Lung function in Birt-Hogg-Dubé syndrome: a retrospective analysis of 96 patients

Background

Birt-Hogg-Dubé syndrome (BHD) is a rare autosomal dominant disorder caused by mutations in the FLCN gene coding for folliculin. Its clinical expression includes cutaneous fibrofolliculomas, renal tumors, multiple pulmonary cysts, and recurrent spontaneous pneumothoraces. Data on lung function in BHD are scarce and it is not known whether lung function declines over time. We retrospectively assessed lung function at baseline and during follow-up in 96 patients with BHD.

Results

Ninety-five percent of BHD patients had multiple pulmonary cysts on computed tomography and 59% had experienced at least one pneumothorax. Mean values of forced expiratory volume in 1 second (FEV₁), forced vital capacity (FVC), FEV₁/FVC ratio, and total lung capacity were normal at baseline. Mean (standard deviation) residual volume (RV) was moderately increased to 116 (36) %pred at baseline, and RV was elevated > 120%pred in 41% of cases. Mean (standard deviation) carbon monoxide transfer factor (DLco) was moderately decreased to 85 (18) %pred at baseline, and DLco was decreased < 80%pred in 33% of cases. When adjusted for age, gender, smoking and history of pleurodesis, lung function parameters did not significantly decline over a follow-up period of 6 years.

Conclusions

Cystic lung disease in BHD does not affect respiratory function at baseline except for slightly increased RV and reduced DLco. No significant deterioration of lung function occurs in BHD over a follow-up period of 6 years.

[Diagnostic difficulties of chronic pulmonary berylliosis in France]

INTRODUCTION

The epidemiology of chronic beryllium disease (CBD) in France is poorly understood. The aim of this study was to determine the number of prevalent cases of CBD in France between 2010 and 2014.

METHODS

We conducted a national survey using a specific questionnaire distributed by the professional pathology services.

RESULTS

In total, 33 CBD cases were reported in France, with a diagnosis established between 1982 and 2014. 85% (28/33) of CBD cases resulted from professional exposure and mostly concerned foundry workers (39%). A definite diagnosis defined by the association of an abnormal beryllium lymphocyte proliferation test and of a granulomatous inflammatory response in the lung, was obtained in 29/33 cases (88%). The other cases were probable CBD, defined by a granulomatous lung disease with a beryllium exposure, but without evidence of beryllium sensitisation. The diagnosis of granulomatous disease was confirmed a mean of 4 years after the end of exposure. The median delay between diagnosis of a granulomatous disease and diagnosis of CBD was 2 years (range 0-38 years). A genetic predisposition was found in 14 of 17 tested patients (82%).

CONCLUSION

In this study, we report 33 cases of CBD followed in France between 2010 and 2014. The poor understanding of CBD and the exposure leading to it, the late development after the end of exposure, the complexity of the diagnosis and the similarities with sarcoidosis may explain the small number of cases reported.

[Cryptogenic organizing pneumonia]

INTRODUCTION

Organizing pneumonia is a particular type of inflammatory reaction of the lung which gives rise to a clinico-pathological syndrome. It is called "secondary" when a cause such as an infection, a drug toxicity, or a connective tissue disease can be identified, or "cryptogenic" when no cause is identified. The clinical picture is usually characterized by the subacute onset of fever, fatigue, cough and dyspnea, with multiple subpleural areas of consolidation on thoracic imaging.

STATE OF THE ART

Organizing pneumonia is characterised by the presence of buds of endoalveolar connective tissue. These result from an injury to the alveolar epithelium, followed by the deposition of fibrin in the alveolar spaces, and the migration of fibroblasts which produce a myxoid endoalveolar matrix. A remarkable feature of organizing pneumonia is the complete disappearance of these endoalveolar buds with corticosteroid treatment, in sharp contrast with what is seen in pulmonary fibrosis. The clinical response to corticosteroids is usually prompt and excellent. Relapses are frequent but usually benign.

PERSPECTIVES AND CONCLUSION

As the clinical, imaging and pathological characteristics of organizing pneumonia are now well established, many questions remain unanswered, such as the mechanisms involved in the complete reversibility of the pulmonary lesions, and the role of steroid-sparing treatments such as immunomodulatory macrolides.

[Pulmonary lymphangioleiomyomatosis: From pathogenesis to management]

INTRODUCTION

Pulmonary lymphangioleiomyomatosis (LAM) is a rare disease affecting mainly young women.

BACKGROUND

The respiratory manifestations are characterized by a progressive cystic destruction of the lung parenchyma. Extrapulmonary involvement includes benign renal tumours called angiomyolipomas and abdominal lymphatic masses called lymphangioleiomyomas. At the pathological level, the cellular proliferation found in LAM is in part due to the presence of mutations in the tumour suppressor genes TSC1 and TSC2 (Tuberous Sclerosis Complex). These mutations lead to the activation of the mTOR pathway, which is currently the main therapeutic target. mTOR inhibitors such as sirolimus or everolimus have shown a beneficial effect on the decline in pulmonary function and a reduction of angiomyolipoma size, but are necessary in only some patients.

PERSPECTIVES

LAM cells have migratory properties mediated by the formation of new lymphatic vessels. They are also able to secrete metalloproteases, which enhance their invasiveness. Moreover, the expression of estrogen and progesterone receptors by LAM cells suggests a possible role for sex hormones in the pathogenesis of the disease.

CONCLUSION

A better understanding of mTOR-independent mechanisms would allow the development of novel therapeutic approaches.

[Idiopathic pulmonary fibrosis: recent diagnostic and therapeutic advances]

Idiopathic pulmonary fibrosis (IPF) is the most frequent of the idiopathic interstitial pneumonias. It is a progressive disorderwith a poor prognosis. Its diagnosis requires the careful exclusion of potential causes, and a pattern of usual interstitial pneumonia at high-resolution computed tomography or video-assisted surgical lung biopsy. Several recent randomized trials have profoundly modified the therapeutic management of IPF. The combination of prednisone and azathioprine, often prescribed until recently, has been shown to be harmful and is no longer indicated. N-acetylcystein, also used in the past decade, failed to show an efficacy. However, two new antifibrotic drugs, pirfenidone and nintedanib, have for the first time proven effective in slowing disease progression.

[Granulomatous lymphocytic interstitial lung disease in common variable immunodeficiency]

Common variable immunodeficiency (CVID) is the most frequent primary immune deficiency. Recurrent infections are classical consequences of CVID, but their impact has been largely reduced by immunoglobulin replacement. CVID is also associated with various inflammatory and autoimmune manifestations resulting from abnormal cellular immunity. The lungs are especially affected by a recently described entity called granulomatous lymphocytic interstitial lung disease (GLILD). GLILD currently constitutes an important cause of morbidity and mortality in these patients. It is distinct from bronchiectasis secondary to recurrent infections, and presents similarities but also striking differences with sarcoidosis.

[Respiratory bronchiolitis and respiratory bronchiolitis-associated interstitial lung disease]

The increasing use of chest CT imaging in medical practice rises the likelihood of the general practitioner to be confronted with cases of interstitial lung disease. Respiratory bronchiolitis (RB) and respiratory bronchiolitis-associated interstitial lung disease (RB-ILD) are two smoking-related lung damages that may have important implications for the patient's management. The authors present in this paper a review of current knowledge of the epidemiology, clinical features, prognosis, and treatment options of RB and RB-ILD.

[Computed tomography screening for lung cancer]

Lung cancer screening has been the focus of intense interest since the publication in 2011 of the NLST trial (National Lung Screening Trial) showing a mortality reduction in smokers undergoing 3-year screening by chest computed tomography. Although these data appear promising, many issues remain to be resolved, such as high rate of false positive cases, risk of overdiagnosis, optimal intervals between screens, duration of the screening process, feasibility, and cost. Structured screening programs appear crucial to guarantee patient information, technical quality, and multidisciplinary management. Despite these uncertainties, several guidelines already state that screening should be performed in patients at risk, whereas investigators stress that more data are needed. How should the primary care physician deal with individual patients requests? This review provides some clues on this complex issue.

Use of variability in national and regional data to estimate the prevalence of lymphangioleiomyomatosis

BACKGROUND

Understanding the true prevalence of lymphangioleiomyomatosis (LAM) is important in estimating disease burden and targeting specific interventions. As with all rare diseases, obtaining reliable epidemiological data is difficult and requires innovative approaches.

AIM

To determine the prevalence and incidence of LAM using data from patient organizations in seven countries, and to use the extent to which the prevalence of LAM varies regionally and nationally to determine whether prevalence estimates are related to health-care provision.

METHODS

Numbers of women with LAM were obtained from patient groups and national databases from seven countries (n = 1001). Prevalence was calculated for regions within countries using female population figures from census data. Incidence estimates were calculated for the USA, UK and Switzerland. Regional variation in prevalence and changes in incidence over time were analysed using Poisson regression and linear regression.

RESULTS

Prevalence of LAM in the seven countries ranged from 3.4 to 7.8/million women with significant variation, both between countries and between states in the USA. This variation did not relate to the number of pulmonary specialists in the region nor the percentage of population with health insurance, but suggests a large number of patients remain undiagnosed. The incidence of LAM from 2004 to 2008 ranged from 0.23 to 0.31/million women/per year in the USA, UK and Switzerland.

CONCLUSION

Using this method, we have found that the prevalence of LAM is higher than that previously recorded and that many patients with LAM are undiagnosed.

[Urinary incontinence due to chronic cough in interstitial lung disease]

INTRODUCTION

Urinary stress incontinence affects 10% to 30% of the female population and may have a major impact on psychosocial health. In interstitial lung disease, chronic cough may lead to development of urinary incontinence, but the prevalence and impact of this symptom are unknown.

OBJECTIVES

To determine the rate and impact of urinary stress incontinence among women with chronic cough due to interstitial lung disease.

METHODS

28 female patients with chronic cough secondary to interstitial lung disease and 15 controls were evaluated by questionnaires to determine the prevalence of cough-related urinary incontinence, its severity, and its impact on quality of life.

RESULTS

Cough-related urinary incontinence was present in 14/28 patients with interstitial lung disease and chronic cough (50%), but in only 1/15 controls (7%, p=0.005). On a 5-points quality of life scale, the median impact of urinary incontinence was 3 (minimum=1, maximal=5), and the median impact of chronic cough was 3.5. The majority of patients (64%) believed that incontinence was a natural phenomenon due to ageing, all were ashamed by this symptom and 79% were unable to mention it to their caring physician. Only one physician had previously addressed this issue.

CONCLUSION

Cough-related urinary incontinence is common in patients with interstitial lung disease and is largely overlooked. It may significantly alter quality of life. A systematic questioning by the physician would allow to promptly refer these patients for appropriate therapeutic interventions, such as perineal training.

[Pulmonary alveolar proteinosis]

Pulmonary alveolar proteinosis (PAP) is a rare, diffuse infiltrative lung disease of unknown etiology characterized by accumulation of abnormal lung surfactant in the alveoli and distal airways. Although it was first described in 1958, few large scale studies have been published. The diagnosis is conventionally based on lung biopsy and the value of less invasive procedures such as bronchoalveolar lavage (BAL) remains controversial. A multi-center retrospective study was conducted in an attempt to update epidemiological, clinical and long term outcome and to assess the usefulness of chest CT scan and BAL in the management of a large homogeneous series of 41 patients. Inclusion criteria required a clinical picture compatible with PAP and either histological confirmation, or a BAL with a milky macroscopic appearance coupled with positive staining to PAS. Mean age was 48.8 years with a 4: 1 male predominance. The prevalence of smokers (80%) and occupational exposure to various inhaled dusts (39%) was high. The clinical, roentgenographic and functional features were in keeping with previous series. Worsening dyspnea was the most common symptom. Other common manifestations were dry cough, recurrent lung infections, weight loss, finger clubbing, crackles and cyanosis. LDH serum levels were increased in 51% of cases. Lung function tests usually showed a mild restrictive ventilatory defect with hypoxemia and reduced DLCO. Chest X ray revealed bilateral ground glass opacities with consolidation or air bronchogram involving peri-hilar or lower lobes. Chest CT scan, performed in 38 patients, revealed a similar pattern in most of them with diffuse intra-alveolar ground glass opacities (33/38) and interlobular thickening (35/38), resulting in a crazy paving appearance in the typical geographic pattern (32/38). This latter aspect was highly suggestive of the diagnosis. Segmental BAL led to a definitive diagnosis in 62% and lung biopsy was only required in 38% of cases. These data suggest that careful BAL analysis can be sufficient to provide a diagnosis without the need for a lung biopsy. During follow-up, spontaneous remission or improvement was reported in 26%. Segmental (n=3) or whole lung lavage (n=22) was required in 62.5% with a favorable course (complete remission 37%, improvement 34%, stable course 21%) in 92% of the cases. In this series the overall prognosis for PAP remained good, although unpredictable.

Cryptogenic organizing pneumonia. Characteristics of relapses in a series of 48 patients. The Groupe d'Etudes et de Recherche sur les Maladles "Orphelines" Pulmonaires (GERM"O"P)

Cryptogenic organizing pneumonia (COP) is a clinicopathologic syndrome characterized by rapid resolution with corticosteroids, but frequent relapses when treatment is tapered or stopped. We retrospectively studied relapses in 48 cases of biopsy-proven COP. One or more relapses (mean 2.4 +/- 2.2) occurred in 58%. At first relapse, 68% of patients were still under treatment for the initial episode. Compared with the no-relapse group, nine patients with multiple (>/= 3) relapses had longer delays between first symptoms and treatment onset (22 +/- 17 versus 11 +/- 8 wk, p = 0.02), and elevated gamma-glutamyltransferase (124 +/- 98 versus 29 +/- 13 IU/L, p = 0.001) and alkaline phosphatase (190 +/- 124 versus 110 +/- 68 IU/L, p = 0.04) levels. Relapses did not adversely affect outcome. Corticosteroid treatment side effects occurred in 25% of patients. Standardized treatment in 14 patients allowed a reduction of prednisone cumulated doses (p < 0.05) without affecting outcome or relapse rate. We conclude that: (1) delayed treatment increases the risk of relapses; (2) mild cholestasis identifies a subgroup of patients with multiple relapses; (3) relapses do not affect outcome, and prolonged therapy to suppress relapses appears unnecessary; (4) a standardized treatment allows a reduction in steroid doses.

Tissue oxygenation and hemodynamic response to NO synthase inhibition in septic shock

The objective of the study was to evaluate the tissue oxygenation and hemodynamic effects of NOS inhibition in clinical severe septic shock. Eight patients with septic shock refractory to volume loading and high level of adrenergic support were prospectively enrolled in the study. Increasing doses of NOS inhibitors [N(G)-nitro-L-arginine-methyl ester (L-NAME) or N(G)-monomethyl-L-arginine (L-NMMA)] were administered as i.v. bolus until a peak effect = 10 mmHg on mean blood pressure was obtained or until side effects occurred. If deemed clinically appropriate, a continuous infusion of L-NAME was instituted and adrenergic support weaning attempted. The bolus administration of NOS inhibitors transiently increased mean blood pressure by 10 mm Hg in all patients. Seven out of eight patients received an L-NAME infusion, associated over 24 h with a progressive decline in cardiac index (P < 0.001) and an increase in systemic vascular resistance (P < 0.01). Partial or total adrenergic support weaning was rapidly possible in 6/8 patients. Oxygen transport decreased (P < 0.001), but oxygen consumption remained unchanged in those patients in whom it could be measured by indirect calorimetry (5/8). Blood lactate and the difference between tonometric gastric and arterial PCO2 remained unchanged. There were 4/8 ICU survivors. We conclude that nitric oxide synthase inhibition in severe septic shock was followed with a progressive correction of the vasoplegic hemodynamic disturbances with finally normalization of cardiac output and systemic vascular resistances without any demonstrable deterioration in tissue oxygenation.

Microscopic polyangiitis with alveolar hemorrhage. A study of 29 cases and review of the literature. Groupe d'Etudes et de Recherche sur les Maladies "Orphelines" Pulmonaires (GERM"O"P)

Microscopic polyangiitis (MPA) is a systemic small-vessel vasculitis primarily associated with necrotizing glomerulonephritis and pulmonary capillaritis. In this retrospective study of 29 patients with MPA and alveolar hemorrhage (AH), we characterized the pulmonary manifestations at presentation and assessed the short- and long-term outcome. AH was diagnosed when bronchoalveolar lavage was macroscopically bloody, or contained hemosiderin-laden macrophages, in the absence of lung infection or pulmonary edema. MPA was diagnosed when AH was associated with focal segmental necrotizing glomerulonephritis at kidney biopsy or pathologically proved small-vessel vasculitis. There were 17 women and 12 men, with a mean age of 55.8 +/- 16.7 years. The onset was rapidly progressive, but in 8 (28%) patients, symptoms preceded the diagnosis for more than 1 year. The most constant systemic findings associated with AH were glomerulonephritis in 28 (97%) patients; fever (62%); myalgia and arthralgia (52%); weight loss (45%); ear, nose, and throat symptoms (31%); and skin involvement (17%). Lung opacities were bilateral in 26 (90%) patients, most frequently involving the lower part of the lungs. Bronchoalveolar lavage, performed in 27 patients, was hemorrhagic in 25 (93%), and contained numerous siderophages in others. Most patients were severely anemic (mean hemoglobin, 8.1 +/- 1.8 g/dL). ANCA, present in 27 (93%) patients, gave a perinuclear (14), cytoplasmic (11), or mixed (1) pattern. Mean serum creatinine level was 407 +/- 415 mumol/L. Renal biopsy confirmed the presence of necrotizing glomerulonephritis in 27 patients. Patients were treated with corticosteroids (100%), cyclophosphamide (79%), plasmapheresis (24%), dialysis (28%), and mechanical ventilation (10%). The overall mortality rate was 31% (9 patients). Deaths were related to vasculitis (5 patients) or side effects of treatment (4). Deaths were more frequent in aged or mechanically ventilated patients. The 5-year survival rate was 68%. The recovery of respiratory function among survivors was clinically considered complete in 20 (69%) patients. However, 7 patients (24%) had persistent alterations on pulmonary function tests. Of the 11 patients who had relapses, 2 died from AH.

Pulmonary lymphangioleiomyomatosis. A study of 69 patients. Groupe d'Etudes et de Recherche sur les Maladies "Orphelines" Pulmonaires (GERM"O"P)

Pulmonary lymphangioleiomyomatosis (LAM) is a rare disorder of unknown cause characterized by peribronchial, perivascular, and perilymphatic proliferation of abnormal smooth muscle cells leading to cystic lesions. The hypothesis of hormonal dependence and the effectiveness of hormonal therapy have not yet been demonstrated conclusively, and the prevalence of extrathoracic manifestations and the survival of patients with LAM are somewhat contradictory. A multicentric retrospective study was conducted in an attempt to describe better the initial features, the diagnostic procedures, the associated lesions, and, above all, the management and course of LAM in a large homogeneous series of 69 stringently selected patients, with a majority of cases diagnosed since 1990. The aim of the study, based on a review of the literature, also was to provide a comprehensive view of this uncommon disease. The clinical features were in keeping with previous studies, but we found that exertional dyspnea and pneumothorax were the most common features, and chylous involvement was less frequent. LAM was diagnosed after menopause in about 10% of cases. The onset of LAM occurred during pregnancy in 20% of cases, and a clear exacerbation of LAM was observed in 14% of cases during pregnancy. Pulmonary LAM was diagnosed on lung histopathology in 83% of cases, but renal angiomyolipoma, observed in 32% of our patients, may be a useful diagnostic criterion when associated with typical multiple cysts on chest CT scan or with chylous effusion. Chest CT scan was more informative than chest X-ray (normal in 9% of cases), and may be indicated in spontaneous pneumothorax or renal angiomyolipoma in women of childbearing age. About 40% of the patients had a normal initial spirometry, while an obstructive ventilatory defect (44%), a restrictive ventilatory defect (23%), was observed in other patients. Initial diffusing capacity for carbon monoxide was frequently decreased (82%). Hormonal therapy was administered in 57 patients, but a clear > or = 15% improvement of FEV1 was observed in only 4 evaluable patients, treated with tamoxifen and progestogens (n = 2), progestogen (n = 1), and oophorectomy (n = 1). Probably 1 of the most urgent needs for clinical research in LAM is to test the currently available hormonal treatments in the context of international multicenter prospective controlled studies. Pleurodesis was performed in 40 patients. Lung transplantation was performed in 13 patients, 7.8 +/- 5.2 years after onset of LAM, in whom the mean FEV1 was 0.57 +/- 0.15 L. After a follow-up of 2.3 +/- 2.2 years, 9 patients were alive. Mean follow-up from onset of disease to either death or closing date was 8.2 +/- 6.3 years. Overall survival was better than usually reported in LAM, and Kaplan-Meier plot showed survival probabilities of 91% after 5 years, 79% after 10 years, and 71% after 15 years of disease duration.

Hypoxic contraction of small pulmonary arteries from normal and endotoxemic rats: fundamental role of NO

The present study was aimed at examining the role of nitric oxide (NO) in the hypoxic contraction of isolated small pulmonary arteries (SPA) in the rat. Animals were treated with either saline (sham experiments) or Escherichia coli lipolysaccharide [LPS, to obtain expression of the inducible NO synthase (iNOS) in the lung] and killed 4 h later. SPA (300- to 600-micrometer outer diameter) were mounted as rings in organ chambers for the recording of isometric tension, precontracted with PGF2alpha, and exposed to either severe (bath PO2 8 +/- 3 mmHg) or milder (21 +/- 3 mmHg) hypoxia. In SPA from sham-treated rats, contractions elicited by severe hypoxia were completely suppressed by either endothelium removal or preincubation with an NOS inhibitor [NG-nitro-L-arginine methyl ester (L-NAME), 10(-3) M]. In SPA from LPS-treated rats, contractions elicited by severe hypoxia occurred irrespective of the presence or absence of endothelium and were largely suppressed by L-NAME. The milder hypoxia elicited no increase in vascular tone. These results indicate an essential role of NO in the hypoxic contractions of precontracted rat SPA. The endothelium independence of HPV in arteries from LPS-treated animals appears related to the extraendothelial expression of iNOS. The severe degree of hypoxia required to elicit any contraction is consistent with a mechanism of reduced NO production caused by a limited availability of O2 as a substrate for NOS.

L-canavanine, an inhibitor of inducible nitric oxide synthase, improves venous return in endotoxemic rats

OBJECTIVE

To investigate the hemodynamic effects of L-canavanine (an inhibitor of inducible, but not of constitutive, nitric oxide synthase) in endotoxic shock.

DESIGN

Controlled, randomized, experimental study.

SETTING

Animal laboratory.

SUBJECTS

Wistar rats.

INTERVENTIONS

Rats were anesthetized with pentobarbital, and hemodynamically monitored. One hour after an intravenous challenge with 5 mg/kg of Escherichia coli endotoxin, the rats were randomized to receive a continuous infusion of either L-canavanine (20 mg/kg/hr; n = 8) or vehicle only (isotonic saline, n = 11). In all animals, the infusion was given over 5 hrs at a rate of 2 mL/kg/hr. These experiments were repeated in additional rats challenged with isotonic saline instead of endotoxin (sham experiments).

MEASUREMENTS AND MAIN RESULTS

Arterial blood pressure, heart rate, thermodilution cardiac output, central venous pressure, mean systemic filling pressure, urine output, arterial blood gases, blood lactate concentration, and hematocrit were measured. In sham experiments, hemodynamic stability was maintained throughout and L-canavanine had no detectable effect. Animals challenged with endotoxin and not treated with L-canavanine developed progressive hypotension and low cardiac output. After 6 hrs of endotoxemia, both central venous pressure and mean systemic filling pressure were significantly below their baseline values, indicating relative hypovolemia as the main determinant of reduced cardiac output. In endotoxemic animals treated with L-canavanine, hypotension was less marked, while cardiac output, central venous pressure, and mean systemic filling pressure were maintained throughout the experiment. L-canavanine had no effect on the time-course of hematocrit. L-canavanine significantly increased urine output and reduced the severity of lactic acidosis.

CONCLUSIONS

Six hours after an endotoxin challenge in rats, low cardiac output develops, which appears to be primarily related to relative hypovolemia. L-canavanine, a selective inhibitor of the inducible nitric oxide synthase, increases the mean systemic filling pressure, thereby improving venous return, under these conditions.

Safety of combined heat and moisture exchanger filters in long-term mechanical ventilation

STUDY OBJECTIVE

To evaluate the safety of a combined heat and moisture exchanger filter (HMEF) for the conditioning of inspired gas in long-term mechanical ventilation (MV).

DESIGN

Randomized controlled trial.

SETTING

Medical ICU in a large teaching hospital.

PATIENTS

One hundred fifteen consecutive patients who required > or = 48 h of MV.

INTERVENTIONS

Patients were randomized at intubation time (day 1) to receive inspired gas conditioned either by a water-bath humidifier heated at 32 degrees C (HWBH) or by an HMEF (Hygroster; DAR; Mirandola, Italy).

MEASUREMENTS AND MAIN RESULTS

The two study groups were comparable in terms of primary pathologic condition at the time of hospital admission, disease severity as measured by the Simplified Acute Physiology Score, and ICU mortality. They did not differ with respect to ventilator days per patient (mean +/- SD: HMEF, 7.6 +/- 6.5; HWBH, 7.8 +/- 5.8), incidence of endotracheal tube obstruction (HMEF, 0/59; HWBH, 1/56), and incidence of hypothermic episodes (HMEF, five; HWBH, two). In 41 patients receiving MV for > or = 5 days, the morphologic integrity of respiratory epithelium was evaluated on day 1 and day 5, using a cytologic examination of tracheal aspirate smears. The state of ciliated epithelium was scored on a scale from 0 (poorest integrity) to 1,200 (maximum integrity), according to a well-described method. In both patient groups, the scores slightly but significantly decreased from day 1 to day 5 (mean +/- SD: HWBH, from 787 +/- 104 to 745 +/- 88; HMEF, from 813 +/- 79 to 739 +/- 62; p < 0.01 for both groups); there were no statistically significant differences between groups.

CONCLUSIONS

These data indicate acceptable safety of HMEFs of the type used in the present study for long-term mechanical ventilation.

Endothelin-1 does not mediate the endothelium-dependent hypoxic contractions of small pulmonary arteries in rats

Various pulmonary artery preparations in vitro demonstrate sustained endothelium-dependent contractions upon hypoxia. To determine whether endothelin-1 could mediate this phenomenon, we examined the effect of bosentan, a new antagonist of both the ETA and ETB subtypes of the endothelin receptor. Small (300 pm) pulmonary arteries from rats were mounted on a myograph, precontracted with prostaglandin F2 alpha and exposed to hypoxia (PO2, 10 to 15 mm Hg, measured on-line) for 45 min. Endothelium-intact control rings exhibited a biphasic response, with a transient initial vasoconstriction (phase 1) followed by a second slowly developing sustained contraction (phase 2). Expressed in percent of the maximal response to 80 mmol/L KCl, the amplitudes of phase 1 (peak tension) and 2 (tension after 45 min of hypoxia) averaged 37 +/- 12% and 17 +/- 14%, respectively (n = 11). In endothelium-denuded rings, phase 1 persisted while the amplitude of phase 2 was reduced to 2 +/- 12% (p < 0.05, n = 8), showing the endothelium dependence of this contraction. Neither phase was significantly decreased in rings treated with 10(-5) mmol/L bosentan (38 +/- 15% and 17 +/- 12%, respectively, n = 6). The PO2 threshold for onset of hypoxic contraction was not significantly different among these three groups and averaged 32 +/- 24 mm Hg. In a separate experiment, we assessed the inhibitory effect of 10(-5) mol/L bosentan on the response to 10(-8) mol/L endothelin-I. Rings treated for 45 min with 10(-8) mol/L endothelin-1 alone exhibited a maximal contraction of 75 +/- 27% (n = 6). This was reduced to 4 +/- 17% (p < 0.01, n = 6) in rings treated with both 10(-8) mol/L endothelin-1 and 10(-5) mol/L bosentan. We conclude that complete blockade of all endothelin receptor subtypes has no effect on either endothelium-dependent or -independent hypoxic contractions in this preparation. This suggests that endothelial factors other than endothelin-I mediate the acute hypoxic contractions of small pulmonary arteries in the rat.