TY - JOUR

T1 - Therapeutic benefits of proning to improve pulmonary gas exchange in severe respiratory failure

T2 - focus on fundamentals of physiology

AU - Berg, Ronan M.G.

AU - Hartmann, Jacob Peter

AU - Iepsen, Ulrik Winning

AU - Christensen, Regitse Højgaard

AU - Ronit, Andreas

AU - Andreasen, Anne Sofie

AU - Bailey, Damian M.

AU - Mortensen, Jann

AU - Moseley, Pope L.

AU - Plovsing, Ronni R.

N1 - Publisher Copyright: © 2021 The Authors. Experimental Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society

PY - 2022

Y1 - 2022

N2 - New Findings: What is the topic of this review? The use of proning for improving pulmonary gas exchange in critically ill patients. What advances does it highlight? Proning places the lung in its ‘natural’ posture, and thus optimises the ventilation-perfusion distribution, which enables lung protective ventilation and the alleviation of potentially life-threatening hypoxaemia in COVID-19 and other types of critical illness with respiratory failure. Abstract: The survival benefit of proning patients with acute respiratory distress syndrome (ARDS) is well established and has recently been found to improve pulmonary gas exchange in patients with COVID-19-associated ARDS (CARDS). This review outlines the physiological implications of transitioning from supine to prone on alveolar ventilation-perfusion ((Formula presented.)) relationships during spontaneous breathing and during general anaesthesia in the healthy state, as well as during invasive mechanical ventilation in patients with ARDS and CARDS. Spontaneously breathing, awake healthy individuals maintain a small vertical (ventral-to-dorsal) (Formula presented.) ratio gradient in the supine position, which is largely neutralised in the prone position, mainly through redistribution of perfusion. In anaesthetised and mechanically ventilated healthy individuals, a vertical (Formula presented.) ratio gradient is present in both postures, but with better (Formula presented.) matching in the prone position. In ARDS and CARDS, the vertical (Formula presented.) ratio gradient in the supine position becomes larger, with intrapulmonary shunting in gravitationally dependent lung regions due to compression atelectasis of the dorsal lung. This is counteracted by proning, mainly through a more homogeneous distribution of ventilation combined with a largely unaffected high perfusion dorsally, and a consequent substantial improvement in arterial oxygenation. The data regarding proning as a therapy in patients with CARDS is still limited and whether the associated improvement in arterial oxygenation translates to a survival benefit remains unknown. Proning is nonetheless an attractive and lung protective manoeuvre with the potential benefit of improving life-threatening hypoxaemia in patients with ARDS and CARDS.

AB - New Findings: What is the topic of this review? The use of proning for improving pulmonary gas exchange in critically ill patients. What advances does it highlight? Proning places the lung in its ‘natural’ posture, and thus optimises the ventilation-perfusion distribution, which enables lung protective ventilation and the alleviation of potentially life-threatening hypoxaemia in COVID-19 and other types of critical illness with respiratory failure. Abstract: The survival benefit of proning patients with acute respiratory distress syndrome (ARDS) is well established and has recently been found to improve pulmonary gas exchange in patients with COVID-19-associated ARDS (CARDS). This review outlines the physiological implications of transitioning from supine to prone on alveolar ventilation-perfusion ((Formula presented.)) relationships during spontaneous breathing and during general anaesthesia in the healthy state, as well as during invasive mechanical ventilation in patients with ARDS and CARDS. Spontaneously breathing, awake healthy individuals maintain a small vertical (ventral-to-dorsal) (Formula presented.) ratio gradient in the supine position, which is largely neutralised in the prone position, mainly through redistribution of perfusion. In anaesthetised and mechanically ventilated healthy individuals, a vertical (Formula presented.) ratio gradient is present in both postures, but with better (Formula presented.) matching in the prone position. In ARDS and CARDS, the vertical (Formula presented.) ratio gradient in the supine position becomes larger, with intrapulmonary shunting in gravitationally dependent lung regions due to compression atelectasis of the dorsal lung. This is counteracted by proning, mainly through a more homogeneous distribution of ventilation combined with a largely unaffected high perfusion dorsally, and a consequent substantial improvement in arterial oxygenation. The data regarding proning as a therapy in patients with CARDS is still limited and whether the associated improvement in arterial oxygenation translates to a survival benefit remains unknown. Proning is nonetheless an attractive and lung protective manoeuvre with the potential benefit of improving life-threatening hypoxaemia in patients with ARDS and CARDS.

KW - acute respiratory distress syndrome

KW - COVID-19

KW - gas exchange

KW - gravity

KW - respiratory failure

KW - SARS-CoV-2

U2 - 10.1113/EP089405

DO - 10.1113/EP089405

M3 - Journal article

C2 - 34242438

AN - SCOPUS:85112394585

VL - 107

SP - 759

EP - 770

JO - Experimental Physiology

JF - Experimental Physiology

SN - 0958-0670

IS - 7

ER -