## 4 Case Studies
### Weaning Protocol Case Study  
In Ward \(C\), we analyzed the weaning protocol for patients that were ventilated for less than 72 h. During a surgical procedure, the ventilation of the patient is taken over by a mechanical ventilator. After surgery, the ventilator continues to support the patient's ventilation until sufficient spontaneous breathing activity occurs. The process of reduction in the level of support is a stepwise procedure, described in the protocol and shown in Figure 4.  
The weaning protocol can be divided into three basic phases: Bi-level positive airway pressure (BIPAP), assisted spontaneous breathing (ASB) and extrusion phases (stopping support by mechanical ventilation). In the BIPAP phase, the whole breathing is taken over by the mechanical ventilator. When a patient fulfills the criteria from Note A, he/she can enter the ASB Phase, in which the breath is initiated by the patient and supported by the ventilator. The support of the mechanical ventilator is gradually decreased, while the state  
Figure 4: The weaning protocol used in the case study. of the patient is monitored by the nurses. When the patient is fully breathing without any support from the ventilator and is stable for 30 min (as described by note B), he/she enters the extubation phase. The patient is extubated when he/she fulfills the criteria in Note C, which means that the tube is removed and the patient is disconnected from the mechanical ventilator. This ends the weaning protocol. We received the data of 2473 patients that underwent cardiothoracic surgery between August 2012 and April 2015. The data contained information regarding patient-related indicators, measured with different frequency, either automatically or manually. In addition, the settings of the ASB machine were captured, unfortunately only once in every 30 min, and not with each change in the values. Some variables or activities were not registered. Therefore, for this protocol, with the available data, one possibility is to focus on the compliance at the decision points of whether to start decreasing the ventilatory support while breathing and whether to extubate the patient. We could detect those points for 1680 patients. The decisions are guided by several conditions described by Note A and Note C, respectively. The thresholds present in Notes A and C, for which we received the data, are shown in Table 5. This table also shows the deviation thresholds and importance of each of those criteria. For note A, we check six criteria, and for note C, we check eight criteria. Table 6 shows different compliance values according to different measures. First, there were many missing data--for note A around 44% and for note C around 30%. Therefore, we decided to treat the unknown information as non-compliant. This is a natural and straightforward interpretation, as there is no evidence that the protocol was being followed in those cases. This vast amount of missing data causes all the compliance values to be low, especially for measures with higher compliance expectations (i.e., most patients have most of their activities compliant). We use this approach since the protocols are created from the evidence of past cases that reflect, e.g., the best known, used and applicable conditions that influence the process, as in the case of the weaning protocol. Moreover, we can also see the influence of the activity importance on the compliance values. This is especially visible when we calculate the compliance for the note C condition, where almost 15% are strictly non-compliant. The fuzzy compliance enables assessing whether the violation of the strict threshold was substantial or only marginal.