Question 25

Angoff score

6.05

Highest mark

Regarding prone positioning of patients with severe ARDS:
a) Discuss the physiological rationale for its use. (6 marks)

b) List FOUR complications of prone positioning and provide a mitigation strategy for each
complication. (4 marks)

[Click here to toggle visibility of the answers]

College answer

Syllabus topic/section:

2.1.5 Respiratory intensive care: Acute respiratory distress syndrome, Prone positioning: L1

Discussion:

Answers to part a) could be improved by familiarity with the glossary term ‘discuss’, and reference to the status of this topic in the syllabus (Level 1 for both ARDS and prone positioning). Discussion of Level 1 topics requires depth. A discussion asks candidates to address underlying key principles. A list of physiologic effects of prone positioning does not address the depth required, though it is a good springboard for a more in-depth discussion.
Many candidates answered Part b) well and this likely reflects the increased use of proning in clinical practice. The marking rubric is included to aid the candidate’s future study.

	Below standard	At standard	Above standard
a) Discuss the physiological rationale of prone positioning with severe ARDS.	Incomplete/incorrect answer Does not include V/Q mismatch	Must include: Improved V/Q matching and any 2 other physiological effects at a minimum As the question is discuss listing alone is not sufficient to pass must include some detail	At standard level plus provides a more comprehensive response that is broad and covers most of the physiologic rationale linked to pathophysiology of ARDS with an increased level of detail
(6 marks)	0 – 2.5 marks	3 – 4.5 marks	5- 6 marks
b) List four complications and mitigation strategies	Provides less than 4 reasonable complications with mitigation strategies OR Provides 4 complications, without mitigation strategy	Provides 4 reasonable complications, AND Provides 4 well-described mitigation strategies with some omissions	Provides 4 reasonable complications, AND Provides 4- comprehensive mitigation strategies
(4 marks)	0-1.5 marks	2-3 marks	3.5-4 marks

Discussion

a) Rationale, for six marks, would have to be something more solid than just a list, eg:

Improved V/Q matching
- redistributes ventilation to the posterior lung, which still receives a large amount of blood flow
More homogeneous ventilation because of reduced difference between the dorsal and ventral pleural pressure
- More uniform distribution of pleural pressure;
- Thus, more uniform compliance;
- Thus, more uniform distribution of plateau pressure;
- Thus, less cyclical atelectasis and alveolar overdistension.
Less lung deformation, by the heart (which sits on the sternum in the prone position) and by the abdominal content
- thus improved compliance
- thus less injurious ventilation
Increased FRC
- increases by about 300-400ml
Improved drainage of secretions
- dorsoventral orientation of large airways
Improved response to recruitment manoeuvres
- prone patients seem to require less PEEP (8cm vs 14cm) to sustain the post-recruitment improvement in oxygenation.
Improved chest wall mechanics in obesity
- pressure from abdominal content does not affect the diaphragmatic excursion as much as it would in supine position

These were arranged in an ABCDE order, to better match other similar lists. Bruni et al (2021) is an excellent resource for this:

Complication	Mitigating strategy
ETT dislodgement	Dedicated staff for airway hold during positioning Specialised immobilisation face pillow to hold the tube during proning/deproning Attention ot ventilator tubing slack and position
ETT kink/obstruction	Head positioning devices to relieve neck flexion/extension Small mirrors positioned under the face to observe tube position Use of more rigid (eg,. reinforced) tubes
Haemodynamic instability	Mostly related to preload Therefore, ensure adequate fluid volume Reschedule prone positioning for periods of haemodynamic stability
Increased sedation requirement	Multimodal approach to reduce toxicities from single agents Sedation holidays during deproned periods Use of spontaneous modes (eg. APRV) to reduce sedation requirements A focus on analgesia and dissociative anaesthesia rather than classical general anesthetics
Raised ICP	Tilt the bed head up Manage with osmotherapy Aim for a higher MAP to ensure perfusion
Airway oedema	Tilt the bed head up Conservative fluid strategy Diuresis
Poor enteral feed tolerance	Tilt the bed head up Prokinetics Concentrate feeds into deproned time intervals release abdominal pressure by repositioning pillows
Line dislodgement	Assign staff to specifically mind the lines during positioning
Pressure injury	Soft eye pads, facial pillows, towels and shape-memory foam pads Alternate "swimmer's poosition" to avoid brahcial plexus injury Abduct arm to 90 degrees Replace rigid anterior immobilisation devices with tapes or ties Reposition lines to prevent hubs from forming pressure areas Wrap hard devices with gause or towels Focus on enhancing tissue perfusion, eg. shock management with an emphasis on fluid rather than vasopressors

References

Tisdall, M

Mackenzie, Colin F. "Anatomy, physiology, and pathology of the prone position and postural drainage." Critical care medicine 29.5 (2001): 1084-1085.

Lamm, W. J., Michael M. Graham, and Richard K. Albert. "Mechanism by which the prone position improves oxygenation in acute lung injury." American journal of respiratory and critical care medicine 150.1 (1994): 184-193.

Binda, Filippo, et al. "Complications of prone positioning in patients with COVID-19: a cross-sectional study." Intensive and Critical Care Nursing 67 (2021): 103088.

Rollinson, Thomas C., et al. "Complications associated with prone positioning in mechanically ventilated COVID-19 patients: A multicentre, retrospective observational study." Australian Critical Care 38.2 (2025): 101117.

Elmer, Nancy, et al. "Long-term complications of prone position ventilation with relevance for acute and postacute rehabilitation: a systematic review of the literature." European Journal of physical and rehabilitation Medicine 59.1 (2022): 111.

Bruni, Andrea, Eugenio Garofalo, and Federico Longhini. "Avoiding complications during prone position ventilation." Intensive & critical care nursing 66 (2021): 103064.

[Submit a comment or correction]