Allowing for spontaneous breathing during high-frequency oscillation: the key for final success?

In the present issue of Critical Care, van Heerde and colleagues describe a new technical development (a flow-demand system during high-frequency oscillation) that may have an important impact on the future use of high-frequency ventilation in children and adults. Flow compensation on patient demand seems to reduce the imposed work of breathing, may therefore increase patient comfort, and should theoretically allow for maintaining spontaneous breathing while heavy sedation and muscular paralysis could be avoided. With further technical development of this concept, high-frequency oscillation can finally be added to the techniques of mechanical ventilatory support that maintain, rather than suppress, spontaneous breathing efforts. Furthermore, this concept will give high-frequency oscillation the chance to prove its potential role as primary therapy in patients with acute lung injury/acute respiratory distress syndrome, the chance to reduce the incidence of high-frequency oscillation failure for patient or physician discomfort as reported in so many clinical trials in the past, the chance to most probably allow successful weaning from high-frequency oscillation to extubation, and, ultimately, in analogy to what has been reported from the experience with other ventilator modes that allow for maintaining spontaneous breathing, the chance to decrease ventilator days in patients with acute lung injury/acute respiratory distress syndrome

ICU Cornerstone: High frequency ventilation is here to stay

With favourable and extensive experience in the neonatal intensive care unit (ICU) and the recent positive experience in the adult ICU, high-frequency ventilation has become a valuable alternative to conventional ventilation in acute lung injury. To arrive at this point, physicians' understanding of the characteristics and kinetics of acute lung injury had to become more distinct, and it was necessary to merge accumulated knowledge from experience with high-frequency ventilation in the neonatal population and that with conventional ventilation in adults. However, this now calls for a better designed clinical trial in the adult population that combines the three most important concepts for lung protection: early intervention (before acute respiratory distress syndrome is established); optimal lung recruitment; and careful avoidance of lung over-distention over the entire period of mechanical ventilation

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

Objective: Volume-targeted modes are designed to deliver aconstant tidal volume (Vt) 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 Vt delivery. Design and setting: Bench study of six neonatal ventilators in the volume-targeted mode simulating preterm and full-term infant settings on atest lung. Measurements and results: Breath-to-breath expiratory Vt 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 Vt. Some ventilators delivered inaccurate Vt under steady state condition while others showed considerable breath-to-breath Vt variability. Conclusions: We observed inaccurate Vt delivery under specific conditions as well as immediate and sometimes prolonged volume overshooting after arapid respiratory system compliance increase or resistance decrease in volume-targeted modes of modern neonatal ventilators. Similar discrepancies between the set Vt 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 algorithm

High frequency oscillatory ventilation for respiratory failure due to RSV bronchiolitis

Objective: To describe the time course of high frequency oscillatory ventilation (HFOV) in respiratory syncytial virus (RSV) bronchiolitis. Design: Retrospective charts review. Setting: A tertiary paediatric intensive care unit. Patients and participants: Infants with respiratory failure due to RSV infection. Intervention: HFOV. Measurements and results: Pattern of lung disease, ventilatory settings, blood gases, infant's vital parameters, sedation and analgesia during the periods of conventional mechanical ventilation (CMV, 6 infants), after initiation of HFOV (HFOVi, 9 infants), in the middle of its course (HFOVm), at the end (HFOVe) and after extubation (Post-Extub) were compared. All infants showed a predominant overexpanded lung pattern. Mean airway pressure was raised from a mean (SD) 12.5 (2.0) during CMV to 18.9 (2.7) cmH2O during HFOVi (P<0.05), then decreased to 11.1(1.3) at HFOVe (P<0.05). Mean FiO2 was reduced from 0.68 (0.18) (CMV) to 0.59 (0.14) (HFOVi) then to 0.29 (0.06) (P<0.05) at HFOVe and mean peak to peak pressure from 44.9 (12.4) cmH2O (HFOVi) to 21.1 (7.7) P<0.05 (HFOVe) while mean (SD) PaCO2 showed a trend to decrease from 72 (22) (CMV) to 47 (8) mmHg (HFVOe) and mean infants respiratory rate a trend to increase from 20 (11) (HFOVi) to 34 (14) (HFOVe) breaths/min. With usual doses of sedatives and opiates, no infant was paralysed and all were extubated to CPAP or supplemental oxygen after a mean of 120h. Conclusion: RSV induced respiratory failure with hypercapnia can be managed with HFOV using high mean airway pressure and large pressure swings while preserving spontaneous breathin

Exploring social identities in the South African landscape : a study of young, white, South African student teachers.

Thesis (M.A.)-University of KwaZulu-Natal, Durban, 2007.The social, political and economic landscape of South Africa, since 1994 has been one of rapid change, where identities and what it means to be a South African have formed critical points of debate. This study used a qualitative methodology to investigate two broad goals: firstly to explore the identities, and influencing factors, of a group of nine young, White, South African student teachers (21-25); and secondly to examine the intersection of social identities and teaching. As a result, this study also investigated how conceptions of identity, including "Whiteness" can have an impact on or influence the professional identities of the participants as young teachers in a multi-cultural and diverse classroom. Selection of participants was based on self-identification as "White", however, by focusing on racial identity in particular this study must acknowledge, as Gunaratnam (2003) does, that it is working both "with and against" race. Two in-depth interviews took place with each participant and two props were used in order to avoid foregrounding race and imposing a definition on the individual respondents. Firstly an "I am" worksheet was used which asked for descriptors; and, secondly, each participant was asked to draw a timeline of their life in response to the question 'What has made you who you are today?" Because of the subjective nature of narrative data, the participants' stories were framed in a broader "landscape" or context. Their narratives were complex and often contradictory, pointing to the fact that researching identities, especially within such a shifting landscape, is always tricky. However, some common themes emerged: social identities as descriptors were avoided, being White in South Africa emerged as different from other contexts such as Europe, race was highlighted in relation to "others" in terms of economic, political and social changes to their worlds and as teachers there was a limited understanding of diversity and broader issues outside of their own experience

Surfactant use based on the oxygenation response to lung recruitment during HFOV in VLBW infants

Purpose: Early lung recruitment (ELR) during high-frequency oscillatory ventilation (HFOV) in combination with prophylactic surfactant use has been reported to reduce mortality, improve respiratory outcomes, and reduce the need for repeated surfactant dosing, suggesting that surfactant might be used more selectively in very low birth weight (VLBW) infants on HFOV than generally recommended. We report our first experience from such a selective early rescue use of surfactant in VLBW infants on HFOV. Methods: After a deliberate ELR maneuver and "optimal” continuous distending pressure (CDP) finding during HFOV, used as primary ventilation mode for VLBW infants with respiratory distress syndrome (RDS), surfactant was only given when an unsatisfactory oxygenation response to lung recruitment (as defined by CDP×FiO2>5) was observed. Results: Out of 144 VLBW infants on HFOV, 84 (58.3%) received surfactant and 60 (41.7%) did not. Duration of required oxygen supplementation (37.4±44.9 vs. 46.2±35.4days; P=0.031) and respiratory support (i.e., n-CPAP and/or mechanical ventilation; 22.3±19.3 vs. 38.2±24.3days; P=0.001) was shorter for infants who did not receive surfactant than for those who did. The incidence and severity of bronchopulmonary dysplasia was similar in both groups, and there was no difference in survival rates between groups. Subgroup analysis for infants of less than 28weeks of gestation revealed similar results. Conclusions: First intention HFOV combined with an early attempt at lung volume optimization might allow surfactants to be used more selectively (in relation to disease severity) in VLBW infants presenting with RDS at birth without negatively influencing the outcom

Electrical impedance tomography reveals pathophysiology of neonatal pneumothorax during NAVA

Pneumothorax is a potentially life‐threatening complication of neonatal respiratory distress syndrome (RDS). We describe a case of a tension pneumothorax that occurred during neurally adjusted ventilatory assist (NAVA) in a preterm infant suffering from RDS. The infant was included in a multicenter study examining the role of electrical impedance tomography (EIT) in intensive care and therefore continuously monitored with this imaging method. The attending physicians were blinded for EIT findings but offline analysis revealed the potential of EIT to clarify the underlying cause of this complication, which in this case was heterogeneous lung disease resulting in uneven ventilation distribution. Instantaneous increase in end‐expiratory lung impedance on the affected side was observed at time of the air leak. Real‐time bedside availability of EIT data could have modified the treatment decisions made

Selling HIV/AIDS prevention: a case of mixed messages

This paper reports on a content analysis of three youth magazines, undertaken in order to establish whether the messages of loveLife are diluted, contradicted or reinforced by such examples of popular youth culture. SL, Blunt and Ymag were sampled over a period of six months (July-December 2003) in an attempt to identify and analyse the content and perceptions that these magazines convey to their readers. The relationship between the message content of the three magazines and the core values of loveLife’s educational campaigns is then explored

Electrical impedance tomography reveals pathophysiology of neonatal pneumothorax during NAVA

Pneumothorax is a potentially life‐threatening complication of neonatal respiratory distress syndrome (RDS). We describe a case of a tension pneumothorax that occurred during neurally adjusted ventilatory assist (NAVA) in a preterm infant suffering from RDS. The infant was included in a multicenter study examining the role of electrical impedance tomography (EIT) in intensive care and therefore continuously monitored with this imaging method. The attending physicians were blinded for EIT findings but offline analysis revealed the potential of EIT to clarify the underlying cause of this complication, which in this case was heterogeneous lung disease resulting in uneven ventilation distribution. Instantaneous increase in end‐expiratory lung impedance on the affected side was observed at time of the air leak. Real‐time bedside availability of EIT data could have modified the treatment decisions made