Sleep quality in survivors of critical illness.

PURPOSE: There is limited data regarding the sleep quality in survivors of critical illness, while the time course of the sleep abnormalities observed after ICU discharge is not known. The aim of this study was to assess sleep quality and the time course of sleep abnormalities in survivors of critical illness. METHODS: Eligible survivors of critical illness without hypercapnia and hypoxemia were evaluated within 10 days (1st evaluation, n = 36) and at 6 months after hospital discharge (2nd evaluation, n = 29). At each visit, all patients underwent an overnight full polysomnography and completed health-related quality of life questionnaires (HRQL). Lung function and electro-diagnostic tests (ED) were performed in 24 and 11 patients, respectively. RESULTS: At 1st evaluation, sleep quality and HRQL were poor. Sleep was characterised by high percentages of N1, low of N3 and REM stages, and high apnea-hypopnea index (AHI, events/h). Twenty-two out of 36 patients (61%) exhibited AHI ≥ 15 (21 obstructive, 1 central). None of the patients' characteristics, including HRQL and lung function, predicted the occurrence of AHI ≥ 15. At 6 months, although sleep quality remained poor (high percentages of N1 and low of REM), sleep architecture had improved as indicated by the significant increase in N3 [4.2% (0-12.5) vs. 9.8% (3.0-20.4)] and decrease in AHI [21.5 (6.5-29.4) vs. 12.8 (4.7-20.4)]. HRQL improved slightly but significantly at 6 months. Neither the changes in HRQL nor in lung function tests were related to these of sleep architecture. Six out of eight patients with abnormal ED at 1st evaluation continued to exhibit abnormal results at 6 months. CONCLUSIONS: Survivors of critical illness exhibited a high prevalence of obstructive sleep-disordered breathing and poor sleep architecture at hospital discharge, which slightly improved 6 months later, indicating that reversible factors are partly responsible for these abnormalities.

Potentially harmful effects of inspiratory synchronization during pressure preset ventilation.

PURPOSE: Pressure preset ventilation (PPV) modes with set inspiratory time can be classified according to their ability to synchronize pressure delivery with patient's inspiratory efforts (i-synchronization). Non-i-synchronized (like airway pressure release ventilation, APRV), partially i-synchronized (like biphasic airway pressure), and fully i-synchronized modes (like assist-pressure control) can be distinguished. Under identical ventilatory settings across PPV modes, the degree of i-synchronization may affect tidal volume (VT), transpulmonary pressure (PTP), and their variability. We performed bench and clinical studies. METHODS: In the bench study, all the PPV modes of five ventilators were tested with an active lung simulator. Spontaneous efforts of -10 cmH2O at rates of 20 and 30 breaths/min were simulated. Ventilator settings were high pressure 30 cmH2O, positive end-expiratory pressure (PEEP) 15 cmH2O, frequency 15 breaths/min, and inspiratory to expiratory ratios (I:E) 1:3 and 3:1. In the clinical studies, data from eight intubated patients suffering from acute respiratory distress syndrome (ARDS) and ventilated with APRV were compared to the bench tests. In four additional ARDS patients, each of the PPV modes was compared. RESULTS: As the degree of i-synchronization among the different PPV modes increased, mean VT and PTP swings markedly increased while breathing variability decreased. This was consistent with clinical comparison in four ARDS patients. Observational results in eight ARDS patients show low VT and a high variability with APRV. CONCLUSION: Despite identical ventilator settings, the different PPV modes lead to substantial differences in VT, PTP, and breathing variability in the presence spontaneous efforts. Clinicians should be aware of the possible harmful effects of i-synchronization especially when high VT is undesirable.

Recent advances in interfaces for non-invasive ventilation: from bench studies to practical issues.

The interface is the defining element of non-invasive ventilation (NIV). Nowadays different types of interfaces, which differ in terms of shape, mechanical properties and comfort, are available, and their choice and fitting is a key element of NIV success. In the last decade, larger masks covering the entire face and specifically designed helmets have been developed for delivering NIV, theoretically improving comfort and patient tolerance. Recent studies have shown that, despite marked heterogeneity in mask internal volume and compliance, the dynamic dead space and, above all, the clinical efficacy of different masks is on average very similar. Thus, with the exception of the nasal mask and the mouthpiece, a variety of interfaces for NIV can be used in the acute care setting. However, prevention and monitoring of interfaces related side-effects and evaluation of patient tolerance are crucial to avoid NIV failure. To optimize effectiveness and costs, an interface strategy for NIV in acute respiratory failure could be convenient in clinical practice.