scholarly journals Lung histopathologic clusters in severe COVID-19: a link between clinical picture and tissue damage

Critical Care ◽  
2021 ◽  
Vol 25 (1) ◽  
Author(s):  
Maddalena Alessandra Wu ◽  
Gianluca Lopez ◽  
Manuela Nebuloni ◽  
Davide Ottolina ◽  
Jonathan Montomoli ◽  
...  
Keyword(s):  
Clinical Data ◽  
Tissue Damage ◽  
Clinical Picture ◽  
Positive Pressure Ventilation ◽  
Diffuse Alveolar Damage ◽  
Northern Italy ◽  
Positive Pressure ◽  
Positive End Expiratory Pressure ◽  
Lung Histopathology ◽  
Histopathologic Findings

Abstract Background Autoptic pulmonary findings have been described in severe COVID-19 patients, but evidence regarding the correlation between clinical picture and lung histopathologic patterns is still weak. Methods This was a retrospective cohort observational study conducted at the referral center for infectious diseases in northern Italy. Full lung autoptic findings and clinical data of patients who died from COVID-19 were analyzed. Lung histopathologic patterns were scored according to the extent of tissue damage. To consider coexisting histopathologic patterns, hierarchical clustering of histopathologic findings was applied. Results Whole pulmonary examination was available in 75 out of 92 full autopsies. Forty-eight hospitalized patients (64%), 44 from ICU and four from the medical ward, had complete clinical data. The histopathologic patterns had a time-dependent distribution with considerable overlap among patterns. Duration of positive-pressure ventilation (p < 0.0001), mean positive end-expiratory pressure (PEEP) (p = 0.007), worst serum albumin (p = 0.017), interleukin 6 (p = 0.047), and kidney SOFA (p = 0.001) differed among histopathologic clusters. The amount of PEEP for long-lasting ventilatory treatment was associated with the cluster showing the largest areas of early and late proliferative diffuse alveolar damage. No pharmacologic interventions or comorbidities affected the lung histopathology. Conclusions Our study draws a comprehensive link between the clinical and pulmonary histopathologic findings in a large cohort of COVID-19 patients. These results highlight that the positive end-expiratory pressures and the duration of the ventilatory treatment correlate with lung histopathologic patterns, providing new clues to the knowledge of the pathophysiology of severe SARS-CoV-2 pneumonia.

Effects of positive end-expiratory pressure on the right ventricle

1986 ◽  
Vol 61 (3) ◽  
pp. 819-826 ◽  
Author(s):  
R. J. Henning
Keyword(s):  
Stroke Volume ◽  
Right Ventricular ◽  
Positive Pressure Ventilation ◽  
Ventricular Volume ◽  
Positive Pressure ◽  
Right Ventricular Volume ◽  
Positive End Expiratory Pressure ◽  
Lung Water ◽  
Fluid Infusion ◽  
Lung Water Content

Transmural cardiac pressures, stroke volume, right ventricular volume, and lung water content were measured in normal dogs and in dogs with oleic acid-induced pulmonary edema (PE) maintained on positive-pressure ventilation. Measurements were performed prior to and following application of 20 cmH2O positive end-expiratory pressure (PEEP). Colloid fluid was given during PEEP for ventricular volume expansion before and after the oleic acid administration. PEEP significantly increased pleural pressure and pulmonary vascular resistance but decreased right ventricular volume, stroke volume, and mean arterial pressure in both normal and PE dogs. Although the fluid infusion during PEEP raised right ventricular diastolic volumes to the pre-PEEP level, the stroke volumes did not significantly increase in either normal dogs or the PE dogs. The fluid infusion, however, significantly increased the lung water content in the PE dogs. Following discontinuation of PEEP, mean arterial pressure, cardiac output, and stroke volume significantly increased, and heart rate did not change. The failure of the stroke volume to increase despite significant right ventricular volume augmentation during PEEP indicates that positive-pressure ventilation with 20 cmH2O PEEP decreases right ventricular function.

Combination of constant-flow and continuous positive-pressure ventilation in canine pulmonary edema

1989 ◽  
Vol 67 (2) ◽  
pp. 817-823 ◽  
Author(s):  
J. I. Sznajder ◽  
C. J. Becker ◽  
G. P. Crawford ◽  
L. D. Wood
Keyword(s):  
Pulmonary Edema ◽  
Positive Pressure Ventilation ◽  
Alveolar Ventilation ◽  
Positive Pressure ◽  
Constant Flow ◽  
Positive End Expiratory Pressure ◽  
Ventilatory Mode ◽  
Continuous Positive Pressure ◽  
Bronchoscopic Guidance ◽  
Normal Lungs

Constant-flow ventilation (CFV) maintains alveolar ventilation without tidal excursion in dogs with normal lungs, but this ventilatory mode requires high CFV and bronchoscopic guidance for effective subcarinal placement of two inflow catheters. We designed a circuit that combines CFV with continuous positive-pressure ventilation (CPPV; CFV-CPPV), which negates the need for bronchoscopic positioning of CFV cannula, and tested this system in seven dogs having oleic acid-induced pulmonary edema. Addition of positive end-expiratory pressure (PEEP, 10 cmH2O) reduced venous admixture from 44 +/- 17 to 10.4 +/- 5.4% and kept arterial CO2 tension (PaCO2) normal. With the innovative CFV-CPPV circuit at the same PEEP and respiratory rate (RR), we were able to reduce tidal volume (VT) from 437 +/- 28 to 184 +/- 18 ml (P less than 0.001) and elastic end-inspiratory pressures (PEI) from 25.6 +/- 4.6 to 17.7 +/- 2.8 cmH2O (P less than 0.001) without adverse effects on cardiac output or pulmonary exchange of O2 or CO2; indeed, PaCO2 remained at 35 +/- 4 Torr even though CFV was delivered above the carina and at lower (1.6 l.kg-1.min-1) flows than usually required to maintain eucapnia during CFV alone. At the same PEEP and RR, reduction of VT in the CPPV mode without CFV resulted in CO2 retention (PaCO2 59 +/- 8 Torr). We conclude that CFV-CPPV allows CFV to effectively mix alveolar and dead spaces by a small bulk flow bypassing the zone of increased resistance to gas mixing, thereby allowing reduction of the CFV rate, VT, and PEI for adequate gas exchange.

Effects of continuous positive-pressure ventilation in experimental pulmonary edema

1976 ◽  
Vol 40 (4) ◽  
pp. 568-574 ◽  
Author(s):  
P. C. Hopewell ◽  
J. F. Murray
Keyword(s):  
Pulmonary Edema ◽  
Left Atrial ◽  
Positive Pressure Ventilation ◽  
Colloid Osmotic Pressure ◽  
Intermittent Positive Pressure Ventilation ◽  
Water Volume ◽  
Positive Pressure ◽  
Positive End Expiratory Pressure ◽  
Continuous Positive Pressure ◽  
Double Isotope

We compared the effects of continuous positive-pressure ventilation (CPPV), using 10 cmH2O positive end-expiratory pressure (PEEP), with intermittent positive-pressure ventilation (IPPV), on pulmonary extravascular water volume (PEWV) and lung function in dogs with pulmonary edema caused by elevated left atrial pressure and decreased colloid osmotic pressure. The PEWV was measured by gravimetric and double-isotope indicator dilution methods. Animals with high (22–33 mmHg), moderately elevated (12–20 mmHg), and normal (3–11 mmHg) left atrial pressures (Pla) were studied. The PEWV by both methods was significantly increased in the high and moderate Pla groups, the former greater than the latter (P less than 0.05). There was no difference in the PEWV between animals receiving CPPV and those receiving IPPV in both the high and moderately elevated Pla groups. However, in animals with high Pla, the Pao2 was significantly better maintained and the inflation pressure required to deliver a tidal volume of 12 ml/kg was significantly less with the use of CPPV than with IPPV. We conclude that in pulmonary edema associated with high Pla, PEEP does not reduce PEWV but does improve pulmonary function.

scholarly journals Bronchoscopic Insufflation of Room Air for the Treatment of Lobar Atelectasis in Mechanically Ventilated Patients

1995 ◽  
Vol 23 (2) ◽  
pp. 175-177 ◽  
Author(s):  
P. V. Van Heerden ◽  
W. Jacob ◽  
P. D. Cameron ◽  
S. Webb
Keyword(s):  
Positive Pressure Ventilation ◽  
Chest Physiotherapy ◽  
Additional Benefit ◽  
Positive Pressure ◽  
Common Occurrence ◽  
Positive End Expiratory Pressure ◽  
Pulmonary Atelectasis ◽  
Mechanically Ventilated ◽  
Mechanically Ventilated Patients ◽  
Ventilated Patients

Segmental and lobar pulmonary atelectasis is a common occurrence in mechanically ventilated patients. Standard therapy for atelectasis relies on positive pressure ventilation, positive end expiratory pressure (PEEP), tracheobronchial toilet and regular chest physiotherapy. Various adjuncts to physiotherapy such as bronchoscopic clearance of secretions have not proved to be of additional benefit. Bronchoscopic clearance of secretions followed by insufflation of room air at 30 cm H2O into the atelectatic segment was employed on ten occasions in mechanically ventilated patients. Rapid re-expansion of the collapsed segment or lobe occurred in seven out of the ten treatments.

High-frequency oscillation compared with standard ventilation in pulmonary injury model

1982 ◽  
Vol 52 (3) ◽  
pp. 543-548 ◽  
Author(s):  
W. K. Thompson ◽  
B. E. Marchak ◽  
A. B. Froese ◽  
A. C. Bryan
Keyword(s):  
High Frequency ◽  
Positive Pressure Ventilation ◽  
Arterial Oxygen Tension ◽  
Arterial Oxygen ◽  
High Frequency Oscillation ◽  
Positive Pressure ◽  
Positive End Expiratory Pressure ◽  
Frequency Oscillation ◽  
Arterial Blood ◽  
Airway Pressures

Hemorrhagic pulmonary edema was induced by intra-atrial infusion of 0.04--0.1 ml/kg of oleic acid into six anesthetized dogs. Gas exchange and cardiac outputs were then compared at identical mean airway pressures during randomized ventilation with either a volume-cycled ventilator with positive end-expiratory pressure (conventional positive-pressure ventilation, tidal volume 16--21 ml/kg, frequency 15--20 cycles/min) or a variable volume piston pump operating at 15 Hz (high-frequency oscillation). The fractional inspired oxygen concentration was maintained at 0.5 throughout. During 17 data sets matched for intratracheal mean airway pressures over a range of 7.5--27 cmH2O, measurements of systemic arterial pressure, arterial blood gas tensions, thermodilution cardiac outputs, and pulmonary arterial and capillary wedge pressures were identical (P less than 0.05) during ventilation with conventional positive-pressure ventilation and high-frequency oscillation. With both forms of ventilation, arterial oxygen tension progressively improved as mean airway pressure increased. In a shunt model of acute lung injury we were unable to show significant differences in oxygenation or cardiac output when high-frequency oscillation was compared with conventional positive-pressure ventilation with positive end-expiratory pressure at equivalent mean airway pressures.

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