The quality of sleep is impaired in critically ill patients   . Sleep disorders are likely to be affected by endocrine function modulation  , impaired immunity, cognitive function, pain  , as well as discomfort   . This is an issue that cannot be ignored by intensive care unit (ICU) medical teams providing support to critically ill patients.
It has been found that both environmental and physiological/psychological factors contribute to the development of sleep disorders in the ICU  . Consequently, in addition to creating a night-time environment inside the room that is dark and as quiet as possible, we are providing medical care that includes interventions focusing on relief of pain and anxiety, encouraging sleep with sleep-inducing drugs, and increasing the depth of sedation to a level higher than that used during the day, along with other nursing practices. However, it is true that numerous critically ill patients complain of lack of sleep.
Invasive respiratory therapy might cause sleep disturbance in the ICU. In contrast, noninvasive positive pressure ventilation (NPPV) and nasal high-flow oxygen therapy (NHF) are easier to introduce than intubation and are often less invasive and do not require analgesia and sedation. Therefore, patients treated with NPPV and NHF may be able to communicate verbally and sometimes eat and drink. Treatment with NPPV and NHF has been increasing in recent years as a form of respiratory management along with artificial-respiration management with conventional tracheal intubation in patients with acute respiratory failure. Conversely, critically ill patients who are treated with NPPV or NHF encounter several issues that may interfere with sleep, such as discomfort  . Some studies have suggested that insomnia during treatment with NPPV may lead to NPPV discontinuation  . Therefore, it is important to practice care for nurses who support the lifestyle and psychological wellbeing of critically ill patients.
There are several studies on the sleep conditions and sleep inhibitors in patients with tracheal intubation and oxygen mask/nasal cannula    . However, few studies have quantitatively and qualitatively examined the sleep conditions among patients treated with NPPV or NHF.
The purpose of this case study was to clarify the sleep conditions of patients receiving NPPV and NHF in the ICU and to examine the ideal manner of nursing support.
2.1. Data Collection Period and Facilities
This study was conducted between August 2014 and February 2015. The study took place in the ICU of a university hospital with 20 beds and a nurse to patient ratio of 1 to 2. ‘A curtain or sliding door could be used to separate the patient’s room from those of other patients or the ICU hallway.
1) Selection criteria
a) Adult patients (−1 ≤ RASS ≤ 1) who remained in the ICU for at least 1 night (9 pm to 9 am) and were capable of communicating.
b) Patients who were treated with NPPV or NHF for the first time
2) Exclusion criteria
a) Patients after tracheal intubation in the ICU
b) The primary disease was cerebrovascular or neuromuscular
c) Patients who were assessed as having delirium based on the Confusion Assessment Method for the ICU  at the start of the study
d) Patients who had a psychiatric disorder and were receiving drug therapy for their condition
e) Patients with markedly poor circulatory dynamics and respiratory status
f) Patients continuously receiving analgesics, sedatives, and sleep introducers (drugs that may strongly affect the electroencephalogram (EEG))
2.3. Data Collection
1) Data collection with polysomnography (PSG)
The purpose of data collection with PSG was to determine the sleep stages and to accurately measure the presence and degree of arousal responses. Therefore, the three electrophysiological indicators essential for objective sleep measurements, EEG, electro-oculogram (EOG), and electromyogram (EMG), were measured. Generally, in PSG, information on oral/nasal respiration, respiratory movements of the chest and abdomen, percutaneous arterial blood oxygen saturation, electrocardiogram, tibialis anterior EMG, and position are simultaneously collected; however, taking into consideration the burden on the subjects, it was decided that these parameters would not be measured for the present study.
An Alice PDx (Philips Respironics, Murrysville, PA; medical equipment certification number: 22100BZX01027000), which is compact and can be used in the ICU, was used for measurements. Installation of the equipment was conducted by one project manager who had taken a lecture from a full-time laboratory technician from the Philips Respironics sleep center who was familiar with the standard method of the international EEG society (10 - 20 electrode system).
Subjects were at rest in a normal bed in the ICU. In the present study, “Lights out (in bed)” was defined as “lowering the lights in the ICU at approximately 9 pm” and “waking up” was defined as “when the patients naturally woke up in the morning” or “the beginning of medical care at approximately 7 am.”
In accordance with the international 10 - 20 electrode system, the EEG installation sites for A1 and A2 were the earlobes (reference electrodes) attached to C3 and O2, and the body ground was placed on the forehead  . EOG electrodes were attached in two places: 1 cm below the lateral orbital rim and contralaterally 1 cm above the lateral orbital rim of the eye. EMG electrodes were attached at the left and right sides of the jaw  .
2) Data collection by interview
A semi-structured interview was conducted by a researcher with a major theme such as “Sleep status during oxygen therapy (NPPV or NHF)” “How does oxygen therapy (NPPV or NHF) interfere with sleep?” and was able to add questions as appropriate for each patient. The interview took place in a quiet room where privacy could be assured and was recorded using a digital voice recorder with the permission of the subjects. The interview time was scheduled to be no more than 20 minutes per session, taking into account the burden on the subjects.
3) Collection of data from medical records
Following the completion of data collection with PSG, the following information was collected.
Age, the Acute Physiology and Chronic Health Evaluation II score  , the medical history, the treatment details, the nursing care (gargling, suction, listening to breathing sounds, location confirmation of routes, and clothing changes), and the sleep environment.
2.4. Data Analysis
Data analysis was performed by a laboratory technician at the Philips Respironics Sleep Center. Without access to subject-identifying information, sleep stage analysis was conducted using the EEG, EOG, and EMG data. The sleep stage analysis was performed in accordance with the classifications proposed by the American Academy of Sleep Medicine in 2007  .
2) Semi-structured interview
The analysis was performed qualitatively with reference to the Modified Ground Theory Approach (M-GTA)  . M-GTA is a method of qualitative research that builds concepts based on data pertaining to phenomena. The analysis mainly comprises “constant comparative analysis,” “theoretical sampling,” and “theoretical saturation.” We followed the concept of comparative analysis in limited data.
As a specific analysis procedure, the entire dataset was read and we focused on the sections related to the analysis theme: “Sleep status and sleep effects of patients receiving NPPV or NHF.” “In the M-GTA, the minimum analytical unit is the concept. Each concept is created from several pieces of data known as variations. Variations are collected along the analysis theme”  . Moreover, we considered the interrelationships between the concepts and we created categories.
M-GTA usually collects and analyzes multiple cases. However, in this study, a subset of the M-GTA methods were utilized to more clearly present patient experiences.
3. Ethical Considerations
This study was conducted with approval from the ethics review committee of the research facility. The researchers explained the objectives of the study, freedom of withdrawal, and confidentiality of data content to the patients. It was also explained that the data collection would immediately stop if the patients became uncomfortable with the electrodes or if discomfort occurred during the data collection in the ICU. In addition, we took care to avoid burdening the patients physically and mentally during the interviews.
4.1. Summary of Subject Characteristics
The study subjects were two male patients admitted to the ICU for medical treatment (Table 1). In addition, the agitation level was Richmond Agitation-Sedation Scale, 0 in both patients.
4.2. Sleep Status Based on PSG
The hypnogram (including awakening frequency/time) of the subjects and the time-dependent nursing care providedare illustrated in Figure 1 and Figure 2. The test data for night sleep PSG are shown in Table 2. The total sleep time of the subjects was 6 to 8 hours, and N1 was 28% to 34% and N2 was 57% to 62%, whereas N3 (0% to 0.6%) and REM (8%) were almost absent.
Frequent awakening was observed up to 12 am in the patient treated with NPPV (Subject A; Figure 1). Between 12 am and 6 am, fragmented sleep was observed at the timing of nursing intervention. In the patient treated with NHF (Subject B; Figure 2), relatively long fragmented sleep was observed between 11 pm and 4 am at the timing of nursing intervention. In addition, it was found that the patient treated with NPPV had a higher frequency of awakening in 1 hour than the patient treated with NHF.
4.3. Sleep Status as Assessed through the Interviews
The results of the interviews with the two patients are presented in Table 3 and Table 4. Based on our analysis, in subject A (NPPV), three categories were created from eight concepts. In subject B (NHF), three categories were created from five concepts. Both patients treated with NPPV and NHF experienced discomfort associated with the equipment (e.g., the nasal cannula or the respiratory circuit) and with the air pressure, as well as insomnia due to the perceived discomfort.
The study showed that the sleep conditions in the examined patients treated with NPPV or NHF were markedly impaired, with a significant decrease in deep sleep (N3), and the presence of shallow sleep (N1 + N2) accounted for approximately 91% of sleep structure. The patients’ sleep patterns varied greatly from those of healthy individuals. Moreover, these results suggest that, in addition to experiencing extremely fragmented sleep, sleep in these patients was more likely to be interrupted by nursing interventions, such as during auscultation of breath sounds. Furthermore, it was revealed that “anxiety or discomfort associated with the mask or air pressure” in the patient treated with NPPV and “discomfort associated with the nasal cannula or NHF circuit” in the patient treated with NHF could have been the primary causes of disrupted sleep. Thus, in this study, we were able to provide information regarding the sleep disorders and their probable causes in patients treated with NPPV or NHF.
The sleep structure of the patients treated with NPPV or NHF presented in this study was similar to that of patients treated with invasive ventilation using sedatives and in oxygen mask/nasal cannula   . However, it was found that the frequency of awakening in an hour in the patient treated with NPPV, at 34.5 times, was higher than that reported by previous studies (frequency of awakening in 1 hour 27 times on average)  including patients treated with invasive ventilation and oxygen mask/nasal cannula. In contrast, the frequency of awakening
Figure 1. Hypnogram of the patient treated with NPPV (Subject A) and nursing care. W: wake, R: REM sleep, N1: nonREM sleep stage 1, N2: nonREM sleep stage 2, N3: nonREM sleep stage 3.
Figure 2. Hypnogram of the patient treated with NHF (Subject B) and nursing care. W: wake, R: REM sleep, N1: nonREM sleep stage 1, N2: nonREM sleep stage 2, N3: nonREM sleep stage 3.
Table 1. Participant characteristics.
APACHE: Acute Physiologic Assessment and Chronic Health Evaluation  , NPPV: noninvasive positive pressure ventilation, NHF: nasal high-flow oxygen therapy.
Table 2. Results of polysomnography.
N1: non-REM sleep stage 1, N2: nonREM sleep stage 2, N3: NonREM sleep stage 3, NPPV: noninvasive positive pressure ventilation, NHF: nasal high-flow oxygen therapy, Arousal index was defined as the number of arousals per hour during the Total sleep time (TST).
Table 3. Sleep status and sleep inhibitory factors of the patient treated with noninvasive positive pressure ventilation (NPPV).
Table 4. Sleep status and sleep inhibitory factors of the patient treated with nasal high-flow oxygen therapy (NHF).
in an hour in the patient treated with NHF, at 28.7 times, was found to be similar to that previously reported. As a reason for this, a qualitative study showed that patients treated with NPPV were more uncomfortable and anxious than patients treated with NHF. This frequent arousal may lead to insomnia.
Based on the above, we consider nursing care for promoting sleep in patients treated with NPPV or NHF pertinent to the following two dimensions.
1) Nursing support for insomnia according to discomfort.
Both patients treated with NPPV and NHF may experience “discomfort due to difficulty in mobility” as indicated by the qualitative results. Medical teams including nurses need to be aware that patients treated with NPPV or NHF have difficulty moving and to properly explain to patients the extent of possible movement. This can help relieve patient discomfort and provide nursing support for sleep promotion.
In addition, in patients treated with NPPV, the respiratory alarm sounds when the mask or the respiratory circuit comes off, so we can respond quickly; for instance, to reposition them. In contrast, because the NHF does not have an alarm function, and therefore the medical personnel cannot be immediately alerted of abnormal respiratory events. Therefore, we need to convey the importance and necessity of the oxygen therapy to the patient. By doing this, we may be able to support the patient’s willingness to retain the equipment in place, even though NPPV and NHF are unpleasant   . This can promote safety and alleviate anxiety and thus promote sleep.
2) Nursing support for fragmented sleep
In this study, as in other studies, it was suggested that nursing interventions and the ICU environment may result in fragmented sleep   . Therefore, nursing care should be carried out for patients treated with NPPV and NHF, as well as in the Pain, Agitation and Delirium guidelines  , with the aim of minimizing disturbance during the night to maintain the patient’s sleep cycle to the greatest possible extent.
Finally, sleep disturbances, including fragmented sleep, may be a risk factor for delirium  . Furthermore, delirium is a risk factor for post intensive care syndrome  . Therefore, improving sleep disorders, including fragmented sleep, is an important nursing-support consideration that can contribute to the long-term prognosis and improvement of health-related quality of life starting at the ICU, and it is necessary to continue research in patients treated with NPPV or NHF.
There are several limitations in this study. First, we only studied one patient treated with NPPV and one with NHF. Which may have resulted in selection bias. In addition, from the medical records, we collected data, such as nursing care and alarm sounds, that were directly concerning these patients. However, there is a possibility that the records were not sufficiently documented and there may be information bias. In the future, it will be necessary to conduct prospective data collection and to increase the number of subjects in order to advance nursing care related to sleep deprivation and sleep promotion. However, we believe that this case study provided important information regarding the sleeping conditions of patients treated with NPPV or NHF, as we used PSG, which is the gold standard for sleep examination.
Patients treated with NPPV or NHF demonstrated a noticeable reduction in deep sleep, as most of their sleep was shallow. Their sleep patterns varied greatly from those of healthy individuals. These results suggest that, in addition to experiencing extremely fragmented sleep, sleep in these patients was more likely to be interrupted by nursing interventions, such as during auscultation of breath sounds.
Furthermore, it was revealed that “anxiety or discomfort that accompanies the mask or air pressure” in patients treated with NPPV and “discomfort that accompanies the nasal cannula or NHF circuit” in patients treated with NHF may be primary causes of disrupted sleep. This suggests a need for nursing care aimed at improving sleep quality in patients treated with NPPV or NHF.
We would like to express our deepest appreciation to the patients and hospital officials who cooperated in this research.