© Springer International Publishing Switzerland 2017
Basavana G. Goudra and Preet Mohinder Singh (eds.)Out of Operating Room Anesthesia10.1007/978-3-319-39150-2_1515. Ventilation Strategies Including High Frequency Jet Ventilation
(1)
Department of Anesthesiology, Emory University Hospital, Atlanta, GA, USA
(2)
Division of Cardiothoracic Anesthesiology, Department of Anesthesiology, Emory University Hospital, 1364 Clifton Rd NE, Atlanta, GA 30322, USA
Abstract
The number of diagnostic and therapeutic interventions performed outside of the operating room requiring anesthesia services has expanded several fold over the last several decades. With advances in medical research, new technology, and the increasing survival of complicated and elderly patients the role of the anesthesiologist in providing non-operating room anesthesia will continue to expand. Recent studies and advances in non-traditional ventilation techniques including lung-protective ventilation, jet ventilation and non-invasive ventilation have a promising outlook for current and future utilization in non-operating room anesthesia. It will continue to be the responsibility of the anesthesiologist to provide the same standard of care that a patient would receive in the operating room, including the use of capnography and assessment of adequate ventilation, to ensure safe outcomes in a higher risk patient population in the non-operating room environment.
Keywords
High-Frequency Jet VentilationLow-Frequency Jet VentilationNon-Operating Room AnesthesiaLung-Protective VentilationVentilator-Induced Lung InjuryAtrial FibrillationPulmonary Vein IsolationRadiofrequency Catheter AblationCapnographyMonitored Anesthesia CareNon-Invasive VentilationIntroduction
The number of diagnostic and therapeutic interventions performed outside of the operating room requiring anesthesia services has expanded several fold over the last several decades. With advances in medical research, new technology, and the increasing survival of complicated and elderly patients the role of the anesthesiologist in providing non-operating room anesthesia (NORA) will continue to expand. The areas of activity that anesthesia providers may be involved in currently and in the future include diagnostic imaging, cardiac interventions, intervention radiology and gastrointestinal and urology suites. With this expanded role it requires attention to the same requirements for safe anesthetic care for patients that are followed in the operating room. An area often overlooked by anesthesia providers is the method of ventilation and its effects in NORA. Recent study and advances in non-traditional ventilation techniques including jet ventilation have a promising outlook for current and future utilization in NORA [1, 2].
Offsite Environment Challenges
Procedures requiring NORA are often complex, can take a significant time to complete and usually involve high acuity patients. These factors require that anesthesia providers play an integral role in patient care and patient safety initiatives [1]. A major challenge to patient care includes the problems that arise from the physical environment in which NORA is often delivered, including: space limitations, availability of gas supplies, suction, and electrical supply. Something as simple as ambient lighting may be overlooked [3]. Equipment may be mobile, unfamiliar or found in different locations when compared to standard operating rooms and requires an adaptable and vigilant anesthesiologist.
In the NORA environment, pipeline gas supplies may not be available and the sole supply of gas may be the cylinder mounted on the anesthesia machine. An anesthesia provider must know how long the cylinder gas supply will last as this gas supply is finite and based on size of the cylinder and total fresh gas flow used [3].
There is typically no anesthesia workroom nearby if items are needed in an emergency so any out of the operating room (OOR) site should be stocked with additional equipment and medications that anesthesia providers would routinely need to manage a hemodynamically unstable patient, unplanned event or difficult airway [1].
Access may be limited to the patient once the procedure has started, especially in the cardiac catheterization lab or interventional radiology suite due to imaging equipment. Movement of the procedural table and fluoroscopy may be unpredictable and this may require the use of long intravenous lines and breathing circuits [1].
It is important to establish communication prior to the initiation of anesthesia because unlike the operating room environment, proceduralists may not be used to anticipating the actions and needs of an anesthesia providers. In the OOR setting much of the procedure can only be ascertained from the fluoroscopy screen and communication should be collaborative to optimize patient care and safety [1].
Standard Ventilation for NORA
When traditional intermittent positive pressure ventilation (IPPV) is employed under general anesthesia, most anesthesia machines used in both the operating room and OOR settings are capable of volume control or pressure control ventilation modes. Newer variations provide additional modes as well such as volume guaranteed-pressure control ventilation and various types of pressure support.
Depending on patient’s characteristics, tidal volumes are adjusted to provide between 6 and 8 mL/kg, based on predicted body weight (PBW) rather than actual body weight (ABW)
PBW for males: 50 kg + 2.3 kg (height[in] – 60) and females: 45.4 kg + 2.3 kg (height[in] -60) [4]
Care must be exercised to not over-ventilate obese, short or female patients
Delivering a tidal volume of 600–800 mL for an average person is associated with movement of the chest wall, lungs, heart, and abdomen [5].
Recently, lung protective ventilation (LPV) strategies have been studied and developed to minimize the risks of ventilator-induced lung injury (VILI) that may be associated with mechanical ventilation in critically ill patients. These strategies have encouraged anesthesiologists to consider LPV in susceptible non-injured lungs as well, especially in the complex patient population that may require diagnostic and therapeutic interventions outside of the operating room. VILI involves a complex interaction of over-distention (volutrauma), increased transpulmonary pressure (barotrauma), cyclic opening and closing of alveoli (alelectotrauma) and inflammatory mediators (biotrauma) [6].
LPV typically consists of tidal volumes of 6–8 mL/kg based on patient’s PBW and other characteristics, PEEP of ≥5 cmH2O and recruitment maneuvers and may play a role in OOR ventilation strategies [4].
LPV can improve lung mechanics, gas exchange and decrease the incidence of postoperative pulmonary complications, including ALI/ARDS, pulmonary infection and atelectasis in previously non-injured lungs [7].
LPV involves the mindfulness of the anesthesia provider of targeted intraoperative tidal volume selection based on patient lung risk factors, gender and height [4].
Jet Ventilation for NORA
High-frequency jet ventilation (HFJV) is a technique that is most frequently used in the intensive care unit and in the OR during airway and laryngeal surgeries but has seen recent clinical penetration in areas outside of the intensive care unit (ICU) and operating rooms.
In the operating room HFJV is often used for tracheal resection and complex reconstruction
In the ICU it has been used for adult patients with acute respiratory distress syndrome [8].
In the pediatric population it has shown benefit in children with persistent pulmonary hypertension of the newborn [9].
The use of HFJV in NORA is gaining application for providing mechanical ventilation where conscious sedation may not provide the necessary depth of patient comfort, safety and most favorable working conditions for the procedure. The ability to provide mechanical ventilation under general anesthesia with minimal movement of the thorax and abdomen is appealing to procedures where even slight motion artifact from spontaneous or intermittent positive pressure ventilation may significantly affect the duration and success of the procedure. A small tidal volume repeated at a high frequency allows the chest and abdomen to remain relatively motionless while supplying adequate oxygenation and ventilation [5]. Each patient must be evaluated for HFJV but any patient that is hemodynamically stable enough to tolerate induction and general anesthesia with IPPV is likely an appropriate candidate for HFJV [2].
Types of Jet Ventilation
Jet ventilation may be high- or low-frequency with similar general principles between the two methods. Both utilize jet-streams originating from high-pressure sources controlled by flow interruption devices, either hand-held or electronically controlled. Expiration is dependent on passive lung and chest-wall recoil. While much of the gas exchange in low-frequency jet ventilation (LFJV) is achieved by means of convective ventilation or bulk flow, successful gas exchange in HFJV is achieved by a relatively greater contribution of other mechanisms of gas exchange due to the smaller tidal volumes utilized in HFJV. Unlike conventional ventilation, tidal volumes during HFJV are often smaller than anatomical and equipment dead space and therefore alternative mechanisms of ventilation occur. These include laminar flow, Taylor-type dispersion, Pendelluft or collateral ventilation, molecular diffusion and cardiogenic mixing [10].
LFJV is usually applied by a hand-triggered device and is often limited to short diagnostic procedures such as laryngoscopy or bronchoscopy or as an important management strategy of a “can’t intubate, can’t ventilate” situation during a difficult airway [10].
During LFJV, a jet frequency of 8–10 breaths per minute allows sufficient time for exhalation via passive recoil of the lung and chest wall while preventing air-trapping and buildup of pressure in small airways [10].
HFJV is achieved by commercially available jet ventilators that deliver a continuous flow of pressurized gas that is chopped into adjustable jets by a high-frequency flow interrupter valve [10].
All ventilators are equipped with an airway pressure alarm and automatic shutdown that will stop gas flow in the presence of unintentional high airway pressures [10].
High Frequency Jet Ventilation
Several different ventilators are commercially available in the United States and internationally to provide HFJV, including the Monsoon jet ventilator (Acutronic Medical Systems, Fabrik im Shiffli, Switzerland) and the Life Pulse high frequency jet ventilator (Bunnell Incorporated, Salt Lake City, UT). The variables that can be manipulated are respiratory rate, inspiratory time and driving pressure [2]. Oxygen delivery depends on the set FiO2 as well as the degree of room air entrainment. The tidal volume is not set but is rather a function of driving pressure, cannula/airway resistance, inspiratory time, entrainment volume, and the impedance of the respiratory system [10].
Respiratory Rate/Frequency
The respiratory rate may be adjusted from 12 to 150 breaths per minute
Often initiated at 120 breaths per minute based on clinical observation that it provides adequate CO2 elimination
Unlike traditional ventilation, the efficiency of CO2 elimination will typically decrease as the respiratory rate increases [2]
