aOrthopaedic Registrar, St George’s University Hospital, London
bActing Consultant Intensivist, St George’s University Hospital, London
cConsultant Intensivist, St George’s University Hospital, London
Corresponding author e-mail: [email protected]
Published 28 April 2020
COVID-19 has resulted in redeployment of orthopaedic teams to new roles all over the country. One such role is that of the Proning Team. While orthopaedic surgeons may be familiar with placing patients in the prone position for surgery, the reasons for proning patients with COVID-19 are likely to be much less understood. This paper gives a brief insight into the physiology of why proning has proved to be helpful in patients with COVID-19 and, more importantly, how to do it safely.
Prone positioning involves placing a ventilated patient on their stomach to improve oxygenation. Patients are normally placed in this position for at least 16 hours per day. For the remaining time patients are placed supine, which allows access to lines and reduces the risk of pressure sores. Recent guidelines for patients with COVID-19 recommend prone ventilation1. While proning is predominantly reserved for intubated patients, it can also be considered in patients treated with non-invasive ventilation such as CPAP2.
COVID-19 is the disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and primarily affects the respiratory system. While most people suffer mild symptoms including fever and cough3, patients with severe symptoms present with worsening breathlessness and acute hypoxaemia. Hospital management is with supportive oxygen therapy in initial stages, although as the infection worsens non-invasive and / or invasive ventilation may be required.
Early data from Italy4 suggests that COVID-19 does not have a homogenous presentation in patients. Instead two particular pathophysiological phenotypes exist; type 1 patients have hypoxaemia but ‘compliant’ lungs, type 2 patients have hypoxaemia but ‘non-compliant’ lungs and a condition similar to Acute Respiratory Distress Syndrome (ARDS).
While both types can benefit from proning, the benefits are derived from different physiological reasons. Crucial to understanding is the V/Q (Ventilation/Perfusion) relationship, with ventilation describing the rate of alveolar ventilation and perfusion the rate of pulmonary blood flow. If ventilation or perfusion fall, then a V/Q mismatch will occur with resulting hypoxaemia.
ARDS will be familiar to orthopaedic surgeons as a sequelae of the insult from major trauma. ARDS decreases lung compliance, impairs oxygenation and is associated with high mortality rates5.
Awake patients are initially managed supine, a more comfortable and practical position. As patients remain supine, they will develop atelectasis of the dorsal alveoli, which are also already directly compressed by the heart. In contrast the ventral alveoli remain well ventilated. Blood, under the effect of gravity, tends to flow more dorsally rather than ventrally. The net result is that poorly ventilated dorsal alveoli have will adequate perfusion leading to shunt, while better ventilated ventral alveoli will have poorer perfusion (V/Q mismatch).
Proning helps in type 2 (ARDS) COVID patients by recruiting posterior lung alveoli, reducing atelectasis and aiding drainage of secretions. Proning in ARDS is well established; a multi-centre RCT (PROSEVA)6, a Cochrane review7 and a meta-analysis8 have all shown that placing patients with moderate to severe ARDS in the prone position is cost-effective and reduces mortality.
The pathophysiology of type 1 COVID patient is less well understood, but hypoxaemia seems to occur following an inflammatory reaction that leads to microvascular pulmonary thromboses9. There is again V/Q mismatch, but now with adequate ventilation and poor perfusion. Proning therefore reduces hypoxaemia by improving ventilation to better perfused areas of the lung not affected by the inflammatory process.
Placing a patient prone can improve outcomes but there are risks of significant complications, most of which are preventable. Proning requires teamwork, and good communication is essential. In the COVID-19 ICU environment this is made all the more difficult by the use of full personal protective equipment (PPE).
Six people; four staff for proning, an anaesthetist/intensivist managing the airway and an ICU nurse available by the bedside for assistance.
- Full PPE.
- Slide sheet, clean bedsheet, three pillows (extra pillows needed for larger patients).
- Airway trolley in the event of accidental extubation.
Prior to Proning
Supine to Prone
After placing patient prone
Table 1: Steps for safely carrying out a proning procedure
Moving the patient from prone to supine is performed by following almost identical steps as above, but without pillow placement at the start.
During the current COVID-19 pandemic our hospital, a large teaching hospital in South London, created a surge escalation plan of a greater than sevenfold increase in intensive care bed capacity. Doctors from other clinical and surgical teams were asked to bolster the existing intensive care staff and underwent a rigorous weeklong educational 'bootcamp', including how to prone and deprone ventilated patients. However, proning a patient safely takes time and also takes ICU staff away from the other patients on the unit. During surge periods, with many dozens of patients potentially benefiting from proning, dedicated proning teams were set up to relieve the pressure on ICU staff. Our teams consisted of five people including orthopaedic consultants, registrars and staff from other specialities such as audiology. The proning team lead carried a 'prone-phone' which the different ICU units could text to get the team to attend. Teams would typically attend each ICU in the morning to deprone patients and then reattend later in the afternoon to place them in the prone position overnight. A proning teaching session was set-up in a mock ICU ward for the T&O department to train teams on the procedure that included addressing the difficulties of doing it in PPE.
- Alhazzani W, Møller MH, Arabi YM, Loeb M, Gong MN, Fan E, et al. Surviving Sepsis Campaign: guidelines on the management of critically ill adults with Coronavirus Disease 2019 (COVID-19). Intensive Care Med. 2020 Mar 28. [Epub ahead of print].
- Intensive Care Society (2020). Bamford P, Bentley A, Dean J, Whitmore D, Wilson-Baig N. ICS Guidance for Prone Positioning of the Conscious COVID Patient 2020. Available at: https://emcrit.org/wp-content/uploads/2020/04/2020-04-12-Guidance-for-conscious-proning.pdf.
- Carlos WG, Dela Cruz CS, Cao B, Pasnick S, Jamil S. Novel wuhan (2019-nCoV) coronavirus. Am J Respir Crit Care Med. 2020;201(4):P7-P8.
- Gattinoni L, Chiumello D, Rossi S. COVID-19 pneumonia: ARDS or not? Crit Care. 2020;24:154.
- Phua J, Badia JR, Adhikari NK, Friedrich JO, Fowler RA, Singh JM, et al. Has mortality from acute respiratory distress syndrome decreased over time? A systematic review. Am J Respir Crit Care Med. 2009;179(3):220-7.
- Guérin C, Reignier J, Richard J-C, Beuret P, Gacouin A, Boulain T, et al. Prone positioning in severe acute respiratory distress syndrome. N Engl J Med. 2013;368(23):2159-68.
- Bloomfield R, Noble DW, Sudlow A. Prone position for acute respiratory failure in adults. Cochrane Database Syst Rev. 2015;(11):CD008095.
- Sud S, Friedrich JO, Adhikari NK, Taccone P, Mancebo J, Polli F, et al. Effect of prone positioning during mechanical ventilation on mortality among patients with acute respiratory distress syndrome: a systematic review and meta-analysis. CMAJ. 2014;186(10):E381-90.