Facemask Spirometry as a Marker of Respiratory Function and Prognosis in Motor Neurone Disease
Banerjee, Sandip Kamakhya
Background: The assessment and monitoring of respiratory muscle function is clinically relevant in patients with Motor Neurone Disease (MND). Early identification of respiratory muscle dysfunction has therapeutic and prognostic consequences. Current evidence shows that Non-invasive Ventilation (NIV) is associated with improved survival, quality of life and cognitive function. This thesis examines the role of early referral for NIV, serial measurements of vital capacity as a marker of respiratory compromise and advance planning for managing the terminal phase of disease. Study population and methods: With an annual incidence of 2.8 per 100,000; 70 new cases of MND per year were predicted in the catchment population. The thesis is set out in 4 phases. A retrospective case note analysis of the referrals and initiation of NIV in patients with MND between 2000 and 2010 to RSSC, Papworth compared to UK national average. A prospective study (phase 1) compared mask spirometry with conventional tube spirometry in an unselected MND clinic population grouped according to degree of bulbar involvement. Sixty of the 73 subjects screened were recruited. A prospective, diagnostic cohort study (phase 2) to assess spirometry measures in predicting outcomes in bulbar and non-bulbar MND subjects. Sixty seven of 78 consecutive subjects with a new or existing diagnosis of MND (not using NIV and without a tracheostomy) were recruited. A questionnaire survey of all patients (n=70) with probable or definite MND in the East of England region, identified by a network of clinicians, who died between October 2010 and December 2011. Results: Phase 1: Mean annual referral numbers were 44 with 31 NIV starters per year (70% of patients referred) rising from 7 to 44 per annum between 2006 to 2010. Phase 2: Mask spirometry produced higher values than tube spirometry, in patients with FVC < 3 litres. Higher values of FVC were recorded in patients with moderate to severe bulbar involvement, irrespective of FVC. Phase 3: There was no significant difference between mask and tube spirometry in predicting the onset of ventilatory failure or death. Patients with FVC <70% predicted were more likely to need NIV in a 3 month follow up. The results showed that serial measurements of tube or facemask FVC correlated with progression to respiratory failure or death. Phase 4: There was no difference in the time and mode of death in patients with NIV compared to those without NIV support. Advanced care plans had been documented in 41%. Conclusions: My thesis demonstrated higher referral rates and NIV initiation in MND patients at RSSC, Papworth compared to UK national average, which was due to implementation of a care pathway later confirmed in the NICE guidance. This thesis also confirmed that the rate of decline of FVC, may predict the onset of ventilatory failure, irrespective of bulbar involvement. My questionnaire survey of death in MND confirmed that the dying process is not prolonged for patients who have used NIV at home.
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