[Chronic obstructive pulmonary disease and its links with cardiovascular risk factors]. / La bronchopneumopathie chronique obstructive et son lien avec les facteurs de risque cardiovasculaires.

Patients with chronic obstructive pulmonary disease (COPD) often also present with one or more cardiovascular risk factors, resulting not only in an increased mortality rate but also in a major impact on the health care system. Aside from common predisposing and environmental factors, the hypothesis of a chronic systemic inflammation linking COPD and cardiovascular co-morbidities is supported by an increasing body of evidence in recent literature. This could in turn pave the way for new developments, both diagnostic and therapeutic, in the future. In this context, the studies CoLaus and PneumoLaus aim to further investigate characteristics of the Lausanne general population, in particular those relating to cardiovascular and respiratory disease.

[Bronchial hyperresponsiveness and its importance for the clinician]. / L'hyperréactivité bronchique et son importance pour le clinician.

Asthma is a chronic inflammatory airway disease, characterised by bronchial hyperresponsiveness causing bronchoconstriction, and thereby provoking typical symptoms (dyspnoea, cough, wheezing). Bronchial hyperres- ponsiveness indicates a temporary airflow limitation when exposed to a bronchoconstricting stimulus. Its measurement by challenge tests can be a valuable tool for confirming or excluding asthma, as well as for evaluating the efficacy of treatment. However, the origin of bronchial hyperresponsiveness is multifactorial and the different challenge tests are not equivalent. Direct challenge tests, like methacholine, mainly reflect chronic airway remo- delling, whereas indirect tests, like mannitol, better reflect bronchial inflammation.

Diagnosis and management of chronic obstructive pulmonary disease: the Swiss guidelines. Official guidelines of the Swiss Respiratory Society.

The new Swiss Chronic Obstructive Pulmonary Disease (COPD) Guidelines are based on a previous version, which was published 10 years ago. The Swiss Respiratory Society felt the need to update the previous document due to new knowledge and novel therapeutic developments about this prevalent and important disease. The recommendations and statements are based on the available literature, on other national guidelines and, in particular, on the GOLD (Global Initiative for Chronic Obstructive Lung Disease) report. Our aim is to advise pulmonary physicians, general practitioners and other health care workers on the early detection and diagnosis, prevention, best symptomatic control, and avoidance of COPD as well as its complications and deterioration.

[Lung and pregnancy]. / Poumon et grossesse.

During pregnancy several adaptations develop in response to the enhanced maternal and fetal metabolic needs. This review summarizes the major cardiorespiratory modifications of pregnancy as well as their consequences in chronic respiratory diseases such as restrictive ventilatory defects (post-tuberculosis pneumonectomy, kyphoscoliosis, neuromuscular disorders), asthma, cystic fibrosis, and pulmonary hypertension. It is important to recognize early the cardiorespiratory situations for which pregnancy is contraindicated or associated with a high risk of respiratory complications. Clinical management by an expert and often pluridisciplinary team is recommended.

Volitional assessment of respiratory muscle strength.

Respiratory muscle weakness may induce dyspnoea, secretion retention and respiratory failure. Assessing respiratory muscle strength is mandatory in neuromuscular diseases and in case of unexplained dyspnoea. A step by step approach is recommended, starting with simple volitional tests. Using spirometry, respiratory muscle weakness may be suspected on the basis of an abnormal flow-volume loop or a fall of supine vital capacity. When normal, maximal inspiratory and expiratory pressures against a near complete occlusion exclude significant muscle weakness, but low values are more difficult to interpret. Sniff nasal inspiratory pressure is a useful alternative because it is easy and it eliminates the problem of air leaks around the mouthpiece in patients with neuromuscular disorders. The strength available for coughing is easily assessed by measuring peak cough flow. In most cases, these simple non invasive tests are sufficient to confirm or to eliminate significant respiratory muscle weakness and help the timely introduction of ventilatory support or assisted cough techniques. In a minority of patients, a more complete evaluation is necessary using non volitional tests like cervical magnetic stimulation of phrenic nerves.

[Clinical value of bronchoalveolar lavage]. / Uitlité clinique du lavage bronchoalvéolaire.

Bronchoalveolar lavage (BAL) is a minimally invasive procedure used to characterize the status of the alveolar space. Standardization of the procedure and the analysis of samples taken is essential for their proper interpretation. In nonresolving or ventilator-associated pneumonia, BAL contributes to the detection of resistant pathogens and noninfectious etiologies. In immunocompromised hosts with radiological infiltrates, BAL should be performed early during work-up since outcome is significantly modified in this population group. In cases of interstitial lung disease, BAL can exclude infectious or neoplastic causes. Associated with a clinical and radiological evaluation, it provides valuables additional diagnostic information.

Maximal sniff mouth pressure compared with maximal inspiratory pressure in acute respiratory failure.

Inspiratory muscle strength most often is better reflected by sniff Pes than PImax against occlusion. Furthermore, sniff Pes can be estimated noninvasively by the measurement of sniff Pmo in normal subjects and in patients with respiratory muscle weakness. The aim of this study was to compare sniff Pmo and P.PImax to assess inspiratory muscle strength in patients with acute respiratory failure. The highest pressure was produced by P.PImax in 61 percent of measurements, and by sniff Pmo in 39 percent. Above 35 cm H2O P.PImax yielded the highest pressure in 55 percent of cases and the ratio sniff Pmo/P.PImax was 1.20 +/- 0.54. Below 35 cm H2O, P.PImax yielded the highest pressure in 75 percent of cases and the ratio sniff Pmo/P.PImax was 0.76 +/- 0.35 (p less than 0.02). Thus, measurements of sniff Pmo and P.PImax complement one another for assessing inspiratory muscle strength. However, sniff Pmo underestimates inspiratory muscle strength in patients with severe inspiratory muscle weakness.

Acute pulmonary edema caused by venous air embolism after removal of a subclavian catheter.

A 17-year-old boy, who had received chemotherapy for a relapse of acute myelogenous leukemia, manifested a brief loss of consciousness and acute pulmonary edema immediately after the removal of a triple-lumen subclavian catheter. This complication was attributed to a venous air embolism.

Probability of malignancy in pleural fluid eosinophilia.

Pleural fluid eosinophilia is rare and is commonly considered as an indicator of good prognosis. In a series of 224 patients, pleural eosinophilia was present in four of 84 malignant cases; however, the incidence of malignancy in the presence of pleural eosinophilia was 0.40, being explained by a relatively high prevalence of malignancies in the population studied. Although pleural eosinophilia is rare in malignant effusions, it cannot be considered as indicating a good prognosis without taking into consideration the local prevalence of malignancies.

Costal and crural diaphragm in early inspiration: free breathing and occlusion.

Changes in length of costal and crural segments of the canine diaphragm were measured by sonomicrometry within the first 100-300 ms of inspiration during CO2 rebreathing in anesthetized animals. Both segments showed small but significant decreases in end-expiratory length during progressive hypercapnia. Although both costal and crural segments showed electromyographic activity within the first 100 ms of inspiration, in early inspiration crural shortening predominated with minimal costal shortening. Neither segment contracted isometrically early in inspiration in the presence of airway occlusion. The amount of crural shortening during airway occlusion exceeded costal shortening; both segments showed increased shortening with prolonged occlusion and increasing CO2. Costal and crural shortening at 100 ms was not different for unoccluded and occluded states. These observations suggest that neural control patterns evoke discrete and unequal contributions from the diaphragmatic segments at the beginning of an inspiration; the crural segment may be predominately recruited in early inspiration. Despite traditional assumptions about occlusion pressure measurement (P0.1), diaphragm segments do not contract isometrically during early inspiratory effort against an occluded airway.

Velocity of shortening of inspiratory muscles and inspiratory flow.

Respiratory muscle length was measured with sonomicrometry to determine the relation between inspiratory flow and velocity of shortening of the external intercostal and diaphragm. Electromyographic (EMG) activity and tidal shortening of the costal and crural segments of the diaphragm and of the external intercostal were recorded during hyperoxic CO2 rebreathing in 12 anesthetized dogs. We observed a linear increase of EMG activity and peak tidal shortening of costal and crural diaphragm with alveolar CO2 partial pressure. For the external intercostal, no consistent pattern was found either in EMG activity or in tidal shortening. Mean inspiratory flow was linearly related to mean velocity of shortening of costal and crural diaphragm, with no difference between the two segments. Considerable shortening occurred in costal and crural diaphragm during inspiratory efforts against occlusion. We conclude that the relation between mean inspiratory flow and mean velocity of shortening of costal and crural diaphragm is linear and can be altered by an inspiratory load. There does not appear to be a relationship between inspiratory flow and velocity of shortening of external intercostals.

Effect of thoracoabdominal breathing patterns on inspiratory effort sensation.

The respiratory sensations evoked by added inspiratory loads are currently thought to be largely mediated by the activity of the inspiratory muscles. Because of the differences in proprioceptors and in afferent and efferent innervations among the inspiratory muscles, we hypothesized that the sensation evoked by a given load would be different when the motor command is directed mainly to rib cage muscles or mainly to the diaphragm. To test this hypothesis, we studied six normal subjects breathing against several inspiratory resistances while emphasizing the use of rib cage muscles, or the diaphragm, or a combination of both. At the end of 10 loaded breaths the subjects rated the perceived magnitude of inspiratory effort on a Borg scale. A linear and unique relationship (r = 0.96 +/- 0.02; P less than 0.001) was found between the sensation and esophageal pressure (Pes) in the three thoracoabdominal breathing patterns. We conclude that the level of Pes, whether generated mainly by the rib cage muscles or the diaphragm, is the main variable related to the sensation of inspiratory effort under external inspiratory loads.

Costal and crural diaphragm function during CO2 rebreathing in awake dogs.

If costal and crural diaphragm segments can perform as separate muscles, then CO2-stimulated ventilation may elicit differential segmental function. We studied diaphragm segmental length, shortening, and electromyogram (EMG) activity in 10 awake dogs chronically implanted with sonomicrometer transducers and EMG electrodes. During CO2 rebreathing, segmental shortening and EMG activity per whole tidal breath progressively increased, but segmental responses could not be differentiated at any level of CO2. With increasing CO2, resting end-expiratory length of both diaphragm segments increased. During the complete intrabreath inspiratory-expiratory cycle, costal and crural diaphragm revealed distinctive segmental function. At rest, crural shortening exceeded costal shortening in earliest inspiration, costal and especially crural shortening persisted into early expiration, and EMG activity of the crural segment was greater than that of the costal segment in earliest inspiration and showed more end-inspiratory/early expiratory [post-inspiratory inspiratory activity (PIIA)] activity. During CO2-stimulated breathing, neither segment shortened during the inspiratory flow of earliest inspiration. During CO2 rebreathing, shortening of the crural segment exceeded that of the costal segment during early inspiration and outlasted costal shortening during expiration; for both segments, shortening persisted after termination of inspiratory airflow. With increased CO2, EMG activity of the crural segment preceded that of the costal segment in earliest inspiration and was dominant into expiration, whereas costal EMG activity terminated abruptly with inspiratory flow. Thus, costal EMG PIIA was not evident during hypercapnia, whereas crural EMG PIIA was significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Activity of costal and crural diaphragm during progressive hypoxia or hypercapnia.

Because costal and crural diaphragm segments have different functional characteristics, ventilatory stimulation with hypoxia or hypercapnia may elicit differential segmental function. We report measurements of diaphragm segmental length, shortening, and electromyogram (EMG) activity from 11 canines that were chronically implanted with sonomicrometry transducers and EMG electrodes and then studied a mean of 18 days postimplantation while awake and breathing spontaneously during CO2 rebreathing and progressive isocapnic hypoxia. Ventilatory responses to hypercapnia and progressive hypoxia were moderate at 1.13 +/- 0.31 (SD) 1. min-1. mm-1 arterial Pco2 and -0.98 +/- 0.51 l. min-1.%arterial O2 saturation-1. When tidal values for breathing pattern and segmental function were compared at matching tidal volumes that correspond to mean CO2 of 49.4 arterial Pco2 and 77% arterial O2 saturation, there was no significant difference in resting length, tidal shortening, or tidal EMG of costal or crural segments. Intrabreath profiles of flow, shortening, and EMG activity at matched tidal volumes showed that 1) inspiratory flow during hypoxia was significantly greater during early inspiration, 2) crural EMG activity preceded costal EMG activity in early inspiration during both hypercapnia and hypoxia, 3) both segments showed increased postinspiratory inspiratory activity with stimulated ventilation, and 4) postinspiratory shortening and EMG were greatest for the crural segment during hypoxia. These results suggest that costal and crural diaphragm segments exhibit differential function during chemical stimulation, especially during postinspiration.

Recovery of diaphragm function after laparotomy and chronic sonomicrometer implantation.

If sonomicrometry transducers could be implanted permanently into the diaphragm, direct measurements of costal and crural length and shortening could be made during recovery from the laparotomy and then indefinitely in an awake, non-anesthetized mammal. We report results from six canines in which we successfully implanted transducers onto the left hemidiaphragm through a midline laparotomy and measured segmental shortening and ventilation at intervals through 22 days of postoperative recovery. After laparotomy, breathing pattern, including tidal volume, respiratory rate and mean inspiratory flow, stabilized by the 4th postoperative day (POD). Tidal shortening of costal and crural segments increased from 1.82 and 1.45% of end-expiratory length (%LFRC) on the 2nd POD to 5.32 and 8.56% LFRC, respectively, after a mean of 22 POD. Segmental shortening did not stabilize until 10 POD, and the recovery process displayed a sequence of segmental motions: lengthening, biphasic inspiratory lengthening-shortening, and increasing simple shortening. Three weeks after implantation, costal and crural segments were stable and shortening 5.32 and 8.56% LFRC, respectively, and capable of shortening 49% LFRC with maximal phrenic stimulation. In a pair of recovered animals, the initial postoperative dysfunction did not recur after a subsequent, simple laparotomy. At postmortem examination, the chronically implanted sonomicrometer transducers were found to have evoked only a thin fibrotic capsule within the diaphragm.

Diaphragm length adjustments with body position changes in the awake dog.

Sonomicrometry was used to measure end-expiratory length and tidal shortening of the costal and crural diaphragm in awake chronically instrumented dogs in the right lateral decubitus, standing, and sitting postures. End-expiratory length did not change significantly in standing but fell by 11.5% for the costal and by 14.4% for the crural segment in sitting, when compared with decubitus position. Tidal shortening of both segments did not change significantly in the three postures. From decubitus to sitting, diaphragmatic electromyogram (EMG) activity increased only in some dogs, not significantly for the group. The inspiratory swing of abdominal pressure was always positive in decubitus and negative in standing and sitting. In the latter two postures, abdominal pressure increased gradually during expiration and fell in inspiration, suggesting a phasic expiratory contraction of abdominal muscles. We conclude that diaphragmatic tidal shortening is maintained in the different postures assumed by the awake dog during resting breathing. It seems that the main compensatory mechanism for changes in diaphragmatic operational length is a phasic expiratory contraction of the abdominal muscles rather than an increase in diaphragmatic EMG activity.

Dissociation between diaphragmatic and rib cage muscle fatigue.

To assess rib cage muscle fatigue and its relationship to diaphragmatic fatigue, we recorded the electromyogram (EMG) of the parasternal intercostals (PS), sternocleidomastoid (SM), and platysma with fine wire electrodes and the EMG of the diaphragm (DI) with an esophageal electrode. Six normal subjects were studied during inspiratory resistive breathing. Two different breathing patterns were imposed: mainly diaphragmatic or mainly rib cage breathing. The development of fatigue was assessed by analysis of the high-to-low (H/L) ratio of the EMG. To determine the appropriate frequency bands for the PS and SM, we established their EMG power spectrum by Fourier analysis. The mean and SD for the centroid frequency was 312 +/- 16 Hz for PS and 244 +/- 48 Hz for SM. When breathing with the diaphragmatic patterns, all subjects showed a fall in H/L of the DI and none had a fall in H/L of the PS or SM. During rib cage emphasis, four out of five subjects showed a fall in H/L of the PS and five out of six showed a fall in H/L of the SM. Four subjects showed no fall in H/L of the DI; the other two subjects were unable to inhibit diaphragm activity to a substantial degree and did show a fall in H/L of the DI. Activity of the platysma was minimal or absent during diaphragmatic emphasis but was usually strong during rib cage breathing. We conclude that fatigue of either the diaphragm or the parasternal and sternocleidomastoid can occur independently according to the recruitment pattern of inspiratory muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnosis of diaphragmatic dysfunction.

Diaphragmatic dysfunction is an important entity, as it can cause severe dyspnea, ventilation-perfusion abnormalities, and ventilatory failure. The most frequent and important dysfunctions are diaphragmatic weakness, incoordination between the diaphragm and other respiratory muscles, fatigue, and paralysis. Methods for the diagnosis of dysfunction are reviewed and specific dysfunctions are briefly discussed with methods for their evaluation.

Non-invasive home ventilation in patients over 75 years of age: tolerance, compliance, and impact on quality of life.

The adequacy of domiciliary non-invasive positive pressure ventilation (NIHV) for hypercapnic restrictive pulmonary disease in patients aged 75 years or above has been questioned, because of a lower life expectancy, a higher risk of neuropsychological impairment and a lower potential for adapting to NIHV. This study aims to illustrate that the use of NIHV is possible and efficient in this age group. In our referral area, all patients under NIHV have been included in a database since 1994; at the end of 1996, all patients in whom NIHV had been initiated at age 75 years or above were studied. We performed a cross-sectional study of six patients (two men, four women, age: 79 +/- 3 years at time of study) who had been under NIHV for 31 +/- 17 months. Patients underwent pulmonary function testing, assessment of respiratory muscle strength, physical disability and neuropsychological performance, tolerance and compliance to NIHV, and health-related quality of life (SF-36, St. George Respiratory Questionnaire: SGRQ). Hospitalization rates were recorded for the year prior and the 2 yr following initiation of NIHV. By the time of the study, all patients showed improved arterial blood gases when compared to values before NIHV (PaCO2: 46 +/- 9 vs 66 +/- 10 mmHg, P = 0.04). Patients adapted well to NIHV, with minor side-effects and an average daily use of ventilator of 10.5 +/- 2 h. None of the patients showed signs of emotional disturbance. SF-36 scores for mental health, subjective well-being and vitality, or social functioning, did not differ from that of age-matched controls. SGRQ scores were similar to those published for younger patients under NIHV. Use of health care facilities was similar to that of younger patients under NIHV; hospitalization rates decreased significantly after initiating NIHV (40 +/- 31 days for year before NIHV, vs 13 +/- 14 days and 0.8 +/- 0.4 days for the 2 yr following NIHV, P = 0.02). Age above 75 years should not be considered per se as a contraindication to NIHV in patients with well-accepted indications for this treatment. Our results suggest that in this age group, the cost/benefit ratio of NIHV may be favourable.

Does the 'oxygen cost diagram' reflect changes in six minute walking distance in follow up studies?

The oxygen cost diagram (OCD) is a simple scale for quantifying a patient's evaluation of his tolerance to exercise frequently used in clinical trials; it has been shown to be well correlated with objective measures of capacity of ambulation such as the 6 min walk test (6' W). This study aimed to determine whether the OCD accurately depicts changes in capacity of ambulation either quantitatively or qualitatively. OCD ratings were analysed at baseline and after a 1 yr follow-up, in patients treated by non-invasive home mechanical ventilation, as well as objective measurements of pulmonary function [forced expiratory volume in 1 sec (FEV1), forced vital capacity (FVC), arterial blood gases], physical autonomy (6' W), resting dyspnoea (Borg scale) and scores for anxiety or depressive disorders (HAD). Forty-five patients (24 male, 21 female, aged 62 +/- 16 years, mean FEV1: 38 +/- 17% of predicted) were evaluated at baseline. OCD ratings were significantly correlated with 6 min walking distance (P < 0.0001)--although with a large variability around the regression line--but not with resting dyspnoea (Borg). Patients were re-evaluated after 352 +/- 90 days. Changes in OCD ratings were not significantly correlated with changes in FFV1 FVC, PaO2, PaCO2, 6' W, HAD scores or resting dyspnoea; furthermore--albeit for Borg scores--changes in OCD did not reflect the trend of changes in these parameters. These results show that although OCD ratings are well correlated with results of a 6' W test, they cannot be used to extrapolate individual performances, because of a large variability around the regression line, furthermore, changes in the OCD over 1 yr did not depict objective changes in 6' W test results, either quantitatively or qualitatively. The use of the OCD in clinical trials should be limited to the description of the patient's perception of exercise tolerance, as a component of health-related quality of life, with the awareness of possible discrepancies between changes in objective performances and changes in OCD ratings.