Association Between Vitamin D Status and Weaning From Prolonged Mechanical Ventilation in Survivors of Critical Illness.

BACKGROUND: In this study, we examined the association between 25-hydroxyvitamin D (25(OH)D) concentration and successful weaning from mechanical ventilation in a cohort of ICU survivors requiring prolonged mechanical ventilation. METHODS: This was a retrospective cohort study of ICU survivors admitted to a long-term acute care hospital. Demographic data were extracted from medical records, including 25(OH)D concentrations drawn on admission. Subjects were divided into 2 groups based on their 25(OH)D concentrations (deficient, < 20 ng/mL; not deficient, ≥ 20 ng/mL), and associations between 25(OH)D concentration and successful weaning were calculated. RESULTS: A total of 183 subjects were studied. A high prevalence of 25(OH)D deficiency was found (61%, 111/183). No association was found between 25(OH)D concentration and weaning from mechanical ventilation. Increased comorbidity burden (Charlson comorbidity index) was associated with decreased odds of weaning (odds ratio of 0.50, 95% CI 0.25-0.99, P = .05). CONCLUSIONS: Vitamin D deficiency is common in ICU survivors requiring prolonged mechanical ventilation. Surprisingly, there was no significant relationship between 25(OH)D concentration and successful weaning. This finding may be due to the low 25(OH)D concentrations seen in our subjects. Given what is known about vitamin D and lung function and given the low vitamin D concentrations seen in patients requiring long-term ventilatory support, interventional studies assessing the effects of 25(OH)D supplementation in these patients are needed.

Diagnosis of obstructive sleep apnea using pulse oximeter derived photoplethysmographic signals.

OBJECTIVES: Increasing awareness of the high prevalence of obstructive sleep apnea (OSA) and its impact on health in conjunction with high cost, inconvenience, and short supply of in-lab polysomnography (PSG) has led to the development of more convenient, affordable, and accessible diagnostic devices. We evaluated the reliability and accuracy of a single-channel (finger pulse-oximetry) photoplethysmography (PPG)-based device for detection of OSA (Morpheus Ox). METHODS: Among a cohort of 73 patients referred for in-laboratory evaluation of OSA, 65 were simultaneously monitored with the PPG based device while undergoing PSG. Among these, 19 had significant cardiopulmonary comorbidities. Using the PSG as the "gold standard," the sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), as well as the positive likelihood ratio (+LR) for an apnea hypopnea index (AHI)PSG > 5/h and AHIPSG > 15/h were calculated for the PPG. RESULTS: Valid results were available for 65 subjects. Mean age: 52.1 ± 14.2, Male: 52%, and BMI: 36.3 ± 9.7 kg/m(2). Positive correlation was found between PPG-derived and PSG-derived AHI (r = 0.81, p < 0.001). For AHIPSG > 5/h, sensitivity was 80%, specificity 86%, PPV 93%, NPV 68%, and +LR was 5.9. For AHIPSG > 15/h, sensitivity was 70%, specificity 91%, PPV 80%, NPV 85%, and +LR was 7.83. The corresponding areas under the receiver operator curves were 0.91 and 0.9. CONCLUSIONS: PPG-derived data compare well with simultaneous in-lab PSG in the diagnosis of suspected OSA among patients with and without cardiopulmonary comorbidities. CITATION: Romem A; Romem A; Koldobskiy D; Scharf SM. Diagnosis of obstructive sleep apnea using pulse oximeter derived photoplethysmographic signals.

Long-term acute care patients weaning from prolonged mechanical ventilation maintain circadian rhythm.

BACKGROUND: Circadian rhythm regulates many physiologic and immunologic processes. Disruption of these processes has been demonstrated in acutely ill, mechanically ventilated patients in the ICU setting. Light has not been studied as an entraining stimulus in the chronically mechanically ventilated patient. The purpose of this study was to determine the association of naturally occurring ambient light levels in a long-term acute care (LTAC) hospital with circadian rhythm in patients recovering from critical illness and requiring prolonged mechanical ventilation (PMV). METHODS: We performed a prospective observational study of 15 adult patients who were recovering from critical illness and receiving PMV and who were admitted to the ventilator weaning unit at an LTAC hospital. Demographic data were obtained from chart review. Light stimuli in each patient room were assessed using a photometer device placed at eye level. Circadian rhythm was assessed by wrist actigraphy. Cumulative data were obtained from each device for a 48-h period, averaged into 4-h intervals, and analyzed. RESULTS: Patients receiving PMV were obese (mean body mass index of 32.7 ± 10.3 kg/m2) and predominantly female (73%) and had an average age of 63.1 ± 14.3 y. Light exposure to this cohort maintained diurnal variation (P < .001) and was significantly different across time periods. Circadian rhythm, as represented by actigraphy, also maintained diurnal variation (P < .001) and was in phase with light. Linear regression of movement and time demonstrated a moderate relationship between light and actigraphy (R2 = 0.56). CONCLUSIONS: Despite requiring continued high-level care and a prolonged stay in a medical facility, patients recovering from critical illness and actively weaning from PMV maintain their circadian rhythm in phase with normal diurnal variations of light.