Titration with automatic continuous positive airway pressure in obstructive sleep apnea.

BACKGROUND AND OBJECTIVE: Autotitrating positive airway pressure (APAP) is an accepted titration method to determine the optimal positive airway pressure (PAP), for the treatment of obstructive sleep apnea (OSA). The required duration of APAP monitoring to determine a fixed continuous positive airway pressure level still remains to be established. We aimed to evaluate the variation in PAP level, delivered by APAP devices, at different periods of treatment, to determine the APAP treatment duration required to reach an effective and stable PAP level. METHODS: A cross-sectional study of 62 patients newly diagnosed with OSA were evaluated after 3 months of APAP therapy. APAP data corresponding to the first day (D1), first week (W1), seventh week (W7) and twelfth week (W12) under APAP therapy was collected. For the analysis of the pressure behaviour, the difference of P95th pressure level between W12 and W7 (P W12-W7), W12 and W1 (P W12-W1) and W12 and D1 (P W12-D1) was calculated. RESULTS: There was a high correlation in P95th pressure level between D1 and W12 (r=0.771; p>0.0001), W1 and W12 (r=0.817; p>0.0001), and W7 and W12 (r=0.926; p>0.0001). This correlation progressively increased with APAP use. A significance difference was found in concordance between P W12-W7 and P W12-D1 (p=0.046) within the pressure range ±2cmH2O. However there was no significant difference in concordance between P W12-W7 and P W12-W1. CONCLUSIONS: One week of APAP therapy seems sufficient to determine an effective and stable PAP level, within the pressure range ±2cmH2O.

Epworth Sleepiness Scale in obstructive sleep apnea syndrome--an underestimated subjective scale.

Excessive daytime sleepiness is a major symptom in obstructive sleep apnea syndrome (OSAS) and can be evaluated using both subjective and objective methods. The Epworth Sleepiness Scale (ESS) is a simple and validated questionnaire for assessing subjective daytime sleepiness in the context of sleep disorders. Although its subjective character may limit the accurate expression of daytime sleepiness, the clinical benefit of sequential ESS is clear and demonstrates how ESS scores evolve in individual patients and how these scores may relate to various parameters. In this context we compared the severity of daytime sleepiness reported at baseline visit with severity of baseline sleepiness assessed, retrospectively, after treatment with automatic positive airway pressure (APAP). We conducted a prospective study that included 66 patients evaluated in a sleep clinic diagnosed with OSAS. The diagnosis was confirmed by in-laboratory or portable sleep studies. Their mean age was 53.3 years and the majority were men (88%, n=58). The ESS was answered during the first interview (baseline daytime sleepiness). During follow-up visits, after APAP treatment, the patient was asked to assess baseline sleepiness, retrospectively, as well as post-treatment sleepiness. The mean baseline ESS score was 11.8, mean retrospective baseline ESS 15.4, with a mean difference of 3.55 (p<0.001 t-Test) and post-treatment ESS 7.3. There was no significant correlation between the difference in ESS score (baseline - retrospective baseline) with the average daily (hours) use of APAP, the apnea-hypopnea index (AHI), the minimal recorded SatO(2), disease duration, body mass index (BMI) and age. Our findings confirm that the severity of subjective sleepiness reported before treatment with positive airway pressure is often underestimated by patients with OSAS.

Pulmonary function tests in obese people candidate to bariatric surgery.

Obesity is considered one of the most serious public health problems of the modern world. Because it alters the relationship between the lungs, chest wall and diaphragm, it is to be expected that it impacts on the respiratory function. In Portugal, there is not much data about the relationship between obesity and pulmonary function. The aim of this study was to characterize respiratory function in morbidly obese patients and to evaluate whether weight loss in patients submitted to bariatric surgery affects pulmonary function tests (PFT). We conducted a retrospective study with 36 morbidly obese patients submitted to bariatric surgery, with a mean age of 40.6 years, 64% female and with a mean body mass index (BMI) of 49.7 kg/m². All patients were clinical and functionally evaluated before surgery and after their weight had stabilized following surgery. They underwent a complete pulmonary function testing with spirometry, lung volumes, carbon monoxide diffusing capacity (DLCO), maximum respiratory pressures and arterial blood gases analysis. Prior to surgery almost all the patients had functional respiratory changes, 34 had a decrease in functional residual capacity (FRC) 6 of whom a restrictive syndrome. Only 2 patients did not show any functional or arterial blood gas change. After bariatric surgery, BMI decreased to 34 kg/m² and there was a significant improvement in almost all functional parameters with resolution of restrictive disorders. Nevertheless, in 13 patients the FRC remained decreased. After weight loss, the only correlation found was between reduction of BMI and increased FRC (r = -0.371; p = 0.028). This study suggests a relationship between obesity and pulmonary restriction and a positive impact of bariatric surgery in PFT.

Outcome of COPD patients with mild daytime hypoxaemia with or without sleep-related oxygen desaturation.

The aim of the present study was to compare the evolution of pulmonary haemodynamics and of arterial blood gases in chronic obstructive pulmonary disease (COPD) patients with mild-to-moderate hypoxaemia, with or without sleep-related oxygen desaturation. COPD patients with daytime arterial oxygen partial pressure in the range 56-69 mmHg were included prospectively. Sleep-related oxygen desaturation was defined as spending > or = 30% of the nocturnal recording time with arterial oxygen saturation <90%. From the 64 patients included, 35 were desaturators (group 1) and 29 were nondesaturators (group 2). At baseline (t0), patients with sleep-related desaturation had a significantly higher daytime (mean +/- SD) arterial carbon dioxide partial pressure (Pa,CO2) (44.9 +/- 4.9 mmHg versus 41.0 +/- 4.1 mmHg, p=0.001) whereas mean pulmonary artery pressure (mPAP) was similar in the two groups. After 2 yrs (t2) of follow-up, 22 desaturators and 14 nondesaturators could be re-evaluated, including pulmonary haemodynamic measurements. None of the nondesaturator patients became desaturators at t2. The difference between the two groups in terms of daytime Pa,CO2 was still present at t2. The mean changes in mPAP from t0 to t2 were similar between the two groups, as were the rates of death or requirement for long-term oxygen therapy (American Thoracic Society criteria) during follow-up of up to 6 yrs. The presence of sleep-related oxygen desaturation is not a transitional state before the worsening of daytime arterial blood gases, but is a characteristic of some chronic obstructive pulmonary disease patients who have a higher daytime arterial carbon dioxide partial pressure. Such isolated nocturnal hypoxaemia or sleep-related worsening of moderate daytime hypoxaemia does not appear to favour the development of pulmonary hypertension, nor to lead to worsening of daytime blood gases.

A randomized trial of nocturnal oxygen therapy in chronic obstructive pulmonary disease patients.

The beneficial effects of nocturnal oxygen therapy (NOT) in chronic obstructive pulmonary disease (COPD) patients with mild-to-moderate daytime hypoxaemia (arterial oxygen tension (Pa,O2) in the range 7.4-9.2 kPa (56-69 mmHg)) and exhibiting sleep-related oxygen desaturation remains controversial. The effectiveness of NOT in that category of COPD patients was studied. The end points included pulmonary haemodynamic effects after 2 yrs of follow-up, survival and requirement for long-term oxygen therapy (LTOT). Seventy-six patients could be randomized, 41 were allocated to NOT and 35 to no NOT (control). The goal of NOT was to achieve an arterial oxygen saturation of >90% throughout the night. All these patients underwent polysomnography to exclude an associated obstructive sleep apnoea syndrome. The two groups exhibited an identical meansD daytime Pa,O2 of 8.4+/-0.4 kPa (63+/-3 mmHg) at baseline. Twenty-two patients (12 in the NOT group and 10 in the control group, p=0.98) required LTOT during the whole follow-up (35+/-14 months). Sixteen patients died, nine in the NOT group and seven in the control group (p=0.84). Forty-six patients were able to undergo pulmonary haemodynamic re-evaluation after 2 yrs, 24 in the NOT and 22 in the control group. In the control group, mean resting pulmonary artery pressure increased from 19.8+/-5.6 to 20.5+6.5 mmHg, which was not different from the change in mean pulmonary artery pressure in the NOT group, from 18.3+/-4.7 to 19.5+/-5.3 mmHg (p= 0.79). Nocturnal oxygen therapy did not modify the evolution of pulmonary haemodynamics and did not allow delay in the prescription of long-term oxygen therapy. No effect of NOT on survival was observed, but the small number of deaths precluded any firm conclusion. These results suggest that the prescription of nocturnal oxygen therapy in isolation is probably not justified in chronic obstructive pulmonary disease patients.

Sleep-related O2 desaturation and daytime pulmonary haemodynamics in COPD patients with mild hypoxaemia.

It has been hypothesized but not firmly established that sleep-related hypoxaemia could favour the development of pulmonary hypertension in chronic obstructive pulmonary disease (COPD) patients without marked daytime hypoxaemia. We have investigated the relationships between pulmonary function data, sleep-related desaturation and daytime pulmonary haemodynamics in a group of 94 COPD patients not qualifying for conventional O2 therapy (daytime arterial oxygen tension (Pa,O2) in the range 7.4-9.2 kPa (56-69 mmHg)). Nocturnal desaturation was defined by spending > or = 30% of the recording time with a transcutaneous O2 saturation < 90%. An obstructive sleep apnoea syndrome was excluded by polysomnography. Sixty six patients were desaturators (Group 1) and 28 were nondesaturators (Group 2). There was no significant difference between Groups 1 and 2 with regard to pulmonary volumes and Pa,O2 (8.4+/-0.6 vs 8.4+/-0.4 kPa (63+/-4 vs 63+/-3 mmHg)) but arterial carbon dioxide tension (Pa,CO2) was higher in Group 1 (6.0+/-0.7 vs 53+/-0.5 kPa (45+/-5 vs 40+/-4 mmHg); p<0.0001). Mean pulmonary artery pressure (Ppa) was very similar in the two groups (2.6+/-0.7 vs 2.5+/-0.6 kPa (19+/-5 vs 19+/-4 mmHg)). No individual variable or combination of variables could predict the presence of pulmonary hypertension. It is concluded that in these patients with chronic obstructive pulmonary disease with modest daytime hypoxaemia, functional and gasometric variables (with the noticeable exception of arterial carbon dioxide tension) cannot predict the presence of nocturnal desaturation; and that mean pulmonary artery pressure is not correlated with the degree and duration of nocturnal hypoxaemia. These results do not support the hypothesis that sleep-related hypoxaemia favours the development of pulmonary hypertension.