Reference equations for evaluation of spirometry function tests in South Asia, and among South Asians living in other countries.

BACKGROUND: There are few data to support accurate interpretation of spirometry data in South Asia, a major global region with a high reported burden of chronic respiratory disease. METHOD: We measured lung function in 7453 healthy men and women aged ≥18 years, from Bangladesh, North India, South India, Pakistan and Sri Lanka, as part of the South Asia Biobank study. First, we assessed the accuracy of existing equations for predicting normal forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1) and FEV1/FVC ratio. Then, we used our data to derive (n=5589) and internally validate (n=1864) new prediction equations among South Asians, with further external validation among 339 healthy South Asians living in Singapore. RESULTS: The Global Lung Initiative (GLI) and National Health and Nutrition Examination Survey consistently overestimated expiratory volumes (best fit GLI-African American, mean±sd z-score: FEV1 -0.94±1.05, FVC -0.91±1.10; n=7453). Age, height and weight were strong predictors of lung function in our participants (p<0.001), and sex-specific reference equations using these three variables were highly accurate in both internal validation (z-scores: FEV1 0.03±0.99, FVC 0.04±0.97, FEV1/FVC -0.03±0.99) and external validation (z-scores: FEV1 0.31±0.99, FVC 0.24±0.97, FEV1/FVC 0.16±0.91). Further adjustment for study regions improves the model fit, with highest accuracy for estimation of region-specific lung function in South Asia. CONCLUSION: We present improved equations for predicting lung function in South Asians. These offer the opportunity to enhance diagnosis and management of acute and chronic lung diseases in this major global population.

Health-related quality of life in a multiracial Asian interstitial lung disease cohort.

Background: Understanding health-related quality of life (HRQL) in patients with interstitial lung disease (ILD) provides insight into disease burden and treatment effects on patients' well-being. We examined HRQL in a multiracial Asian ILD cohort using the King's brief ILD (K-BILD) and EuroQol 5-dimension-3-level (EQ5D-3L) questionnaires and their associations with several clinical variables. Methods: This was a single-centre cross-sectional study of ILD patients in a university-affiliated tertiary public hospital in Singapore. All patients completed two self-administered HRQL questionnaires upon study entry, and their clinical information was retrieved from electronic medical records. Results: Ninety-nine patients (56% male, 75% Chinese) were included. The median (interquartile range) age was 63 (54-72) years. The most common ILD diagnosis was connective tissue disease-related ILD (n=51, 52%), followed by idiopathic pulmonary fibrosis (n=27, 27%). The mean (standard deviation) scores for the EQ5D-3L utility value, EQ5D Visual Analogue Scale (VAS) and K-BILD total were 0.806 (0.284), 75.1 (12.8) and 63.9 (14.3), respectively. A moderate correlation was found between the EQ5D-3L and K-BILD total and domain scores. The HRQL scores also correlate moderately with the modified Medical Research Council dyspnoea scale (mMRC) scores. There was a weak-to-moderate correlation between HRQL and forced vital capacity (FVC), carbon monoxide diffusing capacity (DLCO) and Charlson comorbidity index. Multiple linear regression showed a significant association of K-BILD total [beta coefficient 0.244, 95% confidence interval (CI): 0.075-0.414; P=0.005], K-BILD 'breathlessness and activities' (beta coefficient 0.448, 95% CI: 0.192-0.703; P=0.001), and the 'psychological' domain (beta coefficient 0.256, 95% CI: 0.024-0.488; P=0.031) with DLCO %pred after adjustment for age, sex, BMI, race, smoking history, comorbidities, FVC %pred and ILD diagnosis. Non-Chinese race was a predictor of better K-BILD 'psychological' domain (beta coefficient 8.680, 95% CI: 0.656-16.704; P=0.034) after adjustment. Conclusions: HRQL is significantly impaired in ILD patients, and low DLCO is a strong predictor of this impairment.

Exercise intolerance due to chronotropic incompetence uncovered by cardiopulmonary exercise test: an often overlooked manifestation of ischaemic heart disease.

A 60-year-old delivery man was referred for evaluation of unexplained exertional dyspnoea despite initial non-diagnostic investigations, including pulmonary function tests and dobutamine stress echocardiography. A symptom-limited cardiopulmonary exercise test (CPET) revealed chronotropic incompetence (CI), reduced oxygen uptake (VO2)/work slope at moderate-high workload, and ST-segment depression on recovery electrocardiogram. Coronary angiogram confirmed severe stenosis in right coronary artery and left anterior descending artery, for which he underwent percutaneous coronary stenting and cardiac rehabilitation. An interval CPET showed improvement in heart rate (HR) response and aerobic capacity. CI is characterized by an attenuated HR response to incremental exercise or an increased HR reserve despite maximal effort. Clinically, it is an independent predictor of adverse cardiovascular events and mortality. CI is frequently overlooked, highlighting the importance of CPET in the diagnostic workup of unexplained dyspnoea.

Clinical course and physiotherapy intervention in 9 patients with COVID-19.

Since the outbreak of the 2019 novel coronavirus (COVID-19), the role of physiotherapy for patients with COVID-19 infection has been highlighted by various international guidelines. Despite that, clinical information regarding the rehabilitation of patients with COVID-19 infection remains limited. In this case series, we provide a novel insight into the physiotherapy management in patients infected with COVID-19 in Singapore. The main findings are: (1) Respiratory physiotherapy interventions were not indicated in the majority of the patients with COVID-19 in this case series; (2) During rehabilitation, exertional or position-related desaturation is a common feature observed in critically ill patients with COVID-19 infection locally. This clinical phenomenon of exertional or positional-related desaturation has significantly slowed down the progression of rehabilitation in our patients. As such, it can potentially result in a significant burden on healthcare resources to provide rehabilitation to these patients. Based on these findings, we have highlighted several recommendations for the provision of rehabilitation in patients who are critically ill with COVID-19.

Reversible platypnea-orthodeoxia in COVID-19 acute respiratory distress syndrome survivors.

Platypnea-orthodeoxia syndrome (POS) is a rare clinical syndrome characterized by orthostatic oxygen desaturation and positional dyspnea from supine to an upright position. We observed POS in 5 of 20 cases of severe 2019 novel coronavirus (COVID-19) pneumonia, which demonstrated persistently elevated shunt fraction even after liberation from mechanical ventilation. POS was first observed during physiotherapy sessions; median oxygen desaturation was 8 % (range: 8-12 %). Affected individuals were older (median 64 vs 53 years old, p = 0.05) and had lower body mass index (median 24.7 vs 27.6 kg/m2, p = 0.03) compared to those without POS. While POS caused alarm and reduced tolerance to therapy, this phenomenon resolved over a median of 17 days with improvement of parenchymal disease. The mechanisms of POS are likely due to gravitational redistribution of pulmonary blood flow resulting in increased basal physiological shunting and upper zone dead space ventilation due to the predominantly basal distribution of consolidative change and reported vasculoplegia and microthrombi in severe COVID-19 disease.

The pattern of use and survival outcomes of a dedicated adult Home Ventilation and Respiratory Support Service in Singapore: a 7-year retrospective observational cohort study.

BACKGROUND: In Singapore, a dedicated adult multidisciplinary Home Ventilation and Respiratory Support Service (HVRSS) was set-up to assist individuals with chronic ventilatory failure. We aimed to study the use, survival outcomes and identify factors influencing survival in our cohort of ventilator-assisted individuals (VAIs). METHODS: We retrospectively reviewed all referrals to HVRSS from 2009 to 2015. All VAIs were included and divided into 4 categories: (I) amyotrophic lateral sclerosis (ALS); (II) other neuromuscular and chest wall disease (NMCW); (III) spinal cord injury (SCI); and (IV) complex intensive care unit (ICU) groups for comparison of baseline characteristics, co-morbidities, therapy details and survival outcomes. Cox proportional analysis was used to identify important factors influencing survival for ALS and non-ALS VAIs. RESULTS: There were 112 VAIs; most were male (63%) and ethnic Chinese (83%). At baseline, median [interquartile range (IQR)] age was 61 [46-69] years, body mass index was 20.2 (17.1-23.8) kg/m2 and forced vital capacity was 38 [24-65] %predicted. The three most common diseases were ALS (43%), SCI (13%) and congenital muscular dystrophies (6%). Seventy-four (66%) VAIs received non-invasive ventilation (NIV). Median survival for ALS, Complex ICU, SCI and NMCW VAIs were 1.8, 2.6, 4.2 and 6.7 years respectively. In ALS, NIV conversion to invasive mechanical ventilation (IMV) was associated with longer survival [hazard ratio (HR) 0.24]. In non-ALS VAIs, older age (HR 1.40) and cardiovascular comorbidities (HR 2.61) were poor prognostic factors. CONCLUSIONS: The HVRSS managed a heterogenous group of VAIs in Singapore and survival is comparable to published cohorts. ALS had the worst survival whereas NMCW had the best survival with Complex ICU and SCI groups in between. Transition from NIV to IMV, age and cardiovascular disease were important prognostic factors.

Reversible platypnoea-orthodeoxia syndrome in post-tuberculosis bronchial stenosis.

Bronchial stenosis is known to complicate endobronchial tuberculosis despite medical therapy. It is often associated with dyspnoea. In severe cases, bronchial stenosis results in airflow obstruction, impaired secretion clearance, and can lead to respiratory failure. We present an unusual observation of platypnoea-orthodeoxia syndrome in a young woman with acute atelectasis due to post-tuberculosis bronchial stricture. Imaging revealed complete middle and right lower lobe atelectasis with a partially aerated right upper lobe. In the sitting posture, there was positional worsening of dyspnoea associated with an increase in the alveolar-arterial oxygen gradient and shunt fraction. The likely mechanism was due to gravitational difference in ventilation-perfusion matching. The platypnoea-orthodeoxia syndrome was reversible following balloon dilatation of the bronchial stenosis and expansion of the collapsed lung.

Patterns of use, survival and prognostic factors in patients receiving home mechanical ventilation in Western Australia: A single centre historical cohort study.

Home mechanical ventilation (HMV) is used in a wide range of disorders associated with chronic hypoventilation. We describe the patterns of use, survival and predictors of death in Western Australia. We identified 240 consecutive patients (60% male; mean age 58 years and body mass index 31 kg m-2) referred for HMV between 2005 and 2010. The patients were grouped into four categories: motor neurone disorders (MND; 39%), pulmonary disease (PULM; 25%, mainly chronic obstructive pulmonary disease), non-MND neuromuscular and chest wall disorders (NMCW; 21%) and the obesity hypoventilation syndrome (OHS; 15%). On average, the patients had moderate ventilatory impairment (forced vital capacity: 51%predicted), sleep apnoea (apnoea-hypopnea index: 25 events h-1), sleep-related hypoventilation (transcutaneous carbon dioxide rise of 20 mmHg) and daytime hypercarbia (PCO2: 54 mmHg). Median durations of survival from HMV initiation were 1.0, 4.2, 9.9 and >11.5 years for MND, PULM, NMCW and OHS, respectively. Independent predictors of death varied between primary indications for HMV; the predictors included (a) age in all groups except for MND (hazard ratios (HRs) 1.03-1.10); (b) cardiovascular disease (HR: 2.35, 95% confidence interval (CI): 1.08-5.10) in MND; (c) obesity (HR: 0.28, 95% CI: 0.13-0.62) and oxygen therapy (HR: 0.33, 95% CI: 0.14-0.79) in PULM; and (d) forced expiratory volume in 1 s (%predicted; HR: 0.93, 95% CI: 0.88-1.00) in OHS.