Jeff Charbeneau

Excessive tidal volume from breath stacking during lung-protective ventilation for acute lung injury

Rationale:Low tidal volume ventilation strategies for patients with respiratory failure from acute lung injury may lead to breath stacking and higher volumes than intended. Objective:To determine frequency, risk factors, and volume of stacked breaths during low tidal volume ventilation for acute lung injury. Design, Setting, and Patients:Prospective cohort study of mechanically ventilated patients with acute lung injury (enrolled from August 2006 through May 2007) treated with low tidal volume ventilation in a medical intensive care unit at an academic tertiary care hospital. Interventions:Patients were ventilated with low tidal volumes using the Acute Respiratory Distress Syndrome Network protocol for acute lung injury. Continuous flow-time and pressure-time waveforms were recorded. The frequency, risk factors, and volume of stacked breaths were determined. Sedation depth was monitored using Richmond agitation sedation scale. Measurements and Main Results:Twenty patients were enrolled and studied for a mean 3.3 ± 1.7 days. The median (interquartile range) Richmond agitation sedation scale was −4 (−5, −3). Inter-rater agreement for identifying stacked breaths was high (kappa 0.99, 95% confidence interval 0.98–0.99). Stacked breaths occurred at a mean 2.3 ± 3.5 per minute and resulted in median volumes of 10.1 (8.8–10.7) mL/kg predicted body weight, which was 1.62 (1.44–1.82) times the set tidal volume. Stacked breaths were significantly less common with higher set tidal volumes (relative risk 0.4 for 1 mL/kg predicted body weight increase in tidal volume, 95% confidence interval 0.23–0.90). Conclusion:Stacked breaths occur frequently in low tidal volume ventilation despite deep sedation and result in volumes substantially above the set tidal volume. Set tidal volume has a strong influence on frequency of stacked breaths.

Comparison of Sirolimus with Azathioprine in a Tacrolimus-based Immunosuppressive Regimen in Lung Transplantation

RATIONALE Lung transplantation has evolved into a life-saving therapy for select patients with end-stage lung diseases. However, long-term survival remains limited because of chronic rejection. Sirolimus is beneficial in preventing cardiac rejection and may decrease rejection after lung transplantation. OBJECTIVES To determine the potential benefit versus risk of sirolimus in lung transplantation. METHODS We conducted a multicenter randomized, open label controlled trial comparing sirolimus (SIR) with azathioprine (AZA) in a tacrolimus-based immunosuppressive regimen in lung transplantation. The primary end point was the incidence of acute rejection at 1 year after transplantation between the two study groups. MEASUREMENTS AND MAIN RESULTS One hundred eighty-one patients were randomized to be included in this study. At 1 year after transplantation, there was no significant difference in the incidence of grade A acute rejection between the two study groups. Similarly, the incidence of chronic rejection and graft survival was no different between the two study groups. Cytomegalovirus infection was decreased in the SIR arm compared with the AZA arm (relative risk, 0.67 [95% confidence interval, 0.55, 0.82]; P < 0.01). There was a higher rate of adverse events leading to early discontinuation of SIR (64%) compared with AZA (49%) during the course of this study. CONCLUSIONS Sirolimus, an mTOR inhibitor, did not decrease the incidence of acute rejection at 1 year compared with azathioprine in lung transplantation. These results differ from previous results in cardiac and renal transplantation and emphasize the need for multicenter randomized controlled trials in lung transplantation. Clinical trial registered with www.clinicaltrials.gov (NCT 00321906).

Increased risk of venous thromboembolism with a sirolimus-based immunosuppression regimen in lung transplantation

BACKGROUND Sirolimus (rapamycin) is a potent anti-proliferative agent with immunosuppressive properties that is increasingly being used in solid-organ and hematopoietic stem cell transplantation. In addition, this drug is being investigated for treatment of a broad range of disorders, including cardiovascular disease, malignancies, tuberous sclerosis, and lymphangeioleiomyomatosis. In this study, we found an increased risk of venous thromboembolism (VTE) in lung transplant recipients treated with a sirolimus (SIR)-based immunosuppressive regimen. METHODS One hundred eighty-one lung transplant recipients were enrolled in a prospective, multicenter, randomized, open-label trial comparing a tacrolimus (TAC)/SIR/prednisone immunosuppression regimen with a TAC/azathioprine (AZA)/prednisone immunosuppressive regimen. The differences in rates of VTE were examined. RESULTS There was a significantly higher occurrence of VTE in the SIR cohort [15 of 87 (17.2%)] compared with the AZA cohort [3 of 94 (3.2%)] (stratified log-rank statistic = 7.44, p < 0.01). When adjusted for pre-transplant diagnosis and stratified by transplant center, this difference remained essentially unchanged (hazard ratio for SIR vs AZA = 5.2, 95% confidence interval 1.4 to 19.5, p = 0.01). CONCLUSION Clinicians prescribing SIR should maintain a high level of vigilance for VTE, particularly among patients with other risk factors for this complication.

Decreased incidence of cytomegalovirus infection with sirolimus in a post hoc randomized, multicenter study in lung transplantation

BACKGROUND Cytomegalovirus (CMV) is the most common opportunistic infection in lung transplantation. A recent multicenter, randomized trial (the AIRSAC study) comparing sirolimus to azathioprine in lung transplant recipients showed a decreased incidence of CMV events in the sirolimus cohort. To better characterize this relationship of decreased incidence of CMV events with sirolimus, we examined known risk factors and characteristics of CMV events from the AIRSAC database. METHODS The AIRSAC database included 181 lung transplant patients from 8 U.S.-based lung transplant centers that were randomized to sirolimus or azathioprine at 3 months post-transplantation. CMV incidence, prophylaxis, diagnosis and treatment data were all prospectively collected. Prophylaxis and treatment of CMV were at the discretion of each institution. RESULTS The overall incidence of any CMV event was decreased in the sirolimus arm when compared with the azathioprine arm at 1 year after lung transplantation (relative risk [RR] = 0.67, confidence interval [CI] 0.55 to 0.82, p < 0.01). This decreased incidence of CMV events with sirolimus remained significant after adjusting for confounding factors of CMV serostatus and CMV prophylaxis. CONCLUSIONS These data support results from other solid-organ transplantation studies and suggest further investigation of this agent in the treatment of lung transplant recipients at high risk for CMV events.

Patient-Related Factors Associated With Hospital Discharge to a Care Facility After Critical Illness

BACKGROUND Many critically ill patients are transferred to other care facilities instead of to home at hospital discharge. OBJECTIVE To identify patient-related factors associated with hospital discharge to a care facility after critical illness and to estimate the magnitude of risk associated with each factor. METHODS Retrospective cohort study of 548 survivors of critical illness in a medical intensive care unit. Multivariable logistic regression was used to identify independent risk factors for discharge to a care facility. Only the first 72 hours of intensive care were analyzed. RESULTS Approximately one-quarter of the survivors of critical illness were discharged to a care facility instead of to home. This event occurred more commonly in older patients, even after adjustment for severity of illness and comorbid conditions (odds ratio [OR] 1.8 for patients ≥ 65 years of age vs patients < 65 years; 95% confidence interval [CI], 1.1-3.1; P = .02). The risk was greatest for patients who received mechanical ventilation (OR, 3.4; 95% CI, 2.0-5.8; P < .001) or had hospitalizations characterized by severe cognitive dysfunction (OR, 8.1; 95% CI, 1.3-50.6; P = .02) or poor strength and/or mobility (OR, 31.7; 95% CI, 6.4-157.3; P < .001). The model showed good discrimination (area under the curve, 0.82; 95% CI, 0.77-0.86). CONCLUSION The model, which did not include baseline function or social variables, provided good discrimination between patients discharged to a care facility after critical illness and patients discharged to home. These results suggest that future research should focus on the debilitating effects of respiratory failure and on conditions with cognitive and neuromuscular sequelae.

High frequency chest wall oscillation for asthma and chronic obstructive pulmonary disease exacerbations: a randomized sham-controlled clinical trial

BackgroundHigh frequency chest wall oscillation (HFCWO) is used for airway mucus clearance. The objective of this study was to evaluate the use of HFCWO early in the treatment of adults hospitalized for acute asthma or chronic obstructive pulmonary disease (COPD).MethodsRandomized, multi-center, double-masked phase II clinical trial of active or sham treatment initiated within 24 hours of hospital admission for acute asthma or COPD at four academic medical centers. Patients received active or sham treatment for 15 minutes three times a day for four treatments. Medical management was standardized across groups. The primary outcomes were patient adherence to therapy after four treatments (minutes used/60 minutes prescribed) and satisfaction. Secondary outcomes included change in Borg dyspnea score (≥ 1 unit indicates a clinically significant change), spontaneously expectorated sputum volume, and forced expired volume in 1 second.ResultsFifty-two participants were randomized to active (n = 25) or sham (n = 27) treatment. Patient adherence was similarly high in both groups (91% vs. 93%; p = 0.70). Patient satisfaction was also similarly high in both groups. After four treatments, a higher proportion of patients in the active treatment group had a clinically significant improvement in dyspnea (70.8% vs. 42.3%, p = 0.04). There were no significant differences in other secondary outcomes.ConclusionsHFCWO is well tolerated in adults hospitalized for acute asthma or COPD and significantly improves dyspnea. The high levels of patient satisfaction in both treatment groups justify the need for sham controls when evaluating the use of HFCWO on patient-reported outcomes. Additional studies are needed to more fully evaluate the role of HFCWO in improving in-hospital and post-discharge outcomes in this population.Trial RegistrationClinicalTrials.gov: NCT00181285