Patients with acute exacerbations of chronic obstructive pulmonary disease may require endotracheal intubation with mechanical ventilation. We designed, and here report on the efficacy of, a noninvasive ventilatory-assistance apparatus to provide inspiratory-pressure support by means of a face mask.

The influence of the endotracheal tube (ETT) during a T-piece trial remains controversial. Our aim was to compare the work of breathing of 14 successfully extubated patients at the end of a 2-h trial (T) and after extubation (E) of the trachea, and to assess, using the acoustic reflection method, the resistance of the endotracheal tube and of the supraglottic airway as well as their related work. We found that the work of breathing of the patients was identical between T and E (1.72 ± 0.59 versus 1.63 ± 0.45 J/L; p = 0.50 and 23.5 ± 10.6 versus 22.6 ± 9.7 J/min; p = 0.70). There was no significant difference between the beginning and the end of the T-piece trial (1.57 ± 0.53 versus 1.72 ± 0.59 J/ L, p = 0.10). The work caused by the ETT amounted to 11.0 ± 3.9% of the total work of breathing. The supraglottic airway resistance was in the normal range and was significantly smaller than the endotracheal tube resistance (0.79 ± 0.4 versus 1.43 ± 0.31 cm H₂O · s/L; p = 0.008, flow = 0.25 L/s). We conclude that a 2-h trial of spontaneous breathing through an endotracheal tube well mimics the work of breathing performed after extubation, in patients who pass a weaning trial and do not require reintubation.

We compare the measurements of viscoelastic properties of adherent alveolar epithelial cells by two micromanipulation techniques: (i) magnetic twisting cytometry and (ii) optical tweezers, using microbeads of same size and similarly attached to F-actin. The values of equivalent Young modulus E, derived from linear viscoelasticity theory, become consistent when the degree of bead immersion in the cell is taken into account. E-values are smaller in (i) than in (ii): ∼34–58 Pa vs ∼29–258 Pa, probably because higher stress in (i) reinforces nonlinearity and cellular plasticity. Otherwise, similar relaxation time constants, around 2 s, suggest similar dissipative mechanisms.

The effects of flow triggering (FT) as compared with pressure triggering (PT) on breathing effort have been the focus of several studies, and discrepant results have been reported. In the initial part of our study, a lung model was used to quantify triggering effort (airway pressure–time product, PTPaw) for a range of sensitivity settings in nine new-generation ventilators. A ventilator providing both FT and PT was then used to compare these systems during pressure-support (PSV) and volume-targeted assist-control ventilation (ACV) in eight ventilator-dependent patients, using sensitivity settings (2 L/min for FT and − 2 cm H2O for PT) that had proven significantly different in the initial bench study. Indexes of effort included the esophageal and transdiaphragmatic pressure–time products and inspiratory work of breathing per minute (PTPes/min, PTPdi/min, and Wi/min, respectively). The experimental study revealed significant differences between ventilators in PTPaw at commonly used settings. In two of three ventilators featuring both systems, PTPaw was significantly lower with FT than PT (p < 0.001). In the clinical study, FT as compared with PT, was associated with reductions in all indexes of breathing effort during PSV: 16 ± 6% (p < 0.001), 13 ± 10% (p < 0.01), and 14 ± 12% (p < 0.05) for PTPdi/min, PTPes/min, and Wi/min, respectively. By contrast, no differences were found when FT was used during ACV. Although FT reduced triggering effort in both modes (p < 0.001), the effects observed during the post-trigger phase differed, and explained the discrepant results between the two modes. We conclude that FT more effectively reduces breathing effort when used in conjunction with a pressure-targeted mode than with a volume-targeted mode, especially when flow delivery is close to or below demand.

The use of helium–oxygen (HeO2) was tested in combination with noninvasive ventilation (NIV) in 10 patients with acute exacerbation of chronic obstructive pulmonary disease (COPD). Effort to breathe as assessed by the respiratory muscle pressure-time index (PTI), work of breathing (WOB), and gas exchange were the main endpoints. Results of NIV-HeO2 were compared with those obtained with standard NIV (AirO2), at two levels of pressure-support ventilation (PSV), 9 ± 2 cm H2O and 18 ± 3 cm H2O. Significant reductions in PTI were observed between HeO2 and AirO2 at both the low PSV level (n = 9; 160 ± 58 versus 198 ± 78 cm H2O/s/ min; p < 0.05) and the high PSV level (n = 10; 100 ± 45 versus 150 ± 82 cm H2O/s/min; p < 0.01). WOB also differed significantly between HeO2 and AirO2 (7.8 ± 4.1 versus 10.9 ± 6.1 J/min at the low PSV level, p < 0.05; and 5.7 ± 3.3 versus 9.2 ± 5. J/min, p < 0.01 at the high PSV level). HeO2 reduced PaCO2 at both the low PSV level (61 ± 13 versus 64 ± 15 mm Hg; p < 0.05) and the high PSV level (56 ± 13 versus 58 ± 14 mm Hg; p < 0.05), without significantly changing breathing pattern or oxygenation. We conclude that use of HeO2 during NIV markedly enhances the ability of NIV to reduce patient effort and to improve gas exchange.