Innovative ICU Solutions to Prevent and Reduce Delirium and Post–Intensive Care Unit Syndrome

Alawi Luetz, MD, PhD; Julius J. Grunow; Rudolf Mörgeli, MD; Max Rosenthal, MD, PhD; Steffen Weber-Carstens, MD, PhD; Bjoern Weiss; Claudia Spies, MD, PhD


Semin Respir Crit Care Med. 2019;40(5):673-686. 

In This Article

Sound and Acoustics

Sound and Health

At least from personal experience, most of us are familiar with the effects that sounds can exert on emotions, mood and, thus, body and psyche. Whether listening to a child's cry, a live music concert, or the sound of waves breaking on a beach, what we hear has a tremendous influence on how we feel. These effects are highly subjective, so that noise, music, and silence can be perceived as calming, frightening, stimulating, or irritating, depending on a listener's experiences, preferences, and current state of mind. Although this subjective nature creates certain challenges, it also offers opportunities to employ acoustics as an ally in the hospital setting, inducing relaxation in an otherwise unfamiliar and usually frightening situation, as well as providing a quiet and supportive environment, for convalescence.

Any unwanted, loud, or disrupting sound may be described as noise. The word "noise" is derived from the Latin "nausea" and used to describe queasiness or pain. Indeed, noise has been used for centuries to harm and weaken, inducing fear in enemy armies (e.g., Aztec death whistles), and as a method of interrogation and torture in more recent conflicts. But even in mundane situations, day-to-day exposure to noise has been linked to several adverse health outcomes, raising cortisol levels, blood pressure, pain perception, and reducing quantity, and quality of sleep.[32] But a consistent reduction in noise pollution may not only be useful in avoiding negative effects, as there may be health benefits in exposure to silence. The brain does not have a passive reaction to silence, such that the absence of sound does not lead to a halting of impulses in the auditory cortex, but rather triggers firing in a distinct auditory network,[33] evidence that the brain actively listens to silence. Exposure to silence for as little as 2 hours per day can promote neuron development in adult mice, enhancing cell development in the hippocampus, the region related to the formation of memories.[34] Alternatively, exposure to music can effect neurochemistry,[35] cardiovascular parameters,[36] reduce pain medication requirements,[37] and lead to an overall improvement in patient-reported outcomes.[38] Acoustic stimulation during sleep has been linked to enhanced slow wave activity, with subsequent improvement in sleep-dependent memory storage in older adults. Alternating music and silence can stimulate and relax individuals. In fact, 2-minute silent pauses proved far more relaxing than either "relaxing" music or a longer silence played before the experiment started.[39] These findings were irrespective of musical background, so one does not have to be a musical connoisseur to enjoy these effects.

Sound and ICU Environment

The ICU environment is notoriously prone to noise pollution, and noise is indeed one of the most commonly cited issues by survivors of critical illness.[40] Not only the baseline sound pressure levels (SPLs) are important, threshold overruns in the form of sudden peaks are also harmful. Whereas the WHO recommends no more than 35 dB of A-weighted energy equivalent (LAeq) SPL during the day and the A-weighted maximum SPL with fast constant (LAFmax) not exceeding 40 dB at night, studies show that LAeqs in most ICUs range from 60 to 90 dB.[41]

The ICU environment has evolved over the years to provide information and security. To draw staff attention to potential dangers, acoustic alarms have become commonplace. We hear syringe pumps that are running low or empty, occlusions in intravenous lines, and vital sign alarms that become progressively louder as measurements deviate from set parameters. During interventions, we can hear oxygen saturation changes or an incipient arrhythmia, and high-flow ventilation systems are a permanent source of noise. Although many of these sources cannot be easily addressed, conversations among staff are one of the most frequent causes of sound peaks ≥80 dB.[42] Staff activities were also identified as a major source of sleep disruption, with studies citing an average of over 40 interventions taking place per 12-hour shift.[43] This relentless mixture of sounds from machines, alarms, monitors, interventions, ringing telephones, conversations among staff, relatives and other patients, especially over days or weeks, all ultimately subject an already critical patient to additional stress and harm. Comfort is, therefore, a frequently sacrificed luxury in the ICU setting. However, as intensivists move away from standard sedation, the short- and long-term effects of such an environment become more apparent. Although a multimodal approach is necessary,[44] noise reduction is an essential factor in combating delirium and long-term cognitive impairment.[45,46]

Incidentally, not only patients are negatively influenced by extreme noise levels at the ICUs. Prolonged exposure to noise can negatively affect productivity and increase stress in staff. A recent study could show that the staff's job satisfaction and anxiety levels were significantly associated with noise measurements at their ICU.[47]

Attempts to implement behavioral changes to reduce noise levels are certainly necessary, but alone, they have thus far been ineffective.[48] Behavioral-based interventions may only be effective when supplemented by innovative tools, and there is a growing number of technological and architectural solutions that can aid the implementation of acoustics in the hospital setting as a prophylactic or therapeutic measure.

The use of earplugs in the ICU has been often suggested as an alternative, but, so far, there is no evidence that their use as a single intervention can reduce delirium rates.[49] Although earplugs were shown to improve sleep quality in combination with other interventions, that is, sleep masks, the same study also reported that 30% of patients in the intervention group did not tolerate the earplugs throughout the night.[50] Tolerability is indeed a significant issue in earplug studies, with nonsedated patients often report frequent dislocation, discomfort, and feelings of isolation when wearing earplugs.[50,51] This suggests that their implementation at the ICU may be limited to certain patients groups, and, as a supplement to other, more tolerable measures. To protect the patient and staff from harmful sound levels, day and night, multimodal strategies must be employed, aiming to provide patient-centered care to critically-ill patients, whether or not they are able to interact with their surroundings.

Innovations in Sound Control

Providing a quiet environment is part of care, as essential for patients as medication or sanitation. There are several interventions possibilities to achieve this goal, including optimizations in architectural design, establishing behavioral changes by improving awareness for staff and visitors, and implementing noise-canceling technology to protect the patient from noise exposure.

Designing ICU rooms with patient-centered approaches in mind has been shown to be effective in reducing noise pollution. The pilot program from Berlin's Charité University Hospital demonstrated how interventions targeting different noise categories can help to significantly reduce LAeqs and SPL overruns.[52] Pilot ICU rooms were designed with an adjacent working room (WR) that has large windows to allow for observation of the patient without entering the room (Figure 1). Reversible drawers, which can be opened from the WR and from inside the room, allow staff to prepare materials for interventions without disturbing the patients.

Figure 1.

New ICU room concept at the Charité University Hospital. A new working room (WR) is one of the key components aiming at noise reduction, (A) the WR allows for observation of the patients through a window and (B) is locates between both two-bed ICU rooms. (C) The WR provides computer working-spaces, patient monitors, and a double-catering-door system to supply the patient area with mobile units. ICU, intensive care unit.

There was a targeted use of sound-absorbing materials, avoiding sound reflective surfaces, and noise from outside was reduced by installing automatically closing doors. Noise-emitting units, such as syringe pumps and ventilation units, were strategically placed behind the patient's bed and separated by a sound protective barrier, permitting immediate access to staff while reducing noise exposure to the patient. These modifications were able to significantly reduce LAFmax values during the night by up to 10 dB and 60 dB threshold overruns from 62.0 to 26.7%.

Beyond architectural changes, cooperation from visitors and staff are required to maximize noise reduction. To implement behavioral changes and increase acceptance of technological solutions, awareness of the problem must first take place. There are innovations that can help staff and visitors recognize how loud the environment is, paving the way for cooperation in approaches involving behavioral change. Sharing baseline sound levels with staff and visitors have been shown to be effective in improving awareness, decreasing noise by an average of 10 to 15 dB.[53] A promising sound logging system was shown in Aarhus University Hospital in Denmark, although clinical data regarding its efficacy are still unavailable. Here, microphones were placed above the patient bed, so as to log sound levels from the patient's perspective. A screen outside the room shows the current noise level in relation to time. It becomes immediately apparent how loud or quiet the room is, and for how long excessive noise or quiet periods take place. Such systems enable staff to immediately recognize harmful levels, and if possible, delay nonessential interventions to prolong restorative periods of quiet. Reducing noise and providing restorative periods they have been found to be key factors in improving subjective sleep quality.[54] Such systems may improve staff acceptance and adherence to "quiet time" interventions which aim to provide a set amount of restorative periods in the ICU, although the effectiveness of such approaches are variable and inconsistent.[55]

Recent innovations in active noise-canceling headphones can improve their usefulness in the ICU setting, such as a new system developed by the University of Illinois.[56] The system involves wireless sensors that can detect soundwaves near entryways or other sound sources, relaying incoming signals to the headset at a faster speed than the soundwave travels. The headset, forewarned, can then create a specific antiwave in real-time, effectively nullifying the sound as it reaches the listener. This development could reduce wide-band white noise by over 14 dB (roughly equivalent to conventional noise-canceling earphone plus earplugs). As it is based on antisignals, it does not have to be placed in the ear canal, allowing the listener to wear the system for hours without causing discomfort. This approach allows for noise cancellation of a variety of frequencies, shielding the listener from outside noise without isolating the patient.

Several studies have attempted to use music in the ICU to improve patient comfort, and although populations and interventions were heterogeneous, music appears to be associated with a reduction of anxiety and stress.[57] Evidence is currently being gathered regarding the effectiveness of music in preventing delirium in mechanically-ventilated patients.[58] However, delivering music to patients should not contribute to noise pollution at the ICU. Noise-canceling headsets can deliver personalized music in addition to reducing noise exposure.[59] Another option is the use of directional speakers which allow for individualized music selection without excessively disturbing neighboring patients. These can be installed either in the patient's vicinity (e.g., around pillow) or through bed- or ceiling-mounted versions. Music intervention in the ICU also appears to be cost-effective in ventilated patients, not only in terms of ventilation days but also in sedation requirements.[60]

Overall, there are several options available to reduce noise pollution and improve patient outcome. Technological innovations have the potential to drive behavioral and environmental changes at the ICU, allowing for a patient-centered delivery of care aimed at preventing short- and long-term negative outcomes.