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2021 : Volume 1, Issue 1

Influence of the Bed Head Positioning on the Current Expiratory Volume of Pediatric Patients in Mechanical Ventilation: A Pilot Clinical Controlled Trial

Author(s) : Camila Gemin R. Locatelli 1 , Valéria Cabral Neves 1 , Adriana Koliski 1 and José Eduardo Carreiro 1

1 Pediatric Intensive Care Unit , Federal University of Parana , Brazil

Open J Pediatr Neonatol

Article Type : Research Article

DOI : https://doi.org/10.53996/2769-6200.ojpn.1000101


Abstract

The elevated bed head position is an important therapeutic intervention that can reduce respiratory complications associated with mechanical ventilation. The objective of this study was to evaluate the effects of elevation at the head of the bed on the tidal volume, pressure variables, hemodynamic data and peripheral oxygen saturation in pediatric patients on mechanical ventilation. Methods: In a before-and-after clinical trial, 52 patients of both sexes, with a chronological age of 28 days to 14 years old, were admitted to the pediatric intensive care unit for more than 24 hours. These were positioned at 0º, 30º, 45º and 60º of elevation of the head of the bed. For each position, the expiratory tidal volume, pressure variables, hemodynamic data and peripheral oxygen saturation were evaluated.

Results: The patients presented an increase in the expired tidal volume, with the bed head angulation at 30º and 45º. Heart rate increased when the head was positioned at 60º. The peripheral oxygen saturation variable increased in the 30º and 45º positions. The systolic blood pressure variables and diastolic blood pressure showed a progressive increase in the 30º, 45º and 60º positions respectively. Significant effects on increasing the Sat
O2/FiOratio were observed in the 30º and 45º positions. Conclusion: This study demonstrated a significant increase in expired tidal volume and an increase in the SatO2/FiO2 ratio with the patient positioned at 30º and 45º of elevation of the head of the bed. The peripheral oxygen saturation variable increased in the 30º and 45º positions. The elevated bed head position should be considered when monitoring children during mechanical ventilation.

Description


Keywords

Pediatric Intensive Care Unit; Patient Positioning; Mechanical Ventilation

Introduction

In clinical practice, the therapeutic approach of infants and children must consider the understanding of a growing and developing organism. Therefore, specific knowledge of the anatomy and physiology of the respiratory system in children is of paramount importance [1,2]. High compliance of the rib cage, less developed respiratory muscles, fewer alveolar units and less lung compliance is characteristics observed in children. These conditions favor early muscle fatigue, collapse of the airways and alveoli, with reduced gas exchange area [3,4]. Therefore, the child's anatomy physiological aspects and the pathophysiological process of the disease are factors that directly influence the process of invasive mechanical ventilation (IMV) [1,2,4]. The use of IMV is a support method for the treatment of patients with acute or chronic respiratory failure in a pediatric intensive care unit (PICU) [1,2,4-8]. The elevated bed head position is an important therapeutic intervention that can reduce respiratory complications associated with mechanical ventilation. Patient positioning can optimize oxygen transport using the effect of gravity on cardiopulmonary and cardiovascular functions. Some positions, such as the prone position, can directly impact the possibility of a more homogeneous alveolar oxygenation, with a possible reduction in the risk of lung injury induced by mechanical ventilation [9-12]. Several studies have concluded that the elevated headboard from 30º is a strong recommendation in the prevention of pneumonia associated with mechanical ventilation [13-16]. The European Society for Intensive Care (2009) recommends raising the head of the bed preferably above 30º, unless it interferes with the care and comfort of the patient [16-18]. Decubitus changes have been extensively used in intensive care units as a treatment and prevention of several diseases that affect seriously ill patients19. However, the multidisciplinary teams working in pediatric intensive care units are conservative regarding the elevation of the bedside of critically ill patients [16,20,21]. This research aims to evaluate the behavior of expiratory tidal volume (VTE), pressure variables, hemodynamic data and peripheral oxygen saturation in pediatric patients on mechanical ventilation at different bedside angles in the pediatric population.


Methods

It was a clinical trial of the type before and after, carried out at the PICU from the Hospital de Clinics Complex of the Federal University of Paraná, in Curitiba, Paraná. The project was approved by the institutional Ethics Committee (Opinion No. 1,889,491/2017) and registered in the Brazilian Registry of Clinical Trials under number RBR-8S8C8C. The study included patients of both sexes, with chronological age of 28 days to 14 years old incomplete, admitted to the PICU for more than 24 hours, using invasive mechanical ventilation. The children were sedated and adapted to the mechanical ventilator and with hemodynamic stability and consent of parents and / or guardians by signing the informed consent form. Tracheostomies patients, with a previous diagnosis of pulmonary fibrosis, with unilateral pulmonary disease and with contraindication to bed head elevation were excluded from the study. For each patient the following data were noted: the identification data (hospital registration number and full name), sex, age, weight, date of birth, admission diagnosis, days of PICU admission, days of duration of mechanical ventilation and the outcome: discharge or death. The mechanical ventilation parameters analyzed were ventilator mode, inspiratory pressure, final positive expiratory pressure, respiratory rate, inspiratory time and inspired oxygen fraction. These data were collected through the graphic monitor of the ventilators.

Intervention

The researchers visited the PICU daily to monitor the patients. The study procedures were performed exclusively by the research responsible for the study. After data collection, the patients were positioned at 0º (position 0 = P0), 30º (position 1 = P1), 45º (position 2 = P2) and 60º (position 3 = P3) at the head of the bed. The patients included in the study were sedated, in a controlled care mode and completely adapted to the mechanical ventilator, according to the service protocol. For greater accuracy of the headboard angle adopted for each position, a goniometer (Carci®) was used, which is defined as an instrument with which angles are measured [22]. All patients were initially placed in the supine position with the headboard at 0º, with an interval of five minutes between one position and another. Next, the values of tidal volume, peak inspiratory pressure, plateau pressure, mean airway pressure, pulmonary distension pressure, heart rate, peripheral oxygen saturation, systolic blood pressure and diastolic artery pressure were measured. The same sequence was repeated for the head elevation positions at 30º, 45º and 60º [23].The records of expiratory tidal volume, peak inspiratory pressure, plateau pressure, mean airway pressure were collected through the screen of the ventilator's graphic monitor during each bedside positioning. Data on heart rate, systolic blood pressure, diastolic blood pressure and peripheral oxygen saturation were collected using the Bionet® multipara metric monitor. At the end of the evaluations, the researcher positioned the head of the patient's bed in the position he was in before the collection began (Figure 1).


Figure 1: Data collection flowchart.


Statistical Analysis

All data collected were entered into a Microsoft Excel® spreadsheet. After the conference, the database was exported to Statistica® 7.0 software in which the analyzes were carried out. Continuous variables were evaluated for their distribution and presented as arithmetic mean and standard deviation, for continuous variables with normal and median distribution (25-75% percentile), for those with asymmetric distribution. The model of analysis of variance for repeated measures (ANOVA) and Friedman's ANOVA were applied considering the values obtained in P0, P1, P2 and P3. The post-hoc tests used included the Bonferroni test for symmetric variables and the Wilcoxon test for asymmetric variables. For all tests used, a value of p <0.05 was considered as the minimum level of significance.

Results

In the period of the study, 153 patients admitted and 89 (58.1%) required invasive ventilator support. In the present study, 78 patients were recruited, but only 52 met the inclusion criteria. The other 26 patients were excluded because mechanical ventilation was withdrawn within 24 hours. The main indication for mechanical ventilation was respiratory failure. The median time on mechanical ventilation was seven and a half days. Of the 52 patients included in the study, 22 (42.3%) were female and 30 (57.7%) male, with a median age of 16.5 months, ranging from 1.0 to 132.0 months (95% CI = 30.96 - 45.81). The patients' diagnoses on admission were: 38 (73.1%) acute respiratory failure; 10 (19.2%) postoperative; 4 (7.7%) others (1 foreign body aspiration, 1 snakebite accident and 2 states of non-convulsive illness). The epidemiological characteristics of the studied sample are shown in Table 1.

Characteristics

Study group(n=52)

Sex F/M (n)

22/30

Age¹ (months)

16,5 (5,0-44,0)

Wheight¹ (kg)

9,5 (6,5-13,3)

Diagnosis

Acute respiratory failure (n,%)

38 (73,1%)

Post-operative (n,%)

10 (19,2%)

Others (n,%)

4 (7,7%)

Source: The author (2021).

Note: ¹Values expressed as median and 25-75% percentiles. F: female; M: male.


Table 1:
Epidemiological characteristics of the sample in the pediatric intensive care unit.


Table 2 shows the results of the mean, standard deviation and median of the mechanical ventilation parameters established for the patients in the study before the bed head positions.

Parameters

Study group(n=52)

Peak pressure (cmH2O) ¹

22,4 ± 4,9

Final expiratory pressure (cmH2O) ¹

9,2 ± 1,8

Respiratory rate (rpm) ¹

19,9 ± 2,6

Inspired oxygen fraction (%) ²

40,0 (30,0-50,0)

Inspiratory time (sec) ¹

0,8 ± 0,1

Sensitivity (cmH2O) ¹

-2,1 ± 0,5

Mechanical ventilation days²

7,5 (5,0 - 11,0)

Source: The author (2021).

Note: ¹Values expressed as mean ± standard deviation. ²Values expressed as median and 25-75% percentiles. cmH2O: centimeters of water.


Table 2:
Mechanical ventilation parameters in the pediatric intensive care unit.

Expiratory Tidal Volume

Graph 1 illustrates the behavior of expiratory tidal volume according to the patient's predicted weight. It was observed that at 30º and 45º of elevation of the head of the bed, the tidal volume showed a significant increase.



Graph 1:
Expired current volume (ML / KG) in the 0º, 30º, 45º and 60º angulation of the bed head.
Note: Test: ANOVA, Post-hoc: Bonferroni.

Peak Pressure, Plateau Pressure, Mean airway Pressure and Pulmonary Distension Pressure

Table 3 shows the values of peak inspiratory pressure, plateau pressure, mean airway pressure and pulmonary distention pressure, during bedside positions. There was no statistically significant difference for these variables.

Variables

30º

45º

60º

p

Peak pressure¹

24,80 ± 5,02

24,61 ± 5,03

24,59 ± 5,35

24,94±5,16

0,10

Plateau pressure¹

21,09 ± 4,29

21,36 ± 4,46

21,36 ± 4,48

21,34±4,46

0,84

Mean airway pressure¹

13,82 ± 2,48

13,89 ± 2,47

13,85 ± 2,49

13,92±2,47

0,85

Pulmonary distention pressure¹

11,98 ± 3,64

12,07 ± 3,69

12,19 ± 3,87

12,23±3,75

0,57

Source: The author (2021).

Note: Data presented as mean ± standard deviation. Test: ANOVA, Post-hoc: Bonferroni. ¹Values expressed in cmH20 (centimeters of water).


Table 3: Peak pressure, plateau pressure, average airway pressure and pulmonary distention pressure, pediatric intensive care unit.

Hemodynamic Data and Peripheral Oxygen Saturation

Table 4 shows the behavior of hemodynamic data and peripheral oxygen saturation during bedside positioning. Heart rate increased when the head was positioned at 60º; the peripheral oxygen saturation variable increased in the 30º and 45º positions; and, the variables systolic blood pressure and diastolic blood pressure showed a progressive increase in the 30º, 45º and 60º positions. All of these changes were statistically significant.

Variables

30º

45º

60º

p

FC (bpm)

136,13 ± 28,17

136,01 ± 28,10

137,36 ± 28,88

138,40 ± 29,27*

0,01*

FR (rpm)

20,01 ± 2,37

20,01 ± 2,37

20,01 ± 2,37

20,01 ± 2,37

-----

SpO2(%)

96,09 ± 4,00

96,61 ± 3,77*

96,61 ± 3,69*

96,25 ± 3,42

0,01*

PAS (mmHg)

97,84 ± 19,73

99,40 ± 20,36*

102,96 ± 17,89*

103,25 ± 19,15*

<0,01*

PAD (mmHg)

55,03 ± 15,82

56,34 ± 15,70*

61,05 ± 16,71*

61,38 ± 15,83*

<0,01*

Source: The author (2021).

Note: Data presented as mean ± standard deviation. ANOVA test, Post-hoc: Bonferroni, * p?0.01. HR: heart rate, bpm: beats per minute, FR: respiratory rate, rpm: breaths per minute, SpO2: peripheral oxygen saturation, SBP: systolic blood pressure, DBP: diastolic blood pressure, mmHg: millimeters of mercury.


Table 4: Hemodynamic data and peripheral oxygen saturation, pediatric intensive care unit.

SpO2/FiO2 Ratio

Graph 2 demonstrates the behavior of the SpO2/FiO2 ratio during the headboard positions, with a statistically significant increase in the 30º and 45º positions.


Graph 2: SPO2/FIO2 ratio in the 0º, 30º, 45º and 60º position of bed heading.
Source: The Author (2021).
Note: Test: Friedman's ANOVA, Post-hoc: Wilcoxon.

Discussion

This was the first intervention study involving a change in the angle of the head affects the respiratory mechanics of MV patients in our unit. It was possible to identify that the elevation of the head of the bed to 30º and 45º increased the tidal volume in pediatric patients. This knowledge is fundamental and should be used as an adjunct in pulmonary protection ventilation strategies. In our casuistic the median age was 16.5 months and 57.7% were male. The average age of pediatric patients receiving mechanical ventilation according to the literature is 12 months 24. The predominance of males is prevalent in several studies in the pediatric population, especially when the causes of hospitalization are respiratory [24-26].

In the present study, the main diagnosis on patient admission was acute respiratory failure and the vast majority with sepsis with pulmonary focus, of which 5 (10.0%) died. Lanetzkiet et al. (2012) in his study with 433 pediatric patients in the PICU, observed that respiratory causes occupy the first three positions of diagnoses at admission with 1.8% mortality. In a study by Batista et al. (2015), with 609 hospitalized patients, the respiratory system was the most affected (71.0%) and the death rate was 15.6% [25,27]. The median time on mechanical ventilation was seven and a half days. In 2004, Farias et al. found in their study that the average time spent on mechanical ventilation in these patients was 6 to 7 days, which corroborates with the present study [26]. Important studies on the indication of IMV in children have determined that, on average, one in six children admitted to the Pediatric Intensive Care Units need this support and its main indication is acute respiratory failure. But regardless of the indication, IMV is a significant cause of morbidity and mortality in pediatric patients [28,29]. Study patients were ventilated in controlled pressure mode. The PICU uses the controlled pressure mode for the ventilation of its patients. The main advantages of controlled pressure ventilation are obtaining higher mean airway pressure with lower inspiratory pressure, better oxygenation rates and better alveolar ventilation. In addition, controlled pressure ventilation has been used as part of the pulmonary protection strategy in patients with hypoxemic respiratory failure [11]. Regarding the values of peak pressure, plateau pressure, mean airway pressure and pulmonary distension pressure, during the headboard positions, no statistically significant difference was observed. In the present study, pulmonary distention pressure was maintained on average ? 12.2 cmH2O. The mechanical ventilation data used in the studied period are in accordance with the recommendations recommended in the current world literature [23,26,27,30-32].

The tidal volume was recognized as the variable that must be controlled during passive mechanical ventilation in order to avoid ventilator-induced lung injury, but recent data indicate that pulmonary distention pressure above 15 cmH20 is closely related to mortality in patients using mechanical ventilation [30-32]. Current mechanical ventilation devices calculate the tidal volume, where the use of tidal volumes around 6 ml/kg of predicted weight in children seems to be ideal and recommended in the literature. In PICU the increase in tidal volume, with a decrease in airway resistance and an increase in lung compliance, are considered an important goal [17-20]. Ventilation of the lungs involves expiration of resistance to flow, inertia and elastic properties of the respiratory system. The amount of pressure needed to move a volume is derived from the complacency of the respiratory system and the resistance of the airways. The measures of lung resistance and compliance are not constant during the respiratory cycle, using pressure-controlled ventilation. As the patient's resistance and complacency change, the volume released varies [4,22].

It is important to recognize that pressure, volume and flow change over time and are therefore variable. When pulmonary compliance decreases, airway resistance increases or when combined they constitute an overload for the respiratory and ventilator muscles. It is known that with increased tidal volume and increased lung compliance, there is less trans pulmonary pressure to deliver tidal volume to the lungs. Therefore, the increase in lung compliance reduces respiratory work and, in fact, increases the chances of success in removing the patient from the ventilator [2,27-29]. It is believed that a ventilator support with tidal volumes of 6ml / Kg of predicted weight, with pulmonary distention pressure <15 cmH2O and PEEP levels sufficient to prevent the collapse of the airways and alveoli, can guarantee an adequate gas exchange. In addition, the proper positioning of the patient on the bed can increase these protective measures [30,31]. Regarding hemodynamic data, an increase in heart rate was observed when the headboard was positioned at 60º. The variables systolic and diastolic blood pressure increased in the 30º, 45º and 60º positions progressively. Although without clinical relevance. Changes in HR, defined as heart rate variability, are normal and expected and indicate the heart's ability to respond to multiple physiological and environmental stimuli. The increase in HR is a consequence of the greater action of the sympathetic pathway and the lower parasympathetic activity [33,34].

The monitoring of the cardio circulatory system aims to prevent and detect instability of the clinical condition [34]. Blood pressure can be influenced by cardiac, respiratory and vasomotor actions. The acute rise in blood pressure is regulated by the sympathetic nervous system, being influenced by increases in heart rate, blood volume, ejection volume and increased peripheral vascular resistance [35]. The Sp
O2 is an estimate of your arterial blood saturation used to monitor patients in inpatient units. When using VMI, SpO2 is used to indicate if there is a need for adjustments in the ventilator support. It was observed in the study that there was an increase in SpO2 as the head of the 0º-30º and 0º- 45º position was changed, which did not happen from 0º- 60º. This improvement in SpO2 is related to the improvement in tidal volume, increased compliance and reduced resistance, which are interfering variables in gas exchange [36]. Rice et al. (2007) in their pioneering study on the SatO2/FiO2 ratio, observed that the SatO2/FiO2 values of 235 and 315 corresponded, respectively, to a PaO2/ FiO2 of 200 and 30037. Therefore, the SatO2/FiO2 data showed excellent sensitivity and good specificity in predicting the corresponding fraction of PaO2/FiO2. It is observed in the present study that the SatO2/FiO2 ratio had an increase in the positions 30º and 45º of elevation of the head of the bed. The assessment of the SatO2/FiO2 ratio in a non-invasive and continuous way can facilitate the early diagnosis of acute respiratory distress syndrome, in addition to reducing the number of arterial blood samples collected from patients under IMV [3,37]. Monitoring lung volumes at the bedside is important for a better understanding of the patient's evolution, optimizing the adjustments of ventilator parameters and ensuring the effectiveness of MV16. The scarcity of similar research in the current scientific literature on the positioning of mechanically ventilated patients and the small sample size were limitations of this study. However, relevant outcomes were addressed and the results were consistent and can be extrapolated to clinical practice in a Pediatric Intensive Care Unit. However, there is a need for more studies that address the topic.

Conclusion

The study demonstrated a significant increase in expired tidal volume with patients positioned at 30º and 45º of head elevation. There were no significant changes in the pressure parameters of mechanical ventilation. The peripheral oxygen saturation variable increased in the 30º and 45º. And the SatO2/FiO2 ratio increased significantly with the head elevation at 30º and 45º.

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CORRESPONDENCE & COPYRIGHT

Corresponding Author: Camila Gemin R. Locatelli, Pediatric Intensive Care Unit, Complexo Hospital de Clínicas, Federal University of Paraná (UFPR), Curitiba (PR), Brazil.

Copyright: © 2021 All copyrights are reserved by Camila Gemin R. Locatelli, published by Coalesce Research Group. This This work is licensed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited.


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