Élaboration et validation d’une grille prédictive de la vascularisation artérielle insuffisante à une plaie au membre inférieur

Prevalence of chronic lower extremity wounds is at 12,6 % among people aged 70 and over. These wounds are present in all health care settings – short-term or long-term hospital care, complex care such as intensive care and emergencies, and 80 % are in home-care settings or out-clinics –, making them an important public issue (Graham, Harrison, Shafey and Keast 2003, CIHI 2013). Now, a good blood supply in the wound bed is required for healing (Gottrup, 2004), whereas 20 % of these wounds have an inadequate one (Norgren et al., 2007). National and international guidelines prescribe to determine if the actual blood supply to the wound is sufficient to heal before deciding on the treatment plan (Norgren et al., 2007, Sibbald et al., 2011). A moist dressing is recommended when the arterial blood supply is deemed sufficient to heal, whereas a dry environment should be preferred when insufficient, the aim being to control the infectious process that may lead to an amputation (Hopf et al., 2006; Hopf et al., 2008, Woo, 2014). Devices known to measure blood supply are the Doppler for the arteriobrachial index, toe pressure, arterial waves of the pedious and posterior tibial arteries, and transcutaneous oximetry. These are not at hand in most health-care settings. Hence, the nurse's clinical decision to apply a moist or dry environment to these wounds is taken without any evaluation of the blood supply. The purpose of this research is to develop a grid in the form of questions, a checklist that the patient could answer or that the nurse could fill in relation to the wound on the lower limb, to predict whether the blood supply is insufficient. The main objectives are to develop such a predictive grid by identifying its potent predictors and to validate it with accepted criteria pertaining to the arterial vascularization in the lower limb. This research was framed by an exploratory sequential mixed method consisting of a ‘narrative synthesis’, expert consensus and pre-experimentation, steps of the development phase resulting in the identification of 52 potential predictors of blood supply in a lower limb wound. These predictors, conveyed by simple questions, were then confronted with five measured criteria (arteriobrachial index, manual and laser toe pressure, and tibial and pedal waves) on 108 patients for 295 wounds during a clinical experiment at the Chaudière-Appalaches CISSS complex wound clinic in Lévis (Québec, Canada). Transcutaneous oximetry could not be used for feasibility reasons. About 50 % of the wounds assessed were at the foot level, none at the level of the buttocks, two at the level of the thigh and eighteen at the levels of the knee and the popliteal area. To ensure the homogeneous predictive ability of the grid, data analysis focused on the 134 foot wounds. Moreover, preliminary results showed a lack of convergence among the five measured criteria used for assessing arterial blood supply to the lower limb wound, contrary to what was pronounced in the literature. This unforeseen fact postponed the process of creating and validating a final predictive grid, notwithstanding the methodological rigor used in the identification of predictors in the development phase. However, logistic regression modeling in a conditional upward accumulation mode (SPSS, v. 24) allowed the analysis of data for a potential predictive model for 134 wounds at the feet of 77 patients, based on five positive predictors and using the criterion relating to the monophasic wave of the posterior tibial artery. This provisional grid shows sensitivity and specificity values of 76,9 % and 91,5 % (Cohen kappa = 0,70, ½ kappa = 0,72, phi = 0.70, chi-square = 65,66), a prediction rate of true-positives = 85,1 %, a false-negatives rate = 86,2 %. These values all improved by taking into account a central uncertainty interval of the score, with sensitivity and specificity values of 84,4 % and 94,7% (Cohen kappa = 0,80, kappa ½ = 0,82, phi = 0,80, chi-square = 77,44). Considering that the afore-mentioned grid and its predictive ability are based on a single indirect criterion and the present unavailability of transcutaneous oximetry, further experimentation with this direct criterion measure should make possible a definitive validation of the grid before it can be applied clinically.

Keyphrases: validation, Clinical prediction, Blood supply, Arterial wound, Tool development, Mixed methods