From the Guidelines
To correctly interpret an anesthesia monitor, particularly in Pressure Support Ventilation (PSV) mode, focus on vital signs and key parameters such as Pressure Support level, PEEP, FiO2, and trigger sensitivity, while also considering the patient's clinical assessment and potential for sleep disruption due to central apneas 1. When interpreting an anesthesia monitor in PSV mode, it is essential to understand the parameters displayed and their implications for patient care. Key parameters include:
- Pressure Support level (usually 5-15 cmH2O), which is the additional pressure provided during inspiration
- PEEP (Positive End-Expiratory Pressure, typically 3-5 cmH2O) maintaining airway pressure at end-expiration
- FiO2 (fraction of inspired oxygen, 21-100%)
- Trigger sensitivity determining how much patient effort initiates a breath The monitor also displays respiratory rate, tidal volume, and minute ventilation, which help assess ventilation adequacy and patient comfort. According to the most recent guidelines, monitoring during anesthesia should include ECG, SpO2, NIBP, and capnography, with alarm limits set to patient-specific values and audible alarms enabled 1. It is crucial to adjust the level of assistance in PSV mode to prevent hyperventilation and central apneas, particularly in patients with chronic heart failure, as high levels of PSV can cause sleep disruption and negatively impact sleep quality 1. Always correlate monitor readings with clinical assessment of the patient, as monitors can sometimes give false readings due to technical issues or patient factors. The use of modes with backup ventilation, such as assist-control mode or synchronized intermittent mandatory ventilation, may prevent periodic breathing during sleep, although they may have other downsides if they put the respiratory muscles excessively at rest 1. In summary, correct interpretation of an anesthesia monitor in PSV mode requires a comprehensive understanding of the parameters displayed, as well as consideration of the patient's clinical assessment and potential for sleep disruption, with the goal of optimizing ventilation adequacy and patient comfort, while minimizing the risk of morbidity and mortality, and improving quality of life.
From the Research
Understanding Pressure Support Ventilation (PSV) Parameters
To interpret an anesthesia monitor, particularly the parameters in Pressure Support Ventilation (PSV), it is crucial to understand the concepts and measurements involved. The key parameters include:
- Tidal volume (Vt)
- Inspiratory effort (Pmus)
- Respiratory system compliance (Crs)
- Pressure support level
Interpreting PSV Parameters
The correct interpretation of these parameters is vital to ensure adequate ventilation and avoid under- or over-assistance. According to 2, a conceptual model can be used to describe the interaction between patient and ventilator in PSV, and how Crs affects this interaction. The model suggests that there is a patient-specific range of PSV levels, within which the inspiratory effort is modulated to keep Vt relatively steady.
Clinical Application of PSV
In clinical practice, the use and management of PSV have been studied in various patient populations. For example, 3 found that in patients receiving prolonged invasive ventilation, almost two-thirds received PSV, which accounted for 40.5% of mechanical ventilation time. However, the study also found that half of the PSV-treated patients were exposed to high tidal volume and two-thirds to likely over-assistance.
Ventilator-Derived Parameters
In addition to PSV parameters, other ventilator-derived parameters should be monitored to guide ventilator strategies. According to 4, these parameters include intrinsic PEEP, peak and plateau pressures, driving pressure, transpulmonary pressure, mechanical energy, mechanical power, and intensity. During assisted mechanical ventilation, the pressure generated 100 ms after onset of inspiratory effort and the pressure-time product per minute should also be evaluated.
Programming PSV
Programming PSV requires careful consideration of various factors, including patient age, weight, compliance, and resistance. According to 5, in pediatric patients, the flow-trigger setting and the level of pressure support can be programmed using common clinical noninvasive variables. However, more studies are needed to estimate the level of pressure support required in other clinical situations.
Monitoring Ventilation and Compliance
Monitoring ventilation and compliance is crucial to ensure patient safety and optimize ventilation. According to 6, Side Stream Spirometry is a technology that allows clinicians to monitor pressure, volume, flow, compliance, and resistance during routine anesthesia practice. This technology provides continuous monitoring of lung mechanics and gas dynamics, enabling clinicians to optimize ventilation and ensure adequate oxygenation.