Expiratory and inspiratory action of transversus abdominis during eupnea and hypercapnic ventilation.

BACKGROUND: Recently, there is interest in the clinical importance of monitoring abdominal muscles during respiratory failure. The clinical interpretation relies on the assumption that expiration is a passive physiologic process and, since diaphragm and abdomen are arranged in series, any inward motion of the abdominal wall represents a sign of diaphragm dysfunction. However, previous studies suggest transversus abdominis might be active even during eupnea and is preferentially recruited over the other abdominal muscles. OBJECTIVE: 1) Is transversus abdominis normally recruited during eupnea? 2) What is the degree of activation of transversus abdominis during hypercapnia? 3) Does the end-inspiratory length of transversus abdominis change during hypercapnia, while diaphragm function is normal? METHODS: In 30 spontaneously breathing canines, awake without confounding anesthetic, we measured directly both electrical activity and corresponding mechanical length and shortening of transversus abdominis during eupnea and hypercapnia. RESULTS: Transversus abdominis is consistently recruited during eupnea. During hypercapnia, transversus abdominis recruitment is progressive and significant. Throughout hypercapnia, transversus abdominis baseline end-inspiratory length is not constant: baseline length decreases progressively throughout hypercapnia. After expiration, into early inspiration, transversus abdominis shows a consistent neural mechanical post -expiratory expiratory activity (PEEA) at rest, which progressively increases during hypercapnia. CONCLUSION: Transversus abdominis is an obligatory expiratory muscle, reinforcing the fundamental principle expiration is not a passive process. Beyond expiration, during hypercapnic ventilation, transversus abdominis contributes as an "accessory inspiratory muscle" into the early phase of inspiration. Clinical monitoring of abdominal wall motion during respiratory failure may be confounded by action of transversus abdominis.

Tele-ICU - a Canadian review.

Based on the learnings and experiences from implementations in the United States, telemedicine may offer certain advantages to help address some of the challenges faced by the Canadian critical care community resulting from staff shortages and increasing demands for quality care. The initial and operating costs of the technology and its impact on direct bedside care are perceived to be significant drivers of resistance to its wide spread implementation. This qualitative review of the available literature summarizes the opportunities and challenges with the potential use of telemedicine to enhance the delivery of critical care services in Canada.

Limitations of surface EMG estimate of parasternal intercostal to infer neural respiratory drive.

BACKGROUND: Recently, surface EMG of parasternal intercostal muscle has been incorporated in the "ERS Statement of Respiratory Muscle Testing" as a clinical technique to monitor the neural respiratory drive (NRD). However, the anatomy of the parasternal muscle risks confounding EMG "crosstalk" activity from neighboring muscles. OBJECTIVES: To determine if surface "parasternal" EMG: 1) reliably estimates parasternal intercostal EMG activity, 2) is a valid surrogate expressing neural respiratory drive (NRD). METHODS: Fine wire electrodes were implanted into parasternal intercostal muscle in 20 severe COPD patients along with a pair of surface EMG electrodes at the same intercostal level. We recorded both direct fine wire parasternal EMG (EMGPARA) and surface estimated "parasternal" EMG (SurfEMGpara) simultaneously during resting breathing, volitional inspiratory maneuvers, apnoea with extraneous movement of upper extremity, and hypercapnic ventilation. RESULTS: Surface estimated "parasternal" EMG showed spurious "pseudobreathing" activity without any airflow while real parasternal EMG was silent, during apnoea with body extremity movement. Surface estimated "parasternal" EMG did not faithfully represent real measured parasternal EMG. Surface estimated "parasternal" EMG was significantly less active than directly measured parasternal EMG during all conditions including baseline, inspiratory capacity and hypercapnic ventilation. Bland-Altman analysis showed consistent bias between direct parasternal EMG recording and surface estimated EMG during stimulated breathing. CONCLUSION: Surface "parasternal" EMG does not consistently or reliably express EMG activity of parasternal intercostal as recorded directly by implanted fine wires. A chest wall surface estimate of parasternal intercostal EMG may not faithfully express NRD and is of limited utility as a biomarker in clinical applications.

The accuracy of pulse oximetry in emergency department patients with severe sepsis and septic shock: a retrospective cohort study.

BACKGROUND: Pulse oximetry is routinely used to continuously and noninvasively monitor arterial oxygen saturation (SaO2) in critically ill patients. Although pulse oximeter oxygen saturation (SpO2) has been studied in several patient populations, including the critically ill, its accuracy has never been studied in emergency department (ED) patients with severe sepsis and septic shock. Sepsis results in characteristic microcirculatory derangements that could theoretically affect pulse oximeter accuracy. The purposes of the present study were twofold: 1) to determine the accuracy of pulse oximetry relative to SaO2 obtained from ABG in ED patients with severe sepsis and septic shock, and 2) to assess the impact of specific physiologic factors on this accuracy. METHODS: This analysis consisted of a retrospective cohort of 88 consecutive ED patients with severe sepsis who had a simultaneous arterial blood gas and an SpO2 value recorded. Adult ICU patients that were admitted from any Calgary Health Region adult ED with a pre-specified, sepsis-related admission diagnosis between October 1, 2005 and September 30, 2006, were identified. Accuracy (SpO2 - SaO2) was analyzed by the method of Bland and Altman. The effects of hypoxemia, acidosis, hyperlactatemia, anemia, and the use of vasoactive drugs on bias were determined. RESULTS: The cohort consisted of 88 subjects, with a mean age of 57 years (19 - 89). The mean difference (SpO2 - SaO2) was 2.75% and the standard deviation of the differences was 3.1%. Subgroup analysis demonstrated that hypoxemia (SaO2 < 90) significantly affected pulse oximeter accuracy. The mean difference was 4.9% in hypoxemic patients and 1.89% in non-hypoxemic patients (p < 0.004). In 50% (11/22) of cases in which SpO2 was in the 90-93% range the SaO2 was <90%. Though pulse oximeter accuracy was not affected by acidoisis, hyperlactatementa, anemia or vasoactive drugs, these factors worsened precision. CONCLUSIONS: Pulse oximetry overestimates ABG-determined SaO2 by a mean of 2.75% in emergency department patients with severe sepsis and septic shock. This overestimation is exacerbated by the presence of hypoxemia. When SaO2 needs to be determined with a high degree of accuracy arterial blood gases are recommended.

Distinct neural-mechanical efficiency of costal and crural diaphragm during hypercapnia.

Classic physiology suggests that the two distinct diaphragm segments, costal and crural, are functionally different. It is not known if the two diaphragm muscles share a common neural mechanical activation. We hypothesized that costal and crural diaphragm are recruited differently during hypercapnic stimulated ventilation, and the EMG recordings of the esophageal crural diaphragm segment does not translate to the same level of mechanical shortening for costal and crural segments In 30 spontaneously breathing canines, without confounding anesthetic, we measured directly electrical activity and corresponding mechanical shortening of both the costal and crural diaphragm, at room air and during increasing hypercapnia. During hypercapnic ventilation, the costal diaphragm showed a predominant recruitment over the crural diaphragm. The distinct mechanical contribution of the costal segment was not due to a different level of neural activation between the two muscles as measured by segmental EMG activity. Thus, the two diaphragm segments exhibited a significantly different neural-mechanical relationship.

Prevention of ventilator-associated pneumonia in the calgary health region: a Canadian success story!

This article describes the experiences of a Canadian multidisciplinary critical care team striving to reduce the incidence of ventilator-associated pneumonia (VAP). Several interventions, including a VAP bundle, were used and applied across a health region. Our regional VAP rate has seen a steady decline over the past 12 months and has been largely under our goal of 9.8 cases per 1,000 ventilator-days. The team's success in lowering VAP has provided the momentum for sustained improvement, which has spread to other areas.

Timing of onset of persistent critical illness: a multi-centre retrospective cohort study.

PURPOSE: Persistent critical illness has been described as a subtype of chronic critical illness, characterized as a transition after ICU admission where primary diagnosis and illness acuity are no better at predicting outcome than pre-hospital characteristics. Herein we describe the occurrence and outcomes associated with persistent critical illness in a large Canadian health region. METHODS: In this multi-center observational cohort study, all patients aged older than 14 years admitted to 12 ICUs in Alberta, Canada, between June 2012 and December 2014 were included. Primary outcome was in-hospital mortality. Predictors at ICU admission were separated into: (1) antecedent characteristics component (e.g., demographics, chronic health component of the APACHE II score, comorbid conditions); and (2) acute illness component (e.g., APACHE II score at admission, SOFA score, primary diagnostic category, surgical status, acute organ support). Using multiple statistical methods and randomly splitting the cohort into development and validation samples for risk scoring using logistic regression, we examined mortality prediction of each of these components to characterize the timing of transition to persistent critical illness. RESULTS: We included 17,783 patients with a median (IQR) age 61 years (49-71), 62% were male, and mean APACHE II score was 19.0 (7.9). In-hospital mortality was 16.8%. Among patients alive and in ICU, the acute illness component, which accurately predicted outcome at the time of admission [area under the receiver operating characteristics curve (AUC) 0.861; 95% CI 0.860-0.862], progressively lost predictive ability and was no longer more predictive than antecedent characteristics after 9 days. This transition defined the onset of persistent critical illness and comprised 16.1% (n = 2856) of the cohort. Transition ranged between 5 and 21 days across subgroups. In-hospital mortality was greater for those with persistent critical illness [23.9% vs. 15.5%, odds ratio (OR) 1.54; 95% CI 1.43-1.67, p < 0.001]. Persistently critically ill patients accounted for 54.5% of 97844 ICU bed-days and 36.3% of 420119 hospital bed-days, respectively. CONCLUSIONS: Persistent critical illness occurred in one in six patients admitted to Alberta ICUs and portended greater risk of death, prolonged ICU and hospital stay, and disproportionate use of health resources compared to patients without persistent critical illness.

Association between strained capacity and mortality among patients admitted to intensive care: A path-analysis modeling strategy.

PURPOSE: To evaluate the associations between strained ICU capacity and patient outcomes. METHODS: Multi-center population-based cohort study of nine integrated ICUs in Alberta, Canada. Path-analysis modeling was adopted to investigate direct and indirect associations between strain (available beds ≤1; occupancy ≥95%) and outcomes. Mixed-effects multivariate regression was used to measure the association between strain and acuity (APACHE II score), and both acuity and strain measures on ICU mortality and length of stay. RESULTS: 12,265 admissions comprise the study cohort. Available beds ≤1 and occupancy ≥95% occurred for 22.3% and 17.0% of admissions. Lower bed availability was associated with higher APACHE II score (p<0.0001). The direct effect of ≤1 available beds at ICU admission on ICU mortality was 11.6% (OR 1.116; 95% CI, 0.995-1.252). Integrating direct and indirect effects resulted in a 16.5% increased risk of ICU mortality (OR 1.165; 95% CI, 1.036-1.310), which exceeded the direct effect by 4.9%. Findings were similar with strain defined as occupancy ≥95%. Strain was associated with shorter ICU stay, primarily mediated by greater acuity. CONCLUSIONS: Strained capacity was associated with increased ICU mortality, partly mediated through greater illness acuity. Future work should consider both the direct and indirect relationships of strain on outcomes.

Telemedicine in the intensive care unit environment--a survey of the attitudes and perspectives of critical care clinicians.

PURPOSE: This study was conducted to assess the preimplementation knowledge and perceptions of intensive care unit (ICU) clinicians regarding the ability of telemedicine in the ICU environment (Tele-ICU) to address challenges resulting from the shortages of experienced critical care human resources and the drive to improve quality of care. METHODS: An online survey was administered to clinicians from a Canadian multisite critical care department. Qualitative and quantitative analyses were undertaken to identify key positive and negative themes. RESULTS: The overall self-rated knowledge about Tele-ICU was low, with significant uncertainty particularly related to the novelty of the technology, lack of widespread existing implementations, and insufficient education. A significant degree of skepticism was expressed regarding the ability of Tele-ICU to address the challenges of staff shortages and quality of care. CONCLUSIONS: Significant uncertainty and skepticism were expressed by critical care clinicians regarding the ability of Tele-ICU to address the challenges of human resource limitation and the delivery of quality care. This suggests the need for further research and education of system impact beyond patient outcomes related to this new technology.