Patient-ventilator synchrony and sleep quality with proportional assist and pressure support ventilation.

OBJECTIVE: To examine patient-ventilator asynchrony and sleep quality in non-sedated critically ill patients ventilated with proportional assist ventilation with load adjustable gain factors (PAV+) and pressure support (PSV). METHODS: This was a randomized crossover physiological study conducted in an adult ICU at a tertiary hospital. Patients who exhibited patient-ventilator asynchrony on PSV were selected. Polysomnography was performed in these patients over 24 h, during which respiratory variables were continuously recorded. During the study period, each patient was randomized to receive alternating 4-h periods of PSV and PAV+ equally distributed during the day and night. Sleep architecture was analyzed manually using predetermined criteria. Patient-ventilator asynchrony was evaluated breath by breath using the flow-time and airway pressure-time waveforms. RESULTS: Fourteen patients were studied. The majority (85.7 %) had either acute exacerbation of COPD as admission diagnosis or COPD as comorbidity. During sleep, compared to PSV, PAV+ significantly reduced the patient-ventilator asynchrony events per hour of sleep [5 (1-17) vs. 40 (4-443), p = 0.02, median (25-75th interquartile range)]. Compared to PSV, PAV+ was associated with slightly but significantly greater sleep fragmentation [18.8 (13.1-33.1) versus 18.1 (7.0-22.8) events/h, p = 0.01] and less REM sleep [0.0 % (0.0-8.4) vs. 5.8 % (0.0-21.9), p = 0.02). CONCLUSIONS: PAV+ failed to improve sleep in mechanically ventilated patients despite the fact that this mode was associated with better synchrony between the patient and ventilator. These results do not support the hypothesis that patient-ventilator synchrony plays a central role in determining sleep quality in this group of patients.

Sleep during proportional-assist ventilation with load-adjustable gain factors in critically ill patients.

BACKGROUND: Proportional-assist ventilation with load-adjustable gain factors (PAV+) automatically adjusts the flow and volume assist to represent constant fractions of resistance and elastance of the respiratory system, respectively. Resistance and elastance are calculated at random intervals of 4-10 breaths, by applying a 300 ms pause maneuver at the end of selected inspirations. OBJECTIVES: To determine whether the large number of end-inspiratory occlusions during PAV+ operation influences sleep quality in critically ill patients who exhibited good patient-ventilator synchrony during pressure support (PS, baseline). METHODS: One and two nights' polysomnography was performed in sedated (protocol A, n=11) and non-sedated (protocol B, n=9) patients, respectively, while respiratory variables were continuously recorded. In each protocol the patients were ventilated with PAV+ and PS at two levels of assist (baseline and high). RESULTS: In both protocols sleep quality did not differ between the modes of support or the assist levels. In sedated patients sleep efficiency was slightly but significantly higher with PAV+ than with high PS, while it did not differ between modes in non-sedated patients. The two modes of support had comparable effects on respiratory variables. Independent of the mode of support and particularly at high assist, a significant proportion of patients developed periodic breathing during sleep (27% in protocol A and 44% in protocol B). CONCLUSION: In patients exhibiting good patient-ventilator synchrony during PS, the large number of short-term end-inspiratory occlusions with PAV+ operation did not adversely influence sleep quality. With both modes high assist may cause unstable breathing during sleep.

Noninvasive bilevel positive pressure ventilation in patients with blunt thoracic trauma.

BACKGROUND: Noninvasive bilevel positive pressure ventilation (N-BiPAP) has an established role in providing respiratory support in patients with acute respiratory failure. The significant advantage of N-BiPAP is to avoid endotracheal intubation and its complications. Currently there are no data that support N-BiPAP as first-line treatment in patients with blunt thoracic trauma. OBJECTIVE: To evaluate the safety and efficacy of N-BiPAP in patients with acute respiratory failure due to blunt thoracic trauma. METHODS: Prospective observational study. Twenty-two patients with blunt chest trauma (mean injury severity score 26 +/- 9) were studied. N-BiPAP was applied via a tight-fitting full or total-face mask, combined with regional anesthesia in all patients. RESULTS: N-BiPAP resulted in significant changes in blood gasses, heart rate and breathing frequency at 1 h. Eighteen out of 22 patients avoided intubation and were discharged from the ICU (success group). Four patients met predefined criteria and required intubation (failure group) within 24 h after N-BiPAP. Three of the patients in the failure group survived while 1 developed septic shock and died. The acute response of oxygenation to N-BiPAP differed significantly between groups, being higher in the success group. Complications related to N-BiPAP were minor, consisting of nose bridge injury (1 patient) and gastric distention (1 patient). CONCLUSIONS: N-BiPAP administration could be a safe and effective method to improve the gas exchange in patients with acute respiratory failure due to blunt thoracic trauma.

Pulmonary sarcoidosis. Correlation of expiratory high-resolution CT findings with inspiratory patterns and pulmonary function tests.

PURPOSE: To assess the presence and extent of air trapping (AT) on chest high-resolution CT (HRCT) in sarcoidosis and to correlate such findings with patterns, lesion extent on inspiratory CT and pulmonary function tests (PFT). MATERIAL AND METHODS: Thirty patients with sarcoidosis underwent inspiratory and expiratory HRCT and PFT. HRCT images were evaluated for presence, distribution and AT extent as well as the predominant HRCT pattern and the extent of lesions at inspiration. Attenuation difference in the AT regions at expiration and at inspiration were calculated. The presence and extent of AT were correlated with PFT, extent of involvement and predominant inspiratory patterns. RESULTS: AT was present in 25/30 patients with no lung zone predilection. AT was the only CT indication of pulmonary sarcoidosis in 3/30 patients who also had normal PFT. Attenuation difference between inspiration and expiration ranged from -40 HU to 106 HU. In 2 patients, a paradoxical decrease of lung attenuation was observed at expiration. A significant correlation was found between AT extent at expiration, with residual volume-total lung capacity ratio and residual volume. CONCLUSION: AT is an additional HRCT finding in sarcoidosis. AT may involve any lung zone, including costophrenic angles and may be the only CT feature of pulmonary sarcoidosis. Strong correlation is only found with PFT values that are specific for incomplete lung emptying at expiration.

Respiratory muscle function in endocrine diseases.

This review reports evidence showing that the function of the respiratory muscles (RMs) is affected in endocrinopathies and emphasizes that clinicians should look for RM weakness in hormone inbalances. Although there is a potential pathophysiological mechanism for affecting RM in diabetes insipidus, hypoparathyroidism, Cushing's disease, pheochromocytoma, adrenalin deficiency or androgen disorder, no study was found in the available literature. Therefore, investigations are urgently needed in these diseases. Controversial results have been reported in acromegaly, hypopituitarism, diabetes mellitus and steroid-induced (iatrogenic) RM myopathy. Obviously, these are areas for further research. Respiratory muscle dysfunction has been well documented in thyroid disease and there is general agreement that both hypo- and hyperthyroidism are associated with reversible respiratory muscle weakness.