Christophe Uldry

BACKGROUND: Inspiratory muscle strength is often better reflected by oesophageal pressure during a maximal sniff (sniff POES) than by maximal inspiratory pressure (PImax). Sniff POES can be estimated non-invasively by measuring the sniff nasal inspiratory pressure (SNIP). The aim was to establish maximal normal values for the SNIP and to compare them with PImax. METHODS: One hundred and sixty healthy subjects (80 men) aged 20-80 years were recruited. All subjects had a forced vital capacity (FVC) of > 80%, a forced expiratory volume in one second (FEV1)/FVC of > 85% predicted value, and a body mass index of 18-31 kg/m2. Because PImax is known to be reduced in the supine posture, the SNIP was measured in both the sitting and the supine positions. PImax sustained over one second was measured from functional residual capacity (FRC) in the sitting position with a standard flanged mouthpiece during four manoeuvres. SNIP was measured from FRC in the sitting and supine positions using a catheter through a plug occluding one nostril during 10 maximal sniffs through the contralateral nostril. For each test the largest pressure measured in cm H2O was taken into account. RESULTS: For both men and women maximal SNIP was negatively correlated with age, and was similar in the sitting and the supine positions. In the sitting position maximal SNIP was greater or equal to PImax in 107 of 160 subjects. The mean (SD) ratio SNIP/PImax was 1.08 (0.22) in men and 1.17 (0.29) in women. CONCLUSIONS: Normal values of maximal SNIP can be predicted from age and sex. Maximal SNIP is similar in the sitting and the supine position and is significantly higher than PImax in healthy subjects. The low level of agreement between maximal SNIP and PImax indicates that the two manoeuvres are not interchangeable but complementary.

BACKGROUND: Education programmes for adults with asthma vary widely. Such variability suggests a lack of consensus on what works and what does not. The objectives of this paper are to describe asthma education programmes and assess their variability. METHODS: A systematic review of reports published between 1979 and 1998 was conducted. Medline, the CINAHL database, the PsycINFO database, the Cochrane collaboration database, the Dissertation Index database, and cross referencing were used to identify educational interventions; 77 projects including 94 interventions that involved 7953 patients were analysed. A standard form was used to record characteristics of studies (design, setting, size, year, and country of publication), projects (theoretical framework, objectives), and education (methods, duration, intensity, educator, and content). RESULTS: Most reports did not specify the general (56%) and educational objectives (60%) of the intervention. Important training characteristics were often not available: duration of education (45%) and number of sessions (22%), who delivered education (15%), whether training was conducted in groups or was individualised (28%). When this information was available there were wide variations in training methods and content: training duration ranged from 0 (self-education) to 58 hours and the number of sessions from 0 to 36; training tools such as peak flow meters, diary cards or books were used in various proportions of interventions (19%, 27%, and 23%, respectively). The content of education also differed widely between programmes. CONCLUSIONS: Insufficient documentation of asthma education programmes for adults precludes their replication. This, together with excessive variability, reduces the possibility of identifying their most effective components. A more systematic description of asthma training programmes should be promoted.

Arterialized ear lobe blood samples have been described as adequate to gauge gas exchange in acute and chronically ill patients. It is a safe procedure, usually performed by medical technicians. We have conducted a prospective study to verify the validity of this method. One hundred and fifteen consecutive adult patients were studied. Blood samples were drawn simultaneously from arterialized earlobe and radial artery. Values of partial pressure of oxygen (PO2) and of carbon dioxide (PCO2) were measured by means of blood gas electrodes. The correlation coefficients between the two samples were 0.928 for PO2 and 0.957 for PCO2 values. In spite of a highly significant correlation, the limits of agreement between the two methods were wide for PO2. Earlobe values of PO2 were usually lower than arterial values, with larger differences in the range of normal arterial PO2. On the other hand, the error and the limits of agreement were smaller for PCO2. We conclude that, in adult patients, arterialized earlobe blood PO2 is not a reliable mirror of arterial PO2.

In subjects with normal lung mechanics, inspiratory muscle strength can be reliably and easily assessed by the sniff nasal inspiratory pressure (SNIP), which is the pressure measured in an occluded nostril during a maximal sniff performed through the contralateral nostril. The aim of this study was to assess the validity of the SNIP in patients with chronic obstructive pulmonary disease (COPD), where pressure transmission from alveoli to upper airways is likely to be dampened. Twenty eight patients with COPD were studied (mean forced expiratory volume in one second (FEV1) = 36% of predicted). The SNIP and the sniff oesophageal pressure (sniff Poes) were measured simultaneously during maximal sniffs, and were compared to the maximal inspiratory pressure obtained against an occlusion (MIP). All measurements were performed from functional residual capacity in the sitting position. The ratio SNIP/sniff Poes was 0.80, and did not correlate with the degree of airflow limitation. The ratio MIP/sniff Poes was 0.87, and the ratio SNIP/MIP was 0.97. Inspiratory muscle weakness, as defined by a low sniff Poes, was present in 17 of the 28 patients. A false diagnosis of weakness was made in eight patients when MIP was considered alone, in four when SNIP was considered alone, and in only three patients when MIP and SNIP were combined. We conclude that both the sniff nasal inspiratory pressure and the maximal inspiratory pressure moderately underestimate sniff oesophageal pressure in chronic obstructive pulmonary disease. Although suboptimal in this condition, the sniff nasal inspiratory pressure appears useful to complement the maximal inspiratory pressure for assessing inspiratory muscle strength in patients with chronic obstructive pulmonary disease.