Subclause 6.4 – Disclosure of delays

ü If an event occurs in the PATIENT or the equipment that should result in the generation of ALARM SIGNALS, the generation should occur promptly. For example, clinicians would expect an ALARM SIGNAL soon after an abrupt fall in heart rate to a value below the lower ALARM LIMIT for heart rate, or once apnea or asystole has occurred. This is usually the case.

ü However, in some situations, ALARM SIGNAL generation can be delayed to such an extent that the delay can be clinically significant. This collateral standard recognizes that there are two fundamentally different potential causes for these delays.

ü First, it can take some time for the ALARM SYSTEM to determine that an ALARM CONDITION is present after the occurrence of a valid triggering event in the PATIENT. This delay is defined as the ALARM CONDITION DELAY. It can be due to:

– artifact rejection algorithms, or

– INTELLIGENT ALARM SYSTEMS that include event duration as part of the algorithm, or

– aperiodic measurement (e.g., intermittent non-invasive blood pressure monitoring).

ü When the ALARM SYSTEM is aperiodically measuring rather than continuously monitoring a variable, there can be a significant delay between the time that an event occurs in the PATIENT and when that event is detected. If the OPERATOR is unaware of this, incorrect treatment decisions can occur. The time between measurements is considered to be part of the ALARM CONDITION DELAY.

ü In the case of apnea or asystole, the valid triggering event in the PATIENT has not occurred until the absence of respiration or heart rate has existed for a defined period of time. Because this defined period of time is required to pass before the event itself exists, it is not included as part of the ALARM CONDITION DELAY. See also the rationale for Definition 3.2.

M Second, the generation of ALARM SIGNALS can lag some time after the ALARM SYSTEM has determined that an ALARM CONDITION exists. This delay is defined in this document as the ALARM SIGNAL GENERATION DELAY. In most ALARM SYSTEMS this delay is usually clinically insignificant, but can be important, for example, when paging systems or networked remote devices are used to generate ALARM SIGNALS. See also the rationale for Subclause 6.10.

אולי ההנחיה צריכה להיות שההתרעות לא תושהינה על ידי רשת התקשורת.

M A further complication can occur when the ALARM SYSTEM is not continuously monitoring, but is aperiodically measuring the variable that causes an ALARM CONDITION, e.g. a non-invasive blood pressure monitor. There can be a significant delay between when an event occurs in the PATIENT and when that event is detected. If OPERATORS are unaware of this likelihood, incorrect treatment decisions can occur.

זה לא נכון להטיל את האחריות על המשתמש. הנכון הוא לחייב זמן השהיה מירבי בשיעור של חלק קטן 10-20% של הזמן הנדרש לתחילת הטיפול בחולה

ü In that case, the time between measurements is considered to be part of the ALARM CONDITION DELAY.

Figure A.1 illustrates the components of ALARM SYSTEM delay for a PHYSIOLOGICAL ALARM CONDITION normalized variable.

Figure A.1 – Graphical representation of components of ALARM SYSTEM delay

ü A valid triggering event occurs in the PATIENT at t1. At t2 the ALARM SYSTEM determines that an ALARM CONDITION exists.

û NOTE In this example, the ALARM LIMIT is less than 85, not less than or equal to 85.

אין כמו הערה זו כדי להעיד על כך שסעיף זה של התקן זה כתוב במונחים מתמטיים-הנדסיים במקום במונחים של סיכון החולה.

The ALARM CONDITION DELAY is t2 – t1. This delay is due to the ALARM SYSTEM processing and averaging.

The ALARM SIGNAL GENERATION DELAY is t3 – t2. This delay is attributed to the ALARM SYSTEM strategy and the communication time to the ALARM SYSTEM generating device or DISTRIBUTED ALARM SYSTEM (e.g. PATIENT monitor or central station).

At t3 the ALARM SYSTEM begins to generate ALARM SIGNALS.

Thus, the overall ALARM SYSTEM delay time is t3 – t1.