Liam M. Hannan

Bio: Liam M. Hannan is an academic researcher from University of Melbourne. The author has contributed to research in topics: Medicine & Mechanical ventilation. The author has an hindex of 7, co-authored 21 publications receiving 133 citations. Previous affiliations of Liam M. Hannan include Northern Health & Austin Hospital.

Inpatient and long-term outcomes of individuals admitted for weaning from mechanical ventilation at a specialized ventilation weaning unit.

Abstract: Background: Weaning from invasive mechanical ventilation (IMV) in specialized weaning units has been demonstrated to be safe and cost-effective. Success rates and outcomes vary widely, probably relating to patient factors and unit expertise. Methods: An audit was undertaken of patients admitted for weaning from IMV at the Austin Hospital Ventilation Weaning Unit (VWU) between March 2002 and January 2008. Weaning success, complications and both in-hospital and long-term mortality were examined and regression analysis was undertaken to examine factors related to these outcomes. Results: Seventy-eight patients were admitted to the VWU after a median of 27 days of IMV at their referring centre. Weaning success rate (ventilator free or nocturnal non-invasive ventilation only) was 78.2% (n = 61). Inpatient mortality was 10.2% (n = 8) and serious complications were infrequent. Progressive neuromuscular disease (odds ratio 0.10) and sepsis during admission to the VWU (odds ratio 0.09) were predictive of weaning failure at discharge. Overall survival at 12 months following discharge from the VWU was 66.7% (n = 52) with most survivors residing in the community. Increasing age (hazard ratio 1.93), referral from rural or outer metropolitan centres (hazard ratio 3.57 and 2.37 respectively) and a diagnosis of chronic obstructive pulmonary disease were associated with increased long-term mortality. Conclusion: High rates of weaning success with infrequent complications and low mortality were achieved in this specialized non-intensive care unit-based weaning unit. The VWU may provide a useful template for the development of similar units elsewhere.

Randomised controlled trial of polysomnographic titration of noninvasive ventilation.

Abstract: Noninvasive ventilation (NIV) settings determined during wakefulness may produce patient–ventilator asynchrony (PVA) during sleep, causing sleep disruption and limiting tolerance. This study investigated whether NIV titrated with polysomnography (PSG) is associated with less PVA and sleep disruption than therapy titrated during daytime alone. Treatment-naive individuals referred for NIV were randomised to control (daytime titration followed by sham polysomnographic titration) or PSG (daytime titration followed by polysomnographic titration) groups. Primary outcomes were PVA and arousal indices on PSG at 10 weeks. Secondary outcomes included adherence, gas exchange, symptoms and health-related quality of life (HRQoL). In total, 60 participants were randomised. Most (88.3%) had a neuromuscular disorder and respiratory muscle weakness but minor derangements in daytime arterial blood gases. PVA events were less frequent in those undergoing polysomnographic titration (median (interquartile range (IQR)): PSG 25.7 (12–68) events·h−1versus control 41.0 (28–182) events·h−1; p=0.046), but arousals were not significantly different (median (IQR): PSG 11.4 (9–19) arousals·h−1versus control 14.6 (11–19) arousals·h−1; p=0.258). Overall adherence was not different except in those with poor early adherence ( NIV titrated with PSG is associated with less PVA but not less sleep disruption when compared with therapy titrated during daytime alone.

Direct ultrasound localisation for pleural aspiration: translating evidence into action.

Abstract: BACKGROUND: There is strong evidence that direct ultrasound localisation for pleural aspiration reduces complications, but this practice is not universal in Australia and New Zealand. AIMS: To describe the current utilisation and logistical barriers to the use of direct ultrasound localisation for pleural aspiration by respiratory physicians from Australia and New Zealand, and to determine the cost benefits of procuring equipment and training resources in chest ultrasound. METHODS: We surveyed all adult respiratory physician members of the Thoracic Society of Australia and New Zealand regarding their use of direct ultrasound localisation for pleural aspiration. We performed a cost-benefit analysis for acquiring bedside ultrasound equipment and estimated the capacity of available ultrasound training. RESULTS: One hundred and forty-six of 275 respiratory physicians responded (53% response). One-third (33.6%) of respondents do not undertake direct ultrasound localisation. Lack of training/expertise (44.6%) and lack of access to ultrasound equipment (41%) were the most frequently reported barriers to performing direct ultrasound localisation. An average delay of 2 or more days to obtain an ultrasound performed in radiology was reported in 42.7% of respondents. Decision-tree analysis demonstrated that clinician-performed direct ultrasound localisation for pleural aspiration is cost-beneficial, with recovery of initial capital expenditure within 6 months. Ultrasound training infrastructure is already available to up-skill all respiratory physicians within 2 years and is cost-neutral. CONCLUSION: Many respiratory physicians have not adopted direct ultrasound localisation for pleural aspiration because they lack equipment and expertise. However, purchase of ultrasound equipment is cost-beneficial, and there is already sufficient capacity to deliver accredited ultrasound training through existing services.

Clinical utility of sequential venous blood gas measurement in the assessment of ventilatory status during physiological stress

Abstract: Background Venous blood gases (VBG) are commonly utilised, particularly in the emergency setting, to assess and monitor patients at risk of ventilatory failure with limited evidence regarding their clinical utility in the assessment of ventilatory status over time. Aims This study aims to assess agreement between arterial and venous pH and partial pressure of carbon dioxide (pCO2) both before and after physiological stress, at each time point, and within the same subject between paired samples before and after bronchoscopy. Methods Prospective study of 30 patients undergoing flexible bronchoscopy under conscious sedation. Paired arterial and venous samples taken before and after bronchoscopy were analysed utilising descriptive statistics and bias plot (Bland–Altman) analysis to assess limits of agreement. Results Compared with baseline, post-bronchoscopy arterial blood gas and VBG showed reduced pH (−0.05 ± 0.05 and −0.04 ± 0.04 respectively) and increased arterial and venous pCO2 (5.9 ± 6.7 and 3.5 ± 5.5 mmHg respectively), the differences being statistically significant (P = 0.035). There was statistical agreement between arterial blood gas and VBG parameters; however, the limits of agreement were wide at rest and, for pCO2, widened further post-bronchoscopy. Conclusion Sequential VBG provide an unpredictable means for assessing pCO2 in patients undergoing flexible bronchoscopy. Previously noted poor agreement between arterial and venous pCO2 worsens following physiological stress, with sequential VBG likely to underestimate changes in ventilatory status in patients with acute respiratory compromise, suggesting limited utility as a means for monitoring changes in ventilation.

Care Practices and Health-related Quality of Life for Individuals Receiving Assisted Ventilation. A Cross-National Study.

Abstract: Rationale: Comparisons of home mechanical ventilation services have demonstrated considerable regional variation in patient populations managed with this therapy. The respiratory care practices used to support individuals receiving assisted ventilation also appear to vary, but they are not well described. It is uncertain whether differences in the approach to care could influence health outcomes for individuals receiving assisted ventilation.Objectives: We sought to identify and describe the respiratory care practices of home ventilation providers in two different regions and determine whether care practice differences influence health-related quality of life.Methods: We conducted a cross-national survey of individuals receiving assisted ventilation managed by two statewide home mechanical ventilation providers, one in Victoria, Australia, and the other in British Columbia, Canada. The survey was used to evaluate care practices, functional and physical measures, socioeconomic attributes, and health-relate...

Relating oxygen partial pressure, saturation and content: the haemoglobin–oxygen dissociation curve

Abstract: The delivery of oxygen by arterial blood to the tissues of the body has a number of critical determinants including blood oxygen concentration (content), saturation (S O2 ) and partial pressure, haemoglobin concentration and cardiac output, including its distribution. The haemoglobin-oxygen dissociation curve, a graphical representation of the relationship between oxygen satur-ation and oxygen partial pressure helps us to understand some of the principles underpinning this process. Historically this curve was derived from very limited data based on blood samples from small numbers of healthy subjects which were manipulated in vitro and ultimately determined by equations such as those described by Severinghaus in 1979. In a study of 3524 clinical specimens, we found that this equation estimated the S O2 in blood from patients with normal pH and S O2 >70% with remarkable accuracy and, to our knowledge, this is the first large-scale validation of this equation using clinical samples. Oxygen saturation by pulse oximetry (S pO2 ) is nowadays the standard clinical method for assessing arterial oxygen saturation, providing a convenient, pain-free means of continuously assessing oxygenation, provided the interpreting clinician is aware of important limitations. The use of pulse oximetry reduces the need for arterial blood gas analysis (S aO2 ) as many patients who are not at risk of hypercapnic respiratory failure or metabolic acidosis and have acceptable S pO2 do not necessarily require blood gas analysis. While arterial sampling remains the gold-standard method of assessing ventilation and oxygenation, in those patients in whom blood gas analysis is indicated, arterialised capillary samples also have a valuable role in patient care. The clinical role of venous blood gases however remains less well defined.

Talaromyces (Penicillium) marneffei infection in non-HIV-infected patients.

Abstract: Talaromyces (Penicillium) marneffei is an important pathogenic thermally dimorphic fungus causing systemic mycosis in Southeast Asia. The clinical significance of T. marneffei became evident when the human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome epidemic arrived in Southeast Asia in 1988. Subsequently, a decline in the incidence of T. marneffei infection among HIV-infected patients was seen in regions with access to highly active antiretroviral therapy and other control measures for HIV. Since the 1990s, an increasing number of T. marneffei infections have been reported among non-HIV-infected patients with impaired cell-mediated immunity. Their comorbidities included primary adult-onset immunodeficiency due to anti-interferon-gamma autoantibodies and secondary immunosuppressive conditions including other autoimmune diseases, solid organ and hematopoietic stem cell transplantations, T-lymphocyte-depleting immunsuppressive drugs and novel anti-cancer targeted therapies such as anti-CD20 monoclonal antibodies and kinase inhibitors. Moreover, improved immunological diagnostics identified more primary immunodeficiency syndromes associated with T. marneffei infection in children. The higher case-fatality rate of T. marneffei infection in non-HIV-infected than HIV-infected patients might be related to delayed diagnosis due to the lack of clinical suspicion. Correction of the underlying immune defects and early use of antifungals are important treatment strategies. Clinicians should be familiar with the changing epidemiology and clinical management of T. marneffei infection among non-HIV-infected patients.

On the safety of radial artery cannulation

Abstract: The frequency of complications following radial artery cannulation for monitoring purposes was determined in 1,699 cardiovascular surgical patients and in 83 patients in whom cannulation was performed in another artery after failure at the radial site. Patients were examined and radial artery flow d

A randomised controlled trial comparing high-flow nasal oxygen with standard management for conscious sedation during bronchoscopy

Abstract: Traditional conscious sedation for endobronchial ultrasound procedures places patients at risk of desaturation, and high-flow nasal oxygen may reduce the risk. We designed a parallel-group randomised controlled trial of high-flow nasal oxygen at a flow rate of 30-70 l.min-1 via nasal cannulae, compared with standard oxygen therapy at 10 l.min-1 via a bite block in adults planned for conscious sedation for endobronchial ultrasound. The primary outcome was the proportion of patients experiencing desaturation (defined as SpO2 < 90%). Secondary outcomes included oxygen saturation after pre-oxygenation, lowest oxygen saturation during procedure, number of hypoxic episodes, duration of hypoxia, end-procedure end-tidal CO2 , satisfaction scores and complications. Thirty participants were allocated to each group. Baseline patient characteristics, procedure time and anaesthetic agents used were similar between the groups. Desaturation occurred in 4 out of 30 patients allocated to the high-flow nasal oxygen group, compared with 10 out of 30 allocated to the standard oxygenation group, a non-significant difference (p = 0.07) with intention to treat analysis. The difference was significant (p = 0.047) when using a per-protocol analysis. Oxygen saturation after pre-oxygenation and the lowest oxygen saturation during procedure were significantly higher in the high-flow nasal oxygen group compared with the standard oxygenation group; median (IQR [range] 100 (99-100 [93-100]) vs. 98 (97-99 [94-100]), p = 0.0001 and 97.5 (94-99 [77-100]) vs. 92 (88-95 [79-98]), p < 0.001, respectively. There were no differences in other secondary outcomes. Although high-flow nasal oxygen may prevent desaturation due to some causes, it does not protect against hypoxaemia in all circumstances.

Invasive home mechanical ventilation: living conditions and health-related quality of life.

Abstract: Background: The number of patients with invasive home mechanical ventilation (HMV) following unsuccessful weaning is steadily increasing, but little is known about the living conditions and health-related quality of life (HRQL) in these patients. Objectives: To establish detailed information on living conditions and HRQL in patients with invasive HMV. Methods: The Severe Respiratory Insufficiency Questionnaire (SRI) was used to measure specific HRQL aspects in addition to patient interviews on individual living conditions during home visits. Results: Thirty-two patients with lung disease, most prominently COPD (n = 18), and neuromuscular disorders (n = 14) were included. The overall mean SRI summary scale score (range 0-100) was 53 ± 16, with a broad range amongst individuals (23-86). Neuromuscular patients were younger than those with lung diseases (49 ± 18 vs. 67 ± 11 years; p Conclusions: Patients undergoing invasive HMV primarily following unsuccessful weaning reported an individual HRQL which, when taken together, was highly heterogeneous and ranged from very good to extremely bad. Older patients with COPD and more comorbidities are likely to have a worse HRQL than neuromuscular patients, while the living situation does not influence the HRQL.