Short-term effects of non-invasive ventilation on cerebral blood flow and cognitive function in COPD.

OBJECTIVES: Investigate the acute effects of non-invasive ventilation (NIV) on cerebral blood flow (CBF) and on cognitive functions in COPD. METHODS: Nine non-hypercapnic stable COPD and twelve healthy controls were enrolled. CBF (transcranial Doppler), cognitive tests and cardiorespiratory response were performed at baseline, during one hour of NIV and after 30 min. RESULTS: Both groups had an increase in tidal volume and reduction in respiratory rate during NIV, but only controls showed PaCO2 reductions (41.2 ±â€¯4.6 to 36.5 ±â€¯7.3 in controls vs. 40.9 ±â€¯4.5 to 42.9 ±â€¯5.9 in COPD). During NIV CBF was significantly reduced in healthy controls and COPD, although this effect was less pronounced in the latter. At the same time, healthy controls demonstrated an improvement in cognitive executive function compared to COPD in the Trail Making Test part B (90.5 vs. 180s; respectively). CONCLUSION: NIV application for one hour reversibly reduced CBF in healthy controls and non-hypercapnic stable COPD patients, despite no significant reductions of the PaCO2 in the latter group. It was associated with minor cognitive improvements in the executive function in healthy volunteers, but not in COPD.

Effect of an automatic triggering and cycling system on comfort and patient-ventilator synchrony during pressure support ventilation.

BACKGROUND: The digital Auto-Trak™ system is a technology capable of automatically adjusting the triggering and cycling mechanisms during pressure support ventilation (PSV). OBJECTIVE: To compare Auto-Trak with conventional settings in terms of patient-ventilator synchrony and discomfort. METHODS: Twelve healthy volunteers underwent PSV via the mouth by breathing through an endotracheal tube. In the conventional setting, a pressure support of 8 cm H2O with flow cycling (25% peak inspiratory flow) and a sensitivity of 1 cm H2O was adjusted. In Auto-Trak the triggering and cycling were automatically set. Discomfort, effort of breathing, and the asynchrony index (AI) were assessed. In a complementary bench study, the inspiratory and expiratory time delays were quantified for both settings in three mechanical models: 'normal', obstructive (COPD), and restrictive (ARDS), using the ASL 5000 simulator. RESULTS: In the volunteer study the AI and the discomfort scores did not differ statistically between the two settings. In the bench investigation the use of Auto-Trak was associated with a greater triggering delay in the COPD model and earlier expiratory cycling in the ARDS model but with no asynchronic events. CONCLUSIONS: Use of the Auto-Trak system during PSV showed similar results in comparison to the conventional adjustments with respect to patient-ventilator synchrony and discomfort in simulated conditions of invasive mechanical ventilation.

Continuous positive airway pressure effects on regional lung aeration in patients with COPD: a high-resolution CT scan study.

BACKGROUND: The effects of nasal continuous positive airway pressure (CPAP) on the lung parenchyma of patients with COPD, to our knowledge, have never been assessed by high-resolution CT (HRCT) scanning. METHODS: HRCT scans were obtained at the apex, hilum, and basis of the lungs at functional residual capacity while on spontaneous respiration and at the end of CPAP trials of 5 cm water (H(2)O), 10 cm H(2)O, and 15 cm H(2)O in 11 stable patients with COPD and eight healthy volunteers. Lung aeration was assessed by quantitative density parameters and by qualitative analysis of each CT image after processing by means of a density-based color-mask computational algorithm. The quantitative parameters were density histograms, the relative area of the lungs with attenuation values < -950 Hounsfield units (percentage of hyperaerated areas) and the 15th percentile (the density value separating the 15% voxels of least density). RESULTS: A CPAP of 5 cm H(2)O caused little increase in lung aeration in both groups, but in some patients with COPD, CPAP deflated some regions of the lungs. CPAP levels of 10 cm H(2)O and 15 cm H(2)O increased the emphysematous zones in all sectors of the lungs, including dorsal and apical regions in patients with COPD compared to little hyperaeration predominantly in the ventral areas in healthy volunteers. CONCLUSIONS: Nasal CPAP causes variable effects on regional lung aeration in relation to the applied pressure and the regional distribution of emphysema in patients with COPD. Low pressure levels may cause regional lung deflation in some patients. High levels increase the emphysematous areas wherever they are located inside the lungs.