Reliability of automatic detection of AHI during positive airway pressure treatment in obstructive sleep apnea patients: A "real-life study"

INTRODUCTION

Automatic event detection (AED) of residual apnea-hypopnea index (AHI) by ventilators is a current practice in sleep and mechanical ventilation Units but this methodology has not been validated in an unselected population of OSA patients. Aim of the present study was to assess in a "real-life" condition the reliability of AED during PAP therapy by the in-built software compared to full polysomnography during follow-up.

METHODS

We enrolled 300 OSA patients (105 F; AHI 45.3 ± 27.8) already on Positive airway pressure (PAP) therapy: 53% of the patients were on CPAP while other modalities were used in the rest of the sample.

RESULTS

Overall, the built-in software identified residual obstructive AHI (AHIPAP) > 5, 10 or 15 in 18.7, 8.6 or 4.6% of patients, respectively. By using AHIPAP, 28.4% of patients were wrongly classified as "well controlled" despite a residual AHIPSG>5 (6% considering a residual AHIVENT >15); 7% of patients were classified as not controlled while AHIPSG was <5 (1.4% considering a residual AHIVENT >15). Type of ventilation, ventilator parameters, adherence to treatment and level of baseline or follow-up Epworth Sleepiness Scale score were similar between groups. The sensitivity and positive predicted values were very low. Positive likelihood ratio appears adequate only for residual AHIPAP ≥10, but negative likelihood ratio was inconclusive for all the cut-off considered.

DISCUSSION

The results of the present study suggest a more cautious approach in the follow-up of OSA patients, since a protocol based only on AED detection and symptoms assessment may not be accurate especially for AHIPAP<15.

SAS CARE 2 - a randomized study of CPAP in patients with obstructive sleep disordered breathing following ischemic stroke or transient ischemic attack

Objective/background

The benefit of Continuous Positive Airway Pressure (CPAP) treatment following ischemic stroke in patients with obstructive sleep-disordered breathing (SDB) is unclear. We set out to investigate this open question in a randomized controlled trial as part of the SAS-CARE study.

Patients/methods.

Non-sleepy patients (ESS < 10) with ischemic stroke or transient ischemic attack (TIA) and obstructive SDB (AHI ≥ 20) 3 months post-stroke were randomized 1:1 to CPAP treatment (CPAP+) or standard care. Primary outcome was the occurrence of vascular events (TIA/stroke, myocardial infarction/revascularization, hospitalization for heart failure or unstable angina) or death within 24 months post-stroke. Secondary outcomes included Modified Rankin Scale (mRS) and Barthel Index.

Results

Among 238 SAS-CARE patients 41 (17%) non-sleepy obstructive SDB patients were randomized to CPAP (n = 19) or standard care (n = 22). Most patients (80%) had stroke and were males (78%), mean age was 64 ± 7 years and mean NIHSS score 0.6 ± 1.0 (range: 0–5). The primary endpoint was met by one patient in the standard care arm (a new stroke). In an intent-to treat analysis disregarding adherence, this corresponds to an absolute risk difference of 4.5% or an NNT = 22. mRS and Barthel Index were stable and similar between arms. CPAP adherence was sufficient in 60% of evaluable patients at month 24.

Conclusion

No benefit of CPAP started three months post-stroke was found in terms of new cardio- and cerebrovascular events over 2 years. This may be related to the small size of this study, the mild stoke severity, the exclusion of sleepy patients, the delayed start of treatment, and the overall low event rate.

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No benefit of CPAP started 3 months post-stroke was found.

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A sufficient CPAP compliance was observed over 2 years in 60% of patients.

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Studies of CPAP in mild stroke need to be large and include long-term outcomes.

Comparison of two humidification systems for long-term noninvasive mechanical ventilation

There is no consensus concerning the best system of humidification during long-term noninvasive mechanical ventilation (NIMV). In a technical pilot randomised crossover 12-month study, 16 patients with stable chronic hypercapnic respiratory failure received either heated humidification or heat and moisture exchanger. Compliance with long-term NIMV, airway symptoms, side-effects and number of severe acute pulmonary exacerbations requiring hospitalisation were recorded. Two patients died. Intention-to-treat statistical analysis was performed on 14 patients. No significant differences were observed in compliance with long-term NIMV, but 10 out of 14 patients decided to continue long-term NIMV with heated humidification at the end of the trial. The incidence of side-effects, except for dry throat (significantly more often present using heat and moisture exchanger), hospitalisations and pneumonia were not significantly different. In the present pilot study, the use heated humidification and heat and moisture exchanger showed similar tolerance and side-effects, but a higher number of patients decided to continue long-term noninvasive mechanical ventilation with heated humidification. Further larger studies are required in order to confirm these findings.

Medico-legal implications of sleep apnoea syndrome: Driving license regulations in Europe

BACKGROUND

Sleep apnoea syndrome (SAS), one of the main medical causes of excessive daytime sleepiness, has been shown to be a risk factor for traffic accidents. Treating SAS results in a normalized rate of traffic accidents. As part of the COST Action B-26, we looked at driving license regulations, and especially at its medical aspects in the European region.

METHODS

We obtained data from Transport Authorities in 25 countries (Austria, AT; Belgium, BE; Czech Republic, CZ; Denmark, DK; Estonia, EE; Finland, FI; France, FR; Germany, DE; Greece, GR; Hungary, HU; Ireland, IE; Italy, IT; Lithuania, LT; Luxembourg, LU; Malta, MT; Netherlands, NL; Norway, EC; Poland, PL; Portugal, PT; Slovakia, SK; Slovenia, SI; Spain, ES; Sweden, SE; Switzerland, CH; United Kingdom, UK).

RESULTS

Driving license regulations date from 1997 onwards. Excessive daytime sleepiness is mentioned in nine, whereas sleep apnoea syndrome is mentioned in 10 countries. A patient with untreated sleep apnoea is always considered unfit to drive. To recover the driving capacity, seven countries rely on a physician's medical certificate based on symptom control and compliance with therapy, whereas in two countries it is up to the patient to decide (on his doctor's advice) to drive again. Only FR requires a normalized electroencephalography (EEG)-based Maintenance of Wakefulness Test for professional drivers. Rare conditions (e.g., narcolepsy) are considered a driving safety risk more frequently than sleep apnoea syndrome.

CONCLUSION

Despite the available scientific evidence, most countries in Europe do not include sleep apnoea syndrome or excessive daytime sleepiness among the specific medical conditions to be considered when judging whether or not a person is fit to drive. A unified European Directive seems desirable.

Effect of paced breathing on ventilatory and cardiovascular variability parameters during short-term investigations of autonomic function

Paced breathing (PB) around 0.25 Hz has been advocated as a means to avoid confounding and to standardize measurements in short-term investigations of autonomic cardiovascular regulation. Controversy remains, however, as to whether it causes any alteration in autonomic control. We addressed this issue in 40 supine, middle-aged, healthy volunteers by assessing the changes induced by PB (0.25 Hz for 8 min) on 1) ventilatory parameters, 2) the indexes of autonomic control of cardiovascular function, and 3) the spectral indexes of cardiovascular variability. Subjects were grouped into group 1 (n = 31), if spontaneous breathing was regular and within the high-frequency (HF) band (0.15-0.45 Hz), or group 2 (n = 9), if it was irregular or slow (< 0.15 Hz). In both groups, PB was accompanied by an increase in minute ventilation (both groups, P < 0.01), whereas tidal volume increased only in group 1 (P = 0.0003). End-tidal CO2 decreased by [median (lower quartile, upper quartile)] -0.2 (-0.5, -0.1)% (group 1, P < 0.0001) and -0.6 (-0.8, -0.5)% (group 2, P = 0.008). Mean R-R interval and systolic and diastolic pressure remained remarkably stable (all P > or = 0.13, both groups). No significant changes were observed in spectral indexes of R-R and pressure variability (all P > or = 0.12, measured only in group 1 to avoid confounding), except in the HF power of pressure signals, which significantly increased (all P < 0.05) in association with increased tidal volume. In conclusion, PB at 0.25 Hz causes a slight hyperventilation and does not affect traditional indexes of autonomic control or, in subjects with spontaneous breathing in the HF band, most relevant spectral indexes of cardiovascular variability. These findings support the notion that PB does not alter cardiovascular autonomic regulation compared with spontaneous breathing.

Nutritional status and airflow obstruction: two independent contributors to CO diffusing capacity impairment in COPD

Background. The association between weight loss and Chronic Obstructive Pulmonary Disease (COPD) has been recognised from many years. Based on the evidence that nutritional status reflects metabolic disturbances in COPD, the relationship between body mass index (BMI), severity of airflow obstruction and CO diffusing capacity (DLCO), that is the functional hallmark of emphysema, is relevant to the management of COPD phenotypes. Methods. We reviewed 104 patients with COPD (82 males), aged 66±9 years (mean±SD). Height averaged 165±8 cm, weight 71±16 Kg, FEV1 50±18 (% of predicted), RV 169±49%, and DLCO 56±26%. Multiple linear regression was performed using BMI, FEV1 and RV, as explanatory variables for DLCO. Patients were also classified into four groups according to BMI ≤ 18.5 (low), &gt; 18.5 and ≤ 25 (ideal), &gt; 25 and ≤ 30 (overweight), &gt; 30 (obese), and post-bronchodilator FEV1 &lt; 50%. Using this categorisation, a two-factor analysis of variance, testing for interaction and main effects (BMI and FEV1) was performed as confirmatory analysis for the association between BMI (kg/m2), FEV1% and DLCO%. Results. FEV1 and BMI were significantly and independently associated to DLCO according to the equation: DLCO = -18.32 + 0.65·FEV1 + 1.59·BMI (R2 = 0.40, p&lt;0.0001). The contribution of RV % to DLCO % was largely non-significant (p=0.16). A close relationship was found between BMI (kg/m2) and DLCO %, for all of the four BMI groups segregated by post-bronchodilator FEV1%, (p&lt;.0001). No interaction was found between these two factors (p=0.30). Conclusion. Nutritional status as assessed by BMI contributes substantially to impairment of DLCO independently of the severity of airflow obstruction. This data confirms the association between emphysematous process and weight loss in advanced COPD, independent of the airflow obstruction severity.

The treatment of Sleep Apnea Syndrome: looking for new answers for old problems

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Sleep disordered breathing in patients with chronic obstructive pulmonary disease

Sleep has effects on breathing, including changes in respiratory control, airways resistance and muscular contractility. These sleep-related modifications in the respiratory system do not induce adverse effects in healthy subjects, but may cause problems in patients with chronic obstructive pulmonary disease (COPD). Hypo-ventilation causes the most important gas-exchange alteration during sleep in COPD patients, leading to hypercapnia and hypoxemia, especially during rapid-eye-movement (REM) sleep. Blood gases alterations lead to increased arousals, sleep disruption, pulmonary hypertension and higher mortality. The presence of other sleep-related breathing disorders, like sleep apnea syndrome, may induce a more pronounced impairment of gas exchange, both during sleep and wakefulness, and development of symptoms like excessive daytime somnolence. Nocturnal oximetry is recommended to evaluate gas exchange during sleep in COPD patients. Sleep studies are usually indicated when there is a possibility of sleep apnea or obesity-hypoventilation syndrome. The role of non-invasive mechanical ventilation in managing COPD patients with nocturnal hypoventilation is discussed.

Levodropropizine does not affect P0.1 and breathing pattern in healthy volunteers and patients with chronic respiratory impairment

To evaluate whether the peripherally acting antitussive levodropropizine could affect the respiratory drive and the breathing pattern, we performed a double-blind, randomised, cross-over trial in 12 healthy volunteers and 12 patients with chronic respiratory impairment associated with chronic obstructive pulmonary disease. Levodropropizine 6% drops (at the recommended dose for adults) or placebo were administered orally t.i.d. for 10 consecutive administrations. Mouth occlusion pressure (P0.1), minute ventilation (V(e)), tidal volume (V(t)), respiratory rate (RR), mean inspiratory flow (V(t)/T(i)), end-tidal CO(2) (EtCO(2)), oxygen saturation (SaO(2)), forced expiratory volume in 1 s (FEV(1)), and the response to a hypercapnic stimulus were measured before and 1 h after the first and the last drug administration. Levodropropizine did not modify P0.1 in basal conditions and after a hypercapnic stimulus, either in healthy volunteers or in patients. In parallel, levodropropizine did not significantly affect V(t), RR, V(e), V(t)/T(i) and EtCO(2) in both the populations. Minor changes were induced by levodropropizine on SaO(2) in healthy volunteers, which despite a statistical difference, were too low to gain a clinical significance. These results confirmed the respiratory safety of levodropropizine 6% drops administered at the recommended dosage either in healthy volunteers or patients with chronic respiratory impairment.

Orthopnea and inspiratory effort in chronic heart failure patients

STUDY OBJECTIVE

Orthopnea is a typical feature of patients with chronic heart failure (CHF), the factors contributing to it are not completely understood. We investigated changes in dyspnea and other respiratory variables, induced by altering posture (from sitting to supine) in 11 CHF patients (NYHA classes II-IV) and 10 control subjects.

METHODS AND RESULTS

We measured dyspnea (Borg scale) the diaphragm pressure time product per minute (PTPdi/m, index of metabolic consumption), and mechanical properties of the lung (lung compliance (C,L) and resistances (R,L). CHF patients also underwent a trial of non-invasive mechanical ventilation (NIMV) in the supine position in order to ascertain whether unloading the inspiratory muscles could somehow relieve dyspnea. While sitting the PTPdi/min was significantly higher in CHF patients than in controls (181 +/- 54 cm H2O x s/min vs. 96 +/- 32; P<0.05). Assuming a supine position caused no major changes in controls, whereas CHF patients showed a significant worsening in dyspnea, a rise in PTPdi/min (243 +/- 97 p<0.01) and R,L (4.7 +/- 1.2 cm H2O/L x s sitting vs. 7.9 +/- 2.5 supine; P<0.01) and a decrease in C,L (0.08 +/- 0.02 L/cm H2O sitting vs. 0.07 +/- 0.01 supine; P<0.05). Applying NIMV to supine CHF patients significantly reduced the PTPdi/min to 81 +/- 42 (P<0.001). Changes in dyspnea, produced by varying position or applying NIMV, were significantly correlated with PTPdi/min (r=0.80, P<0.005 and r=0.58, P<0.01, respectively).

CONCLUSIONS

CHF patients had a higher PTPdi/min than controls when sitting, and assuming a supine position induced severe dyspnea, a large rise in R,L, and a reduction in C,L so that PTPdi/min increased further. Orthopnea was strongly correlated with the increased diaphragmatic effort.

Physiologic evaluation of 4 weeks of nocturnal nasal positive pressure ventilation in stable hypercapnic patients with chronic obstructive pulmonary disease

BACKGROUND

The long-term daily use of noninvasive mechanical ventilation (NIMV) to treat chronic respiratory failure in chronic obstructive pulmonary disease (COPD) patients is not widely recommended, partly because of a lack of clear clinical results and partly because the physiological mechanisms by which the daily application of NIMV would be helpful in these patients have not yet been clarified.

OBJECTIVES

We designed a physiological study in order to assess the effects of supervised long-term NIMV on gas exchange, respiratory muscle function, pulmonary mechanics and to ascertain the possible effect of the treatment in responders and nonresponders.

METHODS

Fourteen consecutive inpatients with stable hypercapnic COPD (pH = 7.37 +/- 0.01; PaCO(2) = 56.73 +/- 6.48 mm Hg) underwent 4 weeks of nocturnal NIMV delivered with a bilevel ventilator 'physiologically' set to reduce tidal transdiaphragmatic pressure (Pdi) by at least 50% and the amount of dynamic intrinsic positive end-expiratory pressure by 70%. Various measurements were compared with those obtained in a control group of consecutive patients with comparable baseline characteristics who refused NIMV and underwent breathing exercises for the same period of time.

RESULTS

By the end of the 4 weeks NIMV had induced a slight but significant (p < 0.01) reduction in resting PaCO(2) (53.78 +/- 5.64 mm Hg) associated with a decrease in the pressure time product of the diaphragm per minute (from 172 +/- 60 to 136 +/- 61 cm H(2)O/l/s; p < 0.05). This latter value was primarily due to a significant shortening of the inspiratory duty cycle, while Pdi and lung mechanics were not modified. Eight of the 13 NIMV-treated patients (1 dropped out for nonmedical reasons) had a clear reduction in PaCO(2) (>3 mm Hg or >5% from enrollment) and were classified as responders. The acute reduction in PaCO(2) during the first trial with NIMV resulted to be a strong index of the final response. The subgroup of responders had a significantly increased maximal Pdi (from 41 +/- 19 to 49 +/- 23 cm H(2)O, p < 0.05) and an enhanced ability of the ventilatory pump to clear CO(2) (9.7 +/- 3.4 vs. 7.2 +/- 2.9 cm H(2)O x s/min; p < 0.01). No significant changes were observed in the control group.

CONCLUSIONS

These results suggest that in a remarkable and identifyable proportion of patients with stable hypercapnic COPD, nocturnal NIMV may decrease resting PaCO(2), reraising the role of chronically supporting the respiratory pump.

Salbutamol delivery during non-invasive mechanical ventilation in patients with chronic obstructive pulmonary disease: a randomized, controlled study

OBJECTIVE

We investigated the clinical response to equivalent doses of salbutamol delivered, via metered dose inhaler (MDI) during non-invasive mechanical ventilation (NIMV-MDI), during spontaneous breathing using a spacer (MDI-Spacer), and also during intermittent positive pressure breathing (IPPB).

SETTING

A respiratory intensive care unit.

DESIGN

Prospective, randomized, and placebo-controlled study.

PATIENTS

Eighteen stable patients with chronic obstructive pulmonary disease (mean FEV1=38.5+/-8.8% predicted).

RESULTS

Overall salbutamol administration induced, compared to placebo, a significant improvement in FEV1, irrespective of the mode of administration (+7.9+/-7.1% or +108+/-91 ml for IPPB, +9.6+/-8.8% or 112+/-67 ml for MDI-NIMV (inspiratory pressure=14.3+/-1.8 cmH2O; expiratory pressure=none), and +10.8+/-11.4% or 119+/-114 ml for MDI-Spacer, respectively). DeltaFVC significantly increased from placebo only in MDI-NIMV (+214+/-182 ml P=0.02). A second set of experiments performed in eight patients to ascertain the possible effect of NIMV on pulmonary function tests, showed a significant improvement from baseline values in FVC both after the delivering of placebo or salbutamol via NIMV-MDI (+206+/-147 ml and 208+/-145, respectively). FEV1 significantly increased only after salbutamol. No changes in gas exchange were observed after bronchodilator delivery.

CONCLUSIONS

We show that delivery of bronchodilators via MDI with a spacer chamber during NIMV is feasible and induces a significant bronchodilator effect compared to placebo, even though it may be slightly less effective than the classical delivery system (MDI-Spacer).

Is It Safe for Patients With Chronic Hypercapnic Respiratory Failure Undergoing Home Noninvasive Ventilation To Discontinue Ventilation Briefly?

STUDY OBJECTIVES

A brief discontinuation (< 1 week) of long-term ventilation may be necessary in patients who are not totally ventilator-dependent in cases of technical problems, intolerable nasal irritation, upper airway congestion, or travel. We examined the incidence, timing, and causes of possible clinical deterioration after a brief withdrawal of ventilation in patients with chronic respiratory failure (CRF) who were well-established on long-term noninvasive mechanical ventilation (NIMV).

STUDY DESIGN

Prospective clinical study.

PATIENTS

Eleven inpatients in clinically stable condition (COPD, 6 patients; and restrictive thoracic disease [RTD], 5 patients) who had severe CRF (PaCO(2), > 50 mm Hg) and had been receiving NIMV for (mean +/- SD) 19.3 +/- 5.3 months were enrolled.

INTERVENTIONS AND MEASUREMENTS

Arterial blood gas (ABG) levels, maximal inspiratory pressure (PImax), breathing pattern, dyspnea rating, and life symptoms (measured by a questionnaire) were recorded daily after NIMV withdrawal for 6 days or until the patients showed clinical and/or ABG level deterioration. Pulmonary function tests were performed and neuromuscular drive was measured at the beginning and the end of the study.

RESULTS

Five of the 11 patients (45.4%) [COPD, 3 patients; and RTD, 2 patients] were reconnected to a ventilator before the scheduled time because of ABG level deterioration. Despite these changes, none of the patients reported severe worsening of symptoms or other medical complications. The patients whose ABG levels worsened had statistically significant decreases in tidal volume and PImax, suggesting that the development of alveolar hypoventilation was related to respiratory muscle weakness.

CONCLUSIONS

A brief discontinuation of NIMV in patients who were affected by chronic hypercapnic respiratory failure and were well-established on NIMV is associated with a relatively high incidence of ABG level worsening due to the development of alveolar hypoventilation. If NIMV must be briefly interrupted for clinical reasons, the patient should be monitored closely for abrupt worsening, and prompt technical intervention should be provided if a ventilator fails.

Periodic breathing in heart failure patients: testing the hypothesis of instability of the chemoreflex loop

In this study, we applied time- and frequency-domain signal processing techniques to the analysis of respiratory and arterial O(2) saturation (Sa(O(2))) oscillations during nonapneic periodic breathing (PB) in 37 supine awake chronic heart failure patients. O(2) was administered to eight of them at 3 l/min. Instantaneous tidal volume and instantaneous minute ventilation (IMV) signals were obtained from the lung volume signal. The main objectives were to verify 1) whether the timing relationship between IMV and Sa(O(2)) was consistent with modeling predictions derived from the instability hypothesis of PB and 2) whether O(2) administration, by decreasing loop gain and increasing O(2) stores, would have increased system stability reducing or abolishing the ventilatory oscillation. PB was centered around 0.021 Hz, whereas respiratory rate was centered around 0.33 Hz and was almost stable between hyperventilation and hypopnea. The average phase shift between IMV and Sa(O(2)) at the PB frequency was 205 degrees (95% confidence interval 198-212 degrees). In 12 of 37 patients in whom we measured the pure circulatory delay, the predicted lung-to-ear delay was 28.8 +/- 5.2 s and the corresponding observed delay was 30.9 +/- 8.8 s (P = 0.13). In seven of eight patients, O(2) administration abolished PB (in the eighth patient, Sa(O(2)) did not increase). These results show a remarkable consistency between theoretical expectations derived from the instability hypothesis and experimental observations and clearly indicate that a condition of loss of stability in the chemical feedback control of ventilation might play a determinant role in the genesis of PB in awake chronic heart failure patients.

Erectile dysfunction in men with obstructive sleep apnea: an early sign of nerve involvement

Erectile dysfunction (ED) is common in men with obstructive sleep apnea (OSAS) but no completely convincing hypotheses about the underlying pathogenic mechanisms have been published in the literature. The aims of the present study were to assess the presence of ED in a group of OSAS patients without daytime respiratory failure and to determine whether this dysfunction was related to peripheral nerve involvement. Evaluation of the bulbocavernosus reflex (BCR) and the somato-sensory evoked potentials of pudendal nerve (PSEPs), the most widely established method of documenting pudendal neuropathies as being the cause of impotence, was performed in 25 patients. Data on BCR were compared with those of 25 healthy males volunteers matched for age. BCR was altered in 17 patients: in 6 it was elicited while in 11 it had a prolonged latency and reduced amplitude. Patients with altered BCR presented an higher AHI, an higher percentage of sleep time spent with SaO2 <90% (TST90) and a lower daytime PaO2. Six patient had clinically silent neurophysiological signs of mild polyneuropathy. The degree of OSAS and gas exchange alteration was more severe in patients with polyneuropathy than in those with isolated BCR alteration. ED is a common finding in OSAS patients and this alteration seems to be related to a nerve dysfunction. The development of nerve dysfunction is associated with a more severe degree of OSAS and nocturnal hypoxia.

Physiologic evaluation of noninvasive mechanical ventilation delivered with three types of masks in patients with chronic hypercapnic respiratory failure

OBJECTIVE

The efficacy of noninvasive mechanical ventilation (NIMV) in improving breathing pattern and arterial blood gases (ABG) in hypercapnic patients has been well documented; however, little attention has been given to the choice of the interface and the ventilatory mode. We evaluated the effects of three types of masks and two modes of ventilation on patients' ABG, breathing pattern, and tolerance to ventilation.

DESIGN

Prospective randomized study.

SETTING

Two respiratory weaning centers.

PATIENTS

A total of 26 stable hypercapnic patients (pH, 7.38 +/- 0.04; PaCO2, 59.2. +/- 10.9 torr) had not received NIMV and were affected by restrictive thoracic disease or obstructive pulmonary disease.

INTERVENTIONS

Three 30-min runs of NIMV, delivered using volume-assisted (n = 13) or pressure-assisted modes of partial mechanical support (n = 13), were performed in random order with a full-face mask, a nasal mask, and nasal plugs.

MEASUREMENTS

ABG, breathing pattern, and patients' tolerance to ventilation.

MAIN RESULTS

Compared with spontaneous breathing, the application of NIMV significantly improved ABG and minute ventilation, irrespective of the ventilatory mode, the underlying pathology or the type of mask. Overall, a nasal mask was better tolerated than the other two interfaces (p < .005 vs. nasal plugs and full-face mask). PaCO2 was significantly lower (p < .01) with a full-face mask or nasal plugs than with a nasal mask (49.5 +/- 9.4 torr, 49.7 +/- 8 torr, and 52.4 +/- 11 torr, respectively). Minute ventilation was significantly higher with a full-face mask than with a nasal mask because of an increase in tidal volume. No differences were observed in tolerance to ventilation, ABG, or breathing pattern, using assist control or pressure-assisted modes.

CONCLUSIONS

In this physiologic study, we have shown that in patients with hypercapnic respiratory failure, irrespective of the underlying pathology, the type of interface affects the NIMV outcome more than the ventilatory mode.

Pulmonary function and complications following chemotherapy and stem cell support in breast cancer

Pulmonary complications are frequent in patients treated with high-dose chemotherapy and autologous bone marrow transplantation for breast cancer or other solid tumours. This study analyses the development of lung toxicity, changes in respiratory function and occurrence of clinical symptoms in a group of 24 patients (mean age 46+/-7 yrs) who underwent high-dose sequential chemotherapy (HDS) with autologous peripheral blood stem cell (PBSC) support for high risk breast cancer. Clinical examination, chest radiography and lung function tests were performed before the HDS and 1 and 3 months following transplantation. Only one patient developed acute interstitial pulmonary disease which resolved after prednisone therapy. No patients developed infectious complications after transplantation. Baseline respiratory function was normal for most of the parameters. Only lung diffusing capacity of the lung for carbon monoxide (TL,CO) and maximal inspiratory pressure were below the normal range. Following PBSC transplantation only one patient had an altered vital capacity while 72.3% of patients had reduced TL,CO values at 1 month and 54.5% at 3 months after transplantation. Maximal expiratory flow at 25% forced vital capacity, TL,CO and maximal expiratory pres-sure were significantly reduced after 1 month but recovered slightly by 3 months. Arterial oxygen tension between baseline and both follow-up evaluations declined significantly in patients seropositive for human cytomegalovirus. It is concluded that this high-dose sequential chemotherapy regimen is acceptably safe since no pulmonary related mortality or respiratory infectious complications were observed. The only lung function alteration induced was an isolated diffusing capacity of the lung for carbon monoxide impairment, clinically negligible and partially recovered within 3 months.

Identification of chronic heart failure patients at risk of Cheyne-Stokes respiration

Chronic heart failure (CHF) patients frequently show sleep-disordered breathing consisting of periodic breathing (PB) and Cheyne-Stokes respiration (CSR) with central sleep apnoea (CSA). Since the diagnosis of sleep-disordered breathing, in CHF patients, can be made only by means of full polysomnography, the aim of the present study was to evaluate whether or not daytime respiratory function can identify patients at risk of nocturnal PB and/or CSR/CSA. Twenty-seven patients (mean age 54 +/- 8.5 yrs), eight New York Heart Association Functional Class (NYHAFC) II, 17 NYHAFC III and two NYHAFC IV, with severe cardiac failure (cardiac output 2.0 +/- 0.66 L.min-1, ejection fraction 22.5 +/- 5.77%, pulmonary capillary wedge/pressure 23 +/- 9.05 mmHg). Mouth occlusion pressure (P0.1)/maximal inspiratory pressure (MIP) was significantly higher in patients with nocturnal CSR/CSA (5.04 +/- 1.49 versus 3.24 +/- 2.13%, analysis of variance (ANOVA) 0.03), whereas their arterial carbon dioxide tension (Pa,CO2) was significantly lower (4.15 +/- 0.56 (31.2 +/- 4.23 mmHg) versus 4.67 +/- 0.53 kPa (35.1 +/- 4 mmHg), ANOVA 0.02). Logistic regression analysis demonstrated that CSR/CSA occurrence may be predicted by daytime measurement of P0.1/MIP and Pa,CO2 (p = 0.04 and 0.01 respectively; odds ratio 1.93 and 0.76 respectively). The sensitivity was 70%, specificity 76.5%, false positive rate 36.4%, false negative rate 18.8%, positive predictive value 71.4% and negative predictive value 85%. This model seems useful for predicting respiratory pattern changes in chronic heart failure patients and the authors suggest that polysomnography be performed only in high-risk patients, saving costs and the resources of sleep laboratories.

The development of hyperventilation in patients with chronic heart failure and Cheyne-Strokes respiration: a possible role of chronic hypoxia

AIM

To analyze the relationship between daytime respiratory and cardiac function in patients with compensated chronic heart failure (CHF) with and without periodic breathing (PB) or Cheyne-Stokes respiration (CSR).

PATIENTS

We studied 132 patients (female, 13%; mean age, 53+/-8 years; body mass index, 25.9+/-3.5 kg/m2; left ventricular ejection fraction <40%; 23% in New York Heart Association class I, 43% in class II, and 34% in class III-IV).

METHODS

Measurement of pulmonary function and blood gases, hemodynamic evaluation, analysis of breathing profile, echocardiography, recording of ECG, beat-to-beat arterial oxygen saturation, and respiration during spontaneous breathing.

RESULTS

Fifty-eight percent of patients showed PB or CSR. Patients with PB or CSR have greater cardiac function impairment. Mean values of lung volumes and PaO2 were similar in the three groups of patients considered. In contrast, patients with PB or CSR had an increased minute ventilation and reduced PaCO2 values. Interestingly, patients with PB or CSR had lower values of arterial content of O2 and systemic oxygen transport (SOT) than patients with a normal breathing pattern (SOT, 394+/-9.8, 347+/-9.6, 438+/-11 mL of O2/min/m2, respectively; analysis of variance p<0.001). Weak correlations were found among lung volumes, blood gases, and cardiac function parameters: ie, vital capacity was correlated inversely with pulmonary capillary wedge pressure (PCWP) (-0.25; p<0.05); PaCO2 with PCWP (r=0.26; p<0.05), lung-to-ear circulation time (LECT) (r=-0.4; p<0.05), SOT (r=-0.33; p<0.0001), and cardiac index (CI) (r=0.27; p=0.003). Multiple regression analyses showed that arterial PCO2 was significantly correlated with SOT, LECT, and CI (r=0.51; r2=0.26; p<0.000001); the correlation became stronger considering only CSR patients (r=0.64; r2=0.4; p<0.001).

CONCLUSIONS

Our study shows that patients with daytime breathing disorders have chronic hypocapnia. A reduced SOT may be one of the stimuli determining increased minute ventilation in these patients.

Chronic respiratory failure in a patient with type I Arnold-Chiari malformation (ACM1) and syringomyelia

We present the case of a young adult with type I Arnold-Chiari malformation (AMC1) and syringomyelia who developed central sleep apnoea and chronic respiratory failure, successfully treated with nocturnal noninvasive positive pressure ventilation ventilation (NIPPV). An extensive syringomyelic cavity (from bulbar to L4 segment) with severe impairment of the IX cranial nerve was documented and remains, although reduced, after the neurosurgical treatment. At baseline evaluation, the patient showed a moderate restrictive ventilatory defect, severe hypercapnic respiratory failure, abnormal control of breathing characterized by the absence of response to hypoxia and hypercapnia, and severe nocturnal central apnoeas. Nocturnal NIPPV was then started in the A/C mode with an improvement in blood gas values. Further evaluations were performed 10 and 18 months later. A progressive significant improvement of lung volumes, both in sitting and supine position, associated with a slight improvement of blood-gas values were observed. Nonetheless, the breathing pattern abnormalities persisted. Polysomnographic evaluation during mechanical ventilation showed a normalization of breathing pattern with arterial oxygen saturation (SaO2) > 90% throughout the night.

The efficacy of noninvasive mechanical ventilation on nocturnal hypoxaemia in Duchenne's muscular dystrophy

The aim of this 2 yr follow-up study was to evaluate the efficacy of nocturnal noninvasive mechanical ventilation in a group of 10 Duchenne's muscular dystrophy (DMD) patients who desaturated during the night but had normal daytime blood gases: mean (range) age 18.3 (15-22) yrs; mean (SD) vital capacity (VC) 752.5 (460-1,308) mL; mean time in bed (TIB) with arterial oxygen saturation (Sa,O2) < 90% 22.8% of total TIB (range: 16.6-32.0); mean arterial oxygen tension (Pa,O2) 10.3 (9.3-11.7) kPa (78 (70.0-87.8) mmHg); mean arterial carbon dioxide tension (Pa,CO2) 5.9 (4.8-6.5) kPa (44.3 (36.3-48.5) mmHg). All the patients were noninvasively ventilated during the night with a bilevel positive pressure ventilation (BiPAP) devise in spontaneous mode in order to correct the episodes of nocturnal desaturation. Nocturnal Sa,O2 values normalized during nocturnal noninvasive mechanical ventilation, and daytime sleep-disordered breathing disappeared, for the entire study period. No statistically significant differences were observed between baseline and follow-up daytime blood gas values, although a slight increase in Pa,O2 was found. During the follow-up, VC declined at a rate of 79.1 +/- 25 mL.yr-1, less than that generally reported in the past in untreated patients in the same age range. In conclusion, our data suggest that patients with advanced Duchenne's muscular dystrophy with pronounced nocturnal desaturation, not fulfilling criteria for imperative ventilation, could be successfully treated with "elective" nocturnal ventilation with immediate benefits consequent to the correction of the nocturnal blood gas anomalies and with long-term benefits related to the preservation of residual respiratory function, delay of development of chronic hypercapnia and thus the requirement for imperative mechanical ventilation.

Pulmonary complications and respiratory function changes after bone marrow transplantation in children

We prospectively assessed the frequency of pulmonary complications and the natural course of lung function after bone marrow transplantation (BMT), as well as the effect of several risk factors in a homogeneous group of 39 children who underwent allogeneic or autologous BMT for haematological malignancies between 1992 and 1995. Four patients developed pneumonia within the first 3 months and three 3-6 months after BMT. A considerable percentage of acute bronchitis was recorded throughout the follow-up. Three patients died after the 6 month visit because of pneumonia (two patients) and pulmonary aspergillosis (one patient). No patients had obstructive lung disease syndrome. At 3 months after BMT, forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and transfer factor of the lung for carbon monoxide (TL,CO) significantly decreased, but FEV1/FVC ratio and maximal expiratory flow at 25% of FVC remained unchanged, suggesting a restrictive defect with diffusion impairment. At 18 months, there was a progressive recovery in lung function, although only 11 patients had normalized. Seropositivity for cytomegalovirus had a significant effect on lung function whereas graft-versus-host disease also had an effect, although it was not statistically significant. Baseline respiratory function, type of transplant, type of conditioning regimen and respiratory infections did not significantly affect the outcome of BMT. The high frequency of severe lung function abnormalities found in this study, suggests a careful functional monitoring in all subjects undergoing bone marrow transplantation, even in the absence of respiratory symptoms.

Obstructive sleep apnoea syndrome: is the "half-night polysomnography" an adequate method for evaluating sleep profile and respiratory events?

Recently, to reduce the costs of polysomnography, split-night studies have been introduced into routine practice: the first part of the night is used to make the diagnosis of obstructive sleep apnoea syndrome (OSAS) and the second part to achieve an appropriate level of continuous positive airway pressure. Since this split-night protocol has not yet been validated by the comparison of polysomnographic pictures obtained in the first and second parts of the night, the aim of this study was to evaluate sleep profile and respiratory disturbances in the first part (PSG1) and second (PSG2) portion of a standard full-night polysomnographic examination (PSGtot) in a group of OSAS patients. Twenty nine consecutive OSAS patients, aged 54+/-10 yrs; body mass index (BMI) 40+/-6 kg x m(-2) (mean+/-SD values), were studied by separate analyses of PSG1, PSG2 and PSGtot. PSG1 was found to have a low sensitivity value (66%). A significant difference was found between apnoea-hypopnoea indices (AHI) recorded in PSG1, PSG2 and PSGtot (mean+/-SD, AHI1 33+/-27, AHI2 45+/-28, AHItot 40+/-25 events x h(-1), respectively; p<0.01). A strong correlation was observed between AHItot and AHI1 (r=0.89) and between AHItot and AHI2 (r=0.92), but a weaker correlation between AHI1 and AHI2 (r=0.66). These correlations became weaker when patients were subdivided into two different classes on the basis of disease severity. PSG1 was representative of PSGtot and similar to PSG2 only in those patients with rapid eye movement (REM) phase sleep in the first part of the night. We conclude that split-night protocols are not appropriate for evaluating sleep-disordered breathing in obstructive sleep apnoea syndrome patients when rapid eye movement phase sleep does not occur in the first part of the night.

Pulmonary function in children with systemic lupus erythematosus

BACKGROUND

Abnormalities of pulmonary function have been found in children with systemic lupus erythematosus (SLE) even in the absence of clinical or radiographic evidence of pulmonary involvement. It is unknown whether these abnormalities represent an early sign of progressive lung disease or whether they are associated with disease activity.

METHODS

After a mean of 4.5 years, respiratory function (forced vital capacity (FVC) and single breath gas transfer factor (TLCO)) and disease activity were reexamined in 13 of 15 previously studied children with SLE. Disease activity was assessed by a validated index of SLE activity (SLE activity measure (SLAM)).

RESULTS

In spite of the high prevalence of abnormalities of respiratory function at the baseline investigation, no chest radiographic abnormalities or overt clinical signs of lung disease were found at baseline, in the interval between the two investigations, or at the re-evaluation in any patient. From baseline to the second investigation the mean value of SLAM decreased and there was a trend toward an improvement in FVC and TLCO. TLCO was more severely impaired than FVC, being found as an isolated abnormality in a high percentage of patients (45% at baseline and 35% at follow up). There was a relationship between baseline TLCO and disease activity, expressed as a SLAM score. Moreover, there was a correlation between the changes in the SLAM score from baseline to the second investigation and the corresponding changes in the TLCO value, but not with the corresponding changes in the FVC value.

CONCLUSIONS

In this series of patients the decrease in SLE activity from the first to the second investigation was associated with an improvement in pulmonary function. The presence of early isolated functional abnormalities was not associated with subsequent development of lung disease.

Evaluation of methacholine dose-response curves by linear and exponential mathematical models: goodness-of-fit and validity of extrapolation

Several models have been proposed to analyse dose-response curves recorded in bronchoprovocation challenge tests. The aims of the present work were: 1) to investigate which model (linear vs exponential) and which minimization method (trials and errors vs Levenberg-Marquardt) gives better results in terms of data interpolation (goodness-of-fit); and 2) to verify the validity of extrapolation by comparing forced expiratory volume in one second (FEV1) observed after 4 mg methacholine with values extrapolated after truncation of the curves at 2 mg. For these purposes, methacholine dose-response curves were obtained in 832 subjects from a random population sample, as part of the European Community Respiratory Health Survey (ECRHS) in Italy. Methacholine was inhaled up to a maximum dose of 6 mg by dosimeter technique. The coefficient of determination (r2) was significantly higher with the exponential model (0.81 +/- 0.22; mean +/- SD) than with the linear model (0.69 +/- 0.27). With both models, extrapolated values were usually lower than observed values. As a consequence, a 20% fall in FEV1 with respect to postsaline FEV1 was observed in only 24% and 21% of the tests, where a 20% fall had been predicted, respectively, according to the linear and exponential model. In conclusion, exponential models are better than linear models with respect to data interpolation of methacholine dose-response curves. However, they are worse with respect to extrapolation to higher doses. With any model, extrapolation of dose-response curves by one doubling-dose should be avoided.

Breathing during sleep in myasthenia gravis

The aim of this study was to assess breathing patterns during sleep in patients with generalized mild myasthenia gravis. Fourteen patients (13 F; 1M, age range 20-40 years) in a stable clinical and functional state underwent a sleep questionnaire, baseline respiratory function tests and standard nocturnal polysomnography. All of the patients had normal daytime blood-gas values, except one who showed mild hypoxemia. No patient complained of disturbed sleep; six patients reported snoring. In five patients nocturnal polysomnography showed the occurrence of short and infrequent central apneas mainly during REM sleep, together with a drop in HbSaO2 levels of more than 5% of the baseline wakefulness value. Our data indicate that, in patients with mild generalized MG in a stable functional state, breathing pattern instability during sleep is infrequent and, when it occurs, is mild and mainly related to REM sleep.

Airway reactivity in parents of infants and young children with recurrent wheeze: a case-control study

Increased airway reactivity has been found in family members of school age children and adults with asthma. As the relation between recurrent wheeze in infancy and bronchial reactivity is not yet clear, it was decided to test bronchial reactivity to methacholine in both parents of 50 preschool age children with recurrent wheeze and in 200 population based controls matched for sex, age, smoking habits, and atopy. Wheezy children fulfilled the following criteria: first attack of wheezing before the age of 2 years, at least four wheezing episodes triggered by a respiratory infection, negative skin prick tests, and no symptoms related to allergy. Four parents and five controls did not undergo the methacholine challenge because their forced expiratory volume in one second was < 80% of the predicted value. Methacholine reactivity was not significantly different in parents and controls. In summary, an increased bronchial responsiveness was not found in parents of infants and young children with recurrent wheeze triggered by infection.

Reference values of arterial oxygen tension in the middle-aged and elderly

The lack of available reference values of arterial PO2, particularly for elderly persons, led us to study a sample of 194 normal nonsmoking subjects, equally distributed over all age ranges from 40 to 90 yr. The radial artery was punctured and blood samples were taken and analyzed on an automated, computerized gas-analyzer. The trend of the mean values of PaO2 in the 5-yr class intervals of age showed a clear decline up to the 70- to 74-yr class, and then an inversion. The two regression lines intersecting at this point provided a better fit to the data than did a single regression line (R22 - R12 = 0.918 - 0.678 = 0.24; F = 20.49, p = 0.0027). The relationship of PaO2 with age was thus subsequently considered for the two subgroups (40 to 74 yr; > or = 75 yr) identified on the basis of this cutoff. Because of the significant influence on Pao2 of age, body-mass index (BMI), and PaCO2 in the group 40 to 74 yr of age, the following reference equation was constructed: Pao2 (mm Hg) = 143.6 - (0.39 . age) - (0.56 . BMI) - (0.57 . PaCO2); R2 = 0.28; SEE = 7.48; p < 0.0001. For subjects > or = 75 yr old, for whom there was no correlation with age, BMI, or PaCO2, only the mean +/- SD and 5th percentile of PaO2 were reported (83.4 +/- 9.15 mm Hg and 68.4 mm Hg, respectively). PaCO2 values were not correlated with either age or BMI; the mean +/- SD was 35.79 +/- 3.87 mm Hg.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic respiratory symptoms, bronchial responsiveness and dietary sodium and potassium: a population-based study

A possible relationship between Na+ intake and increased prevalence and mortality from asthma and chronic obstructive pulmonary disease (COPD) has been suggested but not clearly proven for several reasons (difficulty in assessing Na+ and K+ both by 24 h excretion and dietary recall, too small an effect of these ions on the pathology, and the role of potential confounders). We wanted to determine the relationship of Na+ and K+ intake, assessed by means of a 7 day recall, with chronic respiratory symptoms and bronchial responsiveness in a sample of the general population. Two hundred and five subjects were studied, with complete dietary and respiratory questionnaires, and baseline respiratory function tests, together with a subsample of 146 subjects who underwent histamine challenge. The 7 day recall consisted of two parts: the first assessed discretionary Na+; and the second assessed Na+ and K+ contained in food. The whole sample was split into two groups based on the levels of consumption, and the statistical analysis was performed contrasting the three lower quartiles vs the highest. Smoking habit, social economic status, age and body mass index (BMI) were not confounders for Na+ and K+ intake. The prevalence of symptomatic subjects and baseline respiratory function values were not significantly different in the two groups of quartiles for Na+ and K+. Baseline respiratory values and dose-response slope of the subsample were also not significantly different. We did not prove a relationship between these dietary factors and either bronchial responsiveness or chronic respiratory symptoms. Although we consider that our questionnaire is more reliable than other methods for Na+ and K+ assessment, several potential biases still remain.(ABSTRACT TRUNCATED AT 250 WORDS)

Sleep related breathing patterns in patients with spinal muscular atrophy

A clinical and polygraphic study of nocturnal sleep was performed in 8 (4 males, 4 females; age range 10-37 years) patients with spinal muscular atrophy, whose baseline respiratory function assessment during wakefulness showed restrictive ventilatory syndrome but blood-gas tension within normal limits. No patient reported any significant sleep complaint suggestive of sleep-disordered breathing. However, in 4 patients HbSaO2 desaturations below 90% (HbSaO2 nadir 68%) were detected during nocturnal polysomnography. The HbSaO2 desaturations occurred during brief central apneas or hypopneas, mainly during REM sleep, the apnoea hypopnea index being within normal limits in all cases. The data suggest that nocturnal polysomnography can detect otherwise clinically silent hypoxemia in SMA patients without any predisposing factor to sleep-disordered breathing other than their illness and still showing normal blood-gas tensions during wakefulness. Further studies are needed to determine the long-term evolution and the prognostic significance of nocturnal hypoxemia in these patients.

Sleep disorders in neuromuscular diseases

This article reports the results of several studies on neuromuscular patients (9 Duchenne's muscular dystrophy, 10 myotonic muscular dystrophy, 8 mitochondrial myopathies, 6 spinal muscular atrophy). An evaluation of respiratory function during wakefulness, a sleep questionnaire and an overnight polysomnography were performed in all patients. Recurrent hypoxaemia of variable degree was observed during sleep. In most cases, night-time hypoxaemia appears not to be predictable during wakefulness. Nocturnal hypoxaemia occurs in relation to apnoeas or hypopnoeas, mainly of central type, especially when these breathing irregularities occur during rapid eye movement (REM) sleep. Moreover, polygraphic sleep-apnoea patterns, as defined by international criteria, seem to be an infrequent condition, except for those neuromuscular diseases, characterized by an involvement of the central nervous system.

Reference values of maximal respiratory mouth pressures: a population-based study

The aim of our study was to measure values of maximal inspiratory (MIP) and expiratory (MEP) mouth pressures in 625 (266 male, 359 female) clinically and functionally normal subjects drawn out of a sample representative of the general population. MEP (near TLC and FRC) was found to be significantly higher when compared with MIP (near RV and FRC), and pressures in male subjects were significantly higher than those in female subjects. MEP values at TLC and FRC were found to be closely related, as were values of MIP near RV and near FRC. Among the tested body-size variables, body surface area (BSA) for all parameters had the highest degree of correlation. Stepwise linear regression analysis was performed to define the equation of normality for all four parameters, employing BSA, sex, age, and relative interaction terms. R2 values, although the variables employed for the equations were highly significant, were relatively low and didn't fully explain the source of variability. The influence of age was smaller than the influence of BSA, although age did reduce the unexplained variance in MEP and MIP. These results confirm that the most useful employment of MIP and MEP is to monitor their changes in each patient, but they point out, however, the usefulness of reliable reference equations.

Pulmonary function in childhood connective tissue diseases

The term connective tissue diseases (CTD) defines a group of illnesses characterized by the presence of immune abnormalities and by widespread inflammation involving various organs and tissues including the lung. These diseases are not frequent in the paediatric age group. Very few data on pulmonary function are available in paediatric CTD. We investigated possible early lung function abnormalities and any likely relationship with clinical activity of the disease in a group of 81 paediatric CTD patients, without clinical or radiological evidence of pulmonary involvement. Measurement of lung volumes and diffusion lung capacity were performed. A sample of 65 subjects, defined as normal on the basis of history and clinical examination, and matched by age and height with the group of patients, was chosen as control group. CTD patients did not show significant deviations from the control distribution with respect to functional residual capacity (FRC) and maximal expiratory flow at 75% of the forced vital capacity (MEF75) values. On the contrary, both vital capacity (VC) and diffusing capacity of the lungs for carbon monoxide (DLCO) were quite impaired in most CTD during the active phase of the disease. Our results show a functional lung impairment in most children with clinically active CTD, even in absence of abnormalities on chest X-ray pictures.

Pulmonary function in childhood connective tissue diseases

The term connective tissue diseases (CTD) defines a group of illnesses characterized by the presence of immune abnormalities and by widespread inflammation involving various organs and tissues including the lung. These diseases are not frequent in the paediatric age group. Very few data on pulmonary function are available in paediatric CTD. We investigated possible early lung function abnormalities and any likely relationship with clinical activity of the disease in a group of 81 paediatric CTD patients, without clinical or radiological evidence of pulmonary involvement. Measurement of lung volumes and diffusion lung capacity were performed. A sample of 65 subjects, defined as normal on the basis of history and clinical examination, and matched by age and height with the group of patients, was chosen as control group. CTD patients did not show significant deviations from the control distribution with respect to functional residual capacity (FRC) and maximal expiratory flow at 75% of the forced vital capacity (MEF75) values. On the contrary, both vital capacity (VC) and diffusing capacity of the lungs for carbon monoxide (DLCO) were quite impaired in most CTD during the active phase of the disease. Our results show a functional lung impairment in most children with clinically active CTD, even in absence of abnormalities on chest X-ray pictures.

[Cigarette smoke and bronchial hypersensitivity]

Among intrinsic factors which may affect the onset of COPD, bronchial non specific hyperresponsiveness seems to play an important, even though, ill-defined role. Attention is drawn to 2 major points: 1) Cigarette smoking habit may increase airway responsiveness? 2) Any possible hyperresponsiveness induced by smoking may be relevant in the development of COPD? At present, only point 1 may be positively answered; point 2 will be clarified by means of perspective and long-term surveys, we have not achieved yet. Our cross-sectional study showed a significant influence of smoking on bronchial responsiveness in absolutely asymptomatic subjects and with airway caliber absolutely in the normal range. This kind of influence resulted to be dose-dependent. Furthermore a noxious role of smoking has been observed, the greater effect the higher amount of cigarettes/day smoked. Moreover this acute role of smoking has been remarked by the trend of bronchial responsiveness of past-smokers, the more similar to non smoker's, the more far was smoking cessation.