Presentation ways of monitored parameter values
OverviewThere are four common forms of parameter value monitoring, see [Tobin2013] p.91:
-waveforms and loops,
The most common parameter value representations are numerical values.
Trendlines are graphs, that show monitored parameters and their changes over long periods of time.
Waveforms and loops
Waveforms are temporal representations of airway pressure, volume and flow see e.g., [Rimensberger2015] p.318.
Waveforms are used to identify changes in settings or mechanics in the ventilation level or to identify sources of patient–ventilator asynchrony,
If two parameters are displayed as a function of each other instead of functions of time, the representation is called loop.
The most common pulmonary loops are pressure volume (PV) loops, see [Rimensberger2015] p.333, 361 and flow volume (FV) loops, see [Rimensberger2015] p.319, 360.
PV loops are useful in the identification of optimum PEEP levels and over-distension.
FV loops are often used to identify the response to bronchodilators.
There are fundamental difference between the flow/volume loops in classical spirometry and in mechanically ventilated patients.
In the mechanical ventilated patient the loop is upside-down, because the patient forcibly exhales into the machine.
The peak expiratory flow rate and the shape of the expiratory flow-volume curve are the best measures of airway resistance. In case of mechanically ventilated patient, the turbine gives rise to a controllable and adjustable inspiratory flow. The inspiratory flow part of the loop is therefore more reflective of lung compliance: as the lung distends, the flow decreases. Then, the patient exhales passively; here airway resistance will be revealed as the determinant of expiratory flow rate.
There are different forms of advanced graphics, see [Tobin2013] p.91.