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The Diversity of the Effects of Sulfur Mustard Gas Inhalation on Respiratory System 10 Years After a Single, Heavy Exposure
The Diversity of the Effects of Sulfur Mustard Gas Inhalation on Respiratory System 10 Years After a Single, Heavy Exposure* Analysis of 197 Cases Ali Emad, MD; and Gholam Reza Rezaian, MD Objective: To find out the late pulmonary sequelae of sulfur mustard gas inhalation in 197 veterans, 10 years after their exposure. Design: Cross-sectional clinical study. Setting: University hospital. Patients: One hundred ninety-seven veterans with a single, heavy exposure to sulfur mustard gas in 1986 and 86 nonexposed veterans as their control group. Interventions: Pulmonary function tests, carbon monoxide diffusion capacity, bronchoscopy, and high-resolution CT of the chest were performed in all patients. Trans bronchial lung biopsy was done in 24 suspected cases of pulmonary fibrosis. Results: Asthma was diagnosed in 21 (10.65%), chronic bronchitis in 116 (58.88%), bronchiectasis in 17 (8.62%), airway narrowing due to scaring or granulation tissue in 19 (9.64%), and pulmonary fibrosis in 24 (12.18%) cases. None of these were found among the control group except for a single case of chronic bronchitis. Conclusion: Although the respiratory symptoms of an acute sulfur mustard gas inhalation are usually transient and nonspecific, it can lead to the development of a series of chronic destructive pulmonary sequelae in such cases. (CHEST 1997; 112:734-38) Key words: asthma; bronchiectas is; chronic bronchitis; mustard gas; pulmonary fibrosis Abbreviations: Dco=carbon monoxi de diffusion capacity; HRCT= high-resolution CT; PEF=peak expiratory flow; PFTs = pulmonary function tests
s
ulfur mustard gas is an alkylating agent that is seriously toxic to the skin, eyes, and respiratory tract. 1·2 Unfortunately, it has been used as a vesicant chemical warfare agent in the past and recently in the Iran-Iraq war.3-5 The upper and lower respiratory tracts may be acutely damaged after its inhalation ,6 -9 and subsequently, a variety of chronic pulmonary sequelae may develop.l 0 Since the available literature is quite scanty in this regard, herein we present the chronic sequelae of sulfur mustard exposure after an acute and massive inhalation of this gas by a group of Iranian veterans in 1986.
*From the Department of Internal Medicine, Division of Respiratory Diseases, Shiraz University of Medical Sciences, Shiraz, Iran. Manuscript received August 23, 1996; revision accepted March 12, 1997. Reprint requests: Ali Emad, MD , PO Box 71345-1 674, Shiraz University of Medical Sciences, Shiraz, Iran 734
MATERIALS AND METHODS
Those patients with respiratory symptoms whose exposure to mustard gas had been confirmed b y studies on their urine and vesicular fluid (using the methods advocated by Heyndrickx et al 11 ) in a special toxicology laborat01y in 1986 were included. All these patients had their initial admissions in our university hospitals in 1986 because of the acute respiratory symptoms that included rhinonhea, sore throat, hoarseness, cough, chest tightness, and dyspnea. Patients were included only if they had no history of exposure to other environmental agents known to cause interstitial lung disease or extrinsic allergic alveolitis. In the interim (1986 to 1996), all patients had regular follow-ups in a s pecial outpatient clinic designed for these chemically injured vet erans. Jobs such as painting, woodworking, welding, farming, milling, sculpturing, fire fighting, and baking were not allowed. Home visits and inspection of workplace were regularly done and all subjects were instructed to avoid exposure to asbestos, coal dust, silicone, or cotton dust. None of the patients worked in petroleum industries. Subjects with known asthma (before their exposure to sulfur mustard gas ) (n=O), cigarette smokers (n=9), and those with proven cardiovascular disease (n=3) or other systemic illness (n=3) were excluded from the study. One hundred ninety-seven patients fulfill ed the above cJ;teria and were enrolled into the study. In addition, 84 nonsmoker veterans who had participate d in the war in another region in the Clinical Investigations
same year (1986) but had no exposure to the mustard gas were voluntarily entered into the study as our control group.
Study Design All subjects signed an informed written consent. Each patient was carefully examined. All patients had an ECG, a chest radiograph, and high-resolution CT (1-IRCT ) of the chest. All HRCTs were performed with l.O- or 1.5-mm-thick sections taken at 1-cm intervals throughout the entire thorax. Pulmona1y function tests (PFTs) were measured through spirometric assessment. An experienced physician did all spirometric measurements for all the subjects usi ng a spirometer (F UDAC .50; Fukuda Sangyo Co LTD; Chiba, Japan). Each patient was trained to give his best effort. After 15 min of resting, three spirometric measurements were done at 1-min intervals; th e highes t values were chosen and repmt ed. Each patient underwent a bronchodilator study by a standard dose of inhaled (3 2 -agonist as well, 12 and all tests were repeated again 15 to 20 min later. Reversibility of FEV1 was calculated by the following formula: (FEV1 after - FEV 1 before)/ FEV1 before. 12 The carbon monoxide diffusion capacity (Dco) was also measured for each patient. Treatment with inhaled (3 2 -agonist or inhaled ipratropium bromide was withdrawn for 8 h, and also treatment with anticholinergic agents, sodium cromoglycate, antihistamines, beclomethasone inhaler, and theophylline was discontinued 2 days prior to each patient's examination and his PFTs. All patients unde1went bronchoscopic examinations under appropriate and recommended precautions especially for asthmatic patients.J-3 The upper respiratory tract was anesthetized by 2% lidocaine. Atropine (0.75 mg IM ) was given before the procedure. Patients who were labeled as being asthmatic or having severe chronic bronchitis received a continuous infusion of aminophylline, 0.6 mglkglh, which was continued for 2 h after the termination of the procedure. Bronchial biopsy was done in all cases. Transbronchial lung biopsy was performed for only 24 patients whose spirometric data, chest radiographs, and HRCT of the chest14 were suggestive of interstitial lung disease. Biopsy specimens were obtained from all three lobes on the right side or from upper and lower lobes of the left lung.
Patients With Chronic Bronchitis Chronic bronchitis was defined when the following criteria were present: (1) no evidence of airway narrowing, stricture, or obstruction due to granulation tissue on bronchoscopy; (2) no evidence of bronchiectasis in the HRCT scan of the chest; (3) history of cough and sputum production for at least 3 mo/yr for 2:2 years; and (4) an obstructive pattern in th e results of spirometry. 18 The severity of chronic bronchitis was based on the values of patients' FEV 1 . 19 Mild COPD was defined as an FEV1 ::o:50% of predicted, moderate as FEV1 35 to 49% of predicted, and severe type as FEV1 <35% of predicted.
Patients With Pulnwnary Fibrosis Pulmonary fibrosis was considered to be present when all the following criteria were met: (1) a estrictive r pattern in the spirometric data; (2) decreased single-breath D co ; and (3) the lung biopsy specimen showing evidence of interstitial pneumonitis with varying degrees of interstitial fibrosis without evidence of granuloma formation. All transbronchiallung biopsy specimens were seen and interpreted b yan expert pathologist who had no information about the patients' clinical or paraclinical data. Individual slides of the lung biopsy specimens were stained with hematoxylin-eosin and Masson trichrome. The degree of fibrosis was given an estimate as compared to a normal lung specimen. Fibrosis was estimated to be mild, moderate, or severe when there was <25%, 25 to 40%, or >40% increase in the amount of visualized collagen.
Patients With Bronchiectasis The diagnosis of bronchiectasis was made according to the typical radiologic and HRCT findings. 20
Control Group The prerequisites for participation in the study were the same as tbose of the gas-exposed vete rans. All had a complete histmy and physical examination. In addition, a chest radiograph and an ECG were obtained and PFTs were measured in all of tbem .
Statistics Asthmatic Patients Patients were provisionally labeled as having asthma when they met at least two of the following three criteria: (1) typical history of attacks of breathlessness, wheezing, or both, nocturnal cough, chest tightness either spontaneously or triggered by exercise, respiratory infections, or irritants; (2) reversibility in FEVv defined as ([ FEV 1 after- FEV, before]/FEV1 before)> 15% after a standard dose of inhaled (3 2 -agonist;12 and (3) diurnal variability in peak expiratory flow (PEF ) rate >20%, calculated from the following formula: (highest PEF-lowest PEF)/highest PEF.L3 · 16 A patient was finally labeled as having asthma when bronchoscopy failed to show evidence of any upper or lower airway narrowing or obstruction due to granulation tissue or stricture form ation. The severity of asthma was determined by taking history, performing physical examination, the medications used, and the results of PFTs. Mild asthma was defin ed when the patients used only intermittent inhaled short-acting (3 2 -agonist as needed, and had a PEF 2:80% predicted valueP Moderate to severe asthma was defined when the patients needed daily inhaled anti-inflammatory agents or possible daily long-acting bronchodilator, and had a PEF :580% predicted value and a PEF variability of 2:30%.1'
All results are mean ±SD unless othervvise indicated. The two methods of x2 and Spearman were used for analysis of data. Spearman rank test was pe rformed to find out the correlation between the patient's age and th e type or severity of the pulmonary sequelae. Spearman rank correlation was also used to compare the degree of fibrosis with the age, percent FEV v percent FVC, and percent Dco because fibrosis was ranked from mild ( + 1)to moderate ( +2) and all other data were either continuous or ranked. In addition, because we had only one patient with severe degree of the fibrosis ( +3), this patient was not considered in the Spearman rank correlation.
RESULTS
The age range of the patients was 27 to 65 years (mean=34.39±5.95 years ) and that of the control group was 32 to 48 years (mean=35.52±3.97 years) (p=O.ll). Asthma was diagnosed in 21 (10.65%), chronic bronchitis in 116 (58.88%), and pulmonary fibrosis was seen in 24 (12.18%) patients. CHEST I 112 I 3 I SEPTEMBER, 1997
735
Table l-Mean Age and PFTs in 21 Patients With Asthma, 10 Years After Exposure to Sulfur Mustard Gas FEY1 , L
FYC, L
PEF Rate, Lis
Asthma
Age, yr
Observed
% of Predicted
Observed
% of Predicted
Observed
% of Predicted
Mild (n=6) Moderate to severe (n=15)
27.33::+::0.51 32.13::+::4.94
2.73::+::0.12 2.20::+::0.23
83.51::+::3.06 64.20::+::7.95
3.43::+::0.10 3.06::+::0.12
81.05::+::2.78 70.86::+::3.03
7.05::+::0.24 4.85::+::0.48
85.27::+::3.83 56.73::+::6.16
Table 2-The Mean Age and PFTs in 116 Patients With Chronic Bronchitis, 10 Years After a Single Heavy Exposure to Sulfur Mustard Gas FEY1 , L Chronic Bronchitis Mild (n = 27) Moderate (n=53) Severe (n=36)
PEF Rate, Us
FYC, L
Age, yr
Observed
% of Predicted
Obse1ved
% of Predicted
Observed
% of Predicted
36.51 ::+::9.63 35.26::+::6.04 35.36::+::2.99
2.23::+::0.14 1.45::+::0.17 1.19::+::0.05
68.98::+::5.07 47.49::+::2.20 33.01::+::1.54
3.51 ::+::0.28 2.49::+::0.28 2.43::+::0.28
70.03::+::4.49 51.79::+::2.96 43.57::+::2.72
6.00::+::0.91 4.57::+::0.39 2.40::+::0.30
67.80::+::8.24 49.11::+::6.61 30.60::+::3.71
Table 3-The Mean Age and PFTs in 17 Patients With Bronchiectasis and 19 Patients With Airway Stricture or Narrowing, 10 Years After Their Exposure to Sulfur Mustard Gas FEY, L Age, yr 32.94::+::1.71 Bronchiectasis (n=17) Airway stricture or 35.94::+::7.36 narrowing (n=19)
FYC, L
PEF Rate, Us
Observed
% of Predicted
Observed
% of Predicted
FEY/FYC,% Observed
2.22::+::0.30
65.75::+::10.6
3.01::+::0.15
70.52::+::3.73
73.59::+::8.47
5.13::+::0.75
60.97::+::9.78
1.96::+::0.26
56.90::+::8.10
2.83::+::0.26
66.33::+::5.62
67.91::+::10.56
4.58::+::0.57
54.57::+::7.41
Observed
% of Predicted
Asthmatic Patients
Patients With Bronchiectasis or Airway Stricture
There was only a significant difference between the age of the patients with asthma (mean=30.76±4.7 years) and those with chronic bronchitis (mean=35.48±6.3 years) (p=0.001). The results of FEVto FVC, FEV/FVC, and PEF rate in patients with asthma are shown in Table 1. Six asthmatic patients were classified as having mild asthma while the rest suffered from a moderate to a severe disease. There was a significant correlation between the age of the patients and the severity of asthma (r=0.67, p=0.002).
Diffuse bronchiectasis was seen in 17 patients (8.62%), and airway stricture or narrowing due to scaring or granulation tissue was detected in 19 patients (9.64%). Of these, seven were found in the trachea, eight in the main bronchi, and four in one or more of the lobar bronchi. Their ages and PFTs are shown in Table 3.
Patients With Chronic Bronchitis Mild, moderate, and severe chronic bronchitis was diagnosed in 27, 53, and 36 veterans, respectively (Table 2) . All 36 patients with severe bronchitis had dyspnea at rest and were dependent on long-term oxygen therapy with a mean of 37.75±10.99 months. One of these patients died of acute myocardial infarction soon after the termination of the study. There was no significant correlation between the patient's age and the severity of bronchitis (r=0.16, p=0.07). 736
Patients With Pulmonary Fibrosis The PFTs and degree of fibrosis in patients with pulmonary fibrosis are shown in Table 4. Twelve patients (50%) had mild fibrosis. Eleven patients (45.83%) had moderate pulmonary fibrosis, and only one patient (4.16%) had severe fibrosis. Alveolar septal fibrosis was a prominent finding in most of the patients (62.5%). Diffuse fibrosis was seen in only three patients (12.5%). Neither honeycomb formation nor granulation tissue or granuloma was seen in any of the biopsy specimens. Comparisons between the degree of fibrosis and the physiologic parameters of PFT and percent Dco are shown in Table 5. Of these, only the percentage of Dco showed a significant correlation with the degree of fibrosis . Clinical Investigations
Table 4-The Mean Age and PFTs in 24 Patients With Pulmonary Fibrosis, 10 Years After a Single Heavy Exposure to Sulfur Mustard Gas FVC, L
FEY 1, L Pulmonary Fibrosis Mild (n=12) Moderate (n =ll ) Severe (n =1)
Age, yr
Observed
% of Predicted
Obse rved
% o f Predicted
Dco,% of Predicted
32.58::!::3.63 31.09::!:: 1.22 38.00
3.02 ::!:: 0.34 2.79 ::!:: 0.32 2.94
82.43::!::3.48 81.84::!::3.67 81.83
3.45::!:: 0.37 3.39::!::0.25 2.65
65.34::!::7.02 55.53::!::6.97 50.00
69.08::!::6.52 51.45::!::8.29 21.00
Table 5-The Correlation Between the Degree of Fibrosis With the Age and PFTs of 24 Patients With Pulmonary Fibrosis* Degree of Fibrosis
Disease Categ01y p
Age, yr FYC, % FEY~> %
Dco,%
- 0.12 -0.39 - 0.68 -0.76
Table 6-The Correlation Between the Age and Severity of Disease in Each Individual Diagnostic Group of Gas-Exposed Veterans *
0.56 0.06 0.75 0.0003
*Spearman rank correlation was used for all comparisons.
The correlation between the age and severity of disease in each individual diagnostic group is shown in Table 6.
Control Group The FEV1 values ranged from 2.22 to 3.49 L (mean =3.14 ±0.33 L). The FVC and PEF rate ranged from 3.21 to 4.45 L (mean=4.27 ±0.14 L) and from 5.33 to 9.01 Us (mean=8.43±0.42 Us) , respectively. None of the subjects in the control group had any pulmonary disorder except one patient (age, 48 years old) who had mild chronic bronchitis with an FEV 1 of 54% of predicted value.
DISCUSSION
The vesicant effect of sulfur mustard has been known since early in this century. Despite the available international treaty on the banning of the use of chemical and biological agents in warfare,21 these agents were used heavily during the Iran-Iraq war in the 1980s.5·22 This gas is lipophilic. Tissues exposed to adequate concentration of this chemical agent undergo DNA alkylation, which can lead to the cell death.23 Sulfur mustard is also selective in its accumulation in fat tissue. The organs that are more prone to the acute effects of exposure to sulfur mustard gas are skin, eyes, upper and lower respiratory tracts, and sometimes the GI tract.3 In an acute heavy exposure to sulfur mustard gas, the columnar cells of the epithelial lining of the upper respiratory tract may shed. 6 This may also be
Asthma 1 Chronic bronchitis'
Pulmon ary fibrosi s§
Seve rity
Age, yr, mean ::t: SD
Mild Moderate-severe Mild Mode rate Severe Mild Mode rate
27.33::!::0.51 32.13::!::4.94 36.5l:t9.63 35.26::!::6.04 35.36::!::2.99 32.58::!::3.63 31.09::!:: 1.22
*Spearman rank corre lation was used for all comparisons. 1r=0. 67, p = 0.002. 1r=0.16, p=0.07. l r=-0.12, p=0.56.
accompanied by peribronchial edema, hyperemia of the blood vessels, cellular infiltrations in the submucosa, and intense vacuolization and disorganization of cytoplasmic and nuclear stmctures. 6·7·24 Pulmonary hemorrhage, pulmonary edema,25 and respiratory failure with a picture similar to ARDS may occur. These cytotoxic effects of sulfur mustard gas associated with the acute thermal injury sustained by the airway mucosa may le ad to the scarring and development of stenosis of the tracheobronchial tree, 26 as was seen in 19 (9.64%) of our patients. Recurrent infections are relatively common in the subacute and chronic phases of the lung involvement.27 This, accompanied by the loss of normal ciliary activity and airway obstruction, may lead to the development of bronchiectasis, which was seen in 17 (8.62%) of our patients. The incidence of asthma as a late sequela of pulmonary effects of sulfur mustard gas exposure was about 10.65% in this series of patients. This airway hyperreactivity may be induced by its cytotoxic effect .6·28 Chronic bronchitis is a well-known late complication of sulfur mustard gas inhalation in humans. 10 With an incidence of 58.88%, it was the most common pulmonary sequela in our patients. It was the cause of marked disability in all 36 patients with severe diseases and the only fatality was in this group of patients. There seemed to be apositive correlation between CHEST I 112 I 3 I SEPTEMBER, 1997
737
the age of the gas-exposed veterans to the severity of asthma and development of chronic bronchitis. That is, the older subjects had a higher chance of having a more severe form of asthma and a higher chance of developing chronic bronchitis. Pulmonary fibrosis as documented by spirometric studies and lung biopsy specimens was seen in 24 patients (12.18%). This relatively low incidence is probably because of the fact that most of the mustard gas is absorbed in the upper airways, producing more of an airway disease, and little reaches the alveoli, thus sparing the lung tissue from its devastating effects. Although physiologic parameters of the lungs are generally used to assess and monitor patients with pulmonary fibrosis, in comparison to the significant correlates with the degree of fibrosis, only percent Dco correlated well with the degree of pulmonary fibrosis in our veterans. Therefore, the percentage of Dco can be used as an objective monitor of the degree of fibrosis and also as a good predictor of prognosis in our gas-exposed patients with pulmonary fibrosis. Although lung cancer has been reported as a late complication of mustard gas inhalation, 29 •30 we have found no bronchial carcinoma or other lung malignancies in these veterans by now (after 10 years). Further follow-ups are needed for the assessment of the carcinogenic effect of this gas on the pulmonary system.
REFERENCES 1 Ludlum DB, Austin-Ritchie P, Hagopian M, et al. Detection of sulfur mustard-induced DNA modifications. Chern Biol Interact 1994; 91:39-49 2 Ashkenazi I, Blumenthal M, Avni I, eta!. Mustard gas injuries of the eyes. Harefuah 1991; 120:279-83 3 Somani SM , Babu SR. Toxicodynamics of sulfur mustard. Int J Clin Pharmacal Ther Toxicol 1989; 27:419-35 4 Worwser U. Toxicology of mustard gas. Trends Pharmacal Sci 1991; 12:164-67 5 Report of specialists appointed by the Secretary General to investigate allegations by the Islamic Republic of Iran concerning the use of chemical weapons. New York: Security Council of the United Nations document S/16433, 1986 6 Calvet JH, Jarreau PH, Levame M, etal. Acute and chronic respiratory effects of sulfur mustard intoxication in guinea pig. J Appl Physiol1994; 76:681-88 7 Chevillard M, Lainee P, Robineau P, et al. Toxic effects of sulfur mustard on respiratory epithelial cells in culture. Cell Bioi Toxicol 1992; 8:171-81 8 lwaszkiewicz J. Burns of the upper respiratory tract caused by mustard gas. Pol Med J 1966; 5:706-09 9 Szarejko R. Changes induced by mustard gas in the upper respiratory airways and an attempt at treating them in rats. Otolaryngol Pol1974; 28:617-18 10 Winte mitz W. Chronic lesions of the respiratory tract initi-
738
ated by inhalation of irritant gases. JAMA 1919; 73:689 11 Heyndrickx A, De Puydt H, Cordonnier J. Comparative study of two different field tests for the detection of yperite in the atmosphere, applied on biological samples of gassed soldiers. Proc First World Cong Bioi Chem Warfare, Ghent, Belgium , May 21-23, 1984; 61-68 12 Ries AK. Response to bronchodilators. In: Clausen JL, ed. Pulmonmy function testing: guidelines and controversies. New York: Academic Press, 1982; 215-21 13 Bensein IL, Boushey HA, Cherniack RM , eta!. Summary and recommendations of a workshop on the investigative use of fib eroptic bronchoscopy and bronchoalveolar lavage in asthmatic patients. Chest 1985; 88:136-38 14 Webb WR. High resolution lung computed tomography: normal anatomic and pathologic findings. Radio! Clin North Am 1991; 29:1051-63 15 Quackenboss JJ, Lebowitz MD , Krzyzanowski M. The normal range of diurnal changes in peak expiratory flow rates: relationship to symptoms and respiratory diseases. Am Rev Respir Dis 1991; 143:323-30 16 Clark TJ, Hetzel MR. Diurnal variation of asthma. Br J Dis Chest 1977; 71:87-92 17 Inte rnational consensus report on diagnosis and treatment of asthma. Eur Respir J 1992; 5:601-41 18 American Thoracic Society. Standards for the diagnosis and care of patients with chronic obstructive pulmonary disease (COPD) and asthma. Am Rev Respir Dis 1987; 136:225-44 19 Standards for the diagnosis and care of patients \vith chronic obstructive pulmonary disease. Am J Respir Crit Care Med 1995; 152:S77-S120 20 Aronchick JM, Miller \VT. Bronchiectasis. J Thorac Imaging 1995; 10:255-67 21 Geneva protocol, 1925. Prohibition of the use in war of asphyxiating poisonous or other gases, and of bacteriological method of warfare. New York: United Nations, 1925 22 Budiansky S. Chemical weapons: United Nations accuses Iraq of military use [news]. Nature 1984; 308:483 23 Ludlum DB, Papinneister B. DNA modification by sulfur mustards and nitrosureas and repair of these lesions. In: Ludlum DB, ed. Mechanisms of DNA damage and repair. New York: Plenum Publishing, 1986; 119-45 24 Pappenheimer AM. Pathological action of war gases. In: Weed FW, ed. The Medical Department of the United States Army in the World War, (vol XIV): medical aspects of gas warfare, Washington, DC: US Government Printing Office, 1926, 87-249 25 Vedder EB. The medical aspects of chemical warfare. Baltimore: Williams & Wilkins, 1925 26 Freitag L, Firusian , Stamatis G, et al. The role of bronchoscopy in pulmonary complications due to mustard gas inhalation. Chest 1991; 100:1436-41 27 Willems JL. Clinical management of mustard gas casualties. Ann Med Milit Belg 1989; 3:S1-S61 28 Gilchrist HL, Matz PB. The residual effects of warfare gases: I. Chlorine; II. Mustard. Washington, DC: US Government Printing Office, 1933 29 Wada S, Mivanishi M, Nishimoto Y, et al. Mustard gas as a cause of respiratory neoplasms in man. Lancet 1968; 1:1161-63 30 Beebe GW. Lung cancer in World War I veterans: possible relation to mustard-gas injury and 1918 influenza epidemic. J Nat! Cancer Inst 1960; 25:1231-51
Clinical Investigations
s
ulfur mustard gas is an alkylating agent that is seriously toxic to the skin, eyes, and respiratory tract. 1·2 Unfortunately, it has been used as a vesicant chemical warfare agent in the past and recently in the Iran-Iraq war.3-5 The upper and lower respiratory tracts may be acutely damaged after its inhalation ,6 -9 and subsequently, a variety of chronic pulmonary sequelae may develop.l 0 Since the available literature is quite scanty in this regard, herein we present the chronic sequelae of sulfur mustard exposure after an acute and massive inhalation of this gas by a group of Iranian veterans in 1986.
*From the Department of Internal Medicine, Division of Respiratory Diseases, Shiraz University of Medical Sciences, Shiraz, Iran. Manuscript received August 23, 1996; revision accepted March 12, 1997. Reprint requests: Ali Emad, MD , PO Box 71345-1 674, Shiraz University of Medical Sciences, Shiraz, Iran 734
MATERIALS AND METHODS
Those patients with respiratory symptoms whose exposure to mustard gas had been confirmed b y studies on their urine and vesicular fluid (using the methods advocated by Heyndrickx et al 11 ) in a special toxicology laborat01y in 1986 were included. All these patients had their initial admissions in our university hospitals in 1986 because of the acute respiratory symptoms that included rhinonhea, sore throat, hoarseness, cough, chest tightness, and dyspnea. Patients were included only if they had no history of exposure to other environmental agents known to cause interstitial lung disease or extrinsic allergic alveolitis. In the interim (1986 to 1996), all patients had regular follow-ups in a s pecial outpatient clinic designed for these chemically injured vet erans. Jobs such as painting, woodworking, welding, farming, milling, sculpturing, fire fighting, and baking were not allowed. Home visits and inspection of workplace were regularly done and all subjects were instructed to avoid exposure to asbestos, coal dust, silicone, or cotton dust. None of the patients worked in petroleum industries. Subjects with known asthma (before their exposure to sulfur mustard gas ) (n=O), cigarette smokers (n=9), and those with proven cardiovascular disease (n=3) or other systemic illness (n=3) were excluded from the study. One hundred ninety-seven patients fulfill ed the above cJ;teria and were enrolled into the study. In addition, 84 nonsmoker veterans who had participate d in the war in another region in the Clinical Investigations
same year (1986) but had no exposure to the mustard gas were voluntarily entered into the study as our control group.
Study Design All subjects signed an informed written consent. Each patient was carefully examined. All patients had an ECG, a chest radiograph, and high-resolution CT (1-IRCT ) of the chest. All HRCTs were performed with l.O- or 1.5-mm-thick sections taken at 1-cm intervals throughout the entire thorax. Pulmona1y function tests (PFTs) were measured through spirometric assessment. An experienced physician did all spirometric measurements for all the subjects usi ng a spirometer (F UDAC .50; Fukuda Sangyo Co LTD; Chiba, Japan). Each patient was trained to give his best effort. After 15 min of resting, three spirometric measurements were done at 1-min intervals; th e highes t values were chosen and repmt ed. Each patient underwent a bronchodilator study by a standard dose of inhaled (3 2 -agonist as well, 12 and all tests were repeated again 15 to 20 min later. Reversibility of FEV1 was calculated by the following formula: (FEV1 after - FEV 1 before)/ FEV1 before. 12 The carbon monoxide diffusion capacity (Dco) was also measured for each patient. Treatment with inhaled (3 2 -agonist or inhaled ipratropium bromide was withdrawn for 8 h, and also treatment with anticholinergic agents, sodium cromoglycate, antihistamines, beclomethasone inhaler, and theophylline was discontinued 2 days prior to each patient's examination and his PFTs. All patients unde1went bronchoscopic examinations under appropriate and recommended precautions especially for asthmatic patients.J-3 The upper respiratory tract was anesthetized by 2% lidocaine. Atropine (0.75 mg IM ) was given before the procedure. Patients who were labeled as being asthmatic or having severe chronic bronchitis received a continuous infusion of aminophylline, 0.6 mglkglh, which was continued for 2 h after the termination of the procedure. Bronchial biopsy was done in all cases. Transbronchial lung biopsy was performed for only 24 patients whose spirometric data, chest radiographs, and HRCT of the chest14 were suggestive of interstitial lung disease. Biopsy specimens were obtained from all three lobes on the right side or from upper and lower lobes of the left lung.
Patients With Chronic Bronchitis Chronic bronchitis was defined when the following criteria were present: (1) no evidence of airway narrowing, stricture, or obstruction due to granulation tissue on bronchoscopy; (2) no evidence of bronchiectasis in the HRCT scan of the chest; (3) history of cough and sputum production for at least 3 mo/yr for 2:2 years; and (4) an obstructive pattern in th e results of spirometry. 18 The severity of chronic bronchitis was based on the values of patients' FEV 1 . 19 Mild COPD was defined as an FEV1 ::o:50% of predicted, moderate as FEV1 35 to 49% of predicted, and severe type as FEV1 <35% of predicted.
Patients With Pulnwnary Fibrosis Pulmonary fibrosis was considered to be present when all the following criteria were met: (1) a estrictive r pattern in the spirometric data; (2) decreased single-breath D co ; and (3) the lung biopsy specimen showing evidence of interstitial pneumonitis with varying degrees of interstitial fibrosis without evidence of granuloma formation. All transbronchiallung biopsy specimens were seen and interpreted b yan expert pathologist who had no information about the patients' clinical or paraclinical data. Individual slides of the lung biopsy specimens were stained with hematoxylin-eosin and Masson trichrome. The degree of fibrosis was given an estimate as compared to a normal lung specimen. Fibrosis was estimated to be mild, moderate, or severe when there was <25%, 25 to 40%, or >40% increase in the amount of visualized collagen.
Patients With Bronchiectasis The diagnosis of bronchiectasis was made according to the typical radiologic and HRCT findings. 20
Control Group The prerequisites for participation in the study were the same as tbose of the gas-exposed vete rans. All had a complete histmy and physical examination. In addition, a chest radiograph and an ECG were obtained and PFTs were measured in all of tbem .
Statistics Asthmatic Patients Patients were provisionally labeled as having asthma when they met at least two of the following three criteria: (1) typical history of attacks of breathlessness, wheezing, or both, nocturnal cough, chest tightness either spontaneously or triggered by exercise, respiratory infections, or irritants; (2) reversibility in FEVv defined as ([ FEV 1 after- FEV, before]/FEV1 before)> 15% after a standard dose of inhaled (3 2 -agonist;12 and (3) diurnal variability in peak expiratory flow (PEF ) rate >20%, calculated from the following formula: (highest PEF-lowest PEF)/highest PEF.L3 · 16 A patient was finally labeled as having asthma when bronchoscopy failed to show evidence of any upper or lower airway narrowing or obstruction due to granulation tissue or stricture form ation. The severity of asthma was determined by taking history, performing physical examination, the medications used, and the results of PFTs. Mild asthma was defin ed when the patients used only intermittent inhaled short-acting (3 2 -agonist as needed, and had a PEF 2:80% predicted valueP Moderate to severe asthma was defined when the patients needed daily inhaled anti-inflammatory agents or possible daily long-acting bronchodilator, and had a PEF :580% predicted value and a PEF variability of 2:30%.1'
All results are mean ±SD unless othervvise indicated. The two methods of x2 and Spearman were used for analysis of data. Spearman rank test was pe rformed to find out the correlation between the patient's age and th e type or severity of the pulmonary sequelae. Spearman rank correlation was also used to compare the degree of fibrosis with the age, percent FEV v percent FVC, and percent Dco because fibrosis was ranked from mild ( + 1)to moderate ( +2) and all other data were either continuous or ranked. In addition, because we had only one patient with severe degree of the fibrosis ( +3), this patient was not considered in the Spearman rank correlation.
RESULTS
The age range of the patients was 27 to 65 years (mean=34.39±5.95 years ) and that of the control group was 32 to 48 years (mean=35.52±3.97 years) (p=O.ll). Asthma was diagnosed in 21 (10.65%), chronic bronchitis in 116 (58.88%), and pulmonary fibrosis was seen in 24 (12.18%) patients. CHEST I 112 I 3 I SEPTEMBER, 1997
735
Table l-Mean Age and PFTs in 21 Patients With Asthma, 10 Years After Exposure to Sulfur Mustard Gas FEY1 , L
FYC, L
PEF Rate, Lis
Asthma
Age, yr
Observed
% of Predicted
Observed
% of Predicted
Observed
% of Predicted
Mild (n=6) Moderate to severe (n=15)
27.33::+::0.51 32.13::+::4.94
2.73::+::0.12 2.20::+::0.23
83.51::+::3.06 64.20::+::7.95
3.43::+::0.10 3.06::+::0.12
81.05::+::2.78 70.86::+::3.03
7.05::+::0.24 4.85::+::0.48
85.27::+::3.83 56.73::+::6.16
Table 2-The Mean Age and PFTs in 116 Patients With Chronic Bronchitis, 10 Years After a Single Heavy Exposure to Sulfur Mustard Gas FEY1 , L Chronic Bronchitis Mild (n = 27) Moderate (n=53) Severe (n=36)
PEF Rate, Us
FYC, L
Age, yr
Observed
% of Predicted
Obse1ved
% of Predicted
Observed
% of Predicted
36.51 ::+::9.63 35.26::+::6.04 35.36::+::2.99
2.23::+::0.14 1.45::+::0.17 1.19::+::0.05
68.98::+::5.07 47.49::+::2.20 33.01::+::1.54
3.51 ::+::0.28 2.49::+::0.28 2.43::+::0.28
70.03::+::4.49 51.79::+::2.96 43.57::+::2.72
6.00::+::0.91 4.57::+::0.39 2.40::+::0.30
67.80::+::8.24 49.11::+::6.61 30.60::+::3.71
Table 3-The Mean Age and PFTs in 17 Patients With Bronchiectasis and 19 Patients With Airway Stricture or Narrowing, 10 Years After Their Exposure to Sulfur Mustard Gas FEY, L Age, yr 32.94::+::1.71 Bronchiectasis (n=17) Airway stricture or 35.94::+::7.36 narrowing (n=19)
FYC, L
PEF Rate, Us
Observed
% of Predicted
Observed
% of Predicted
FEY/FYC,% Observed
2.22::+::0.30
65.75::+::10.6
3.01::+::0.15
70.52::+::3.73
73.59::+::8.47
5.13::+::0.75
60.97::+::9.78
1.96::+::0.26
56.90::+::8.10
2.83::+::0.26
66.33::+::5.62
67.91::+::10.56
4.58::+::0.57
54.57::+::7.41
Observed
% of Predicted
Asthmatic Patients
Patients With Bronchiectasis or Airway Stricture
There was only a significant difference between the age of the patients with asthma (mean=30.76±4.7 years) and those with chronic bronchitis (mean=35.48±6.3 years) (p=0.001). The results of FEVto FVC, FEV/FVC, and PEF rate in patients with asthma are shown in Table 1. Six asthmatic patients were classified as having mild asthma while the rest suffered from a moderate to a severe disease. There was a significant correlation between the age of the patients and the severity of asthma (r=0.67, p=0.002).
Diffuse bronchiectasis was seen in 17 patients (8.62%), and airway stricture or narrowing due to scaring or granulation tissue was detected in 19 patients (9.64%). Of these, seven were found in the trachea, eight in the main bronchi, and four in one or more of the lobar bronchi. Their ages and PFTs are shown in Table 3.
Patients With Chronic Bronchitis Mild, moderate, and severe chronic bronchitis was diagnosed in 27, 53, and 36 veterans, respectively (Table 2) . All 36 patients with severe bronchitis had dyspnea at rest and were dependent on long-term oxygen therapy with a mean of 37.75±10.99 months. One of these patients died of acute myocardial infarction soon after the termination of the study. There was no significant correlation between the patient's age and the severity of bronchitis (r=0.16, p=0.07). 736
Patients With Pulmonary Fibrosis The PFTs and degree of fibrosis in patients with pulmonary fibrosis are shown in Table 4. Twelve patients (50%) had mild fibrosis. Eleven patients (45.83%) had moderate pulmonary fibrosis, and only one patient (4.16%) had severe fibrosis. Alveolar septal fibrosis was a prominent finding in most of the patients (62.5%). Diffuse fibrosis was seen in only three patients (12.5%). Neither honeycomb formation nor granulation tissue or granuloma was seen in any of the biopsy specimens. Comparisons between the degree of fibrosis and the physiologic parameters of PFT and percent Dco are shown in Table 5. Of these, only the percentage of Dco showed a significant correlation with the degree of fibrosis . Clinical Investigations
Table 4-The Mean Age and PFTs in 24 Patients With Pulmonary Fibrosis, 10 Years After a Single Heavy Exposure to Sulfur Mustard Gas FVC, L
FEY 1, L Pulmonary Fibrosis Mild (n=12) Moderate (n =ll ) Severe (n =1)
Age, yr
Observed
% of Predicted
Obse rved
% o f Predicted
Dco,% of Predicted
32.58::!::3.63 31.09::!:: 1.22 38.00
3.02 ::!:: 0.34 2.79 ::!:: 0.32 2.94
82.43::!::3.48 81.84::!::3.67 81.83
3.45::!:: 0.37 3.39::!::0.25 2.65
65.34::!::7.02 55.53::!::6.97 50.00
69.08::!::6.52 51.45::!::8.29 21.00
Table 5-The Correlation Between the Degree of Fibrosis With the Age and PFTs of 24 Patients With Pulmonary Fibrosis* Degree of Fibrosis
Disease Categ01y p
Age, yr FYC, % FEY~> %
Dco,%
- 0.12 -0.39 - 0.68 -0.76
Table 6-The Correlation Between the Age and Severity of Disease in Each Individual Diagnostic Group of Gas-Exposed Veterans *
0.56 0.06 0.75 0.0003
*Spearman rank correlation was used for all comparisons.
The correlation between the age and severity of disease in each individual diagnostic group is shown in Table 6.
Control Group The FEV1 values ranged from 2.22 to 3.49 L (mean =3.14 ±0.33 L). The FVC and PEF rate ranged from 3.21 to 4.45 L (mean=4.27 ±0.14 L) and from 5.33 to 9.01 Us (mean=8.43±0.42 Us) , respectively. None of the subjects in the control group had any pulmonary disorder except one patient (age, 48 years old) who had mild chronic bronchitis with an FEV 1 of 54% of predicted value.
DISCUSSION
The vesicant effect of sulfur mustard has been known since early in this century. Despite the available international treaty on the banning of the use of chemical and biological agents in warfare,21 these agents were used heavily during the Iran-Iraq war in the 1980s.5·22 This gas is lipophilic. Tissues exposed to adequate concentration of this chemical agent undergo DNA alkylation, which can lead to the cell death.23 Sulfur mustard is also selective in its accumulation in fat tissue. The organs that are more prone to the acute effects of exposure to sulfur mustard gas are skin, eyes, upper and lower respiratory tracts, and sometimes the GI tract.3 In an acute heavy exposure to sulfur mustard gas, the columnar cells of the epithelial lining of the upper respiratory tract may shed. 6 This may also be
Asthma 1 Chronic bronchitis'
Pulmon ary fibrosi s§
Seve rity
Age, yr, mean ::t: SD
Mild Moderate-severe Mild Mode rate Severe Mild Mode rate
27.33::!::0.51 32.13::!::4.94 36.5l:t9.63 35.26::!::6.04 35.36::!::2.99 32.58::!::3.63 31.09::!:: 1.22
*Spearman rank corre lation was used for all comparisons. 1r=0. 67, p = 0.002. 1r=0.16, p=0.07. l r=-0.12, p=0.56.
accompanied by peribronchial edema, hyperemia of the blood vessels, cellular infiltrations in the submucosa, and intense vacuolization and disorganization of cytoplasmic and nuclear stmctures. 6·7·24 Pulmonary hemorrhage, pulmonary edema,25 and respiratory failure with a picture similar to ARDS may occur. These cytotoxic effects of sulfur mustard gas associated with the acute thermal injury sustained by the airway mucosa may le ad to the scarring and development of stenosis of the tracheobronchial tree, 26 as was seen in 19 (9.64%) of our patients. Recurrent infections are relatively common in the subacute and chronic phases of the lung involvement.27 This, accompanied by the loss of normal ciliary activity and airway obstruction, may lead to the development of bronchiectasis, which was seen in 17 (8.62%) of our patients. The incidence of asthma as a late sequela of pulmonary effects of sulfur mustard gas exposure was about 10.65% in this series of patients. This airway hyperreactivity may be induced by its cytotoxic effect .6·28 Chronic bronchitis is a well-known late complication of sulfur mustard gas inhalation in humans. 10 With an incidence of 58.88%, it was the most common pulmonary sequela in our patients. It was the cause of marked disability in all 36 patients with severe diseases and the only fatality was in this group of patients. There seemed to be apositive correlation between CHEST I 112 I 3 I SEPTEMBER, 1997
737
the age of the gas-exposed veterans to the severity of asthma and development of chronic bronchitis. That is, the older subjects had a higher chance of having a more severe form of asthma and a higher chance of developing chronic bronchitis. Pulmonary fibrosis as documented by spirometric studies and lung biopsy specimens was seen in 24 patients (12.18%). This relatively low incidence is probably because of the fact that most of the mustard gas is absorbed in the upper airways, producing more of an airway disease, and little reaches the alveoli, thus sparing the lung tissue from its devastating effects. Although physiologic parameters of the lungs are generally used to assess and monitor patients with pulmonary fibrosis, in comparison to the significant correlates with the degree of fibrosis, only percent Dco correlated well with the degree of pulmonary fibrosis in our veterans. Therefore, the percentage of Dco can be used as an objective monitor of the degree of fibrosis and also as a good predictor of prognosis in our gas-exposed patients with pulmonary fibrosis. Although lung cancer has been reported as a late complication of mustard gas inhalation, 29 •30 we have found no bronchial carcinoma or other lung malignancies in these veterans by now (after 10 years). Further follow-ups are needed for the assessment of the carcinogenic effect of this gas on the pulmonary system.
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Clinical Investigations