Background and rationale {6a}
Critically ill patients on invasive mechanical ventilation (IMV) usually develop mucus retention, increasing the risk for associated morbidity [
1‐
5]. Endotracheal intubation and inflation of the endotracheal tube cuff are associated with a drastic decrease of mucocilliar transportation (aprox. 10x) and imped an effective cough. Additionally, the semi-sitting position at 30°, which is currently recommended by international guidelines to prevent ventilator-associated pneumonia, may further hinder mucus clearance because of the gravity force in the greater caliber airways. Also, the use of sedative and relaxing drugs may inhibit cilia motility and respiratory muscles activation which increases mucus retention. Finally, associated comorbidities and recurrent respiratory infections also play an important role in the increased production of respiratory secretions [
1‐
5].
Respiratory physiotherapy has been proposed as a potential strategy to prevent and/or reduce the retention of secretions in critical patients connected to invasive mechanical ventilation. The scientific evidence on the effectiveness of these techniques is not clearly conclusive and its safety has some related controversial. There are several publications that demonstrate the effectiveness of respiratory physiotherapy techniques in the mobilization of air volumes, expiratory flows, and respiratory secretions but still in an insufficient number so that clear evidence of effectiveness can be manifested in systematic review studies. Some of the respiratory physiotherapy techniques used in intensive care in ventilated patients try to modulate the ventilatory flows and improve the transport of mucus based on the double gas-liquid phase rationale. The use of these techniques is supported by laboratory evidence that mucus removal is enhanced when the expiratory flow is greater than the inspiratory flow. This is the case, for example, of the rapid chest compression technique, which aims to increase the expiratory flow and facilitate the transport of mucus to the exterior of the bronchial tree [
1,
2].
In many studies, the effectiveness of the technique of rapid chest compression in the mobilization of secretions and peak expiratory flow is studied. Although in the work of Lima et al. (2008) [
2] applied the thoracic compression technique, in one of its variants, to assess its effects in an animal model with atelectasis, using unilateral thoracic compression and concluding that the technique was not effective for the resolution of atelectasis with the mobilization of secretions. In a more recent work by Martí et al. (2013) [
1], the technique of manual thoracic compression with different intensities was applied in pigs in IMV, and it was concluded that, with the rapid application of the technique, the secretions were mobilized outwards the bronchial tree. In this last study, controlled and randomized, the movement of respiratory secretions was studied by fluoroscopy in tracheostomized, sedated, and in IMV pigs [
1,
2]. There are also studies that provide evidence of the technique of manual compression of the abdomen and chest in humans; Naue et al. (2011) [
4] studied its effects associated with the increase of the support pressure to assess the amount of suctioned secretions without finding differences between groups. In 2014, the same authors published a randomized clinical trial in which they studied the increase in inspiratory pressure of 10 cmH20 associated with the technique of manual compression of the abdomen and chest with an increase in the amount of secretions suctioned, the volume of exhaled air, and improvement in the pulmonary dynamics. In the same 2014, Guimarães et al. [
3] studied the effects of rapid thoracic compression on pulmonary mechanics, amount of secretions suctioned, and peak expiratory flow, finding significant differences in peak expiratory flow in the intervention group [
3‐
5].
Although the effects of the different variants of the rapid chest compression technique in the mobilization of secretions, pulmonary dynamics, and expiratory flow continue to be studied, some authors devoted themselves to studying their effects in other systems and in certain pathologies in order to justify their use in specific clinical situations. This is the case of the effects of the manual rapid chest compression technique on intracranial pressure in patients with acute brain injuries. The first clinical trial on this matter was carried out by Thiesen et al. (2005) [
6] where they studied the effects of some techniques of respiratory physiotherapy on intracranial pressure, among which manual thoracic compression with satisfactory results relative to the control of intracranial pressure was included; the conclusions were obtained without control group or randomization. Subsequently, Toledo et al. (2008) [
7] studied the effect of vibro-compression on intracranial pressure in patients with cranio-encephalic trauma concluding that the respiratory physiotherapy maneuver did not increase intracranial pressure or cerebral perfusion pressure, this study was also performed without control group or randomization. Cerqueira-Neto et al. (2010) [
8] and Cerqueira Neto et al. (2013) [
9], also without a control, blind, or randomization group, studied the effects of the expiratory flow acceleration technique, one of the possible variants of the technique, in patients with traumatic brain injury, concluding that it did not significantly alter the intracranial pressure [
6‐
9]. In a more recent study, Tomar et al. (2019) [
10] in a randomized crossover trial comparing the manual chest percussion with the mechanical chest vibration concluded that the manual percussion was associated with ICP increase.
From the literature review, it can be verified that there is little scientific evidence on the safety of manual rapid chest compression in critically ill patients with acute brain injury in invasive mechanical ventilation [
6‐
9,
11].
Patients with acute brain damage usually present respiratory complications associated with invasive mechanical ventilation and therefore could benefit from respiratory physiotherapy. However, the application of respiratory physiotherapy techniques in these patients could be associated with an increase in intracranial pressure [
7‐
10,
12]. The maneuvers of respiratory physiotherapy can momentarily increase intrathoracic pressure, decreasing venous return and increasing intracranial pressure [
6].
The intrathoracic pressure is directly related to the alveolar pressure and the manual rapid chest compression technique can increase momentarily the alveolar pressure. So, any technique that aims to increase the expiratory air flow must do it in a rapid way to avoid major intracranial pressure increases [
6,
13‐
17].
According to the bibliography, the increase in intracranial pressure is a contraindication for the application of some techniques in patients with acute brain injury since it can cause a decrease in cerebral perfusion pressure if it is sustained over time or if it is not accompanied of a rise in the mean arterial pressure. The lowering of cerebral perfusion pressure leads to associated damage in the control mechanisms of blood supply in areas of penumbra, which will be responsible for part of the neuroplasticity in the recovery phases of acute brain injuries, with all its implications [
10,
12,
18‐
20].
It is important to mention that different brain lesions may have different behaviors in terms of intracranial pressure and may present higher intervention risks [
18].
Cerebral lesions with a hemorrhagic component imply a more aggressive control of the mean arterial pressure and intracranial pressure and may present extreme complications with punctual rises, as these pressure rises may cause an increase in hemorrhagic lesions due to fragility. The ischemic brain lesions may have an inverse behavior since decreases in mean arterial pressure or increases in intracranial pressure can lead to decreases in the cerebral perfusion pressure and make the penumbra areas suffer [
18‐
21].
At present, there are no randomized clinical trials that have studied the effect of the manual rapid chest compression technique alone on intracranial pressure and that try to relate its behavior with the different kinds of acute brain injuries. Therefore, we believe that it is necessary to investigate the effects of the technique with the highest possible methodological rigor and quality [
10‐
12].
We propose this study, trying to control as many variables as possible and studying the effects of a single technique, in order to provide methodologically sound conclusions.