Brian K Walsh

Humidification During Invasive and Noninvasive Mechanical Ventilation: 2012

We searched the MEDLINE, CINAHL, and Cochrane Library databases for articles published between January 1990 and December 2011. The update of this clinical practice guideline is based on 184 clinical trials and systematic reviews, and 10 articles investigating humidification during invasive and noninvasive mechanical ventilation. The following recommendations are made following the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) scoring system: 1. Humidification is recommended on every patient receiving invasive mechanical ventilation. 2. Active humidification is suggested for noninvasive mechanical ventilation, as it may improve adherence and comfort. 3. When providing active humidification to patients who are invasively ventilated, it is suggested that the device provide a humidity level between 33 mg H2O/L and 44 mg H2O/L and gas temperature between 34°C and 41°C at the circuit Y-piece, with a relative humidity of 100%. 4. When providing passive humidification to patients undergoing invasive mechanical ventilation, it is suggested that the HME provide a minimum of 30 mg H2O/L. 5. Passive humidification is not recommended for noninvasive mechanical ventilation. 6. When providing humidification to patients with low tidal volumes, such as when lung-protective ventilation strategies are used, HMEs are not recommended because they contribute additional dead space, which can increase the ventilation requirement and PaCO2. 7. It is suggested that HMEs are not used as a prevention strategy for ventilator-associated pneumonia.

Responding to Compliance Changes in a Lung Model During Manual Ventilation: Perhaps Volume, Rather Than Pressure, Should be Displayed

Objective. The standard technique for positive-pressure ventilation is to regulate the breath size by varying the pressure applied to the bag. Investigators have argued that consistency of peak inspiratory pressure is important. However, research shows that excessive tidal volume delivered with excessive pressure injures preterm lungs, which suggests that inspiratory pressure should be varied during times of changing compliance, such as resuscitation of newborns or treatment after surfactant delivery. Methods. We modified a computerized lung model (ASL5000 [IngMar Medical, Pittsburgh, PA]) to simulate the functional residual capacity of a 3-kg neonate with apnea and programmed it to change compliance during ventilation. Forty-five professionals were blinded to randomized compliance changes while using a flow-inflating bag, a self-inflating bag, and a T-piece resuscitator. We instructed subjects to maintain a constant inflation volume, first while blinded to delivered volume and then with volume displayed, with all 3 devices. Results. Subjects adapted to compliance changes by adjusting inflation pressure more effectively when delivered volume was displayed. When only pressure was displayed, sensing of compliance changes occurred only with the self-inflating bag. When volume was displayed, adjustments to compliance changes occurred with all 3 devices, although the self-inflating bag was superior. Conclusions. In this lung model, volume display permitted far better detection of compliance changes compared with display of only pressure. Devices for administration of positive-pressure ventilation should display volume rather than pressure.

Oxygen Gas–Filled Microparticles Provide Intravenous Oxygen Delivery

A foam suspension containing oxygen gas–filled microparticles can deliver life-sustaining oxygen during a 15-min period of complete asphyxia. Oxygen on Demand The clinical sequelae after prolonged oxygen deprivation can be serious, including cardiac arrest and brain damage. In these situations, patients are typically fed oxygen through a tube via the mouth. What happens when access to the lungs is impeded or delayed? Currently, few other options exist. In response, Kheir and colleagues have engineered microparticles that can be injected into the veins for systemic delivery of oxygen to all of the vital organs. The lipidic oxygen–containing microparticles (LOMs) consist of a lipid shell and an oxygen gas (O2) core, with an approximate diameter of 4 μm. These tiny particles were designed to mix with venous blood and deliver O2 to oxygen-deprived hemoglobin—the molecule that carries oxygen to all tissues within the body. Kheir et al. first confirmed that the LOMs functioned as intended by mixing a foam suspension of the particles with human blood in tubes and measuring the rise in oxygenated hemoglobin. When administered intravenously to asphyxiated (and therefore hypoxemic) rabbits, the LOMs were able to maintain full-body oxygenation, normal blood pressure, and normal heart rate compared to control animals that only received a saline solution. The animals receiving LOMs also lived longer and did not experience any injury to major organs, such as liver and lungs. This is an encouraging demonstration for critical care medicine situations, showing that animals can survive and remain healthy even after 10 to 15 min of complete asphyxia. Such short-term infusions could therefore serve an important therapeutic function for critically ill patients, but before you hear “LOMs, stat!” in the emergency room, additional studies will be needed to assess simultaneous removal of carbon dioxide buildup, LOM metabolism, and possible side effects from longer-term, continuous infusions. We have developed an injectable foam suspension containing self-assembling, lipid-based microparticles encapsulating a core of pure oxygen gas for intravenous injection. Prototype suspensions were manufactured to contain between 50 and 90 ml of oxygen gas per deciliter of suspension. Particle size was polydisperse, with a mean particle diameter between 2 and 4 μm. When mixed with human blood ex vivo, oxygen transfer from 70 volume % microparticles was complete within 4 s. When the microparticles were infused by intravenous injection into hypoxemic rabbits, arterial saturations increased within seconds to near-normal levels; this was followed by a decrease in oxygen tensions after stopping the infusions. The particles were also infused into rabbits undergoing 15 min of complete tracheal occlusion. Oxygen microparticles significantly decreased the degree of hypoxemia in these rabbits, and the incidence of cardiac arrest and organ injury was reduced compared to controls. The ability to administer oxygen and other gases directly to the bloodstream may represent a technique for short-term rescue of profoundly hypoxemic patients, to selectively augment oxygen delivery to at-risk organs, or for novel diagnostic techniques. Furthermore, the ability to titrate gas infusions rapidly may minimize oxygen-related toxicity.

Capnography/Capnometry During Mechanical Ventilation: 2011

We searched the MEDLINE, CINAHL, and Cochrane Library databases for articles published between January 1990 and November 2010. The update of this clinical practice guideline is based on 234 clinical studies and systematic reviews, 19 review articles that investigated capnography/capnometry during mechanical ventilation, and the 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. The following recommendations are made following the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) scoring system: (1) Continuous-waveform capnography is recommended, in addition to clinical assessment to confirm and monitor correct placement of an endotracheal tube. (2) If waveform capnography is not available, a non-waveform exhaled CO2 monitor, in addition to clinical assessment, is suggested as the initial method for confirming correct tube placement in a patient in cardiac arrest. (3) End-tidal CO2 (PETCO2) is suggested to guide ventilator management. (4) Continuous capnometry during transport of the mechanically ventilated patients is suggested. (5) Capnography is suggested to identify abnormalities of exhaled air flow. (6) Volumetric capnography is suggested to assess CO2 elimination and the ratio of dead-space volume to tidal volume (VD/VT) to optimize mechanical ventilation. (7) Quantitative waveform capnography is suggested in intubated patients to monitor cardiopulmonary quality, optimize chest compressions, and detect return of spontaneous circulation during chest compressions or when rhythm check reveals an organized rhythm.

Inpatient Bronchiolitis Guideline Implementation and Resource Utilization

BACKGROUND: Provider-dependent practice variation in children hospitalized with bronchiolitis is not uncommon. Clinical practice guidelines (CPGs) can streamline practice and reduce utilization however, CPG implementation is complex. METHODS: A multidisciplinary team developed and implemented CPGs for management of bronchiolitis for children <2 years old. Children with comorbidities, ICU admissions, and outside hospital transfers were excluded. Implementation involved teamwork and collaboration, provider education, online access to CPGs, order sets, data sharing, and monthly team meetings. Resource utilization was defined as use of chest x-rays (CXRs), antibiotics, steroids, and more than 2 doses of inhaled bronchodilator use. Outcome metrics included length of stay (LOS) and readmission rate. Bronchiolitis season was defined as September to April. Data were collected for 2 seasons post implementation. RESULTS: The number CPG-eligible patients in the pre- and 2 postimplementation periods were similar (1244, preimplementation; 1159, postimplementation season 1; 1283 postimplementation season 2). CXRs decreased from 59.7% to 45.1% (P < .0001) in season 1 to 39% (P < .0001) in season 2. Bronchodilator use decreased from 27% to 20% (P < .01) in season 1 to 14% (P < .002) in season 2. Steroid use significantly reduced from 19% to 11% (P < .01). Antibiotic use did not change significantly (P = .16). LOS decreased from 2.3 to 1.8 days (P < .0001) in season 1 and 1.9 days (P < .05) in season 2. All-cause 7-day readmission rate did not change (P = .45). CONCLUSIONS: Bronchiolitis CPG implementation resulted in reduced use of CXRs, bronchodilators, steroids, and LOS without affecting 7-day all-cause readmissions.

AARC Clinical Practice Guideline: Blood Gas Analysis and Hemoximetry: 2013

We searched MEDLINE, CINAHL, and Cochrane Library database for articles published between January 1990 and December 2012. The update of this clinical practice guideline is based on 237 clinical trials, 54 reviews, and 23 meta-analyses on blood gas analysis (BGA) and hemoximetry. The following recommendations are made following the Grading of Recommendations Assessment, Development, and Evaluation scoring system. BGA and hemoximetry are recommended for evaluating a patients ventilatory, acid-base, and/or oxygenation status. BGA and hemoximetry are suggested for evaluating a patients response to therapeutic interventions. BGA and hemoximetry are recommended for monitoring severity and progression of documented cardiopulmonary disease processes. Hemoximetry is recommended to determine the impact of dyshemoglobins on oxygenation. Capillary BGA is not recommended to determine oxygenation status. Central venous BGA and hemoximetry are suggested to determine oxygen consumption in the setting of early goal-directed therapies. For the assessment of oxygenation, a peripheral venous PO2 is not recommended as a substitute for an arterial blood measurement (PaO2). It is not recommended to use venous PCO2 and pH as a substitute for arterial blood measurement of PaCO2 and pH. It is suggested that hemoximetry is used in the detection and evaluation of shunts during diagnostic cardiac catheterization.

Pediatric Airway Maintenance and Clearance in the Acute Care Setting: How To Stay Out of Trouble

Traditional airway maintenance and clearance therapy and principles of application are similar for neonates, children, and adults. Yet there are distinct differences in physiology and pathology between children and adults that limit the routine application of adult-derived airway-clearance techniques in children. This paper focuses on airway-clearance techniques and airway maintenance in the pediatric patient with acute respiratory disease, specifically, those used in the hospital environment, prevailing lung characteristics that may arise during exacerbations, and the differences in physiologic processes unique to infants and children. One of the staples of respiratory care has been chest physiotherapy and postural drainage. Many new airway clearance and maintenance techniques have evolved, but few have demonstrated true efficacy in the pediatric patient population. Much of this is probably due to the limited ability to assess outcome and/or choose a proper disease-specific or age-specific modality. Airway-clearance techniques consume a substantial amount of time and equipment. Available disease-specific evidence of airway-clearance techniques and airway maintenance will be discussed whenever possible. Unfortunately, more questions than answers remain.

Reversal of dependent lung collapse predicts response to lung recruitment in children with early acute lung injury.

Objective: To describe the resolution of regional atelectasis and the development of regional lung overdistension during a lung-recruitment protocol in children with acute lung injury. Design: Prospective interventional trial. Setting: Pediatric intensive care unit. Patients: Ten children with early (<72 hrs) acute lung injury. Interventions: Sustained inflation maneuver (positive airway pressure of 40 cm H2O for 40 secs), followed by a stepwise recruitment maneuver (escalating plateau pressures by 5 cm H2O every 15 mins) until physiologic lung recruitment, defined by PaO2 + PaCO2 ≥400 mm Hg, was achieved. Regional lung volumes and mechanics were measured using electrical impedance tomography. Measurements and Main Results: Patients that responded to the stepwise lung-recruitment maneuver had atelectasis in 54% of the dependent lung regions, while nonresponders had atelectasis in 10% of the dependent lung regions (p = .032). In the pressure step preceding physiologic lung recruitment, a significant reversal of atelectasis occurred in 17% of the dependent lung regions (p = .016). Stepwise recruitment overdistended 8% of the dependent lung regions in responders, but 58% of the same regions in nonresponders (p < .001). Lung compliance in dependent lung regions increased in responders, while compliance in nonresponders did not improve. In contrast to the stepwise recruitment maneuver, the sustained inflation did not produce significant changes in atelectasis or oxygenation: atelectasis was only reversed in 12% of the lung (p = .122), and there was only a modest improvement in oxygenation (27 ± 14 mm Hg, p = .088). Conclusions: Reversal of atelectasis in the most dependent lung region preceded improvements in gas exchange during a stepwise lung-recruitment strategy. Lung recruitment of dependent lung areas was accompanied by considerable overdistension of nondependent lung regions. Larger amounts of atelectasis in dependent lung areas were associated with a positive response to a stepwise lung-recruitment maneuver.

Electrical activity of the diaphragm during extubation readiness testing in critically ill children

Objectives: To investigate the electrical activity of the diaphragm during extubation readiness testing. Design: Prospective observational trial. Setting: A 29-bed medical-surgical pediatric intensive care unit. Patients: Mechanically ventilated children between 1 month and 18 yrs of age. Interventions: Twenty patients underwent a standardized extubation readiness test using a minimal pressure support ventilation strategy. A size-appropriate multiple-array esophageal electrode (electrical diaphragmatic activity catheter), which doubled as a feeding tube, was inserted. The electrical diaphragmatic activity, ventilatory parameters, and spirometry measurements were recorded with the Servo-i ventilator (Maquet, Solna, Sweden). Measurements were obtained before the extubation readiness test and 1 hr into the extubation readiness test. Measurements and Main Results: During extubation readiness testing, the ratio of tidal volume to delta electrical diaphragmatic activity was significantly lower in those patients who passed the extubation readiness test compared to those who failed the extubation readiness test (extubation readiness test, pass: 24.8 ± 20.9 mL/&mgr;V vs. extubation readiness test, fail: 67.2 ± 27 mL/&mgr;V, respectively; p = .02). Delta electrical diaphragmatic activity correlated significantly with neuromuscular drive assessed by airway opening pressure at 0.1 secs (before extubation readiness test: r = .591, p < .001; during extubation readiness test: r = .682, p < .001). Eight out of 20 patients had ventilator dys-synchrony identified with electrical diaphragmatic activity during extubation readiness testing. Conclusions: Patients who generate higher diaphragmatic activity in relation to tidal volume may have better preserved diaphragmatic function and a better chance of passing the extubation readiness test as opposed to patients who generate lower diaphragmatic activity in relation to tidal volume, indicating diaphragmatic weakness. Electrical activity of the diaphragm also may be a useful adjunct to assess neuromuscular drive in ventilated children.

Factors associated with survival in pediatric extracorporeal membrane oxygenation—a single-center experience

AIM We aimed to examine outcomes of extracorporeal membrane oxygenation (ECMO) therapy in the pediatric population and identify pre-ECMO and on-ECMO characteristics that are associated with survival. METHODS We retrospectively reviewed the ECMO records at our institution between 1999 and 2008 and selected pediatric patients who were cannulated for respiratory failure or hemodynamic instability resistant to conventional interventions. We recorded details of pre-ECMO clinical characteristics, including blood gas variables and mechanical ventilatory support, and details of ECMO therapy including survival off ECMO and to hospital discharge. Predictors of survival were analyzed using logistic regression modeling and a prediction algorithm was developed. RESULTS Of the 445 ECMO runs, data from 58 consecutive patients were analyzed: 57% were successfully decannulated, and 48% survived to discharge from the hospital. The cohort included 32 (55%) female patients, 22 postoperative patients (38%), and 15 (26%) with an immunosuppressive condition, with a median age of 5 years and weight 19.5 kg, The mean duration of pre-ECMO respiratory support was 3 days, in the form of high-frequency oscillatory ventilation (n = 28, 48%) and conventional mechanical ventilation (n = 13, 22%). The median duration (interquartile range) of ECMO support was 142 hours (60, 321) or 5.9 days. Pre-ECMO pH above 7.2 (P < .001) and oxygenation index below 35 (P = .021) were associated with the highest survival rates. Pre-ECMO PaCO(2) and duration of mechanical ventilation were not associated with survival. CONCLUSIONS Based on our results, ECMO therapy should be considered early in children with oxygenation index greater than 35 with worsening metabolic status. The restriction of ECMO based on ventilator days alone needs to be revisited in this era of lung protective ventilation.