This month's issue of the Journal contains the proceedings of the 58th Respiratory Care Journal Conference, Monitoring Respiratory Function in Adult Acute Care, co-chaired by Lluis Blanch and Thomas Piraino. The conference was held in June of 2019 and focused on monitoring of both the ventilated and non-ventilated adult patients. The goal of the conference was to provide state-of-the-art reviews on traditional monitoring of gas exchange, new techniques for monitoring the diaphragm and distribution of ventilation, and assessment of asynchrony. The conference also explored monitoring in specific environments and the role of big data in predicting outcomes. The discussions were spirited and instructive.
Schmidt contributed the first paper on the traditional non-invasive monitoring of gas exchange including pulse oximetry, capnography, and transcutaneous sensors. He reviews the use of pulse oximetry for monitoring oxygenation as well as newer methods for determining carboxyhemoglobin and hemoglobin. The latter remain to show any real clinical utility. Capnography is discussed in relationship to monitoring ventilation, dead space, and the success of cardiopulmonary resuscitation. The role of transcutaneous carbon dioxide and its relationship to PaCO2 and end-tidal PCO2 are described.
Monitoring ventilator graphics has become a science of pattern recognition coupled with basic physiology to evaluate the patient's response to ventilatory support. Dexter and Clark review the use of pressure, volume and flow waveforms to measure compliance, airway resistance and respiratory mechanics. This paper includes the utility of the pressure-volume curve in monitoring lung characteristics and setting PEEP. Measures of work of breathing and surrogates are also considered.
Piraino provides an expert review on measuring lung volumes and the distribution of ventilation. Lung volume measures in ventilated patients have been used for decades with standard determinations of flow as well both helium dilution and nitrogen washout for functional residual capacity (FRC). Importantly, during mechanical ventilation, FRC is better termed end-expiratory lung volume to account for the effect of PEEP. Piraino introduces the principle of operation and utility of electrical impedance tomography (EIT). EIT represents the first bedside method to determine the regional distribution of ventilation, potentially allowing determination of both lung recruitment, pendelluft and overdistension. The key to the future of EIT is the ability to alter ventilation settings to impact the distribution of ventilation and impact patient outcomes.
Pham and colleagues provide an in-depth review of the use of esophageal manometry, including the important technical considerations and sources of error. They note that in spontaneously breathing patients, esophageal manometry can allow the measurement of work of breathing and determine the patient's response to mechanical ventilation. In passive subjects, esophageal manometry allows the determination of transpulmonary pressure and improves measures related to stress and strain. They describe the clinical indications for esophageal manometry as part of an individualized approach to ventilatory support.
Scott describes the measurements of breathing frequency, respiratory pattern and effort, particularly as it applies to the non-mechanically ventilated patient. Breathing frequency is a common determination that uses both manual recording as well as a number of non-invasive devices relying on air flow or changes in chest wall dimensions. Scott demonstrates that frequency is frequently measured, often miscalculated, and commonly overlooked with regard to the sensitivity with which it determines patient status. This paper also evaluates non-invasive measures of minute volume and details that can be garnered from monitoring respiratory pattern.
Schepens and others provide a detailed review regarding the importance of and methods for monitoring diaphragmatic function. They demonstrate that the impact of mechanical ventilation on diaphragmatic function is more important than previously thought. Measures of transdiaphragmatic pressures, diaphragmatic electromyogram and electrical activity of the diaphragm are described and the utility and pitfalls with each explained. The authors also detail the expanding knowledge regarding diaphragm protective ventilation.
Alarms are visual and aural displays alerting clinicians to the violation of pre-set monitored variables. Alarms are associated with clinician fatigue often related to unactionable nuisance alerts. Walsh and Waugh provide a review of alarm strategies, including systems which utilize multiple monitored variables to provide a global assessment of patient condition.
Rackley provides a practical review of monitoring mechanically ventilated patients. This includes the use of monitors of gas exchange, airway pressure, and lung volumes. Rackley's approach is pragmatic, assessing the real time, every day utility of monitoring described in earlier papers. He also includes monitoring endotracheal tube cuff pressures as this relates to both prevention of aspiration and airway injury.
Aquino-Esperanza and colleagues describe the incidence and importance of asynchrony during mechanical ventilation and define the most common asynchronies. They link asynchronous events with current pathophysiology and provide evidence for the association of asynchrony with outcomes. Importantly, this group has pioneered the automated detection of asynchrony and its implementation into ventilators and the electronic health record. This paper helps provide a road map for the future of asynchrony detection and mitigation.
Lamberti discusses the importance of monitoring patients outside the ICU, a location often disadvantaged by geography and patient to caregiver ratio. In the last decade, untoward events related to opioid administration have become too common and a target for quality improvement through monitoring. Lamberti also reviews the use of central monitoring and early warning systems aimed at preventing untoward complications and allowing intervention rather than rapid response.
Branson and Rodriquez describe monitoring in another environment often associated with untoward and commonly undetected events. Monitoring during transport describes the complications and mishaps affiliated with patient movement. This paper uses reported common complications as a template for which types of monitoring are required. Both interhospital and intrahospital transport have unique needs and hypobarism associated with aeromedical transport carries additional concerns. The importance of monitoring gas exchange during transport is emphasized along with methods to prevent airway complications and early warning indicators.
Smallwood tackles the issue of big data in monitoring the mechanically ventilated patient. He introduces key concepts, definitions and best practices as they relate to machine learning. He includes the pitfalls of big data gathered from the electronic medical record and the promise of big data as it relates to predicting success of ventilator liberation and response to ventilator manipulations. He concludes that artificial intelligence and big data are developing into an important part of respiratory care and as mature data collection systems are implemented, decision support tools can be built to provide insight to bedside clinicians.
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