Differences in PO 2 and PCO 2 between arterial and arterialized earlobe samples. A. Sauty, C. Uldry, L-F. Debétaz, P. Leuenberger, J-W. Fitting. ©ERS Journals Ltd 1996. ABSTRACT: 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 (PO 2 ) and of carbon dioxide (PCO 2 ) were measured by means of blood gas electrodes.The correlation coefficients between the two samples were 0.928 for PO 2 and 0.957 for PCO 2 values. In spite of a highly significant correlation, the limits of agreement between the two methods were wide for PO 2 . Earlobe values of PO 2 were usually lower than arterial values, with larger differences in the range of normal arterial PO 2 . On the other hand, the error and the limits of agreement were smaller for PCO 2 .We conclude that, in adult patients, arterialized earlobe blood PO 2 is not a reliable mirror of arterial PO 2 . Eur Respir J., 1996, 9: 186-189 Blood gas values can be measured using arterialized earlobe blood samples, instead of arterial samples, in order to gauge pulmonary gas exchange in acute or chronically ill patients. This method, described many years ago [1], is a simple and safe procedure which can be performed by medical technicians. Comparing values for partial pressure of oxygen (PO 2 ) and of carbon dioxide (PCO 2 ) from arterialized earlobe blood samples with arterial blood samples, several authors have concluded that the earlobe site was suitable for routine clinical purposes [1][2][3][4][5][6][7][8][9]. This idea was again advocated by two recent studies. PITKIN et al. [10] compared PO 2 , PCO 2 , and pH values from 40 blood samples simultaneously drawn from the radial artery and hyperaemic earlobe. Using the method of BLAND and ALTMAN [11] for the assessment of agreement, these authors also concluded that arterialized earlobe blood gas values were accurate enough to be used in clinical application. Finally, DAR et al. [12] reported that earlobe sampling was significantly less painful than arterial sampling in 55 patients, whereas blood gas values were not different with the two techniques.For several years, the arterialized earlobe technique has been the standard practice for measuring arterial blood gases in our pulmonary function laboratory. However, in some instances, we have noticed a marked discrepancy between arterial and relatively lower arterialized earlobe values of PO 2 . We, therefore, conducted a prospective study to compare arterial and arterialized earlobe blood samples in 115 consecutive adult patients. Material and methodsOur study group included 115 consecutive adult patients investigated in our pulmonary function laboratory for various conditions. No...

The measurement of mouth pressure during a maximal inspiratory effort against a quasi occlusion (maximal inspiratory pressure (MIP)) is classically established as the standard for assessment of inspiratory muscle strength [1]. However, in addition to being closely dependent on subject collaboration, this manoeuvre is demanding and unpleasant. Thus, whilst high values of MIP exclude inspiratory muscle weakness, lower values are frequently difficult to interpret, reflecting either a true muscle weakness or a lack of motivation and co-ordination [2].A recent alternative noninvasive method consists of performing a short maximal sniff through one nostril while measuring nasal pressure through a plug occluding the contralateral nostril (sniff nasal inspiratory pressure (SNIP)) [3][4][5]. This natural manoeuvre is easier and less unpleasant than the static effort of MIP, but nevertheless depends on volitional muscle contraction. The need for a nonvolitional test, especially in situations where collaboration is totally lacking, has led to the development of phrenic nerve stimulation. Because it is better tolerated and easier to apply, cervical magnetic stimulation has now largely replaced electrical stimulation [6,7]. The measurement of twitch mouth pressure (Pmo,tw) during magnetic stimulation was recently reported as a reliable assessment of diaphragm strength [8].Thus, several noninvasive techniques are now available for assessing inspiratory muscle strength, based on volitional and nonvolitional manoeuvres. In order to use these new methods in clinical settings, it is necessary to characterize them in comparison with the established reference method. The aim of this study was to determine the reproducibility of SNIP and Pmo,tw during cervical magnetic stimulation and to compare them to classical MIP in a group of normal subjects. Materials and methods Study subjectsTen healthy volunteers (nine males, one female) were studied. Their characteristics were (mean±SD): age 28±7 Ten healthy subjects were studied at functional residual capacity in semirecumbent position. Cervical magnetic phrenic nerve stimulation was performed during gentle expiration against an occlusion incorporating a small leak. Constancy of stimulation was controlled by recording diaphragmatic electromyogram. Within and betweensession reproducibility of pressure were studied for Pmo,tw, SNIP, and MIP. The subjects were studied during a session of 10 manoeuvres repeated after 1 day and 1 month.The mean values were 16 cmH 2 O for Pmo,tw, 118 cmH 2 O for SNIP, and 115 cmH 2 O for MIP. For the three tests, the within subject variation was small in relation to between-subject variation, with the intraclass correlation coefficient ranging 0. We conclude that the within session reproducibility of the new tests twitch mouth pressure and sniff nasal inspiratory pressure is sufficient to be clinically useful. For sniff nasal inspiratory pressure, the between session reproducibility established after 1 day was maintained after 1 month. For twitch mouth pressure,...

Severe respiratory insufficiency causes patients to be intolerant of physical effort and to be frequently limited in their daily activity and results in an imbalance between food intake and nutritional needs. Undernutrition and overnutrition can both affect the quality of life and survival of patients with pulmonary disease. Protein-energy malnutrition can lead to quantitative, qualitative and functional alterations of muscle [1,2] and this affects muscle function, including respiratory muscle in patients with already limited respiratory reserves. Optimal adaptation of nutrition support through the assessment of fat-free mass (FFM) and fat mass (FM) in patients with chronic respiratory insufficiency can avoid or minimize muscle wasting or obesity. For these reasons, the nutritional assessment should include body composition measurements which are based on objective rather than subjective criteria of nutritional evaluation. Body composition can be measured by a number of techniques, including hydrodensitometry, isotope dilution, and whole-body counting of potassium-40 [3]. However, these methods are not easily applicable in ill subjects.More recent methods for the determination of the FFM are dual-energy X-ray absorptiometry (DXA) and bioelectrical impedance analysis (BIA). DXA has been validated against independent methods, including a gamma neutronactivation model [4,5], total body potassium and hydrodensitometry [6] and is becoming one of the reference methods for body composition analysis, but requires sophisticated technology. BIA is a method of measuring body composition which is easy, noninvasive and inexpensive [7]. BIA measurements have been validated in healthy adults [8][9][10]. The relationship between body impedance and body composition is dependent on age and sex [11,12]. Over 20 different formulae permit the calculation of the FFM and FM based on BIA measurements and have generally been validated in healthy, young adults. SCHOLS et al. [13] proposed a BIA formula validated against deuterium dilution for patients with chronic obstructive pulmonary disease (COPD) (n=24), which included weight and height 2 /resistance (ht 2 /R) as independent variables. Recently, PICHARD et al. [14] were unable to obtain clinically relevant correlations between FFM calculated by 12 BIA formulae [8,9,11,[15][16][17][18][19][20][21], including SCHOLS et al. [13], and DXA-determined FFM, and suggested that a specific formula should be developed for patients with chronic severe respiratory insufficiency. These results suggest that the bioelectrical impedance analysis formula specific to patients with severe respiratory insufficiency give a better correlation and smaller mean differences than 12 different bioelectrical impedance analysis formulae described in the medical literature. A prediction equation, validated against dual-energy X-ray absorptiometry and based on subjects with similar clinical characteristics, is more applicable to the patients with respiratory insufficiency than a formula developed for healthy subje...

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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.