Oystein Tronstad

Oxygen delivery through high-flow nasal cannulae increase end-expiratory lung volume and reduce respiratory rate in post-cardiac surgical patients.

BACKGROUND High-flow nasal cannulae (HFNCs) create positive oropharyngeal airway pressure, but it is unclear how their use affects lung volume. Electrical impedance tomography allows the assessment of changes in lung volume by measuring changes in lung impedance. Primary objectives were to investigate the effects of HFNC on airway pressure (P(aw)) and end-expiratory lung volume (EELV) and to identify any correlation between the two. Secondary objectives were to investigate the effects of HFNC on respiratory rate, dyspnoea, tidal volume, and oxygenation; and the interaction between BMI and EELV. METHODS Twenty patients prescribed HFNC post-cardiac surgery were investigated. Impedance measures, P(aw), ratio, respiratory rate, and modified Borg scores were recorded first on low-flow oxygen and then on HFNC. RESULTS A strong and significant correlation existed between P(aw) and end-expiratory lung impedance (EELI) (r=0.7, P<0.001). Compared with low-flow oxygen, HFNC significantly increased EELI by 25.6% [95% confidence interval (CI) 24.3, 26.9] and P(aw) by 3.0 cm H(2)O (95% CI 2.4, 3.7). Respiratory rate reduced by 3.4 bpm (95% CI 1.7, 5.2) with HFNC use, tidal impedance variation increased by 10.5% (95% CI 6.1, 18.3), and ratio improved by 30.6 mm Hg (95% CI 17.9, 43.3). A trend towards HFNC improving subjective dyspnoea scoring (P=0.023) was found. Increases in EELI were significantly influenced by BMI, with larger increases associated with higher BMIs (P<0.001). CONCLUSIONS This study suggests that HFNCs reduce respiratory rate and improve oxygenation by increasing both EELV and tidal volume and are most beneficial in patients with higher BMIs.

The silent and apparent neurological injury in transcatheter aortic valve implantation study (SANITY): concept, design and rationale.

BackgroundThe incidence of clinically apparent stroke in transcatheter aortic valve implantation (TAVI) exceeds that of any other procedure performed by interventional cardiologists and, in the index admission, occurs more than twice as frequently with TAVI than with surgical aortic valve replacement (SAVR). However, this represents only a small component of the vast burden of neurological injury that occurs during TAVI, with recent evidence suggesting that many strokes are clinically silent or only subtly apparent. Additionally, insult may manifest as slight neurocognitive dysfunction rather than overt neurological deficits. Characterisation of the incidence and underlying aetiology of these neurological events may lead to identification of currently unrecognised neuroprotective strategies.MethodsThe Silent and Apparent Neurological Injury in TAVI (SANITY) Study is a prospective, multicentre, observational study comparing the incidence of neurological injury after TAVI versus SAVR. It introduces an intensive, standardised, formal neurologic and neurocognitive disease assessment for all aortic valve recipients, regardless of intervention (SAVR, TAVI), valve-type (bioprosthetic, Edwards SAPIEN-XT) or access route (sternotomy, transfemoral, transapical or transaortic). Comprehensive monitoring of neurological insult will also be recorded to more fully define and compare the neurological burden of the procedures and identify targets for harm minimisation strategies.DiscussionThe SANITY study undertakes the most rigorous assessment of neurological injury reported in the literature to date. It attempts to accurately characterise the insult and sustained injury associated with both TAVI and SAVR in an attempt to advance understanding of this complication and associations thus allowing for improved patient selection and procedural modification.

Neurological Injury in Intermediate‐Risk Transcatheter Aortic Valve Implantation

Background The application of transcatheter aortic valve implantation (TAVI) to intermediate‐risk patients is a controversial issue. Of concern, neurological injury in this group remains poorly defined. Among high‐risk and inoperable patients, subclinical injury is reported on average in 75% undergoing the procedure. Although this attendant risk may be acceptable in higher‐risk patients, it may not be so in those of lower risk. Methods and Results Forty patients undergoing TAVI with the Edwards SAPIEN‐XT ™ prosthesis were prospectively studied. Patients were of intermediate surgical risk, with a mean±standard deviation Society of Thoracic Surgeons score of 5.1±2.5% and a EuroSCORE II of 4.8±2.4%; participant age was 82±7 years. Clinically apparent injury was assessed by serial National Institutes of Health Stroke Scale assessments, Montreal Cognitive Assessments (MoCA), and with the Confusion Assessment Method. These identified 1 (2.5%) minor stroke, 1 (2.5%) episode of postoperative delirium, and 2 patients (5%) with significant postoperative cognitive dysfunction. Subclinical neurological injury was assessed using brain magnetic resonance imaging, including diffusion‐weighted imaging (DWI) sequences preprocedure and at 3±1 days postprocedure. This identified 68 new DWI lesions present in 60% of participants, with a median±interquartile range of 1±3 lesions/patient and volumes of infarction of 24±19 μL/lesion and 89±218 μL/patient. DWI lesions were associated with a statistically significant reduction in early cognition (mean ΔMoCA −3.5±1.7) without effect on cognition, quality of life, or functional capacity at 6 months. Conclusions Objectively measured subclinical neurological injuries remain a concern in intermediate‐risk patients undergoing TAVI and are likely to manifest with early neurocognitive changes. Clinical Trial Registration URL: http://www.anzctr.org.au. Australian & New Zealand Clinical Trials Registry: ACTRN12613000083796.

A comparison of the effects of manual hyperinflation and ventilator hyperinflation on restoring end-expiratory lung volume after endotracheal suctioning: A pilot physiologic study

Purpose: Endotracheal suctioning (ES) of mechanically ventilated patients decreases end‐expiratory lung volume (EELV). Manual hyperinflation (MHI) and ventilator hyperinflation (VHI) may restore EELV post‐ES but it remains unknown which method is most effective. The primary aim was to compare the efficacy of MHI and VHI in restoring EELV post‐ES. Materials and methods: ES was performed on mechanically ventilated intensive care patients, followed by MHI or VHI, in a randomised crossover design. The washout period between interventions was 1 h. End‐expiratory lung impedance (EELI), measured by electrical impedance tomography, was recorded at baseline, during ES, during hyperinflation and 1, 5, 15 and 30 min post‐hyperinflation. Results: Nine participants were studied. ES decreased EELI by 1672z (95% CI, 1204 to 2140) from baseline. From baseline, MHI increased EELI by 1154z (95% CI, 977 to 1330) while VHI increased EELI by 769z (95% CI, 457 to 1080). Five minutes post‐VHI, EELI remained 528z (95% CI, 4 to 1053) above baseline. Fifteen minutes post‐MHI, EELI remained 351z (95% CI, 111 to 592) above baseline. At subsequent time‐points, EELI returned to baseline. Conclusions: MHI and VHI effectively restore EELV above baseline post‐ES and should be considered post suctioning.

Long-Term Survival and Health-Related Quality of Life in Adults After Extra Corporeal Membrane Oxygenation

BACKGROUND The study aims to determine long-term survival, health-related quality of life (HRQoL) and functional and physical outcomes of adult extra corporeal membrane oxygenation (ECMO) patients as there are limited and conflicting data in this area. METHODS All patients receiving ECMO from April 2009 until June 2014 at The Prince Charles Hospital, Brisbane had Kaplan Meier survival calculated. Quality of life (QoL) was assessed using the Short Form Health Survey (SF-36v2), EQ5D-5L, The Frenchay Activities Index (FAI) and a return to work survey. From December 2011, these measures and 6-minute walk distance (6MWD) were assessed at hospital discharge and 12 months post-discharge. RESULTS Seventy-seven (77) patients (45 veno-arterial and 32 veno-venous) received ECMO of whom 47/77 (61%) survived to hospital discharge. There were no deaths recorded in those discharged alive from the intensive care unit at median follow-up time 1,011days (range 227-2,014 days). Mean SF-36 scores (n=33) and EQ5D were assessed at a median of 606days after hospital discharge. SF-36 scores were significantly (p<0.05) worse than age-matched norms in all domains except vitality, bodily pain and mental health. Thirteen (13) (39%) participants had persistent problems with mobility and usual activity as measured by EQ5D. At 12 months post-ECMO, 6MWD was 531(IQR:397.3-626.8)m; 72% (IQR:53.2-77.6%) predicted but had improved by 223m (p=0.002) when compared to baseline. Nineteen (19) of 20 participants who had been employed pre-ECMO had returned to work. CONCLUSIONS All ECMO patients discharged from hospital were alive at follow-up. Despite improvements in physical measures and HRQoL, long-term functional deficits persist when compared to that of aged- and sex-matched norms.

When is it safe to exercise mechanically ventilated patients in the intensive care unit? An evaluation of consensus recommendations in a cardiothoracic setting

Rationale Consensus recommendations have been developed to guide exercise rehabilitation of mechanically ventilated patients in the intensive care unit. Objective This study aimed to investigate the safety of exercise rehabilitation of mechanically ventilated patients and evaluate the consensus recommendations. Methods This was a prospective, single‐centre, cohort study conducted in a specialist cardiothoracic intensive care unit of a tertiary, university affiliated hospital in Australia. Results 91 mechanically ventilated participants; 54 (59.3%) male; mean age of 56.52 (16.3) years; were studied with 809 occasions of service recorded. Ten (0.0182%) minor adverse events were recorded, with only one adverse event occurring when a patient was receiving moderate level of vasoactive support. Conclusions The consensus recommendations are a useful tool in guiding safe exercise rehabilitation of mechanically ventilated patients. Our findings suggest that there is further scope to safely commence exercise rehabilitation in patients receiving vasoactive support.