Clinical study of Dysfunctional Ventilatory Weaning Response in critically ill patients*

Objective: to clinically validate the nursing diagnosis of Dysfunctional Ventilatory Weaning Response in adult patients admitted to Intensive Care Units. Method: a concurrent cohort performed with 93 patients admitted to Intensive Care Units. The incidence and incidence density of the diagnosis were estimated, its related factors were identified based on bivariate analysis and clinical indicators for determining its occurrence, according to the global and temporal presentation. Results: the overall incidence of the diagnosis was 44.09% and the incidence density was 14.49 occurrences for every 100 extubations/day. The factors related to the diagnosis were the following: age, clinical severity, fluid balance, oliguria, hemodialysis, edema in upper/lower limbs, anasarca, number of antibiotics, hypothermia, hyperthermia, amount of secretion, muscle retraction, anxiety score, heart rate, use of vasopressors and non-invasive ventilation after extubation. The clinical indicators most frequently identified for determining the diagnosis were the following: tachypnea, drop of saturation and tachycardia. Temporal progression in the severity of these manifestations was found. Conclusion: the Dysfunctional Ventilatory Weaning Response is a common finding in critically ill patients. Some components of the diagnosis of the NANDA-International (2018) version could be clinically validated. It is noteworthy that there are variables not yet described in the taxonomy, demonstrating the need to review this nursing diagnosis.


Introduction
Mechanical Ventilation (MV) is a therapeutic support often used in Intensive Care Units (ICU).
Multi-center cross-sectional studies demonstrate that up to 46% of the patients admitted to these units require MV at some point during their hospitalization (1)(2)(3) . However, despite being a primary intervention for the patient with acute or chronicacute respiratory failure, reducing the work of the respiratory muscles, and reversing or preventing muscle fatigue (2)(3) , mechanical ventilatory support is capable of inducing several complications, such as Ventilator Associated Pneumonia (VAP) (4) , diaphragmatic dysfunction induced by MV (5)(6) , and critical illness polyneuropathy (7) , increasing the morbidity and mortality of a critically ill patient (8)(9)(10) In this context, it is essential to reduce the time in which the patient is under invasive artificial ventilation, restoring spontaneous ventilation as soon as possible, a process called ventilatory weaning (9,(11)(12) .
The performance of the nurse in this context aims to minimize the adverse events caused by MV and potential risks to which the patient on artificial ventilation is exposed, such as self-extubation, the occurrence of VAP and other nosocomial infections, in addition to extubation failure (13) . This ND refers to the activity/rest domain, being defined as "Inability to adjust to decreased levels of mechanical ventilatory support, which interrupts and prolongs the weaning process" (14) . However, despite being accepted by NANDA-I about 25 years ago, this ND is not supported by strong scientific evidence and its defining characteristics and related factors are not yet determined in terms of relevance.
Besides, it is considered that the factors related to the diagnosis, in addition to being limited, are outdated in relation to the current scientific production on the human problem/response. It should be noted that validation or review studies of its components have not been identified. Finally, it is worth mentioning that this is one of the ND for which NANDA-I recommends that studies be conducted to produce scientific evidence of the diagnosis itself and its components (14) .

Method
This is a multi-center concurrent cohort study with consecutive follow-up of hospitalized patients in four adult ICUs of two large teaching hospitals in a Brazilian capital. In addition to estimating the incidence and incidence density of DVWR in the sample, the clinical indicators for determining this ND (defining characteristics) and factors related to its occurrence were also observed.  It is worth mentioning that, for this study, failure to wean was considered as the need for restitution of artificial ventilation and reintubation within 48 hours after extubation, as established in the III Brazilian Consensus on Mechanical Ventilation (9) and in the Brazilian Mechanical Ventilation Guidelines (12) .  (18) .
The main factor that motivated the use of MV was respiratory failure (52.7%), followed by sensory lowering (21.5%) and by surgery (14% There was a statistical association between the mean age and the occurrence of DVWR, with each year increasing in age, there is a 1.03-fold increase in the chance of developing the outcome (Table 1).
For the gender and age group variables no significant association was found (p<0.05).
There were also no statistically significant differences Clinical severity at admission was significantly associated with failure to wean, with patients with higher scores in the SAPS 3 values having a higher chance of occurrence of DVWR ( Table 1).
The increase in heart rate was significantly associated with failure in extubation, increasing the chance of DVWR to 1.04 times for each unit increased in value (Table 1). Other vital signs such as respiratory rate, mean arterial pressure and peripheral oxygen saturation measured with an oximeter did not present statistically significant differences between the groups.   (Table 1). Additionally, with each point added to the locker value during the edema evaluation, there is an approximately 2-fold increase in the chance of the outcome occurring (Table 1). In addition, the presence of anasarca, occurrence of oliguria and hemodialysis increased the chance for the development of DVWR (Table 2).
Rev. Latino-Am. Enfermagem 2020;28:e3334.  (Table 1). There was also an association between the occurrence of thermal changes, such as hyperthermia and hypothermia, and the occurrence of this ND ( Table 2).
The administration of sedatives showed no statistical difference in relation to the outcome of extubation. In turn, the use of vasopressor, secretion amount in the orotracheal tube, presence of muscle retraction, and anxiety variables were statistically significant to the occurrence of DVWR (p<0.05) ( Table 2). However, for these variables there were problems in estimating the OR, which was associated with the fact that they did not have one of the categories or had 2 or fewer patients in a certain category.
The oxygenation index and the performance of the SBT also did not show any association with the occurrence of DVWR.
Patients submitted to NIV after extubation, in turn, presented 4 times more extubation failure than those in which this ventilatory support was not implemented ( Table 2).
There was no association between the occurrence of DVWR and the laboratory tests analyzed, such as gasometric parameters: pH, PaO 2 , pCO 2 , HCO 3  frequently after extubations (20.8%), followed by a drop in oxygen saturation and tachycardia (Table 3). It is worth mentioning that the patient could present more than one clinical indicator for determining DVWR.

Discussion
The process of interrupting mechanical ventilatory support is considered complex and liable to failure, making the removal of the patient from MV more difficult than maintaining it, which makes it difficult to determine the acceptable failure rate (19) . In this perspective, some authors describe weaning as a shady area of intensive care and that, even in specialized centers, can be considered a mixture of art and science (19)(20) .
According to the Brazilian Intensive Care Association, despite protocols implemented in various services, extubation failure has occurred in about 24% of the cases in Brazil (21) . In the present study, the overall incidence of failure in ventilatory weaning, configuring the occurrence of DVWR, was 44.09%. It is worth noting that the higher Rev. Latino-Am. Enfermagem 2020;28:e3334.
incidence of the diagnosis identified can be attributed to the high clinical severity observed in the patients who composed the sample. This fact may be related to the low occurrence of admissions and elective intubations, since one of the hospitals included in the study is a reference center for trauma, urgency and emergency.
Previous studies revealed that the prevalence of patients who failed in the process of ventilatory weaning, even after extensive evaluation of the extubation potential, varied between 5% and 30% (19,(21)(22)(23)(24)(25)(26) . It should be noted that these results reflect a different reality from the Brazilian one, since they are mostly data from international studies.
It is estimated that, in order to make a more accurate diagnosis of dysfunctional responses to the process, the nurse will need evidence to support characteristic findings for the condition (signs and symptoms) and must be able to identify patients at risk of developing this ND to establish, together to the multi-professional team, preventive intervention actions (27) .
In this study, from a competing cohort, clinical markers were identified to determine the occurrence of failure in ventilatory weaning and its related factors, in order to clinically validate the ND of DVWR.
The characteristics of the studied sample have similarities and divergences when compared to those found in the literature. Regarding gender, there was a slight predominance of women (52.7%). However, no statistical difference (p<0.05) was found related to the variable, which confirms the findings of other authors (22,25) .
As for the age group, there was a higher frequency of elderly people in the sample (61.3%), with a mean age of 60.77 years old (SD ± 18.9). Nevertheless, there was no statistical difference between the age group and the occurrence of DVWR (p<0.05). However, a statistical association was observed between the mean age and the occurrence of DVWR (p=0.02), which corroborates the findings reported by previous investigations (25,(28)(29) .
The association can be partially explained by the morphological and functional changes that occur in the respiratory system with aging, in addition to the greater number of comorbidities in this population.
Upon admission to the ICU, sepsis was the most identified medical diagnosis (25.8%), and SAH and COPD were the most frequent comorbidities in the sample. Although, in this study no statistically significant differences were identified between the extubation failure and success groups according to the medical diagnosis at admission and to the comorbidities.
The use of SAPS 3 is able to show scores that infer prognosis beyond 24 hours of admission and reflect the complexity of the care demanded considering the patient's clinical status (32) . Other authors (20,25,33) also found an association between SAPS 3 and the occurrence of weaning failure, concluding that the SAPS 3 system has a good discriminatory power during the ventilatory weaning process.
It is noteworthy that aspects related to fluid balance Silva LCR, Tonelli IS, Oliveira RCC, Lemos PL, Matos SS, Chianca TCM.
The exact role of decreased renal function on respiratory outcomes in critically ill patients is not yet fully elucidated, but it is suggested that this relationship can be partially explained by the interactions of fluids in respiratory muscle performance and lung volumes, which seems to be correlated with situations of systemic inflammation such as sepsis (35) . Thus, it is recommended that other cardiovascular factors be evaluated to analyze the value of hemodynamic monitoring and the role of diuretic therapy in preventing reintubation (29) .
Congestive heart failure has also been suggested as an important reason for the failure of weaning in patients with positive fluid balance, generally associated with increased pulmonary artery occlusion pressure (29,34) .
This data may explain the fact that the heart rate variable has shown a statistically significant association in conjunction with oliguria and limb edema.
In this context, the nurse plays a fundamental role in the fluid control of critically ill patients, evaluating congestive signs such as the presence of edema, anasarca, and pulmonary crackles during physical examination and identifying signs such as decreased urine volume and increased renal slag.
Infection also stands out as an important factor related to delayed weaning from MV and to a worse prognosis for patients on MV (36)(37) . It is considered that the associations observed between thermal changes and the number of antibiotics with the occurrence of DVWR may also be related to the context of the infection, since hyperthermia is considered a highly prevalent sign in the evolution of infectious conditions and the antibiotics are used in treatment.
It was found that patients undergoing NIV after extubation had 4 times more extubation failures. The implementation of this ventilatory support was also significantly associated in another investigation that evaluated 508 attempts at extubation and observed a 3.2 fold increase in the chance of failure when NIV was performed after the removal of the artificial airway (25) .
The literature shows that the group that needs NIV after extubation has a significantly higher proportion of patients with chronic respiratory disease, which is related to a higher incidence of extubation failure in adjusted analyses (38) .
When analyzing the related factors described in the DVWR taxonomy, it is observed that, among the physiological factors described by NANDA-I (14) , ineffective airway clearance, assessed considering the amount of secretion in the airways, in fact showed a statistically significant association (p <0.05) with the outcome.
Of the psychological factors (14) , only anxiety was evaluated in this study, as it was the only aspect in which a quantitative analysis was possible through the application of a scale, enabling to conduct statistical tests to verify associations with the studied outcome. Considering the situational factors described in NANDA-I (14) : environmental barrier, uncontrolled episodic energy demands, inappropriate pace in decreasing ventilatory weaning, and insufficient social support, it is highlighted that these were not evaluated in this investigation due to the difficulty of measuring these variables for the type of idealized clinical validation study.
Among the associated conditions mentioned by NANDA-I (14) , the history of ventilator dependence for more than 4 days was analyzed considering the MV time This result was similar to other studies that estimate that the process of MV removal takes up about half of the total time of ventilatory support (40)(41)(42) . However, both the weaning time and the total MV time, concerning the date of intubation until the day of extubation, did not show statistically significant differences between the groups.
The other associated condition described in the taxonomy, history of unsuccessful weaning attempts, was analyzed based on the performance of the SBT variable, since previous extubation failure was adopted as an exclusion criterion in this investigation. However, the SBT was also not statistically associated with the occurrence of DVWR.
In this study, among the clinical indicators present in the ND of DVWR, proposed by NANDA-I (14) and those Rev. Latino-Am. Enfermagem 2020;28:e3334.
identified in the studies selected in the ILR, tachypnea was observed more frequently after extubations, followed by a drop in oxygen saturation and tachycardia, which corroborates the previous findings which report that post-extubation respiratory failure, expressed by visible signs of increased respiratory effort, is a common event and is associated with increased morbidity and mortality in the ICU (22,43) .
The defining characteristics of this ND were the subject of a study conducted to verify the temporality occurrence of these clinical indicators. It was found that 18% of the defining characteristics proposed by the taxonomy occurred in the first 30 minutes of observation, and it is possible to classify these as short duration events, indicating the need to return to the ventilatory prosthesis, with sufficient severity to motivate the nursing team to interrupt the MV withdrawal process (17) . In this sense, the role of nurses is of fundamental importance for the early and accurate performance of weaning from MV, as well as in the implementation of various care for mechanically ventilated patients, which precede the weaning process (13) .
Therefore, it is imperative that nurses working It is also recommended to investigate other related factors described in NANDA-I (14) for the diagnosis and hemodynamic changes (elevated heart rate, use of vasopressors) and, finally, use of NIV after extubation.