Update: adjuncts to mechanical ventilation

Tidal volume in mechanically ventilated dogs: can human strategies be extrapolated to veterinary patients?

This paper compares and describes the tidal volume (Vt) used in mechanically ventilated dogs under a range of clinical conditions. Twenty-eight dogs requiring mechanical ventilation (MV) were classified into 3 groups: healthy dogs mechanically ventilated during surgery (group I, n = 10), dogs requiring MV due to extra-pulmonary reasons (group II, n = 7), and dogs that required MV due to pulmonary pathologies (group III, n = 11). The median Vt used in each group was 16 mL/kg (interquartile range [IQR], 15.14-21) for group I, 12.59 mL/kg (IQR, 9-14.25) for group II, and 12.59 mL/kg (IQR, 10.15-14.96) for group III. The Vt used was significantly lower in group III than in group I (p = 0.016). The thoraco-pulmonary compliance was significantly higher in group I than in groups II and III (p = 0.011 and p = 0.006, respectively). The median driving pressure was similar among the groups with a median of 9, 11, and 10 cmH₂O in groups I, II, and III, respectively (p = 0.260). Critically-ill dogs requiring MV due to the primary pulmonary pathology received a significantly lower Vt than healthy dogs but with a range of values that were markedly higher than those recommended by human guidelines.

Management of blunt pulmonary injury

Thoracic injuries account for 25% of all civilian deaths. Blunt force injuries are a subset of thoracic injuries and include injuries of the tracheobronchial tree, pleural space, and lung parenchyma. Early identification of these injuries during initial assessment and resuscitation is essential to reduce associated morbidity and mortality rates. Management of airway injuries includes definitive airway control with identification and repair of tracheobronchial injuries. Management of pneumothorax and hemothorax includes pleural space drainage and control of ongoing hemorrhage, along with monitoring for complications such as empyema and chylothorax. Injuries of the lung parenchyma, such as pulmonary contusion, may require support of oxygenation and ventilation through both conventional and nonconventional mechanical ventilation strategies. General strategies to improve pulmonary function and gas exchange include balanced fluid resuscitation to targeted volume-based resuscitation end points, positioning therapy, and pain management.

A Survey of Mechanical Ventilator Practices Across Burn Centers in North America

Burn injury introduces unique clinical challenges that make it difficult to extrapolate mechanical ventilator (MV) practices designed for the management of general critical care patients to the burn population. We hypothesize that no consensus exists among North American burn centers with regard to optimal ventilator practices. The purpose of this study is to examine various MV practice patterns in the burn population and to identify potential opportunities for future research. A researcher designed, 24-item survey was sent electronically to 129 burn centers. The χ, Fisher's exact, and Cochran-Mantel-Haenszel tests were used to determine if there were significant differences in practice patterns. We analyzed 46 questionnaires for a 36% response rate. More than 95% of the burn centers reported greater than 100 annual admissions. Pressure support and volume assist control were the most common initial MV modes used with or without inhalation injury. In the setting of Berlin defined mild acute respiratory distress syndrome (ARDS), ARDSNet protocol and optimal positive end-expiratory pressure were the top ventilator choices, along with fluid restriction/diuresis as a nonventilator adjunct. For severe ARDS, airway pressure release ventilation and neuromuscular blockade were the most popular. The most frequently reported time frame for mechanical ventilation before tracheostomy was 2 weeks (25 of 45, 55%); however, all respondents reported in the affirmative that there are certain clinical situations where early tracheostomy is warranted. Wide variations in clinical practice exist among North American burn centers. No single ventilator mode or adjunct prevails in the management of burn patients regardless of pulmonary insult. Movement toward American Burn Association-supported, multicenter studies to determine best practices and guidelines for ventilator management in burn patients is prudent in light of these findings.

Computerized Decision Support Systems for Mechanical Ventilation in Children

Mechanical ventilation is an effective treatment in the ICU but can have significant adverse effects. Approaches from adult research have been adopted in pediatric critical care despite known differences in respiratory physiology and ICU processes. There continues to be considerable variation in how ventilators are managed. Computerized decision support systems implement explicit protocols, and are designed to make mechanical ventilation management safer, more consistent, and more lung protective. Variable results and low or unknown compliance with protocols and CDSS tools have been reported. To date, there has been limited research regarding CDSS for mechanical ventilation in children.

Effects on lung stress of position and different doses of perfluorocarbon in a model of ARDS

We determined whether the combination of low dose partial liquid ventilation (PLV) with perfluorocarbons (PFC) and prone positioning improved lung function while inducing minimal stress. Eighteen pigs with acute lung injury were assigned to conventional mechanical ventilation (CMV) or PLV (5 or 10 ml/kg of PFC). Positive end-expiratory pressure (PEEP) trials in supine and prone positions were performed. Data were analyzed by a multivariate polynomial regression model. The interplay between PLV and position depended on the PEEP level. In supine PLV dampened the stress induced by increased PEEP during the trial. The PFC dose of 5 ml/kg was more effective than the dose 10 ml/kg. This effect was not observed in prone. Oxygenation was significantly higher in prone than in supine position mainly at lower levels of PEEP. In conclusion, MV settings should take both gas exchange and stress/strain into account. When protective CMV fails, rescue strategies combining prone positioning and PLV with optimal PEEP should improve gas exchange with minimal stress.

Management of Blunt Pulmonary Injury

Thoracic injuries account for 25% of all civilian deaths. Blunt force injuries are a subset of thoracic injuries and include injuries of the tracheobronchial tree, pleural space, and lung parenchyma. Early identification of these injuries during initial assessment and resuscitation is essential to reduce associated morbidity and mortality rates. Management of airway injuries includes definitive airway control with identification and repair of tracheobronchial injuries. Management of pneumothorax and hemothorax includes pleural space drainage and control of ongoing hemorrhage, along with monitoring for complications such as empyema and chylothorax. Injuries of the lung parenchyma, such as pulmonary contusion, may require support of oxygenation and ventilation through both conventional and nonconventional mechanical ventilation strategies. General strategies to improve pulmonary function and gas exchange include balanced fluid resuscitation to targeted volume-based resuscitation end points, positioning therapy, and pain management.

Extracorporeal membrane oxygenation as an alternative to ventilation

PURPOSE OF REVIEW

Following the recent H1N1 epidemic, there has been renewed interest in using extracorporeal membrane oxygenation (ECMO) as a treatment for acute respiratory failure. Currently, following the advances in technology, ECMO is now recommended as a definitive treatment for acute respiratory failure. However, there have been limited randomized trials and cohort studies evaluating this therapy.

RECENT FINDINGS

Currently, results imply that ECMO is superior to conventional ventilation providing lung rest. There is expansion in the indications for ECMO including a bridge to lung transplantation, the use of ECMO in awake patients, liver transplantation, as well as in adult respiratory distress syndrome. This article looks at the current indications and uses.

SUMMARY

Further studies are warranted to define and validate the role of ECMO, including studying the pharmacodynamics and pharmacokinetics of patients receiving support. The use of sedatives and antibiotics may be required to be changed significantly. If the incidence of intracerebral haemorrhage can be decreased, then in the author's opinion it may become the first-line treatment for acute respiratory failure.