Daytime sleepiness and polysomnographic variables in sleep apnoea patients

Excessive daytime sleepiness (EDS) is not invariably present in patients with obstructive sleep apnoea syndrome (OSAS). The aim of the present study was to investigate polysomnographic determinants of EDS in patients with OSAS. EDS was assessed using the Epworth Sleepiness Scale (ESS) and the multiple sleep latency test (MSLT). Patients showed EDS whenever the ESS score was >10 and the MSLT score <5 min. Absence of EDS was defined as having an ESS score of <10 and an MSLT score of >10 min. In total, 23 male patients with EDS (mean+/-sd ESS and MSLT score 17+/-3 and 4+/-1 min, respectively) and 17 without EDS (ESS and MSLT score 5+/-2 and 16+/-3 min, respectively), were studied. Both groups exhibited a similar apnoea/hypopnoea index (62+/-18 versus 60+/-20 events.h(-1)). Patients with EDS exhibited shorter sleep latency (11+/-16 versus 18+/-18 min) and greater sleep efficiency (90+/-7 versus 82+/-13%) than those without EDS. Patients with EDS showed lower oxygenation (lowest arterial oxygen saturation 69+/-12 versus 79+/-8%; mean arterial oxygen saturation 87+/-6 versus 90+/-5%). Sleep stage distribution and arousal index did not differ between the groups. Patients with obstructive sleep apnoea syndrome and excessive daytime sleepiness are characterised by shorter sleep latency, increased sleep efficiency and worse nocturnal oxygenation than those without excessive daytime sleepiness. Nocturnal hypoxaemia can be a major determinant of excessive daytime sleepiness in patients with obstructive sleep apnoea syndrome.

Exhaled nitric oxide and airway caliber during exercise-induced bronchoconstriction

Data on the relationship between exercise-induced bronchoconstriction (EIB) and exhaled nitric oxide (NO) in adult patients with asthma are controversial. It is unclear whether endogenous NO may act as either a protective or stimulatory factor in the airway response to exercise or whether changes in exhaled NO simply reflect acute narrowing of the airway. The aim of this study was to assess the changes in the fraction of exhaled nitric oxide (FE(NO)) before and after exercise challenge in patients with asthma and to analyze the relationship between FE(NO) and airway obstruction. Twenty-five non-smoking, steroid-naïve, atopic, adult patients with mild persistent asthma and 12 non-smoking, nonatopic, healthy subjects (control group) performed an exercise challenge on a cycloergometer, with monitored ventilation. FEV1 and FE(NO) were measured at baseline and 1, 5, 10, 15 and 20 minutes after the exercise challenge. Eleven of the asthmatic patients had exercise-induced bronchoconstriction (EIB group) and the remaining 14 did not (non-EIB group). Baseline FE(NO) was higher in the EIB and non-EIB asthmatic groups than in the control group. In the EIB group, FE(NO) was significantly lower 5, 10 and 15 minutes after exercise, and the changes in FE(NO) correlated with variation in FEV1 10 and 15 min after exercise. A significant correlation between baseline FE(NO) and maximal post-exercise decrease in FEV1 was found in asthmatic patients (EIB group). In conclusion, exhaled nitric oxide levels transiently decrease during exercise-induced bronchoconstriction in adult patients with asthma. Baseline FE(NO) might predict the airway obstruction resulting after exercise.

Comparison of Carbon Dioxide Rebreathing During Application of Continuous Positive Airway Pressure With 3 Types of Nasal Mask

A comparison is made between the end-tidal fractional concentration of carbon dioxide (FETCO2) obtained during application of varying levels of continuous positive airway pressure (CPAP) with a prototype mask (from Carburos Metálicos) and FETCO2 obtained with 2 commonly used nasal masks (Profile Lite and ComfortClassic from Respironics). The nasal FETCO2 was measured on 3 consecutive days in 11 healthy volunteers, 12 patients with severe obstructive sleep apnea-hypopnea syndrome, and 12 hypercapnic patients. A different mask was randomly assigned on each day and the FETCO2 was measured after 3 minutes of CPAP at 4, 5, 6, 8, 10, 15, and 20 cm H2O. Although in all cases a progressive reduction in FETCO2 was observed with increasing CPAP, the effect was greatest with the prototype mask at all pressures. In the 3 different study groups the pressures obtained with the prototype mask were similar to those generated by the CPAP machine. In conclusion, the lower concentration of nasal CO2 obtained using the prototype mask suggests that it causes less rebreathing.

Noninvasive measurement of the maximum relaxation rate of inspiratory muscles in patients with neuromuscular disorders

BACKGROUND

Slowing of inspiratory muscle relaxation has been used as an index for inspiratory muscle fatigue. However, maximum relaxation rate measured from oesophageal pressure traces after maximum sniff (P(oes) MRR) has limited clinical usefulness because it requires an oesophageal balloon catheter system.

OBJECTIVES

It was the aim of this study to establish whether, in neuromuscular patients, maximum relaxation rate assessed from sniff nasal pressure (P(nasal) MRR) reflects oesophageal MRR and the tension-time index of the diaphragm (TT(di)).

METHODS

Twenty patients with neuromuscular disease and 10 healthy subjects were studied. P(oes) and transdiaphragmatic pressure were measured while P(nasal) was recorded with a balloon advanced through the nose into the nasopharynx. Maximum P(oes), transdiaphragmatic pressure and P(nasal) were simultaneously measured while the patients performed maximal sniffs. The MRR (% pressure fall/10 ms) for each sniff, the TT(di) and the tension-time index of respiratory muscles were determined.

RESULTS

Neuromuscular patients showed higher TT(di), lower P(oes) MRR and lower P(nasal) MRR than the control group. In patients with neuromuscular disease, the correlation coefficient of P(nasal) MRR and P(oes) MRR was 0.985 (p < 0.001). Regression analysis showed that P(oes) MRR = -1.101 + 1.113.P(nasal) MRR (r(2) = 0.929, standard error of the estimate = 0.208). Indeed, P(nasal) MRR was negatively correlated with TT(di) (r = -0.914, p < 0.001) and the tension-time index of respiratory muscles (r = -0.732, p < 0.001). In the neuromuscular group, the mean difference between P(nasal) MRR and P(oes) MRR was 0.286 +/- 0.217%/10 ms.

CONCLUSIONS

P(nasal) MRR obtained from a maximal sniff accurately reflects P(oes) MRR and TT(di) in patients with neuromuscular disorders.

Usefulness of bronchial reactivity analysis in the diagnosis of bronchial asthma in patients with bronchial hyperresponsiveness

We examined the usefulness of some bronchial reactivity indices to identify bronchial asthma in patients with airway hyperresponsiveness. Eighty-eight consecutive patients with positive response to histamine bronchial challenge (> or = 20% fall in FEV1) were included in the study. Dose-response curves were characterised by their sensitivity (PD20) and reactivity. Dose-response slope, continuous index of responsiveness (CIR) and bronchial reactivity index (BRI) with respect to baseline and post-diluent baseline values were determined as reactivity indices. The clinical diagnosis remaining in the case history 2 years after the bronchial challenge was considered the definitive diagnosis. Asthmatic patients had higher baseline BRI (12.121+/-0.412 vs. 11.615+/-0.201; P<0.001) and post-diluent baseline BRI (12.054+/-0.368 vs. 11.563+/-0.531; P = 0.003) than other subjects. Area beneath their receiver operating characteristic (ROC) curve was 82.68% (standard error: 0.77) for the baseline BRI and 81.73 (standard error: 0.76). By multiple logistic regression analysis, baseline BRI was the only independent variable identified as a predictor for diagnosis of bronchial asthma (r = 0.387, P = 0.0007). A cut-off of 11.76 for baseline BRI reached an 87.2% sensitivity and an 80% specificity for bronchial asthma diagnosis. In conclusion, BRI calculated with respect to baseline FEV1 should be useful in identifying asthmatic patients among subjects with airway hyperresponsiveness.

[Late postoperative amiodarone pulmonary toxicity]

Amiodarone is an effective antiarrhytmic drug and it is used to treat supraventricular or ventricular rhythm disturbances. Nevertheless it is not free from side effects. Acute amiodarone-induced pulmonary toxicity is one of them. We referred a 55-year-old man who started on amiodarone after a mitral valva replacement. Afterwards he had acute respiratory failure and diffuse ill-defined opacities. The diagnosis was confirmed by detection of lots of foamy macrophages in the bronchoalveolar lavage fluid. Relief of symptoms and arterial blood gases improvement was achieved when he started on corticosteroids and amiodarone treatment was stopped.