Smart Maintenance and Human Factor Modeling for Aircraft Safety

The global pandemic has significantly accelerated the need for remote monitoring and diagnostics of airline operations and assets. As passenger and cargo flights are impacted from all directions, maintenance can be the steady, reliable part of the puzzle that helps get things back on track. This chapter explores the aircraft safety challenges that can be addressed with better maintenance technology and human factor modeling. Aircraft safety relies heavily on maintenance. During the COVID-19 recovery phase, airline operators need to focus on the application of a robust management of change process to implement better maintenance technology, identify new aircraft safety risks, determine effective mitigation measures, and implement strategies for deploying changes accordingly. For years aircraft maintenance routines have been carried out in the same manner without change, now with international travel restrictions, social distancing, reduced staff, and limited maintenance funding, the need for smarter ways of doing maintenance is obvious. In this regard smart technology has an important role to play. For instance, IoT data generates the capacity for predictive aircraft maintenance, AI introduces the capacity for smart, deep-learning machines to make predictive maintenance more accurate, actionable, and automatic. AI-enabled predictive maintenance leverages IoT data to predict and prevent aircraft failures. While smart technology enhances aircraft safety through better maintenance performance on the one hand, there are technical and human factor problems induced by COVID-19 on the other. The Safe Aircraft System (SAS) model, based on the Dirty Dozen and SHELL human factor models, is an initiative proposed to minimize such COVID-19 problems. This work shows through a case illustration that SAS modeling is a useful tool in identifying potential hazards/consequences associated with any major or minor changes in flight operations. Hence the synergistic effect of smart maintenance and the SAS model in enhancing aircraft system safety are demonstrated. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

Validation of the one minute sit to stand test(1MSTS)for identification of exertional oxygen desaturation in chronic respiratory disease

Background: Despite limited validation data (Kalin et al Systematic Reviews 2021 Mar 16;10(1):77), the 1MSTS was widely used as a rapid exercise test to assess exertional oxygen desaturation during the COVID-19 pandemic. Aim(s): To assess the diagnostic accuracy of the 1MSTS to detect significant exertional oxygen desaturation in people with chronic respiratory disease. Method(s): 99 patients referred for pulmonary rehabilitation assessment were assessed for ambulatory oxygen requirements using a shuttle walk test according to British Thoracic Society Guidelines for Home Oxygen Use. Exertional oxygen desaturation was defined as a drop in oxygen saturations (SpO ) of >=4% with nadir <90%. 1MSTS was conducted in each participant by an assessor blinded to ambulatory oxygen assessment results. Result(s): Mean(SD) age 68.9(11.4) years, 59%COPD, 13%ILD. 21% demonstrated significant exertional oxygen desaturation. Using a drop of SpO >=4% to nadir <90% threshold, the 1MSTS only identified 6 out of 21 patients with exertional oxygen desaturation (sensitivity 29%). Simplifying the threshold to a drop in SpO of >=4% alone during 1MSTS improved sensitivity to 81% with specificity of 87%. Conclusion(s): Using a threshold of drop in SpO of >=4%, the 1MSTS test had reasonable sensitivity and specificity identifying significant exertional oxygen desaturation in patients with chronic respiratory disease.

The impact of comorbidities on recovery following hospitalisation from COVID-19

Introduction: It is unknown how pre-existing comorbidities affect recovery after a hospital admission for COVID-19. Aim(s): To explore the impact of comorbidities on symptoms, exercise capacity and QoL 5 months after a hospital admission for COVID-19. Method(s): Patients hospitalised with COVID-19 were recruited to an observational longitudinal cohort study (PHOSPCOVID). Patients were categorised into three comorbid categories (0, 1, >=2). The Incremental Shuttle Walking Test (ISWT), FACIT, Dyspnoea-12 and the EQ5D-VAS were assessed 5 months post-discharge. Patient perceived preadmission EQ5D-VAS scores were collected retrospectively. One-way ANOVA were used to compare groups. Result(s): 1516 patients completed the assessment: 61% male, mean[SD];age 58[12], length of stay 14[19] days, BMI 32[7], number of comorbidities 2[2] with 813(53%) patients having >=2 comorbidities. The EQ5D was reduced pre admission to 5 months for all groups (p<0.01), however the difference between pre EQ5D-VAS and at 5 months was similar between groups (p=0.18). There was a significant difference in ISWT (m, %), FACIT and EQ5D between those that had >=2 comorbidities compared to no, and 1 comorbidity (p<0.01)(table 1). Conclusion(s): Although patients with more co-morbidities have a greater symptom burden and lower exercise capacity at five months post-discharge, important morbidity also persists in adults without pre-existing co-morbidity.

Exercise tolerance and limiting symptoms 5 and 12 months after hospital discharge from COVID-19

Introduction: Exercise tolerance, a strong predictor of morbidity and mortality, is reduced 2-3 months after a COVID19 hospitalisation. However, the long-term effects of COVID-19 on exercise tolerance in this population remain largely unknown. Aim(s): This study aimed to assess exercise tolerance 5 and 12 months after hospital discharge for COVID-19 and compare groups according to the limiting symptom. Method(s): Patients discharged from hospital after COVID-19 were invited to a multicentre long-term follow up study (PHOSP-COVID). 378 participants (58 +/- 12 y;BMI: 32.2 +/- 7.4 kg/m2;143 [38%] female;106 [28%] had received mechanical ventilation) performed an incremental shuttle walk test (ISWT) to intolerance 5 and 12 months after hospital discharge. Self-reported reason for intolerance was recorded. Result(s): ISWT distance 5 months post-discharge was 465 +/- 263 m (63 +/- 29% predicted;heart rate: 66 +/- 17% agepredicted max). At exercise intolerance, modified Borg ratings of perceived exertion and breathlessness were 3 +/- 2 and 4 +/- 2, respectively. Participants terminated the test due to breathlessness (n = 107;28%), leg fatigue (38;10%), breathlessness and leg fatigue (85;23%) or other reason (148;39%). There was no increase in ISWT distance 5 to 12 months post-hospital discharge (12 months;476 +/- 264 m;64 +/- 29% predicted;p = 0.09), with no differences between participants based on their reason for exercise intolerance at 5 months (p = 0.29). Conclusion(s): Between 5 and 12 months after hospital discharge, exercise tolerance did not increase, irrespective of patient reported exercise limitations, underscoring the need for effective rehabilitation strategies in this population.

Integrating home-based exercise training within a hospital at home service for patients hospitalised with acute exacerbations of COPD: a mixed methods feasibility study

BackgroundThe uptake of face-to-face supervised outpatient-based pulmonary rehabilitation (PR) following hospitalisation for an acute exacerbation of COPD (AECOPD) is low. One commonly cited barrier is travel. Home-based PR may be an alternative setting. The aim of this study was to determine whether a co-designed home-based exercise training intervention, delivered alongside usual hospital at home (HaH) care post-hospitalisation for an AECOPD, is acceptable and feasible.MethodsA mixed method feasibility study was conducted including a parallel, two-group randomised controlled trial (RCT) (control group: usual HaH care;intervention group: usual care plus home-based exercise training) with convergent qualitative components (interviews: patients, family carers, researchers;focus groups: healthcare professionals [HCPs]).Results16/132 patients screened were recruited to the RCT with 8 allocated to each group and one withdrawn prior to receiving HaH care (56% were male, mean [SD] age: 74 [9] years, median [IQR] FEV1: 29 [21, 40] percent predicted, 87% with an eMRC dyspnoea score of 4, 5a or 5b). Four vs eight and four vs seven attended four week and three-month follow-up assessments in the control and intervention groups respectively. There was no evidence of contamination in the control group. 25% of patients allocated to the intervention group were unable to receive the intervention due to Covid-19. The questionnaire-based outcomes were more complete and appeared more acceptable to patients than physical measures, with very poor uptake for physical activity monitoring via accelerometery. Qualitative findings (interviews: five patients, two family carers, four researchers;focus groups: PR and HaH service HCPs) demonstrated that trial and intervention processes were acceptable, clinically beneficial and safe, but did not explain the disparity between questionnaire-based vs physical outcome measure completion rates.ConclusionThe findings suggest an efficacy trial which investigates home-based exercise training integrated within a HaH service following hospitalisation for an AECOPD would be safe and acceptable to patients, family carers, HCPs and researchers alike, and is qualitatively felt to be of clinical benefit. However, additional piloting is required to optimise intervention fidelity and study processes given the low recruitment rates, high drop out of the control group and poor uptake of some physical assessments.

Upper Limb Function in Survivors of COVID-19 Requiring Mechanical Ventilation

Rationale Upper limb dysfunction is well recognised in survivors of intensive care (Gustafson et al Crit Care Med 2018;46:1769-1774). A mainstay of respiratory support through the COVID-19 pandemic has been use of repeated patient prone positioning to improve ventilation. Potential complications reported with prone positioning of sedated patients include brachial plexopathy, shoulder subluxation and peripheral nerve injury. We hypothesised that there would be a high prevalence of upper limb dysfunction, disability and pain in survivors of COVID-19 requiring mechanical ventilation, particularly in those who were prone positioned. Methods Eligible patients were laboratory-confirmed swab positive for SARS-CoV-2, mechanically ventilated for a minimum of 72 hours on the Royal Brompton Hospital Adult Intensive Care Units. We measured handgrip strength (HGS), normalised for age and sex, the Disability of Arm Shoulder Hand (DASH) questionnaire (Beaton et al J Hand Ther 2001;14:128-146) and Upper limb Pain Numerical Rating Scale (from 0-10). Health related quality of life was measured using the EuroQol-5 dimensions 5-level (EQ5D5L Utility Index (UI) and Visual Analogue Score (VAS)). Patients were stratified according to whether they received prone positioning or not. Results Twenty-seven consecutive patients were assessed at mean 45 days after hospital discharge. Baseline demographics, admission characteristics, and follow-up upper limb assessment data are shown in Table 1. There was evidence of upper limb weakness (mean (SD) right HGS: 44.77(19.31) %predicted;left HGS 47.69 (18.41) %predicted), with 63% showing upper limb dysfunction (DASH ≥ 16) and 33% showing severe upper limb dysfunction (DASH ≥40). Median (IQR) pain scores were 4 (0.75-6.25) with 53% reporting severe pain (≥ 5). DASH correlated significantly with EQ5D5L UI and VAS (r=-0.69 and r=-0.73 respectively;both p<0.001). No significant differences in upper limb parameters were seen between patients who did or did not receive prone positioning.

Minimal clinically important difference for pedometer step count in COPD: A prospective analysis

Background: Infection control precautions arising from the COVID-19 pandemic has led to challenges undertaking face-to-face exercise testing required for pulmonary rehabilitation (PR) exercise prescription and evaluation.1 Self-management programmes, incorporating physical activity, have been advocated as an alternative to PR when face-to-face assessment is not possible.1 Daily step count is the most commonly used physical activity outcome and does not require face-to-face assessment. We aimed to estimate the minimal clinically important difference (MCID) for daily pedometer step count in COPD, using response to PR as a model of improvement and longitudinal decline following PR as a model of deterioration. Methods: This was a secondary analysis of a trial that investigated the effectiveness of pedometer-directed step count targets in COPD as an adjunct to PR, with the study arms combined as the intervention did not result in significant between-group differences.2 We measured spirometry, Medical Research Council score, incremental shuttle walk test, Chronic Respiratory Questionnaire and pedometer step count (Yamax Digiwalker CW700) pre-, post- and six months following PR. Post-PR and six months post-PR, participants completed a Global Rating of Change Questionnaire: 'How do you feel your physical activity levels have changed following rehabilitation?' and rated the response on a five-point Likert scale ( '1: I feel much more active' to '5: I feel much less active'). The MCID for improvement was defined as the median for '2: I feel a little more active' at the post-PR assessment. The MCID for deterioration was the median for '4: I feel a little less active' at the six-month assessment (compared to post-PR). Results: 152 participants enrolled in PR;80% and 70% attended the post-PR and six month assessments respectively. Baseline characteristics and change with PR and over time are (Table presented) in table 1. There were significant improvements in daily pedometer step count following PR and reductions at six months. The median (25th, 75th centile) MCID estimate for improvement and deterioration in daily pedometer step count was 427 (-443, 1286) and -456 (-2271, 650) steps respectively. Conclusion: The MCID estimates for improvement with PR and deterioration over time after PR are 427 and -456 steps respectively.