Bronchial arterial imaging using helical computed tomography

The bronchial arteries, which provide the systemic arterial supply to the lungs, are involved in a variety of disease processes in humans, including congenital disorders, infection, and pulmonary thromboembolism. In these conditions, the bronchial arteries hypertrophy and bronchial blood flow increases. Consequently, in many disorders, such as bronchiectasis, the bronchial arteries are a frequent source of haemoptysis, which may be massive and life-threatening. Evaluation of the bronchial circulation has typically required invasive imaging with angiography to determine the location of bleeding. Non-invasive assessment of bronchial arterial anatomy and morphology is currently being investigated with the use of helical computed tomography (CT). We evaluated eight patients with various lung diseases with helical CT (GE Medical Systems, LS16, Milwaukee, WI) to determine the imaging features of the bronchial circulation. Non-ionic contrast medium (iopromide) was injected intravenously (80-1000ml/30s) and scanning was triggered once contrast material was present in the pulmonary artery (average delay=15s) or ascending aorta (average delay=20s). Detector collimation (16-row unit) was 10mm. Imaging parameters included a section thickness of 0.6mm, kilovolt peak of 120, 150-440mA, pitch factor of 1.375, matrix of 512x512, and tube rotation time of 0.8s. The images were reconstructed and scanned isotropically (Advantage Workstation 4.1,GE Medical Systems). We conclude that helical computed tomography may provide a non-invasive means of evaluating the bronchial arteries and their role in pulmonary disease processes.

Bronchovascular responses to intravenous contrast media for helical CT pulmonary angiography

CT angiography is now commonly used for the diagnosis of pulmonary embolism, but the contrast media used for imaging produces various hemodynamic changes. In this study, we investigated the bronchovascular and hemodynamic responses to intravenous iopromide, a non-ionic contrast agent used for pulmonary CT angiograms, in anesthetized, mechanically ventilated sheep (n = 6). Bronchial blood flow and cardiac output were measured with ultrasonic flow probes. Systemic and pulmonary arterial pressures were continuously monitored. Injections of 0.9% NaCl (120 ml over 30 s) or iopromide (300 mg/ml, 120 ml over 30 s) were given in random order in a peripheral vein with an angiogram infuser and hemodynamic changes were determined. After these parameters returned to baseline, the left pulmonary artery (LPA) was occluded with a snare and the animals were allowed to stabilize. Injections of NaCl and iopromide were repeated in random order as before. There were no significant hemodynamic effects with infusion of NaCl. With intact pulmonary vasculature, NaCl and iopromide did not cause significant changes in arterial blood gases, however, cardiac output (QT, L/min), mean systemic and pulmonary arterial pressures (PSA and PPA, Torr) increased and bronchovascular resistance (BVR, Torr x min/ml), decreased. Following LPA ligation, pH and PO2 significantly decreased over baseline, whereas PCO2 increased. After LPA ligation, iopromide produced a greater decrease in BVR as compared with preligation intact pulmonary vasculature. In conclusion, iopromide caused rapid hemodynamic changes and decreased BVR, likely secondary to osmolar stress. Bronchovascular effects were more pronounced after pulmonary arterial occlusion.

Controlled trial of inhaled fluticasone propionate in moderate to severe COPD

Inhaled corticosteroids are often used in the treatment of stable chronic obstructive pulmonary disease (COPD), however, studies of these agents have had mixed results. Previous trials have often excluded subjects with bronchodilator response, have failed to evaluate effect on gas exchange, and have usually looked at only post- rather than prebronchodilator forced expiratory volume (FEV). Our objective was to better assess the efficacy of topical corticosteroids in the treatment of COPD. We used a prospective, randomized, double-blinded, placebo-controlled, crossover study at the Outpatient Department, Department of Veterans Affairs Medical Center. Thirty-six COPD patients with a mean (+/- SD) FEV1 of 1.10 +/- 0.43 L, with or without significant bronchodilator response participated in the study. Subjects received a 3-month course of inhaled fluticasone propionate (220 micro g/puff) or identical-appearing placebo by metered-dose inhaler at 2 puffs twice daily, followed by crossover to the alternative inhaler for an additional 3 months. Fluticasone treatment resulted in a higher prebronchodilator FEV1 (1.17 +/- 0.08 L [mean +/- SEM] versus 1.07 +/- 0.08 L, p = 0.001), a higher PaO2 (66.6 +/- 1.4 mmHg versus 63.6 +/- 1.6 mmHg, p = 0.002), and a better dyspnea score on the chronic respiratory questionnaire (3.70 +/- 0.18 versus 3.47 +/- 0.19, p = 0.03). A trend towards fewer exacerbations with fluticasone did not quite meet statistical significance (p = 0.11). Inhaled fluticasone over 3 months improved prebronchodilator airflow obstruction and oxygenation while decreasing dyspnea in moderate to severe COPD. Postbronchodilator FEV1 was not significantly changed.

Does sildenafil also improve breathing?

Sildenafil is being used by a number of patients with erectile dysfunction. Some of these patients also may have concomitant COPD. The effect of sildenafil on lung function is not known. Two patients with severe COPD and erectile dysfunction reported that their dyspnea improved when they took oral sildenafil for erectile dysfunction. Spirometry performed in these patients revealed an improvement in FEV(1) by 24% and 12%. This suggests that, in COPD patients, oral sildenafil does not have any deleterious effect on pulmonary function, and in some patients it may produce a modest improvement in FEV(1).

Effect of expiratory resistive loading on the noninvasive tension-time index in COPD

Expiratory resistive loading (ERL) is used by chronic obstructive pulmonary disease (COPD) patients to improve respiratory function. We, therefore, used a noninvasive tension-time index of the inspiratory muscles (TT(mus) = I/PI(max) x TI/TT, where I is mean inspiratory pressure estimated from the mouth occlusion pressure, PI(max) is maximal inspiratory pressure, TI is inspiratory time, and TT is total respiratory cycle time) to better define the effect of ERL on COPD patients. To accomplish this, we measured airway pressures, mouth occlusion pressure, respiratory cycle flow rates, and functional residual capacity (FRC) in 14 COPD patients and 10 normal subjects with and without the application of ERL. TT(mus) was then calculated and found to drop in both COPD and normal subjects (P<0.05). The decline in TT(mus) in both groups resulted solely from a prolongation of expiratory time with ERL (P<0.001 for COPD, P<0.05 for normal subjects). In contrast to the COPD patients, normal subjects had an elevation in I and FRC, thus minimizing the decline in TT(mus). In conclusion, ERL reduces the potential for inspiratory muscle fatigue in COPD by reducing TI/TT without affecting FRC and I.

Comparative effects of alpha-receptor stimulation and nitrergic inhibition on bronchovascular tone

Adrenergic agonists are known to influence bronchial blood flow and bronchovascular resistance. Recently, the nitrergic system has also been implicated in the control of bronchovascular tone. In this study, we compared the effects of the nitric oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) and the alpha(1)-receptor agonist phenylephrine on bronchovascular resistance in anesthetized sheep (n = 9). Bronchial blood flow, cardiac output, and systemic and pulmonary arterial pressures were continuously monitored. Phenylephrine (1.2-3.4 microg. kg(-1). min(-1)) was infused intravenously to increase mean systemic arterial pressure above 95 Torr for 10 min and then was discontinued. When hemodynamic parameters returned to baseline, nebulized phenylephrine (10 mg) was given over 10 min. When parameters again normalized, L-NAME (30 mg/kg) was infused intravenously over 1 min. Intravenous phenylephrine increased systemic vascular resistance by 40% at 10 min with no concurrent increase in bronchovascular resistance, but inhaled phenylephrine increased bronchovascular resistance by 66% at 10 min. By comparison, intravenous L-NAME produced a rapid and sustained fivefold increase in bronchovascular resistance at 10 min. We conclude that, although alpha-agonist stimulation has some influence on bronchovascular resistance in sheep, the nitrergic system has predominant control of bronchovascular tone.

Effect of aerosolized acetylcholine on bronchial blood flow

We studied the effects of aerosolized as well as intravenous infusion of acetylcholine on bronchial blood flow in six anesthetized sheep. Intravenous infusion of acetylcholine, at a dose of 2 microg/kg, increased bronchial blood flow from 45 +/- 15 (SE) to 74 +/- 30 ml/min, and vascular conductance increased by 76 +/- 22%. In contrast, aerosolized acetylcholine at doses of 2 and 20 microg/kg decreased bronchial vascular conductance by approximately 10%. At an aerosolized dose of 200 microg/kg, the bronchial vascular conductance increased by approximately 15%, and there was no further increase in conductance when the aerosolized dose was increased to 2,000 microg/kg. Pretreatment of animals with a nitric oxide synthase inhibitor, Nomega-nitro-L-arginine methyl ester hydrochloride, partially blocked the vasodilatory effects of intravenous acetylcholine and completely blocked the vasodilatory effects of high-dose aerosolized acetylcholine. These data suggest that aerosolized acetylcholine does not readily penetrate the vascular wall of bronchial circulatory system and, therefore, has minimal vasodilatory effects on the bronchial vasculature.

Effect of increased coronary venous pressure on left ventricular function in sheep

We studied the effect of increased coronary venous pressure (Pcv) on left ventricular (LV) function in nine anesthetized open-chested sheep. Pcv was increased by inflating a balloon in the coronary sinus. LV function was estimated by measuring maximum rate of change in LV pressure (dP/dt max) and LV end-diastolic pressure (LVEDP). Left anterior descending (LAD) coronary artery blood flow was measured with an electromagnetic flow probe. A control group (n=6) was studied similarly except that Pcv was not elevated. After completion of the experiment, LV wet/dry weight ratios were measured to estimate LV myocardial water content. The balloon inflation increased Pcv from 8.6+/-1.1 to 23.8+/-1.7 mmHg (mean+/-SEM), which decreased dP/dt max from 1611+/-236 at baseline to 1041+/-210 after 120 min of increased Pcv (P < 0.05). The dP/dt max in the control group did not change significantly. Heart rate, LAD flow, LVEDP, and aortic pressures were similar in two groups but the LV water content was significantly higher (P < 0.05) in the experimental group (76.2+/-1.0 vs. 79.1+/-0.5%). These data suggest that acute increases in Pcv result in LV dysfunction and that coronary vascular congestion and myocardial edema may, at least in part, be responsible for this finding.

Non-cAMP-mediated bronchial arterial vasodilation in response to inhaled beta-agonists

We studied the dose-dependent effects of inhaled isoetharine HCl, a beta-adrenergic bronchodilator (2.5, 5.0, 10.0, and 20.0 mg), on bronchial blood flow (Qbr) in anesthetized sheep. Isoetharine resulted in a dose-dependent increase in Qbr. With a total dose of 17.5 mg, Qbr increased from baseline values of 22 +/- 3.4 (SE) to 60 +/- 16 ml/min (P < 0.001), an effect independent of changes in cardiac output and systemic arterial pressure. To further study whether synthesis of endogenous nitric oxide (NO) affects beta-agonist-induced increases in Qbr, we administered isoetharine (20 mg) by inhalation before and after the NO-synthase inhibitor N omega-nitro-L-arginine methyl ester (L-NAME). Intravenous L-NAME (30 mg/kg) rapidly decreased Qbr by approximately 80% of baseline, whereas L-NAME via inhalation (10 mg/kg) resulted in a delayed and smaller (approximately 22%) decrease. Pretreatment with L-NAME via both routes of administration attenuated bronchial arterial vasodilation after subsequent challenge with isoetharine. We conclude that isoetharine via inhalation increases Qbr in a dose-dependent manner and that beta-agonist-induced relaxation of vascular smooth muscle in the bronchial vasculature is partially mediated via synthesis of NO.

Bronchial vascular congestion and angiogenesis

The bronchial vasculature is the systemic arterial blood supply to the lung. Although small relative to the pulmonary blood flow, the bronchial vasculature serves important functions and is modified in a variety of pulmonary and airway diseases. Congestion of the bronchial vasculature may narrow the airway lumen in inflammatory airway diseases, and formation of new bronchial vessels (angiogenesis) is implicated in the pathology of a variety of chronic inflammatory, infectious and ischaemic pulmonary diseases. The remarkable ability of the bronchial vasculature to remodel has implications for disease pathogenesis. The contributions of the bronchial vasculature to the pathogenesis of pulmonary disease are reviewed in this article.

Management of bronchopleural fistula with a variable-resistance valve and a single ventilator

Independent lung ventilation with two ventilators is sometimes used in the management of bronchopleural fistula (BPF). We describe a patient in whom gas flow through a large BPF was initially reduced, and subsequently eliminated, during differential lung ventilation using a single ventilator and a variable-resistance valve attached to one lumen of a bifurcated endotracheal tube.

Nitric oxide and beta-adrenergic agonist-induced bronchial arterial vasodilation

In anesthetized sheep, we measured bronchial blood flow (Qbr) by an ultrasonic flow probe to investigate the interaction between inhaled nitric oxide (NO; 100 parts/million) given for 5 min and 5 ml of aerosolized isoetharine (1.49 x 10(-2) M concentration). NO and isoetharine increased Qbr from 26.5 +/- 6.5 to 39.1 (SE) +/- 10.6 and 39.7 +/- 10.7 ml/min, respectively (n = 5). Administration of NO immediately after isoetharine further increased Qbr to 57.3 +/- 15.1 ml/min. NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester hydrochloride (L-NAME; 30 mg/kg, in 20 ml saline given i.v.) decreased Qbr to 14.6 +/- 2.6 ml/min. NO given three times alternately with isoetharine progressively increased Qbr from 14.6 +/- 2.6 to 74.3 +/- 17.0 ml/min, suggesting that NO and isoetharine potentiate vasodilator effects of each other. In three other sheep, after L-NAME three sequential doses of isoetharine increased Qbr from 10.2 +/- 3.4 to 11.5 +/- 5.7, 11.7 +/- 4.7, and 13.3 +/- 5.7 ml/min, respectively, indicating that effects of isoetharine are predominantly mediated through synthesis of NO. When this was followed by three sequential administrations of NO, Qbr increased by 146, 172, and 185%, respectively. Thus in the bronchial circulation, there seems to be a close interaction between adenosine 3',5'-cyclic monophosphate- and guanosine 3',5'-cyclic monophosphate-mediated vasodilation.

Angiogenesis in bronchial circulatory system after unilateral pulmonary artery obstruction

We studied the effects of left pulmonary artery (LPA) ligation on the bronchial circulatory system (BCS) by using a sheep model. LPA was ligated in the newborn lambs soon after birth (n = 8), and when the sheep were approximately 3 yr of age anatomic studies revealed marked angiogenesis in BCS. Bronchial blood flow and cardiac output were studied by placing flow probes around the bronchial and pulmonary arteries in four adult sheep. After LPA ligation, bronchial blood flow increased from 35 +/- 6 to 134 +/- 42 ml/min in approximately 3 wk (P < 0.05). We also studied gas-exchange functions of BCS approximately 3 yr after the ligation of LPA in newborn lambs (n = 4) and used a control group (n = 12) in which LPA was ligated acutely. In the left lung, O2 uptake after acute ligation was 16 +/- 3 ml/min and was similar to the chronic model, whereas CO2 output in the control group was 27 +/- 3 ml/min compared with 79 +/- 12 ml/min in the chronic preparation (P < 0.05). We conclude that LPA ligation causes marked angiogenesis in BCS that is capable of performing some gas-exchange functions.

Changes in bronchial and pulmonary arterial blood flow with progressive tension pneumothorax

We studied the effects of unilateral tension pneumothorax and its release on bronchial and pulmonary arterial blood flow and gas exchange in 10 adult anesthetized and mechanically ventilated sheep with chronically implanted ultrasonic flow probes. Right pleural pressure (Ppl) was increased in two steps from -5 to 10 and 25 cmH2O and then decreased to 10 and -5 cmH2O. Each level of Ppl was maintained for 5 min. Bronchial blood flow, right and left pulmonary arterial flows, cardiac output (QT), hemodynamic measurements, and arterial blood gases were obtained at the end of each period. Pneumothorax resulted in a 66% decrease in QT, bronchial blood flow decreased by 84%, and right pulmonary arterial flow decreased by 80% at Ppl of 25 cmH2O (P < 0.001). At peak Ppl, the majority of QT was due to blood flow through the left pulmonary artery. With resolution of pneumothorax, hemodynamic parameters normalized, although abnormalities in gas exchange persisted for 60-90 min after recovery and were associated with a decrease in total respiratory compliance.

Controlled trial of oral prednisone in outpatients with acute COPD exacerbation

Corticosteroids are often used in the outpatient treatment of acute exacerbation of chronic obstructive pulmonary disease (COPD). To date, there are few data documenting the benefit of this practice. The objective of this randomized, double-blind, placebo-controlled trial was to assess the efficacy of corticosteroids in the outpatient treatment of COPD exacerbations. Twenty-seven patients presenting with acute COPD exacerbation were studied. In addition to continuing their previous medications and increasing their use of beta-agonists, patients were randomized to receive a 9-d tapering dose of either oral prednisone or placebo. Treatment with prednisone rather than placebo resulted in a more rapid improvement in arterial PO2 (PaO2) (1.12 mm Hg/d versus -0.03 mm Hg/day; p = 0.002), alveolar-arterial oxygen gradient (A-aDO2) (-1.16 mm Hg/d versus -0.03 mm Hg/day; p = 0.04), FEV1 (0.05 L/d versus 0.00 L/d; p = 0.006), and peak expiratory flow (PEF) (0.15 L/s/d versus 0.04 L/s/d; p = 0.009). Prednisone also resulted in fewer treatment failures (p = 0.002) and in a trend toward more rapid improvement in dyspnea scale scores. Outpatient treatment of acute COPD exacerbation with prednisone accelerates recovery of PaO2, A-aDO2, FEV1, and PEF, reduces the treatment failure rate, and improves subjective dyspnea.

Impaired bronchodilator response to albuterol in healthy elderly men and women

BACKGROUND

Lymphocytes of normal elderly subjects and young asthmatics display dysfunctional beta-adrenoceptors. If beta-adrenoceptor dysfunction were found in senescent airways, it might help explain the pathogenesis of late onset asthma.

METHODS

The bronchodilatory effects of albuterol after methacholine-provoked bronchoconstriction were compared in 17 healthy young (age 20 to 36 years) and 17 healthy elderly (age 60 to 76 years) volunteer subjects. Albuterol was inhaled via dosimeter (initially 7.8 micrograms, doubling every 7.5 min) with forced expiratory flow at 50% vital capacity (FEF50) measured prior to each dose. Albuterol sensitivity was expressed as the cumulative logarithm of the area under the FEF50 recovery curve (AUC); a greater AUC meant lower sensitivity. On another study day, spontaneous recovery from methacholine was assessed similarly.

RESULTS

There was no intergroup difference in spontaneous recovery. Despite lower methacholine doses provoking similar (35%) FEF50 falls in elderly subjects, albuterol AUC was greater in elderly subjects (6,552%.min.microgram) than young subjects (3,922%.min microgram; p = 0.03). Multiple regression showed that AUC and age were related (p = 0.02).

CONCLUSION

Airway beta 2-adrenoceptor responsiveness is diminished in old age, suggesting that airway beta-adrenoceptor dysfunction may be implicated in late-onset asthma.

Effects of erythromycin on the rabbit pleura: its potential role as a pleural sclerosant

Tetracycline (TCN) has been considered the agent of choice for pleurodesis in patients with symptomatic malignant pleural effusions and recurrent pneumothoraces. However, the intravenous form of TCN used for pleurodesis is no longer available. Erythromycin, like TCN, often produces irritation when administered intravenously. In view of these irritant properties, we tested the effect of erythromycin as a pleural sclerosant in rabbits as compared with TCN. Normal saline was used as a control. Adult rabbits weighing 2.5 to 3.0 kg underwent sterile placement of a silastic pleural tube in the right pleural space. Erythromycin (n = 17) or TCN (n = 6), each in doses of 35 mg/kg in 2 ml saline, was administered via the tube. Control animals (n = 6) received 2 ml saline. The chest tubes were left in place for removal of pleural fluid and to maintain lung expansion. Animals were killed 8 d after receiving the various treatments, and their pleural surfaces were examined grossly and histologically. Numerous adhesions were present between the visceral and parietal pleurae in all animals receiving erythromycin and TCN, but not in those receiving saline. On light microscopy, pleurae treated with erythromycin or TCN were histologically identical, showing inflammation, edema, and fibroblast proliferation in the submesothelial tissues. The saline-treated animals had a normal pleura. Because erythromycin produced pleural inflammation and adhesions within 8 d of treatment, we propose that it may have a potential role as a pleural sclerosant.

Independent lung ventilation with a single ventilator using a variable resistance valve

Independent lung ventilation using two ventilators has been attempted in the treatment of acute respiratory failure due to unilateral lung disease. However, this method has been found to be cumbersome and difficult to use. We reasoned that a bifurcated endotracheal tube with a variable resistance valve may enable us to change the inspiratory airway pressures and, hence, the inspired tidal volume to one lung using a single ventilator. We tested this hypothesis in eight anesthetized sheep and created a bronchopleural fistula in one lung as a model of unilateral lung disease. A bifurcated endotracheal tube was placed to separate the ventilation to each lung and, through a "Y" connector, both right and left lungs were ventilated simultaneously with a single ventilator. A variable resistance valve was placed between the "Y" connector and the tube ventilating the experimental lung with bronchopleural fistula. With a ventilator-generated peak inspiratory pressure of 31 +/- 2 cm H2O, the airway pressure distal to the valve was randomly changed from 31 cm H2O to 23 +/- 2, 15 +/- 1, 8 +/- 1, and 0 cm H2O. This resulted in progressive diversion of tidal volume from the experimental lung to the control lung and an increase in exhaled tidal volume due to a decrease in air leak from the bronchopleural fistula. These data suggest that a variable resistance valve may be used for independent lung ventilation using a single ventilator.

Streptococcus pneumoniae-induced pulmonary hypertension and systemic hypotension in anesthetized sheep

Because some patients with Streptococcus pneumoniae bacteremia may present with shock, we reasoned that this organism may produce substances that cause shock. To test this hypothesis, type III pneumococcus supernatant, suspended in 10 ml of sterile water, was infused over 1 min in 8 adult anesthetized sheep. Normal saline was used as a control and had no effect on any of the hemodynamic parameters. Infusion of supernatant resulted in a precipitous fall in cardiac output from a control value of 4.25 +/- 0.54 to 2.80 +/- 0.43 (SE) l/min, a fall in mean systemic arterial pressure from 70 +/- 4 to 49 +/- 8 mmHg, and an increase in the mean pulmonary arterial pressure from 13 +/- 2 to 23 +/- 4 mmHg within 1 min after the infusion was completed. The peak hemodynamic effects were observed at approximately 3 min and returned to normal within 10 min after the infusion was completed. The thromboxane B2 level increased from a control value of 10 +/- 5 to 156 +/- 43 pg/ml at 3 min after the infusion was completed and decreased to 63 +/- 34 pg/ml at 20 min. A second identical dose of pneumococcal supernatant, repeated within 2 h of the first dose, had no effect on hemodynamic variables. Pretreatment with indomethacin, 5 mg/kg body wt, completely blocked the hemodynamic effects of pneumococcal supernatant (n = 3 sheep). Thus, we conclude that S. pneumoniae supernatant contains substances that cause septic shock syndrome through the synthesis of arachidonic acid metabolites and that a sublethal dose of the supernatant causes rapid tachyphylaxis.

Piperacillin/tazobactam compared with ticarcillin/clavulanate in community-acquired bacterial lower respiratory tract infection

The efficacy and safety of a new combination parenteral antibiotic, piperacillin/tazobactam, was compared with that of parenteral ticarcillin/clavulanate in the treatment of adult patients with community-acquired lower respiratory tract infections. A total of 299 patients were enrolled in this multicentre, double-blind, comparative study; 177 received piperacillin/tazobactam and 122 received ticarcillin/clavulanate. Of these, 119 met the evaluability criteria (69, piperacillin/tazobactam and 50, ticarcillin/clavulanate). The study drugs (piperacillin/tazobactam 3 g/375 mg or ticarcillin/clavulanate 3 g/100 mg) were given every 6 h by slow iv infusion for a minimum of 5 days. The favourable clinical response (cured and improved) rates of evaluable patients were 84% and 64% at endpoint (P < 0.01) for piperacillin/tazobactam and ticarcillin/clavulanate, respectively. The favourable bacteriological response at the early follow-up (eradicated and presumed eradicated) were 91% and 67% for piperacillin/tazobactam and ticarcillin/clavulanate, respectively (P < 0.01). At endpoint, 84% and 64%, respectively (P = 0.02) had a favourable response. The most common adverse experiences involved the gastrointestinal tract and occurred in 31.6% of the piperacillin/tazobactam group compared with 20.5% in the ticarcillin/clavulanate group (P = 0.02). These events were mild and generally did not affect therapy. Piperacillin/tazobactam appears to be more effective than ticarcillin/clavulanate in this patient population and is generally well tolerated.

Use of plasma for arterial blood gas analysis in leukemia

A 63-year-old patient with chronic lymphocytic leukemia presented with severe hypoxemia. However, the patient's hemoglobin saturation, measured by an ear oximeter, was normal. Although his WBC count was approximately 1,000,000/microliters, hypoxemia could not be explained by the consumption of oxygen by leukocytes. Therefore, arterial blood gas values were analyzed in both plasma as well as in whole blood. The PaO2 in the plasma was much higher than in whole blood and corresponded with the hemoglobin saturation measured by the ear oximeter. These findings suggest that very high leukocyte counts may interfere with the measurement of oxygen tension and that plasma may be used for blood gas analysis in this situation.

Peripheral mononuclear leucocyte beta adrenoceptors and non-specific bronchial responsiveness to methacholine in young and elderly normal subjects and asthmatic patients

BACKGROUND

As beta adrenoceptor dysfunction occurs in both the normal elderly subject and in young asthmatic patients, the hypothesis was examined that age related beta adrenoceptor changes are important in the pathogenesis of late onset asthma in old age.

METHODS

Subjects were non-smokers who comprised 17 young normal subjects of mean (SE) age 29.4 (1.3) years, 17 elderly normal subjects of 67.2 (1.3) years, seven young asthmatic patients of 31.0 (2.8) years, and 17 elderly asthmatic patients of 68.5 (1.4) years. All asthmatic patients withheld inhalers for 12 hours and oral treatment for 24 hours before each study day. Subjects underwent an inhaled methacholine challenge (Newcastle dosimeter method) on two nonconsecutive days. The slope of the flow at 50% of the vital capacity (FEF50) dose-response curve was derived from the percentage fall in FEE50 divided by methacholine dose (sFEF50). Beta-adrenoceptor density (Bmax) and affinity (%KH) were determined with (125I)iodocyanopindolol as the radioligand in membranes prepared from mononuclear leucocytes.

RESULTS

Log sFEF50 was shown to be reproducible (repeatability coefficient 0.41) on the two study days and was inversely related to %KH but not to Bmax. Multiple regression analysis (all 58 subjects, overall R2 = 0.57) revealed an inverse relation between log sFEF50 and %KH, and between log sFEF50 and Bmax. The inverse relation between log sFEF50 and %KH was preserved whereas that between log sFEF50 and Bmax was lost when young asthmatic subjects or when all asthmatic subjects were excluded from multiple regression analysis.

CONCLUSIONS

The beta adrenoceptor dysfunction observed in late onset asthma may be similar to that seen during ageing. Thus late onset asthma may represent the extreme of a spectrum of age associated beta adrenoceptor dysfunction.

Effects of tube thoracostomy on pleural fluid characteristics in sheep

We studied the pleural inflammatory response to tube thoracostomy by inserting an Argyle 32-Fr tube in the pleural space of 10 anesthetized sheep. An experimental pleural effusion was created by infusion of sterile normal saline (10 ml/kg) into the pleural space, and the animals were allowed to recover. Systemic blood and experimental pleural effusion (EPE) samples were obtained at time 0, 30 min, hourly for 6 h, and at 6-h intervals for a total of 48 h. EPE white cell count rose from 125 +/- 125 to 6,323 +/- 2,268/microliters (SE) at 6 h (P < 0.05) but showed marked variability at 42 and 48 h (P < 0.05), with values ranging from 8,000 to 22,000/microliters. The systemic white cell count rose from 5,195 +/- 914 to 9,640 +/- 1,110/microliters (P < 0.01) within the first 12 h and then remained stable. EPE protein increased from 0 +/- 0 to 3.73 +/- 0.2 g/dl at 48 h (P < 0.05). EPE lactate dehydrogenase rose from 44 +/- 12 IU/l to a peak of 638 +/- 55 IU/l at 24 h (P < 0.05). EPE glucose was significantly lower than serum glucose at 36, 42, and 48 h (P < 0.05). These data indicate that chest tube placement rapidly induces significant pleural inflammation and results in formation of a sterile exudate.

Unilateral pulmonary edema. An unusual cause

A patient presented with shortness of breath without fever, cough or sputum production. The patient was hypoxic without leukocytosis and a chest x-ray film demonstrated a right unilateral pulmonary infiltrate. A chest CT showed a large ascending thoracic aortic aneurysm with dissection. During surgical repair, the aneurysm was noted to be compressing the single right pulmonary vein. The infiltrate resolved postoperatively, and the patient has remained symptom-free for one year.

Relationship between nonspecific bronchial responsiveness to methacholine and peripheral mononuclear leukocyte beta-adrenergic receptor function in young drug-naive subjects

Asthma is associated with dysfunction of the beta-adrenergic receptor adenylyl cyclase signal transduction pathway. It has been argued that this results from receptor down-regulation by beta-agonist therapy. This study examined the relationship between nonspecific bronchial responsiveness (NSBR) to methacholine (Newcastle dosimeter method) and beta-adrenergic receptor density (Bmax) and affinity (%KH) in membranes from peripheral blood mononuclear leukocytes (MNL) in 12 male (27.3 +/- 1.7 yr old) and 14 female (31.4 +/- 1.7 yr old) drug-naive subjects with and without symptoms of mild intermittent wheezing. None had ever smoked or received any antiasthma medication. "Hyperresponsive" subjects were defined as those (n = 11) whose simplified slope of FEF50 (calculated as the percent fall in FEF50 divided by the dose of methacholine) was more than one SD above the mean for asymptomatic subjects. The log of the slope was reproducible (repeatability coefficient = 0.43) on two nonconsecutive days. Multiple regression analysis (overall R2 = 0.57) revealed negative relationships between the log of the slope and both Bmax (p = 0.016) and %KH (p = 0.011). Analysis of variance confirmed a lower mean (+/- SEM) value of %KH in "hyperresponsives" (45.7 +/- 5.5%) than in "normoresponsives" (60.4 +/- 4.1%, p = 0.04) with a similar trend for Bmax (hyperresponsives = 33.5 +/- 4.1 fmol/mg, normoresponsives = 45.9 +/- 7.1 fmol/mg, p = 0.18). These relationships between bronchial responsiveness, Bmax, and %KH cannot be explained by drug therapy, and they provide further evidence that there is an intrinsic impairment in the function of beta-adrenergic receptors on peripheral MNLs from subjects with high levels of nonspecific bronchial responsiveness.

Reduced subjective awareness of bronchoconstriction provoked by methacholine in elderly asthmatic and normal subjects as measured on a simple awareness scale

BACKGROUND

Asthma death rates are rising, with the greatest rise and highest death rates in old age. A reduced cardiovascular response in the elderly may lead to the underestimation by physicians of the severity of acute asthma attacks. This would be compounded if elderly patients had reduced awareness of bronchoconstriction.

METHODS

Methacholine provoked bronchoconstriction was compared in 34 elderly (17 asthmatic, 17 normal; age 60-83, mean 68 years) and 33 young subjects (16 asthmatic, 17 normal; 20-46, mean 30 years). None were smokers. All underwent inhaled methacholine challenge by the Newcastle dosimeter method, monitored by maximal expiratory flow-volume loops (MEFVL). The endpoints were a 35% fall in forced expiratory flow at 50% vital capacity or cumulative inhalation of 6.4 mg methacholine. The one second forced expiratory volume (FEV1) was derived from MEFVL. After challenge and before bronchodilatation subjects graded awareness of respiratory discomfort from 1 (no symptoms) to 4 (pronounced symptoms needing immediate treatment).

RESULTS

Despite a greater fall in FEV1 in elderly asthmatic patients (mean (SE) 27.4% (2.2%)) than in young asthmatic patients (21.5% (1.7%)) elderly patients were less aware of bronchoconstriction (awareness score 2.00 (SE 0.15) than young patients (3.06 (0.11)). Similar differences in awareness score were seen between elderly normal subjects (1.53 (0.17)) and young normal subjects (2.76 (0.22)), despite no difference in degree of bronchoconstriction.

CONCLUSIONS

Reduced awareness of moderate acute bronchoconstriction in old age may delay self referral in acute asthma and contribute to higher asthma mortality in the elderly.

Endobronchial granulocytic sarcoma causing acute respiratory failure in acute myelogenous leukemia

Infiltration by leukemic cells may occur in many organs. When localized masses caused by myeloid leukemic infiltration occur, they are called granulocytic sarcomas. Such tumors may be mistaken for primary carcinomas. In this report, we describe a 63-yr-old man with acute myelogenous leukemia who developed progressive atelectasis of the left lower lobe of the lung. Bronchoscopy revealed a fungating endobronchial tumor completely obstructing the left lower lobe bronchus and partially occluding the left upper lobe bronchus. Biopsies from this lesion showed an endobronchial granulocytic sarcoma. Despite chemotherapy, the patient developed progressive hypoxemia and died.

Systemic arterial blood supply to the trachea and lung in sheep

We studied the systemic arterial blood supply to the trachea and lung in adult sheep. After anesthesia, sheep were exsanguinated and then studied by intra-arterial injection of one of the following materials: saline containing dyes of various colors (n = 24), Microfil (n = 8), or Batson's solution (n = 6). The systemic blood supply to the cervical trachea originated from the two common carotid arteries via three to four small branches (rami tracheales cervicales) on each side. A segment of the thoracic trachea between the thoracic inlet and the origin of the tracheal bronchus (bronchus trachealis) and the bronchial tree of the right cranial lobe (lobus cranialis dexter) were supplied by the tracheal bronchial branch (ramus bronchalis trachealis), which originated from the brachiocephalic trunk (truncus brachiocephalicus). A portion of thoracic trachea between the origin of the tracheal bronchus and the tracheal carina was supplied by the thoracic tracheal branch (ramus trachealis thoracica), arising from the bronchoesophageal artery (arteria bronchoesophagea) or directly from the thoracic aorta. The bronchial branch (ramus bronchalis) originated from the bronchoesophageal artery, and its branches supplied the remainder of the bronchial tree. At 120 cmH2O pressure (n = 8), the bronchial branch contributed approximately 50% and the other two approximately 25% each of the total tracheobronchial blood flow. These three branches also supplied the visceral pleura. Additionally, several small vessels (rami pleurales pulmonales) originated from the esophageal branch (ramus esophagea) of the bronchoesophageal artery, traversed the pulmonary ligaments, and supplied the visceral pleura.

Hypoxia and hypercarbia increase bronchial blood flow through bronchopulmonary anastomoses in anesthetized dogs

We studied the effect of systemic hypoxemia and hypercarbia on the bronchial blood flow in open-chested, anesthetized dogs. The pulmonary artery and vein of the left lower lobe (LLL) were isolated with cannulas and connected to reservoirs set at atmospheric pressure relative to the base of the LLL. That fraction of the bronchial arterial flow (Qbr) to the LLL, which flowed through the bronchopulmonary anastomoses into these reservoirs, was continuously measured. The LLL was inflated continuously with 6% CO2 and air at a constant alveolar pressure of 10 cm H2O. Systemic arterial O2 tension (PaO2) and arterial CO2 tension (PaCO2) were varied by separately ventilating the right lung through a bifurcated endotracheal tube. A 10-min period was allowed for stabilization after each change in experimental condition. Anastomotic Qbr was measured for 5 min during each experiment. In separate animals, similar studies were performed before and 30 min after intravenously administered indomethacin (6 mg/kg body weight). During normoxic conditions when PaO2 was 79 +/- 8 torr (mean +/- SEM), the mean anastomotic Qbr was 5.7 +/- 2.0 ml/min (n = 9). This flow increased to 8.3 +/- 2.5 ml/min (p less than 0.05) during hypoxemic conditions (PaO2, 38 +/- 3). The anastomotic Qbr increased from 5.8 +/- 1 to 9.0 +/- 2 ml/min (p less than 0.005) when PaCO2 was increased from 23 +/- 1 to 47 +/- 2 torr (n = 11). Pretreatment with intravenously administered indomethacin blocked both the hypoxemia-induced (n = 4) and hypercarbia-induced (n = 4) increases in anastomotic Qbr. We conclude that both hypoxemia and hypercarbia increased the anastomotic Qbr through a mechanism involving cyclooxygenase products of arachidonic acid.

Factors affecting bronchial blood flow through bronchopulmonary anastomoses in dogs

Most of the bronchial arterial blood flow (Qbr) drains through bronchopulmonary anastomoses into the pulmonary circulation, and the remainder goes into the systemic venous system via the bronchial veins. We studied the relationship between blood flow through bronchopulmonary anastomoses, and alveolar pressure and pulmonary vascular pressures as well as hydrostatic pressure in the bronchial veins in 10 adult dogs. The pulmonary artery and vein of the experimental left lower lobes (LLL) of open-chested, anesthetized dogs were isolated and connected to reservoirs. That part of the Qbr that flowed through bronchopulmonary anastomoses into the reservoirs was continuously measured at constant pulmonary vascular pressures of 0 cm H2O relative to the lung base. Any bronchial blood volume that retained within the LLL was estimated from changes in lobe weight. The lobe was distended with 5% CO2 and air, at alveolar pressures of 5, 10, or 20 cm H2O in a random sequence. Because bronchial veins drain into the azygos vein, the bronchial venous pressure was elevated by snaring the azygos vein. The mean anastomotic Qbr was 4.4 +/- 1.1 (mean +/- SEM) ml/min and it decreased by 23 and 39% when alveolar pressure was raised from 5 cm H2O to 10 and 20 cm H2O respectively (p less than 0.05). Approximately 75% of the total anastomotic Qbr was collected from the pulmonary venous reservoir at all alveolar pressures. When both pulmonary artery and venous pressures were increased higher than the alveolar pressure (zone III), azygos snaring increased the anastomotic Qbr by 13 and 31% at alveolar pressures of 10 and 20 cm H2O, respectively (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Theophylline clearance in patients with severe chronic obstructive pulmonary disease receiving supplemental oxygen and the effect of acute hypoxemia

The effect of hypoxemia on the disposition of theophylline was examined in 10 stable patients with chronic obstructive pulmonary disease (COPD) receiving chronic theophylline and supplemental home oxygen therapy. Pharmacokinetics after intravenous theophylline were estimated on the second day of supplemental oxygen (PaO2, 69 +/- 4 mmHg; mean +/- SEM) and on the second day of room air breathing (PaO2, 43 +/- 3) using a randomized cross-over design. On each occasion stable isotope-enriched theophylline (10 mg, m/z 183) was administered intravenously along with the regular oral dose of theophylline (m/z 180). Concentrations of both forms of theophylline in plasma samples obtained over 24 h were measured using mass spectrometry. Theophylline clearance during oxygen therapy (0.048 +/- 0.005 L/h/kg) was similar to that during room air breathing (0.050 +/- 0.004 L/h/kg). Values for elimination half-life (7.6 +/- 0.8 versus 6.8 +/- 0.6 h) and volume of distribution at steady state (0.450 +/- 0.021 versus 0.429 +/- 0.024 L/kg) were also unchanged. The volume of distribution of theophylline was inversely related to arterial pH during oxygen therapy (pH range, 7.32 to 7.44) and during room air breathing (pH range, 7.33 to 7.47). Although hypoxemia does not alter theophylline clearance in patients with COPD, theophylline loading doses may need adjustment according to arterial pH because of an effect on volume of distribution.

Effect of increased bronchial venous pressure on lung lymph flow

We postulated that if the bronchial circulation affects lung fluid balance, increases in bronchial venous pressures may influence lung lymph flow. This hypothesis was tested in eight anesthetized sheep prepared with acute lung lymph fistulas. After control data, we increased bronchial venous pressure by infusing saline directly into the bronchial vein at a controlled infusion pressure of 20-25 cmH2O. Evans blue dye (2.5 mg/ml) was added into the saline as a marker for assessing leakage that might occur from either the catheter or the ruptured bronchial veins. Lymph flow was measured every 15 min. Lymph as well as plasma samples were collected every 30 min for measurement of protein. In five sheep we also measured Evans blue dye content both in lymph and plasma to further characterize the role of bronchial circulation in lung fluid balance. The control lymph flow was 1.9 +/- 0.2 ml/15 min, and lymph-to-plasma protein ratio was 0.65 +/- 0.3 (mean +/- SE). With infusion of saline into the bronchial vein, the mean lung lymph flow and lymph-to-plasma protein ratio did not change significantly. There was a progressive increase in dye content both in lymph and plasma. The mean Evans blue dye content in lymph was 0.087, 0.16, and 0.26 microgram/ml, whereas in plasma it was 0.43, 1.15, and 1.45 microgram/ml in samples obtained at 30, 60, and 90 min, respectively. The dye content was significantly higher in the plasma compared with the lymph in all three samples (less than 0.05). Pulmonary arterial pressure, pulmonary capillary wedge pressure, and cardiac output did not change significantly throughout the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of accidental chlorine inhalation on pulmonary function

In an industrial accident, 19 previously healthy workers were briefly exposed to high concentrations of chlorine gas. Pulmonary function tests were done at intervals for about two years but complete follow-up data were available in only 11 subjects. Immediately following the exposure, airway obstruction was detected in 10 of 19 patients; 700 days later this was found in only 3 of 11 patients. Two of these three patients had a history of smoking, however. The mean residual volume was 141% +/- 97 (mean +/- standard error of the mean) on day 1. In subsequent follow-up studies, the residual volume progressively fell in all patients, and 700 days later the mean residual volume was 90% +/- 5. In 5 of the 19 subjects, all pulmonary function test results were within normal limits on day 1. Apparently in some subjects acute exposure to chlorine gas may cause immediate changes in the lung functions, but these changes gradually resolve. Because of the small number of patients in our series, however, the long-term effects of chlorine are less apparent.

Measurement of bronchial arterial blood flow and bronchovascular resistance in sheep

We studied the bronchial arterial blood flow (Qbr) and bronchial vascular resistance (BVR) in sheep prepared with carotid-bronchial artery shunt. Nine adult sheep were anesthetized, and through a left thoracotomy a heparinized Teflon-tipped Silastic catheter was introduced into the bronchial artery. The other end of the catheter was brought out through the chest wall and through a neck incision was introduced into the carotid artery. A reservoir filled with warm heparinized blood was connected to this shunt. The height of blood column in the reservoir was kept constant at 150 cm by adding more blood. Qbr was measured, after interrupting the carotid-bronchial artery flow, by the changes in the reservoir volume. The bronchial arterial back pressure (Pbr) was measured through the shunt when both carotid-bronchial artery and reservoir Qbr had been temporarily interrupted. The mean Qbr was 34.1 +/- 2.9 (SE) ml/min, Pbr = 17.5 +/- 3.3 cmH2O, BVR = 3.9 +/- 0.5 cmH2O X ml-1 X min, mean pulmonary arterial pressure = 21.5 +/- 3.6 cmH2O, and pulmonary capillary wedge pressure (Ppcw) = 14.3 +/- 3.7 cmH2O. We further studied the effect of increased left atrial pressure on these parameters by inflating a balloon in the left atrium. The left atrial balloon inflation increased Ppcw to 25.3 +/- 3.1 cmH2O, Qbr decreased to 21.8 +/- 2.4 ml/min (P less than 0.05), and BVR increased to 5.5 +/- 1.0 cmH2O.ml-1.min (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The role of bronchial circulation in lung abscess

We studied the anatomy of bronchial circulation in 6 sheep with multiple lung abscesses. After anesthesia, the animals were heparinized and exsanguinated. The bronchial artery, pulmonary artery, and tracheobronchial tree were filled with Batson's solution of varying colors. The cast was dissected and the anatomy was studied with a dissecting microscope as well as a scanning electron-microscope. The bronchial arteries were found to be enlarged and hypertrophied in all infected animals. The abscess cavities were surrounded with a dense vascular plexus that was being supplied exclusively by the bronchial arteries. The pulmonary capillaries were sparse and were filled entirely by the bronchial artery. The pulmonary circulation did not supply the walls of lung abscess cavity. Our findings indicate that the bronchial circulation may be more important than the pulmonary circulation in resolution and repair after certain lung infections.

Gross and subgross anatomy of bronchial circulation in sheep

The anatomy of the bronchial artery in sheep has recently been described. However, the course of the bronchial veins has not been well established. It has been suggested that the bronchial veins are the major site of fluid leakage following histamine infusion, and it has been postulated that the bronchial circulation may play a role in fluid reabsorption. We studied the anatomy of the bronchial circulation in 18 sheep with emphasis on bronchial venous drainage and bronchopulmonary communications. Following anesthesia animals were heparinized and exsanguinated. Evans blue dye was infused into the bronchial artery in six sheep and the gross and subgross anatomy of the bronchial circulation studied. In six other sheep the bronchial artery, pulmonary artery, and tracheobronchial tree were filled with Batson's solution of varying colors. The subgross anatomy was studied under a dissecting microscope, and samples were taken for scanning electron microscopy. In six separate sheep we studied the anatomy of the proximal vein by infusing dye directly into the vein and found that the extrapulmonary bronchial blood drained into the left azygos vein via a single vessel. Intrapulmonary bronchi are surrounded by a dense bronchial microvascular plexus which drains into the pulmonary vessels at the precapillary level.

Extra-alveolar vessel contribution to hydrostatic pulmonary edema in in situ dog lungs

We determined the relative contribution of larger extra-alveolar arteries and veins to hydrostatic edema in in situ dog lungs. Left lower lobe alveolar and vascular pressures were controlled in 24 open-chest, anesthetized, heparinized dogs. Zero pressure was at the lobe base. Normal blood gases were maintained by ventilating the right lung. The left lower lobe was inflated with 5% CO2 and air to an alveolar pressure of 10 or 25 cmH2O and suspended from a strain gauge, which allowed continual weight recording. Vascular pressures were raised to alveolar pressure plus lung height (zone III) before and after pulmonary arterial or venous embolization with 37- to 74-microns polystyrene beads, which isolated the larger extra-alveolar arteries or veins from alveolar vessels. The weight change occurring during the last 3 min of the 5-min hydrostatic stress was taken to represent transvascular fluid flux. At an alveolar pressure of 25 cmH2O (estimated transmural pressure 40 cmH2O), leakage from the larger extra-alveolar arteries and veins accounted for 41 and 32%, respectively, of the total transvascular fluid flux occurring after embolization. At an alveolar pressure of 10 cmH2O (estimated transmural pressure 22 cmH2O), no extra-alveolar vessel leakage occurred. However, when vascular pressures were raised to provide a transmural pressure similar to that present at the higher alveolar pressure, the same contribution from larger extra-alveolar vessels was observed.

Pulmonary effects of topical timolol

Timolol, a beta-adrenergic blocking agent, recently became available for the treatment of glaucoma. We report the occurrence of acute bronchospasm in a previously asymptomatic asthmatic patient following topical use of timolol. Therapy with the drug was discontinued, and four weeks later the patient was challenged with two drops of 0.5% timolol. A 25% decrease in forced expiratory volume at one second (FEV1) was demonstrated at one hour. The fall in FEV1 was even greater (47%) when the patient was rechallenged with four drops. We emphasize the need to avoid topical beta-adrenergic blocking agents in asthmatic patients.

Alveolar gas compression in smokers and asthmatics

To correlate the degree of alveolar gas compression with the severity of airway obstruction, we plotted separately exhaled and plethysmographic maximal-expiratory-flow-volume (MEFV) curves in each of 4 healthy nonsmokers, 4 asymptomatic smokers, and 4 asymptomatic asthmatics. Spirometry, lung volumes, single breath nitrogen plateau (Phase III), and closing volumes (Phase IV) were normal in the smokers and nonsmokers, and there were either normal or showed evidence of mild airway obstruction in the asthmatics. MEFV curves were plotted by using exhaled flow (VE) against exhaled volume (VE), and by using plethysmographic flow (VL) against plethysmographic volume (VL). These curves were utilized to construct isovolume-pressure-flow (IVPF) curves of esophageal pressure (Pes) against VE and against VL for each subject. Differences in the flow (VL minus VE) were calculated from these curves at 75% vital capacity (VC), 50% VC, and 25% VC at the same Pes in all 3 groups. At 75% VC, the mean flow difference in the asthmatic group was significantly higher than in normals (P less than 0.05); at 50% VC, it was significantly higher both in the asthmatics and the smokers (P less than 0.05); at 25% VC, there was no significant difference among the 3 groups. The mean plethysmographic forced vital capacity (FVC) exceeded exhaled FVC in all 3 groups, but the difference was significantly higher in smokers and asthmatics than in nonsmokers (P less than 0.05). These findings suggest that significant alveolar gas compression may occur at 75% VC in mild asthmatics, whereas in smokers it occurs at the middle portion of the VC.

Pulmonary injuries associated with acute sulfur dioxide inhalation

This report describes an industrial accident in which 5 previously healthy persons were acutely exposed to very high concentrations of sulfur dioxide. Of these 5 subjects, the 2 with the highest exposure died immediately; histologic examination of the lungs revealed extensive sloughing of the mucosa of large and small airways along with hemorrhagic alveolar edema. The 3 survivors were evaluated with pulmonary function tests performed at regular intervals. One subject subsequently developed symptomatic severe airway obstruction unresponsive to bronchodilators; another subject developed asymptomatic mild obstructive and restrictive disease, and the third subject continued to be asymptomatic with normal pulmonary function tests. This report severe to document the histologic features of fatal exposure to sulfur dioxide and stresses the need to follow parameters of pulmonary function in the nonfatal cases.