Lecture 5 'Control'

Question 1

The Mercury space capsule control panel controls three types of movements, what are they?

Answer 1

roll = {cartwheel}
pitch = {fall forward}
yaw = {turn on feet}

Question 2

Under pressure, what kinds of mappings or motions do people revert to in terms of control?

Answer 2

Those which are more naturally compatible

Question 3

What kind of control violations underlie many accidents and incidents with equipment?

Answer 3

violations of stimulus response (SR) compatibility

Question 4

> a) Out of the following control knobs, which did Bradley (1954) find to be the rated as the most natural (SR compatible) and linked to the least amount of starting/setting errors?
b) Which was rated last?

A - direct drive, left-right increase, clockwise=decrease

B - direct drive, right-left increase, clockwise=increase

C - reversed drive, left-right increase, clockwise=increase

D - reversed drive, right-left increase, clockwise=decrease

Answer 4

A - direct drive; left>right, clockwise=decreases

D. = last

Question 5

According to McCormick and Sanders, Location/Spatial compatibility is the relationship between what two things?

Answer 5

Physical arrangement in a space of controls + associated displays

Question 6

The target zone for the depth of anesthesia is between __ -__

Answer 6

60-40

Question 7

Awareness under anesthesia affects ___% of patients

Answer 7

0.1-0.2%

Question 8

According to Myles et al (2004), the Bispectral Index (BIS) monitoring system _______ the risk of patients at high-risk of awareness under anesthesia.

Was this supported by Avidan (2008)?

Answer 8

reduced

No - did not replicate findings

Question 9

Describe the Utah drug display as outlined in Cooke & Durso?

Answer 9

> Utah drug display shows =

a) current/past drug dosing
b) predicted pharmacokinetics
c) combined effects on levels of sedation, analgesia and neuromuscular blockade

Question 10

(Q. 29) A drug takes several minutes to reach its full effect even after it starts to hit receptor sites in the
brain. This is an example of which phenomenon in closed-loop control?

Answer 10

Lag

Question 11

Answer the following related to closed-loop control;

Delay = _______
Lag = _______
Gain = _______
Order of control = _______

Answer 11

Delay = time before response starts

Lag = time for response to get to full strength

Gain = multiplier of input (big/small reaction)

Order of control = position / velocity / acceleration

Question 12

What is the main difference between closed-loop and open-loop controls?

Answer 12

open-loop controls do not have feedback on which to base corrections; you have to “know” how it will respond in advance (“ballistic”)

Question 13

(Q. 30) I move a joystick to 2 cm to the left. The speed of a dot on my screen start moving to the left,
building up speed until it reaches a relatively low constant speed. This is an example of what kind
of control dynamics?

Answer 13

A 1st order system with a lag and low gain

Question 14

Describe a 0-order control?

Answer 14

identical movements as control (e.g. like a mouse moving on the screen the same way/speed you move it in your hand)

Question 15

Describe a 1st -order control?

Answer 15

builds up velocity/speed GRADUALLY then stays at a constant speed

Question 16

Describe a 2nd -order control?

Answer 16

accelerates quickly, builds speed and keeps getting faster

Question 17

(Q. 28) When controlling a process such as depth of anesthesia, what is the input signal that the
controller (human or machine) responds to?

a. The desired output.
b. The error between actual and desired output.
c. The actual output.
d. The brain’s response.

Answer 17

b. The (+/-) error between actual and desired output

Question 18

Liu et al (2006) showed that a proportional differential controller (PD) does a _________ job than an manual human controller (the anesthetist). What does it do?

Answer 18

better

Try to nullify the BIS error without making response unstable or making it sluggish

> BIS stays between 40-60
Patients wake up faster
Less overall control error

Question 19

Drug “effect-site delay” means what?

Answer 19

the DELAY and LAG in how long it takes a drug (e.g. propofol) to have its full pharmacological effect

Question 20

(Q. 34) What does the drug display for anesthesia (Syroid et al. 2002; Drews et al. 2006) actually show?

Answer 20

A graphical model of a patient’s physiological response to the anesthesia drugs over time.

Question 21

When tested, the drug display resulted in what three positive effects?

Answer 21

• patients woke up earlier
• anesthetists = lower mental workload
• anesthetists = feel better performance

Question 22

According to an ICU clinical information systems (CIS) evaluation of displays, answer the following.

Nurses detected change faster with which displays? Which of these was better?

Doctors agreed more closely about which systems had failed with which display?

Doctors agreed more closely about diagnoses with which display?

Answer 22

Nurses detected change faster with = PAPER and ELECTRONIC prototypes (compared to traditional chart)
> ELECTRONIC = better

Doctors agreed about failed system = ELECTRONIC (vs. paper vs. traditional)

Doctors agreed about diagnoses = PAPER (vs. electronic vs. traditional)

Question 23

(Q. 35) Consider the connection between human trust and automated control of anesthesia with a PID
controller. What must the anesthetist trust?

Answer 23

> Measures of depth of anaesthesia

> PID control dynamics