Maintaining the health of people with and without COVID-19 during isolation: a case study.

This case study evaluated the effects of a health package (HP) of a light intensity individualised exercise program and advice on anxiety management and nutrition, on the physical and mental health of people with or without COVID-19, who were quarantined in hotels used as Special Health Accommodation and admitted to the Royal Prince Alfred Virtual Hospital, Sydney during the COVID-19 pandemic. After initial screening and consenting, participants completed three surveys: Depression, Anxiety, Stress Scale; Brief Fatigue Inventory; and the European Quality of Life 5-Dimensions 5-Levels, and were provided with the HP for the duration of their quarantine. The three surveys and a participant reported experience measure were completed prior to discharge. The HP for people in quarantine demonstrated stability of health outcomes and reduction in fatigue. Most participants reported that the HP helped them cope with isolation. Provision of a HP during quarantine could be useful to support physical and mental health.

RECITAL: a non-inferiority randomised control trial evaluating a virtual fracture clinic compared with in-person care for people with simple fractures (study protocol).

INTRODUCTION: Most simple undisplaced fractures can be managed without surgery by immobilising the limb with a splint, prescribing medication for pain, and providing advice and early rehabilitation. Recent systematic reviews based on retrospective observational studies have reported that virtual fracture clinics can deliver follow-up care that is safe and cost-effective. However, no randomised controlled trial has investigated if a virtual fracture clinic can provide non-inferior physical function outcomes compared with an in-person clinic for patients with simple fractures. METHODS AND ANALYSIS: 312 participants will be recruited from 2 metropolitan hospitals located in Sydney, Australia. Adult patients will be eligible if they have an acute simple fracture that can be managed with a removable splint and is deemed appropriate for follow-up at either the virtual or in-person fracture clinic by an orthopaedic doctor. Patients will not be eligible if they have a complex fracture that requires a cast or surgery. Eligible participants will be randomised to receive their follow-up care either at the virtual or the in-person fracture clinic. Participants at the virtual fracture clinic will be reviewed within 5 days of receiving a referral through video calls with a physiotherapist. Participants at the in-person fracture clinic will be reviewed by an orthopaedic doctor within 7-10 days of receiving a referral. The primary outcome will be the patient's function measured using the Patient-Specific Functional Scale at 12 weeks. Secondary outcomes will include health-related quality of life, patient-reported experiences, pain, health cost, healthcare utilisation, medication use, adverse events, emergency department representations and surgery. ETHICS AND DISSEMINATION: The study has been approved by the Sydney Local Health District Ethics Review Committee (RPAH Zone) (X23-0200 and 2023/ETH01038). The trial results will be submitted for publication in a reputable international journal and will be presented at professional conferences. TRIAL REGISTRATION NUMBER: ACTRN12623000934640.

Fighting the Same Battles on a New Battleground: Embedding Technologies in a Virtual Care Environment.

The pandemic necessitated the rapid design, development and implementation of technologies to allow remote monitoring of COVID-19 patients at home. This study aimed to explore the environmental barriers and facilitators to the successful development and implementation of virtual care technologies in this fast-paced context. We interviewed eight staff at a virtual hospital in Australia. We found key facilitators to be a learning organizational culture and strong leadership support. Barriers included interoperability issues, legislative constraints and unrealistic clinician expectations. Also, we found that a combination of hot-desking and the lack of single sign on in the virtual care environment, was reported to create additional work for staff. Overall, despite this unique context, our findings are consistent with prior work examining design and implementation of healthcare technologies. The fast pace and high-pressure environment appeared to magnify previously reported barriers, but also cultivate and foster a learning culture.

Impact of cystic fibrosis multidisciplinary virtual clinics on patient experience, time commitments and costs.

BACKGROUND AND AIMS: The experience of outpatient care may differ for select patient groups. This prospective study evaluates the adult patient experience of multidisciplinary outpatient cystic fibrosis (CF) care with videoconferencing through telehealth compared with face-to-face care the year prior. METHODS: People with CF without a lung transplant were recruited. Patient-reported outcomes were obtained at commencement and 12 months into the study, reflecting both their face-to-face and telehealth through videoconferencing experience, respectively. Three patient cohorts were analysed: (i) participants with a regional residence, (ii) participants with a nonregional including metropolitan residence and (iii) participants with colonised multiresistant microbiota. RESULTS: Seventy-four patients were enrolled in the study (mean age, 37 ± 11 years; 50% male; mean forced expiratory volume in the first second of expiration, 60% [standard deviation, 23]) between February 2020 and May 2021. No differences between models were observed in the participants' rating of the health care team, general and mental health rating, and their confidence in handling treatment plans at home. No between-group differences in the Cystic Fibrosis Questionnaire - Revised (CFQ-R) were observed. Travel duration and the cost of attending a clinic was significantly reduced, particularly for the regional group (4 h, AU$108 per clinic; P < 0.05). A total of 93% respondents preferred to continue with a hybrid approach. CONCLUSION: In this pilot study, participants' experience of care and quality of life were no different with face-to-face and virtual care between the groups. Time and cost-savings, particularly for patients living in regional areas, were observed. Most participants preferred to continue with a hybrid model for outpatient care.

Patient and Clinician Perceptions of the Pulse Oximeter in a Remote Monitoring Setting for COVID-19: Qualitative Study.

BACKGROUND: As a response to the COVID-19 pandemic, the Sydney Local Health District in New South Wales, Australia, launched the rpavirtual program, the first full-scale virtual hospital in Australia, to remotely monitor and follow up stable patients with COVID-19. As part of the intervention, a pulse oximeter wearable device was delivered to patients to monitor their oxygen saturation levels, a critical indicator of COVID-19 patient deterioration. Understanding users' perceptions toward the device is fundamental to assessing its usability and acceptability and contributing to the effectiveness of the intervention, but no research to date has explored the user experience of the pulse oximeter for remote monitoring in this setting. OBJECTIVE: This study aimed to explore the use, performance, and acceptability of the pulse oximeter by clinicians and patients in rpavirtual during COVID-19. METHODS: Semistructured interviews and usability testing were conducted. Stable adult patients with COVID-19 (aged ≥18 years) who used the pulse oximeter and were monitored by rpavirtual, and rpavirtual clinicians monitoring these patients were interviewed. Clinicians could be nurses, doctors, or staff who were part of the team that assisted patients with the use of the pulse oximeter. Usability testing was conducted with patients who had the pulse oximeter when they were contacted. Interviews were coded using the Theoretical Framework of Acceptability. Usability testing was conducted using a think-aloud protocol. Data were collected until saturation was reached. RESULTS: Twenty-one patients (average age 51, SD 13 years) and 15 clinicians (average age 41, SD 11 years) completed the interview. Eight patients (average age 51, SD 13 years) completed the usability testing. All participants liked the device and thought it was easy to use. They also had a good understanding of how to use the device and the device's purpose. Patients' age and device use-related characteristics (eg, the warmth of hands and hand steadiness) were identified by users as factors negatively impacting the accurate use of the pulse oximeter. CONCLUSIONS: Patients and clinicians had very positive perceptions of the pulse oximeter for COVID-19 remote monitoring, indicating high acceptability and usability of the device. However, factors that may impact the accuracy of the device should be considered when delivering interventions using the pulse oximeter for remote monitoring. Targeted instructions about the use of the device may be necessary for specific populations (eg, older people and patients unfamiliar with technology). Further research should focus on the integration of the pulse oximeter data into electronic medical records for real-time and secure patient monitoring.

Clinical characteristics and predictors for hospitalisation during the initial phases of the Delta variant COVID-19 outbreak in Sydney, Australia.

OBJECTIVES: The COVID-19 Delta variant of concern continues to pose significant challenges to health systems globally, with increased transmissibility and different patient populations affected. In Sydney, a virtual model of care was implemented in response to the COVID-19 pandemic and Special Health Accommodation (SHA) was made available for community patients with COVID-19 who could not isolate at home or needed health support. METHODS: This retrospective observational cohort study of all patients with COVID-19 Delta variant in SHA during the initial phases of the Delta variant outbreak in Sydney describes the demographic and clinical characteristics of patients with Delta variant COVID-19 and determines predictors of need for in-patient hospital admission. RESULTS: Data from 794 patients were analysed. One hundred and fifty-seven patients (19.8%) were transferred to ED. Of those, 125 were admitted to an in-patient unit (admission rate from ED 79.6%), and of these 30 (24%) went to ICU and seven were intubated. Two patients died within the follow-up period. Age >40 years, obesity, and presence of fever (temperature >37.5°C), hypoxia (oxygen saturation <95%), tachycardia or gastrointestinal symptoms on initial assessment in SHA were independent predictors of in-patient admission with an AUROC of 0.78 (95% confidence interval 0.73, 0.82). CONCLUSIONS: Initial symptoms and vital signs were just as predictive for short-term deterioration as age and pre-existing comorbidities and should be included in future risk prediction models for COVID-19. Based on this, we derive a proposed risk prediction score that incorporates these predictors with further validation required.

Sydney Local Health District's Integrated Response to the COVID-19 Pandemic: A Descriptive Study.

Introduction: Sydney Local Health District (SLHD) is a local health district in the state of New South Wales in Australia responsible for providing health services to the centre and inner west of the Sydney metropolitan area. SLHD adopted, during the COVID-19 pandemic, an integrated virtual and community care approach to manage quarantine and protect the health and wellbeing of the population. Description: The case study describes the roles of the different agencies and teams in the first six months of the pandemic across four key functions of 1) rapid screening and testing; 2) reaching the community; 3) effective quarantine and ongoing care; and 4) infrastructure, pathology and staff education. Discussion: The "whole of system" approach proved to be an effective method of delivering care that reduced community anxiety, improved and created relationships between existing and new internal and external stakeholders, and changed the community and health sector's perspective on the importance of virtual care. Conclusion: This case study describes the importance of well-integrated, decentralised and funded public health system in response to the COVID-19 pandemic.

Inequity in Access and Delivery of Virtual Care Interventions: A Scoping Review.

The objectives of this review were to map and summarize the existing evidence from a global perspective about inequity in access and delivery of virtual care interventions and to identify strategies that may be adopted by virtual care services to address these inequities. We searched MEDLINE, EMBASE, and CINAHL using both medical subject headings (MeSH) and free-text keywords for empirical studies exploring inequity in ambulatory services offered virtually. Forty-one studies were included, most of them cross-sectional in design. Included studies were extracted using a customized extraction tool, and descriptive analysis was performed. The review identified widespread differences in accessing and using virtual care interventions among cultural and ethnic minorities, older people, socioeconomically disadvantaged groups, people with limited digital and/or health literacy, and those with limited access to digital devices and good connectivity. Potential solutions addressing these barriers identified in the review included having digitally literate caregivers present during virtual care appointments, conducting virtual care appointments in culturally sensitive manner, and having a focus on enhancing patients' digital literacy. We identified evidence-based practices for virtual care interventions to ensure equity in access and delivery for their virtual care patients.

Understanding for whom, how and why Sydney Local Health District's Integrated Response was Effective in Addressing COVID-19: A Critical Realist Qualitative Study.

INTRODUCTION: Australia has been comparatively effective in preventing the transmission of COVID-19. The Sydney Local Health District [SLHD] used a "whole of health" integrated approach to respond to the pandemic. The aim of this study was to understand for whom, how and why this response worked, to inform a sustainable system transformation. METHODS: A critical realist qualitative study was conducted with 20 purposively selected key informants. Data were collected through in-depth interviews and analysed using thematic analysis guided by abduction and retroduction. The five strategies of the WHO integrated people-centred health services framework was used to guide the overall study. RESULTS: An enabling environment of a strong governance, emergency preparedness, a committed and adaptable workforce, and a strong core infrastructure underpinned SLHD's effective response. With a culture of embracing innovation, the district adapted virtual care to effectively quarantine people through their special health accommodation, and coordinate care across tertiary and community services. The established interagency relationships prior to the pandemic, enabled service directors to quickly integrate their services, which empowered and engaged the community [and staff], working across relevant sectors to provide care "where the people are"; reaching marginalised populations, and reducing community transmission. DISCUSSION AND CONCLUSION: The SLHD's progress towards a 'whole of health' approach, empowered and enabled the district to effectively work within and across sectors to address the pandemic in a people-centred manner. Sustaining the contextual conditions and mechanisms, that facilitated effective integration, will be beneficial beyond the pandemic.

rpavirtual: Key lessons in healthcare organisational resilience in the time of COVID-19.

The COVID-19 pandemic is an unfolding crisis which is continually testing the resilience of healthcare organisations. In this context, a key requirement for executives, managers and frontline staff is continually adapting, learning and coping with complexity under pressure to deliver high quality and safe care. Sydney Local Health District has responded to the COVID-19 crisis, in part, through the pivoting of rpavirtual, a newly established virtual health service, to deliver an innovative model of care in a clinically rigorous and safe manner. Through reviewing the rapid evolution of rpavirtual's purpose, implementation challenges and impact, we investigate how it has displayed resilience and derive key lessons for health organisations.

The Virtual Care Experience of Patients Diagnosed With COVID-19.

Virtual models of care are seen as a sustainable solution to the growing demand for health care. This paper analyses the experience of virtual care among patients diagnosed with COVID-19 in home isolation or health hotel quarantine using a patient-reported experience questionnaire. Results found that patients respond well to virtual models of care during a pandemic. Lessons learned can inform future developments of virtual care models.

Virtual Health Care for Community Management of Patients With COVID-19 in Australia: Observational Cohort Study.

BACKGROUND: Australia has successfully controlled the COVID-19 pandemic. Similar to other high-income countries, Australia has extensively used telehealth services. Virtual health care, including telemedicine in combination with remote patient monitoring, has been implemented in certain settings as part of new models of care that are aimed at managing patients with COVID-19 outside the hospital setting. OBJECTIVE: This study aimed to describe the implementation of and early experience with virtual health care for community management of patients with COVID-19. METHODS: This observational cohort study was conducted with patients with COVID-19 who availed of a large Australian metropolitan health service with an established virtual health care program capable of monitoring patients remotely. We included patients with COVID-19 who received the health service, could self-isolate safely, did not require immediate admission to an in-patient setting, had no major active comorbid illness, and could be managed at home or at other suitable sites. Skin temperature, pulse rate, and blood oxygen saturation were remotely monitored. The primary outcome measures were care escalation rates, including emergency department presentation, and hospital admission. RESULTS: During March 11-29, 2020, a total of 162 of 173 (93.6%) patients with COVID-19 (median age 38 years, range 11-79 years), who were diagnosed locally, were enrolled in the virtual health care program. For 62 of 162 (38.3%) patients discharged during this period, the median length of stay was 8 (range 1-17) days. The peak of 100 prevalent patients equated to approximately 25 patients per registered nurse per shift. Patients were contacted a median of 16 (range 1-30) times during this period. Video consultations (n=1902, 66.3%) comprised most of the patient contacts, and 132 (81.5%) patients were monitored remotely. Care escalation rates were low, with an ambulance attendance rate of 3% (n=5), emergency department attendance rate of 2.5% (n=4), and hospital admission rate of 1.9% (n=3). No deaths were recorded. CONCLUSIONS: Community-based virtual health care is safe for managing most patients with COVID-19 and can be rapidly implemented in an urban Australian setting for pandemic management. Health services implementing virtual health care should anticipate challenges associated with rapid technology deployments and provide adequate support to resolve them, including strategies to support the use of health information technologies among consumers.

Control of COVID-19 in Australia through quarantine: the role of special health accommodation (SHA) in New South Wales, Australia.

BACKGROUND: The first COVID-19 cases were diagnosed in Australia on 25 January 2020. Initial epidiemiology showed that the majority of cases were in returned travellers from overseas. One aspect of Public Health response was to introduce compulsory 14 day quarantine for all travellers returning to New South Wales (NSW) by air or sea in Special Health Accommodation (SHA). We aim to outline the establishment of a specialised health quarantine accommodation service in the context of the COVID-19 pandemic, and describe the first month of COVID-19 screening. METHODS: The SHA was established with a comprehensive governance structure, remote clinical management through Royal Prince Alfred Virtual Hospital (rpavirtual) and site management with health care workers, NSW Police and accommodation staff. RESULTS: From 29 March to 29 April 2020, 373 returning travellers were admitted to the SHA from Sydney Airport. 88 (26.1%) of those swabbed were positive for SARS-CoV 2. The day of diagnosis of COVID-19 varied from Day 1 to Day 13, with 63.6% (n = 56) of these in the first week of quarantine. 50% of the people in the SHA were referred to rpavirtual for ongoing clinical management. Seven people required admission to hospital for ongoing clinical care. CONCLUSION: The Public Health response to COVID-19 in Australia included early and increased case detection through testing, tracing of contacts of confirmed cases, social distancing and prohibition of gatherings. In addition to these measures, the introduction of mandated quarantine for travellers to Australia was integral to the successful containment of COVID-19 in NSW and Australia through the prevention of transmission locally and interstate from returning travellers.

Theoretical Investigation of the Atmospheric Photochemistry of Glyoxylic Acid in the Gas Phase.

The photochemistry of glyoxylic acid (HC(O)C(O)OH) is explored in the near UV in both the singlet (S1/S0) and triplet (T1) manifolds using density functional theory (M06-2X/aug-cc-pVTZ) to reach an overall mechanistic picture of the atmospherically relevant photochemistry in the gas phase. The calculated energies and structures are also used in RRKM kinetics calculations to compare the relative reaction rates on each of these electronic states. The major photolysis pathways are two possible photodecarboxylation reactions: direct C-C bond cleavage (Norrish Type I reaction) and ß-hydrogen transfer followed by CO2 loss. These results indicate that from λ = 350-380 nm both photodecarboxylation pathways can occur following intersystem crossing to the T1 surface. However, hydrogen transfer-decarboxylation initiated on S1 becomes increasingly important at λ < 350 nm. At the lower energy UV wavelengths available in the atmosphere (λ = 380-400 nm), reactions can only occur in S0 where concerted hydrogen transfer-decarboxylation is the dominant dissociation pathway with some minor contributions from CO loss/decarbonylation reactions.

Designing Initiatives for Vulnerable Families: From Theory to Design in Sydney, Australia.

INTRODUCTION: Intergenerational cycles of poverty, violence and crime, poor education and employment opportunities, psychopathology, and poor lifestyle and health behaviours require innovative models of health care delivery to break them. We describe a programme of research informed service development targeting vulnerable families in inner metropolitan Sydney, Australia that is designed to build and confirm a "Theory of Neighbourhood Context, Stress, Depression, and the Developmental Origins of Health and Disease (DOHaD)". We describe the development of an intervention design and business case that drew on earlier realist causal and programme theoretical work. METHODS: Realist causal and programme theory were used to inform the collaborative design of initiatives for vulnerable families. The collaborative design process included: identification of desirable and undesirable outcomes and contextual factors, consultation forums, interagency planning, and development of a service proposal. RESULTS: The design elements included: perinatal coordination, sustained home visiting, integrated service model development, two place-based hubs, health promotion and strengthened research and analysis capability. CONCLUSIONS: We demonstrate here the design of interventions for vulnerable families in Sydney utilising translational research from previous realist causal and program theory building to operational service design. We have identified the importance of our earlier analysis of underlying causal mechanisms and related programme mechanisms for identifying the elements for the full intervention design. The application of theory added rigour to the design of the integrated care initiatives. In applying the theory to the local situation the analysis took into account: the role of the local agencies; evidence of program effectiveness; determinants and outcomes for local children and their families; the current deployment of service resources; and insights from front-line staff and interagency partners.

Designing an Integrated Care Initiative for Vulnerable Families: Operationalisation of Realist Causal and Programme Theory, Sydney Australia.

INTRODUCTION: In July 2015 Sydney Local Health District (SLHD) implemented an integrated care initiative for vulnerable families in the Inner West region of Sydney, Australia. The initiative was designed as a cross-agency care coordination network that would ensure that vulnerable families: had their complex health and social needs met; kept themselves and their children safe; and were connected to society. We will describe the development of the design that drew on earlier realist causal and program theoretical work. METHODS: Realist causal and program theory were used to inform the collaborative design of an initiative for vulnerable families. The collaborative design process included: identification of desirable and undesirable outcomes and contextual factors, stakeholder consultation, interagency planning, and development of a service proposal. RESULTS: The design elements included: identification of vulnerable family cohorts; care coordination; evidence-informed intervention(s); general practice engagement and support; family health improvement; placed-based neighbourhood initiatives; interagency system change and collaborative planning; monitoring of individual and family outcomes; and evaluation. CONCLUSIONS: The design study described advances toward the implementation of a whole-of-government integrated health and social care initiative. The initiative was designed as a cross-agency care coordination network that would ensure that vulnerable families: had their complex health and social needs met; kept themselves and their children safe; and were connected to society. In so doing we aim to break intergenerational cycles of poverty, violence and crime, poor education and employment opportunities, psychopathology, and poor lifestyle and health behaviours, through strengthening family resilience, improving access to services, and addressing the social determinants of health and wellbeing.

Implementation, Mechanisms of Effect and Context of an Integrated Care Intervention for Vulnerable Families in Central Sydney Australia: A Research and Evaluation Protocol.

INTRODUCTION: In March 2014, the New South Wales (NSW) Government (Australia) announced the NSW Integrated Care Strategy. In response, a family-centred, population-based, integrated care initiative for vulnerable families and their children in Sydney, Australia was developed. The initiative was called Healthy Homes and Neighbourhoods. A realist translational social epidemiology programme of research and collaborative design is at the foundation of its evaluation. THEORY AND METHOD: The UK Medical Research Council (MRC) Framework for evaluating complex health interventions was adapted. This has four components, namely 1) development, 2) feasibility/piloting, 3) evaluation and 4) implementation. We adapted the Framework to include: critical realist, theory driven, and continuous improvement approaches. The modified Framework underpins this research and evaluation protocol for Healthy Homes and Neighbourhoods. DISCUSSION: The NSW Health Monitoring and Evaluation Framework did not make provisions for assessment of the programme layers of context, or the effect of programme mechanism at each level. We therefore developed a multilevel approach that uses mixed-method research to examine not only outcomes, but also what is working for whom and why.

Linking two randomised controlled trials for Healthy Beginnings©: optimising early obesity prevention programs for children under 3 years.

BACKGROUND: Beginning in 2017 we have conducted a 3-arm randomised controlled trial (RCT) to determine the effectiveness of an early obesity intervention in the first two years of life using either telephone or Short Message Service (SMS) support for mothers. The trial recruited 1155 mothers from their third trimester of pregnancy. This protocol is for a new trial to build on the existing trial using the mother-child dyads retained at 24 months for recruitment to the new RCT. The aim of this new trial is to test whether use of a combination of telephone and SMS interventions is effective in promoting healthy eating and physical activity, as well as reducing child body mass index (BMI) at 3 years of age. METHODS: We will conduct a parallel RCT with an estimated sample of 750 mother-child dyads retained from the existing trial at 24 months. Mothers who completed the 24 months survey, including a telephone survey and measurement of child's height and weight will be invited to participate in the new trial. Informed consent will be obtained at the 24 months survey. The participating mother-child dyads will then be randomly allocated to the intervention (combined telephone and text messaging intervention) or the control group. The intervention will comprise three staged telephone consultations and text messages after each of the three intervention booklets is mailed to mothers at specific time-points between two and three years of child age. The main trial outcome measures include a) BMI and BMI z-score measured at 36 months, b) diet, physical activity and screen time c) cost-effectiveness, and d) feasibility and acceptability of the intervention. DISCUSSION: This unique opportunity to link two studies will expedite project start up time, utilise existing research infrastructure and systems to run the study, and optimise the use of an already engaged population of study participants. It can address a significant knowledge gap regarding early obesity prevention for children aged 2 to 3 years. The feasibility and effectiveness of the combined telephone and SMS intervention will indicate whether this is a scaleable, broad-reach and low-cost early obesity intervention. TRIAL REGISTRATION: The trial was registered with the Australian Clinical Trial Registry ( ACTRN12618001571268 ) on 20/09/2018.

Dynamics and quantum yields of H2 + CH2CO as a primary photolysis channel in CH3CHO.

The first experimental observation of the primary photochemical channel of acetaldehyde leading to the formation of ketene (CH2CO) and hydrogen (H2) molecular products is reported. Acetaldehyde (CH3CHO) was photolysed in a molecular beam at 305.6 nm and the resulting H2 product characterized using velocity-map ion (VMI) imaging. Resonance-enhanced multiphoton ionization (REMPI), via two-photon excitation to the double-well EF 1Σ state, was used to state-selectively ionize the H2 and determine angular momentum distributions for H2 (ν = 0) and H2 (ν = 1). Velocity-map ion images were obtained for H2 (ν = 0 and 1, J = 5), allowing the total translational energy release of the photodissociation process to be determined. Following photolysis of CH3CHO in a gas cell, the CH2CO co-fragment was identified, using Fourier transform infrared spectroscopy, by its characteristic infrared absorption at 2150 cm-1. The measured quantum yield of the CH2CO + H2 product channel at 305.0 nm is φ = 0.0075 ± 0.0025 for both 15 Torr of neat CH3CHO and a mixture with 745 Torr of N2. Although small, this result has implications for the atmospheric photochemistry of carbonyls and this reaction represents a new tropospheric source of H2. Quasi-classical trajectory (QCT) simulations on a zero-point energy corrected reaction-path potential are also performed. The experimental REMPI and VMI image distributions are not consistent with the QCT simulations, indicating a non reaction-path mechanism should be considered.

Photo-tautomerization of acetaldehyde as a photochemical source of formic acid in the troposphere.

Organic acids play a key role in the troposphere, contributing to atmospheric aqueous-phase chemistry, aerosol formation, and precipitation acidity. Atmospheric models currently account for less than half the observed, globally averaged formic acid loading. Here we report that acetaldehyde photo-tautomerizes to vinyl alcohol under atmospherically relevant pressures of nitrogen, in the actinic wavelength range, λ = 300-330 nm, with measured quantum yields of 2-25%. Recent theoretical kinetics studies show hydroxyl-initiated oxidation of vinyl alcohol produces formic acid. Adding these pathways to an atmospheric chemistry box model (Master Chemical Mechanism) demonstrates increased formic acid concentrations by a factor of ~1.7 in the polluted troposphere and a factor of ~3 under pristine conditions. Incorporating this mechanism into the GEOS-Chem 3D global chemical transport model reveals an estimated 7% contribution to worldwide formic acid production, with up to 60% of the total modeled formic acid production over oceans arising from photo-tautomerization.