Stefano Nava

Objective Imperfect patient–ventilator interaction is common during assisted ventilation, and the detection of clinically relevant mismatching requires visual monitoring of the ventilator screen. We have assessed the feasibility, sensitivity and specificity of an algorithm embedded in a ventilator system that is able to automatically detect the occurrence of ineffective triggering and double triggering in real time. Design Prospective study. Setting Respiratory intensive care unit. Methods Twenty patients undergoing pressure-support ventilation, either non-invasively (NIV, n = 10) or conventionally ventilated (n = 10), were studied. Measurements The detection of ineffective triggering and double triggering from the algorithm was compared by two operators with the “real” occurrence of the phenomena as assessed using the transdiaphragmatic pressure (Pdi). Results Seven of the 20 patients exhibited gross mismatching, while in the remaining patients patient–ventilator mismatching was artificially induced using a pressure control, with a low respiratory rate. Ineffective triggering and double triggering were identified by the operators in 507 and 19 of the 3343 analyzed breaths, respectively. False positives were significantly more frequent in the NIV group than with conventional ventilation. The algorithm had an overall sensitivity of 91% and specificity of 97%. Specificity was statistically higher in the conventional ventilated group than with NIV (99% vs. 95%, p < 0.05). Conclusions We have demonstrated the feasibility and efficacy of a new algorithm to detect the occurrence of impaired patient–ventilator interaction during mechanical ventilation in real time. This software may help the clinician in the identification of this problem, which has been shown to have important clinical consequences.

A survey was performed on behalf of the European Respiratory Society to assess end-of-life practices in patients admitted to European respiratory intermediate care units and high dependency units over a 6-month period.A 33-item questionnaire was sent by e-mail to physicians throughout Europe and the response rate was 28 (29.5%) out of 95. A total of 6,008 patients were admitted and an end-of-life decision was taken in 1,292 (21.5%). The mortality rate in these patients was 68% (884 out of 1,292).The patients received similar proportions of withholding of treatment (298 (23%) out of 1292), do-not-resuscitate or do-not-intubate orders (442 (34%) out of 1,292) and noninvasive mechanical ventilation as the ceiling of ventilatory care (402 (31%) out of 1,292). Withdrawal of therapy was employed in 149 (11%) out of 1,292 patients and euthanasia in one. Do-not-intubate/do-not-resuscitate orders were more frequently used in North compared with South Europe. All of the 473 competent patients directly participated in the decision, whereas, in 722 (56%) out of 1,292 cases, decision-making was reported to be shared with the nurses.In European respiratory intermediate care units and high dependency units, an end-of-life decision is taken for 21.5% of patients admitted. Withholding of treatment, do-not-intubate/do-not-resuscitate orders and noninvasive mechanical ventilation as the ventilatory care ceiling are the most common procedures. Competent patients are often involved, together with nurses.

Rationale T-piece trials and spontaneous breathing trials through the tracheostomy tube are often used as weaning techniques. They are usually performed with the cuff inflated, which may increase the inspiratory load and/or influence the tidal volume generated by the patient. We assessed diaphragmatic effort during T-piece trials with or without cuff inflation. Settings Respiratory intensive care unit Methods We measured breathing pattern, transdiaphragmatic pressure (Pdi), the pressure-time product of the diaphragm, per minute (PTPdi/min) and per breath (PTPdi/b), and lung mechanics (lung compliance and resistance) in 13 tracheotomized patients ready for a weaning trial. V_T was recorded with respiratory inductive plethysmography (RIP-V_T) or pneumotachography PT-V_T). Patients completed two T-piece trials of 30 min each with or without the cuff inflated. Results RIP-V_T and PT-V_T values were similar with the cuff inflated, but PT-V_T significantly underestimated RIP-V_T when the cuff was deflated, and therefore the RIP-V_T was chosen as the reference method. The RIP-V_T was significantly greater and the Pdi and PTPdi/min significantly lower when the cuff was deflated than when it was inflated. The efficiency of the diaphragm, calculated by the ratio of PTPdi/b over RIP-V_T, was also improved, while no changes were observed in lung mechanics. Conclusions Diaphragmatic effort is significantly lower during a T-piece trial with a deflated cuff than when the cuff is inflated, while RIP-V_T is higher, so that the diaphragm's efficiency in generating tidal volume is also improved.

Educational aims To present four innovative papers from the field on non-invasive ventilation published in 2004 and to discuss the important points and conclusions from each. Summary This paper summarises the findings of four important papers that have been published over the last year. The first paper reports data on the success rate of NIV in patients with early onset of ARF due to SARS. Furthermore, the paper discusses how NIV may be used in patients affected by highly contagious diseases in a way which is safe for healthcare workers. The second paper concentrates on dying at end-stage disease and the limits of medical care. It studies the use of NIV treatment in patients with CHF and COPD affected by ARF who have signed a DNI order. The next article investigates the use of both CPAP and NIV delivered by face mask in patients with CPE, when compared with the use of oxygen alone, and their effect on physiological parameters and avoiding intubation. Finally, the last paper reviewed reports on the use of NIV to treat an episode of post-extubation respiratory failure in “unselected” patients. This review article aims to keep the reader updated on the most recent and some of the important advancements in this field over the last year.

Background. A low body mass index is one of the strongest predictors of mortality in Chronic Obstructive Pulmonary Disease (COPD) patients. Under-nutrition is often associated with skeletal muscle wasting and hypophosphatemia. Aim and Methods. In a pilot, randomised, doubleblind placebo-controlled study, we assessed the physiological effects of phosphorous administration in 17 stable undernourished COPD patients, on diaphragmatic function, breathing pattern, neuromuscular drive (P0.1) and dyspnea score. Fructose 1.6-diphosphate (FDP) or placebo was administered i.v. for 7 consecutive days. Results. FDP administration was associated with a marked increase in inspiratory time (Ti) that induced a significant rise (p<0.05) in the Pressure Time Product of the diaphragm per breath (PTPdi/b). However, since breathing frequency also decreased, the Pressure Time Product per minute of the diaphragm (PTPdi/min), index of diaphragmatic energy expenditure was markedly reduced. The efficiency of the respiratory pump in clearing CO2 was also improved, although not significantly, in the FDP group (p=0.09) as well as the maximal transdiaphragmatic pressure during the sniff manoeuvre (Pdi,sniff). Conclusions. This pilot physiological study showed that phosphorus replacement in undernourished, stable COPD patients, may be associated with a complex modification in respiratory pattern and diaphragmatic functions, leading to a marked although not significant reduction in PTPdi/min.