Transcutaneous Electrical Stimulation for Apnea Detected by Capnography

Recruitment in the TES pilot trial is defined as the number of eligible study participants who agreed to participate in this pilot trial compared to the total number of eligible participants who met the inclusion criteria. The Participant Recruitment and Follow-Up Form will be completed by the researcher and used to track recruitment procedures (i.e., recruitment rates and reasons for participation and non-participation). Participants are not required to provide a reason for declining to participate in the research. However, if they choose to share their reasons, we will note their reasons for refusal.

Retention is defined as the number of participants who enroll and stay in this pilot trial through completing the follow-up assessment at the end of the observation period among the total trial participants. This variable is measured using the Participant Recruitment and Follow-Up Form. The form has the following items: TESCapno trial ID, completing pain assessment, TES and opioid related adverse events form in both groups.

Acceptability of the intervention will be assessed using the Intervention Acceptability Form and will be completed by participants at the end of observation period. Acceptability of the TES is a self-report questionnaire developed by the researchers containing 5-point Likert scales: 1= "strongly disagree"; 2= "disagree"; 3= "neutral"; 4= "agree"; 5= "strongly agree". Responses to Likert scale questions will be reported using means and standard deviations. In the absence of reference interpretations of the acceptability questionnaire, the midpoint of Likert scale will be selected as the minimum level of acceptability of the TES device.

Apnea is defined as the cessation of breathing for a minimum of 10 seconds, and it's the most repetitive feature of opioid-induced respiratory depression (OIRD) in postoperative patients. Therefore, for the purpose of this study, the cumulative duration of detected apnea events lasting ≥ 10 seconds over the duration of recording in both groups will be captured using continuous capnography measurements with the Capnostream device. The Capnostream™ 20p monitor (Medtronic) will be used to offer "real-time" observation of apnea.

During the observation period, the incidence of RD episodes in the PACU will be captured by continuous capnography and pulse oximetry measurements and recorded to a laptop in conjunction with the clinical data as reported by the research student. The clinical data and monitor parameters specified below are considered an episode of RD:

• EtCO2 ≤ 15 or ≥ 60 mmHg for ≥ 3 minutes.
• RR ≤ 5 breaths for ≥ 3 minutes.
• SpO2 ≤ 85% for ≥ 3 minutes.
• Apnea episode lasting ≥ 30 seconds
• Any respiratory opioid-related adverse drug event (rORADE)

During the observation period, nursing interventions aimed at addressing respiratory depression include providing verbal instructions to encourage breathing, physically stimulating the patient, employing a stir-up regimen (repositioning, coughing, deep breathing, and incentive spirometry), and increasing or adding supplemental oxygen will be recorded.

A researcher-designed questionnaire will be used to evaluate the nursing interventions aimed at addressing respiratory depression. This questionnaire will assess the implementation of interventions, such as verbal stimulation, tactile stimulation, the stir-up regimen (repositioning, coughing, deep breathing, and incentive spirometry), and the use of increased or supplemental oxygen.

At the end of the observation period, the researcher will inspect participants' skin integrity around the TES region to assess for anticipated and unanticipated adverse events in the all groups. The adverse events will be considered as painful sensations or other uncomfortable reactions, including cutaneous injuries, unresolved numbness, tingling of extremity, skin irritation, tenderness or soreness, and discomfort.

Before starting the intervention and at the end of the observation period, subjective pain assessments will be performed using a visual analog scale (VAS). The VAS utilizes a 100-mm horizontal line, marked from 0 to 10 from left to right, where zero represents 'no pain' and 10 represents the 'worst possible pain.' Participants will be asked by the researcher to indicate on the line the point that corresponds to their perception of their current pain level. This scale allows for the measurement of pain, which can range across a continuum from no pain to the most severe pain imaginable. The VAS is easy to use, valid and reliable compared with other pain rating scales (r=.71-.78, intraclass correlation coefficient [ICC]=.71-.99).

At the end of observation period, intraoperative and postoperative administration of opioids will be recorded and then converted to total morphine milligram equivalents (MME), a standardized unit that allows for comparison across different opioid types. This is done by multiplying the quantity and dose, and applying standard conversion tables.