Project description:ObjectivesProne positioning allows to improve oxygenation and decrease mortality rate in COVID-19-associated acute respiratory distress syndrome (C-ARDS). However, the mechanisms leading to these effects are not fully understood. The aim of this study is to assess the physiologic effects of pronation by the means of CT scan and electrical impedance tomography (EIT).DesignExperimental, physiologic study.SettingPatients were enrolled from October 2020 to March 2021 in an Italian dedicated COVID-19 ICU.PatientsTwenty-one intubated patients with moderate or severe C-ARDS.InterventionsFirst, patients were transported to the CT scan facility, and image acquisition was performed in prone, then supine position. Back to the ICU, gas exchange, respiratory mechanics, and ventilation and perfusion EIT-based analysis were provided toward the end of two 30 minutes steps (e.g., in supine, then prone position).Measurements and main resultsProne position induced recruitment in the dorsal part of the lungs (12.5% ± 8.0%; p < 0.001 from baseline) and derecruitment in the ventral regions (-6.9% ± 5.2%; p < 0.001). These changes led to a global increase in recruitment (6.0% ± 6.7%; p < 0.001). Respiratory system compliance did not change with prone position (45 ± 15 vs 45 ± 18 mL/cm H2O in supine and prone position, respectively; p = 0.957) suggesting a decrease in atelectrauma. This hypothesis was supported by the decrease of a time-impedance curve concavity index designed as a surrogate for atelectrauma (1.41 ± 0.16 vs 1.30 ± 0.16; p = 0.001). Dead space measured by EIT was reduced in the ventral regions of the lungs, and the dead-space/shunt ratio decreased significantly (5.1 [2.3-23.4] vs 4.3 [0.7-6.8]; p = 0.035), showing an improvement in ventilation-perfusion matching.ConclusionsSeveral changes are associated with prone position in C-ARDS: increased lung recruitment, decreased atelectrauma, and improved ventilation-perfusion matching. These physiologic effects may be associated with more protective ventilation.

Project description:Severe hypoxemic respiratory failure is frequently managed with invasive mechanical ventilation with or without prone position (PP). We describe 13 cases of nonhypercapnic acute hypoxemic respiratory failure (AHRF) of varied etiology, who were treated successfully in PP without the need for intubation. Noninvasive ventilation (NIV), high-flow oxygen via nasal cannula, supplementary oxygen with venturi face mask, or nasal cannula were used variedly in these patients. Mechanical ventilatory support is offered to patients with AHRF when other methods, such as NIV and oxygen via high-flow nasal cannula, fail. Invasive mechanical ventilation is fraught with complications which could be immediate, ranging from worsening of hypoxemia, worsening hemodynamics, loss of airway, and even death. Late complications could be ventilator-associated pneumonia, biotrauma, tracheal stenosis, etc. Prone position is known to improve oxygenation and outcome in adult respiratory distress syndrome. We postulated that positioning an unintubated patient with AHRF in PP will improve oxygenation and avoid the need for invasive mechanical ventilation and thereby its complications. Here, we describe a series of 13 patients with hypoxemic respiratory of varied etiology, who were successfully treated in the PP without endotracheal intubation. Two patients (15.4%) had mild, nine (69.2%) had moderate, and two (15.4%) had severe hypoxemia. Oxygenation as assessed by PaO2/FiO2 ratio in supine position was 154 ± 52, which improved to 328 ± 65 after PP. Alveolar to arterial (A-a) O2 gradient improved from a median of 170.5 mm Hg interquartile range (IQR) (127.8, 309.7) in supine position to 49.1 mm Hg IQR (45.0, 56.6) after PP. This improvement in oxygenation took a median of 46 hours, IQR (24, 109). Thus, voluntary PP maneuver improved oxygenation and avoided endotracheal intubation in a select group of patients with hypoxemic respiratory failure. This maneuver may be relevant in the ongoing novel coronavirus disease pandemic by potentially reducing endotracheal intubation and the need for ventilator and therefore better utilization of critical care services.How to cite this articleRao SV, Udhayachandar R, Rao VB, Raju NA, Nesaraj JJJ, Kandasamy S, et al. Voluntary Prone Position for Acute Hypoxemic Respiratory Failure in Unintubated Patients. Indian J Crit Care Med 2020;24(7):557-562.

Project description:BackgroundThe effects of awake prone position on the breathing pattern of hypoxemic patients need to be better understood. We conducted a crossover trial to assess the physiological effects of awake prone position in patients with acute hypoxemic respiratory failure.MethodsFifteen patients with acute hypoxemic respiratory failure and PaO2/FiO2 < 200 mmHg underwent high-flow nasal oxygen for 1 h in supine position and 2 h in prone position, followed by a final 1-h supine phase. At the end of each study phase, the following parameters were measured: arterial blood gases, inspiratory effort (ΔPES), transpulmonary driving pressure (ΔPL), respiratory rate and esophageal pressure simplified pressure-time product per minute (sPTPES) by esophageal manometry, tidal volume (VT), end-expiratory lung impedance (EELI), lung compliance, airway resistance, time constant, dynamic strain (VT/EELI) and pendelluft extent through electrical impedance tomography.ResultsCompared to supine position, prone position increased PaO2/FiO2 (median [Interquartile range] 104 mmHg [76-129] vs. 74 [69-93], p < 0.001), reduced respiratory rate (24 breaths/min [22-26] vs. 27 [26-30], p = 0.05) and increased ΔPES (12 cmH2O [11-13] vs. 9 [8-12], p = 0.04) with similar sPTPES (131 [75-154] cmH2O s min-1 vs. 105 [81-129], p > 0.99) and ΔPL (9 [7-11] cmH2O vs. 8 [5-9], p = 0.17). Airway resistance and time constant were higher in prone vs. supine position (9 cmH2O s arbitrary units-3 [4-11] vs. 6 [4-9], p = 0.05; 0.53 s [0.32-61] vs. 0.40 [0.37-0.44], p = 0.03). Prone position increased EELI (3887 arbitrary units [3414-8547] vs. 1456 [959-2420], p = 0.002) and promoted VT distribution towards dorsal lung regions without affecting VT size and lung compliance: this generated lower dynamic strain (0.21 [0.16-0.24] vs. 0.38 [0.30-0.49], p = 0.004). The magnitude of pendelluft phenomenon was not different between study phases (55% [7-57] of VT in prone vs. 31% [14-55] in supine position, p > 0.99).ConclusionsProne position improves oxygenation, increases EELI and promotes VT distribution towards dependent lung regions without affecting VT size, ΔPL, lung compliance and pendelluft magnitude. Prone position reduces respiratory rate and increases ΔPES because of positional increases in airway resistance and prolonged expiratory time. Because high ΔPES is the main mechanistic determinant of self-inflicted lung injury, caution may be needed in using awake prone position in patients exhibiting intense ΔPES. Clinical trail registeration: The study was registered on clinicaltrials.gov (NCT03095300) on March 29, 2017.

Project description:BackgroundARDS is a heterogeneous syndrome involving different subphenotypes with different clinical features and different responses to treatment strategies. The prone position (PP) is an effective treatment for ARDS; however, whether the effects of prone positioning vary among ARDS patients with different subphenotypes remains unknown.ObjectivesTo evaluated the impact of PP on ventilation-perfusion matching(VQ matching) by contrast-enhanced Electrical impedance tomography (EIT) in ARDS patients with different subphenotypes.MethodsThis was a prospective, observational study at the medical ICU of Zhongda Hospital, Southeast University. ARDS patients undergoing mechanical ventilation were screened and allocated to different subphenotypes based on lung morphology (focal/non-focal) and D-dimer level (low/high D-dimer). EIT was used in the supine position and 3 h, 6 h, and 12 h after the PP during the first PP session.ResultsFrom July 1, 2021, to July 1, 2022, 25 patients were included in this study. 10 patients (40%) were focal ARDS, and 15 were non-focal ARDS based on baseline morphology. 12 patients (48%) were high D-dimer ARDS, and 13 were low D-dimer ARDS based on baseline D-dimer levels. PaO2/FiO2 increased significantly 3 h after prone positioning in focal ARDS patients (130.30[109.94-147.30] vs. 213.50[176.00-256.50] mmHg, p < 0.001), while the effect of improved oxygenation was not apparent until 6 h after prone positioning in non-focal ARDS patients (104.60[95.20-127.00] vs. 190.20[160.10-213.20] mm Hg, p < 0.001). VQ matching improved after 3 h in the prone position in the focal ARDS group (69.93 ± 6.69 vs. 78.22 ± 5.07, p = 0.006) but improved after only 6 h in the prone position in the non-focal ARDS group (67.32 ± 4.78 vs. 78.70 ± 5.93, p < 0.001). In ARDS patients with varying levels of D-dimer, increased PaO2/FiO2 (126.60[99.30-146.20] vs. 185.20[112.10-236.00] mmHg, p = 0.013) and improved VQ matching (67.60 ± 4.60 vs. 72.97 ± 6.48, p = 0.023) were observed at 3 h in the PP in patients with low D-dimer ARDS. In contrast, increased PaO2/FiO2(105.20[95.20-124.10] vs. 195.2[183.20-213.20], p < 0.001) and improved VQ matching (67.19 ± 6.70 vs. 72.50 ± 6.37, p < 0.001) were revealed only after 6 h in the prone position in high D-dimer ARDS patients.ConclusionsFor moderate to severe ARDS patients, non-focal and high D-dimer ARDS patients need longer PP to improve oxygenation and VQmatching than the focal and low D-dimer patients.Clinical trial registrationThis was a prospective, observational study registered in the Chinese Clinical Trial Registry (ChiCTR2200055442, https://www.chictr.org.cn/ ), on June 30, 2021.

Project description:BackgroundProne position has been shown to improve oxygenation and survival in patients with early acute respiratory distress syndrome (ARDS). These beneficial effects are partly mediated by improved ventilation/perfusion (V/Q) distribution. Few studies have investigated the impact of early versus delayed proning on V/Q distribution in patients with ARDS. The aim of this study was to assess the regional ventilation and perfusion distribution in early versus persistent ARDS after prone position.MethodsThis is a prospective, observational study from June 30, 2021, to October 1, 2022 at the medical ICU in Zhongda Hospital, Southeast University. Fifty-seven consecutive adult patients with moderate-to-severe ARDS ventilated in supine and prone position. Electrical impedance tomography was used to study V/Q distribution in the supine position and 12 h after a prone session.ResultsOf the 57 patients, 33 were early ARDS (≤ 7 days) and 24 were persistent ARDS (> 7 days). Oxygenation significantly improved after proning in early ARDS (157 [121, 191] vs. 190 [164, 245] mm Hg, p < 0.001), whereas no significant change was found in persistent ARDS patients (168 [136, 232] vs.177 [155, 232] mm Hg, p = 0.10). Compared to supine position, prone reduced V/Q mismatch in early ARDS (28.7 [24.6, 35.4] vs. 22.8 [20.0, 26.8] %, p < 0.001), but increased V/Q mismatch in persistent ARDS (23.8 [19.8, 28.6] vs. 30.3 [24.5, 33.3] %, p = 0.006). In early ARDS, proning significantly reduced shunt in the dorsal region and dead space in the ventral region. In persistent ARDS, proning increased global shunt. A significant correlation was found between duration of ARDS onset to proning and the change in V/Q distribution (r = 0.54, p < 0.001).ConclusionsProne position significantly reduced V/Q mismatch in patients with early ARDS, while it increased V/Q mismatch in persistent ARDS patients. Trial registration ClinicalTrials.gov (NCT05207267, principal investigator Ling Liu, date of registration 2021.08.20).

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Prone Position and Lung Ventilation and Perfusion Matching in Acute Respiratory Failure due to COVID-19.

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Prone Position and Lung Ventilation and Perfusion Matching in Acute Respiratory Failure due to COVID-19.

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