Volume-targeted modes of modern neonatal ventilators: how stable is the delivered tidal volume?

Objective Volume-targeted modes are designed to deliver a constant tidal volume (V_t) at lowest possible pressure independently of changes in compliance, resistance, and leak of the respiratory system. We examined whether these volume-targeted modes respond rapidly enough to sudden changes in respiratory mechanics (e.g., selective intubation, surfactant administration, endotracheal tube kinking, de-kinking, obstruction), resulting in insufficient or excessive V_t delivery. Design and setting Bench study of six neonatal ventilators in the volume-targeted mode simulating preterm and full-term infant settings on a test lung. Measurements and results Breath-to-breath expiratory V_t were measured after rapid compliance, resistance, and leak changes. Under our test settings all ventilators showed important volume overshooting following rapid increase in compliance or decrease in resistance. Between one and 16 inflations were required to return to the set V_t. Some ventilators delivered inaccurate V_t under steady state condition while others showed considerable breath-to-breath V_t variability. Conclusions We observed inaccurate V_t delivery under specific conditions as well as immediate and sometimes prolonged volume overshooting after a rapid respiratory system compliance increase or resistance decrease in volume-targeted modes of modern neonatal ventilators. Similar discrepancies between the set V_t and the delivered inflations can be harmful in clinical situations, especially in newborns. Their clinical relevance needs to be clarified with safety studies in the neonatal population and we encourage manufacturers to further improve the ventilators algorithms. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Are nurses able to assess fatigue,exertion fatigue and types of fatigue in residential home patients?

Are nurses able to assess fatigue, exertion fatigue and types of fatigue in residential home patients? Although fatigue is recognized as a subjective, generalized, extensive and disabling health care problem with a relatively high prevalence among the chronically ill, there have been no studies to show whether nurses caring for fatigued subjects are able to accurately assess the level of fatigue that exists in these patients. The aim of the present study is to investigate this issue. The following research questions are formulated: (1) To what degree do the assessments of fatigue and exertion fatigue given by nurses and patients agree? and (2) To what degree do the assessments of types of fatigue given by nurses and patients agree? The method adopted employed a correlational design approach applied to residential home patients and nurses. Data were gathered by questionnaire. Data collected from 44 selected patients and two assessors (nurses) for each patient are used in the analyses. Measurement instruments used are the Dutch fatigue scale (DUFS), the Dutch exertion fatigue scale (DEFS), types of fatigue and sociodemographic variables. Measurement correlations between the patients and the nurses, both for the DUFS and DEFS, showed fair agreement (fatigue and exertion fatigue) and slight agreement (types of fatigue). The main conclusion of this study is that nurses working in residential home care are unable, in comparison with the patients themselves, to accurately assess patient's fatigue (fair agreement), exertion fatigue (fair agreement) and types of fatigue (slight agreement).     

Are COX-2 inhibitors truly able to prevent NSAIDs-associated ulcer?

Non-steroidal anti-inflammatory drugs(NSAIDs) have a potential to cause mucosal injury in the gastrointestinal tract. Inhibitions of cyclooxygenase, one of the targets of NSAIDs and direct cytotoxic effects of NSAIDs, are reported to be involved in NSAIDs-related mucosal damage. It is estimated that 15-30% of patients taking NSAIDs develop gastroduodenal ulcers, 2% of patients have life-threatening complications. Normal gastroduodenal mucosa expresses only COX-1, and it is reported that NSAIDs are more strongly inhibiting COX-1 are more harmful to gastroduodenal mucosa. Therefore, selective COX-2 inhibitors have been developed as safer NSAIDs than non-selective NSAIDs. Recent reports have, however, shown that COX-2 is expressing in gastroduodenal ulcers and H. pylori infection, suggesting that COX-2 plays an important role in mucosal healing. In this article, we discuss whether COX-2 selective inhibitors are able to prevent NSAIDs-associated ulceration.     

Are ward sisters and charge nurses able to fulfil their role?

AIM: To investigate the self-reported duties carried out by sisters and charge nurses working on the wards and to assess the attitudes of these health care professionals towards their management role. METHOD: Questionnaire. RESULTS: Sisters/charge nurses were allocated patients in addition to being in charge of their ward for, on average, half of their shifts each week. Most of them did not have time to complete their managerial duties, which included supporting and supervising other staff on patient care issues. More than 50 per cent of the sisters/charge nurses did not have the time to attend clinical supervision. CONCLUSION: Sisters/charge nurses treat clinical care--both delivering it directly themselves and advising other staff on its delivery--as a higher priority than their managerial and administrative duties; lack of time is a barrier to the successful fulfilment of their role.     

Are we able to comply with the NICE head injury guidelines?

Background: An estimated 120 000 patients are admitted to hospital in England and Wales each year for neurological observations following a head injury. The National Institute for Clinical Excellence (NICE) has issued guidelines on the quality and frequency of neurological observations that should be made. Objective: Review of frequency and quality of observations in one trauma unit. Study design: Prospective audit of current practice. Method: Data on 100 consecutive patients admitted to a trauma unit for neurological observations were audited to monitor the consistency and frequency of neurological observations requested by the admitting doctor. Medical staff had previously been briefed on the recommendations of the NICE head injury guidelines. Results: A detailed evaluation revealed inconsistency and inexplicable gaps in observations. No single set of observations was complete. Sequential regular monitoring was difficult for many reasons, bringing into question the safety and reliability of current practice. Conclusions: The introduction of the new guidelines which recommend more frequent neurological observations has major staffing implications, where underperformance raises significant clinical governance issues. All hospitals admitting patients with head injuries should have an established protocol based on the NICE guidelines with observations recorded on an appropriately designed data collection form. Trained nursing staff have enormous work and time pressures including direct patient care, ward rounds, drug rounds, administration, management, and responding to emergencies. The development of a competency based training programme for auxiliary nursing staff to undertake neurological observations, including when to report concerns, is one solution to reduce the pressure on trained nursing staff.     

Are people with learning disabilities able to contribute to focus groups on health promotion?

AIM: This paper shows the differences between the success of three focus groups in promoting group discussion on health promotion and also the detailed effects of individual members with speech and language difficulties in participating. BACKGROUND: Conducting focus groups with people with learning disabilities can promote their social inclusion. CONCLUSIONS: We conclude that focus groups are an effective method of conducting exploratory research with adults with learning disabilities in the community, however, ability to participate with other members may be a limiting factor. Furthermore, special arrangements may need to be made for groups to be successful, including the use of an interpreter. The preparation of the moderator is also an important factor in group success.     

Ultra-protective tidal volume: how low should we go?

Applying tidal volumes of less than 6 mL/kg might improve lung protection in patients with acute respiratory distress syndrome. In a recent article, Retamal and colleagues showed that such a reduction is feasible with conventional mechanical ventilation and leads to less tidal recruitment and overdistension without causing carbon dioxide retention or auto-positive end-expiratory pressure. However, whether the compensatory increase in the respiratory rate blunts the lung protection remains unestablished.Further reducing tidal volumes beyond the standard 6 mL/kg is an appealing goal in patients with acute respiratory distress syndrome (ARDS) [1]. Such reduction could decrease the tidal stretch imposed on the lung, potentially attenuating further the ventilator-induced lung injury [2]. In fact, tidal volumes of less than 6.5 mL/kg and as low as 4 mL/kg were recently associated with increased survival in patients with ARDS [3]. One of the main obstacles to such a strategy is the potential for carbon dioxide (CO₂) retention and severe acidosis. To avoid this, specialized techniques, such as high-frequency oscillatory ventilation and extracorporeal CO₂ removal, have been previously tested with mixed results [4-6].In the previous issue of Critical Care, Retamal and colleagues proposed that lower tidal volumes could be used with conventional positive-pressure ventilation without leading to CO₂ retention [1]. A reduction in tidal volume from 6 to 4 mL/kg was feasible with a decrease in the instrumental dead space and an increase in the respiratory rate. In patients with ARDS, the dead space is a marker of disease severity [7]. Consequently, very low tidal volumes can be difficult to use in practice, especially in very sick patients, because the necessary increase in respiratory rate might cause significant auto-positive end-expiratory pressure (auto-PEEP). Luckily, patients with severe ARDS also tend to have low lung compliance [8], making their lungs inflate and deflate fast. Therefore, this restrictive ventilatory pattern allows the safe use of high respiratory rates without leading to significant auto-PEEP.Retamal and colleagues [1] should be congratulated for their careful design of the ventilator protocol in the 4 mL/kg phase, which allowed an effective CO₂ elimination. The bottom line is that if one decides to use very low tidal volumes with high respiratory rates, attention to the details is invaluable. First, the removal of any dispensable dead space, including substituting an external heated humidifier by the heat-moisture exchanger, is imperative. Second, the use of volume-controlled ventilation helps to keep short inspiratory times. Peak airway pressures may increase, but the preserved expiratory time guarantees low auto-PEEP and, consequently, low plateau pressures. For safety, plateau pressures and auto-PEEP should be measured periodically. Third, in selected cases with high recruitability, the alveolar dead space can be minimized through recruitment maneuvers and higher PEEP values. Finally, the use of a short end-inspiratory pause is encouraged to improve the CO₂ elimination [9]. These measures will improve the safety and optimize the CO₂ elimination of a strategy with very low tidal volumes, even with higher-than-normal respiratory rates.However, even successfully avoiding CO₂ retention, this strategy has yet to be proven effective in terms of further lung protection. We believe that two aspects should be taken into consideration. The first is whether the strategy attenuated the mechanisms of lung injury. The authors performed computed tomography scans in all patients at tidal volumes of both 4 and 6 mL/kg and showed that the amount of cyclic recruitment-derecruitment and hyperinflation decreased after reducing the tidal volume. Although the absolute reduction was small (less than 1% of the lung weight), this finding is suggestive of decreased injury per breath. The second aspect is that an increased respiratory rate can be injurious per se [10]. It would be important to know whether the compensatory increase of the respiratory rate blunted the protective effect per breath of the tidal volume reduction.This tradeoff was emphasized recently in a model of the energy delivered by the ventilator as a surrogate for the potential lung damage [11]. Decreases in tidal volume require disproportionate increases in respiratory rate to maintain alveolar ventilation, and so more energy can be delivered to the lungs even at reduced stress and strain per breath. Though purely theoretical, this hypothesis helps reconcile our expectation of a further protective effect of very low tidal volumes with the recent findings of harmful or null effect of oscillatory high-frequency ventilation [5,6]. In these trials, it is possible that the reduction in lung injury per breath was offset by the very high respiratory rates applied.Finally, Retamal and colleagues [1] followed their patients for 5 to 30 minutes only. Since lower tidal volumes tend to promote atelectasis, especially under insufficient PEEP [12], a longer observation time perhaps would have shown an increase in atelectasis and driving pressures, opposing the benefits initially achieved.In conclusion, we are convinced that a strategy with very low tidal volumes (4 mL/kg) is feasible with conventional positive-pressure ventilation. This strategy could be used in patients with high plateau pressures or high driving pressures with standard 6 mL/kg tidal volumes, but we need more data in terms of lung protection before we can recommend this strategy to every patient with ARDS.     

How clean is the home environment?: a tool to assess home hygiene

The role of the home environment in the transmission of infectious diseases has been well described in the developing world but has received less attention in developed countries. An increasing focus on home hygiene has emerged in debates regarding the use of antimicrobial products in the home and the potential for development of resistance and in discussions regarding "when is clean too clean" and "what is clean." Studies are clearly needed to further explicate the role of the home in the spread of infectious agents, but before these can be conducted, adequate measurement tools are essential. This article describes extensive psychometric testing undertaken to develop valid and reliable methods and tools to measure home hygiene and focuses on a neighborhood that was primarily Spanish speaking in New York City. The Home Hygiene Assessment Tool described in this article can be used by clinicians and researchers to further elucidate the role of the home environment in the prevention and control of infections.     

Electrical impedance tomography: a method for monitoring regional lung aeration and tidal volume distribution?

Objective To demonstrate the monitoring capacity of modern electrical impedance tomography (EIT) as an indicator of regional lung aeration and tidal volume distribution.Design and setting Short-term ventilation experiment in an animal research laboratory.Patients and participants One newborn piglet (body weight: 2 kg).Interventions Surfactant depletion by repeated bronchoalveolar lavage, surfactant administration.Measurements and results EIT scanning was performed at an acquisition rate of 13 images/s during two ventilatory manoeuvres performed before and after surfactant administration. During the scanning periods of 120 s the piglet was ventilated with a tidal volume of 10 ml/kg at positive end-expiratory pressures (PEEP) in the range of 0–30 cmH₂O, increasing and decreasing in 5 cmH₂O steps. Local changes in aeration and ventilation with PEEP were visualised by EIT scans showing the regional shifts in end-expiratory lung volume and distribution of tidal volume, respectively. In selected regions of interest EIT clearly identified the changes in local aeration and tidal volume distribution over time and after surfactant treatment as well as the differences between stepwise inflation and deflation.Conclusions Our data indicate that modern EIT devices provide an assessment of regional lung aeration and tidal volume and allow evaluation of immediate effects of a change in ventilation or other therapeutic intervention. Future use of EIT in a clinical setting is expected to optimise the selection of appropriate ventilation strategies.