A Prospective Analysis of Motor and Cognitive Skill Retention in Novice Learners of Point of Care Ultrasound.

OBJECTIVES: To identify the time at which point of care ultrasound static image recognition and image acquisition skills decay in novice learners. SETTING: The University of Iowa Hospitals and Clinics. SUBJECTS: Twenty-four subjects (23 first-year medical students and one first-year physician assistant student). DESIGN: The subjects completed an initial didactic and hands-on session with immediate testing of learned image acquisition and static image identification skills. INTERVENTIONS: Retesting occurred at 1, 4, and 8 weeks after the initial training session with no retraining in between. Image acquisition skills were obtained on the same healthy male volunteers, and the students were given no immediate feedback on their performance. The image identification skills were assessed with a 10 question test at each follow-up session. MEASUREMENTS AND MAIN RESULTS: For pleural ultrasound by 4 weeks, there was a significant decline of the ability to identify A-lines (p = 0.0065). For pleural image acquisition, there was no significant decline in the ability to demonstrate lung sliding. Conversely, cardiac image recognition did not significantly decline throughout the study, while the ability to demonstrate cardiac images at 4 weeks (parasternal short axis view) did (p = 0.0008). CONCLUSIONS: Motor and cognitive skills decay at different times for pleural and cardiac images. Future ultrasound curricula should retrain skills at a maximum of 8 weeks from initial training. They should focus more on didactic sessions related to image identification for pleural images, and more hands-on image acquisition training for cardiac images, which represents a novel finding.

Respiratory Therapist-Driven Mechanical Ventilation Protocol Is Associated With Increased Lung Protective Ventilation.

BACKGROUND: Mechanical ventilation is a common life-saving procedure but can lead to serious complications, including ARDS and oxygen toxicity. Nonadherence to lung-protective ventilation guidelines is common. We hypothesized that a respiratory therapist-driven mechanical ventilation bundle could increase adherence to lung-protective ventilation and decrease the incidence of pulmonary complications in the ICU. METHODS: A respiratory therapist-driven protocol was implemented on August 1, 2018, in all adult ICUs of a Midwestern academic tertiary center. The protocol targeted low tidal volume, adequate PEEP, limiting oxygen, adequate breathing frequency, and head of the bed elevation. Adherence to lung-protective guidelines and clinical outcomes were retrospectively observed in adult subjects admitted to the ICU and on ventilation for ≥ 24 h between January 2011 and December 2019. RESULTS: We included 666 subjects; 68.5% were in the pre-intervention group and 31.5% were in the post-intervention group. After adjusting for body mass index and intubation indication, a significant increase in overall adherence to lung-protective ventilation guidelines was observed in the post-intervention period (adjusted odds ratio 2.48, 95% CI 1.73-3.56). Fewer subjects were diagnosed with ARDS in the post-intervention group (adjusted odds ratio 0.22, 95% CI 0.08-0.65) than in the pre-intervention group. There was no difference in the incidence of ventilator-associated pneumonia, ventilator-free days, ICU mortality, or death within 1 month of ICU discharge. CONCLUSIONS: A respiratory therapist-driven protocol increased adherence to lung-protective mechanical ventilation guidelines in the ICU and was associated with decreased ARDS incidence.

Abundant DNase I-sensitive bacterial DNA in healthy porcine lungs and its implications for the lung microbiome.

Human lungs are constantly exposed to bacteria in the environment, yet the prevailing dogma is that healthy lungs are sterile. DNA sequencing-based studies of pulmonary bacterial diversity challenge this notion. However, DNA-based microbial analysis currently fails to distinguish between DNA from live bacteria and that from bacteria that have been killed by lung immune mechanisms, potentially causing overestimation of bacterial abundance and diversity. We investigated whether bacterial DNA recovered from lungs represents live or dead bacteria in bronchoalveolar lavage (BAL) fluid and lung samples in young healthy pigs. Live bacterial DNA was DNase I resistant and became DNase I sensitive upon human antimicrobial-mediated killing in vitro. We determined live and total bacterial DNA loads in porcine BAL fluid and lung tissue by comparing DNase I-treated versus untreated samples. In contrast to the case for BAL fluid, we were unable to culture bacteria from most lung homogenates. Surprisingly, total bacterial DNA was abundant in both BAL fluid and lung homogenates. In BAL fluid, 63% was DNase I sensitive. In 6 out of 11 lung homogenates, all bacterial DNA was DNase I sensitive, suggesting a predominance of dead bacteria; in the remaining homogenates, 94% was DNase I sensitive, and bacterial diversity determined by 16S rRNA gene sequencing was similar in DNase I-treated and untreated samples. Healthy pig lungs are mostly sterile yet contain abundant DNase I-sensitive DNA from inhaled and aspirated bacteria killed by pulmonary host defense mechanisms. This approach and conceptual framework will improve analysis of the lung microbiome in disease.

Capnography for Monitoring of the Critically Ill Patient.

Capnography has been widely adopted in multiple clinical areas. The capnogram and end-tidal carbon dioxide offer a wealth of information, in the right clinical setting, and when properly interpreted. In this article, the authors aim to review the most common clinical scenarios during which capnography has been shown to be of benefit. This includes the areas of fluid responsiveness, cardiopulmonary resuscitation, and conscious sedation. They review the published literature, highlighting its pitfalls and identifying its limitations.

Central venous-to-arterial PCO2 difference as a marker to identify fluid responsiveness in septic shock.

Defining the hemodynamic response to volume therapy is integral to managing critically ill patients with acute circulatory failure, especially in the absence of cardiac index (CI) measurement. This study aimed at investigating whether changes in central venous-to-arterial CO2 difference (Δ-ΔPCO2) and central venous oxygen saturation (ΔScvO2) induced by volume expansion (VE) are reliable parameters to define fluid responsiveness in sedated and mechanically ventilated septic patients. We prospectively studied 49 critically ill septic patients in whom VE was indicated because of circulatory failure and clinical indices. CI, ΔPCO2, ScvO2, and oxygen consumption (VO2) were measured before and after VE. Responders were defined as patients with a > 10% increase in CI (transpulmonary thermodilution) after VE. We calculated areas under the receiver operating characteristic curves (AUCs) for Δ-ΔPCO2, ΔScvO2, and changes in CI (ΔCI) after VE in the whole population and in the subgroup of patients with an increase in VO2 (ΔVO2) ≤ 10% after VE (oxygen-supply independency). Twenty-five patients were fluid responders. In the whole population, Δ-ΔPCO2 and ΔScvO2 were significantly correlated with ΔCI after VE (r = - 0.30, p = 0.03 and r = 0.42, p = 0.003, respectively). The AUCs for Δ-ΔPCO2 and ΔScvO2 to define fluid responsiveness (increase in CI > 10% after VE) were 0.76 (p < 0.001) and 0.68 (p = 0.02), respectively. In patients with ΔVO2 ≤ 10% (n = 36) after VE, the correlation between ΔScvO2 and ΔCI was 0.62 (p < 0.001), and between Δ-ΔPCO2 and ΔCI was - 0.47 (p = 0.004). The AUCs for Δ-ΔPCO2 and ΔScvO2 were 0.83 (p < 0.001) and 0.73 (p = 0.006), respectively. In these patients, Δ-ΔPCO2 ≤ -37.5% after VE allowed the categorization between responders and non-responders with a positive predictive value of 100% and a negative predictive value of 60%. In sedated and mechanically ventilated septic patients with no signs of tissue hypoxia (oxygen-supply independency), Δ-ΔPCO2 is a reliable parameter to define fluid responsiveness.

Usefulness of venous-to-arterial partial pressure of CO2 difference to assess oxygen supply to demand adequacy: effects of dobutamine.

The central venous O2 saturation value and lactic acid levels are part of the diagnostic and therapeutic work up of patients in shock. These usual indicators of tissue hypoxia don't fully describe the adequacy of tissue perfusion. There is ample evidence that supplementing this data with the venous-to-arterial partial pressure of CO2 (PCO2) difference (ΔPCO2) complements the clinician's tools when treating patients with shock. Based on a modified Fick equation as it applies to CO2, in patients in a steady state, the ΔPCO2 reflects the cardiac output (CO). This observation has been shown to be of clinical value in resuscitating patients in shock. Moreover, the ΔPCO2 can be used to titrate inotropes, and differentiate the hemodynamic from the metabolic effect of dobutamine.

Estimating Arterial Partial Pressure of Carbon Dioxide in Ventilated Patients: How Valid Are Surrogate Measures?

The arterial partial pressure of carbon dioxide (PaCO2) is an important parameter in critically ill, mechanically ventilated patients. To limit invasive procedures or for more continuous monitoring of PaCO2, clinicians often rely on venous blood gases, capnography, or transcutaneous monitoring. Each of these has advantages and limitations. Central venous Pco2 allows accurate estimation of PaCO2, differing from it by an amount described by the Fick principle. As long as cardiac output is relatively normal, central venous Pco2 exceeds the arterial value by approximately 4 mm Hg. In contrast, peripheral venous Pco2 is a poor predictor of PaCO2, and we do not recommend using peripheral venous Pco2 in this manner. Capnography offers measurement of the end-tidal Pco2 (PetCO2), a value that is close to PaCO2 when the lung is healthy. It has the advantage of being noninvasive and continuously available. In mechanically ventilated patients with lung disease, however, PetCO2 often differs from PaCO2, sometimes by a large degree, often seriously underestimating the arterial value. Dependence of PetCO2 on alveolar dead space and ventilator expiratory time limits its value to predict PaCO2. When lung function or ventilator settings change, PetCO2 and PaCO2 can vary in different directions, producing further uncertainty. Transcutaneous Pco2 measurement has become practical and reliable. It is promising for judging steady state values for PaCO2 unless there is overt vasoconstriction of the skin. Moreover, it can be useful in conditions where capnography fails (high-frequency ventilation) or where arterial blood gas analysis is burdensome (clinic or home management of mechanical ventilation).

Improving CPR Performance.

Cardiac arrest continues to represent a public health burden with most patients having dismal outcomes. CPR is a complex set of interventions requiring leadership, coordination, and best practices. Despite the widespread adoption of new evidence in various guidelines, the provision of CPR remains variable with poor adherence to published recommendations. Key steps health-care systems can take to enhance the quality of CPR and, potentially, to improve outcomes, include optimizing chest compressions, avoiding hyperventilation, encouraging intraosseous access, and monitoring capnography. Feedback devices provide instantaneous guidance to the rescuer, improve rescuer technique, and could impact patient outcomes. New technologies promise to improve the resuscitation process: mechanical devices standardize chest compressions, capnography guides resuscitation efforts and signals the return of spontaneous circulation, and intraosseous devices minimize interruptions to gain vascular access. This review aims at identifying a discreet group of interventions that health-care systems can use to raise their standard of cardiac resuscitation.

Using electronic medical record notes to measure ICU telemedicine utilization.

Given the complexity of high-acuity health care, designing an effective clinical note template can be beneficial to both document patient care and clarify how telemedicine is used. We characterized documented interactions via a standardized note template between bedside intensive care unit (ICU) providers and teleintensivists in 2 Veterans Health Administration ICU telemedicine support centers. All ICUs linked to support centers and providing care from October 2012 through September 2014 were considered. Interactions were assessed based on initiation site, bedside initiator, contact type, and patient care change. Of 14 511 ICU admissions with teleintensivist access, teleintensivist interaction was documented in 21.6% (N = 3136). In particular, contacts were primarily initiated by bedside staff (74.4%), use increased over time, and of contacts resulting in changes in patient care, most were initiated by a bedside nurse (84.3%). Given this variation, future research necessitates inclusion of utilization in evaluation of Tele-ICU and patient outcomes.

Capnography During Critical Illness.

Capnography has made steady inroads in the ICU and is increasingly used for all patients who are mechanically ventilated. There is growing recognition that capnography is rich in information about lung and circulatory physiology and provides insight into many diseases and treatments. These include conditions of impaired matching of ventilation and perfusion, such as pulmonary embolism and obstructive lung diseases; circulatory questions, such as the adequacy of chest compressions during cardiac arrest or fluid responsiveness in patients in shock; and the safety of procedural sedation. In this review, we emphasize analysis of the entire capnographic waveform as a way to glean additional useful information. We also discuss important limitations of capnography, especially when it is considered to be a surrogate for Paco2.

Impact of an intensive care unit telemedicine program on patient outcomes in an integrated health care system.

IMPORTANCE: Intensive care unit (ICU) telemedicine (TM) programs have been promoted as improving access to intensive care specialists and ultimately improving patient outcomes, but data on effectiveness are limited and conflicting. OBJECTIVE: To examine the impact of ICU TM on mortality rates and length of stay (LOS) in an integrated health care system. DESIGN, SETTING, AND PARTICIPANTS: Observational pre-post study of patients treated in 8 "intervention" ICUs (7 hospitals within the US Department of Veterans Affairs health care system) during 2011-2012 that implemented TM monitoring during the post-TM period as well as patients treated in concurrent control ICUs that did not implement an ICU TM program. INTERVENTION: Implementation of ICU TM monitoring. MAIN OUTCOMES AND MEASURES: Unadjusted and risk-adjusted ICU, in-hospital, and 30-day mortality rates and ICU and hospital LOS for patients who did or did not receive treatment in ICUs equipped with TM monitoring. RESULTS: Our study included 3355 patients treated in our intervention ICUs (1708 in the pre-TM period and 1647 in the post-TM period) and 3584 treated in the control ICUs during the same period. Patient demographics and comorbid illnesses were similar in the intervention and control ICUs during the pre-TM and post-TM periods; however, predicted ICU mortality rates were modestly lower for admissions to the intervention ICUs compared with control ICUs in both the pre-TM (3.0% vs 3.6%; P = .02) and post-TM (2.8% vs 3.5%; P < .001) periods. Implementation of ICU TM was not associated with a significant decline in ICU, in-hospital, or 30-day mortality rates or LOS in unadjusted or adjusted analyses. For example, unadjusted ICU mortality in the pre-TM vs post-TM periods were 2.9% vs 2.8% (P = .89) for the intervention ICUs and 4.0% vs 3.4% (P = .31) for the control ICUs. Unadjusted 30-day mortality during the pre-TM vs post-TM periods were 7.7% vs 7.8% (P = .91) for the intervention ICUs and 12.0% vs 10.2% (P = .08) for the control ICUs. Evaluation of interaction terms comparing the magnitude of mortality rate change during the pre-TM and post-TM periods in the intervention and control ICUs failed to demonstrate a significant reduction in mortality rates or LOS. CONCLUSIONS AND RELEVANCE: We found no evidence that the implementation of ICU TM significantly reduced mortality rates or LOS.

Trendelenburg position does not increase cross-sectional area of the internal jugular vein predictably.

BACKGROUND: The Trendelenburg position is used to distend the central veins, improving both the success and safety of vascular cannulation. The purpose of this study was to measure the cross-sectional area (CSA) of the internal jugular vein (IJV) in three different positions using surface ultrasonography. METHODS: Fifty-one subjects were enrolled. A Sono Site Titan 180 or M-Turbo portable ultrasound machine with a 10.5-mHz broadband linear surface probe was used. We measured the CSA of the IJV (at end-expiration at the level of the cricoid cartilage) in three positions: 15° reverse Trendelenburg, supine, and 15° Trendelenburg. RESULTS: The mean CSA at 15° reverse Trendelenburg was 0.83 cm2 (SD, 0.86), in the supine position it was 1.25 cm2 (SD, 0.98), and at -15° Trendelenburg it was 1.47 cm2 (SD, 1.03). Moving from reverse Trendelenburg to supine, the CSA increased by 50%. In contrast, lowering the head to a Trendelenburg position increased the mean CSA by only 17%. Surprisingly, Trendelenburg positioning reduced the CSA in nine of the 51 subjects. CONCLUSIONS: Trendelenburg positioning augments the CSA only modestly, on average, compared with the supine position, and in some patients it reduces the CSA. TRIAL REGISTRATION: ClinicalTrials.gov; No.: NCT01099254; URL: www.clinicaltrials.gov.

The flow-time waveform predicts respiratory system resistance and compliance.

PURPOSE: Knowledge of patients' lung compliance and resistance aids clinical management. We investigated whether these values, readily measured during volume assist-control ventilation (VACV), could also be estimated during pressure assist-control ventilation (PACV). METHODS: Data were collected in 12 mechanically ventilated human subjects. During VACV, peak pressure, plateau pressure, end-expiratory pressure, tidal volume, and inspiratory flow rate were measured. During PACV, inspiratory pressure, end-expiratory pressure, and tidal volume were recorded. The linear component of the pressure-time waveform was extrapolated to time and flow axes. Using the equation of motion for the respiratory system, assuming a nonlinear resistance, we calculated inspiratory resistance and compliance. During VACV, compliance and inspiratory resistance were calculated in the conventional manner. RESULTS: In ventilated subjects, mean compliance during PACV was 37.06 ± 15.65 mL/cm H(2)O, and during VACV, 36.93 ± 12.18 mL/cm H(2)O. Mean inspiratory resistance during PACV was 15.17 ± 5.14 cm H(2)O/L per second, whereas during VACV, it was 12.50 ± 2.99 cm H(2)O/L per second. A strong correlation is evident between compliance and inspiratory resistance calculated during PACV vs VACV (r(2) of 0.73 and 0.51, respectively). CONCLUSIONS: During PACV, the inspiratory flow waveform is linear, and its slope contains information regarding inspiratory resistance and compliance. Calculated values correlate with those during VACV.