under direct laryngoscopy with a good clinical result.
elevated values for airway resistance made the dichotomy between the magnitude of obstruction and the normal distribution of ventilation even more striking. METHODS
Displaceable lung volumes were measured with a spirometer. Functional residual capacity was determined by a body plethysmographic technique.s Tests of distribution of ventilation included a single breath nitrogen elimination test3 and a nitrogen washout test with graphic analysis of the washout curve to calculate pulmonary nitrogen clearance delay.! Airway resistance was obtained during panting at one to two cycles per second between 0.25 liter per second inspiratory and expiratory How rate, by the body plethysmographic teehnique.s Diffusing capacity of the lung for carbon monoxide was determined by steady state6 and single breath methods." Arterial blood gases and pH were determined with an Instrumentation Laboratory pH blood gas analyzer. UPPER
Amw AY
I
CASE
2
This 61-year-old woman was admitted to the hospital because of increasing dyspnea of six months' duration. Ten days prior to admission, she developed wheezing, stridor and an uncomfortable sensation in her throat. Bronchoscopy revealed a subglottic bulging which narrowed this region to a small slit. Biopsy of this region was consistent with lymphoma. Bone marrow examination was consistent with chronic lymphatic leukemia. CASE
OBSTRUCTION
3
This 23-year-old woman was hospitalized elsewhere six months prior to admission to our hospital. At that time,
Table I lists the patient characteristics and Table 2 the
Table 2-Pulmonary Function Ted. in Upper AiTlClay Ob,'ruction.* Case VC liters RV liters TLC liters RV/TLC% SBN, % Pulm N, clearance delay % MBC liters/min FEV l.I liters Airway resistance cmH,O/liters/sec Deoss ml/mm Hg x min DeoSB ml/mm Hg x min PO,mm Hg Pco, mm Hg pH units B.E. mEq/liters
2 1.65 1.55 3.15 49
(86)
(Ill)
(95) (117)
88 ( < 1(0)
2.25 1.74 3.99 44 2.0
(78) (105) (88) (119) «2.5)
3.15 0.77 3.92 20 1.6
(88) (58) (SO) (74) «2.5)
17 (35) .84 (63) 17.7 (1053)
30 (45) 1.59 (64) 8.9 (594)
51 (52) 2.20 (65) 9.6 (589)
10.9 (160)
12.6 (129)
21.8 (120) 19.9 (77)
79 24 7.54 0
86
36 7.40 -2
4
3
68
42 7.43 +3
1.07 1.90 2.98 64
(38) (94) (62) (152)
53 ( < 1(0)
5 3.04 4.78 7.92 61 1.6 43
(75) (206) (123) (169) «3.5) ( < 1(0)
15 (23) .47 (20) 22.0 (1667)
23 (24) 1.39 (43) 10.6 (1831)
55 50 7.47 +10
10.5 (90) 28.1 (117) 64 23 7.55 0
6 1.95 2.26 4.21 54 2.2
(90) (155) (116) (135) «3.5)
28 (54) 1.03 (68) 6.5 (501) 9.8 (140) 86 30 7.48 0
7 3.17 2.59 5.76 45 1.5 46
(102) (119) (l09) (110) «3.5) «100)
42 (60) 1.56 (61) 4.1 (469) 24.3 (149) 83 32 7.46 0
*Values within parentheses indicate percent of predicted normal except for tests of distribution where highest normal value is listed.
CHEST, VOL. 62, NO.4, OCTOBER, 1972
416
MARVIN A. SACKNER
she had an enlarged thyroid which compressed the trachea. A thyroidectomy was carried out and squamous cell carcinoma was found within the gland. Postoperatively, a tracheostomy was left in situ for two months. Two months following decannulation, she noted dyspnea and a feeling of obstruction to breathing low in her throat but denied wheezing. Physical examination at our hospital revealed tracheal wheezing during forced inspiration and expiration. Bronchofiberscopy revealed narrowing of the trachea in its midportion to about 6 mm in diameter. The neck was reexplored and squamous cell carcinoma was found within the trachea, neck and mediastinum. The patient died eight months later with an inoperable stenosis of the thoracic portion of the trachea. CASE
4
This 70-year-old man was admitted to our hospital for evaluation of dyspnea and stridor of one year's duration. He had a ten-year history of pulmonary lymphoma which was treated with three courses of cobalt radiotherapy to the mediastinum and lung fields. Recurrent pleural effusions required multiple thoracenteses. The physical appearance of his neck suggested a superior vena cava syndrome. He was extremely hoarse and could speak only with a whisper. A tracheal wheeze was present during both quiet inspiration and expiration. Bronchofiberoscopy revealed a large multinodular fleshy tumor in the cervical trachea. The tracheal lumen through this tumor was only a few millimeters in diameter. A minimal resection of the tumor was carried out under direct bronchoscopy because of a great deal of bleeding. Endotracheal intubation for four days was necessary until the edema around the tumor subsided. The biopsy was consistent with an undifferentiated squamous cell carcinoma. He was given a course of cyclophosphamide and improved. Pulmonary function tests repeated two months following surgery revealed an increase in VC to 1.46 liters, MBC to 30 liters per minute and FEV1 .0 to 1.02 liters. The airway resistance dropped from 22.0 cm H20 per liters per second ( 1667 percent of predicted normal) to 5.9 em H20 per liters per second (268 percent of predicted normal). CASES
This 58-year-old man was admitted to the hospital with a right lower lobe pneumonia and congestive heart failure. On the day following admission, he suffered a cardiac arrest and required endotracheal intubation. He was intubated for four days and then tracheostomized. Continuous mechanical ventilation for three weeks was necessary for respiratory failure. He developed renal shutdown which required multiple dialyses. Six weeks after admission, the tracheostomy tube was removed. Three weeks later, he developed increasing dyspnea and wheezing. Physical examination revealed a tracheal wheeze and bronchofiberscopy showed marked tracheal stenosis at the tracheostomy site. The lumen was estimated at approximately 6 to 7 mm in diameter. After bougie dilatation the airway resistance fell from 10.6 cm H20 per liters per second (1831 percent predicted normal) to 9.4 cm H20 per liters per second (1382 percent predicted normal). CASE
6
This 72-year-old woman was admitted because of pain in the throat and a nonproductive cough of one week's duration. Wheezing was present over the trachea; it was also transmitted to the chest. An enlarged thyroid gland was present.
Chest roentgenogram revealed a large mediastinal mass which upon radioisotopic scanning was indicative of thyroid tissue. An incisional biopsy revealed an undifferentiated carcinoma of the thyroid gland. CASE
7
This 76-year-old man with carcinoma of the tongue underwent hemiglossectomy along with an elective tracheostomy. The latter was terminated after three days. Two weeks following surgery, he noticed dyspnea and noisy breathing. This progressed in severity and he was admitted two months later for evaluation. A tracheal wheeze was heard during forced inspiration and expiration. Bronchoflberscopic cine revealed an edematous subglottic membrane which reduced the tracheal lumen to about 20 percent of the original area. Pulmonary function tests revealed an elevation in airway resivtance to 469 percent of predicted normal. He was placed upon prednisone 60 mg a day and had marked subjective improvement within six days. No wheeze could be heard on auscultation over the trachea. Airway resistance fell to within normal limits of 1.2 cm H20 per liters per second (148 percent predicted normal) and bronchoflberscopic cine revealed shrinkage of the subglottic membrane such that the lumen was reduced to about 40 percent of its original area. DISCUSSION
The present study confirms the work of Simonsson and Malmberg! who pointed out that tracheal obstruction is associated with a normal distribution of ventilation and reduced FEV 1.0. Airway resistance in our cases was moderately to markedly elevated and made the dichotomy between the severe obstruction to air How and the normal distribution of ventilation even more striking. As a further test of fixed upper airway obstruction, there was no improvement of airway resistance after administration of bronchodilators. Other tests of pulmonary function have been advocated to detect upper airway obstruction. Thus, the ratio of peak expiratory to inspiratory Howat the midvolume point of the vital capacity is said to be unity in fixed tracheal obstruction, whereas this ratio will be less than unity in chronic obstructive pulmonary diseases.v" However, if there is an inconstant upper airway obstruction, the location becomes important because of transmural pressure gradients. The extrathoracic lesion causes slowing predominantly in inspiration and the intrathoracic lesion causes slowing predominantly in expiration. These transmural gradients only become significant during forced ventilatory maneuvers when there are large swings in transpulmonary pressure. The How rate over which airway resistance was calculated in the present study was low, ie, between 0.25 liters per second inspiratory and expiratory How. Thus, airway resistance estimated under these circumstances would be relatively insensitive to inconstant upper airway obstructions. For example, in emphysema, a CHEST, VOL. 62, NO.4, OCTOBER, 1972
PHYSIOLOGIC FEATURES OF UPPER AIRWAY OBSTRUCTION
marked reduction in FEV 1.0 is associated with a normal or slightly elevated expiratory airway resistance at these low How rates.'? Furthermore, in such patients who have tracheobronchial collapse during forced expiration, the inspiratory airway resistance is normal, The spotty nature of the destruction and dilatation of the acinus in emphysema produces uneven distribution of ventilation. In contrast to such findings, patients with fixed tracheal obstructions show an increase in airway resistance over both the inspiratory and expiratory phases of respiration even at low How rates and distribution of ventilation is normal. False positive diagnoses ought not to occur but if coexistent obstructive or restrictive lung diseases are present, then distribution of ventilation might be uneven. ADDENDUM
417 !U:FERENCES
Simonsson BG, Malmberg R: Differentiation between localized and generalized airway obstruction. Thorax 19:416, 1964 2 DuBois AB, Botelho SY, Bedell GN, et al: A rapid plethysmographic method for measuring thoracic gas volume: A comparison with the nitrogen washout method for measuring functional residual capacity in normal subjects. J Clin Invest 35:322, 1956 3 Sandqvist L, Kjellmer I: Normal values for the single breath nitrogen elimination test in different age groups. Scand J Clin Lab Invest 12: 131, 1960 4 Fowler WS, Cornish ER jr, Kety SS: Lung function studies. Analysis of alveolar ventilation by pulmonary N2 clearance curves. J Clin Invest 31 :40, 1952 5 DuBois AB, Botelho SY, Comroe JH Jr: A new method for measuring airway resistance in man using a body plethysmograph: Values in normal subjects and in patients with respiratory disease. J Clin Invest 35:327, 1956
Since submission of this paper, I studied a patient with partial tracheal obstruction and almost complete obstruction of the left bronchus by carcinoma. Airway resistance was elevated five-fold above normal values and nitrogen clearance delay was normal at 12 breaths per minute, but prolonged at 26 breaths per minute. This test is affected by respiratory frequency when different time constants are present within the lung (unpublished data). Thus, false positive diagnoses by my criteria can occur in unilateral bronchial obstruction if the nitrogen washout test is measured at slow respiratory rates.
9 Miller RD, Hyatt RE: Obstructing lesions of the larynx and trachea: clinical and physiologic characteristics. Mayo Clinic Proc 44:161,1969
ACKNOWLEDGMENT: Dr. J. Landa performed the bronchoBberscopic examination and Dr. D. Fonseca referred two of the patients with tracheal stenosis to us.
10 Herzog H, Keller R, Allgower M: Special methods of diagnosing and treating obstructive diseases of the central airways. Chest 60:49, 1971
6 Bates DV, Boucot NG, Donner AE: The pulmonary diffusing capacity in normal subjects. J Physiol (Lond) 129:137,1955 7 Ogilvie CM, Foster RE, Blakemore WS, et al: A standardized breath holding technique for the clinical measurement of the diffusing capacity of the lung for carbon monoxide. J Clin Invest 36:1, 1957 8 Jordanoglou J, Pride NB: A comparison of maximum, inspiratory and expiratory flow in health and in lung disease. Thorax 23:38, 1958
Editorial Expression The increasing incidence of central airway obstruction by strictures from trauma, irritation of cuffed tubes, and neoplasms makes this report particularly timely. The physician seeing a patient with increasing dyspnea must consider major airway obstruction among the more common pulmonary and cardiac causes. Hearing a two-way stridor, observation of an unusual set of pulmonary function tests herein described, and timely endoscopy all may contribute to the identification of one of these unusual central airway lesions. The pulmonary function laboratory may trigger the correct diagnosis in the face of high airway resistance with relatively normal intrapulmonary mixing, or a peculiar How volume loop with a plateau in either or both the expiratory and inspiratory loop. The lack of reo CHEST, VOL. 62, NO.4, OCTOBER, 1972
sponse to bronchodilator described here does not, in itself, separate these unusual cases from up to one-third of patients with COPD who likewise do not demonstrate a measurable response to aerosol bronchodilator. The clinical lesson is to be aware of the increasing frequency of this type of problem with more frequent occurrence of vehicular trauma and aggressive resuscitation measures with tracheal intubation and tracheostomy. Use of pulmonary function tools of any of the variety mentioned above, and endoscopy, can localize the obstruction, and corrective measures may be dramatically effective in situations where tracheal narrowing can be lifethreatening. R. Drew Miller, M.D., F.C.C.P. Rochester, Minnesota