PRONE POSITIONING PRONE POSITIONING IN ARDSIN ARDS

BYBYDR. MUHAMMAD AKRAM DR. MUHAMMAD AKRAM

INTENSIVE CARE UNITINTENSIVE CARE UNITMATERNITY AND CHILDREN HOSPITALMATERNITY AND CHILDREN HOSPITAL

MAUSADIA JEDDAHMAUSADIA JEDDAH

Definition of ARDSDefinition of ARDS

American – European Consensus Conference in American – European Consensus Conference in 1993 defined ARDS as:-1993 defined ARDS as:- Clinical syndrome requiring the presence of :-Clinical syndrome requiring the presence of :- severe oxygenation abnormality with PaO2/FiO2 severe oxygenation abnormality with PaO2/FiO2

<200 torr<200 torr Diffuse bilateral pulmonary infiltrates on chest Diffuse bilateral pulmonary infiltrates on chest

radiograph, involving 03or 04 quadrantsradiograph, involving 03or 04 quadrants Pulmonary Capillary Wedge Pressure <18mmHgPulmonary Capillary Wedge Pressure <18mmHg Absence of clinical elevation of left sided filling Absence of clinical elevation of left sided filling

pressure.pressure. Synonymous term ALI ( Acute Lung Injury) meets Synonymous term ALI ( Acute Lung Injury) meets

the same criteria , except the PaO2/FiO2 ratio of the same criteria , except the PaO2/FiO2 ratio of <300 <300

WHAT IS PRONE POSITIONING?WHAT IS PRONE POSITIONING?

MECHANISMS OF ACTIONMECHANISMS OF ACTION EFFECTS ON FRCEFFECTS ON FRC

The volume of gas remaining in the lungs after a normal The volume of gas remaining in the lungs after a normal exhalation exhalation

In the supine position, functional residual capacity (FRC) In the supine position, functional residual capacity (FRC) decreases due to compression of the lungs by the decreases due to compression of the lungs by the diaphragm due to intra-abdominal pressure. diaphragm due to intra-abdominal pressure.

In the prone position particularly with the abdomen In the prone position particularly with the abdomen unsupported, abdominal weight shifts the diaphragm unsupported, abdominal weight shifts the diaphragm caudally, increasing the FRC caudally, increasing the FRC

. In normal and obese anaesthetized and paralyzed . In normal and obese anaesthetized and paralyzed patients prone positioning resulted in improved FRC and patients prone positioning resulted in improved FRC and oxygenation. Increased FRC results in end expiratory oxygenation. Increased FRC results in end expiratory alveolar recruitment alveolar recruitment

MECHANISMS OF ACTIONMECHANISMS OF ACTION EFFECTS ON PERFUSIONEFFECTS ON PERFUSION

In the supine position there is a perfusion gradient from the In the supine position there is a perfusion gradient from the dependent dorsal lung to the non-dependent ventral lung dependent dorsal lung to the non-dependent ventral lung

SPECT imaging of intravenously injected radiolabelled albumin SPECT imaging of intravenously injected radiolabelled albumin demonstrated maintenance of dorsal predominant flow in the prone demonstrated maintenance of dorsal predominant flow in the prone position . position .

Regional perfusion is always preferentially directed to dorsal lung Regional perfusion is always preferentially directed to dorsal lung regions regardless of whether these regions are in the dependent or regions regardless of whether these regions are in the dependent or nondependent position. This non-gravitational blood flow has nondependent position. This non-gravitational blood flow has implications for understanding the mechanism by which the prone implications for understanding the mechanism by which the prone position results in improved gas exchange.position results in improved gas exchange.

If the dorsal regions always receive preferential perfusion the only If the dorsal regions always receive preferential perfusion the only way intra-pulmonary shunt can be reduced is as a result improved way intra-pulmonary shunt can be reduced is as a result improved regional ventilation of underventilated or atelectatic dorsal regions in regional ventilation of underventilated or atelectatic dorsal regions in the prone position which are perfused but not well ventilated when the prone position which are perfused but not well ventilated when supine. supine.

MECHANISMS OF ACTIONMECHANISMS OF ACTION

EFFECTS ON VENTILATIONEFFECTS ON VENTILATION Regional lung ventilation is determined by the pleural pressure gradient Regional lung ventilation is determined by the pleural pressure gradient In normal subjects in the supine position the non-dependent ventral In normal subjects in the supine position the non-dependent ventral

lung has a more negative pleural pressure compared to the dependent lung has a more negative pleural pressure compared to the dependent dorsal lung region and this determines regional ventilation with the dorsal lung region and this determines regional ventilation with the ventral lung receiving more ventilation. ventral lung receiving more ventilation.

In the setting of acute lung injury in the supine position the pleural In the setting of acute lung injury in the supine position the pleural pressure of the non-dependent ventral lung remains negative, however pressure of the non-dependent ventral lung remains negative, however the pleural pressure of the dependent dorsal lung region becomes the pleural pressure of the dependent dorsal lung region becomes positive. This large pleural pressure gradient results in overdistension of positive. This large pleural pressure gradient results in overdistension of the ventral lung and reduced ventilation to the dorsal lung. the ventral lung and reduced ventilation to the dorsal lung.

In addition the positive pleural pressure in the dorsal lung region tends In addition the positive pleural pressure in the dorsal lung region tends to promote atelectasis further reducing ventilation in this regionto promote atelectasis further reducing ventilation in this region

. In the prone position, the ventral - dorsal pleural pressure gradient is . In the prone position, the ventral - dorsal pleural pressure gradient is markedly reduced markedly reduced

The prone position eliminates the compression of the lungs by the heart The prone position eliminates the compression of the lungs by the heart

MECHANISMS OF ACTIONMECHANISMS OF ACTION

MISCELLANEOUS EFFECTSMISCELLANEOUS EFFECTS It is interesting to note that prone position has been shown to It is interesting to note that prone position has been shown to

induce redistribution of lung density indicating more uniform induce redistribution of lung density indicating more uniform regional ventilation. This suggests additional mechanisms may regional ventilation. This suggests additional mechanisms may be important in improving gas exchange.be important in improving gas exchange.

Improved mobilization of secretions or redistribution of Improved mobilization of secretions or redistribution of extravascular lung water. The significance of alteration in extravascular lung water. The significance of alteration in extravascular lung water (EVLW) in ARDS remains to be extravascular lung water (EVLW) in ARDS remains to be defined.defined.

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CLINICAL EFFECTS CLINICAL EFFECTS EFFECT ON OXYGENATIONEFFECT ON OXYGENATION

Prone positioning was first reported to improve oxygenation in acute Prone positioning was first reported to improve oxygenation in acute respiratory failure in two small studies in the 1970s respiratory failure in two small studies in the 1970s

EFFECT ON RESPIRATORY MECHANICSEFFECT ON RESPIRATORY MECHANICS Associated with an initial decrease in respiratory system compliance which Associated with an initial decrease in respiratory system compliance which

subsequently improves during the prone period and increases when subsequently improves during the prone period and increases when returned to supine. returned to supine.

The initial reduction when the patient is turned prone is probably due to a The initial reduction when the patient is turned prone is probably due to a decrease in chest wall compliance. It is suggested that maintaining decrease in chest wall compliance. It is suggested that maintaining support of the abdomen might have avoided the initial increase in support of the abdomen might have avoided the initial increase in respiratory system compliance respiratory system compliance

In contrast, the subsequent improvement seems to relate to the increase In contrast, the subsequent improvement seems to relate to the increase in lung compliance.in lung compliance.

EFFECT ON CO2 CLEARANCE EFFECT ON CO2 CLEARANCE Prolonged prone ventilation is associated with improvement in CO2 Prolonged prone ventilation is associated with improvement in CO2

clearance which is related to improvement in alveolar ventilation in well-clearance which is related to improvement in alveolar ventilation in well-perfused areas.perfused areas.

PRONE POSITIONING FOR ARDS PRONE POSITIONING FOR ARDS

Treatment of ARDS is largely supportiveTreatment of ARDS is largely supportive Prone positioning has been suggested since 1974 (9) as a Prone positioning has been suggested since 1974 (9) as a

ventilatory strategy to improve oxygenation and pulmonary ventilatory strategy to improve oxygenation and pulmonary mechanics in patients with ALI and ARDS. mechanics in patients with ALI and ARDS.

INDICATIONS:INDICATIONS: Pulmonary dysfunction despite escalating mechanical Pulmonary dysfunction despite escalating mechanical

ventilatory support ventilatory support GOALS OF VENTILATION:GOALS OF VENTILATION:

SaO2 >92% SaO2 >92% PaO2/FiO2 ≥200 PaO2/FiO2 ≥200 pH 7.25 – 7.40 pH 7.25 – 7.40 Pplat <35 cm H2O Pplat <35 cm H2O

PRONE POSITIONING FOR ARDS PRONE POSITIONING FOR ARDS

Criteria for Inclusion:Criteria for Inclusion: CXR with diffuse bilateral infiltrates CXR with diffuse bilateral infiltrates

consistent with ALI or ARDS consistent with ALI or ARDS Mechanical ventilation Mechanical ventilation

FiO2 ≥ 0.6 for 48 hours FiO2 ≥ 0.6 for 48 hours PEEP ≥ 15 cm for 48 hours (includes PCIRV, auto PEEP ≥ 15 cm for 48 hours (includes PCIRV, auto

PEEP) PEEP) Increasing respiratory dysfunction as Increasing respiratory dysfunction as

evidenced by: evidenced by: PaO2/FiO2 < 200 PaO2/FiO2 < 200

PRONE POSITIONING FOR ARDS PRONE POSITIONING FOR ARDS

Exclusion Criteria:Exclusion Criteria: Closed head injury with ICH Closed head injury with ICH Unstable orthopedic fracture Unstable orthopedic fracture Spinal cord injury Spinal cord injury Hemodynamic instability Hemodynamic instability Active intraabdominal process Active intraabdominal process Pregnancy Pregnancy

TECHNIQUE OF POSITIONINGTECHNIQUE OF POSITIONING There is no standardized method for turning.There is no standardized method for turning. Most studies describe a log roll in two steps with the variable use of a Most studies describe a log roll in two steps with the variable use of a

glide sheet under the patient. glide sheet under the patient. In the first step the patient is moved to one edge of the bed and then In the first step the patient is moved to one edge of the bed and then

moved into the lateral position to face the other edge of the bed.moved into the lateral position to face the other edge of the bed. In the second step the patient is placed in the prone position. In the second step the patient is placed in the prone position. One study used a portable support frame that acts as an anchor for the One study used a portable support frame that acts as an anchor for the

body during the turn and then serves as a cushion device to maintain the body during the turn and then serves as a cushion device to maintain the abdomen free of restriction in the prone position.abdomen free of restriction in the prone position.

In the majority of studies 5 persons including an experienced physician In the majority of studies 5 persons including an experienced physician who can re-intubate the patient if necessary were used to turn the who can re-intubate the patient if necessary were used to turn the patient.patient.

In one study 3 members of nursing staff turned the patient. In this study In one study 3 members of nursing staff turned the patient. In this study there was only one unplanned extubation in 148 turning prone cycles there was only one unplanned extubation in 148 turning prone cycles (supine – prone – supine) which was treated immediately with no (supine – prone – supine) which was treated immediately with no deleterious effect.deleterious effect.

Each person has a defined role, with one person having responsibility for Each person has a defined role, with one person having responsibility for the airway. the airway.

Prior to turning any patient prone proper placement and fixation of the Prior to turning any patient prone proper placement and fixation of the endotracheal tube must be confirmed.endotracheal tube must be confirmed.

TECHNIQUE OF POSITIONINGTECHNIQUE OF POSITIONING Vascular lines must also be monitored during turning to avoid Vascular lines must also be monitored during turning to avoid

displacement. displacement. Following repositioning, the endotracheal tube and all catheters Following repositioning, the endotracheal tube and all catheters

should be surveyed to assure that no displacement has should be surveyed to assure that no displacement has occurred.occurred.

The importance of avoiding non-physiological movement of the The importance of avoiding non-physiological movement of the arms during turningarms during turning

the importance of protecting pressure areas including areas the importance of protecting pressure areas including areas overlying all tubes and Foley and intravascular catheters and overlying all tubes and Foley and intravascular catheters and avoiding ocular injury was emphasized. avoiding ocular injury was emphasized.

It is emphasized that staff involved in the management of It is emphasized that staff involved in the management of patients in the prone position should be aware of the procedure patients in the prone position should be aware of the procedure to rapidly turn patients with severe cardiopulmonary instability, to rapidly turn patients with severe cardiopulmonary instability, as CPR requires a return to the supine position.as CPR requires a return to the supine position.

TECHNIQUE OF POSITIONINGTECHNIQUE OF POSITIONING Reposition ECG leads to patient’s back. Reposition ECG leads to patient’s back. Anticipate the need for frequent ETT suctioning. Anticipate the need for frequent ETT suctioning. Obtain ABG 20 minutes after repositioning. Obtain ABG 20 minutes after repositioning. Duration of prone positioning is dependent upon patient’s Duration of prone positioning is dependent upon patient’s

hemodynamic statushemodynamic status

PREDICTION OF RESPONSEPREDICTION OF RESPONSE Methods of predicting a positive response to prone Methods of predicting a positive response to prone

positioning are not well studied.positioning are not well studied. Langer was the first to classify patient as “responders” and Langer was the first to classify patient as “responders” and

“non-responders” according to the presence or absence of an “non-responders” according to the presence or absence of an increase in paO2 of more than 10mmHg after 30 minutes. increase in paO2 of more than 10mmHg after 30 minutes.

Subsequently the definition of response varied widely. Subsequently the definition of response varied widely. Change has been measured both in absolute change in paO2 Change has been measured both in absolute change in paO2 and paO2 / FiO2 ratio as well as percentage change in the and paO2 / FiO2 ratio as well as percentage change in the paO2 / FiO2 ratio.paO2 / FiO2 ratio.

Both the magnitude of change and time period over which Both the magnitude of change and time period over which the change is measured have varied widely.the change is measured have varied widely.

Several studies divide the groups into responders and non-Several studies divide the groups into responders and non-responders but do not actually define the criteria on which responders but do not actually define the criteria on which this is basedthis is based

Though available research makes no specific Though available research makes no specific recommendations, 6 or more hours a day, for as long as 10 recommendations, 6 or more hours a day, for as long as 10 days, appears typical in clinical studies and reported practice.days, appears typical in clinical studies and reported practice.

IS IT ARDS ?IS IT ARDS ?