Pc Deegan

Predictive value of clinical features for the obstructive sleep apnoea syndrome

The advantage of being a National Referral Centre for patients with suspected obstructive sleep apnoea (OSA) was used to seek clinical factors predictive of OSA, and thus determine if the number of polysomnography tests required could be reduced. Patients were mainly primary referrals, from an island population of 3.5 million. Two hundred and fifty consecutive patients underwent clinical assessment, full polysomnography, and a detailed self-administered questionnaire. This represents one of the largest European studies, so far, utilizing full polysomnography. Fifty four percent (n = 134) had polysomnographic evidence of OSA (apnoea/hypopnoea index (AHI) > or = 15 events.h-1 sleep). Patients with OSA were more likely to be male, and had a significantly greater prevalence of habitual snoring, sleeping supine, wakening with heartburn, and dozing whilst driving. Alcohol intake, age and body mass index (BMI) were significant independent correlates of AHI. After controlling for BMI and age, waist circumference correlated more closely with AHI than neck circumference among males, while the opposite was true among females. No single factor was usefully predictive of obstructive sleep apnoea. However, combining clinical features and oximetry data, where appropriate, approximately one third of patients could be confidently designated as having obstructive sleep apnoea or not. The remaining two thirds of patients would still require more detailed sleep studies, such as full polysomnography, to reach a confident diagnosis.

Reversible hypercapnia in chronic obstructive pulmonary disease: A distinct pattern of respiratory failure with a favorable prognosis

PURPOSE Hypercapnia is regarded as a poor prognostic indicator in chronic obstructive pulmonary disease (COPD), but many patients hospitalized with hypercapnia associated with an acute exacerbation of COPD revert to normocapnia during recovery. We wished to determine if this reversible hypercapnia represents a distinct pattern of respiratory failure in COPD, or simply a stage in the progression to chronic hypercapnia. We therefore compared the long-term clinical progression and survival of COPD patients with reversible hypercapnic respiratory failure (defined as type 2.1) to those with normocapnic (PaCO2 < 50 mm Hg; type 1) and also to those patients with chronic hypercapnic (PaCO2 > 50 mm Hg) respiratory failure (defined as type 2.2). PATIENTS AND METHODS We prospectively followed for 5 years a cohort of 85 patients who had been admitted as emergencies during a 1-year period to the respiratory unit of a University teaching hospital with an exacerbation of COPD complicated by respiratory failure (PaO2 < 60 mm Hg). The main long-term outcome measures were survival and blood gas changes. RESULTS Sixty-eight (80%) patients survived the initial admission, and 17 (27%) survived 5 years. PaCO2 rose substantially more during exacerbations in type 2.1 patients (mean 15.8 mm Hg), compared with type 2.2 (mean 6.8 mm Hg) and type 1 patients (mean 1.5 mm Hg). We analyzed 149 subsequent admissions among the survivors over the following 5 years. Type 2.1 patients had a better 5-year survival (28%) than type 2.2 (11% survival; P < 0.05), and similar to type 1 patients (33% 5-year survival). Only 24% of reversible hypercapnic patients developed chronic hypercapnia during long-term followup. CONCLUSIONS The data support reversible hypercapnia being a distinct manifestation of respiratory failure in COPD, with a similar prognosis to that of normocapnic respiratory failure.

Haemodynamic effects of nasal continuous positive airway pressure in severe congestive heart failure

Nasal continuous positive airway pressure (NCPAP) during sleep may be a useful adjunct to medical therapy in patients with stable severe congestive heart failure (CHF), particularly when there is a coexisting respiratory sleep disorder. However, the direct haemodynamic effects of NCPAP in patients with severe stable CHF have not yet been adequately assessed. Right heart catheter studies were performed in seven awake males (aged 51-75 yrs) with stable CHF, before, during and after the application of 5 cmH2O NCPAP over 3 h. All patients had left ventricular ejection fractions < or = 30% and baseline pulmonary capillary wedge pressures > 12 mmHg, and six patients were in atrial fibrillation. Cardiac index fell from baseline in all patients whilst on NCPAP, with the greatest fall at 2 h (from 3.3 +/- 0.3 (mean +/- SEM) at baseline to 2.8 +/- 0.2 l.min-1.m-2) and rose back to baseline after NCPAP withdrawal. Systemic vascular resistance (SVR) increased during NCPAP application (1,268 +/- 108 to 1,560 +/- 82 dyn.s-1.cm5), with baseline SVR showing a significant negative correlation vs percentage fall in cardiac index (CI) at 2 h on multiple linear regression analysis (r2 = 0.8). These data indicate that domiciliary nocturnal NCPAP should not be prescribed as part of the therapy in severe CHF without first determining the individual patients cardiac response to such therapy.

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.

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.

Topical Oropharyngeal Anesthesia in Patients with Obstructive Sleep Apnea

Topical oropharyngeal anesthesia (TOPA) increases obstructive sleep apnea (OSA) frequency in both normal subjects and loud snorers. The effects of TOPA in established OSA were assessed in six male patients with a mean age (+/- SEM) of 50 +/- 5.3 yr. Following an acclimatization night, each subject underwent two overnight sleep studies, randomly assigned to TOPA (10% lidocaine spray and 0.25% bupivocaine gargle) and control (C) (saline placebo). Patients demonstrated sleep efficiencies of 93 +/- 2.9% (mean +/- SEM) during C and 88 +/- 2.9% during TOPA. Overall apnea-hypopnea (AH) frequency, using inductance plethysmography, showed little change: 21.2 +/- 3.6 on C versus 25.1 +/- 3.5 events/h on TOPA nights (p = 0.12). There was no significant increase in AH duration with TOPA, and oxygen desaturation (> or = 4%) frequency was similar: 21.1 +/- 3.9 per hour during TOPA versus 23.6 +/- 5.9 during C. However, obstructive AHs showed a change in thoracoabdominal motion from C to TOPA nights, with an increase in events with abdominal paradox from 3.1 +/- 1.1 to 10.3 +/- 3.1 per hour (p = 0.03), and a reduction in events with ribcage paradox from 13.1 +/- 1.6 to 8.2 +/- 2.4 per hour (p = 0.08). Central and mixed AHs demonstrated similar frequencies on both nights. These data support an impairment of upper airway (UA) protective reflexes among patients with OSA.

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.

Treatment of Robin sequence with nasal CPAP.

A 12-year-old schoolgirl presented with severe obstructive sleep apnoea due to the Robin sequence. The sleep apnoea, together with the associated findings of daytime sleepiness, nocturia, right heart strain and growth retardation, were successfully reversed by nasal CPAP therapy. This therapy allows postponement of a decision concerning corrective surgery until after full growth has occurred.