Protocols for lung protective ventilation

Tidal volume significantly affects oxygenation in healthy pigs during high-frequency oscillatory ventilation compared to conventional ventilation

Background

The role of high-frequency oscillatory ventilation (HFOV) has long been debated. Numerous studies documented its benefits, whereas several more recent studies did not prove superiority of HFOV over protective conventional mechanical ventilation (CV). One of the accepted explanations is that CV and HFOV act differently, including gas exchange.

Methods

To investigate a different level of coupling or decoupling between oxygenation and carbon dioxide elimination during CV and HFOV, we conducted a prospective crossover animal study in 11 healthy pigs. In each animal, we found a normocapnic tidal volume (VT) after the lung recruitment maneuver. Then, VT was repeatedly changed over a wide range while keeping constant the levels of PEEP during CV and mean airway pressure during HFOV. Arterial partial pressures of oxygen (PaO2) and carbon dioxide (PaCO2) were recorded. The same procedure was repeated for CV and HFOV in random order.

Results

Changes in PaCO2 intentionally induced by adjustment of VT affected oxygenation more significantly during HFOV than during CV. Increasing VT above its normocapnic value during HFOV caused a significant improvement in oxygenation, whereas improvement in oxygenation during CV hyperventilation was limited. Any decrease in VT during HFOV caused a rapid worsening of oxygenation compared to CV.

Conclusion

A change in PaCO2 induced by the manipulation of tidal volume inevitably brings with it a change in oxygenation, while this effect on oxygenation is significantly greater in HFOV compared to CV.

Ventilator Liberation in the Pediatric ICU

Despite the accepted importance of minimizing time on mechanical ventilation, only limited guidance on weaning and extubation is available from the pediatric literature. A significant proportion of patients being evaluated for weaning are actually ready for extubation, suggesting that weaning is often not considered early enough in the course of ventilation. Indications for extubation are often not clear, although a trial of spontaneous breathing on CPAP without pressure support seems an appropriate prerequisite in many cases. Several indexes have been developed to predict weaning and extubation success, but the available literature suggests they offer little or no improvement over clinical judgment. New techniques for assessing readiness for weaning and predicting extubation success are being developed but are far from general acceptance in pediatric practice. While there have been some excellent physiologic, observational, and even randomized controlled trials on aspects of pediatric ventilator liberation, robust research data are lacking. Given the lack of data in many areas, a determined approach that combines systematic review with consensus opinion of international experts could generate high-quality recommendations and terminology definitions to guide clinical practice and highlight important areas for future research in weaning, extubation readiness, and liberation from mechanical ventilation following pediatric respiratory failure.

Physiological Basis of Neonatal Aerodigestive Difficulties in Chronic Lung Disease

In the United States, preterm birth rates have steadily increased since 2014. Despite the recent advances in neonatal-perinatal care, more than 40% of very low-birth-weight infants develop chronic lung disease (CLD) and almost 25% have feeding difficulties resulting in delayed achievement of full oral feeds and longer hospital stay. Establishment of full oral feeds, a major challenge for preterm infants, becomes magnified among those on respiratory support and/or with CLD. The strategies to minimize aerodigestive disorders include supporting nonnutritive sucking, developing infant-directed feeding protocols, sensory oromotor stimulation, and early introduction of oral feeds.

Low tidal volume ventilation use remains low in patients with acute respiratory distress syndrome at a single center

PURPOSE

Low tidal volume ventilation (LTVV) reduces mortality in acute respiratory distress syndrome (ARDS) patients. Understanding local barriers to LTVV use at a former ARDS Network hospital may provide new insight to improve LTVV implementation.

METHODS

A cohort of 214 randomly selected adults met the Berlin definition of ARDS at Harborview Medical Center between 2008 and 2012. The primary outcome was the receipt of LTVV (tidal volume of ≤6.5mL/kg predicted body weight) within 48h of ARDS onset. We constructed a multivariable logistic regression model to identify factors associated with the outcome.

RESULTS

Only 27% of patients received tidal volumes of ≤6.5mL/kg PBW within 48h of ARDS onset. Increasing plateau pressure (OR 1.11; 95% CI 1.03 to 1.19; p-value<0.01) was positively associated with LTVV use while increasing PaO₂:F_IO₂ ratio was negatively associated (OR 0.75; 95% CI 0.57 to 0.98; p-value 0.03). Physicians documented an ARDS diagnosis in only 21% of the cohort. Neither patient height nor gender was associated with LTVV use.

CONCLUSIONS

Most ARDS patients did not receive LTVV despite implementation of a protocol. ARDS was also recognized in a minority of patients, suggesting an opportunity for improvement of care.

MECHANICAL VENTILATION FOR THE LUNG TRANSPLANT RECIPIENT

Mechanical ventilation (MV) is an important aspect in the intraoperative and early postoperative management of lung transplant (LTx)-recipients. There are no randomized-controlled trials of LTx-recipient MV strategies; however there are LTx center experiences and international survey studies reported. The main early complication of LTx is primary graft dysfunction (PGD), which is similar to the adult respiratory distress syndrome (ARDS). We aim to summarize information pertinent to LTx-MV, as well as PGD, ARDS, and intraoperative MV and to synthesize these available data into recommendations. Based on the available evidence, we recommend lung-protective MV with low-tidal-volumes (≤6 mL/kg predicted body weight [PBW]) and positive end-expiratory pressure for the LTx-recipient. In our opinion, the MV strategy should be based on donor characteristics (donor PBW as a parameter of actual allograft size), rather than based on recipient characteristics; however this donor-characteristics-based protective MV is based on indirect evidence and requires validation in prospective clinical studies.

Clinical pathways for chronic cough in children

BACKGROUND

Chronic cough (a cough lasting longer than four weeks) is a common problem internationally. Chronic cough has associated economic costs and is distressing to the child and to parents; ignoring cough may lead to delayed diagnosis and progression of serious underlying respiratory disease. Clinical guidelines have been shown to lead to efficient and effective patient care and can facilitate clinical decision making. Cough guidelines have been designed to facilitate the management of chronic cough. However, treatment recommendations vary, and specific clinical pathways for the treatment of chronic cough in children are important, as causes of and treatments for cough vary significantly from those in adults. Therefore, systematic evaluation of the use of evidence-based clinical pathways for the management of chronic cough in children would be beneficial for clinical practice and for patient care. Use of a management algorithm can improve clinical outcomes; such management guidelines can be found in the guidelines for cough provided by the American College of Chest Physicians (ACCP) and the British Thoracic Society (BTS).

OBJECTIVES

To evaluate the effectiveness of using a clinical pathway in the management of children with chronic cough.

SEARCH METHODS

The Cochrane Register of Controlled Trials (CENTRAL), the Cochrane Airways Group Specialised Register, MEDLINE, EMBASE, review articles and reference lists of relevant articles were searched. The latest search was conducted in January 2014.

SELECTION CRITERIA

All randomised controlled trials of parallel-group design comparing use versus non-use of a clinical pathway for treatment of chronic cough in children (< 18 years of age).

DATA COLLECTION AND ANALYSIS

Results of searches were reviewed against predetermined criteria for inclusion. Two review authors independently selected studies and performed data extraction in duplicate.

MAIN RESULTS

One study was included in the review. This multi-centre trial was based in five Australian hospitals and recruited 272 children with chronic cough. Children were randomly assigned to early (two weeks) or delayed (six weeks) referral to respiratory specialists who used a cough management pathway. When an intention-to-treat analysis was performed, clinical failure at six weeks post randomisation (defined as < 75% improvement in cough score, or total resolution for fewer than three consecutive days) was significantly less in the early pathway arm compared with the control arm (odds ratio (OR) 0.35, 95% confidence interval (CI) 0.21 to 0.58). These results indicate that one additional child will be cured for every five children treated via the cough pathway (number needed to treat for an additional beneficial outcome (NNTB) = 5, 95% CI 3 to 9) at six weeks. Cough-specific parent-reported quality of life scores were significantly better in the early-pathway group; the mean difference (MD) between groups was 0.60 (95% CI 0.19 to 1.01). Duration of cough post randomisation was significantly shorter in the intervention group (early-pathway arm) compared with the control group (delayed-pathway arm) (MD -2.70 weeks, 95% CI -4.26 to -1.14).

AUTHORS' CONCLUSIONS

Current evidence suggests that using a clinical algorithm for the management of children with chronic cough in hospital outpatient settings is more effective than providing wait-list care. Futher high-quality randomised controlled trials are needed to perform ongoing evaluation of cough management pathways in general practitioner and other primary care settings.

High-frequency oscillatory ventilation in children with acute respiratory distress syndrome: experience of a pediatric intensive care unit

OBJECTIVE

To describe the effects of high-frequency oscillatory ventilation (HFOV) as a rescue ventilatory support in pediatric patients with acute respiratory distress syndrome (ARDS).

METHODS

Twenty-five children (1 month < age < 17 years) admitted to a university hospital pediatric intensive care unit (ICU) with ARDS and submitted to HFOV for a minimum of 48 hours after failure of conventional mechanical ventilation were assessed.

RESULTS

Twenty eight days after the onset of ARDS, the mortality rate was 52% (13/25). Over the course of 48 hours, the use of HFOV reduced the oxygenation index [38 (31-50) vs. 17 (10-27)] and increased the ratio of partial arterial pressure O2 and fraction of inspired O2 [65 [44-80) vs. 152 (106-213)]. Arterial CO2 partial pressure [54 (45-74) vs. 48 (39-58) mmHg] remained unchanged. The mean airway pressure ranged between 23 and 29 cmH2O. HFOV did not compromise hemodynamics, and a reduction in heart rate was observed (141±32 vs. 119±22 beats/min), whereas mean arterial pressure (66±20 vs. 71±17 mmHg) and inotropic score [44 (17-130) vs. 20 (16-75)] remained stable during this period. No survivors were dependent on oxygen.

CONCLUSION

HFOV improves oxygenation in pediatric patients with ARDS and severe hypoxemia refractory to conventional ventilatory support.

Frequency of adoption of practice management guidelines at trauma centers

Evidence-based management guidelines have been shown to improve patient outcomes, yet their utilization by trauma centers remains unknown. This study measured adoption of practice management guidelines or protocols by trauma centers. A survey of 228 trauma centers was conducted over 1 year; 55 completed the survey. Centers were classified into three groups: noncompliant, partially compliant, and compliant with adoption of management protocols. Characteristics of compliant centers were compared with those of the other two groups. Most centers were Level I (58%) not-for-profit (67%) teaching hospitals (84%) with a surgical residency (74%). One-third of centers had an accredited fellowship in surgical critical care (37%). Only one center was compliant with all 32 management protocols. Half of the centers were compliant with 14 of 32 protocols studied (range, 4 to 32). Of the 21 trauma center characteristics studied, only two were independently associated with compliant centers: use of physician extenders and daily attending rounds (both P < .0001). Adoption of management guidelines by trauma centers is inconsistent, with wide variations in practices across centers.

Effectiveness of short-term 6-hour high-volume hemofiltration during refractory severe septic shock

BACKGROUND

The effectiveness of a single 6-hour session of high-volume hemofiltration (HVHF) was evaluated in terms of decreased norepinephrine (NE) requirements, progressive refractory hypotension and hypoperfusion by the fourth hour, and observed versus expected hospital mortality in patients with refractory severe septic shock.

METHODS

A prospective cohort study conducted at the intensive care unit with 31 patients suffering from severe septic shock (NE dose ≥ 0.3 μg kg min to maintain mean arterial pressure 70-80 mm Hg and lactic acidosis) and refractory to treatments recommended by Surviving Sepsis Campaign, 2008. All patients were subjected to a single short-term 6-hour HVHF with a goal-directed protocol. Changes in NE dose, hemodynamic, metabolic, and respiratory parameters were measured at the onset (t0), 4 (t4) and 6 hours (t6) during HVHF. Patients were considered responders if by t4 of HVHF, they showed a decrease in NE dose ≥ 50%, maintaining mean arterial pressure 80 mm Hg to 70 mm Hg.

RESULTS

: Twenty-five of the 31 patients responded to HVHF treatment (responders), whereas 6 did not (nonresponders). In the responders group, a decrease in NE dose was observed by t4 (1.3 ± 0.5 μg kg min). This beneficial effect was maintained by t6 of treatment. Hemodynamic, metabolic, and respiratory parameters and other organic function indicators were also significantly improved by t4 and maintained by t6. Hospital mortality (45.16%) was significantly lower than that predicted by Sequential Organ Failure Assessment score (>90%): 83% for nonresponders versus 36% for responders.

CONCLUSIONS

We conclude that a single session of short-term 6-hour HVHF in patients with refractory severe septic shock reduces NE dose requirements and improves organic function already by the fourth hour of treatment.

LEVEL OF EVIDENCE

III, therapeutic study.

Protocols in the management of critical illness

Care of the critically ill patient is becoming increasingly complex. Protocols, which standardize care of patients with similar diseases, represent a potential solution to managing multiple simultaneous problems in critically ill patients. In this article, we examine the advantages and disadvantages to care protocolization, and posit that careful and thoughtful implementation of protocols is likely to benefit patients. We also discuss the potential for unintended consequences, and even harm, with protocolization in critically ill patients using the Critical Illness Outcomes Study as a model to examine the effects of protocolization in large populations of intensive care patients.

High mortality from respiratory failure secondary to swine-origin influenza A (H1N1) in South Africa

BACKGROUND

The novel influenza A (H1N1) pandemic affected South Africa late during the 2009 Southern hemisphere winter and placed an extra burden on a health care system already dealing with a high prevalence of chronic lung diseases and human immunodeficiency virus (HIV) infection.

AIM

The aim of this study was to describe the epidemiological characteristics, clinical features, management and outcomes of patients with confirmed influenza A (H1N1) infection complicated by respiratory failure.

METHODS

We included all adult patients with confirmed influenza A (H1N1) infection that were referred to the medical intensive care unit of a large academic hospital in Cape Town for ventilatory support in this prospective observational study.

RESULTS

A total of 19 patients (39.5 +/- 14.8 years) needed ventilatory support over a 6-week period. Of these, 15 were female and 16 had identifiable risk factors for severe disease, including pregnancy (n = 6), type 2 diabetes mellitus (n = 6), obesity (n = 4), HIV infection (n = 3), immunosuppressive therapy (n = 3) and active pulmonary tuberculosis (n = 2). The most frequent complications were acute renal failure (n = 13), acute respiratory distress syndrome (n = 12) and ventilator associated pneumonia (n = 10). Thirteen patients died (mortality: 68.4%). Fatal cases were significantly associated with an APACHE II score >or=20 (P = 0.034), but not with a P(a)O(2)/F(I)O(2) <200 (P = 0.085) and a chest radiograph score >or=12 (P = 0.134).

CONCLUSION

The majority of patients with respiratory failure secondary to influenza A (H1N1) infection were young females and had an underlying risk factor for severe disease. The condition had a high mortality, particularly amongst patients with an APACHE II score >or=20.

The importance of fluid management in acute lung injury secondary to septic shock

BACKGROUND

Recent studies have suggested that early goal-directed resuscitation of patients with septic shock and conservative fluid management of patients with acute lung injury (ALI) can improve outcomes. Because these may be seen as potentially conflicting practices, we set out to determine the influence of fluid management on the outcomes of patients with septic shock complicated by ALI.

METHODS

A retrospective analysis was performed at Barnes-Jewish Hospital (St. Louis, MO) and in the medical ICU of Mayo Medical Center (Rochester, MN). Patients hospitalized with septic shock were enrolled into the study if they met the American-European Consensus definition of ALI within 72 h of septic shock onset. Adequate initial fluid resuscitation (AIFR) was defined as the administration of an initial fluid bolus of >or= 20 mL/kg prior to and achievement of a central venous pressure of >or= 8 mm Hg within 6 h after the onset of therapy with vasopressors. Conservative late fluid management (CLFM) was defined as even-to-negative fluid balance measured on at least 2 consecutive days during the first 7 days after septic shock onset.

RESULTS

The study cohort was made up of 212 patients with ALI complicating septic shock. Hospital mortality was statistically lowest for those achieving both AIFR and CLFM and higher for those achieving only CLFM, those achieving only AIFR, and those achieving neither (17 of 93 patients [18.3%] vs 13 of 31 patients [41.9%] vs 30 of 53 patients [56.6%] vs 27 of 35 [77.1%], respectively; p < 0.001).

CONCLUSIONS

Both early and late fluid management of septic shock complicated by ALI can influence patient outcomes.

Weaning and extubation readiness in pediatric patients

OBJECTIVE

A systematic review of weaning and extubation for pediatric patients on mechanical ventilation.

DATA SELECTION

Pediatric and adult literature, English language.

STUDY SELECTION

Invited review.

DATA SOURCES

Literature review using National Library of Medicine PubMed from January 1972 until April 2008, earlier cross-referenced article citations, the Cochrane Database of Systematic Reviews, and the Internet.

CONCLUSIONS

Despite the importance of minimizing time on mechanical ventilation, only limited guidance on weaning and extubation is available from the pediatric literature. A significant proportion of patients being evaluated for weaning are actually ready for extubation, suggesting that weaning is often not considered early enough in the course of ventilation. Indications for extubation are even less clear, although a trial of spontaneous breathing would seem a prerequisite. Several indices have been developed in an attempt to predict weaning and extubation success but the available literature would suggest they offer no improvement over clinical judgment. Extubation failure rates range from 2% to 20% and bear little relationship to the duration of mechanical ventilation. Upper airway obstruction is the single most common cause of extubation failure. A reliable method of assessing readiness for weaning and predicting extubation success is not evident from the pediatric literature.

Total and regional lung volume changes during high-frequency oscillatory ventilation (HFOV) of the normal lung

The effect of high-frequency oscillatory ventilation (HFOV) settings on the distribution of lung volume (V(L)) with changes in mean airway pressure (Paw), frequency (f(R)) and tidal volume (V(T)) remains controversial. We used computer tomographic (CT) imaging to quantify the distribution of V(L) during HFOV compared to static continuous positive airway pressure (CPAP). In anesthetized, supine canines, CT imaging of the entire lung was performed during CPAP and HFOV at Paw of 5, 12.5 and 20 cm H(2)O, f(R)=5, 10, 15 Hz. We found small, statistically significant decreases compared with CPAP in total and regional V(L) during HFOV that were greatest at lower f(R) and Paw. Apex and base sub-volumes underwent changes comparable to the lung overall. Increases in f(R) were accompanied by increases in Pa(O)(2). These finding provide additional insight into the impact of HFOV settings on the distribution of V(L) and suggest that there is low risk of occult regional over-distention during HFOV in normal lungs.

Clinical pathways for chronic cough in children

BACKGROUND

Chronic cough (a cough lasting longer than 4 weeks) is a common symptom presenting to primary care in Australia and internationally. Chronic cough costs the community, is distressing to parents, and ignoring cough may lead to delayed diagnosis and illness progression of serious underlying respiratory disease. Clinical guidelines have been shown to provide more efficient and effective patient care and can clarify clinical decision making. Cough guidelines have been designed to facilitate management of chronic cough, however treatment recommendations vary and specific clinical pathways for the treatment of chronic cough in children are important, as the cause and treatments for cough in a child vary significantly adults. Therefore, it would be beneficial to clinical practice to systematically evaluate the use of clinical pathways for the treatment of chronic cough in children.

OBJECTIVES

To evaluate the effectiveness of using a clinical pathway in the management of children with chronic cough.

SEARCH STRATEGY

The Cochrane Register of controlled Trials (CENTRAL), the Cochrane Airways Group Specialised Register, MEDLINE, EMBASE, review articles and reference lists of relevant articles were searched. The search was carried out in May 2007.

SELECTION CRITERIA

All randomised controlled trials with parallel group design comparing use vs non-use of a clinical pathway for treatment of chronic cough in children.

DATA COLLECTION AND ANALYSIS

Results of searches were reviewed against the pre-determined criteria for inclusion. Two reviewers independently selected the studies and it was planned that data extraction would have been done in duplicate.

MAIN RESULTS

The search identified 471 potentially relevant titles but no studies met criteria for inclusion in the review.

AUTHORS' CONCLUSIONS

Without further available evidence, recommendations for the use of clinical pathways for the treatment of chronic cough in children cannot be made. Until further evidence is available, the decision for further investigation and treatment for the child presenting with chronic cough should be made on an individual basis (i.e. dependent on symptoms and signs) with consideration for existing data from other Cochrane reviews on specific treatments for cough. Trials are required to provide evidence on the effectiveness of clinical pathways for the treatment of chronic cough in children.

Lung-protective ventilation strategies in neonatology: What do we know—What do we need to know?

OBJECTIVE

Randomized controlled trials (RCTs) investigating various lung-protective ventilation modes or strategies in newborn infants have failed to show clear differences in mortality or bronchopulmonary dysplasia. This review tries to identify possible reasons for this observation, applying modern concepts on ventilator-induced lung injury and lung-protective ventilation.

DATA SOURCE

Published RCTs and systematic reviews on mechanical ventilation in newborn infants were identified by searching PubMed and the Cochrane Library.

DATA SYNTHESIS

A total of 16 RCTs and four systematic reviews comparing high-frequency ventilation with conventional mechanical ventilation (CMV) failed to show consistent differences in mortality and bronchopulmonary dysplasia. Unfortunately, clear information or data on ventilation and oxygenation targets in the search for optimal lung volumes during high-frequency ventilation or CMV is lacking in many RCTs, questioning the validity of the results and the meta-analytic subgroup analysis. Based on improvement in oxygenation, only three RCTs successfully applied the optimal lung volume strategy during high-frequency ventilation. A total of 24 RCTs and three systematic reviews comparing various CMV modes and settings and two RCTs investigating permissive hypercapnia reported no differences in mortality or bronchopulmonary dysplasia. However, the intervention arms in these RCTs did not differ in tidal volume or positive end-expiratory pressures, variables that are considered important determinants in ventilator-induced lung injury. In fact, no RCT in newborn infants has substantiated so far the experimental finding that avoiding large tidal volumes and low positive end-expiratory pressure during CMV is lung protective in newborn infants.

CONCLUSION

RCTs investigating lung-protective ventilation in neonates have mainly focused on comparing high-frequency ventilation with CMV. Most of these RCTs show weaknesses in the design, which may explain the inconsistent effect of high-frequency ventilation on bronchopulmonary dysplasia. RCTs on CMV only focused on comparing various modes and settings, leaving the important question whether reducing tidal volume or increasing positive end-expiratory pressure is also lung protective in newborn infants unanswered.

Technical Innovations of Carinal Resection for Nonsmall-Cell Lung Cancer

BACKGROUND

We present our perioperative management of operable nonsmall-cell lung cancer invading the tracheobronchial bifurcation and the results obtained.

METHODS

Fifty consecutive patients undergoing carinal surgery with radical lymphadenectomy over a 5-year period were studied.

RESULTS

Eighteen patients (36%) were N2 and had chemoradiation (48 +/- 6 Gy) preoperatively. Surgery included 34 carinal pneumonectomies (24 right, 10 left), 11 carinal lobectomies (n = 6) or bilobectomies (n = 5), and 5 carinal resections, with (n = 3) and without (n = 2) reconstructions. Patients were ventilated through low tidal volume controlled techniques except during airway resection and reconstruction, during which the apneic (hyper) oxygenation techniques were used. High inspiratory oxygen concentrations, multiple collapse and reexpansions, hypoperfusion of the ipsilateral lung, and fluid overload were avoided. All patients but 1 were extubated in the operating room, 7 +/- 5 minutes after skin closure. Operative mortality (less than 30 days) and morbidity were 4% (n = 2) and 37% (n = 18), respectively. All resections but 1 (98%) R1 were complete. The number of resected nodes per patient was 9 +/- 2, and 7 (22%) of the 32 patients who had negative preoperative positron emission tomography results had micrometastatic mediastinal nodes. With a median follow-up of 38 months, actuarial 5-year and disease-free survivals were 51% and 47%, respectively. Disease-free survival was significantly affected by endobronchial extension (tracheobronchial angle invasion versus less than 0.5 cm from carina, p = 0.03) and nodal status (N0 versus N1-2, p = 0.02) in the multivariate analysis.

CONCLUSIONS

Preoperative chemoradiation, carinal lobectomy, or left pneumonectomy, and radical lymphadenectomy do not worsen the therapeutic index of carinal surgery. The high incidence of micrometastatic nodes in positron emission tomography-negative patients justifies routine mediastinoscopy and radical lymphadenectomy.