Open Anesthesia: Resources on Pediatric Ventilation
Jeffrey Feldman, MD, MSE, FASA, Debnath Chatterjee, MD, FAAP, Aditee Ambardekar, MD, MSE, FASA
It is simply impossible for busy clinicians to keep up with relevant medical literature. Even a narrow-focused specialty like pediatric anesthesiology overwhelms our ability to “keep up” with novel medical breakthroughs, revisited research in the field, important quality improvement initiatives, interesting editorials, and updated clinical guidelines. There are multiple national and international journals devoted to Anesthesiology, not to mention the journal dedicated to our niche specialty: Pediatric Anesthesia. Reading them all would be impossible even if you never cared for patients. The late Dr. Ron Litman recognized this conundrum and started the Pediatric Anesthesia Article of the Day (PAAD). After his death, some of his friends continued the PAAD in his honor as a free resource to the worldwide pediatric anesthesia community. A multi-institutional Executive Council was formed after his death to further broaden PAAD's editorial reviews and scope, to ensure continuity and quality of the content, and to guide the long-term success of this unique endeavor.
We currently review 25+ PRINT journals each month and have not had the bandwidth to review alternative electronic media. We are pleased to announce that we are adding Dr. Debnath Chatterjee to our executive council and starting with today’s PAAD, we will begin to review electronic media regularly beginning with this series of articles on pediatric ventilation published on line in Open Anesthesia (OA).
What is Open Anesthesia (OA)? OA offers free online access to high-quality, peer-reviewed educational content on various anesthesiology, critical care, and perioperative medicine topics. OA includes summaries, podcasts with experts in the field, videos, and links to a wide range of educational resources. OA summaries are mini-reviews of high-yield topics that can be used to learn or quickly review a topic or teach in the perioperative setting. OA is sponsored by the International Anesthesia Research Society, the publisher of Anesthesia and Analgesia. Accessing all the free content on OpenAnesthesia requires a simple registration, login, and password, which allows OpenAnesthesia to identify its users. Myron Yaster MD
Learning to manage ventilation is fundamental to the practice of providing anesthesia care. Given the risk and impact of respiratory complications, it is essential to fully understand the different approaches to ventilation that are available to select the best option for a given clinical scenario and to optimize mechanical ventilation when it is needed. Mechanical ventilators not only provide the convenience of automating the ventilation process, they are also therapeutic tools used to prevent and correct pulmonary compromise. We are fortunate in pediatric anesthesia practice to have access to modern anesthesia ventilators designed to match the specifications of intensive care ventilators. Combined with respiratory monitoring integrated into the anesthesia workstation, the ventilator becomes an important and powerful tool for optimizing gas exchange while protecting the lungs from injury.
While modern anesthesia ventilators are designed to be highly effective for pediatric patients, it is essential that they be used properly to avoid complications and achieve the desired outcome. Small changes in intended ventilation can be highly significant, especially in small patients. In this issue of the PAAD, we summarize some resources available through Open Anesthesia (OA) to learn and review the important principles of ventilation during anesthesia care for pediatric patients. The title of each article has an embedded hyperlink to the actual publication on the OA website. A series of articles are available that cover fundamental concepts important to effective ventilation of the pediatric patient.
Eric Cheon MD and Jeffrey Feldman MD, MSEd: Pediatric Ventilation: Physiology
Link: https://www.openanesthesia.org/keywords/pediatric-ventilation-physiology/
This article reviews concepts of age-related physiology, lung protective ventilation, and dead space management. Lung protective ventilation has become an established strategy with clinical evidence for the efficacy of limiting tidal volume and distending pressure in specific patient populations. The original work that established this approach focused on adult patients with ARDS. Subsequent work in adult patients with normal lungs undergoing major surgical procedures indicated that lung protective ventilation is useful to prevent abnormalities with gas exchange and postoperative respiratory complications. Similar studies of pediatric patients with normal lungs undergoing anesthesia care are lacking, so current recommendations for lung protective strategies are primarily extrapolated from the literature in adults. The theory of ergotrauma focuses on the total energy used to provide ventilation, which is the product of pressure and volume delivered. This theory unifies the effect of pressure and volume on lung injury and underscores the reasonable approach of minimizing tidal volume and pressure as long as effective gas exchange is achieved.
Dead space management is a key point of this article that deserves emphasis. It is very easy to add elbows and heat and moisture exchangers (HME) between the y-piece and the patient’s airway, which increases dead space. This produces the same effect of increased CO2 production and would require a compensatory increase in minute ventilation to achieve normocarbia. Ideally, apparatus dead space should not exceed one-third of the desired tidal volume. If the goal of lung-protective ventilation is to minimize the energy to which the lung is exposed, adding dead space works against that goal.
Brian Tashjian MD and Young May Cha MD: Pediatric Bag-Mask Ventilation
Link: https://www.openanesthesia.org/keywords/pediatric-bag-mask-ventilation/
This article reviews bag-mask ventilation with an emphasis on technique and device selection. As the most fundamental skill for arguably all healthcare professionals, especially in the acute care setting, this review offers an important summary. Starting from proper mask selection and hand position, this article provides practical guidance on technique, device selection, and the use of assist devices like oro- and naso-pharyngeal airways.
Jeffrey Feldman MD, MSEd: Pediatric Ventilation: Breathing Circuits
Link: https://www.openanesthesia.org/keywords/pediatric-ventilation-breathing-circuits/
This article reviews the various breathing circuits commonly used when caring for pediatric patients. Specifically, manual circuits, both self- and flow-inflating, the circle system, which is unique to anesthesia delivery systems and ICU ventilators, are discussed. The role of these different circuits in modern pediatric anesthesia practice is reviewed along with the clinical indications and potential complications.
Manual bags are useful for patient transport and should always be readily available in the operating room and ICU for rescue should a mechanical ventilator fail. While self-inflating manual bags have the advantage of being able to ventilate without an external gas supply, flow-inflating bags are typically preferred since they offer greater tactile feel of lung compliance and tidal volume and can be used to support spontaneous or controlled ventilation. Circle systems are the mainstay in procedure areas where an anesthesia machine is used. Modern anesthesia machines and circle systems are quite effective for even the most challenging ventilation scenario as long as the leak and compliance test is performed properly and apparatus dead space is managed. ICU ventilators are generally considered to be the most capable device for mechanical ventilation. During patient transport, a portable ICU ventilator is preferred to a manual bag since it provides consistent ventilation and can easily deliver oxygen in concentrations less than 100%. In the operating room, however, an ICU ventilator may not be the best choice. Modern anesthesia machines, in general, match the specifications of ICU ventilators and also offer advantages of delivering inhaled anesthetics and easy transition between manual and mechanical ventilation.
Anthony Alexander MD and Jeffrey Feldman MD MSEd: Pediatric Ventilation: Anesthesia Ventilators
Link: https://www.openanesthesia.org/keywords/pediatric-ventilation-anesthesia-ventilators/
This article reviews the four different designs for modern anesthesia ventilators – bellows, piston, turbine and volume manifold or reflector. All of these designs incorporate the fundamental advances of compliance and fresh gas flow compensation that enable accurate tidal volume delivery when using a volume-targeted mode of ventilation and accurate tidal volume measurement in all modes of ventilation. Since the configuration of the breathing circuit determines compliance, it is essential to perform the compliance test prior to starting the procedure and to not alter the breathing circuit configuration once that test is completed. A simple change like extending an expandable circuit, or adding an extension to the y-piece after the compliance test can reduce the effectiveness of the ventilator, especially in small patients.
Patient monitoring is also essential to maximizing the effectiveness of mechanical ventilation. The goals of optimal ventilation are:
adequate arterial oxygen tension (PaO2) at the least possible fraction of inspired oxygen concentration (FiO2)
acceptable arterial carbon dioxide tension (PaCO2)
adequate tidal volumes with the lowest possible inspiratory pressures
While arterial blood gas analysis is the gold standard for assessing ventilator effectiveness, bedside monitors are the most practical tools in most patients. Pressure and volume monitoring provides insight into lung compliance. Pulse oximetry is very valuable but only sensitive for detecting oxygenation problems when the FiO2 is not greater than 25-30%.
Jeffrey Feldman MD MSEd: Pediatric Ventilation: Modes of Ventilation
Link: https://www.openanesthesia.org/keywords/pediatric-ventilation-modes-of-ventilation/
This article reviews the various modes of ventilation typically available when using a modern anesthesia ventilator. Modes of ventilation that previously were only available on ICU ventilators have been incorporated into the design of most modern anesthesia ventilators. Anesthesia caregivers now have access to a selection of anesthesia modes that support spontaneous ventilation, provide volume- or pressure-targeted mechanical continuous ventilation and also provide synchronized ventilation. In the past, delivering volume-targeted ventilation at small tidal volumes was not reliable due to the impact of circuit compliance and fresh gas flow, but modern anesthesia machines compensate for those interactions. There are differences between anesthesia machines in the capabilities at small tidal volumes, and the minimum tidal volume specification published by the manufacturer in the instructions for use (IFU) provides that information. In general, there is no one perfect mode of ventilation. Volume-targeted modes are useful during lung-protective ventilation, where a specific tidal volume target is desired, but inspiratory pressure must be monitored as it will vary with lung compliance. Similarly, pressure-targeted ventilation is useful for ensuring a maximum pressure is not exceeded, but volume should be monitored since it will vary with lung compliance. The pros and cons of commonly available ventilator modes are summarized. Respiratory monitoring, which is essential to ensuring that the ventilator is functioning as desired and optimal gas exchange is achieved, is reviewed.