Evidence for chronic inflammation as a component of the interstitial lung disease associated with progressive systemic sclerosis

Helium-oxygen reduces work of breathing in mechanically ventilated patients with chronic obstructive pulmonary disease

OBJECTIVE

To evaluate whether helium-oxygen mixture reduces inspiratory work of breathing (WOB) in sedated, paralyzed, and mechanically ventilated patients with acute exacerbation of chronic obstructive pulmonary disease (COPD).

DESIGN AND SETTING

Open, prospective, randomized, crossover study in the medical intensive care unit in a university hospital.

PATIENTS AND PARTICIPANTS

23 patients admitted for acute exacerbation of COPD and mechanically ventilated.

MEASUREMENTS

Total WOB (WOBt), elastic WOB (WOBel), resistive WOB (WOBres), and WOB due to PEEPi (WOBPeepi) were measured. Static intrinsic positive end expiratory pressure (PEEPi), static compliance (Crs), inspiratory resistance (Rins), inspiratory (tinsp) and expiratory time constant (texp) were also measured. These variables were compared between air-oxygen and helium-oxygen mixtures.

RESULTS

WOBt significantly decreased with helium-oxygen (2.34+/-1.04 to 1.85+/-1.01 J/l, p<0.001). This reduction was significant for WOBel (1.02+/-0.61 J/l to 0.87+/-0.47, p<0.01), WOBPeepi (0.77+/-0.38 J/l to 0.54+/-0.38, p<0.001), and WOBres (0.55+/-0.19 J/l to 0.44+/-0.24, p<0.05). PEEPi, Rins, tinsp and texp significantly decreased. Crs was unchanged.

CONCLUSIONS

Helium-oxygen mixture decreases WOB in mechanically ventilated COPD patients. Helium-oxygen mixture could be useful to reduce the burden of ventilation.

Ligands of the peripheral benzodiazepine receptor have therapeutic effects in pneumopathies in vivo

In this study, we documented the effects of different peripheral benzodiazepine receptor (PBR) ligands: PK 11195, Ro5-4864 and the newly described SSR 180575 on the development of pulmonary inflammation in vivo. To this aim, we used MRL/lpr mice that develop pathological signs similar to the human lupus erythematosus (LE) signs. We found that a chronic treatment (at 3 mg/kg per i.p. for 30 days) with PBR ligands had a significant beneficial therapeutic action and decreased the inflammatory pulmonary responses and alveolitis onset. When analyzing PBR expression in inflamed tissues, we observed that in addition to the infiltrated leukocytes, PBR was expressed in the bronchial epithelium, and especially we evidenced for the first time that PBR in expressed in Clara cells. Interestingly, we observed that PBR expression in those cells was reduced when MRL/lpr mice developed the pathology and restored upon PBR ligand treatment. These original findings support a role of PBR in pulmonary inflammatory process and suggest new therapeutic applications in auto immune disorders for specific potent PBR ligands.

Effects of helium-oxygen on respiratory mechanics, gas exchange, and ventilation-perfusion relationships in a porcine model of stable methacholine-induced bronchospasm

OBJECTIVE

To explore the consequences of helium/oxygen (He/O(2)) inhalation on respiratory mechanics, gas exchange, and ventilation-perfusion (VA/Q) relationships in an animal model of severe induced bronchospasm during mechanical ventilation.

DESIGN

Prospective, interventional study.

SETTING

Experimental animal laboratory, university hospital.

INTERVENTIONS

Seven piglets were anesthetized, paralyzed, and mechanically ventilated, with all ventilator settings remaining constant throughout the protocol. Acute stable bronchospasm was obtained through continuous aerosolization of methacholine. Once steady-state was achieved, the animals successively breathed air/O(2) and He/O(2) (FIO(2) 0.3), or inversely, in random order. Measurements were taken at baseline, during bronchospasm, and after 30 min of He/O(2) inhalation.

RESULTS

Bronchospasm increased lung peak inspiratory pressure (49+/-6.9 vs 18+/-1 cm H(2)O, P<0.001), lung resistance (22.7+/-1.5 vs 6.8+/-1.5 cm H(2)O x l(-1).s, P<0.001), dynamic elastance (76+/-11.2 vs 22.8+/-4.1 cm H(2)O x l(-1), P<0.001), and work of breathing (1.51+/-0.26 vs 0.47+/-0.08, P<0.001). Arterial pH decreased (7.47+/-0.06 vs 7.32+/-0.06, P<0.001), PaCO(2) increased, and PaO(2) decreased. Multiple inert gas elimination showed an absence of shunt, substantial increases in perfusion to low VA/Q regions, and dispersion of VA/Q distribution. He/O(2) reduced lung resistance and work of breathing, and worsened hypercapnia and respiratory acidosis.

CONCLUSIONS

In this model, while He/O(2) improved respiratory mechanics and reduced work of breathing, hypercapnia and respiratory acidosis increased. Close attention should be paid to monitoring arterial blood gases when He/O(2) is used in mechanically ventilated acute severe asthma.

Elevated levels of leukotriene B4 and leukotriene E4 in bronchoalveolar lavage fluid from patients with scleroderma lung disease

OBJECTIVE

The leukotrienes are a family of arachidonic acid-derived lipid mediators with proinflammatory and profibrotic properties. The aim of this study was to analyze the role of leukotriene B(4) (LTB(4)) and LTE(4) in the pathogenesis of scleroderma lung disease (SLD).

METHODS

Nineteen systemic sclerosis (SSc) patients with SLD, 11 SSc patients without SLD, and 10 healthy controls were studied. Bronchoalveolar lavage (BAL) fluid was obtained during routine bronchoscopy of the right middle lobe in all study subjects. Levels of LTB(4) and LTE(4) were measured using enzyme immunoassay kits.

RESULTS

Levels of LTB(4) and LTE(4) were significantly higher in SSc patients with SLD (251 +/- 170 pg/ml and 479 +/- 301 pg/ml, respectively), than those in patients without SLD (114 +/- 86 and 159 +/- 149 pg/ml) and those in normal controls (86 +/- 49 and 110 +/- 67 pg/ml). In the total group of patients with SSc, levels of both leukotrienes correlated positively with the total number of cells in the BAL fluid and correlated negatively with the forced vital capacity. After intravenous pulse therapy with cyclophosphamide in 6 patients, there was a significant reduction in the concentration of LTB(4) (from 380 +/- 196 pg/ml to 155 +/- 123 pg/ml) but no significant difference in the levels of LTE(4) (from 697 +/- 325 pg/ml to 418 +/- 140 pg/ml).

CONCLUSION

Our findings show that LTB(4) and LTE(4) levels are elevated in SSc patients with SLD and correlate with parameters of inflammation in the lungs. These results indicate that leukotrienes may contribute to the pathogenesis of SLD and may represent a new therapeutic target.

Helium/oxygen mixture reduces the work of breathing at the end of the weaning process in patients with severe chronic obstructive pulmonary disease

OBJECTIVE

To test the hypothesis that helium/oxygen mixture can reduce the work of breathing at the end of the weaning process in patients with chronic obstructive pulmonary disease.

DESIGN

Prospective, randomized, crossover study.

SETTING

Two medical intensive care units at two university tertiary care centers.

PATIENTS

Thirteen patients with chronic obstructive pulmonary disease evaluated just before and after extubation.

INTERVENTIONS

Helium/oxygen and air/oxygen mixtures were administered sequentially, for 20 mins each, in a randomized order, just before extubation. It was possible to repeat the study after extubation in five patients.

MEASUREMENTS AND MAIN RESULTS

Before extubation, the helium/oxygen mixture induced no significant variation in the breathing pattern. By contrast, it reduced the work of breathing from 1.442 +/- 0.718 J/L (mean +/- sd) to 1.133 +/- 0.500 J/L (p <.05). This reduction was explained mainly by a reduction in the resistive component of the work of breathing from 0.662 +/- 0.376 to 0.459 +/- 0.256 J/L (p <.01). We also observed a slight reduction in the intrinsic positive end-expiratory pressure from 2.9 +/- 2.1 cm H(2)O to 2.1 +/- 1.8 cm H(2)O (p <.05). Similar results were also observed after extubation in five patients in whom the repetition of the study was possible.

CONCLUSIONS

In spontaneously breathing intubated patients with chronic obstructive pulmonary disease recovering from an acute exacerbation, helium/oxygen mixture reduces the work of breathing as well as intrinsic positive end-expiratory pressure without modifying the breathing pattern.

Interstitial lung disease in scleroderma

Pulmonary fibrosis occurs most patients who have scleroderma. It progresses to severe restrictive lung disease in about 15% of patients and remains a major cause of death in this disease. Risks for developing pulmonary fibrosis include diffuse cutaneous scleroderma and anti-Scl-70 antibodies, and risks for developing progressive pulmonary fibrosis and death include low pulmonary function test results at presentation and lung inflammation. Early evaluation of the extent and severity of pulmonary fibrosis and the presence of lung inflammation is key, so that therapy can be given to patients who are at higher risk of progressive pulmonary fibrosis before they develop severe functional impairment occurs. Evaluation often includes pulmonary function tests, HRCT of the lungs, Doppler echocardiogram, and bronchoalveolar lavage. For patients who are unwilling or unable to participate in therapeutic trials that target pulmonary fibrosis in scleroderma, therapy with oral or intravenous cyclophosphamide is often given.

Effects of positive end-expiratory pressure on gas exchange and expiratory flow limitation in adult respiratory distress syndrome

OBJECTIVE

To assess the effects of different positive end-expiratory pressure (PEEP) levels (0, 5, 10, and 15 cm H2O) on tidal expiratory flow limitation (FL), regional intrinsic positive end-expiratory pressure (PEEPi) inhomogeneity, alveolar recruited volume (Vrec), respiratory mechanics, and arterial blood gases in mechanically ventilated patients with acute respiratory distress syndrome (ARDS).

DESIGN

Prospective clinical study.

SETTING

Multidisciplinary intensive care unit of a university hospital.

PATIENTS

Thirteen sedated, mechanically ventilated patients during the first 2 days of ARDS.

INTERVENTIONS

Detection of tidal FL and evaluation of total dynamic PEEP (PEEPt,dyn), total static PEEP (PEEPt,st), respiratory mechanics, and Vrec from pressure, flow, and volume traces provided by the ventilator. The average (+/-sd) tidal volume was 7.1 +/- 1.5 mL/kg, the total cycle duration was 2.9 +/- 0.45 secs, and the duty cycle was 0.35 +/- 0.05.

MEASUREMENTS

Tidal FL was assessed using the negative expiratory pressure technique. Regional PEEPi inhomogeneity was assessed as the ratio of PEEPt,dyn to PEEPt,st (PEEPi inequality index), and Vrec was quantified as the difference in lung volume at the same airway pressure between quasi-static inflation volume-pressure curves on zero end-expiratory pressure (ZEEP) and PEEP.

RESULTS

On ZEEP, seven patients exhibited FL amounting to 31 +/- 8% of tidal volume. They had higher PEEPt,st and PEEPi,st ( p<.001) and lower PEEPi inequality index ( p<.001) than the six nonflow-limited (NFL) patients. Two FL patients became NFL with PEEP of 5 cm H2O and five with PEEP of 10 cm H2O. In both groups, PaO2 increased progressively with PEEP. In the FL group, there was a significant correlation of PaO2 to PEEPi inequality index ( p=.002). For a given PEEP, Vrec was greater in NFL than FL patients, and a significant correlation of Pao to Vrec ( p<.001) was found only in the NFL group.

CONCLUSIONS

We conclude that on ZEEP, tidal FL is common in ARDS patients and is associated with greater regional PEEPi inhomogeneity than in NFL patients. With PEEP of 10 cm H2O, flow limitation with concurrent cyclic dynamic airway compression and re-expansion and the risk of "low lung volume injury" were absent in all patients. In FL patients, PEEP induced a significant increase in PaO2, mainly because of the reduction of regional PEEPi inequality, whereas in the NFL group, arterial oxygenation was improved satisfactorily because of alveolar recruitment.

Successful determination of lower inflection point and maximal compliance in a population of patients with acute respiratory distress syndrome

OBJECTIVE

To compare the ease and efficacy of two commonly used methods for choosing optimal positive end-expiratory pressure (PEEP) in patients with acute respiratory distress syndrome: a static pressure-volume curve to determine the lower inflection point (P(flex)) and the "best PEEP" (PEEP(best)) as determined by the maximal compliance curve.

DESIGN

Prospective study.

SETTING

Medical and respiratory intensive care units of university-associated tertiary care hospital.

PATIENTS

Twenty-eight patients on mechanical ventilation with acute respiratory distress syndrome.

INTERVENTIONS

A critical care attending physician or fellow and an experienced respiratory therapist attempted to obtain both static pressure-volume curves and maximal compliance curves on 28 patients with acute respiratory distress syndrome by using established methods that were practical to everyday use. The curves then were used to determine both P(flex) and PEEP(best), and the results were compared.

MEASUREMENT AND MAIN RESULTS

Our results showed at least one value for optimal PEEP was obtained in 26 of 28 patients (93%). P(flex) was determined in 19 (68%), a PEEP(best) in 24 (86%), and both values in 17 (61%). In patients who had both P(flex) and PEEP(best) determined, there was a close concordance (+/-3 cm H2O) in 60%. When the values of P(flex) and PEEP(best) were interpreted by two additional investigators, there was unanimous agreement on the P(flex) (+/-3) only 64% of the time. There was agreement on the value of PEEP(best) 93% of the time.

CONCLUSIONS

Our data show that optimal PEEP, as determined by a pressure-volume curve and a maximal compliance curve, are sometimes unobtainable by practical means but, when obtained, often correspond. A maximal compliance is more often identified, has less interobserver variability, and poses less risk to the patient. We conclude that determining optimal PEEP by maximal static compliance may be easier to measure and more frequently obtained at the bedside than by using a static pressure-volume curve.

Pressure-volume curves in acute respiratory distress syndrome: clinical demonstration of the influence of expiratory flow limitation on the initial slope

The presence of an initial segment with a low compliance on the static pressure-volume (PV) curve in patients with acute respiratory distress syndrome (ARDS) indicates that some lung compartments do not initially receive insufflated gas. We tested the hypothesis that an uneven distribution of time constants, producing a "slow compartment," was in part responsible for the change in compliance between the initial and the intermediate segment of the PV curve. In 16 patients with ARDS submitted to mechanical ventilation in volume-controlled mode with a supportive respiratory rate of 15 breaths/minute, we constructed the static PV curve on the first day of respiratory support and determined the intrinsic positive end-expiratory pressure (PEEPi4) during a prolonged end-expiratory pause (4 seconds). We also measured the volume of a "slow compartment" during a prolonged expiration (> 6 seconds), and determined an external PEEP (PEEPe) suppressing PEEPi4. Among the 16 patients studied, 11 exhibited a low inflection point, associated with a "slow compartment" of 172 +/- 83 ml, responsible for a PEEPi4 of 3 +/- 2 cm H2O. Conversely, the five remaining patients had a linear PV curve, associated with a minimal "slow compartment" of 28 +/- 10 ml, responsible for a negligible PEEPi4. We observed that individual slopes of the initial segment of the PV curve were inversely and significantly correlated with the proportion of the "slow compartment" (r = -0.85). We concluded that the shape of the inspiratory PV curve in ARDS might be dependent on the presence of a "slow compartment," and demonstrated that a low external PEEP appeared sufficient to achieve a substantial mechanical improvement in clinical practice.

Long-term effects of spontaneous breathing during ventilatory support in patients with acute lung injury

Improved gas exchange has been observed during spontaneous breathing with airway pressure release ventilation (APRV) as compared with controlled mechanical ventilation. This study was designed to determine whether use of APRV with spontaneous breathing as a primary ventilatory support modality better prevents deterioration of cardiopulmonary function than does initial controlled mechanical ventilation in patients at risk for acute respiratory distress syndrome (ARDS). Thirty patients with multiple trauma were randomly assigned to either breathe spontaneously with APRV (APRV Group) (n = 15) or to receive pressure-controlled, time-cycled mechanical ventilation (PCV) for 72 h followed by weaning with APRV (PCV Group) (n = 15). Patients maintained spontaneous breathing during APRV with continuous infusion of sufentanil and midazolam (Ramsay sedation score [RSS] of 3). Absence of spontaneous breathing (PCV Group) was induced with sufentanil and midazolam (RSS of 5) and neuromuscular blockade. Primary use of APRV was associated with increases (p < 0.05) in respiratory system compliance (CRS), arterial oxygen tension (PaO2), cardiac index (CI), and oxygen delivery (DO2), and with reductions (p < 0.05) in venous admixture (QVA/QT), and oxygen extraction. In contrast, patients who received 72 h of PCV had lower CRS, PaO2, CI, DO2, and Q VA/Q T values (p < 0.05) and required higher doses of sufentanil (p < 0.05), midazolam (p < 0.05), noradrenalin (p < 0.05), and dobutamine (p < 0.05). CRS, PaO2), CI and DO2 were lowest (p < 0.05) and Q VA/Q T was highest (p < 0.05) during PCV. Primary use of APRV was consistently associated with a shorter duration of ventilatory support (APRV Group: 15 +/- 2 d [mean +/- SEM]; PCV Group: 21 +/- 2 d) (p < 0.05) and length of intensive care unit (ICU) stay (APRV Group: 23 +/- 2 d; PCV Group: 30 +/- 2 d) (p < 0.05). These findings indicate that maintaining spontaneous breathing during APRV requires less sedation and improves cardiopulmonary function, presumably by recruiting nonventilated lung units, requiring a shorter duration of ventilatory support and ICU stay.

Intrinsic positive end-expiratory pressure in mechanically ventilated patients with and without tidal expiratory flow limitation

OBJECTIVE

To assess static intrinsic positive end-expiratory pressure (PEEPi,st) and expiratory flow limitation (FL) in 32 consecutive mechanically ventilated patients with acute respiratory failure (ARF), using a commercial ventilator with an incorporated device that allows the application of a negative expiratory pressure (NEP).

DESIGN

Prospective clinical study.

SETTING

Multidisciplinary intensive care unit of a university hospital.

PATIENTS

Thirty-two consecutive ventilated patients with ARF of various etiologies.

INTERVENTIONS

Evaluation of respiratory mechanics, PEEPi,st, and FL from pressure, flow, and volume traces provided by the ventilator.

MEASUREMENTS

Peak airway pressure, PEEPi,st, dynamic elastance, and interrupter resistance were measured in relaxed patients in a supine position. Comparison of tidal flow-volume curves before and during the application of an NEP of 5 cm H2O was used to assess tidal expiratory FL.

RESULTS

Twelve of 32 patients studied exhibited tidal expiratory FL, which was detected by the absence of increase in expiratory flow despite application of an NEP over the entire or part of the baseline expiratory flow-volume curve. All patients exhibited PEEPi,st, which amounted to 1.2 +/- 0.9 cm H2O (mean +/- SD) in the 20 non-FL patients and 7.1 +/- 2.8 cm H2O in the 12 FL patients (p < 0.00001). The majority of patients with ARF resulting from underlying lung disease (11 of 13) had FL and a PEEPi,st > 4 cm H2O, whereas in patients with ARF of extrapulmonary origin, PEEPi,st was always < 4 cm H2O and only one grossly obese patient exhibited FL. Based on multiple regression analysis, in non-FL patients, PEEPi,st correlated significantly only with minute ventilation, whereas in FL patients PEEPi,st correlated significantly with peak airway pressure.

CONCLUSIONS

Because all the patients exhibited PEEPi,st and 12 of 32 patients (38%) also had FL, the authors conclude that the assessment of these variables at the bedside could provide useful information concerning respiratory mechanics in mechanically ventilated patients.

Contribution of expiratory muscle pressure to dynamic intrinsic positive end-expiratory pressure: validation using the Campbell diagram

In spontaneously breathing (SB) patients expiratory muscle contraction leads to an overestimation of dynamic intrinsic PEEP (PEEP(i),dyn). To quantify this overestimation, PEEP(i),dyn measured with the esophageal balloon technique was corrected for the increase in Pga over the course of expiration (Pga,exp rise), for the whole decay of Pga during inspiration (Pga,total decay) or for the part of Pga decay restricted between the onset of inspiratory effort and the point of zero flow (Pga,zf decay). Corrections were compared with the reference PEEP(i),dyn (PEEP(i),dyn ref ), calculated by using the Campbell diagram. In 15 ventilator-dependent, SB, and actively expiring patients, we found that the difference PEEP(i),dyn - Pga, total decay (mean +/- SD, 5.7 +/- 1.9 cm H(2)O) was quite similar to PEEP(i),dyn ref (5.3 +/- 1.9 cm H(2)O). Their mean difference was 0. 37 cm H(2)O with limits of agreement -0.09 to 0.83 cm H(2)O, indicating strong agreement between these methods. PEEP(i),dyn - Pga, exp rise (6.0 +/- 2.1 cm H(2)O) was also similar to PEEP(i),dyn ref. Their mean difference was 0.72 cm H(2)O with limits of agreement -1. 69 to 3.13 cm H(2)O, indicating good agreement. In contrast, mean difference of PEEP(i),dyn - Pga,zf decay and PEEP(i),dyn ref was 3. 14 cm H(2)O with limits of agreement -0.46 to 6.74 cm H(2)O, indicating lack of agreement. The error in measurement due to the subtraction of Pga,zf decay from PEEP(i),dyn (i.e., [PEEP(i),dyn - Pga,zf decay] - PEEP(i),dyn ref ) was proportional to the intensity of expiratory muscle contraction, as expressed by the Pga,exp rise (r = 0.903, p < 0.001). We conclude that in actively expiring patients an adequate correction of PEEP(i),dyn for the overestimation caused by expiratory muscle contraction can be made by subtracting either Pga,total decay or Pga,exp rise from PEEP(i), dyn, the former achieving the best performance.

Effects of helium-oxygen on intrinsic positive end-expiratory pressure in intubated and mechanically ventilated patients with severe chronic obstructive pulmonary disease

OBJECTIVE

To test the hypothesis that replacing 70:30 nitrogen: oxygen (Air-O2) with 70:30 helium:oxygen (He-O2) can decrease dynamic hyperinflation ("intrinsic" positive end-expiratory pressure) in mechanically ventilated patients with chronic obstructive pulmonary disease (COPD), and to document the consequences of such an effect on arterial blood gases and hemodynamics.

DESIGN

Prospective, interventional study.

SETTING

Medical intensive care unit, university tertiary care center.

PATIENTS

Twenty-three intubated, sedated, paralyzed, and mechanically ventilated patients with COPD enrolled within 36 hrs after intubation.

INTERVENTIONS

Measurements were taken at the following time points, all with the same ventilator settings: a) baseline; b) after 45 mins with He-O2; c) 45 mins after return to Air-O2. The results were then compared to those obtained in a test lung model using the same ventilator settings. MAIN RESULTS (MEAN + SD): Trapped lung volume and intrinsic positive end-expiratory pressure decreased during He-O2 ventilation (215+/-125 mL vs. 99+/-15 mL and 9+/-2.5 cm H2O vs. 5+/-2.7 cm H2O, respectively; p < .05). Likewise, peak and mean airway pressures declined with He-O2 (30+/-5 cm H2O vs. 25+/-6 cm H2O and 8+/-2 cm H2O vs. 7+/-2 cm H2O, respectively; p < .05). These parameters all rose to their baseline values on return to Air-O2 (p < .05 vs. values during He-O2). These results were in accordance with those obtained in the test lung model. There was no modification of arterial blood gases, heart rate, or mean systemic arterial blood pressure. In 12/23 patients, a pulmonary artery catheter was in place, allowing hemodynamic measurements and venous admixture calculations. Switching to He-O2 and back to Air-O2 had no effect on pulmonary artery pressures, right and left ventricular filling pressures, cardiac output, pulmonary and systemic vascular resistance, or venous admixture.

CONCLUSION

In mechanically ventilated COPD patients with intrinsic positive end-expiratory pressure, the use of He-O2 can markedly reduce trapped lung volume, intrinsic positive end-expiratory pressure, and peak and mean airway pressures. No effect was noted on hemodynamics or arterial blood gases. He-O2 might prove beneficial in this setting to reduce the risk of barotrauma, as well as to improve hemodynamics and gas exchange in patients with very high levels of intrinsic positive end-expiratory pressure.

Bacterial superantigen staphylococcal enterotoxin B induces interstitial pneumonia in SCID mice reconstituted with peripheral blood mononuclear cells from collagen vascular disease patients

To investigate whether superantigens induce interstitial pneumonia associated with collagen vascular disease (CVD), staphylococcal enterotoxin B (SEB) was intratracheally administered to SCID mice reconstituted with peripheral blood mononuclear cells (PBMCs) from CVD patients that suffered lung complications. Although a slight accumulation of inflammatory cells into the perivascular area was seen in the lungs of SCID mice injected with PBMCs from CVD patients or healthy donors, SEB administration significantly increased the severity of inflammation in the lungs of SCID mice that received CVD patient PBMCs. Furthermore, human leukocytes were detected by immunohistochemistry in the lungs of SCID mice that received SEB after reconstitution with PBMCs from CVD patients but not in other groups of SCID mice. CD45RO(+) memory T cells comprised the majority of infiltrating human leukocytes. These results suggest the possibility that external superantigens may induce the development of interstitial pneumonia in patients that have a genetic background predisposition to autoimmune disease.

Cyclophosphamide is associated with pulmonary function and survival benefit in patients with scleroderma and alveolitis

BACKGROUND

Lung inflammation (alveolitis) may cause lung fibrosis in scleroderma.

OBJECTIVE

To determine whether cyclophosphamide treatment is associated with retention of lung function and improved survival in scleroderma patients with alveolitis.

DESIGN

Retrospective cohort study.

SETTING

Johns Hopkins and University of Maryland Scleroderma Center.

PATIENTS

103 patients with scleroderma who had bronchoalveolar lavage or lung biopsy.

INTERVENTION

Cyclophosphamide therapy.

MEASUREMENTS

1) Serial measurement of forced vital capacity (FVC) and carbon monoxide diffusing capacity and 2) survival.

RESULTS

During a median follow-up of 13 months after bronchoalveolar lavage or biopsy, patients with alveolitis who did not receive cyclophosphamide therapy experienced a decrease in FVC (mean difference, -0.28 L [95% Cl, -0.41 to -0.16 L] and -7.1% of the predicted value [Cl, -10.9% to -4.0%]). Carbon monoxide diffusing capacity also decreased in these patients (mean difference, -3.3 x mmol min(-1) x kPa(-1) [Cl, -4.6 to -2.1 mmol x min(-1) x kPa(-1)] and -9.6% of the predicted value [Cl, -16.7% to -2.4%]). During a median follow-up of 16 months, patients with alveolitis who received cyclophosphamide were more likely to have a good outcome (stabilization or improvement) in FVC (relative risk, 2.5 [Cl, 1.5 to 4.1]) and diffusing capacity (relative risk, 1.5 [Cl, 1.0 to 2.2]). These patients also had improved survival; the median survival rate was 89% (25th, 75th percentiles, 84%, 94%) compared with 71% (25th, 75th percentiles, 55%, 86%) in untreated patients (P = 0.01, log-rank test).

CONCLUSIONS

The presence of lung inflammation identifies patients with scleroderma who are more likely to have worsening lung function. Lung function outcomes and survival are improved in patients with alveolitis who receive cyclophosphamide.

Expiratory flow limitation and intrinsic positive end-expiratory pressure at zero positive end-expiratory pressure in patients with adult respiratory distress syndrome

It has been suggested that in patients with adult respiratory distress syndrome (ARDS), intrinsic positive end-expiratory pressure (PEEPi) is generated by a disproportionate increase in expiratory flow resistance. Using the negative expiratory pressure (NEP) technique, we assessed whether expiratory flow limitation (EFL) and PEEPi were present at zero PEEP in 10 semirecumbent, mechanically ventilated ARDS patients. Because bronchodilators may decrease airway resistance, we also investigated the effect of nebulized salbutamol on EFL, PEEPi, and respiratory mechanics in these patients, and in seven patients we measured the latter variables in the supine position as well. In the semirecumbent position, eight of the 10 ARDS patients exhibited tidal EFL, ranging from 5 to 37% of the control tidal volume (VT), whereas PEEPi was present in all 10 subjects, ranging from 0.4 cm H(2)O to 7.7 cm H(2)O. The onset of EFL was heralded by a distinct inflection point on the expiratory flow-volume curve, which probably reflected small-airway closure. Administration of salbutamol had no statistically significant effect on PEEPi, EFL (as %VT), or respiratory mechanics. EFL (%VT) and PEEPi were significantly higher in the supine position than in the semirecumbent position, whereas the other respiratory variables did not change. Our results suggest that in the absence of externally applied PEEP, most ARDS patients exhibit EFL associated with small-airway closure and a concomitant PEEPi.

[Pulmonary involvement in systemic scleroderma. Part I. Chronic fibrosing interstitial lung disease]

INTRODUCTION

Chronic pulmonary interstitial fibrosis is the most frequent respiratory manifestation in systemic sclerosis, occurring in 80% of cases. It remains a severe complication of the disease and is the primary cause of mortality related to respiratory insufficiency in 20 to 60% of cases.

CURRENT KNOWLEDGE AND KEY POINTS

The date of onset of interstitial lung disease remains undetermined, and only in rare cases does it reveal the presence of systemic sclerosis. The clinical signs are only observable at a later stage, when at least 50% of the lung parenchyma is affected. The methods of choice adopted for early diagnosis of this disease are high resolution computed tomography and pulmonary functional investigations; they should be carried out during the preliminary investigation and at follow-up once a year. Moreover, high resolution computed tomography also provides prognostic data, for there is a correlation between the type of lesion and its severity as determined by high resolution computed tomography and by histological findings. The value of other methods of investigation, in particular bronchoalveolar lavage, has not yet been clearly established. The association of cyclophosphamide and corticoids is currently being evaluated (indications, administration modalities, duration), and this combination may be the most effective treatment.

FUTURE PROSPECTS AND PROJECTS

Interstitial lung disease is one of the major causes of morbidity and mortality in systemic sclerosis. Early diagnosis and management of this disease is therefore of utmost importance.

Pulmonary involvement in diffuse cutaneous systemic sclerosis: broncheoalveolar fluid granulocytosis predicts progression of fibrosing alveolitis

OBJECTIVE

The clinical course of fibrosing alveolitis (FA) in patients with systemic sclerosis (SSc) may vary considerably from stable condition for years to continuous fatal progression. This prospective study aimed at identifying the prognostic value of bronchoalveolar lavage fluid (BALF) analysis in FASSc.

METHODS

Seventy three consecutive patients with SSc and clinical signs of pulmonary involvement were enrolled. Every patient underwent clinical examination, lung function tests, computed tomography (CT), gallium scan, echocardiography, and bronchoalveolar lavage (BAL). Forty nine patients, 26 with pathological and 23 with normal BALF findings were prospectively followed up for two years and re-evaluated annually.

RESULTS

At baseline, 51 subjects (70%) showed radiological signs of lung fibrosis and/or alveolitis by CT and diffusion capacity for carbon monoxide (DLco) was decreased in 47 patients (64%). Thirty five patients (48%) had pathological BALF findings. BALF differential counts included BALF granulocytosis in 18, BALF lymphocytosis in 12, and a mixed increase of both granulocytes and lymphocytes in five patients. On follow up, a progression of FA with a significant decrease of DLco was only observed in patients with BALF granulocytosis. In contrast, patients with BALF lymphocytosis or normal BALF cell count had stable lung function parameters during the study period. In none of our patients echocardiography showed evidence of pulmonary hypertension.

CONCLUSION

BALF granulocytosis predicts progression of FA with deterioration of lung function, which is most sensitively monitored by DLco. Immunosuppressive treatment is recommended in patients with granulocytic FASSc.

Flowcytometric analysis of bronchoalveolar lavage fluid cells in polymyositis/dermatomyositis with interstitial pneumonia

OBJECTIVE

Interstitial lung disease (ILD) is a complication occurring in 10-30% of patients with polymyositis/dermatomyositis (PM/DM) as well as in those with progressive systemic sclerosis (PSS). Clinical features are different between these two disease states, notably with respect to the duration of manifestations, pathological findings, response to steroid therapy etc. However, dissimilarities in pulmonary inflammatory cell characteristics, which, if present at all, would be of critical importance, remain as yet to be clarified.

METHODOLOGY

The phenotypes of lymphocytes and alveolar macrophages in bronchoalveolar lavage fluid (BALF) were analysed to elucidate phenotypic peculiarity of pulmonary inflammatory cells of ILD in PM/DM. Eight PM/DM patients with ILD (mean age 47.9 years) were examined by bronchofibrescopy under local anaesthesia. Bronchoalveolar lavage was performed from the right middle lobe using four 50 mL aliquots of normal saline and the recovered fluid was compared with BALF of ILD in PSS.

RESULTS

Bronchoalveolar lavage fluid cells of PM/DM patients with ILD showed an increased percentage of CD8+ lymphocytes, in particular CD8+ histocompatibility leucocyte antigen-DR positive lymphocytes and CD8+ CD11b-lymphocytes, both of which represent cytotoxic T cells. However, phenotypic differences in these lymphocytes were not found between PM and DM. The percentage of alveolar macrophages with expression of histocompatibility leucocyte antigen-DQ was significantly different among the three groups (PM/DM, PSS, healthy volunteers).

CONCLUSIONS

Cytotoxic T cells may be major pulmonary inflammatory cells of ILD in PM/DM with no apparent difference between PM and DM. In contrast, ILD in PSS was suggested as being likely to be characterized by activated macrophage.

Correcting static intrinsic positive end-expiratory pressure for expiratory muscle contraction. Validation of a new method

We have recently shown (Eur. Respir. J. 1997;10:522-529) that in spontaneously breathing and actively expiring patients, static intrinsic positive end-expiratory pressure (PEEPi,st) can be corrected for expiratory muscle contraction by subtracting the average expiratory rise in gastric pressure (Pga,exp rise), calculated from three breaths just prior to an airway occlusion, from the end-expiratory airway pressure (Paw) of the first occluded inspiratory effort (PEEPi,st avg). However, since in some patients there is substantial variability in the intensity of expiratory muscle activity and hence in Pga,exp rise, this method may be inaccurate because the Pga,exp rise of breaths preceding airway occlusion may differ from that of the first postocclusion breath. In the present study, we introduced a new method consisting of synchronous subtraction of Pga,exp rise from Paw, both occurring during airway occlusion (PEEPi,st sub). PEEPi,st sub and PEEPi,st avg were each compared with the reference PEEPi,st (PEEPi,st ref), which was obtained during muscular paralysis and simulation of the spontaneous breathing pattern by the ventilator. We found that, in 25 critically ill patients, PEEPi,st sub (mean +/- SD, 5.3 +/- 2.6 cm H(2)O) was nearly identical to PEEPi,st ref (5.4 +/- 2.4 cm H(2)O). Their mean difference was -0.06 cm H(2)O with limits of agreement -0.96 to 0.84 cm H(2)O, indicating a strong agreement between these methods. In contrast, mean difference of PEEPi,st avg and PEEPi,st ref was 0.73 cm H(2)O with limits of agreement -3.97 to 5.43 cm H(2)O, indicating lack of agreement. Coefficient of variation of Pga,exp rise was 14.3 +/- 7.2% (range, 5.2 to 28.3%). There was a good correlation between the coefficient of variation of Pga,exp rise and the difference between PEEPi,st avg and PEEPi,st ref (r = 0.909; p < 0.001). We conclude that PEEPi,st can be accurately measured in spontaneously breathing patients by synchronous subtraction of Pga,exp rise from Paw during airway occlusion.

Augmented production of chemokines (monocyte chemotactic protein-1 (MCP-1), macrophage inflammatory protein-1alpha (MIP-1alpha) and MIP-1beta) in patients with systemic sclerosis: MCP-1 and MIP-1alpha may be involved in the development of pulmonary fibrosis

To determine the role of chemokines in the pathogenesis of systemic sclerosis (SSc), we examined serum levels, spontaneous production by peripheral blood mononuclear cells (PBMC), and histological distribution in the affected skin, of MCP-1, MIP-1alpha and MIP-1beta in SSc patients. Serum levels of these chemokines were examined by ELISA in 58 patients with SSc and 20 normal controls. The levels of these chemokines in culture supernatants from PBMC were also measured by ELISA. Serum levels and spontaneous production levels by PBMC of MCP-1, MIP-1alpha, and MIP-1beta were significantly elevated in patients with SSc compared with normal controls. Elevated serum levels of MCP-1 and MIP-1alpha significantly correlated with the presence of pulmonary fibrosis. MCP-1 expression in the skin of SSc was immunohistochemically examined using anti-MCP-1 MoAb. MCP-1 was strongly expressed in the epidermis, inflammatory mononuclear cells, and vascular endothelial cells in the sclerotic skin of SSc patients, but not expressed in any control skin. Furthermore, the MCP-1 expression in inflammatory mononuclear cells and endothelial cells significantly correlated with earlier onset of SSc. Thus, MCP-1, MIP-1alpha and MIP-1beta may be involved in the disease process, possibly by augmenting leucocyte migration into the affected tissues in SSc. Furthermore, MCP-1 and MIP-1alpha may play an important role in the development of pulmonary fibrosis in SSc.

Regulation of Monocyte Survival In Vitro by Deposited IgG: Role of Macrophage Colony-Stimulating Factor

IgG deposition at tissue sites characteristically leads to macrophage accumulation and organ injury. Although the mechanism by which deposited IgG induces tissue injury is not known, we have recently demonstrated that deposited IgG stimulates the release of IL-8 and monocyte chemoattractant protein-1 from normal human monocytes, which may drive inflammation. Since IgG also induces macrophage accumulation in these diseases, we hypothesized that deposited IgG protects monocytes from apoptosis. As an in vitro model of the effect of deposited IgG on monocyte survival, monocyte apoptosis was studied after FcγR cross-linking. Monocytes cultured on immobilized IgG, which induces FcγR cross-linking, were protected from apoptosis, whereas monocytes cultured with equivalent concentrations of F(ab′)2 IgG or 50 times higher concentrations of soluble IgG, neither of which induces FcγR cross-linking, were not protected. Moreover, this protection was transferable, as supernatants from immobilized IgG-stimulated monocytes protected freshly isolated monocytes from apoptosis and contained functional M-CSF, a known monocyte survival factor. M-CSF mediated the monocyte survival induced by FcγR cross-linking, as neutralizing anti-human M-CSF Abs blocked the monocyte protection provided by either immobilized IgG or IgG-stimulated monocyte supernatants. These findings demonstrate a novel mechanism by which deposited IgG targets tissue macrophage accumulation through FcγR-mediated M-CSF release. This pathway may play an important role in promoting and potentiating IgG-mediated tissue injury.

Changes in the work of breathing induced by tracheotomy in ventilator-dependent patients

Tracheotomy is widely performed on ventilator-dependent patients, but its effects on respiratory mechanics have not been studied. We measured the work of breathing (WOB) in eight patients before and after tracheotomy during breathing at three identical levels of pressure support (PS): baseline level (PS-B), PS + 5 cm H2O (PS+5), and PS - 5 cm H2O (PS-5). After the procedure, we also compared the resistive work induced by the patients' endotracheal tubes (ETTs) and by a new tracheotomy cannula in an in vitro bench study. A significant reduction in the WOB was observed after tracheotomy for PS-B (from 0.9 +/- 0.4 to 0.4 +/- 0.2 J/L, p < 0.05), and for PS-5 (1.4 +/- 0.6 to 0.6 +/- 0.3 J/L, p < 0.05), with a near-significant reduction for PS+5 (0.5 +/- 0.5 to 0.2 +/- 0.1 J/L, p = 0.05). A significant reduction was also observed in the pressure-time index of the respiratory muscles (181 +/- 92 to 80 +/- 56 cm H2O. s/min for PS-B, p < 0.05). Resistive and elastic work computed from transpulmonary pressure measurements decreased significantly at PS-B and PS-5. A significant reduction in occlusion pressure and intrinsic positive end-expiratory pressure (PEEP) was also observed for all conditions, with no significant change in breathing pattern. Three patients had ineffective breathing efforts before tracheotomy, and all had improved synchrony with the ventilator after the procedure. In vitro measurements made with ETTs removed from the patients, with new ETTs, and with the tracheotomy cannula showed that the cannula reduced the resistive work induced by the artificial airway. Part of these results was explained by a slight, subtle reduction of the inner diameter of used ETTs. We conclude that tracheotomy can substantially reduce the mechanical workload of ventilator-dependent patients.

A simple automated method for measuring pressure-volume curves during mechanical ventilation

Measurement of respiratory compliance is advocated for assessing the severity of acute respiratory failure (ARF). Recently, the administration of an automated constant flow of 15 L/min was proposed as a method easier to implement at the bedside than supersyringe or inspiratory occlusions methods. However, pressure-volume (P-V) curves were shifted to the right because of the resistive properties of the respiratory system. The aim of this study was to compare the P-V curves obtained using two constant flows-3 and 9 L/min-during volume-controlled mechanical ventilation with those obtained with the supersyringe and the inspiratory occlusions methods. Fourteen paralyzed patients with ARF were studied. The supersyringe and the inspiratory occlusions methods were performed according to usual recommendations. The new automated method was performed during volume-controlled mechanical ventilation by setting the inspiratory:expiratory ratio at 80%, the respiratory frequency at 5 breaths/min, and the tidal volume at 500 or 1,500 ml. These peculiar ventilatory settings were equivalent to administering a constant flow of 3 or 9 L/min during a 9.6-s inspiration. Esophageal and airway pressures were recorded. P-V curves obtained by the 3-L/min constant-flow method were identical to those obtained by the reference methods, whereas the P-V curve obtained by the 9-L/min constant flow was slightly shifted to the right. The slopes of the P-V curves and the lower inflection points were not different between all methods, indicating that the resistive component induced by administering a constant flow equal to or less than 9 L/min is not of clinical relevance. Because the 3-L/min constant-flow method is not artifacted by the resistive properties of the respiratory system and does not require any other equipment than a ventilator, it is an easy-to-implement, inexpensive, safe, and reliable method for measuring the thoracopulmonary P-V curve at the bedside.

Clinical examination reliably detects intrinsic positive end-expiratory pressure in critically ill, mechanically ventilated patients

Critically ill patients requiring mechanical ventilation often develop intrinsic positive end-expiratory pressure (PEEPi). Methods for its detection include an expiratory flow waveform display (not always available), an esophageal pressure transducer (invasive), or a relaxed or paralyzed patient. We sought to determine the accuracy of clinical examination for detecting PEEPi. Examiners blinded to waveform analysis assessed patients for the presence of PEEPi by inspection/palpation and auscultation. If either inspection/palpation or auscultation demonstrated PEEPi, it was said to be present by clinical exam. Clinicians with various levels of experience (attending, resident, student) made 503 observations of 71 patients. Sensitivity (SENS), specificity (SPEC), positive predictive value (PPV), negative predictive value (NPV), and likelihood ratios were determined for inspection/palpation, auscultation, and clinical exam. PEEPi was present during 69.8% of observations. SENS, SPEC, and PPV of clinical exam were 0.72, 0.91, and 0.95 respectively for the examiners as a whole. Likelihood ratio for PEEPi detection by clinical exam was 8.35. Attending intensivists displayed SPEC and PPV of 1.0. NPV was only 0.58 (likelihood ratio 0.31). We conclude that the clinical exam is very good for detecting PEEPi at all experience levels; and further, that the clinical exam is only modestly useful for ruling out PEEPi, therefore, other tests should be used if PEEPi is not detected by clinical exam.

Manifestations of scleroderma pulmonary disease

Scleroderma is a multisystem disease of unknown cause characterized by synthesis and deposition of excessive extracellular matrix and vascular anti-GBM antibodies, leading to pulmonary hemorrhage and glomerulonephritis with rapidly progressive renal insufficiency. Recent advances in the understanding of disease pathogenesis and diagnosis and treatment have significantly improved our ability to recognize the syndrome, distinguish it from other similar disorders, and offer successful treatment. This article focuses on the pathogenetic features, clinical manifestations, diagnostic strategies, and therapeutic principles of anti-GBM disease.

Interstitial lung disease in systemic sclerosis: comparison of BALF lymphocyte phenotype and DLCO impairment

Patients with scleroderma (systemic sclerosis-SSc) frequently develop an interstitial lung disease. The role of lymphocytes in fibrosing alveolitis preceding lung fibrosis has been established. The purpose of this work was to evaluate cell profiles and lymphocyte phenotypes in the bronchoalveolar lavage (BAL) fluid and to correlate them with depression in lung function tests detected by depletion of diffusing capacity (DLCO). BAL was carried out in 25 untreated, non-smoking patients suffering from diffuse scleroderma and in 12 healthy non-smoking volunteers. For the analysis of lymphocyte sub-sets flow cytometry and monoclonal antibodies were used. The following cell sub-types were counted: T lymphocytes, B lymphocytes, helper lymphocytes, suppressor/cytotoxic lymphocytes, natural killer cells, cytotoxic T lymphocytes and activated T lymphocytes. The total cell count was higher in the group of patients with mild and moderate impairment in DLCO. The percentage of lymphocytes was greater in patients with DLCO lower than 65% of the predicted value since neutrophilia was found in patients with severe DLCO depletion, i.e. significant when compared with healthy subjects. The proportions of suppressor/cytotoxic lymphocytes and of activated T lymphocytes were higher in patients than in controls. The statistical analysis revealed significant differences between patients with moderate and mild changes in DLCO and the healthy volunteers. A decreased helper/suppressor ratio was noticed in these patients. We concluded that the BALF lymphocyte phenotype analysis may reflect the features of alveolitis in patients with SSc.

The tension-time index and the frequency/tidal volume ratio are the major pathophysiologic determinants of weaning failure and success

We have previously shown (Am. J. Respir. Crit. Care Med. 1995;152:1248-1255) that in patients needing mechanical ventilation, the load imposed on the inspiratory muscles is excessive relative to their neuromuscular capacity. We have therefore hypothesized that weaning failure may occur because at the time of the trial of spontaneous breathing there is insufficient reduction of the inspiratory load. We therefore prospectively studied patients who initially had failed to wean from mechanical ventilation (F) but had successful weaning (S) on a later occasion. Compared with S, during F patients had greater intrinsic positive end-expiratory pressure (6. 10 +/- 2.45 versus 3.83 +/- 2.69 cm H2O), dynamic hyperinflation (327 +/- 180 versus 213 +/- 175 ml), total resistance (Rmax, 14.14 +/- 4.95 versus 11.19 +/- 4.01 cm H2O/L/s), ratio of mean to maximum inspiratory pressure (0.46 +/- 0.1 versus 0.31 +/- 0.08), tension time index (TTI, 0.162 +/- 0.032 versus 0.102 +/- 0.023) and power (315 +/- 153 versus 215 +/- 75 cm H2O x L/min), less maximum inspiratory pressure (42.3 +/- 12.7 versus 53.8 +/- 15.1 cm H2O), and a breathing pattern that was more rapid and shallow (ratio of frequency to tidal volume, f/VT 98 +/- 38 versus 62 +/- 21 breaths/min/L). To clarify on pathophysiologic grounds what determines inability to wean from mechanical ventilation, we performed multiple logistic regression analysis with the weaning outcome as the dependent variable. The TTI and the f/VT ratio were the only significant variables in the model. We conclude that the TTI and the f/VT are the major pathophysiologic determinants underlying the transition from weaning failure to weaning success.

Intravenous pulse cyclophosphamide in the treatment of interstitial lung disease due to collagen vascular diseases

OBJECTIVE

Substantial toxicity limits the use of daily oral cyclophosphamide (CYC) for the treatment of interstitial lung disease (ILD) due to collagen vascular diseases. We examined whether intravenous (i.v.) pulse CYC can be substituted for daily oral therapy.

METHODS

Six patients with rapidly progressive ILD due to polymyositis, systemic sclerosis, systemic lupus erythematosus, or primary Sjögren's syndrome received 6-9 cycles of i.v. pulse CYC (0.5 gm/m2 of body surface area), together with an initial course of 50 mg of prednisolone, which was tapered to a maintenance dosage of 5-7.5 mg/day, and their response was measured clinically, by high-resolution computed tomography (HRCT) and by assessment of the bronchoalveolar lavage (BAL) cell profile.

RESULTS

All patients showed significant improvement in exercise tolerance and lung function. Elevated BAL neutrophils dropped substantially, whereas the response of BAL lymphocytes was inconsistent. Low-attenuation opacities in the HRCT regressed in 4 patients and remained unchanged in 2, but reticular infiltrates remained largely unaffected. Remission was maintained with hydroxychloroquine, azathioprine, or cyclosporin A.

CONCLUSION

I.v. pulse CYC proved to be an effective and well-tolerated treatment in these patients. Since it appears to target mainly the inflammatory component of the disease, it should be reserved for progressive ILD featuring indices of high inflammatory activity.

Bronchoalveolar lavage cellularity: lone cryptogenic fibrosing alveolitis compared with the fibrosing alveolitis of systemic sclerosis

Lone cryptogenic fibrosing alveolitis (CFA) is histologically identical to fibrosing alveolitis associated with systemic sclerosis (FASSc), but it has a much worse prognosis after matching for disease severity at presentation. The aims of this study were to gain insights into possible pathogenetic mechanisms contributing to this prognostic difference, by comparing bronchoalveolar lavage (BAL) cellularity in the two diseases, and to evaluate the relationships between BAL findings and the regional and global extent of disease, quantified by thin-section computed tomography (CT) and lung function indices. Patients with CFA were distinguished by more extensive fibrosing alveolitis on CT (p < 0.02) and by higher counts of neutrophils (total per ml, p < 0.02; percentage p < 0.03) and eosinophils (total per ml, p < 0.002; percentages, p < 0.02) in BAL fluid. After adjustment for functional and morphologic measures of disease extent, eosinophil percentages and total counts were increased in CFA (p < 0.05 in all 12 multivariate models), but they were not independently related to regional or global disease severity. Neutrophil percentages and total counts were virtually identical in CFA and FASSc in disease of comparable severity, and they increased with increasingly extensive lobar disease and global disease, as judged by CT, p < 0.0005 in all analyses. Neutrophil levels were more closely linked to the extent of disease on CT than to the severity of functional impairment, on univariate and multivariate analysis. The higher BAL eosinophil levels seen in CFA, compared with those seen in FASSc, after adjustment for disease extent, indicate that an eosinophilic influx may be linked to the pathogenesis of fibrosing alveolitis. By contrast, BAL neutrophil levels increase with increasingly extensive disease on CT, but they do not differ independently between CFA and FASSc, suggesting that neutrophil degradation products are unlikely to account for the excess mortality in CFA, compared with that in FASSc.

Interrupted expiratory flow on automatically constructed flow-volume curves may determine the presence of intrinsic positive end-expiratory pressure during one-lung ventilation

We studied patients undergoing elective pulmonary surgery to establish whether observing interrupted expiratory flow (IEF) on the flow-volume curves constructed by the Ultima SV respiratory monitor is a reliable way to identify patients with dynamic pulmonary hyperinflation and intrinsic positive end-expiratory pressure (PEEPi). Patients' tracheas were intubated with a double-lumen endotracheal tube and ventilated with a Siemens 900C constant flow ventilator. In 30 patients, PEEPi was determined by the end-expiratory occlusion (EEO) method during the periods of two-lung and one-lung ventilation in the lateral position. Sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy of the IEF method were calculated. From the 122 measurement pairs, PEEPi was identified with the EEO method in 65 occasions. The mean level of PEEPi was 4.4 cm H2O. During one-lung ventilation, the level of PEEPi and the number of true-positive findings was significantly higher (PEEPi = 4.7 cm H2O and 32 episodes) than during two-lung ventilation (2.9 cm H2O and 19 episodes). When the level of PEEPi was higher than 5 cm H2O, the predictive value of IEF was 100%. The overall sensitivity of the IEF method was 0.78, its specificity was 0.91, and its predictive value was 0.92. In conclusion, examination of the flow-volume curves displayed on the respiratory monitor may identify patients with dynamic hyperinflation and PEEPi during anesthesia for thoracic surgery.

IMPLICATIONS

To identify patients with intrinsic positive end-expiratory pressure during anesthesia without the need to interrupt mechanical ventilation, the flow-volume curves of an online respiratory monitor may be examined. The presence of an interrupted expiratory flow may suggest the presence of intrinsic positive end-expiratory pressure with a reasonable accuracy.

Electrical impedance tomography can monitor dynamic hyperinflation in dogs

We assessed in eight dogs the accuracy with which electrical impedance tomography (EIT) can monitor changes in lung volume by comparing the changes in mean lung conductivity obtained with EIT to changes in esophageal pressure (Pes) and to airway opening pressure (Pao) measured after airway occlusion. The average volume measurement errors were determined: 26 ml for EIT; 35 ml for Pao; and 54 ml for Pes. Subsequently, lung inflation due to applied positive end-expiratory pressure was measured by EIT (delta VEIT) and Pao (delta VPAO) under both inflation and deflation conditions. Whereas delta VPAO was equal under both conditions, delta VEIT was 28 ml greater during deflation than inflation, indicating that EIT is sensitive to lung volume history. The average inflation delta VEIT was 67.7 +/- 78 ml greater than delta VPAO, for an average volume increase of 418 ml. Lung inflation due to external expiratory resistance was measured during ventilation by EIT (delta VEIT,vent) and Pes (delta VPes,vent) and at occlusion by EIT (delta VEIT,occl), Pes, and Pao. The average differences between EIT estimates and delta VEIT,occl were 5.8 +/- 44 ml for delta VEIT,vent and 49.5 +/- 34 ml for delta VEIT,occl. The average volume increase for all dogs was 442.2 ml. These results show that EIT can provide usefully accurate estimates of changes in lung volume over an extended time period and that the technique has promise as a means of conveniently and noninvasively monitoring lung hyperinflation.

Elevated serum levels of mucin-associated antigen in patients with acute respiratory distress syndrome

Increased serum levels of mucin-associated antigen have been previously demonstrated in patients with cystic fibrosis (CF) and interstitial pneumonia, and in lung-transplant recipients. The present study assessed the serum airway mucin levels in patients with acute respiratory distress syndrome (ARDS). An enzyme-linked immunosorbent assay (ELISA) method with a human-airway-mucin-specific monoclonal antibody (17Q2) was used to measure serum mucin levels in normal subjects, chronic smokers, patients with chronic bronchitis and other pulmonary diseases, patients with acute cardiogenic lung edema, and patients with ARDS. The serum mucin levels measured 9.9 +/- 0.8 ng/ml (mean +/- SEM, n = 59) in normal subjects, 12.7 +/- 1.6 ng/ml (n = 29) in chronic smokers, 21.8 +/- 1.9 ng/ml (n = 28) in patients with chronic bronchitis and other pulmonary diseases, 9.0 +/- 3.1 ng/ml (n = 5) in patients with acute cardiogenic lung edema. The serum mucin level was 53.8 +/- 6.6 ng/ml (n = 13) in patients with ARDS (p < 0.05, as compared with the four other groups). Serial measurements of serum mucin levels were obtained in patients with ARDS. Statistical analysis showed an inverse correlation of serial measurements of serum mucin with static respiratory-system compliance (p = 0.021), an inverse correlation of sequential serum mucin levels and log(Pa(O2)/Fl(O2)) (p = 0.016), and a positive correlation of sequential serum mucin levels and lung injury score (LIS) (p = 0.019). Gel-filtration analysis showed that mucin-associated antigens in ARDS sera were polydispersed and smaller than the antigens in normal sera. This study indicates that an increasing amount of degraded mucin occurs in patients with ARDS.

Endothelin-1 secretion by alveolar macrophages in systemic sclerosis

Endothelin-1 (ET-1), a potent fibroblast/smooth muscle cells mitogen, has been implicated in the pathogenesis of systemic sclerosis lung disease (SSc). Since monocytes and macrophages are thought to be activated in SSc, we hypothesized that alveolar macrophages (AM) and their precursors blood monocytes from patients with SSc produced more ET-1 than cells from healthy subjects. ET-1 and big ET-1 concentrations were measured in plasma, in bronchoalveolar lavage (BAL) fluids and in cell culture supernatants from monocytes and alveolar macrophages derived from 13 patients with definite SSc with lung involvement and from 10 control subjects. Plasma and BAL fluid ET-1 and big ET-1 levels were similar in both controls and patients with SSc. ET-1 and big ET-1 concentrations in unstimulated alveolar macrophage supernatants were similar in both groups. In contrast, LPS-stimulated alveolar macrophages from patients with SSc secreted higher amounts of ET-1 and big ET-1 than control subjects. ET-1 and big ET-1 concentrations in monocyte supernatants (either LPS-stimulated or not) were not different in patients and controls. These results show that AM from patients with SSc are hyperresponsive to LPS in vitro in terms of ET-1 and big ET-1 production and suggest that AM could participate in vivo in the overproduction of this potentially profibrotic mediator in patients with SSc.

Differential inspiratory muscle pressure contributions to breathing during dynamic hyperinflation

During dynamic hyperinflation, the ventilatory pump is facing increased demand because it must overcome the intrinsic positive end-expiratory pressure (PEEPi) and decreased capacity since it must operate at a dynamically increased end-expiratory lung volume (EELV). The aim of this study was to evaluate the relative pressure contribution by the diaphragm and inspiratory rib cage muscles (RCMs) during dynamic hyperinflation. In six healthy subjects, dynamic hyperinflation was induced by limiting expiratory flow. The global inspiratory muscle pressure (delta Pmus,i) and transdiaphragmatic pressure (delta Pdi) were partitioned into the portion used to overcome PEEPi and the portion used to inflate the respiratory system. The delta Pdi/delta Pmus,i ratio was used to estimate the pressure contribution of RCMs relative to that of the diaphragm. Our results suggest that (1) with increasing severity of dynamic hyperinflation, there is a significant increase in the inspiratory pressure contribution of RCMs relative to that of the diaphragm for inflating the respiratory system; (2) during dynamic hyperinflation, especially at high EELV, the major pressure contribution of the diaphragm is to overcome the PEEPi-imposed inspiratory threshold load, whereas the inspiratory pressure needed for the subsequent task of inflating the respiratory system is largely contributed by RCMs. This arrangement is consistent with the change in mechanical advantages of RCMs and the diaphragm during the development of dynamic hyperinflation.

A model of the spontaneously breathing patient: applications to intrinsic PEEP and work of breathing

Intrinsic positive end-expiratory pressure (PEEPi) and inspiratory work of breathing (WI) are important factors in the management of severe obstructive respiratory disease. We used a computer model of spontaneously breathing patients with chronic obstructive pulmonary disease to assess the sensitivity of measurement techniques for dynamic PEEPi (PEEPidyn) and WI to expiratory muscle activity (EMA) and cardiogenic oscillations (CGO) on esophageal pressure. Without EMA and CGO, both PEEPidyn and WI were accurately estimated (r = 0.999 and 0.95, respectively). Addition of moderate EMA caused PEEPidyn and WI to be systematically overestimated by 141 and 52%, respectively. Furthermore, CGO introduced large random errors, obliterating the correlation between the true and estimated values for both PEEPidyn (r = 0.29) and WI (r = 0.38). Thus the accurate estimation of PEEPidyn and WI requires steps to be taken to ameliorate the adverse effects of both EMA and CGO. Taking advantage of our simulations, we also investigated the relationship between PEEPidyn and static PEEPi (PEEPistat). The PEEPidyn/PEEPistat ratio decreased as stress adaptation in the lung was increased, suggesting that heterogeneity of expiratory flow limitation is responsible for the discrepancies between PEEPidyn and PEEPistat that have been reported in patients with severe airway obstruction.

Assessment of pulmonary function in the early phase of ARDS in pediatric patients

Scant data are available on lung function in acute respiratory distress syndrome (ARDS) in pediatric patients. We measured respiratory mechanics by single-breath occlusion and maximum expiratory flow-volume curves by forced deflation in ten critically ill infants with clinical ARDS. Ten mechanically ventilated infants without lung disease served as the control group. To assess the severity of the lung injury in the infants with ARDS, we modified an adult scoring system that calculates a score (from 0 to 4; > 2.5 indicates severe lung injury) based on the extent of chest radiographic changes, degree of hypoxemia, amount of positive end-expiratory pressure (PEEP), and total respiratory system compliance. The lung injury scores of our patients were in the range of 2.75 to 3.75. The lung injury scores of the control group were zero. The predominant alteration in lung function was restrictive, as characterized by a significant decrease in total respiratory system compliance (0.41 +/- 0.13 ml/cmH2O/kg versus 1.12 +/- 0.16 ml/cmH2O/kg of controls; P < 0.001) and forced vital capacity (21.5 +/- 6.5 ml/kg versus 59.2 +/- 6.3 ml/kg of controls; P < 0.001). Maximum expiratory flow rates at 10% forced vital capacity were significantly increased (23.6 +/- 20.1 ml/kg/sec versus 8.4 +/- 2.5 ml/kg/sec of controls; P < 0.05), confirming the absence of any significant obstructive abnormalities. The passive expiratory flow-volume curves were curvilinear and convex in shape, indicating inhomogeneous lung pathology. The inhomogeneous distribution of lung injury in ARDS restricts the validity of respiratory mechanics measurements that rely on a single-compartment model. However, the forced deflation technique allows accurate spirometric assessments of the severity of restrictive (and obstructive) lung function changes in intubated infants with severe ARDS. Such measurements can be incorporated into lung injury scoring systems to classify the severity of the disease process for the purpose of outcome evaluation and to evaluate the effect of therapeutic interventions.

Unloadiing of the work of breathing by proportional assist ventilation in a lung model

OBJECTIVES

Proportional assist ventilation is devised to increase airway pressure in proportion to inspiratory effort. A systematic study of the performance of this new mode of ventilation has not been presented. We tested in the laboratory the capability of proportional assist ventilation to unload the work of breathing in proportion to ventilatory drive, under a variety of mechanical loads.

DESIGN

During variations of "ventilatory drive" (i.e., tidal volume), unloading of the work of breathing by proportional assist ventilation was contrasted with unloading by pressure-support ventilation.

SETTING

The respiratory laboratory of a university-affiliated teaching hospital.

SUBJECT

A bellows-in-a-box lung model, powered by a sine wave air flow generator.

INTERVENTIONS

Proportional assist and pressure-support ventilation were preset to provide comparable support at a baseline "ventilatory drive" of 0.7-L tidal volume. The set levels of proportional assist and pressure-support ventilation were subsequently applied to five tidal volumes, from 0.2 to 1.2 L. Three levels of inspiratory support and three settings of mechanical load were evaluated.

MEASUREMENTS AND MAIN RESULTS

Proportional assist ventilation significantly (p < .05) reduced the work of breathing of the lung model at all but the lowest tidal volume (0.2 L). The preset proportion of ventilatory support (30%, 50%, and 70%) unloaded the work of breathing uniformly as ventilatory drive was varied at tidal volumes of > or = 0.5 L, but not always at tidal volumes of < or = 0.4 L. In contrast, pressure-support ventilation overassisted low tidal volumes and underassisted high tidal volumes (p < .05).

CONCLUSIONS

In a lung model, a prototype system delivering proportional assist ventilation provided uniform unloading of the work of breathing as the ventilatory drive was varied within a tidal volume range of 0.5 to 1.2 L. These findings confirm the theoretical modeling of proportional assist ventilation. This system, however, failed to properly unload low tidal volumes of 0.2 to 0.4 L.

Cardiorespiratory responses to incremental exercise in patients with systemic sclerosis

Patients with systemic sclerosis are known to have histologic pulmonary abnormalities despite normal chest radiograph or conventional pulmonary function or both. In an attempt to detect early features of lung involvement in progressive systemic sclerosis, we investigated patients with systemic sclerosis using cardiopulmonary exercise testing. We have studied 78 patients who fulfilled the American Rheumatism Association criteria for the classification of systemic sclerosis, and according to the classification of LeRoy, 44 had limited cutaneous systemic sclerosis and 34 had diffuse cutaneous systemic sclerosis. A significantly decreased diffusing capacity (65 +/- 3% of that predicted) was present only in the group with diffuse cutaneous systemic sclerosis. The patients with lung involvement showed a significant reduction in exercise capacity (54 +/- 3% of that predicted) and in oxygen uptake (70 +/- 3% of that predicted). Additionally, we could demonstrate an increased functional dead space ventilation (0.34 +/- 0.02) and widened alveolar-arterial oxygen difference during exercise (44 +/- 3 mm Hg). By cardiopulmonary exercise testing, 12 of the 78 patients (15%) with normal single-breath diffusing capacity for carbon monoxide had increased dead space to tidal volume ratio. Our results suggest that occult pulmonary impairment may be present in patients with normal pulmonary function and that cardiopulmonary exercise testing enables detection of such impairment. Our study results show the limitations of resting data in predicting abnormalities during exercise in patients with systemic sclerosis.

New aspects of pulmonary mechanics: "slowly" distensible compartments of the respiratory system, identified by a PEEP step maneuver

OBJECTIVE

The aims of the present study were 1) to evaluate a method for identification of "slowly" distensible compartments of the respiratory system (rs), which are characterized by long mechanical time constants (RC) and 2) to identify "slowly" distensible rs-compartments in mechanically ventilated patients.

DESIGN

Prospective study on a physical lung model.

SETTING

Intensive Care Unit, University Hospital, Tübingen.

PATIENTS AND PARTICIPANTS

19 patients with severe lung injury (acute respiratory distress syndrome, ARDS) and on 10 patients with mild lung injury.

MEASUREMENTS AND RESULTS

Positive end-expiratory pressure (PEEP)-increasing and -decreasing steps of about 5 cmH2O were applied and the breath-by-breath differences of inspiratory and expiratory volumes (delta V) were measured. The sequence of delta Vs were analyzed in terms of volume change in the "fast" compartment (Vfast), the "slow" compartment (Vslow), total change in lung volume (delta VL) and mechanical time constant of the slow compartment (RCslow). Thirty-eight measurements in a lung model revealed a good correlation between the preset Vslow/delta VL and Vslow/delta VL measured: r2 = 0.91. The Vslow/delta VL measured amounted to 0.94 +/- 0.15 of Vslow/delta VL in the lung model. RCslow measured was 0.92 +/- 0.43 of the RCslow reference. Starting from a PEEP level of 11 cmH2O PEEP-increasing and PEEP-decreasing steps were applied to the mechanically ventilated patients. Three out of ten patients with mild lung injury (30%) and 7/19 patients with ARDS (36.8%) revealed "slowly" distensible rs-compartments in a PEEP-increasing step, whereas 15/19 ARDS patients and 1/10 patients with mild lung injury showed "slowly" distensible rs-compartments in a PEEP-decreasing step (78.9% vs 10%, P < 0.002, chi-square test).

CONCLUSIONS

The gas distribution properties of the respiratory system can be easily studied by a PEEP-step maneuver. The relative contribution of the "slow" units to the total increase of lung volume following a PEEP step could be adequately assessed. "Slowly" distensible rs-compartments could be detected in patients with severe and mild lung injury, however significantly more ARDS patients revealed "slow" rs-compartments in PEEP-decreasing steps. The influence of "slowly" distensible rs-compartments on pulmonary gas exchange is unknown and has yet to be studied.

Scleroderma. Clinical problems. The lungs

A recent follow-up study found that patients with pulmonary involvement (with no renal or cardiac involvement) survived a median of 78 +/- 17 months. Another study found death from SSc was most frequently due to pulmonary hypertension. Improved diagnostic modalities and better understanding of the pathophysiology of SSc lung disease are essential, because mortality from this SSc lung disease remains high. During the past decade, advances have been made in the understanding of the alveolitis of SSc lung disease. Although the inciting injury remains uncertain, a cascade of inflammatory and fibrosing mediators culminates in a chronic state of interstitial lung disease. There is increasing evidence that the fibrogenic cytokines PDGF and TGF-beta are major contributors to the pathophysiology of interstitial lung disease, including that of SSc. Future research aimed at modifying the biologic response to such cytokines may yield novel therapeutic approaches to the management of this type of lung disease. Similarly, improved understanding of mediators of vascular tone, such as endothelin and nitric oxide, may yield much-needed treatments for pulmonary hypertension.

Immunopathogenesis of systemic sclerosis

The information outlined above can be used to generate a model of the immunopathogenesis of SSc (Fig. 3). This model includes a susceptible host, with age greater than 25 and female gender being risk factors. The model also includes exposure to exogenous agents, which could be different in different individuals and may include inhaled or ingested chemicals or infectious agents. An early event is T-cell activation, with infiltration in the skin and internal organs. Activation of the T cells is a selective process that appears to be influenced by antigen in SSc patients. The importance of a particular T-cell subpopulation may depend upon the organ involved and the stage of the disease. CD4+ T cells predominate in the skin. In contrast, CD8+ T cells are increased in the lungs of patients with alveolitis, where they are oligoclonal, showing evidence of antigen-driven selection. V delta 1+ gamma/delta T cells are increased in both the blood and lungs of SSc patients and also show evidence of selection by antigen. B cells are activated early, with polyclonal activation leading to hypergammaglobulinemia. SSc-specific autoantibodies target DNA topoisomerase I, centromeric proteins, and RNA polymerases I and III. Characteristics of autoantibodies in SSc suggest that the target antigens are presented to the immune system as native molecules or even part of a multiunit complex. There is some homology between viruses and autoantibody targets in SSc, which suggests that molecular mimicry may play a role in initiating the antibody response. Many nonspecific inflammatory cells infiltrate the tissues and show evidence of activation. These include macrophages and monocytes, mast cells, eosinophils, basophils, and natural killer cells. Soluble mediators made by these T cells, B cells, and nonspecific inflammatory cells can activate and damage fibroblasts, endothelial cells, and other vascular cells. The relative importance of the various candidate cytokines, the temporal sequence of their production, and their cellular sources remain largely to be defined. There may be some contribution of direct T-cell cytotoxicity or antibody-dependent cellular cytoxicity to the tissue damage that occurs.