Effect of sleep quality on weaning from mechanical ventilation: A scoping review

A scoping review was undertaken according to the five-stage framework [20]: (1) identifying the research question; (2) identifying relevant studies; (3) study selection; (4) charting the data; and (5) collating, summarizing, and reporting the results. Reporting of the scoping review was guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Extension for Scoping Reviews checklist [21].

Is there a relationship between sleep quality, circadian rhythm, and weaning success from mechanical ventilation?

Publications meeting the following criteria were included in the scoping review: (a) date of publication between January 2000 and October 2022; (b) original study; (c) sleep quality as a factor influencing weaning from mechanical ventilation or extubation in hospitalized patients as the main topic; (d) objective and/or subjective sleep quality assessment; and (e) English language. The exclusion criteria were as follows: (a) patients younger than 18 years; (b) patients with neuromuscular diseases; (c) studies focusing only on the effect of mechanical ventilation modes on sleep quality; (d) home mechanical ventilation; and (e) reviews.

We searched four literature databases: Cumulative Index to Nursing and Allied Health Literature (CINAHL), MEDLINE, ProQuest, and ScienceDirect.

The following search terms were used: patients, in-patients, hospitalized, quality of sleep, sleep disturbance, weaning, spontaneous breathing trial, and extubation. The search terms were combined using the Boolean operators AND and OR. The same search criteria were applied to each database. We used the results of available relevant original studies to verify the objectives and provided further analysis.

A total of 252 studies were identified in the selected databases by three researchers and one librarian. Studies were reviewed independently by two researchers. Sixty-seven studies were removed as duplicates. Based on titles and abstracts, the initial screening validated 185 studies, of which 151 were excluded for lack of relevance to the topic of concern. Another 28 studies were excluded during full-text assessment as they did not meet the inclusion criteria. We checked the reference lists of the remaining six papers for possible missing studies. Studies were selected and classified according to the PRISMA flow diagram (Figure 1). We present primary data extraction from the selected six papers, including information on authors, country of origin, research design, study objectives, data processing forms, research findings, and conclusions in Tables 1 and 2. Next, we provided an analysis of the variables of interest and a synthesis of the findings.

Of the six studies analyzed, four investigated the effect of patients' sleep on their weaning from mechanical ventilation [22,23,24,25], one assessed the presence of delirium and associated circadian rhythm changes during weaning [26], and one analyzed the relationship between sleep quality and the risk of reintubation [27]. The studies comprised small patient samples (19 to 94) treated in various hospital ICUs, pulmonology centers, or specialized weaning units. The total number of all patients included in the review was 324. The studies may be considered recent as the oldest were published in 2015.

All six studies stated the time on ventilator, ranging from three to 187 days. There were differences in airway management. One study evaluated sleep in patients with a tracheostomy tube [23]; others focused on patients receiving endotracheal intubation [22,25], and two studies involved both approaches [24,26].

The studies varied in when and how sleep was assessed. All studies on subjective sleep quality assessed sleep sometime after weaning initiation [23,24]. Of the studies using objective sleep measurement techniques, two assessed sleep architecture before a planned weaning attempt [22,23], one enrolled patients after a first failed weaning attempt and monitored sleep before a subsequent weaning attempt [25], and another assessed sleep after extubation concerning the risk of re-intubation [27]. Dessap et al. [26] collected 6-sulfatoxymelatonin (6-SMT) in the first 24 hours from weaning initiation. The last study included subjective sleep assessment after completion of overnight measurements and objective sleep assessment before weaning initiation [23].

Five of the studies used objective measurement. In four studies with polysomnography (PSG), the timing of PSG recording varied (as stated in the previous paragraph) [22,23,25,27]. Of these, three studies [22,25,27] analyzed PSG recordings not only according to the conventional American Academy of Sleep Medicine (AASM) guidance [28] but also with alternative scoring systems for mechanically ventilated patients that added two new items to the AASM classification: atypical sleep, characterized by the absence of K complexes and sleep spindles in stage N2 sleep, and pathological wakefulness, characterized by altered electroencephalographic (EEG) reactivity and increased slow-wave activity [29]. Abnormal sleep patterns were present in 19% to 44% of PSG recordings. All three studies aimed to determine whether these abnormal sleep patterns affected the weaning course or increased the risk of re-intubation. Thille et al. [25] found that in a group of 45 mechanically ventilated patients, atypical sleep was associated with prolonged weaning. In contrast, a study by Dres et al. [23] failed to confirm the relationship between pathological wakefulness or atypical sleep and successful weaning attempts. The authors elaborated on the concept and used two additional EEG parameters to predict weaning success. The first was the odds ratio product (ORP), an index that evaluates sleep depth according to selected EEG parameters, ranging from 0 (very deep sleep) to 2.5 (full wakefulness). The second derived parameter was the intraclass correlation coefficient between the ORP in the right and left brain hemispheres, which compares sleep depth between the hemispheres. The likelihood of successful weaning was found to be highly correlated with the fraction of monitoring time spent in full wakefulness (ORP > 2.2). The second finding was that a poor correlation between sleep depth in the right and left hemispheres significantly predicted weaning failure. Finally, in their study of 52 patients, Thille et al. [27] explored whether atypical sleep impacted the risk of post-extubation respiratory failure or reintubation. The results showed no association with a higher risk of reintubation.

The negative impact of reduced or absent REM sleep on weaning from mechanical ventilation was documented in all studies examining REM sleep duration before extubation. Thille et al. [25,27] repeatedly described that the absence of REM sleep was associated with multiple reintubations and prolonged weaning. The authors of the other two studies, Dres et al. [22] and Huttmann et al. [23] found an association between reduced REM sleep and unsuccessful weaning.

Only one study measured sleep quality in non-sedated patients experiencing difficult weaning. Of the 19 evaluated patients, weaning was successful in 7 and unsuccessful in 12 [23]. In the other studies analyzing sleep, patients were sedated. Thille et al. [25] analyzed 45 patients on mechanical ventilation. Twenty-seven were in short weaning, and 18 were in prolonged weaning. Another study [27] assessed required for reintubation in 52 patients. Eight patients from this group had to be reintubated, and 44 were successfully extubated. The contribution of sedation to sleep changes (abnormal sleep patterns, absent or reduced REM sleep) was assessed in both studies [25,27] patients with these sleep changes were found to receive greater doses of sedation. Thus, it cannot be ruled out that sedation may also contribute to difficult weaning by impairing sleep before extubation.

Dessap et al. [26] explored the impact of the circadian rhythm on the development of delirium by measuring urinary levels of the melatonin metabolite 6-SMT during weaning (n = 70). Patients with delirium showed significantly reduced urinary excretion of the 6-SMT compared to patients without delirium.

In two studies, subjective sleep quality was subjectively assessed after liberation from mechanical ventilation, with patients retrospectively rating their sleep beforehand [23,24].

Chen et al.[24] used the validated Verran and Snyder-Halpern Sleep Scale [30]. In a group successfully weaned from ventilation within 72 hours, sleep quality was significantly better on all questionnaire items, and good sleep quality was also associated with successful weaning.

Huttmann et al. [23] assessed the quality and quantity of sleep in patients simultaneously with polysomnography (PSG) and their sleep questionnaire - containing four questions and found no difference in any items between weaning success and failure groups.

Four studies included the impact of delirium on weaning, with the assessment tool being either the Confusion Assessment Method For the Intensive Care Unit [22,26] or the Intensive Care Delirium Screening Checklist with a cut-off value of ≥ 4 [25,27]. While three studies found delirium to be associated with more difficult weaning or reintubation [22,26,27], Thille et al. [25] reported no significant difference in weaning duration between patients with and without delirium. In both of their studies [25,27] failed to confirm a relationship between the presence of delirium and atypical sleep. One study evaluated the effect of urinary excretion of 6-SMT in patients undergoing weaning [26]. Urinary 6-SMT levels were lower in patients with delirium, suggesting an association between a disrupted circadian rhythm and the presence of delirium.

Muscle weakness, a potential impediment to weaning from mechanical ventilation, was studied [25,27]. Their subanalysis found muscle weakness to be an independent factor associated with prolonged weaning and significantly more frequent in patients with atypical sleep. However, the authors do not comment on the association between atypical sleep and ICU-acquired weakness.

Disease severity was described using the scoring systems Acute Physiology and Chronic Health Evaluation II (APACHE II) or Sequential Organ Failure Assessment. Most reviewed studies found an association between disease severity and weaning failure [26,22,24,25,27]. When looking for associations between disease severity and sleep, two studies failed to confirm a relationship between the presence of atypical sleep and the severity of the underlying disease [25,27]. According to Chen et al. [24], the relationship between sleep quality and disease severity is one of the factors affecting successful weaning of patients from mechanical ventilation.

This review has several limitations: (1) different groups of patients with different severity of the underlying disease, (2) lack of differentiation of ventilation modes, (3) different methods of airway management (endotracheal tube, tracheostomy), (4) limited assessment of the effect of sedation, (5) failure to include other factors associated with the ICU environment (noise, light, nursing interventions), and (6) a small number of studies addressing the topic.