**5. Proposal of health services**

A health service can be understood as a computing service that inputs one or more vital signs from one or more persons. The output of a health service refers to insights regarding a particular person or a collection of persons (common health conditions of citizens of a city district or community). Thus, the heart rate sensors can detect and predict whether this rate is increasing or decreasing and whether it is falling to the point of causing heart failure [18, 19]. Under normal conditions, a person's heart rate varies between 60 and 100 bpm. Critical situations are considered when the heart rate is less than 40 bpm or greater than 150. In this case, the sensors can be used on patients in the hospital emergency room and patients with chronic cardiorespiratory diseases who want to monitor at home, using historical data from a single user over time. It is possible to trigger an alarm warning that the heart rate is decreasing so that doctors can verify the cause and possibly prevent a cardiac arrest. Not only that but an alert can be sent to the nearest emergency station, automatically triggering an ambulance to where the person is. Moreover, the same system can perform an alert network in the hospital environment, whether during observation, hospitalization, or in the ICU, generating a specific signal to the nearest infirmary, alerting that the patient is in cardiorespiratory arrest.

Besides, the sepsis prediction could be made too. It is characterized by a dysregulation of the inflammatory and their stems in response to a microbial invasion that produces body injury. During sepsis, tachypnea, tachycardia, and the high temperature usually occur. According to [20], two or more of these signs indicate sepsis temperature >38°C, heart rate >90/min, and respiratory rate >20/min. From the detection by the sensors, it can be predicted whether the patient is experiencing a worsening of his condition and getting septic. So, historical data from a single user to monitor over time can be used. This way, the hospital staff can be notified, and the patient should receive proper care.

In addition, from the measurement of individuals' vital signs, it is possible to follow the progression or regression of the chronicity of disease through the analysis of baseline reference values of the analyzed vital signs [21]. In chronic diseases such as cardiac diseases, chronic obstructive pulmonary diseases (asthma, emphysema, bronchitis), and renal diseases, all vital signs are usually monitored, as any of them can worsen and lead to decompensation of the disease. Data from the elderly would be monitored in a home for the elderly with chronic diseases or homes of an older population. This data could be saved for them or their caregivers to follow up. In this case, historical data from a single elderly user is used to monitor over time, and the underlying disease of the elderly can be followed over time.

Monitoring oxygen saturation in patients with Chronic Obstructive Pulmonary Disease (COPD) to help decrease respiratory function can be done. Patients with COPD are more likely to experience a drop in peripheral blood oxygen saturation (hypoxia) because oxygen entry into the lungs is impaired [22]. This way, neighborhoods, and cities could be monitored to predict a worsening clinical picture. Analysis of this vital sign can be sent to the hospital caring for that patient. It may indicate the need for mechanical ventilation or oxygen for the patient or additional treatment.

By measuring oxygen saturation, hypoxemia can be identified. It is characterized by a decrease in partial pressure of oxygen in the blood, leading to impaired blood perfusion and cyanosis in more critical cases [23, 24]. It can be measured through arterial oxygen saturation, characterized by the percentage of hemoglobin saturated with oxygen. Oxygen levels below 90% describe severe hypoxemia in peripheral blood [25]. Some causes of hypoxemia are asthma, chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, pulmonary embolism, and COVID-19. Thus, measuring the arterial oxygen saturation becomes helpful in the hospital environment because once the oxygen saturation level of a patient who has entered the hospital or even who is already hospitalized is detected as low, it can be predicted whether the patient should be in an alert or critical state, and should or should not be intubated due to the need for interventions for mechanical ventilation.

Preeclampsia is a gestational disorder characterized by increased blood pressure and proteinuria during the third trimester of pregnancy. It is one of the leading causes of maternal and infant mortality. The diagnosis is based on the presence of hypertension, with measurements performed at two different times, with systolic blood pressure >140 mmHg and diastolic blood pressure at >90 mmHg, in previously normotensive patients and proteinuria at >300 mg. Thus, the measurement of blood pressure in gestational patients through a device can help diagnose the pathology in pregnant women, with measurement both in the residential and in the hospital or clinic. The device can send an alert to the hospital or pregnant patient, warning that the blood pressure is increasing. With this, the doctor who takes care of the patient can provide adequate treatment to avoid eventual problems.
