Regional distribution of gas and tissue in acute respiratory distress syndrome. III. Consequences for the effects of positive end-expiratory pressure

Objective: To determine whether differences in lung morphology assessed by computed tomography (CT) affect the response to positive end-expiratory pressure (PEEP).¶Design: Prospective study over a 53-month period.¶Setting: Fourteen-bed surgical intensive care unit of a university hospital.¶Patients and participants: Seventy-one consecutive patients with early adult respiratory distress syndrome (ARDS).¶Measurements and results: Fast spiral thoracic CT was performed at zero end-expiratory pressure (ZEEP) and after implementation of PEEP 10 cmH₂O. Hemodynamic and respiratory parameters were measured in both conditions. PEEP-induced overdistension and alveolar recruitment were quantified by specifically designed software (Lungview). Overdistension occurred only in the upper lobes and was significantly correlated with the volume of lung, characterized by a CT attenuation ranging between –900 and –800 HU in ZEEP conditions. Cardiorespiratory effects of PEEP were similar in patients with primary and secondary ARDS. PEEP-induced alveolar recruitment of the lower lobes was significantly correlated with their lung volume (gas + tissue) at functional residual capacity. PEEP-induced alveolar recruitment was greater in the lower lobes with “inflammatory atelectasis” than in the lower lobes with “mechanical atelectasis.” Lung morphology as assessed by CT markedly influenced the effects of PEEP: in patients with diffuse CT attenuations PEEP induced a marked alveolar recruitment without overdistension, whereas in patients with lobar CT attenuations PEEP induced a mild alveolar recruitment associated with overdistension of previously aerated lung areas. These results can be explained by the uneven distribution of regional compliance characterizing patients with lobar CT attenuations (compliant upper lobes and stiff lower lobes) contrasting with a more even distribution of regional compliances observed in patients with diffuse CT attenuations.¶Conclusions: In patients with ARDS, the cardiorespiratory effects of PEEP are affected by lung morphology rather than by the cause of the lung injury (primary versus secondary ARDS). The regional distribution of the loss of aeration and the type of atelectasis –“mechanical” with a massive loss of lung volume, or “inflammatory” with a preservation of lung volume – characterizing the lower lobes are the main determinants of the cardiorespiratory effects of PEEP.     

Distribution of Pneumocystis jirovecii in lungs from colonized COPD patients

Pneumocystis jirovecii has been detected in lung tissue from patients with chronic obstructive pulmonary disease (COPD) and is associated with disease severity. The regional distribution of the organism in lungs is unknown, but differences in distribution of Pneumocystis could affect estimates of colonization prevalence. We examined the distribution of Pneumocystis in the lungs of 19 non-HIV-infected patients with COPD who were undergoing lung transplantation. DNA was extracted from explanted lungs. We found Pneumocystis colonization in lung tissue of 42.1% of patients with advanced COPD; however, there was significant regional variation in colonization between lung segments of individual patients. Colonization was detected more commonly in the lower and middle lobes than in the upper lobes. These findings suggest that single samples from an individual may underestimate the prevalence of Pneumocystis colonization and future studies may obtain a higher yield of Pneumocystis colonization detection when sampling the lower lobes.     

Regional distribution of gas and tissue in acute respiratory distress syndrome. II. Physiological correlations and definition of an ARDS Severity Score

Objectives: (a) To assess whether differences in lung morphology observed in patients with adult respiratory distress syndrome (ARDS) are associated with differences in cardiorespiratory parameters, lung mechanics, and outcome. (b) To propose a new ARDS Severity Score to identify patients with a high mortality risk. Design: Prospective study over a 53-month period. Setting: Fourteen-bed surgical intensive care unit of a university hospital. Patients and participants: Seventy-one consecutive patients with early ARDS. Measurements and results: Cardiorespiratory parameters were measured using a Swan-Ganz catheter, the pressure-volume (PV) curve was measured using the gross syringe method, and fast spiral computed tomography (CT) was performed. Patients with diffuse attenuations (n = 16) differed from patients with lobar attenuations (n = 26) regarding: (a) mortality rate (75 % vs. 42 %, p = 0.05), (b) incidence of primary ARDS (82 % vs. 50 %, p = 0.03), (c) respiratory compliance (47 ± 12 vs. 64 ± 16 ml per cmH₂O^–1 p = 0.04), and (d) lower inflexion point (8.4 ± 2.0 vs. 4.6 ± 2.0 cmH₂O, p = 0.001). A third group of patients with patchy attenuations (n = 29) had a mortality rate of 41 %, a respiratory compliance of 56 ± 18 ml per cmH₂O^–1 and a lower inflexion point of 6.3 ± 2.7 cmH₂O. The bedside chest radiograph accurately assessed lung morphology in only 42 % of the patients. In contrast to the scores based on the bedside chest radiograph, a new ARDS Severity Score based on CT lung morphology and cardiorespiratory parameters identified a subgroup of patients with a high mortality rate (≥ 60 %). Conclusions: In patients with ARDS, differences in lung morphology are associated with differences in outcome and lung mechanics. A new ARDS Severity Score based on CT lung morphology and cardiorespiratory parameters accurately identified patients with the most severe forms of ARDS and a mortality rate above 60 %. Received: 12 May 1999 Final revision received: 9 February 2000 Accepted: 10 April 2000     

Indicator Dilution Measurements of Lung Volumes and Alveolar Air Exchange During Breathing

A new triple tracer indicator dilution technique has been used to measure alveolar ventilation as well as air and tissue volumes in the lungs of experimental animals and man. The tracers indocyanine green, [(121)I]antipyrine and xenon-133 were rapidly injected into the right atrium, while sampling was carried out from a peripheral artery.Blood flow and tissue volumes were obtained by classical analysis of the indocyanine green and antipyrine concentration-time curves. A double exit-port, constant air flow model was used to analyze the xenon curves, because ventilatory loss led to incomplete recovery of the gas tracer in effluent blood. Uniform ventilation and perfusion were assumed. This analysis permitted calculation of alveolar ventilation (VA(Xe)) and functional residual capacity (FRC(Xe)) during normal breathing.In control studies, VA(Xe) was similar to VA(co2), obtained with the steady-state CO(2) method (r = 0.87), while in critically ill patients the xenon measurement was significantly lower, averaging 54% of VA(co2). In theory, underestimates in VA(Xe) and decrease in the ratio VA(Xe)/VA(co2) relate to nonuniformity in regional ventilation and perfusion. The effect is greatest for the slightly soluble gas, xenon. The significant inverse correlation between VA(Xe)/VA(co2) and the physiologic shunt is consistent with this postulate.FRC(Xe) was similar to the predicted FRC in animals but was 76% of the helium measured FRC in patients. FRC(Xe) was significantly lower than the xenon measured air volumes during breath-holding when nonuniformity of ventilation was not operative. Lung tissue volumes in animals were 83% of gravimetric lung weights, while in patients the volumes were much lower than predicted. Nonhomogeneous lung function, including failure to perfuse the entire capillary bed, with resultant incomplete penetration of tracers into all segments of lung air and tissue, may explain these findings. The resultant errors can be significant in sick patients, and may themselves be used to study nonhomogeneities in the distribution of ventilation and volume.     

Plasma levels of the three endothelial-specific proteins von Willebrand factor, tissue factor pathway inhibitor, and thrombomodulin do not predict the development of acute respiratory distress syndrome

Objective: To determine if the plasma levels of three endothelial-specific proteins, von Willebrand factor (vWF), tissue factor pathway inhibitor (TFPI) and thrombomodulin (TM) may be useful in predicting the development of acute respiratory distress syndrome (ARDS).¶Design: Blood samples were obtained from normal healthy volunteers and on the first day from patients at risk for ARDS and those with ARDS. Daily sequential measurements of vWF and TFPI were performed in two patients.¶Setting: Normal subjects were employees at Saint Louis University Hospital, St. Louis, Missouri. Patients at risk and those with ARDS were patients admitted to the medical and surgical floors and the intensive care units at St. Louis University Hospital.¶Patients and participants: Plasma levels of vWF, TFPI and TM were measured in 27 normals, and on day 1 in 15 patients at risk for ARDS and 18 patients with ARDS from different etiologic factors.¶Measurements and results: Plasma levels of vWF were significantly elevated in the at-risk (p < 0.01) and ARDS group (p < 0.001) as compared to normals but did not differ significantly between the two groups (p > 0.05). Plasma levels of TFPI were not significantly different between the normal and the at-risk group (p > 0.05); however, they were significantly elevated in ARDS as compared with at-risk and normal groups (p < 0.001). Levels of TM were significantly increased in the at-risk group as compared to normals (p < 0.01) but were not significantly different from the ARDS group (p > 0.05). Eight patients at risk progressed to develop ARDS. A vWF level of > 300 % in patients at risk was 62 % sensitive and 71 % specific for predicting the development of ARDS with a positive predictive value of only 34 %. TFPI levels were normal in 7 of the 8 patients who developed ARDS. A TM level of > 100 ng/ml in patients at risk was 50 % sensitive and 57 % specific with a positive predictive value of merely 8 % for development of ARDS. There was no significant difference in the mean plasma levels of the three proteins on day 1 in patients at risk who developed ARDS as compared with those who did not develop ARDS. There was also no difference in mean plasma levels of the three proteins in patients with ARDS from sepsis as compared with ARDS from other etiologies. Plasma levels of vWF and TFPI correlated significantly.¶Conclusion: Plasma levels of vWF, TFPI and TM did not appear to serve as useful markers for predicting ARDS in patients at risk.     

End-expiratory lung volume during mechanical ventilation: a comparison with reference values and the effect of positive end-expiratory pressure in intensive care unit patients with different lung conditions

Introduction

Functional residual capacity (FRC) reference values are obtained from spontaneous breathing patients, and are measured in the sitting or standing position. During mechanical ventilation FRC is determined by the level of positive end-expiratory pressure (PEEP), and it is therefore better to speak of end-expiratory lung volume. Application of higher levels of PEEP leads to increased end-expiratory lung volume as a result of recruitment or further distention of already ventilated alveoli. The aim of this study was to measure end-expiratory lung volume in mechanically ventilated intensive care unit (ICU) patients with different types of lung pathology at different PEEP levels, and to compare them with predicted sitting FRC values, arterial oxygenation, and compliance values.

Methods

End-expiratory lung volume measurements were performed at PEEP levels reduced sequentially (15, 10 and then 5 cmH₂O) in 45 mechanically ventilated patients divided into three groups according to pulmonary condition: normal lungs (group N), primary lung disorder (group P), and secondary lung disorder (group S).

Results

In all three groups, end-expiratory lung volume decreased significantly (P < 0.001) while PEEP decreased from 15 to 5 cmH₂O, whereas the ratio of arterial oxygen tension to inspired oxygen fraction did not change. At 5 cmH₂O PEEP, end-expiratory lung volume was 31, 20, and 17 ml/kg predicted body weight in groups N, P, and S, respectively. These measured values were only 66%, 42%, and 34% of the predicted sitting FRC. A correlation between change in end-expiratory lung volume and change in dynamic compliance was found in group S (P < 0.001; R ² = 0.52), but not in the other groups.

Conclusions

End-expiratory lung volume measured at 5 cmH₂O PEEP was markedly lower than predicted sitting FRC values in all groups. Only in patients with secondary lung disorders were PEEP-induced changes in end-expiratory lung volume the result of derecruitment. In combination with compliance, end-expiratory lung volume can provide additional information to optimize the ventilator settings.     

PEEP-induced changes in lung volume in acute respiratory distress syndrome. Two methods to estimate alveolar recruitment

Purpose

Lung volumes, especially functional residual capacity (FRC), are decreased in acute respiratory distress syndrome (ARDS). Positive end-expiratory pressure (PEEP) contributes to increased end-expiratory lung volume (EELV) and to improved oxygenation, but differentiating recruitment of previously nonaerated lung units from distension of previously open lung units remains difficult. This study evaluated simple methods derived from bedside EELV measurements to assess PEEP-induced lung recruitment while monitoring strain.

Methods

Prospective multicenter study in 30 mechanically ventilated patients with ARDS in five university hospital ICUs. Two PEEP levels were studied, each for 45?min, and EELV (nitrogen washout/washin technique) was measured at both levels, with the difference (??) reflecting PEEP-induced lung volume changes. Alveolar recruitment was measured using pressure-volume (PV) curves. High and low recruiters were separated based on median recruitment at high PEEP. Minimum predicted increase in lung volume computed as the product of ??PEEP by static compliance was subtracted from ??EELV as an independent estimate of recruitment. Estimated and measured recruitments were compared. Strain induced by PEEP was also calculated from the same measurements.

Results

FRC was 31?±?11% of predicted. Median [25th?C75th percentiles] PEEP-induced recruitment was 272 [187?C355] mL. Estimated recruitment correlated with recruited volume measured on PV curves (???=?0.68), with a slope close to identity. The ??EELV/FRC ratio differentiated high from low recruiters (110 [76?C135] vs. 55 [23?C70]%, p?=?0.001). Strain increase due to PEEP was larger in high recruiters (p?=?0.002).

Conclusion

PEEP-induced recruitment and strain can be assessed at the bedside using EELV measurement. We describe two bedside methods for predicting low or high alveolar recruitment during ARDS.     

Lung heme oxygenase-1 is elevated in acute respiratory distress syndrome

OBJECTIVE: We aimed to quantify concentrations of inducible heme oxygenase (HO)-1 in the lungs of patients with acute respiratory distress syndrome (ARDS) and to investigate its role as a source of ferrous iron and as a signaling agent for iron regulation. Control of such processes by heme oxygenase has implications for the onset, progression, and resolution of ARDS. DESIGN: Retrospective analysis of archived samples. SETTING: Adult intensive care unit of a postgraduate teaching hospital. PATIENTS: Patients admitted to the adult intensive care unit who fulfilled the American-European Consensus Conference criteria for ARDS. INTERVENTIONS: Biochemical and immunohistochemical studies using bronchoalveolar lavage fluid or lung tissue were performed in patients with established ARDS and in those undergoing lung resection (controls). MEASUREMENTS AND MAIN RESULTS: Concentrations of heme oxygenase protein were significantly elevated in lung tissue (193.7 +/- 13.27 vs. 81.0 +/- 16.0%, p < .01) and in bronchoalveolar lavage fluid (2.4 x 10(5) vs. 1.4 x 10(5) densitometric units, p = .047) taken from patients with ARDS compared with controls. Concentrations of heme oxygenase protein in bronchoalveolar lavage fluid from patients with ARDS correlated positively and significantly with changes in the concentrations of ferritin (r = .697, p = .02) and the iron saturation of transferrin (r = .8, p = .014) but correlated negatively and significantly with concentrations of bleomycin-detectable (redox-active) iron (r = -.73, p = .031). Significantly elevated (p < .05) concentrations of heme oxygenase staining in cell types expressing this protein were detected in patients with ARDS, compared with concentrations in the same cells taken from controls undergoing lung resection. CONCLUSIONS: Heme oxygenase protein is elevated in the lungs of patients with ARDS and may contribute to the changes in iron mobilization, signaling, and regulation seen in this condition.     

功能残气量在重症患者中的应用进展

功能残气量（FRC）是平静呼气末肺内残留的气体量,具有重要的生理功能。在需要机械通气的重症患者中呼气结束时的肺容积被称为呼气末肺容积。目前临床上有多种检测和监测FRC的方法,包括CT测量法、氦气稀释法、氮气冲洗法、电阻抗断层成像技术等方法,其中氮气冲洗法中的氮气洗入/洗出技术更适合在重症患者中开展。FRC可以作为评估机械通气患者肺部疾病病情并指导个性化的保护性机械通气策略的方法,来降低呼吸机相关性肺损伤（VILI）。FRC在机械通气患者中的临床应用越来越受到重视,在病情评估、ARDS患者中的肺保护通气设置和麻醉时肺部情况监测等方面具有重要临床意义。本文对FRC的病理生理功能、检测方法及在重症患者中的应用进行综述。     

Oxidative damage to proteins of bronchoalveolar lavage fluid in patients with acute respiratory distress syndrome: evidence for neutrophil-mediated hydroxylation, nitration, and chlorination.

OBJECTIVE: To assess the degree, source, and patterns of oxidative damage to bronchoalveolar lavage proteins as a modification of amino acid residues in patients with acute respiratory distress syndrome (ARDS). DESIGN: Prospective, controlled study. SETTING: Adult intensive care unit of a postgraduate teaching hospital. PATIENTS: Twenty-eight patients with established ARDS were studied and compared with six ventilated patients without ARDS and 11 normal healthy controls. INTERVENTIONS: Supportive techniques appropriate to ARDS. MEASUREMENTS AND MAIN RESULTS: Evidence of oxidative modification of bronchoalveolar lavage fluid protein, indicative of the production of specific reactive oxidizing species, was sought using a high-performance liquid chromatography technique. Bronchoalveolar lavage fluid samples from patients with ARDS, ventilated intensive care controls, and normal healthy controls were analyzed. Concentrations of orthotyrosine were significantly higher in the ARDS group than in either control group (7.98 + 3.78 nmol/mg for ARDS, 0.67 + 0.67 for ventilated controls, and 0.71 + 0.22 for healthy controls; p < .05). Chlorotyrosine concentrations were also significantly increased in the ARDS group over either control group (4.82 + 1.07 nmol/mg for ARDS, 1.55 + 1.34 for ventilated controls, and 0.33 + 0.12 for healthy controls; p < .05). Nitrotyrosine concentrations were similarly significantly increased in the ARDS groups compared with each control group (2.21 + 0.65 nmol/mg for ARDS, 0.29 + 0.29 for ventilated controls, and 0.06 + 0.03 for healthy controls; p < .05). Chlorotyrosine and nitrotyrosine concentrations showed significant correlations with myeloperoxidase concentrations in bronchoalveolar lavage fluid, measured using an enzyme-linked immunosorbent assay in patients with ARDS. These findings suggest a possible relationship between inflammatory cell activation, oxidant formation, and damage to proteins in the lungs of these patients CONCLUSIONS: Overall, our data strongly suggest heightened concentrations of oxidative stress in the lungs of patients with ARDS that lead to significantly increased oxidative protein damage.     

Mechanical ventilation in acute respiratory failure: recruitment and high positive end-expiratory pressure are necessary

PURPOSE OF REVIEW: To review as best the critical care clinicians can recruit the acute respiratory distress syndrome (ARDS) lungs and keep the lungs opened, assuring homogeneous ventilation, and to present the experimental and clinical results of these mechanical ventilation strategies, along with possible improvements in patient outcome based on selected published medical literature from 1972 to 2004 (highlighting the period from June 2003 to June 2004 and recent results of the authors' group research). RECENT FINDINGS: In the experimental setting, repeated derecruitments accentuate lung injury during mechanical ventilation, whereas open lung concept strategies can attenuate lung injury. In the clinical setting, recruitment maneuvers improve short-term oxygenation in ARDS patients. A recent prospective clinical trial showed that low versus intermediate positive end-expiratory pressure (PEEP) levels (8 vs 13 cm H2O) associated with low tidal ventilation had the same effect on ARDS patient survival. Nevertheless, both conventional and electrical impedance thoracic tomography studies indicate that stepwise PEEP recruitment maneuvers increase lung volume and the recruitment percentage of lung tissue, and higher levels of PEEP (18-26 cm H2O) are necessary to keep the ARDS lungs opened and assure a more homogeneous low tidal ventilation. SUMMARY: Stepwise PEEP recruitment maneuvers can open collapsed ARDS lungs. Higher levels of PEEP are necessary to maintain the lungs open and assure homogenous ventilation in ARDS. In the near future, thoracic CT associated with high-performance monitoring of regional ventilation (electrical impedance tomography) may be used at the bedside to determine the optimal mechanical ventilation of ARDS patients.     

Functional residual capacity and lung mechanics at different levels of mechanical ventilation

We assessed the effects of rapid ventilatory rates (60 to 120 breath/min) and high mechanical ventilation pressures (30/5 to 40/10 cm H2O) on lung mechanics and intravascular pressures in 9 paralyzed, sedated rabbits ventilated with a time-cycled, pressure-limited flow generator (Baby bird). Measurements of tidal volume, ventilator line pressure, tracheal pressure, functional residual capacity (FRC), and arterial and venous blood pressures showed that: 68% of the peak pressure developed by the ventilator was transmitted to the trachea at 60 breath/min, 74% at 120 breath/min, and 87% when ventilation pressures were increased to 40/10 cm H2O; when the ventilatory rate and the PEEP were increased, the end-expiratory pressure in the trachea became progressively greater than that indicated on the ventilator pressure gauge; FRC increased when the PEEP and mean tracheal pressure increased; tidal volume and dynamic compliance decreased and minute ventilation increased as ventilatory rate increased; compliance decreased whenever FRC increased, and increased whenever FRC decreased; and there was little effect on mean central venous or arterial pressure. These data indicate that increasing ventilator rates cause gas trapping within the lung. In normal animals, this may interfere with gas exchange and pulmonary blood flow. In abnormal lungs, the gas trapping may increase FRC and improve gas exchange within the lung.     

Low-dose CT for quantitative analysis in acute respiratory distress syndrome

Introduction

The clinical use of serial quantitative computed tomography (CT) to characterize lung disease and guide the optimization of mechanical ventilation in patients with acute respiratory distress syndrome (ARDS) is limited by the risk of cumulative radiation exposure and by the difficulties and risks related to transferring patients to the CT room. We evaluated the effects of tube current-time product (mAs) variations on quantitative results in healthy lungs and in experimental ARDS in order to support the use of low-dose CT for quantitative analysis.

Methods

In 14 sheep chest CT was performed at baseline and after the induction of ARDS via intravenous oleic acid injection. For each CT session, two consecutive scans were obtained applying two different mAs: 60 mAs was paired with 140, 15 or 7.5 mAs. All other CT parameters were kept unaltered (tube voltage 120 kVp, collimation 32 × 0.5 mm, pitch 0.85, matrix 512 × 512, pixel size 0.625 × 0.625 mm). Quantitative results obtained at different mAs were compared via Bland-Altman analysis.

Results

Good agreement was observed between 60 mAs and 140 mAs and between 60 mAs and 15 mAs (all biases less than 1%). A further reduction of mAs to 7.5 mAs caused an increase in the bias of poorly aerated and nonaerated tissue (-2.9% and 2.4%, respectively) and determined a significant widening of the limits of agreement for the same compartments (-10.5% to 4.8% for poorly aerated tissue and -5.9% to 10.8% for nonaerated tissue). Estimated mean effective dose at 140, 60, 15 and 7.5 mAs corresponded to 17.8, 7.4, 2.0 and 0.9 mSv, respectively. Image noise of scans performed at 140, 60, 15 and 7.5 mAs corresponded to 10, 16, 38 and 74 Hounsfield units, respectively.

Conclusions

A reduction of effective dose up to 70% has been achieved with minimal effects on lung quantitative results. Low-dose computed tomography provides accurate quantitative results and could be used to characterize lung compartment distribution and possibly monitor time-course of ARDS with a lower risk of exposure to ionizing radiation. A further radiation dose reduction is associated with lower accuracy in quantitative results.     

Increased plasma levels of heparin-binding protein in patients with acute respiratory distress syndrome

Introduction

Heparin-binding protein (HBP) is an antimicrobial protein stored in neutrophil granules and plays a role in endothelial permeability regulation. The aim was to assess the diagnostic and prognostic value of measuring HBP in patients with acute lung injury (ALI)/acute respiratory distress syndrome (ARDS).

Methods

Plasma HBP was collected from 78 patients with ALI/ARDS, 28 patients with cardiogenic pulmonary edema (CPE) and 20 healthy volunteers at enrollment. Levels of HBP were measured by ELISA.

Results

Patients with ALI/ARDS had significantly higher median levels of HBP compared with patients with CPE (17.15 (11.95 to 24.07) ng/ml vs. 9.50 (7.98 to 12.18) ng/ml, P <0.001) at enrollment. There was no significant difference between CPE patients and healthy subjects in terms of HBP value (P = 0.372). The HBP levels of nonsurvivors was significantly higher than that of survivors (23.90 (14.81 to 32.45) ng/ml vs. 16.01 (10.97 to 21.06) ng/ml, P = 0.012) and multivariate logistic regression showed HBP (odds ratio =1.52, P = 0.034) was the independent predictor for 30-day mortality in patients with ALI/ARDS.

Conclusions

Plasma HBP levels of ALI/ARDS patients were significantly higher than that of CPE patients. HBP was a strong prognostic marker for short-term mortality in ALI/ARDS.     

An Ultrasound Surface Wave Technique for Assessing Skin and Lung Diseases

Systemic sclerosis (SSc) is a multi-organ connective tissue disease characterized by immune dysregulation and organ fibrosis. Severe organ involvement, especially of the skin and lung, is the cause of morbidity and mortality in SSc. Interstitial lung disease (ILD) includes multiple lung disorders in which the lung tissue is fibrotic and stiffened. The purpose of this study was to translate ultrasound surface wave elastography (USWE) for assessing patients with SSc and/or ILD via measuring surface wave speeds of both skin and superficial lung tissue. Forty-one patients with both SSc and ILD and 30 healthy patients were enrolled in this study. An external harmonic vibration was used to generate the wave propagation on the skin or lung. Three excitation frequencies of 100, 150 and 200?Hz were used. An ultrasound probe was used to measure the wave propagation in the tissue non-invasively. Surface wave speeds were measured on the forearm and upper arm of both left and right arm, as well as the upper and lower lungs, through six intercostal spaces of patients and healthy patients. Viscoelasticity of the skin was calculated by the wave speed dispersion with frequency using the Voigt model. The magnitudes of surface wave speed and viscoelasticity of patients' skin were significantly higher than those of healthy patients (p?<0.0001) for each location and each frequency. The surface wave speeds of patients' lung were significantly higher than those of healthy patients (p?<0.0001) for each location and each frequency. USWE is a non-invasive and non-ionizing technique for measuring both skin and lung surface wave speed and may be useful for quantitative assessment of SSc and/or ILD.     

Components of excess ventilation in patients initiated on mechanical ventilation

OBJECTIVE: To determine the causes of excess minute ventilation in patients initiated on mechanical ventilation. DESIGN: Prospective study of recently intubated, mechanically ventilated patients. SETTING: The medical ICU in a county hospital. PATIENTS: Fifty-two mechanically ventilated medical ICU patients were studied within 36 hrs of intubation. Patients were all supported with volume-cycled ventilation in the assist-control mode. INTERVENTIONS: Timed expired gas collection and an arterial blood gas. MEASUREMENTS AND MAIN RESULTS: Measurements of minute ventilation and CO2 production (VCO2) were made from a timed expired gas collection. PaCO2 was sampled during the gas collection and deadspace was determined. Minute ventilation, VCO2, deadspace, and PaCO2 values in the patients were compared with predicted normal values, and excess minute ventilation due specifically to each component was calculated. Patients were separated clinically into groups: adult respiratory distress syndrome (ARDS), sepsis, obstructive lung disease, pneumonia, and drug overdose. Comparisons were then made between groups. Excess minute ventilation for the entire study population was secondary to increased deadspace (39%), low PaCO2 (36%), increased VCO2 (15%), and the interactive effect of deadspace and VCO2 (10%). VCO2 contributed little to excess minute ventilation early in respiratory failure, even in the ARDS and sepsis groups. Deadspace contributed significantly to excess minute ventilation in all groups, especially in the ARDS group, where it accounted for 53% of the excess ventilation. Low PaCO2 set-point was the predominant cause of excess minute ventilation in the sepsis group, where it contributed to 57% of their total excess minute ventilation. CONCLUSIONS: Although all groups initiated on mechanical ventilation had an excess ventilatory requirement, the contribution of individual components varied considerably between clinical groups.     

The effect of high-frequency oscillatory ventilation combined with tracheal gas insufflation on extravascular lung water in patients with acute respiratory distress syndrome: A randomized,crossover, physiologic study

Purpose

High-frequency oscillation combined with tracheal gas insufflation (HFO-TGI) improves oxygenation in patients with acute respiratory distress syndrome (ARDS). There are limited physiologic data regarding the effects of HFO-TGI on hemodynamics and pulmonary edema during ARDS. The aim of this study was to investigate the effect of HFO-TGI on extravascular lung water (EVLW).

Materials and methods

We conducted a prospective, randomized, crossover study. Consecutive eligible patients with ARDS received sessions of conventional mechanical ventilation with recruitment maneuvers (RMs), followed by HFO-TGI with RMs, or vice versa. Each ventilatory technique was administered for 8 hours. The order of administration was randomly assigned. Arterial/central venous blood gas analysis and measurement of hemodynamic parameters and EVLW were performed at baseline and after each 8-hour period using the single-indicator thermodilution technique.

Results

Twelve patients received 32 sessions. Pao₂/fraction of inspired oxygen and respiratory system compliance were higher (P < .001 for both), whereas extravascular lung water index to predicted body weight and oxygenation index were lower (P = .021 and .029, respectively) in HFO-TGI compared with conventional mechanical ventilation. There was a significant correlation between Pao₂/fraction of inspired oxygen improvement and extravascular lung water index drop during HFO-TGI (Rs = − 0.452, P = .009).

Conclusions

High-frequency oscillation combined with tracheal gas insufflation improves gas exchange and lung mechanics in ARDS and potentially attenuates EVLW accumulation.     

Differential evaluation of bronchoalveolar lavage cells and leukotrienes in unilateral acture lung injury and ARDS patients

Patients with unilateral acute lung injury (UALI; n=6) and ARDS (n=4) were evaluated by bronchoalveolar lavage, as controls we used 5 patients suffering from cerebral hemorrhage and without pulmonary, cardiac or infectious disease who were mechanically ventilated. For each group of patients two independent bronchoalveolar lavages (BAL) were performed. The BAL fluid recovered from the two lungs was immediately analyzed for leukotrienes (LTS) by means of RP-HPLC and stained for cell counts. The BAL from the control group did not show any LTS and the percentage of neutrophils was within the normal range: 1±0.2% right lung and 1.2±0.4% left lung. The BAL fluid from UALI patients showed two different patterns, the injured lung showed high levels of LTS (39.1±8 ng ml^-1 LTB₄; 25±6 ng ml^-1 LTD₄ and 27.8±8.2 ng ml^-111-trans LTC₄) and an increased percentage of neutrophils (74.2±7%) compared to controls. Only 2 out of the 6 patients from the UALI group showed small amounts of LTB₄ (4 ng ml^-1) and LTD₄ (3.2 ng ml^-1). The BAL obtained from the healthy lung in both cases showed values of LTS almost eight fold lower than those present in the injured lung. The percentage of neutrophils from the unaffected lungs (4.3±7%) was not significantly different from controls. Lavage fluid from ARDS patients showed a similar picture to that of the affected lung from UALI patients. Evaluation of ARDS lavage fluid demonstrated the presence of the same LTS (LTB₄, LTD₄ and 11-trans LTC₄) with concentrations similar to those found in the injured lung of UALI subjects. The amount of LTB₄ (a very potent chemotatic factor) correlated directly with the percentage of neutrophils both in ARDS and the diseased lung of UALI patients. These findings suggest that LTS and neutrophils participate in the pathophysiology of UALI and ARDS, and that UALI is a localized pathologic entity similar to ARDS.The data from this study have been partially presented, as communication, during the 4th European Congress on Intensive Care Medicine in Baveno, June 14–18, 1988.This work is partially supported by MPI 601 CAP 02112.01.04 1984/1989.     

基于体素观察慢性阻塞性肺疾病肺叶损伤程度及空间分布

目的 探讨基于体素定量CT分析慢性阻塞性肺疾病（COPD）患者肺叶损伤程度及空间分布的价值。方法 在"数字肺"多研究中心连续性纳入接受双气相扫描COPD患者，测定小气道病变（fSAD）和肺气肿（Emph）的定量值；分析患者各肺叶之间Emph、fSAD肺叶损伤程度及肺叶分布的差异，以及各肺叶定量CT分布与肺功能的相关性。结果 最终纳入50例COPD患者。Emph和fSAD均以右肺中叶最重，两肺上叶次之，两肺下叶程度最轻；Emph和fSAD均主要分布于左肺上叶，其次为右肺上叶，右肺中叶分布最少。两肺下叶Emph和fSAD与FEV₁%的相关性较好。结论 COPD患者肺叶损伤程度以右肺中叶及两肺上叶为重，尤其是右肺中叶；Emph和fSAD主要分布于左肺上叶，其次是右肺上叶；两肺下叶损伤对COPD患者肺功能的影响更著。     

Interleukin-2 involvement in early acute respiratory distress syndrome: relationship with polymorphonuclear neutrophil apoptosis and patient survival

OBJECTIVE: To determine blood and lung alveolar concentrations of interleukin (IL)-2 in acute respiratory distress syndrome (ARDS) and their relationship with polymorphonuclear neutrophil (PMN) apoptosis and patient survival. DESIGN: Prospective cohort study. SETTING: Medical and surgical intensive care units (ICUs; Canada) and the intensive care department (Belgium). PATIENTS: Nineteen consecutive patients with ARDS, 14 non-ARDS ICU patients, and 20 healthy volunteers. INTERVENTIONS: Blood samples and bronchoalveolar lavages (BAL) obtained via venous puncture and by fiberoptic bronchoscopy in the first 72 hrs after the onset of ARDS. MEASUREMENTS AND MAIN RESULTS: One early point concentration of IL-2 was measured in both blood and BAL fluids of the three groups. In vivo alveolar PMN apoptotic index in BAL fluids and the influence of BAL fluid exposure on normal blood PMN spontaneous apoptosis in vitro were evaluated. Blood IL-2 was significantly lower in patients with ARDS compared with non-ARDS ICU patients and controls. In contrast, IL-2 in BAL fluids of patients with ARDS was dramatically elevated compared with non-ARDS ICU patients and controls. ARDS survivors exhibited lower early IL-2 blood levels than nonsurvivors and generally had a higher IL-2 lung content Lung alveolar PMN apoptosis in vivo was lower in patients with ARDS in comparison with controls. This apoptotic index was correlated with corresponding IL-2 alveolar levels in patients with ARDS. Exposure of normal blood PMN to BAL fluids from patients with ARDS delayed apoptosis in vitro. Immunodepletions of IL-2, granulocyte-macrophage colony stimulating factor, and a combination of both cytokines from BAL fluids of ARDS patients significantly restored PMN apoptosis. The recovery of PMN apoptosis was more effective when IL-2 was depleted in BAL fluids from ARDS survivors compared with nonsurvivors. CONCLUSIONS: Opposite and disproportional concentrations of IL-2 are observed in blood and lung fluids of patients with early ARDS. IL-2 significantly contributes (with granulocyte-macrophage colony stimulating factor) to the inhibition of PMN apoptosis in BAL fluids of patients with ARDS. Early low blood IL-2 and high IL-2-driven inhibition of PMN apoptosis are beneficial to survivors. Thus, IL-2 is a new candidate for monitoring in early ARDS and an interesting indicator of prognosis.