John L. Kiely

Comparison of a limited computerized diagnostic system (ResCare Autoset) with polysomnography in the diagnosis of obstructive sleep apnoea syndrome

The increasing numbers of patients referred for evaluation of suspected obstructive sleep apnoea (OSA) places a growing burden on available sleep laboratory resources. A number of limited diagnostic systems have been developed in an effort to cope with this clinical problem. In this study, the diagnostic capabilities of one limited diagnostic system (ResCare Autoset) were compared with full polysomnography (PSG), using the Oxford SAC computerized system. Thirty six patients with suspected OSA had simultaneous studies performed both with the Autoset and Oxford PSG systems. The apnoea plus hypopnoea index (AHI) (events x h(-1)) scored by the Autoset system was compared with the AHI scored from the PSG raw tracings by an experienced sleep technician. There were highly significant correlations between the Autoset AHI and the AHI scored by the manual PSG scoring method (r=0.92; p<0.001). The positive predictive value for diagnosis of OSA for the Autoset was 86% when compared with manual PSG scoring, based on an AHI threshold for OSA of 15 events x h(-1). However, the agreement between Autoset and PSG was poor in severe cases of OSA, although not sufficiently so as to result in mistaken diagnosis in any of these cases. We conclude that the Autoset system is a sensitive and easy to use system, which facilitates screening for obstructive sleep apnoea with a reasonable degree of accuracy.

Efficacy of nasal continuous positive airway pressure therapy in chronic heart failure: importance of underlying cardiac rhythm

BACKGROUND Some previous reports have indicated beneficial cardiac effects of nasal continuous positive airway pressure (NCPAP) in patients with severe congestive heart failure (CHF), but others have reported deleterious cardiac effects, particularly among patients in atrial fibrillation (AF). The aim of this study was to determine if differences in cardiac rhythm influence the acute cardiac response to NCPAP. METHODS Eleven consecutive patients with CHF were recruited, six in atrial fibrillation (AF) and five with sinus rhythm (SR). Cardiac index was measured during awake NCPAP application by the thermodilution technique during cardiac catheterisation. NCPAP was applied in a randomised sequence at pressures of 0, 5, and 10 cm H2O with three 30 minute applications separated by 20 minute recovery periods without NCPAP. RESULTS Significant differences were found between the AF and SR groups for cardiac index responses to NCPAP (p = 0.004, ANOVA) with a fall in cardiac index in the AF group (p = 0.02) and a trend towards an increase in the SR group (p = 0.10). Similar differences were seen between the groups in stroke volume index responses but not in heart rate responses. Changes in systemic vascular resistance were also significantly different between the two groups (p< 0.005, ANOVA), rising in the AF group but falling in the SR group. CONCLUSIONS These data indicate an important effect of underlying cardiac rhythm on the awake haemodynamic effects of NCPAP in patients with CHF.

Controlled oxygen therapy and carbon dioxide retention during exacerbations of chronic obstructive pulmonary disease

Hypoxaemic patients with exacerbations of chronic obstructive pulmonary disease (COPD) are at some risk of carbon dioxide (CO2) retention during oxygen therapy. We quantified the risk of CO2 retention with oxygen therapy in COPD in 24 consecutive patients presenting to the accident and emergency department with acute exacerbations associated with hypercapnic respiratory failure (partial arterial pressure of oxygen [PaO2] < 8 kPa and partial pressure of CO2 [PaCO2] > or = 6.5 kPa). Only three patients developed clinically important CO2 retention (defined as a rise in PaCO2 > 1 kPa) with controlled oxygen therapy (24-40% by Venturi mask to maintain the oxygen saturation at 91-92%). These patients presented with more severe hypercapnia, but all three required only low-flow oxygen (24-28%). These findings suggest only a small risk of aggravating hypercapnia with controlled oxygen supplementation.

Late-onset central hypoventilation syndrome: a family genetic study

Congenital central hypoventilation syndrome is a rare disorder characterised by chronic alveolar hypoventilation, which becomes more pronounced during sleep and may be associated with neurocristopathies, such as Hirchsprungs disease. A mutation in the PHOX2B gene has recently been identified. In a family of both parents and five offspring, detailed clinical assessment, pulmonary function testing, overnight sleep studies and ventilatory responsiveness to progressive hypercapnia (V′R,CO2) were performed, in addition to analysis of known genetic loci for this condition. The father and four of the offspring demonstrated features of central hypoventilation with nonapnoeic oxygen desaturation during sleep and diminished V′R,CO2, despite normal pulmonary function. The lowest sleep saturation was median (range) 79% (67–83%) and V′R,CO2 was 2.1 (0.03–4.3) L·min-1·kPa-1. The normal values for the authors’ centre (St Vincents University Hospital, Dublin, Ireland) are 15–40 L·min-1·kPa-1. An in-frame five amino acid polyalanine expansion of the PHOX2B gene was found in all affected subjects, while the mother and fifth child, who did not have features of central hypoventilation, had a normal PHOX2B gene. Magnetic resonance imaging of the brainstem in one severely affected child was normal. The present study of a unique family confirms that transmission of late-onset congenital central hypoventilation syndrome is autosomal dominant in nature.

Resolution of obstructive sleep apnoea with growth in the Robin sequence

A 12 year old female with the Robin sequence presented with a one year history of snoring, witnessed apnoeas and daytime sleepiness. Surgery in early childhood had consisted of cleft palate repair, tonsillectomy and adenoidectomy and, later, revision palatoplasty. Overnight polysomnography (PSG) demonstrated severe obstructive sleep apnoea syndrome with an apnoea/hypopnoea index (AHI) of 49 events x h(-1), and repetitive oxygen desaturations below 50%. Nasal continuous positive airway pressure (nCPAP) effectively controlled her sleep abnormalities. After 3 yrs of nCPAP therapy, she requested discontinuation and was fully reassessed. PSG without nCPAP revealed an AHI <5 events x h(-1) with no desaturations below 90% and normal sleep quality. A repeat lateral cephalometrogram showed increased mandibular length and posterior airway space and reduced soft palate length. The patient remains asymptomatic 9 months following nCPAP discontinuation. This case indicates that nasal continuous positive airway pressure is an effective nonsurgical therapy in children with obstructive sleep apnoea syndrome and the Robin sequence. It is likely that mandibular growth, increase in mandibular length and enlargement of the posterior airway space was responsible for the resolution of obstructive sleep apnoea syndrome in this case.

The role of nasal CPAP in obstructive sleep apnoea syndrome due to mandibular hypoplasia.

Melnick Needles syndrome (MNS), Treacher Collins syndrome (TCS) and Pierre Robin syndrome (PRS) are congenital abnormalities with characteristic facial appearances that include micrognathia. A 20‐year‐old girl with MNS, a 16‐year‐old boy with TCS and a 12‐year‐old girl with PRS attended the sleep apnoea clinic at our institution at different times. Diagnostic sleep studies were initially performed on all three patients to confirm the diagnosis of obstructive sleep apnoea syndrome (OSAS). They subsequently commenced nasal CPAP (nCPAP) treatment and their progress was followed. A limited sleep study on the patient with MNS demonstrated moderate/severe OSAS with an AHI of 33 events/h. Commencement of nCPAP resulted in symptomatic improvement. Overnight oximetry in the patient with TCS showed repeated desaturation to SpO2 <90%. Subsequent treatment by nCPAP almost completely abolished the desaturation events. Overnight polysomnography in the patient with PRS demonstrated severe OSAS with an AHI of 49 events/h. After 3 years of nCPAP therapy, this patient requested discontinuation of treatment. Subsequent polysomnography without nCPAP revealed an AHI of <5 events/h. The use of nCPAP in the patients with MNS and TCS resulted in effective control of their sleep abnormalities. Mandibular growth and enlargement of the posterior airway space led to resolution of OSAS in the patient with PRS. There is a definite role for nCPAP therapy in patients with congenital micrognathia and OSAS. The use of nCPAP may obviate the need for more invasive corrective surgery for OSAS and is not necessarily a life‐long requirement.