## 2 Methods  
The authors studied 25 healthcare centers belonging to three different healthcare districts in Spain, built between 1985 and 2005, from a quantitative point of view. The selection of these healthcare centers was made to be representative. They represent the same number of beds and are in the same region, so the activity generated by health care and the climate of the area is similar in the centers. When analyzing the data, statistical analysis techniques based on simple and multiple correlations were used to determine the degree of interconnection between the variables. In all cases, the standard error of the estimate and its correlation coefficient were calculated. A healthcare center is a building designed to carry out Primary Health Care Assistance actions, which has adequate staff and equipment to meet those needs. It is designed according to the World Health Organization welfare protocols to optimize the user's first contact with the Health System. It has a continuous operation 24-365, therefore the maintenance of them is critical. As the healthcare buildings studied here are isolated centers located in large urban centers, specialists should carry out routine patrol maintenance every certain period of time. The frequency with which each patrol maintenance is carried out was set in three possible alternatives: 7, 15 and 21 days. A Markov chain is split into different states. These states correspond to the states of the system analyzed [30]. For this research, a nine state Markov chain has been developed, representing the degradation of healthcare facilities. All nine states of the Markov chain are designated as the degradation scale. The probability of system degradation corresponds to the state transition probability, which is obtained based on the statistical study of maintenance incidents that occur in health centers. These probabilities constitute the transition matrix of the Markov chain, i.e., the coefficients of that matrix. These coefficients were determined through the statistical analysis of the information available in the engineering and maintenance services of the healthcare centers analyzed. This analysis is based on minimizing the error that occurs between the observations during maintenance inspections and the predictions of the Markov model [31]. Firstly, the transition matrix is obtained based on the observed data [32]. After that, the transition matrix is determined, which reduces the discrepancy between the matrix obtained from the healthcare center incidents and the matrix determined from applying the Markov model. The Solver tool of Microsoft Excel is used to minimize the error. Finally, the validation of this analysis is done through the Pearson X\({}^{2}\) test [33]. The incidents used in this paper are defined as nonurgent breakdowns originating in a healthcare center. These incidents may include, window insulation failure, door damage, lighting failure, humidity, damage to stretchers or noncritical equipment, among others. The percentage degradation scale as a function of the number of incidents happening in the facilities of a healthcare center is shown in Table 1, is used as a reference to illustrate the current state of the system as a function of the number of monthly incidents and the percentage of degradation. The degradation scale has a range from 1 to 9, where 1 and 9 corresponds to an excellent and unacceptable condition. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Degree** & **Status Description** & **No of Monthly Incidents** & **Degradation** \\ \hline
1 & Excellent & \textless{}5 & 0 to 10\% \\
2 & Very good & 6-10 & 11 to 20\% \\
3 & Good & 11–15 & 21 to 30\% \\
4 & Acceptable & 16–20 & 31 to 40\% \\
5 & Tolerable & 21–25 & 41 to 50\% \\
6 & Low & 26–30 & 51 to 60\% \\
7 & Very low & 31–35 & 61 to 70\% \\
8 & Poor & 36–40 & 71 to 80\% \\
9 & Unacceptable & \textgreater{}40 & \textgreater{}80\% \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Degradation scale of the condition according to the number of incidents.