The Role of Morphological Phenotype in ARDS

Completed

• Conditions: Respiratory Distress Syndrome, Adult
• Interventions: Diagnostic Test: CT

• Registration Number: NCT04157946
• Lead Sponsor: Hospital El Cruce

Brief Summary

Although most of the information focuses on understanding how the ventilator produces lung damage, the pulmonary factors that predispose to ventilator-induced lung injury (VILI) have been less studied. Acute respiratory distress syndrome (ARDS) can adopt different morphological phenotypes, with its own clinical and mechanical characteristics. This morphological phenotypes may favor the development of VILI for same ventilatory strategy

Detailed Description

The lung in acute respiratory distress syndrome ARDS) is a heterogeneous viscoelastic system, in which areas with different time constants coexist, causing tidal volume to be distributed unevenly within an anatomically and functionally reduced lung. The administration of a disproportionately high tidal volume for this lung predisposes to the over-distension of the better ventilated alveoli and to the injury by tidal opening and closing of the alveoli more unstable. In this sense, using low tidal volume and homogenizing the lung by means of the prone position have proven beneficial in ARDS.

Tidal volume, driving pressure, inspiratory flow and respiratory rate have been identified as responsible for mechanical ventilation-induced lung injury (VILI). These factors together represent the mechanical power, the insulting energy which is repeatedly applied to a vulnerable lung parenchyma.

Although most of the information focuses on understanding how the ventilator produces lung damage and/or amplifies the existing one, the pulmonary factors that predispose to VILI have been less studied. Acute respiratory distress syndrome can adopt different morphological phenotypes, with its own clinical and mechanical characteristics. Understanding how each subgroup of ARDS responds to the protective ventilatory strategy could help to personalize treatment.

Objectives: To compare the risk of VILI in two groups of ARDS with different morphological phenotypes (focal and non-focal), ventilated with the same protective strategy.

Design: Patients with ARDS were ventilated under the same conditions of both tidal volume (TV) and plateau pressure (PPlat). Positive End Expiratory Pressure (PEEP) was adjusted to reach 30 cmH2O of PPlat. A CT was performed in inspiration and expiration. Transpulmonary pressures (TP) were measured and lung volumes calculated (Volume Analysis Software,Toshiba, Japan). Stress was defined as TP at the end of inspiration (TPinsp) and strain: tidal volume/End Expiratory Lung Volume Patients were classified into focal and non-focal according to the distribution of aeration loss in CT. Mann - Whitney U test was used to compare variables and Pearson correlation coefficient to compare its correlation. Significant: p \<0.05

Study Timeline

• Study Start: 2017-08-07
• Primary Completion: 2019-07-10
• Study Completion: 2019-07-20
• Status Verified: 2019-11
• Study First Submitted: 2019-11-05
• Study First Submitted QC: 2019-11-06
• Last Update Submitted: 2019-11-06
• Study First Posted: 2019-11-08
• Last Update Posted: 2019-11-08

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 12

Inclusion Criteria

Acute respiratory distress syndrome (ARDS).

Exclusion Criteria

Emphysema Asthma Pneumothorax Oxygen saturation ≤ 88% Severe shock Ventricular arrhythmia Myocardial ischemia.

Study & Design

• Study Type: OBSERVATIONAL
• Study Design: Not specified

Arm && Interventions

Group	Intervention	Description
Focal	CT	ARDS was classified according to the pattern that adopted the loss of aeration in the chest CT in the two groups: focal (predominant commitment in the dependant region) and non- focal (patched or diffused involvement of the entire lung)
Non-Focal	CT	ARDS was classified according to the pattern that adopted the loss of aeration in the chest CT in the two groups: focal (predominant commitment in the dependant region) and non- focal (patched or diffused involvement of the entire lung)

Primary Outcome Measures

Name	Time	Method
Measurement of injury due to cyclic opening and closing of the most unstable caused by mechanical ventilation .	One year	Twelve patients with ARDS were studied (six from each group). Three lung regions were studied on tomography: Basal, middle and apical. A specific software quantified the amount of airless lung (100 to - 100 HU), both in expiration and inspiration. This amount was expressed in numbers of pixels. A lesion due to cyclic opening and closing of the alveoli was defined as the difference between the size of the airless lung between both respiratory times, in relation to the basal condition (lung without air at expiration). This ratio was expressed as a percentage. There is a direct relationship between this mechanism of damage and the risk of VILI. Mann-Whitney U test was used to compare variables. Significant p \< 0.05.
Measuring the level of pulmonary stress caused by mechanical ventilation	One year	Twelve patients with ARDS were studied (six from each group). A balloon catheter was placed at the distal end of the esophagus to measure esophageal pressures. A pneumotachograph was used to record and quantify esophageal pressures during the ventilatory cycle. Esophageal pressure is considered as equivalent of pleural pressure. Pulmonary distention pressure (transpulmonary pressure) is obtained by measuring the difference between the pressure of the respiratory system (supplied by mechanical ventilation) and esophageal pressure. Stress was defined as the transpulmonary pressure measure at the end of an inspiratory pause (in zero flow conditions). Pulmonary stress was quantified in cmH2O. There is a linear relationship between stress and lung damage (VILI). Mann-Whitney U test was used to compare variables. Significant p \< 0.05.
Measurement of pulmonary strain caused by mechanical ventilation	One year	Twelve patients with ARDS were studied (six from each group). A chest tomography was performed during an expiratory and inspiratory pause. Using a specific software (Lung Volume Analysis Software.Toshiba, Japan), the amount of lung volume was calculated in expiration and inspiration air (expressed in ml). The strain was defined as the relationship between the amount of volume supplied by mechanical ventilation (tidal volume) and the lung's ability to receive that volume (EELV: end expiratory lung volume). This ratio was expressed as a percentage. There is a direct relationship between strain and lung damage (VILI). Mann-Whitney U test was used to compare variables. Significant p \< 0.05..

Secondary Outcome Measures

Name	Time	Method
Measurement of pulmonary hyperinflation caused by mechanical ventilation	One year	Twelve patients with ARDS were studied (six from each group). Lung regions were studied on tomography: Basal, middle and apical. A specific software was quantified the amount of excess air (hyperinflation:-900 to - 1000 HU). Hyperinflation was expressed in relation to the total lung volume as a percentage. There is a direct relationship between hyperinflation and the risk of VILI. Mann-Whitney U test was used to compare variables. Significant p \< 0.05.

Trial Locations

Locations (1)

Hospital El Cruce; 🇦🇷 Florencio Varela, Buenos Aires, Argentina