Risk factors for ARDS in patients receiving mechanical ventilation for > 48 h

BACKGROUND: Low tidal volume (Vt) ventilation for ARDS is a well-accepted concept. However, controversy persists regarding the optimal ventilator settings for patients without ARDS receiving mechanical ventilation. This study tested the hypothesis that ventilator settings influence the development of new ARDS. METHODS: Retrospective analysis of patients from the Multi Parameter Intelligent Monitoring of Intensive Care-II project database who received mechanical ventilation for > or = 48 h between 2001 and 2005. RESULTS: A total of 2,583 patients required > 48 h of ventilation. Of 789 patients who did not have ARDS at hospital admission, ARDS developed in 152 patients (19%). Univariate analysis revealed high peak inspiratory pressure (odds ratio [OR], 1.53 per SD; 95% confidence interval [CI], 1.28 to 1.84), increasing positive end-expiratory pressure (OR, 1.35 per SD; 95% CI, 1.15 to 1.58), and Vt (OR, 1.36 per SD; 95% CI, 1.12 to 1.64) to be significant risk factors. Major nonventilator risk factors for ARDS included sepsis, low pH, elevated lactate, low albumin, transfusion of packed RBCs, transfusion of plasma, high net fluid balance, and low respiratory compliance. Multivariable logistic regression showed that peak pressure (OR, 1.31 per SD; 95% CI, 1.08 to 1.59), high net fluid balance (OR, 1.3 per SD; 95% CI, 1.09 to 1.56), transfusion of plasma (OR, 1.26 per SD; 95% CI, 1.07 to 1.49), sepsis (OR, 1.57; 95% CI, 1.00 to 2.45), and Vt (OR, 1.29 per SD; 95% CI, 1.02 to 1.52) were significantly associated with the development of ARDS. CONCLUSIONS: The associations between the development of ARDS and clinical interventions, including high airway pressures, high Vt, positive fluid balance, and transfusion of blood products, suggests that ARDS may be a preventable complication in some cases.     

GI complications in patients receiving mechanical ventilation

Mechanical ventilation (MV) can be lifesaving by maintaining gas exchange until the underlying disorders are corrected, but it is associated with numerous organ-system complications, which can significantly affect the outcome of critically ill patients. Like other organ systems, GI complications may be directly attributable to MV, but most are a reflection of the severity of the underlying disease that required intensive care. The interactions of the underlying critical illness and MV with the GI tract are complex and can manifest in a variety of clinical pictures. Incorporated in this review are discussions of the most prevalent GI complications associated with MV, and current diagnosis and management of these problems.     

Persistent air leaks in patients receiving mechanical ventilation

The term bronchopleural fistula (BPF) can be loosely defined as persistent leakage of gas from the airways into the pleural space. A true BPF, however, is located in the central airways, whereas leaks located peripherally are better described by the term parenchymal-pleural fistula (PPF). The presence of a persistent leak in a mechanically ventilated patient is a worrisome prognostic sign independent of the precise origin, yet it is important to distinguish BPF from PPF in this population. Fundamental differences in the pathogenesis and natural history of these two entities dictate divergent approaches to management. This review compares and contrasts the evaluation and management of BPF and PPF in patients receiving mechanical ventilation, and provides an overview of the many nonsurgical interventions used to manage persistent leaks.     

Safety of ultrasound-guided thoracentesis in patients receiving mechanical ventilation

OBJECTIVE: To determine the safety of ultrasound-guided thoracentesis (UST) performed by critical care physicians on patients receiving mechanical ventilation. DESIGN: Prospective and observational. SETTING: ICUs in a teaching hospital. PATIENTS: Two hundred eleven serial patients receiving mechanical ventilation with pleural effusion requiring diagnostic or therapeutic thoracentesis. INTERVENTIONS: Two hundred thirty-two separate USTs were performed by critical care physicians without radiology support. Anteroposterior chest radiographs were reviewed for possible postprocedure pneumothorax. RESULTS: Pneumothorax occurred in 3 of 232 USTs (1.3%). The procedure was well tolerated in this critically ill population. CONCLUSIONS: UST performed in patients receiving mechanical ventilation without radiology support results in an acceptable rate of pneumothorax.     

Role of transbronchial needle aspiration in patients receiving mechanical ventilation

STUDY OBJECTIVE:s: To evaluate the diagnostic accuracy and safety of transbronchial needle aspiration (TBNA) in patients receiving mechanical ventilation in the ICU. METHODS: Retrospective review of all patients in the medical and surgical ICUs from February 1999 to July 2001 who underwent TBNA while receiving mechanical ventilation. RESULTS: A total of eight histology (19 gauge) and eight cytology (22 gauge) TBNAs were performed on eight patients (four men and four women). TBNA yielded a definitive pathologic diagnosis in five of eight patients (62.5%). Diagnoses were posttransplantation lymphoproliferative disorder, large cell carcinoma, poorly differentiated non-small cell carcinoma, squamous cell carcinoma, and adenocarcinoma. Among patients with negative TBNA results (n = 3), two patients underwent mediastinoscopy. Results of mediastinoscopy were non-small cell carcinoma and inflamed tissue. TBNA led to management changes in five of these patients. Excluding one patient in whom a negative TBNA result could not be further confirmed, TBNA yielded a sensitivity of 83%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 50%. The overall accuracy of the procedure was 75%. There were no complications following any of the TBNAs. CONCLUSIONS: In this small group of patients, TBNA was safe and had a high diagnostic accuracy in selected patients receiving mechanical ventilation in the ICU.     

A descriptive evaluation of transfusion practices in patients receiving mechanical ventilation

STUDY OBJECTIVES: To characterize and compare transfusion practices in a broad sample of patients receiving mechanical ventilation (MV) and not receiving MV in the ICU. DESIGN: Retrospective subgroup analysis from the prospective, multicenter, observational CRIT study. SETTING: Two hundred eighty-four medical, surgical, or medical/surgical ICUs. PATIENTS: Critically ill adults.Main results: Of the 4,892 patients enrolled in the CRIT study, 60% were receiving MV on ICU admission or within 48 h after admission for a median of 4 days. Patients receiving MV had higher baseline APACHE (acute physiology and chronic health evaluation) II scores than patients not receiving MV (22.8 +/- 7.8 and 14.9 +/- 6.4, respectively [mean +/- SD]; p < 0.0001). Despite similar baseline hemoglobin levels (11.0 +/- 2.3 g/dL and 10.9 +/- 2.5 g/dL, p = 0.17), more patients receiving MV underwent transfusions (49% vs 33%, p < 0.0001), and they received significantly more RBCs than patients not receiving MV (p < 0.0001). The principal reason for transfusion in both groups was low hemoglobin level (78.4% and 84.6%, respectively); however, patients receiving MV had higher pretransfusion hemoglobin levels (8.7 +/- 1.7 g/dL) than patients not receiving MV (8.2 +/- 1.7 g/dL, p < 0.0001). Notably, 40.1% of all transfusions in patients receiving MV were administered after day 3 of the ICU stay, compared to 21.2% in patients not receiving MV (p < 0.0001), and a higher percentage of patients receiving MV remaining in the ICU after day 3 underwent transfusions (33.4% vs 18.3%, p < 0.0001). Mortality was higher (17.2% vs 4.5%, p < 0.0001) and mean hospital (15 days vs 10 days, p < 0.0001) and ICU stays (9 days vs 4 days, p < 0.0001) were longer in the subgroup receiving MV. CONCLUSIONS: Mechanical ventilation appears to be an easily identifiable early marker for allogeneic blood exposure risk in ICU patients. While the longer ICU stays account for much of this risk, patients receiving MV also appear to undergo transfusions at higher hemoglobin thresholds than patients not receiving MV, at least early in the ICU stay. Justification of this relatively liberal transfusion practice in patients receiving MV will require further study.     

Does intermittent mandatory ventilation correct respiratory alkalosis in patients receiving assisted mechanical ventilation?

One of the claimed advantages of intermittent mandatory ventilation (IMV) over assisted mechanical ventilation (AMV) (assist-control) is the avoidance or correction of acute respiratory alkalosis, ostensibly by allowing patients to achieve normal alveolar ventilation (VA) and PaCO2 through the function of an intact ventilatory drive. However, although respiratory alkalosis in patients being hyperventilated with controlled mechanical ventilation (CMV) can be corrected by a change to IMV, CMV is seldom appropriate for patients with acute respiratory failure, and whether IMV affects respiratory alkalosis in patients triggering the ventilator in the AMV mode has not previously been tested. We studied 26 patients with acute respiratory alkalosis (pH greater than or equal to 7.48) while receiving AMV. Measurements of arterial blood gases and CO2 production (VCO2), and calculation of VA, were performed after 30 min of AMV, repeated after 30 min of IMV at a mandatory rate one half the previous AMV rate, and then repeated again 30 min after a return to the original AMV settings. Mean arterial pH decreased slightly from 7.51 during AMV to 7.48 during IMV, and returned to 7.51 on resumption of AMV (p less than 0.05 for both changes); corresponding mean values for PaCO2 were 28.6, 29.7, and 27.5 mmHg, respectively. These changes were related to an increase in VCO2 during IMV as compared with AMV (p less than 0.05), without a significant alteration in VA. When the mandatory rate was further reduced during IMV from one half to one fourth the prior, triggered AMV rate in 10 patients, no additional reduction in pH occurred.(ABSTRACT TRUNCATED AT 250 WORDS)     

Usefulness of pleural complement activation products in differentiating tuberculosis and malignant effusions.

OBJECTIVE: To determine whether measurement of the complement activation products SC5b-9 and C3a-desArg in pleural fluid can reliably differentiate tuberculous from malignant pleural effusions. DESIGN: Twenty-four patients with tuberculous pleuritis, 29 with malignant pleural effusion, and 30 control subjects with transudates were enrolled in the study. SCSb-9 and C3a-desArg were measured in pleural fluid using commercial ELISA tests, and their performances were evaluated using receiver operating characteristic (ROC) analysis. RESULTS: Patients with tuberculous pleuritis had higher mean levels of pleural SC5b-9 (5052 microg/L) and C3a-desArg (7436 microg/L) than those with malignant effusions (1048 and 2835 microg/L, respectively), whereas only SC5b-9 concentrations in the latter were comparable with controls. The area under the ROC curve (AUC) was 0.84 for SC5b-9 and 0.81 for C3a-desArg. Pleural SC5b-9 showed an accuracy of 80.8%, compared with 78.8% for C3a-desArg, when cut-off points of 1500 and 4500 microg/L, respectively, were used. Using a stepwise logistic regression model, the combination of pleural SCSb-9 > or =1500 microg/L, age < or =35 years, and pleural monocyte percentage > or =90% provided the highest accuracy for tuberculous pleurisy (88.5%, AUC 0.95). CONCLUSION: This pilot study suggests that pleural SC5b-9 is clinically useful for differentiating tuberculous and malignant pleural effusions.     

Usefulness of the British Thoracic Society and the American College of Chest Physicians guidelines in predicting pleural drainage of non-purulent parapneumonic effusions

AIM: To assess the value of the British Thoracic Society (BTS) and the American College of Chest Physicians (ACCP) guidelines to predict which patients with non-purulent parapneumonic effusions (PPE) warrant chest tube drainage. METHODS: A retrospective chart review was performed on all patients who underwent thoracentesis because of a PPE over a 10-year period at a Spanish medical center. Classification of PPE as complicated (CPPE) or uncomplicated (UPPE) was based on the clinician's decision to insert a chest tube to resolve the effusion. Empyema was defined as pus in the pleural space. Data collected included patient demographics, size of the effusion, and microbiological and pleural fluid chemistries that might influence the physician's decision to place a chest tube. RESULTS: Of the 240 patients with PPE who entered the study, 85 had UPPE, 67 had CPPE, and 88 had empyema. Individual pleural fluid parameters, namely a pH<7.20, a glucose<40 mg/dL or <60 mg/dL, a LDH>1000 U/L or a positive culture had a relatively high specificity (from 78% for LDH to 94% for glucose<40 mg/dL), but low to moderate sensitivity (from 25% for culture to 73% for LDH) in predicting the need for chest tube placement in non-purulent PPE. While pleural fluid cultures performed poorly in discriminating UPPE from CPPE (likelihood ratio positive 1.7), effusion's size performed the best (likelihood ratio positive 5.7). BTS and ACCP guidelines yielded measures of sensitivity (98% and 97%, respectively), and negative likelihood ratio (0.03 and 0.05, respectively) for identifying a CPPE. CONCLUSIONS: Both guidelines have similar accuracy and perform satisfactorily in distinguishing CPPE from UPPE, albeit at an admissible cost of needlessly increasing chest tube drainage.     

Prognosis of noncardiac medical patients receiving mechanical ventilation in a veterans hospital

In order to determine prognostic factors in noncardiac medical patients treated by mechanical ventilation in a Veterans Administration hospital, 78 patient records were reviewed. Disease severity was scored by the Acute Physiology and Chronic Health Evaluation (APACHE) II system. Physicians' prior impressions of prognostic factors were compared with the actual results of this study. Most patients were middle-aged men with respiratory diseases. Fifty-nine patients (76 percent) died in the hospital. Survivors of hospitalization and nonsurvivors had similar age, diagnoses, emergency intubations, duration of ventilation, and pH and oxygen tension after 24 hours of ventilation. However, only one of 31 patients with a serum albumin level of 2.5 g/dl or less at the initiation of mechanical ventilation survived (p less than 0.001). Of 24 patients requiring a fractional inspired oxygen concentration greater than 50 percent at 24 hours, none survived (p less than 0.005). At all APACHE II scores, the mortality rates documented in this study were higher than predicted. Physicians overestimated the impact of several variables, including age and presence of pneumonia, on mortality. At the San Francisco Veterans Administration Medical Center, a low serum albumin level may aid in the decision whether to begin mechanical ventilation, and a high fractional inspired oxygen concentration at 24 hours may aid in the decision regarding further aggressive care. These findings need to be validated in other patients before being applied. Conversely, certain older patients, and those undergoing emergency intubation or intubation for a prolonged time, may have as good a prognosis as patients without these factors.     

Factors related to quality of life in patients receiving home mechanical ventilation

OBJECTIVES: The objective of this study was to evaluate factors associated with health-related quality of life (HRQOL) among patients receiving home mechanical ventilation (HMV). METHODS: Observational, cross-sectional study. Patients receiving HMV were recruited from hospital outpatients facilities at five participating centers; a single follow-up visit was scheduled. The Spanish version of the Severe Respiratory Insufficiency (SRI) Questionnaire was used and the following variables were collected: socio-demographic status, previous medical history (Charlson-Age Comorbidity Index), current symptoms, administration of questionnaires, pulmonary function tests (PFT), current ventilatory support, and oxygen therapy. RESULTS: One hundred and fifteen patients (57 males and 58 females, mean age 62+/-13 years) were investigated. The reasons for HMV were as follows: thoracic cage abnormalities (33 patients), obesity hypoventilation syndrome (37 patients), neuromuscular disorders (18 patients), sequelae of tuberculosis (12 patients), and chronic obstructive pulmonary disease (15 patients). In a bivariate approach, dyspnea, the number of hospitalizations, and the number of emergency room admissions in last year were the main predictors of each HRQOL dimension. Multivariate analysis showed that dyspnea, FEV(1)/FVC, and the number of hospitalizations in the previous year were independently associated with HRQOL. CONCLUSIONS: HRQOL of patients receiving HMV is influenced by many factors, especially by dyspnea and the number of admissions. An obstructive pattern in the PFT also influences HRQOL. These findings may have therapeutic implications.     

Survival of individuals receiving long-term mechanical ventilation

The reports published to date support the concept that LTMV can extend life for patients with respiratory insufficiency, particularly adults and children with neuromuscular and chest wall diseases. The impact of LTMV on survival in patients with obstructive lung diseases, such as COPD and bronchiectasis, is less clear and deserves further study. For all disease states, research is needed to determine the characteristics of patients who are most likely to benefit from LTMV and whether one method of ventilation is superior to another. In addition to survival, other important outcomes, such as patient satisfaction, quality of life, and costs associated with LTMV, should be assessed in future long-term studies.     

机械通气相关胸腔积液25例临床分析

目的研究机械通气(MV)患者并发胸腔积液的临床特点。方法观察机械通气治疗后并发胸腔积液25例患者的临床资料,分析机械通气相关胸腔积液患者的病情特点及相关因素。结果 25例发生胸腔积液的患者中14例为渗出液,病因为肺炎旁积液和肺栓塞相关胸腔积液;11例为漏出液,病因为低蛋白血症和心力衰竭。结论 MV患者行床边超声指导下的胸腔穿刺是安全的,肺炎旁积液及低蛋白血症、心衰诱发的胸腔积液是最主要的病因。     

Effectiveness of tunneled pleural catheter placement in patients with malignant pleural effusions

Pleural effusions (PE) occur frequently among patients with various types of advanced malignancies, resulting in remarkably decreased quality of life. Treatment of malignant PE includes placement of a chest tube with subsequent placement of a tunneled pleural catheter. We reviewed our experience with tunneled pleural catheter use to assess outcomes and resource utilization of this intervention. A retrospective study of consecutive patients (n = 163, including 41 outpatients) who were treated between July 2001 and April 2008 with tunneled pleural catheters was performed to evaluate operative and discharge outcomes. The average age of the patients was 59.32 years (range: 24 to 89). Lung cancer, breast cancer, and ovarian cancer were common primary diseases in this patient population. The mean hospital stay after tunneled pleural catheter placement was 3.19 days (range: 0 to 56), with 41 patients treated as outpatients. Thirteen inpatient deaths were related to the patients'' primary diseases, but no deaths were due to drain placement itself. Eight patients (4.91%) required reoperation to replace a nonfunctioning drain or to add an additional drain, and six patients underwent a second procedure to place a contralateral drain. One hundred twenty-six patients (77.30%) were discharged home following the procedure and hospital stay. Fifty-five people achieved spontaneous pleurodesis. Tunneled pleural catheter placement is a safe and effective approach to the treatment of PE. The advantages of tunneled pleural catheter placement include symptomatic relief and improved quality of life. This method allows patients to spend time at home with their family and avoid prolonged hospitalization.     

Risk factors for pneumonia and fatality in patients receiving continuous mechanical ventilation

We studied risk factors for nosocomial pneumonia and fatality in 233 intensive care unit patients requiring continuous mechanical ventilation. Ventilator-associated pneumonia was diagnosed in 49 (21%) of the 233 patients. Of the 8 risk factors univariately associated with the development of pneumonia, only the presence of an intracranial pressure monitor (p less than 0.002), treatment with cimetidine (p less than 0.01), hospitalization during fall-winter seasons (p less than 0.04), and mechanical ventilator circuit changes every 24 h rather than every 48 h (p less than 0.02) remained significant after stepwise logistic regression. The overall fatality rate for the 49 patients who developed ventilator-associated pneumonia was 55%. Ventilator-associated pneumonia was 1 of 18 variables univariately associated with overall patient fatality, but it was not among the 7 variables present after multivariate analysis. The data delineate risk factors associated with the development of nosocomial pneumonia and fatality in patients receiving continuous mechanical ventilation.     

Health-related auality of life (HRQL) in patients receiving home mechanical ventilation

Evaluation of health-related quality of life (HRQL) has become steadily more essential during the last two decades in research and health care practice in order to evaluate the human and financial costs and benefits of modern medical techniques. HRQL in its definition is based on different components of health including physical state, psychological well-being, social relations and functional capacities that are influenced by a persons experience, beliefs, expectations, and perceptions. For the purpose of assessment of HRQL several instruments have been developed. Generic instruments are not specific to any particular disease and are therefore most commonly used for general survey research on health allowing comparisons between disease states. In contrast, disease-specific questionnaires which are necessary in order to focus on domains most relevant to a particular disease are thought to be more sensitive than generic instruments following therapeutic interventions. Home mechanical ventilation (HMV) delivered noninvasively by a facial mask is a well established treatment for chronic hypercapnic respiratory failure. It is widely accepted that survival improves following institution of HMV in most patients with chest wall deformities or neuromuscular diseases while this is still controversially discussed in patients with COPD. However, patients receiving HMV usually have severe respiratory insufficiency with a past medical history of several years or decades, and suffer from end stage disease with objectively severe limitations of daily living. In addition, HMV is a time consuming and cost intensive therapy. Therefore, several studies have been conducted in the last decade to evaluate HRQL in patients receiving HMV. Recent studies using generic questionnaires have shown impairments in HRQL in patients receiving HMV compared to normals. This was primarily attributed to severe limitations in physical health, but not in mental health indicating that if severe physical limitation occurs in advanced respiratory disease this will not necessarily lead to mental limitation. In addition, limitations in HRQL in patients with HMV were not substantially higher than in patients with different chronic disease being not dependent on HMV. Improvements in HRQL following the institution of HMV were only mild or even insignificant in patients with COPD, but patients with restrictive ventilatory disorders are suspected to have more benefits. However, well validated disease-specific questionnaires which are designed to be more sensitive in the assessment of changes in HRQL than generic instruments have been introduced recently for patients with severe respiratory failure, but the influence of HMV to HRQL remains still unclear, since prospective studies using these questionnaires have yet not been finished.