## 1 Introduction  
### State of the Art  
For decades, hospital architecture design has been governed by the parameters of energy efficiency, effectiveness of use, and the promotion of patient well-being and health [1, 2]. In critical environments such as the intensive care unit (ICU), it becomes particularly important for architectural design to create healthy environments, enabling adequate visual and work performance. One of the key factors that the built environment must promote is the appropriate sleep cycle of patients. Various studies have highlighted that poor sleep quality in ICU patients [3, 4] can have consequences for the recovery process [5]. Low sleep quality appears to influence metabolic, immune, respiratory, cardiovascular, and neurological systems [3, 6, 7, 8, 9, 10, 11], as well as episodes of delirium and cognitive impairment [12, 13]. While sleep disorders are a complex and multifactorial problem, with factors such as the impact of diseases, anxiety, medication, and possible interventions playing a role [14], environmental factors also have a significant impact. These environmental factors, dependent on good architectural design, include noise and particularly, lighting evolution throughout the day and night [5; 11; 12; 13; 15; 16]. In this way, excessive noise levels in ICU environments have been shown to disrupt sleep, increase stress, and negatively impact patient outcomes. In addition, these high noise values can also contribute to hypertension, delayed wound healing, and even prolonged hospital stays [17]. In the case of lighting in hospital environments, at the end of the 19 th century, it was already recognized that light and day-night rhythms were of significant importance in the restoration of patients' health [18]. This is because the regulation of melatonin, a hormone that plays a crucial role in sleep [19], is greatly dependent on perceived light, both in its spectral composition and its luminous flux [20]. Specifically, the suppression of melatonin production in the pineal gland, known as the circadian stimulus (\(CS\)), is largely induced by exposure--for at least half an hour-- of the melanopic photoreceptors in the eye to light with a high short-wavelength spectral component, typically with a spectral peak around 460 nm, commonly referred to as \"royal blue\" light [21; 22]. This spectral composition of the light coincides with natural daylight in the early hours of the day. Therefore, proper circadian synchronization through exposure to natural light can improve sleep quality, alertness, and other biological factors [23]. However, it has been observed that the typical light spectrum in ICU environments, where patients can spend more than an average of 6 days [24], often does not enable optimal activation of melanopic photoreceptors [25; 26; 27]. Several specific studies have highlighted that it is common to find illuminance values in the ICU that are too low during the day and too high during the night [15; 28]. This can also be observed in reviews regarding the design of ICU spaces in the project phase and their impact on circadian entrainment, both in terms of electric and natural lighting [29]. These reviews recommend the introduction of cyclic lighting systems [26; 30; 31], promoting access to natural light [1], and limiting illuminance levels during sleep hours [31; 32]. In the case of using electric lighting systems, multiple studies have analyzed various lighting system proposals that promote circadian entrainment. These include cyclic systems--regulating their luminous flux throughout the day--and tunable white (TW) systems--with the ability to adjust color temperature and luminous flux. There are also biodynamic (BDL) systems--capable of regulating spectral distribution and light flux [33]. The latter systems are notable for their effective control of the resulting spectrum to match activity and time of day, according to biological needs [33].