Influence of Positioning on Ventilation-Perfusion Relationships in Severe Adult Respiratory Distress Syndrome

doi:10.1378/chest.106.5.1511

Chest

Volume 106, Issue 5, November 1994, Pages 1511-1516

https://doi.org/10.1378/chest.106.5.1511 Get rights and content

In 12 patients with severe adult respiratory distress syndrome (ARDS), pulmonary gas exchange and hemodynamics were evaluated before, during, and after a 2-h period of pressure-controlled mechanical ventilation with the patient in the prone position. Ventilation-perfusion relationships ( ${\dot{V}}_{A} / \dot{Q}$ ) were assessed by a multiple inert gas elimination technique. Pressure-controlled mechanical ventilation in the prone position resulted in an overall increase (p≤0.05) of arterial oxygenation after 120 min (98.4 ± 50.3 to 146.2 ± 94.9 mm Hg). Whereas eight patients revealed an improvement of PaO₂ of more than 10 mm Hg after 30 min in the prone position (responders), four patients reacted to positional changes with a deterioration of arterial oxygenation (nonresponders). Data about the continuous distribution of ventilation-perfusion ratios revealed that in the responder group positioning caused a decrease of shunt perfusion of 11 ± 5% and a concomitant increase of normal ${\dot{V}}_{A} / \dot{Q}$ by 12 ± 4% after 30 min. There was no change demonstrable within low ${\dot{V}}_{A} / \dot{Q}$ areas. Returning the patient to the supine position reversed the improvement in gas exchange. The nonresponder group did not show any significant alteration in the distribution of ${\dot{V}}_{A} / \dot{Q}$ during the study. We concluded that improvement of oxygenation during pressure-controlled mechanical ventilation in the prone position is due to a shift of blood flow away from shunt regions, thus increasing areas with normal ${\dot{V}}_{A} / \dot{Q}$ . This redistribution of blood flow is most likely caused by a recruitment of previously ateletatic but nondiseased areas induced by altered gravitational forces.

Section snippets

Study Population

After approval by the institutional human ethics committee, 12 patients who had been transferred to our unit for treatment of severe ARDS classified by Murray score⁶ were included into this study (Table 1). The study was performed on the second day after admission. Patients with bronchopleural fistula were excluded from the study. All patients had a tracheotomy and were sedated, paralyzed, and mechanically ventilated in the pressure control mode with pressure levels and PEEP adjusted to

Results

In the overall population, the prone position during pressure-controlled mechanical ventilation resulted in a markedly, although not significant (p=0.06) increase of PaO₂ after 30 min from 98.4 ± 50.3 to 136.1 ± 99.5 mm Hg. The arterial oxygenation improved significantly after 120 min in the prone position, when compared with baseline (146.2 ± 94.9 mm Hg, 120 min, vs baseline [p=0.027]). Returning the patient to the supine position after 120 min in a prone position caused a significant drop of

Discussion

As it is shown in this study, improvement in arterial oxygenation during pressure-controlled mechanical ventilation in the prone position resulted from a redistribution of blood flow away from unventilated areas to regions with normal ventilation-perfusion ratios, most likely resulting from an alveolar recruitment in previously atelectatic but healthy lung regions.

Consistent with the results by Langer et al,⁵ only 75% of the patients responded immediately to the prone position with an

ACKNOWLEDGMENT

The authors thank Mrs. G. Kaufmann, Frank Lopez, and Gottfried Merker for their excellent technical assistance.

References (21)

LangerM et al.
The prone position in ARDS patients: a clinical study.
Chest
(1988)
LillyCM et al.
The measurement of lung water.
J Crit Care
(1990)
BryanAC
Comments of a devil's advocate.
Am Rev Respir Dis
(1974)
PiehlMA et al.
Use of extreme position changes in acute respiratory failure.
Crit Care Med
(1976)
DouglasWW et al.
Improved oxygenation in patients with acute respiratory failure: the prone position.
Am Rev Respir Dis
(1977)
GattinoniL et al.
Body position changes redistribute lung computed-tomographic density in patients with acute respiratory failure.
Anesthesiology
(1991)
MurrayJF et al.
An expanded definition of the adult respiratory distress syndrome [published erratum appears in Am Rev Respir Dis 1988; 139:1065].
Am Rev Respir Dis
(1988)
WagnerPD et al.
Measurement of continuous distribution of ventilation-perfusion ratios: theory.
J Appl Physiol
(1974)
WagnerPD et al.
Simultaneous measurement of eight foreign gases in blood by chromatography.
J Appl Physiol
(1974)
LundhR et al.
Ventilation-perfusion relationships during halothane anaesthesia and mechanical ventilation: effects of varying inspired oxygen concentration.
Acta Anaesthesiol Scand
(1984)

There are more references available in the full text version of this article.

Cited by (302)

Non-invasive oxygenation strategies for respiratory failure with COVID-19: A concise narrative review of literature in pre and mid-COVID-19 era
2021, Anaesthesia Critical Care and Pain Medicine
The coronavirus disease 2019 (COVID-19) has spread globally and can cause a shortage of medical resources, in particular, mechanical ventilators. High-flow nasal cannula oxygen therapy (HFNC) and non-invasive positive pressure ventilation (NPPV) are frequently used for acute respiratory failure patients as alternatives to invasive mechanical ventilation. They are drawing attention because of a potential role to save mechanical ventilators. However, their effectiveness and risk of viral spread are unclear. The latest network meta-analysis of pre-COVID-19 trials reported that treatment with non-invasive oxygenation strategies was associated with improved survival when compared with conventional oxygen therapy. During the COVID-19 pandemic, a lot of clinical research on COVID-19 related acute respiratory failure has been reported. Several observational studies and small trials have suggested HFNC or NPPV as an alternative of standard oxygen therapy to manage COVID-19 related acute respiratory failure, provided that appropriate infection prevention is applied by health care workers to avoid risks of the virus transmission. Awake proning is an emerging strategy to optimise the management of patients with COVID-19 acute respiratory failure. However, the benefits of awake proning have yet to be assessed in properly designed clinical research. Although HFNC and NPPV are probably effective for acute respiratory failure, the safety data are mostly based on observational and experimental reports. As such, they should be implemented carefully if adequate personal protective equipment and negative pressure rooms are available.
Ten golden rules for individualized mechanical ventilation in acute respiratory distress syndrome
2021, Journal of Intensive Medicine
Considerable progress has been made over the last decades in the management of acute respiratory distress syndrome (ARDS). Mechanical ventilation(MV) remains the cornerstone of supportive therapy for ARDS. Lung-protective MV minimizes the risk of ventilator-induced lung injury (VILI) and improves survival. Several parameters contribute to the risk of VILI and require careful setting including tidal volume (V_T), plateau pressure (P_plat), driving pressure (ΔP), positive end-expiratory pressure (PEEP), and respiratory rate. Measurement of energy and mechanical power allows quantification of the relative contributions of various parameters (V_T, P_plat, ΔP, PEEP, respiratory rate, and airflow) for the individualization of MV settings. The use of neuromuscular blocking agents mainly in cases of severe ARDS can improve oxygenation and reduce asynchrony, although they are not known to confer a survival benefit. Rescue respiratory therapies such as prone positioning, inhaled nitric oxide, and extracorporeal support techniques may be adopted in specific situations. Furthermore, respiratory weaning protocols should also be considered. Based on a review of recent clinical trials, we present 10 golden rules for individualized MV in ARDS management.
Evaluation of PEEP and prone positioning in early COVID-19 ARDS
2020, EClinicalMedicine
In face of the Coronavirus Disease (COVID)-19 pandemic, best practice for mechanical ventilation in COVID-19 associated Acute Respiratory Distress Syndrome (ARDS) is intensely debated. Specifically, the rationale for high positive end-expiratory pressure (PEEP) and prone positioning in early COVID-19 ARDS has been questioned.
The first 23 consecutive patients with COVID-19 associated respiratory failure transferred to a single ICU were assessed. Eight were excluded: five were not invasively ventilated and three received veno-venous ECMO support. The remaining 15 were assessed over the first 15 days of mechanical ventilation. Best PEEP was defined by maximal oxygenation and was determined by structured decremental PEEP trials comprising the monitoring of oxygenation, airway pressures and trans-pulmonary pressures. In nine patients the impact of prone positioning on oxygenation was investigated. Additionally, the effects of high PEEP and prone positioning on pulmonary opacities in serial chest x-rays were determined by applying a semiquantitative scoring-system. This investigation is part of the prospective observational PA-COVID-19 study.
Patients responded to initiation of invasive high PEEP ventilation with markedly improved oxygenation, which was accompanied by reduced pulmonary opacities within 6 h of mechanical ventilation. Decremental PEEP trials confirmed the need for high PEEP (17.9 (SD ± 3.9) mbar) for optimal oxygenation, while driving pressures remained low. Prone positioning substantially increased oxygenation (p<0.01).
In early COVID-19 ARDS, substantial PEEP values were required for optimizing oxygenation. Pulmonary opacities resolved during mechanical ventilation with high PEEP suggesting recruitment of lung volume.
German Research Foundation, German Federal Ministry of Education and Research.
Initial emergency department mechanical ventilation strategies for COVID-19 hypoxemic respiratory failure and ARDS
2020, American Journal of Emergency Medicine
Citation Excerpt :
This position, commonly referred to as “proning,” utilizes gravitational effects to conform the shape of the lung to the chest cavity and ultimately reduce the pleural pressure gradient from non-dependent to dependent regions [62]. In addition to a more favorable and equitable distribution of aeration, proning increases end-expiratory lung volume, improves ventilation-perfusion matching, increases secretion clearance, and alters chest wall mechanics, leading to regional changes and improvements in overall lung ventilation [61,63-65]. Prone positioning has been shown in several studies to protect against VILI [62,66-69] and also has a mortality benefit [60,70,71].
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an emerging viral pathogen that causes the novel coronavirus disease of 2019 (COVID-19) and may result in hypoxemic respiratory failure necessitating invasive mechanical ventilation in the most severe cases.
This narrative review provides evidence-based recommendations for the treatment of COVID-19 related respiratory failure requiring invasive mechanical ventilation.
In severe cases, COVID-19 leads to hypoxemic respiratory failure that may meet criteria for acute respiratory distress syndrome (ARDS). The mainstay of treatment for ARDS includes a lung protective ventilation strategy with low tidal volumes (4–8 mL/kg predicted body weight), adequate positive end-expiratory pressure (PEEP), and maintaining a plateau pressure of < 30 cm H₂O. While further COVID-19 specific studies are needed, current management should focus on supportive care, preventing further lung injury from mechanical ventilation, and treating the underlying cause.
This review provides evidence-based recommendations for the treatment of COVID-19 related respiratory failure requiring invasive mechanical ventilation.
Prone positioning for patients with hypoxic respiratory failure related to COVID-19
2020, CMAJ
Citation Excerpt :
The position also enhances the inferior movement of the diaphragm, which relieves compression on atelectatic posterior lung zones, increasing lung recruitability.10,11 Prone positioning has relatively little effect on a patient’s lung perfusion, however, as most blood flow is directed to posterior lung zones while both supine and prone.9 The result is improved V/Q matching, a decrease in the shunt fraction and improved oxygenation.
Effectiveness and safety of awake prone positioning in COVID-19-related acute hypoxaemic respiratory failure: an overview of systematic reviews
2024, BMC Pulmonary Medicine

View all citing articles on Scopus

: This study was supported by grants DFG-Fa 139/1-3 und 2-3

View full text

Chest

Clinical Investigations in Critical CareInfluence of Positioning on Ventilation-Perfusion Relationships in Severe Adult Respiratory Distress Syndrome

Section snippets

Study Population

Results

Discussion

ACKNOWLEDGMENT

Chest

J Crit Care

Comments of a devil's advocate.

Am Rev Respir Dis

Use of extreme position changes in acute respiratory failure.

Crit Care Med

Improved oxygenation in patients with acute respiratory failure: the prone position.

Am Rev Respir Dis

Body position changes redistribute lung computed-tomographic density in patients with acute respiratory failure.

Anesthesiology

An expanded definition of the adult respiratory distress syndrome [published erratum appears in Am Rev Respir Dis 1988; 139:1065].

Am Rev Respir Dis

Measurement of continuous distribution of ventilation-perfusion ratios: theory.

J Appl Physiol

Simultaneous measurement of eight foreign gases in blood by chromatography.

J Appl Physiol

Ventilation-perfusion relationships during halothane anaesthesia and mechanical ventilation: effects of varying inspired oxygen concentration.

Acta Anaesthesiol Scand

Clinical Investigations in Critical Care
Influence of Positioning on Ventilation-Perfusion Relationships in Severe Adult Respiratory Distress Syndrome