|Ahead of print publication
Effect of Lateral Positioning on Oxygen Levels in an Obese, Critically Hypoxic COVID-19 Patient
Sanjith Saseedharan1, Shalaka Patil2, Gauri Kene2, Ashish Yadav3, Rujuta Bagade3
1 HOD Critical Care, Critical Care Unit, S.L. Raheja Hospital, India
2 ICU Registrar, Critical Care Unit, S.L. Raheja Hospital, India
3 Repiratory Therapist, Critical Care Unit, S.L. Raheja Hospital, India
|Date of Submission||10-Feb-2022|
|Date of Decision||24-Mar-2022|
|Date of Acceptance||23-May-2022|
|Date of Web Publication||11-Jul-2022|
MD Anaesthesia, ICU Registrar, S.L. Raheja Hospital, Mumbai, Maharashtra
Source of Support: None, Conflict of Interest: None
Abstract COVID-19 is an infectious disease caused by SARS-CoV-2 virus. COVID-19 patients can develop a severe disease that can lead to hypoxic respiratory failure and acute respiratory distress syndrome (ARDS), which requires mechanical ventilation, prone ventilation, and salvage therapy like extracorporeal membrane oxygenation. The COVID lung is a hypoxic lung with myriad of reasons of hypoxia including poor ventilation perfusion mismatch and atelectasis. We present a case report of a morbidly obese individual managed with lateral positioning as a salvage for deteriorating PaO2/FiO2 ratio. We also demonstrated that the improvement of oxygenation was due to the recruitment of previously nonventilated lung areas as demonstrated by electrical impedance tomography (EIT). Our patient was morbidly obese and there was a dearth of man power to perform the prone position on this patient. Moreover, the sheer weight of this patient prevented us from trying the prone position. Hence, this patient was placed in a cycle of left lateral, right lateral, and supine position for 120 minutes each for the subsequent 24 hours. Significant improvement in oxygenation and ventilation was noticed in the EIT and SpO2 measurements. The EIT reading indicated ventilation redistribution to previously collapsed areas of the lung and this change persisted even when the patient was turned supine due the application of positive end expiratory pressure (PEEP) to maintain positive expiratory transpulmonary pressure. These results provide evidence of effectiveness of a lateral positioning in the improvement of oxygenation in COVID-19 ARDS.
Keywords: COVID-19, EIT, intensive care unit, positioning, SARS-CoV-2
|How to cite this URL:|
Saseedharan S, Patil S, Kene G, Yadav A, Bagade R. Effect of Lateral Positioning on Oxygen Levels in an Obese, Critically Hypoxic COVID-19 Patient. MAMC J Med Sci [Epub ahead of print] [cited 2022 Nov 26]. Available from: https://www.mamcjms.in/preprintarticle.asp?id=350635
| Introduction|| |
COVID-19 is an infectious disease caused by SARS-CoV-2 virus. COVID-19 patients can develop a severe disease that can lead to hypoxic respiratory failure and acute respiratory distress syndrome (ARDS). A minority of them require mechanical ventilation, prone ventilation, and salvage therapy like extracorporeal membrane oxygenation. A small number of those ventilated respond to recruitment maneuvers and predominantly a large number of patients require prone ventilation. In a recently published study, 61% of patients (out of 1057 patients) required prone ventilation which resulted in significant improvement in 78% of them as defined as 20 mm improvement in the PaO2/FiO2 ratio. This study also found that the change in body position did not change the respiratory system compliance significantly, suggesting that lung recruitment was not the major mechanism.
Studies in the past have reported proning in obese individuals to be a safe procedure with better improvements in oxygenation as compared to the nonobese individuals., Proning a morbidly obese COVID-19 patient has got its own challenges in the current pandemic because of the manpower shortage (proning morbidly obese individuals would require more manpower than in averagely built individuals), use of heavy personal protective equipment reducing flexibility of those involved and lack of experience in such patients in many centers around the world. However, the use of lateral positioning is feasible, easy to use, and requires lesser manpower. However, there is very less evidence in the use of this position for salvage from hypoxia.
We present a case report of a morbidly obese individual managed with lateral positioning as a salvage for deteriorating PaO2/FiO2 ratio. We also demonstrated that the improvement of oxygenation was due to the recruitment of previously nonventilated lung areas as demonstrated by electrical impedance tomography (EIT).
EIT is noninvasive and can be used at the bedside for real-time evaluation to identify ventilation distribution of infected lungs. It is radiation free, and a dynamic regional ventilation profile can be monitored at the bedside every time the ventilator settings are changed. If the lungs are evenly ventilated by reducing regional overdistension and recruiting the collapsed region, local stress and strain can be ameliorated, resulting in the prevention of ventilator-induced lung injury. The importance of homogeneity of regional ventilation has been increasingly recognized with EIT.
Statement of informed consent: The written consent for submitting the data of the patient for publication was taken from the patient as well as the relative of the patient.
| Case Report|| |
A 64-year-old obese hypertensive male was admitted to the intensive care unit with a diagnosis of critical COVID-19 ARDS with a computed tomography (CT) severity score of 19/25. Due to the failure of the high flow nasal cannula and increasing effort the patient was intubated and ventilated using the Carescape R860 (Carescape R860; GE Healthcare, Chicago, IL, USA) ventilator. As per protocol, the transpulmonary pressure was monitored using an esophageal manometer using the Nutrivent (NutriventTM, Sidam, Italy). End-expiratory lung volume (EELV) or the functional residual capacity (FRC) was measured using the nitrogen washout method. The patient was ventilated with a pressure controlled mode at a FiO2 of 80% of ventilated with the driving pressure (pressure control – PEEP) maintained at 15. The PEEP was progressively increased in steps of five (staircase maneuver). Two minutes were spent at each PEEP setting since most of the changes in the EELV are known to occur in 2 minutes. The staircase recruitment was continued to reach an inspiratory transpulmonary pressure of 25 or a PEEP of 40 (whichever reached earlier). At each step of the staircase maneuver the EELV, compliance, and the EIT values were noted to avoid overdistension. Furthermore, PEEP was set in order to maintain the expiratory transpulmonary pressure of 5 as per the oxygenation management table of the Esophageal Pressure-Guided Ventilation (EPVent) 2 study protocol (as the FiO2 was set at 80%)., There was evidence of increase in the FRC/EELV associated with a reduction in the compliance with no improvement in the oxygenation signifying overdistension ([Table 1]). This was further confirmed by the values seen on the EIT ([Table 2]). This was associated with absence of clinical recruitment (absence of increase in SpO2) even after 12 hours of ventilation and patient continued to show a very high oxygen requirement.
| Positioning|| |
As no significant improvement in oxygenation was observed, decision was taken to prone the patient. However, due to the lack of manpower, the imminent danger of tube dislocation in a patient with difficult airway, and lack of expertise in proning obese individual, it was decided to explore lateral positioning with the hope of improving the oxygenation.
The lateral position is described as side-lying with pillows strategically placed along the patient’s back, and possibly buttocks, and a pillow placed between the patient’s flexed legs to prevent adduction and internal rotation of the hip. Lateral and supine positions were performed (2 hours in lateral and 4 hours in supine position). While patient was in supine position, EIT belt was applied and changes in air distribution were noted. Same procedure was repeated for left lateral position and changes in regional distribution of ventilation were noted.
At each position, an FRC calculation (average of three) was done and an EIT measurement was done. The lung strain was calculated by the formula tidal volume/FRC and was found to be <0.25 at all times.
We studied the evolution in SpO2, variations in regional distribution of ventilation (TV) and changes in EELV/FRC. There was no hemodynamic embarrassment at given moment.
EIT revealed that even if there was increase in the FRC, the apical and dorsal region of the lungs in the EIT had no air distribution which again suggests that it could probably be the overdistension of mid zones of the lungs.
Before assuming the right lateral position, the distribution of air was as per the [Figure 1]a with the corresponding values on the region of interest (ROI) as per [Table 2]. Subsequently, the patient was given a right lateral position for 2 hours later, an EIT reading was observed as shown in [Figure 1]b; the corresponding values of the ROI are shown in the [Table 2]. What was clearly seen is a redistribution of air into the poorly ventilated quadrant from the overventilated quadrants. The poorly ventilated ROI1 (4%) got more distribution of air (10%) post right lateral positioning. The overdistended ROI3 (57%) was also found to have a reduction in the overdistension akin to homogenization of the air distribution. There was also an increase in the SpO2 from 84% to 88%. The patient was then maintained in supine position for 4 hours. Subsequently, an EIT reading was performed and the subsequent values of which are seen in [Table 2]. The redistribution or the homogenization was seen to persist (as seen in [Figure 1]b and [Table 2]) at the end of 4 hours with maintenance of the SpO2 at 88% and reduction in the FiO2 requirements. Subsequently, the patient was shifted to the left lateral position for 2 hours. The patient was made supine after 2 hours and the EIT readings were noted. As seen in [Figure 2]b and the [Table 2] there was a clear distribution of air into ROI4 (12%) which was initially underventilated (7%). Importantly, there was an improvement in oxygenation with reduction in oxygen requirement (SpO2 on FiO2 of 60%). During this entire period, the ventilation parameters (mode, tidal volume, PEEP, respiratory rate, and I:E ratio) were not changed. The absence of significant change in the measured FRC/EELV indicates that the change in the SpO2 was probably due to redistribution of air into those lung regions which were not participating in gas exchange. These findings suggest recruitment of previously nonventilated/poorly ventilated lung areas.
|Figure 1 Position: (a) before right lateral and (b) after right lateral.|
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| Discussion|| |
The COVID lung is a hypoxic lung with myriad of reasons of hypoxia including poor ventilation perfusion mismatch and atelectasis. Chest physiotherapy and recruitment maneuvers are two methods that improve respiratory efficiency, reinflate collapsed regions, promote lung mechanics, reduce occurrence of pulmonary complications, and improve oxygenation. However, the absence of robust data that shows clear improvement of mortality with recruitment maneuvers and the sheer danger of causing injury to the lungs (without the use of guidance like esophageal manometry, EIT, etc.) and hemodynamics makes us wary of their use. Lateral positioning is used in routine critical care. But this is more for the prevention of bedsores. Very few studies have shown improvement in oxygenation in the lateral positions. Many other studies have not found any significant alteration in oxygenation parameters., What is known is that in patients with unilateral lung disease, PaO2 increases with the unaffected lung in the dependent position., However, frequent lateral positioning may help in tracheobronchial drainage, mobilization of the secretions, increased sputum volume production, and prevention of pooling of secretions., Frequent turning is also known to recruit previously collapsed alveoli and hence could potentially lead to an improvement in oxygenation. There are no large robust studies that have compared the lateral position to supine position and the improvement of oxygenation seen thereafter. Hence, when placed in a situation where the harms with a prone positioning for salvage from hypoxia (for example, in morbidly obese patient like ours) is more than the benefits, it is important to look for other means to improve oxygenation. However, there is a dearth of evidence in this regard. The use of EIT would provide information on the regional overdistension and collapse., What is known is that the transpulmonary pressure would be highest in the nondependent area of the lung as compared to the dependent area and this gradient would be more than that seen in anterior to posterior region in the supine position. Also, the distribution of ventilation becomes more homogeneous when PEEP is applied. Hence, the higher lung now gets subjected to a higher transpulmonary pressure as compared to the supine position with a lower mean airway pressure when compared to the supine position due the gravity gradient effect. This would lead to a slow and safe recruitment of the lung which would then remain open due to the presence of PEEP. When the nondependent lung becomes dependent, the PEEP prevents the collapse while the same process of slow safe recruitment would occur with the previously dependent lung that has now become nondependent. Thus, such positional alteration or positional recruitment maneuver can reverse atelectasis without subjecting the patient to a high-pressure recruitment maneuver. This form of positional recruitment was demonstrated in children with healthy lungs. One of the major drivers of hypoxemia in COVID-19 lungs seems to be atelectasis. Increasing atelectasis makes it more and more difficult to open up the lungs, causing extreme distortion of architecture followed by biotrauma as a results of ‘stress raisers’ between normal alveoli and collapsed alveoli. Positional alterations like prone positioning might help in opening up the lungs in such cases. However, there are many patients (for example, morbidly obese patient, recent abdominal surgery, abdominal wall tumors, requirement of vasopressors) in which prone position may become difficult to perform or at times harmful. At such times, we could still resort to give alternating lateral positions on a regular interval which would help in ‘gentle’ recruitment and thus serve as a salvage from hypoxia.
Our patient was morbidly obese and there was a dearth of manpower to perform the prone position on this patient. Moreover, the sheer weight of this patient prevented us from trying the prone position. Hence, this patient was placed in a cycle of left lateral, right lateral, and supine position for 120 minutes each for the subsequent 24 hours. Significant improvement in oxygenation and ventilation was noticed in the EIT and SpO2 measurements. As shown in the [Figure 3], the EIT reading indicated ventilation redistribution to previously collapsed areas of the lung and this change persisted even when the patient was turned supine due the application of PEEP to maintain positive expiratory transpulmonary pressure.
|Figure 3 Flowchart showing series of events showing improvement in oxygenations.|
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| Conclusion|| |
These results provide evidence of effectiveness of a lateral positioning in the improvement of oxygenation in COVID-19 ARDS. However, these findings need to be studied in a larger group of individuals to consolidate the findings. This case report would encourage the use of lateral positioning in those hypoxic patients who cannot be proned or in those units who have no expertise in proning.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2]