Culadeeban Ratneswaran

Effect of Continuous Positive Airway Pressure on Blood Pressure Variability in Patients With Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is a common risk factor for cardiovascular disease. Continuous positive airway pressure (CPAP) improves OSA symptoms and blood pressure (BP) control. The effect of CPAP on BP variability (BPV) in patients with and without hypertension treated with autotitrating CPAP (APAP) for 2 weeks was studied. A total of 78 participants (76.9% men, 49% hypertensive, mean body mass index 36.2 [6.9] kg/m2, age 49.0 [12.9] years) underwent 2 weeks of APAP therapy. Office BP, BPV (standard deviation of three BP measurements), and pulse rate were measured before and after treatment. Systolic BPV (5.3±4.9 vs 4.2±3.4 mm Hg, P=.047) and pulse rate (78.0±14.5 vs 75.5±15.8 beats per minute, P=.032) decreased after treatment, particularly in hypertensive participants. Mask leak was independently associated with reduced changes in systolic BPV (r=−0.237, P=.048). Short‐term APAP treatment reduced BPV and pulse rate, particularly in hypertensive patients with OSA.

A cross-sectional survey investigating the desensitisation of graphic health warning labels and their impact on smokers, non-smokers and patients with COPD in a London cohort

Objectives There is a lack of evidence regarding the effectiveness of graphic health warning labels (GHWL) in different individuals, including patients with chronic obstructive pulmonary disease (COPD). Investigating knowledge and attitudes may allow better implementation of future public health policies. We hypothesised that differences in the impact of GHWL exist between non-smokers, smokers and patients with COPD, with decreased efficacy in those groups who are longer and more frequently exposed to them. Participants and setting 163 participants (54% male, aged 21–80) including 60 non-smokers, 53 smokers and 50 patients with COPD (Gold stage II–IV), attending London respiratory outpatient clinics, participated in case-controlled surveys (50 items). Outcome measures Ten different GHWL were shown and demographics, smoking history, plans to quit, smoking-risk awareness, emotional response, processing and impact of GHWL on behaviour were recorded. Patients were further asked to prioritise the hypothetical treatment or prevention of five specific smoking-related diseases. Results Smokers, in particular those with COPD, were less susceptible to GHWL than non-smokers; 53.4% of all participants expressed fear when looking at GHWL, non-smokers (71.9%) more so than smokers (39.8%, p<0.001). COPD participants were less aware of the consequences than non-COPD participants (p<0.001), including an awareness of lung cancer (p=0.001). Lung cancer (95%), oral cancer (90.2%), heart disease (84.7%) and stroke (71.2%) were correctly associated with smoking, whereas blindness was least associated (23.9%). However, blindness was prioritised over oral cancer, stroke and in patients with COPD also over heart disease when participants were asked about hypothetical treatment or prevention. Conclusions GHWL are most effective in non-smokers and a desensitisation effect was observed in smokers and patients with COPD. As a consequence, a tailored and concerted public health approach to use such messages is required and ‘blindness’ deserves to be mentioned in this context because of an unexpectedly high-deterring impact.

Continuous Positive Airway Pressure and Breathlessness in Obese Patients with Obstructive Sleep Apnea: A Pilot Study.

STUDY OBJECTIVES Continuous positive airway pressure (CPAP) is an effective treatment for obstructive sleep apnea (OSA). However, long-term compliance with CPAP is limited. We tested the hypothesis that CPAP levels routinely used during sleep increase neural respiratory drive (NRD) and breathlessness, which may discourage compliance. METHODS This was an observational physiological cohort study in a respiratory physiology and sleep unit, University Hospital. Patients with a body mass index (BMI) > 25 kg/m(2) and confirmed OSA were studied supine and awake on CPAP (4-20 cm H2O, increments of 2 cm H2O/3 min). We measured NRD during awake CPAP titration in obese subjects to quantify the response to the load of the respiratory system and compared it to the CPAP used for nocturnal treatment, with the modified Borg Scale (mBorg) for dyspnea recorded (from 0 to 10 points, with higher numbers indicating more breathlessness). RESULTS Fifteen patients (age 48 ± 10 years, 12 male, BMI 38.9 ± 5.8 kg/m(2)) with OSA (AHI 32.2 ± 21.1/h, 95(th) percentile of CPAP 14.1 ± 3.8 cm H2O) were studied and NRD (electromyogram of the parasternal intercostals, EMGpara; EMG of the external oblique, EMGabdomen) was recorded (awake, supine). Awake, EMGpara declined from baseline to 70.2% ± 17.1% when CPAP of 10.7 ± 3.4 cm H2O (P = 0.026) was applied. Further increase in CPAP led to a rise in EMGpara and increased breathlessness (P = 0.02). CPAP compliance (nights used) correlated negatively with mBorg scores (r = -0.738, P = 0.006). CONCLUSIONS Awake, the respiratory system is maximally offloaded with lower than therapeutic CPAP levels in obese patients with OSA. Levels of NRD observed at effective CPAP levels while asleep are associated with breathlessness which may limit long-term CPAP compliance.

Desensitisation to cigarette package graphic health warnings: a cohort comparison between London and Singapore

Objectives We compared 2 sociocultural cohorts with different duration of exposure to graphic health warning labels (GHWL), to investigate a possible desensitisation to their use. We further studied how a differing awareness and emotional impact of smoking-associated risks could be used to prevent this. Setting Structured interviews of patients from the general respiratory department were undertaken between 2012 and 2013 in 2 tertiary hospitals in Singapore and London. Participants 266 participants were studied, 163 Londoners (35% smokers, 54% male, age 52±18 years) and 103 Singaporeans (53% smokers, p=0.003; 78% male, p<0.001; age 58±15 years, p=0.012). Main outcomes and measures 50 items assessed demographics, smoking history, knowledge and the deterring impact of smoking-associated risks. After showing 10 GHWL, the impact on emotional response, cognitive processing and intended smoking behaviour was recorded. Results Singaporeans scored lower than the Londoners across all label processing constructs, and this was consistent for the smoking and non-smoking groups. Londoners experienced more ‘disgust’ and felt GHWL were more effective at preventing initiation of, or quitting, smoking. Singaporeans had a lower awareness of lung cancer (82% vs 96%, p<0.001), despite ranking it as the most deterring consequence of smoking. Overall, ‘blindness’ was the least known potential risk (28%), despite being ranked as more deterring than ‘stroke’ and ‘oral cancer’ in all participants. Conclusions The length of exposure to GHWL impacts on the effectiveness. However, acknowledging the different levels of awareness and emotional impact of smoking-associated risks within different sociocultural cohorts could be used to maintain their impact.

Sleep, obesity and physicians’ education

More than two thirds of the US population is obese or overweight, with worldwide obesity rates doubling since 1980. Obesity causes serious health risks including cardiovascular disease, diabetes and cancer (1). It is also associated with respiratory conditions like obesity hypoventilation syndrome, asthma and obstructive sleep apnoea (OSA). Obesity causes a 6-fold increase in OSA prevalence (2) and over the last two decades, has caused a rise in the prevalence of OSA to 10% in middle-aged male subjects (3).

Clinical update sleep: year in review 2015-2016.

Sleep disorders are becoming increasingly prevalent secondary to elevated levels of light-, noise- and stress-exposure in addition to rising levels of obesity. Sleep medicine is experiencing an exponential gain of knowledge that can be explained by several factors: (I) advanced physiological monitoring at night; (II) improved follow-up of patients; and (III) greater collaboration between specialties that have contributed to our understanding of long-term complications. Advances in device technology and interventions, such as minimally invasive surgery, have further helped to speed up the development of available treatment options. It does not come as a surprise that sleep medicine is ever more important and provides the perfect background for an interdisciplinary collaboration between basic scientists, clinicians and epidemiologists. This overview is dedicated to recent advances and hot topics of sleep medicine that have the potential to impact standards of care.

A model for medical school application courses: widening access to student preparation

What problems were addressed? A growing trend exists of private entities offering expensive courses to support medical school applications. These are often financially out of reach for those from poorer socio-economic backgrounds, leading to a bias of successful applications towards the richer, who can afford to be better trained, as opposed to the better skilled. Non-profit courses are often linked to a medical school society, causing a preferential bias towards the host university, and potentially providing inadequate preparation for the diverse selection procedures within other medical schools. Hence, there is a need for affordable preparatory courses, which include a diverse tutor cohort, to provide accurate admission information to all applicants, including those from poorer socio-economic backgrounds. What was tried? Medical student tutors from three universities, supervised by clinical lecturers to maintain material accuracy, coordinated a pilot philanthropic conference for 50 secondary-school students, prior to their medical application process. An outreach programme prioritised less affluent communities and a peer-assisted learning (PAL) teaching method was used, thereby incentivising the medical students through development of their organisation, communication, teaching and presentation skills, and hence avoiding the need for a financial motivation. The itinerary included ‘life as a doctor and medical student’, ‘the application process’, ‘medical communication skills’ and ‘ethical and personal statement writing’ workshops. A social media feed (facebook.com/oslersroom) encouraged collaborative learning and networking, and a website (oslersroom.com) was created, providing a social hub for students, as well as endorsing affiliated charities. Formal feedback was elicited from both tutors and attendees using an electronic survey. Multi-university committees were established to allow for longterm sustainability. What lessons were learned? On a scale of ‘poor’, ‘indifferent’, ‘good’ and ‘excellent’, 88% of attendees rated the course as ‘excellent’ and 12% as ‘good’. Free text comments included thanks to the tutors for giving up their time, increased understanding of the roles and responsibilities of doctors, appreciation of feedback on personal statements, and calls to provide similar sessions in their local schools. Tutors (n = 8), on a scale of 1 (‘poor’) to 5 (‘excellent’), reported improved confidence in teaching (2.8 0.9 to 4.4 0.4 points, p < 0.01) and public speaking (3.2 0.5 to 4.3 0.5 points, p < 0.05), and all tutors rated ‘enjoyment’ of the course overall as ‘excellent’. A British Lung Foundation award was established, supporting travel to an international medical conference; this was made available for the medical students, to further nurture academic development. Use of this philanthropic PAL model results in a cost-effective, high-quality teaching session, whilst being mutually beneficial to both prospective applicants and medical students. Our approach could help overcome an unfavourable trend that excludes those with lower socio-economic backgrounds from succeeding with their medical school applications. Future conferences will obtain input from tutors and a variety of medical schools to enhance the relevance of this approach. Talks on cognitive aspects (e.g. admission examinations) should also be incorporated, but maintaining supervision by senior members of staff is necessary to ensure the accuracy of the teaching. Data on successful admission rates of participants, as well as the students’ experiences of the conference, would help to understand the impact of this initiative and build upon its initial success.

Obesity, Respiratory Mechanics and Its Impact on the Work of Breathing, Neural Respiratory Drive, Gas Exchange and the Development of Sleep-Disordered Breathing

Obesity causes an increased load on the respiratory muscle pump that impacts on the work of breathing and requires high levels of neural respiratory drive. Elevated intra-abdominal pressures in obesity impose a preload on the diaphragm during inspiration, particularly in the supine posture. These forces contribute to a reduced transpulmonary pressure gradient in the thoracic compartment and affect operational lung volumes. Morbidly obese subjects breathe at low lung volumes, close to the residual volume (RV); their functional residual capacity shifts towards a less favourable part of the pressure-volume curve with a reduced compliance. At low lung volumes, the closing volume of the airway increases airway resistance further and contributes an intrinsic positive end-expiratory pressure. In the asleep subject, the reduced neuromuscular tone in the skeletal muscles results in increased upper airway collapsibility and, potentially, leads to obstructive sleep apnoea. Reduced respiratory muscle recruitment during sleep causes alveolar hypoventilation and obesity hypoventilation syndrome (OHS). The disadvantageous respiratory mechanics in obesity can be overcome by the use of continuous positive airway pressure to avoid upper airway collapse and noninvasive ventilation to support ventilation. Physiological changes observed with obesity are largely reversible following significant weight loss. It is important to consider the respiratory physiology in obesity when screening for sleep-disordered breathing in this population prior to iatrogenic interventions.

Preface for the 3rd Clinical Update Sleep, 23rd February 2018, Royal College of Physicians, London, UK: year in review.

Sleep medicine remains an exciting and fast-evolving field of medicine with insomnia, hypersomnia, parasomnia, sleep-disordered breathing and circadian rhythm disorders affecting significant proportions of the population. This update provides a selected overview about recent publications in the field.

The acute effect of continuous positive airway pressure titration on blood pressure in awake overweight/obese patients with obstructive sleep apnoea

Abstract Objectives: Continuous positive airway pressure (CPAP) improves upper airway obstruction in patients with obstructive sleep apnoea (OSA), who often are overweight-obese. Although it is thought that CPAP improves long-term blood pressure control (BP), the impact of acute and short-term CPAP use on the cardiovascular system in obese patients has not been described in detail. Methods: Obese patients (body mass index, BMI > 25 kg/m2) with OSA were studied awake, supine during incremental CPAP titration (4–20 cmH2O, +2 cmH2O/3 mins). BP was measured continuously with a beat-to-beat BP monitor (Ohmeda 2300, Finapres Medical Systems, Amsterdam/NL), BP variability (BPV) was calculated as the standard deviation of BP at each CPAP level, the 95% confidence interval (95%CI) was calculated and changes in BP and BPV were reported. Results: 15 patients (12 male, 48 ± 10) years, BMI 38.9 ± 5.8 kg/m2) were studied; the baseline BP was 131.0 ± 10.2/85.1 ± 9.1 mmHg. BP and BPV increased linearly with CPAP titration (systolic BP r = 0.960, p < .001; diastolic BP r = 0.961, p < .001; systolic BPV r = 0.662, p = .026; diastolic BPV r = 0.886, p < .001). The systolic BP increased by +17% (+23.15 (7.9, 38.4) mmHg; p = .011) and the diastolic BP by +23% (+18.27 (2.33, 34.21) mmHg; p = .009), when titrating CPAP to 20 cmH2O. Systolic BPV increased by +96% (+5.10 (0.67, 9.53) mmHg; p < .001) and was maximal at 14 cmH2O, and diastolic BPV by +97% (+3.02 (0.26, 5.78) mmHg; p < .001) at 16 cmH2O. Conclusion: Short-term incremental CPAP leads to significant increases in BP and BPV in obese patients with OSA while awake. Careful titration of pressures is required to minimise the risk of nocturnal awakenings while improving BP control.