Daniel Chipman

Early Mobilization in Critically Ill Patients: Patients' Mobilization Level Depends on Health Care Provider's Profession

To evaluate whether the level of mobilization achieved and the barriers for progressing to the next mobilization level differ between nurses and physical therapists.

Bilevel vs ICU Ventilators Providing Noninvasive Ventilation: Effect of System Leaks: A COPD Lung Model Comparison

BACKGROUND Noninvasive positive-pressure ventilation (NPPV) modes are currently available on bilevel and ICU ventilators. However, little data comparing the performance of the NPPV modes on these ventilators are available. METHODS In an experimental bench study, the ability of nine ICU ventilators to function in the presence of leaks was compared with a bilevel ventilator using the IngMar ASL5000 lung simulator (IngMar Medical; Pittsburgh, PA) set at a compliance of 60 mL/cm H(2)O, an inspiratory resistance of 10 cm H(2)O/L/s, an expiratory resistance of 20 cm H(2)O/ L/s, and a respiratory rate of 15 breaths/min. All of the ventilators were set at 12 cm H(2)O pressure support and 5 cm H(2)O positive end-expiratory pressure. The data were collected at baseline and at three customized leaks. MAIN RESULTS At baseline, all of the ventilators were able to deliver adequate tidal volumes, to maintain airway pressure, and to synchronize with the simulator, without missed efforts or auto-triggering. As the leak was increased, all of the ventilators (except the Vision [Respironics; Murrysville, PA] and Servo I [Maquet; Solna, Sweden]) needed adjustment of sensitivity or cycling criteria to maintain adequate ventilation, and some transitioned to backup ventilation. Significant differences in triggering and cycling were observed between the Servo I and the Vision ventilators. CONCLUSIONS The Vision and Servo I were the only ventilators that required no adjustments as they adapted to increasing leaks. There were differences in performance between these two ventilators, although the clinical significance of these differences is unclear. Clinicians should be aware that in the presence of leaks, most ICU ventilators require adjustments to maintain an adequate tidal volume.

Global Muscle Strength But Not Grip Strength Predicts Mortality and Length of Stay in a General Population in a Surgical Intensive Care Unit

Background Paresis acquired in the intensive care unit (ICU) is common in patients who are critically ill and independently predicts mortality and morbidity. Manual muscle testing (MMT) and handgrip dynamometry assessments have been used to evaluate muscle weakness in patients in a medical ICU, but similar data for patients in a surgical ICU (SICU) are limited. Objective The purpose of this study was to evaluate the predictive value of strength measured by MMT and handgrip dynamometry at ICU admission for in-hospital mortality, SICU length of stay (LOS), hospital LOS, and duration of mechanical ventilation. Design This investigation was a prospective, observational study. Methods One hundred ten patients were screened for eligibility for testing in the SICU of a large, academic medical center. The Acute Physiology and Chronic Health Evaluation (APACHE) II score, diagnoses, and laboratory data were collected. Measurements were obtained by MMT quantified with the sum (total) score on the Medical Research Council Scale and by handgrip dynamometry. Outcome data, including in-hospital mortality, SICU LOS, hospital LOS, and duration of mechanical ventilation, were collected for all participants. Results One hundred seven participants were eligible for testing; 89% were tested successfully at a median of 3 days (25th–75th percentiles=3–6 days) after admission. Sedation was the most frequent barrier to testing (70.6%). Manual muscle testing was identified as an independent predictor of mortality, SICU LOS, hospital LOS, and duration of mechanical ventilation. Grip strength was not independently associated with these outcomes. Limitations This study did not address whether muscle weakness translates to functional outcome impairment. Conclusions In contrast to handgrip strength, MMT reliably predicted in-hospital mortality, duration of mechanical ventilation, SICU LOS, and hospital LOS.

Autologous Transfusion of Stored Red Blood Cells Increases Pulmonary Artery Pressure

RATIONALE Transfusion of erythrocytes stored for prolonged periods is associated with increased mortality. Erythrocytes undergo hemolysis during storage and after transfusion. Plasma hemoglobin scavenges endogenous nitric oxide leading to systemic and pulmonary vasoconstriction. OBJECTIVES We hypothesized that transfusion of autologous blood stored for 40 days would increase the pulmonary artery pressure in volunteers with endothelial dysfunction (impaired endothelial production of nitric oxide). We also tested whether breathing nitric oxide before and during transfusion could prevent the increase of pulmonary artery pressure. METHODS Fourteen obese adults with endothelial dysfunction were enrolled in a randomized crossover study of transfusing autologous, leukoreduced blood stored for either 3 or 40 days. Volunteers were transfused with 3-day blood, 40-day blood, and 40-day blood while breathing 80 ppm nitric oxide. MEASUREMENTS AND MAIN RESULTS The age of volunteers was 41 ± 4 years (mean ± SEM), and their body mass index was 33.4 ± 1.3 kg/m(2). Plasma hemoglobin concentrations increased after transfusion with 40-day and 40-day plus nitric oxide blood but not after transfusing 3-day blood. Mean pulmonary artery pressure, estimated by transthoracic echocardiography, increased after transfusing 40-day blood (18 ± 2 to 23 ± 2 mm Hg; P < 0.05) but did not change after transfusing 3-day blood (17 ± 2 to 18 ± 2 mm Hg; P = 0.5). Breathing nitric oxide decreased pulmonary artery pressure in volunteers transfused with 40-day blood (17 ± 2 to 12 ± 1 mm Hg; P < 0.05). CONCLUSIONS Transfusion of autologous leukoreduced blood stored for 40 days was associated with increased plasma hemoglobin levels and increased pulmonary artery pressure. Breathing nitric oxide prevents the increase of pulmonary artery pressure produced by transfusing stored blood. Clinical trial registered with www.clinicaltrials.gov (NCT 01529502).

Recruitment Maneuvers and Positive End-Expiratory Pressure Titration in Morbidly Obese ICU Patients.

Objective:The approach to applying positive end-expiratory pressure in morbidly obese patients is not well defined. These patients frequently require prolonged mechanical ventilation, increasing the risk for failed liberation from ventilatory support. We hypothesized that lung recruitment maneuvers and titration of positive end-expiratory pressure were both necessary to improve lung volumes and the elastic properties of the lungs, leading to improved gas exchange. Design:Prospective, crossover, nonrandomized interventional study. Setting:Medical and surgical ICUs at Massachusetts General Hospital. Patients:Critically ill, mechanically ventilated morbidly obese (body mass index > 35 kg/m2) patients (n = 14). Interventions:This study evaluated two methods of titrating positive end-expiratory pressure; both trials were done utilizing positive end-expiratory pressure titration and recruitment maneuvers while measuring hemodynamics and respiratory mechanics. Measurements were obtained at the baseline positive end-expiratory pressure set by the clinicians, at zero positive end-expiratory pressure, at best positive end-expiratory pressure identified through esophageal pressure measurement before and after a recruitment maneuver, and at best positive end-expiratory pressure identified through a best decremental positive end-expiratory pressure trial. Measurements and Main Results:The average body mass index was 50.7 ± 16.0 kg/m2. The two methods of evaluating positive end-expiratory pressure identified similar optimal positive end-expiratory pressure levels (20.7 ± 4.0 vs 21.3 ± 3.8 cm H2O; p = 0.40). End-expiratory pressure titration increased end-expiratory lung volumes (&Dgr;11 ± 7 mL/kg; p < 0.01) and oxygenation (&Dgr;86 ± 50 torr; p < 0.01) and decreased lung elastance (&Dgr;5 ± 5 cm H2O/L; p < 0.01). Recruitment maneuvers followed by titrated positive end-expiratory pressure were effective at increasing end-expiratory lung volumes while decreasing end-inspiratory transpulmonary pressure, suggesting an improved distribution of lung aeration and reduction of overdistension. The positive end-expiratory pressure levels set by the clinicians (11.6 ± 2.9 cm H2O) were associated with lower lung volumes, worse elastic properties of the lung, and lower oxygenation. Conclusions:Commonly used positive end-expiratory pressure by clinicians is inadequate for optimal mechanical ventilation of morbidly obese patients. A recruitment maneuver followed by end-expiratory pressure titration was found to significantly improve lung volumes, respiratory system elastance, and oxygenation.

Telemedicine Versus Face-to-Face Evaluations by Respiratory Therapists of Mechanically Ventilated Neonates and Children: A Pilot Study.

BACKGROUND: Mechanical ventilation is one of the most important therapeutic interventions in neonatal and pediatric ICUs. Telemedicine has been shown to reliably extend pediatric intensivist expertise to facilities where expertise is limited. If reliable, telemedicine may extend the reach of pediatric respiratory therapists (RTs) to facilities where expertise does not exist or free up existing RT resources for important face-to-face activities in facilities where expertise is limited. The aim of this study was to determine how well respiratory assessments for ventilated neonates and children correlated when performed simultaneously by 2 RTs face-to-face and via telemedicine. METHODS: We conducted a pilot study including 40 assessments by 16 RTs on 11 subjects (5 neonatal ICU; 6 pediatric ICU). Anonymously completed intake forms by 2 different RTs concurrently assessing 14 ventilator-derived and patient-based respiratory variables were used to determine correlations. RESULTS: Forty paired assessments were performed. Median telemedicine assessment time was 8 min. The Pearson correlation coefficient (r) was used to determine agreement between continuous data, and the Cohen kappa statistics were used for binary variables. Pressure control, PEEP, breathing frequency, and FIO2 perfectly correlated (r = 1, all P < .001) as did the presence of a CO2 monitor and need for increased ventilatory support (kappa = 1). The Pearson correlation coefficient for VT, minute ventilation, mean airway pressure, and oxygen saturation ranged from 0.84 to 0.97 (all P < .001). kappa = 0.41 (95% CI 0.02–0.80) for patient-triggered breaths, and kappa = 0.57 (95% CI 0.19–0.94) for breathing frequency higher than set frequency. kappa = −0.25 (95% CI −0.46 to −0.04) for need for suctioning. CONCLUSIONS: Telemedicine technology was acceptable to RTs. Telemedicine evaluations highly correlated with face-to-face for 10 of 14 aspects of standard bedside respiratory assessment. Poor correlation was noted for more complex, patient-generated parameters, highlighting the importance of further investigation incorporating a virtual stethoscope.

Advances in Ventilatory Support of Critically Ill Children

Advances in pediatric medical practices often lag behind the progress made in adult patients, primarily because of the limited number of randomized, controlled, clinical trials. Recent advances in mechanical ventilation derived from successful application in adults include neurally adjusted ventilatory assist, noninvasive ventilation, and protective lung strategies. NAVA improves patient/ventilator synchrony and reduces the work of breathing, which allows for a decreased use of sedation. This should decrease the length of time patients are intubated and mechanically ventilated. The use of noninvasive ventilation eliminates the need for endotracheal tubes and complications associated with them including tracheal injury, pressure ulcers, issues with oral hygiene and ventilator associated pneumonia. Application of lung protective strategies to pediatric patients with acute lung injury and/or ARDS results in increased oxygenation, less lung injury, and improvements in morbidity and mortality.

Reply to Fontana et al.

We would like to thank Dr. Fontana et al. [1] for their letter addressing our recent publication on the performance of adult ICU ventilators providing neonatal ventilation [2]. They raise two important issues regarding our data that we will address here: (1) trigger pressure and trigger delay, and (2) the variability of our data. In order to address the issue of trigger delay and trigger pressure, it is important to first understand the difference between our model lung, the IngMar ASL 5000 and the Michigan Instruments 5601i-Adult/Infant PNEUVIEW. As stated by Dr. Fontana et al. [1], they measured changes in airway pressure and flow at the ‘‘wye’’ piece of the ventilator circuit proximal to the lung model’s compliance and resistance. As has been done with other Michigan Instruments lung model studies, the onset of inspiration for measurement purposes occurred when either pressure deflected below baseline or a change in flow was measured at the circuit ‘‘wye’’ [3, 4]. However, before this change occurred at the wye, the lung model needed to be decompressed and the resistance and compliance overcome for pressure and flow to change at the wye. Thus, time was spent and pressure was dissipated before a change was ever measurable at the circuit wye. In the IngMar, the pressure to trigger and the time to trigger were measured inside the lung model itself. As a result, the compliance and resistance of the lung model had to be overcome before pressure and flow could change at the circuit wye. Hence the longer time to trigger and greater trigger pressure than that observed by Fontana et al. in the same ventilator [1]. We believe our measurements [2] reflect more closely the pressure and time to trigger experienced by a neonate triggering the ventilator evaluated. As noted in the supplement to our article, the P0.1 of our model was even higher than that set by Fontana et al. [1] (-4 and -7 cm H2O vs -2 cm H2O). Thus, one would expect the time to trigger to be shorter in our study and the pressure to trigger to be greater. The pressure to trigger was greater but the time to trigger was longer because of measurement inside the lung model versus at the circuit wye. The variability depicted in Figs. 2– 5 of our paper results from a number of factors [2]. First of all, 24 separate conditions were evaluated for each ventilator studied. These included three different settings of compliance/ resistance, two different muscle efforts, two different ventilator settings, and each of the above with and without a system leak. We agree with Dr. Fontana that, during a single evaluation, the variability among a series of breathes on a lung model are extremely small, but if you collapse findings under a number of different circumstances variability increases greatly, which is what we present. For example, Fig. 2 depicts the effects of the three compliance/resistance settings, but this represents the average data from two different muscle efforts and two ventilator settings all with and without a system leak! Thus the high variability noted in this figure. Finally, the level of variability among ventilators was considerable; some varied greatly over the 24 test conditions while others did not!