**3. Vigilance and attention in patients with Sleep Apnea Syndrome**

#### **3.1 State of research (Fig. 4)**

Attention underlies performance of intellectual and everyday tasks. Depending on requirement character, novelty, intensity and level of activity, different components of attention are required.

The central nervous system activation (*alertness*) reflects the degree of general alertness and represents a kind of basic activation and general responsiveness. It is unconscious, and affected by the autonomic nervous system and the physiological diurnal state of the organism. Two variants of the central nervous system activation are described. The *tonic activation* is the stable level of attention over a long period of time. A disruption in tonic activation is manifested by a slowing of cognitive and motor processes. The tonic activation can be measured with the Multiple Sleep Latency Test *MSLT* (Carskadon & Dement 1977, Carskadon et al. 1986), the Maintenance of Wakefulness Test *MWT* (Poceta et al. 1992) or the

Although the MSLT and MWT have been used frequently, in many studies was found evidence that the reliability and validity of the procedures are unsatisfactory. In addition, the two test methods don't correspond to any real life situation (Johns, 2000). Even if it is objective and standardized measuring instruments, have been repeatedly confirmed weaknesses in the implementing objectivity of the individual tests as well as their generalization ability (Danker-Hopfe et al. 2006). John's criticism is that the reliability and validity verification of MWT and MSLT were not gone in any way according to objective and standardized criteria. The ESS compared to the MSLT and MWT has good reliability and validation criteria, sensitivity and specificity measures. Its only drawback lies in the fact that the subjective assessments are based on individual perception and trust and the honesty

Johns (2000) emphasizes the need to find an objective test, such as the ESS is valid and able to quantify the alertness in various everyday situations. Such a test would represent a true gold standard. Result of this strong criticism and of the clinical relevance of developing a new measuring method, Rühle et al. (2005) analyzed the effect sizes of the ESS. They pursued the goal, to detect the daytime sleepiness of life situation as objective, reliable and valid as possible. The analysis of the ESS and its implications led to the experimental derivation, design and construction of the *Reading test* (pilot study: Rühle et al. 2007, main

Both the pilot study and the main study, the alertness impairments in OSAS patients with the reading activity, a simple spiritual activity were operationalized. In contrast to the MSLT and MWT daytime sleepiness was not measured in an experimental laboratory situation, but in an everyday clinical situation. The *Reading Test* is suitable for the determination of daytime sleepiness, because it probably produces a low level of attention. The reading activity will be documented and monitored continuously by EOG. Therefore, the nonreading phases can be observed, e.g. at the beginning of sleep, movement and looking around of the patient. In addition, the behaviour spectrum of patients are also detected in the EMG, as unwanted movements (facial grimacing and head movements), which can

Attention underlies performance of intellectual and everyday tasks. Depending on requirement character, novelty, intensity and level of activity, different components of

The central nervous system activation (*alertness*) reflects the degree of general alertness and represents a kind of basic activation and general responsiveness. It is unconscious, and affected by the autonomic nervous system and the physiological diurnal state of the organism. Two variants of the central nervous system activation are described. The *tonic activation* is the stable level of attention over a long period of time. A disruption in tonic activation is manifested by a slowing of cognitive and motor processes. The tonic activation can be measured with the Multiple Sleep Latency Test *MSLT* (Carskadon & Dement 1977, Carskadon et al. 1986), the Maintenance of Wakefulness Test *MWT* (Poceta et al. 1992) or the

prevent sleep. This aspect would be particularly relevant in experiments.

**3. Vigilance and attention in patients with Sleep Apnea Syndrome** 

**2.8.3 Summary and outlook** 

of the patient.

study: Erle et al. 2009).

**2.8.4 Conclusion of the reading test** 

**3.1 State of research (Fig. 4)** 

attention are required.

Pupillography (company Amtech, Weinheim, Wilhelm et al. 1998, 2001). A newer method to quantify the tonic activation is the *Reading test* (Erle et al. 2009).

The *phasic activation* is manifested in stimulus situations, in which short-term increases of the activation in the resting state are required. Limitations of the phasic activation can result in delayed reaction rapidities up to omitted reactions. The phasic activation may be tested for example in the kind of reaction time measurements, e.g. with the test battery of Zimmermann and Fimm (TAP / 1994), event-related EEG deductions or on the basis of the heartbeat rate or skin conductivity.

Fig. 4. Proposed relationship between sleep quality and sleepiness-related restrictions during the day

*Sustained attention* is the ability to direct attention over a long period to one or more randomly occurring stimuli and to respond to minimal stimuli changes (Davies, Jones and Taylor 1984). *Vigilance*, which is a variant of sustained attention, requires long-term attention performance in minimally and irregularly occurring stimuli. As reliable indicators false (i.e. incorrectly or delayed) and omitted responses as well as reaction times can be measured as an expression of sustained attention and vigilance. Furthermore, particularly in the field of sleep medicine the *Clock Test* by Mackworth (1948), modified by Quatember and Maly (Sturm und Büssing, 1993), and the *vigilance test* "*Carda*" by Randerath et al. (1997, 2000) and Gerdesmeyer et al. (1997) and the *sustained attention test* "*Carsim*" by Büttner et al. (2000a/b, 2001) have been used to test the vigilance and sustained attention.

*Selective attention* is also the ability to focus on specific relevant stimuli and to suppress simultaneously occurring irrelevant stimuli. The kind of attention function can be investigated by choice-reaction tasks or orienting responses, e.g. based on the subtest "*Selective attention*" to the *TAP*1.

*Divided attention* describes the capacity for serial and parallel information processing and the flexibility of selecting to switch back and forth at least two different sources of information (Sturm and Zimmermann 2000). Relevant stimuli can each occur in one or two sources of information to which the person have to respond as quickly as possible. Divided attention can be measured with dual-task activities (e.g. using the subtest "*Divided attention*" of the *TAP*).

As with many sleep-related disorders, such as hypersomnias and dyssomnias, the victims suffer from, in addition to their nocturnal symptoms, increased daytime sleepiness and the tendency to fall asleep (Büttner et al. 2004b). These difficulties are in turn associated with attention-related deficits and limitations (including Gerdesmeyer et al. 1997, Müller et al. 1997, Randerath et al. 1997, 1998, Weeß 1997, Weeß et al. 1998a/b, Büttner et al. 2003b, 2004b).

<sup>1</sup> TAP = German: **T**estbatterie zur **A**ufmerksamkeits**p**rüfung; English translation: Test battery for Attentional Performance

The Effects of Sleep-Related Breathing Disorders on Waking Performance 131

The Ambrock vigilance test "Carda" by Randerath et al. (1997) recorded the vigilance performance over a period of 30 minutes. The patient sits in a semi-darkened room in front of a black computer screen and look at the picture of a street with a running road median and the lateral lane boundaries. They are asked to respond within one second of a with a computer keyboard button on stimuli (white flashing rectangles), which occur in time and space for 20 ms randomly. In each 10-minute interval 100 stimuli appearing, in the total period 300 will be shown. After a brief instruction and a short practice the test is started via

Fig. 5. Driving Simulator *Carda* by Gerdesmeyer et al. 1997, Randerath et al. 1997, 1998

Measurements for the reliability and validity are pending.

**3.3 Sustained attention test** *Carsim* **(Fig. 6)** 

Right and false reactions are calculated in relation to the presented events (in percentage), the latter being registered as an error. The unfounded (delayed) reactions are given in absolute numbers. The age-and gender-independent cut-off value for the error is 5.75% (SD = 11.3%) after a standardization study with healthy volunteers of Randerath and colleagues (2000). For the unfounded responses and response times are currently no cut-off values.

The Ambrock sustained attention test "Carsim" by Büttner et al. (2000a/b, 2001) recorded its performance over a period of 30 minutes. The image with a road median and lane boundary is simulated polychrome. On the right side of the road obstacles (in the kind of no entry signs) can be presented, which are only briefly visible in each case (e.g. for 200 ms). Their appearance is timely random, in which a fixed number of events can be adjusted with a 5-minute section. The patient now has the task to keep up with the help of

**3.2 Vigilance test** *Carda* **(Fig. 5)** 

a menu driven DOS computer program.

**Evaluation** 

Consequence of this reduced performance include an increased risk of accidents at work and in traffic and thus a higher socio-medical risk (e.g. Bradley et al. 1985, Podszus et al. In 1986, He et al. 1988, Mitler et al. 1988, Lamphere et al. 1989, Roehrs et al. 1989, Bédard et al. 1991, Kribbs et al. 1993a/b, Gerdesmeyer et al. 1997, Randerath et al. 1997, 1998, Weeß 1997, Weeß et al. 1998a/b, Büttner et al. 2000a/b, Büttner 2001).

To explore the difficult relationship between sleep, daytime fatigue and physical and mental performance is based mainly on three conditions (Johnson 1982, Weeß 1997, Weeß et al. 1998a/b). Thus, the three mentioned above parameters will be affecting through a variety of other variables, for example by the motivation of the healthy subjects or patients, or the daily and weekly rhythm. Furthermore, daytime fatigue and performance as well as their underlying attention-related processes are complex constructs. This analysis will be complicated also by the lack of standard term uses in the medical and psychological literature (Johnson 1982, Weeß 1997, Weeß et al. 1998a/b).

There are, both in the medical and especially in sleep medicine research, a number of different research approaches and definitions regarding the attention and attention-driven processes (Rützel 1977, Rapp 1982, Brickenkamp & Karl 1986, Posner & Rafal, 1987, Säring 1988, Posner & Petersen, 1990, Posner 1995), which accentuate different characteristics and aspects of the daytime performance (James 1890, Head 1926, Mackworth JF 1956, Mackworth N 1958, Schmidtke 1965, Norman 1973, Bäumler 1974, Harnatt 1975, Rützel 1977, Brickenkamp & Karl 1986, Posner & Rafal, 1987, Säring 1988, Posner & Petersen, 1990, Rollet 1993, Schmöttke & Wiedl 1993).

Currently, in the sleep medicine literature, mainly the concept of Posner and Rafal (1987) will be used (Keller et al. 1993, Weeß 1997, Weeß et al. 1998a/b).

Also problematic are the very diverse conducted empirical analysis of attention and its components and the varying quality of the validation test procedures and instruments. Thus, inter alia vigilance covered by inappropriate (Stephan et al. 1991), too complex (Bédard et al. 1993) or timely too short (Bédard et al. 1991, 1993) test requirements (Weeß 1997, Weeß et al. 1998a/b).

To capture the tendency to fall asleep in Obstructive Sleep Apnea is conducted usually by the MSLT (Multiple Sleep Latency Test) (Poceta et al. 1992), because it correlated most strongly with the subjective state/mood of OSAS. However, through it the attention and vigilance will be detected only indirectly (Denzel et al. 1993).

For this purpose researched Denzel et al. (1993) for more suitable methods and examined in this context, two computerized neuropsychological test procedures, a vigilance and a attention test, in which the attention test was checked under three experimental conditions (visual, auditory, combined). In both the dual-task-task as well as the vigilance testing was found significant differences before and after nCPAP therapy (Denzel et al. 1993).

Similar results – i.e. a significant improvement of vigilance under nCPAP – were found already by Kesper-Schwarzenberger et al. (1991), Cassel et al. (1991) and George et al. (1997; *DADT*)

As important criteria was found the standardization of experimental conditions (Horn et al. 1983, Denzel et al. 1993) and the design of the experimental setup (the author). Thus showed, inter alia, that an immediate auditory feedback about the correctness improved the occurred reactions improved the motivation of the patients, thereby obscuring the effects of sleep deprivation and their resulting poor performance (Wilkinson 1961, Steyvers & Gaillard 1993, Weeß 1997, Weeß et al. 1998a/b).
