ards

1. Presented By
Andrea Wahyu

2. Introduction
• Respiratory failure is present whenever the respiratory system fails in the gas exchange function
• ‘hypoxaemic’ when oxygen tension values are lower than normal (PaO2 value is lower than the
normal for age and altitude)
• ventilatory’ when elimination of carbon dioxide is insufficient (PaCO2 of >45 mmHg)
• The most common causes are COPD exacerbation, asthma, and neuromuscular fatigue, leading to
dyspnoea, tachypnoea, tachycardia, use of accessory muscles of respiration, and altered
consciousness
• History taking and ABG analysis are the easiest ways to assess the nature of ARF, and treatment
should resolve the baseline pathology. In severe cases, mechanical ventilation is necessary as a
‘buying time’ therapy

3. • Acute hypoxaemic respiratory failure arising from widespread diffuse injury to the alveolar– capillary
membrane is termed acute respiratory distress syndrome (ARDS), which is the clinical and
radiographic manifestation of acute pulmonary inflammatory states

4. Respiratory failure

5. Diagnosis
• Blood gases
• The PaO2 and PaCO2 values obtained by blood gas analysis give immediate information for the
diagnosis and determination of the ‘nature’ (oxygenation or ventilatory) of respiratory failure.

6. Imaging
• CXR is one of the simplest examinations used to assess the cardiopulmonary status of patients.
detect pulmonary infiltrates, pneumothorax, and pleural effusions.
• CT scans allows a complete examination of the lung parenchyma, and quantitative analysis makes
it possible to determine the degree of aeration of each lung region such as localized pneumothorax,
pleural effusions, and bronchial and tracheal alterations, not shown on X- rays
• PET can quantify regional perfusion, ventilation, aeration, lung vascular permeability, oedema,
inflammatory cell and enzyme activity, and pulmonary gene expression
• Lung US is a bedside tool to assess the state of aeration and ventilation of the lung, the presence of
heterogeneity, and the temporal evolution of pathologies
• EIT monitors lung heterogeneities, the effects of ventilatory manoeuvres, and the physiological
effects of PEEP and tidal volume.

7. Haemodynamics
• Cardiac output and pulmonary wedge pressure may provide important informationfor diagnosis
• PACs or CVCs allow precise monitoring of the volaemic status, cardiac function, and the
haemodynamic effects of mechanical ventilation  Central venous saturation (SvO2)
• Bedside echocardiography has become useful for the management of critically ill patients and as a
non- invasive diagnostic and monitoring tool for circulatory and respiratory failure  fluid
responsiveness, haemodynamic management

8. Treatment of respiratory failure
• The treatment of respiratory failure includes therapies, with three different targets, namely:
1. ‘Symptoms’: with the aim of correcting the consequences of the underlying pathology causing
respiratory failure. This kind of therapy is very important when the consequences, e.g. hypoxaemia,
are life- threatening.
2. ‘Pathogenesis’: with the aim of interrupting the primary insult and clinical consequences, e.g.
corticosteroid administration.
3. ‘Aetiology’: with the aim of correcting the underlying pathology, e.g. antimicrobial administration to
treat bacterial pneumonia or surgery in the case of abdominal disease.
• treatments devoted to correct symptoms, as they allow the buying of time while awaiting resolution
of the underlying pathology

9. Acute respiratory distress syndrome
• Definition
• ‘The clinical pattern . . . Includes severe dyspnoea, tachypnoea, cyanosis that is refractory to
oxygen therapy, loss of lung compliance, and a diffuse alveolar infiltrate seen on chest X- ray (The
lancet, 1967)
• ARDS definition revolved around a combination of the presence of hypoxaemia (PaO2, FiO2),
radiographic infiltrates, low compliance, and wedge pressure - 1988
• In 1988, Murray et al. [31] proposed an approach based on the ‘lung injury score’ (LIS)
1. Chest roentgenogram.
2. Hypoxaemia (PaO2/ FiO2 ratio).
3. PEEP (when ventilated).
4. Respiratory system compliance.
Three levels of severity of lung injury are defined: (1) absence of ung injury (LIS = 0); (2) mild to moderate lung
injury (LIS = 0.1–2.5); and (3) severe lung injury (ARDS) (LIS >2.5).

11. Risk factors

12. Pathophysiology
• pulmonary or extrapulmonary origin, causes a generalized inflammatory response involving the
whole lung clinical and radiographic manifestation
• The process begins with the local production of cytokines by inflammatory cells, epithelial cells, and
fibroblast
• The progression of the lung injury has been divided into three phases: (1) exudative; (2)
proliferative; and (3) fibrotic.ts, which increases the alveolar– capillary barrier permeability.

13. Inflammatory pulmonary oedema
• CT images of the lung during the early phase of ARDS are characterized by three vertically
distributed compartments: the non- dependent regions, which are usually normally aerated; the
middle lung, characterized by ground- glass opacification; and the almost consolidated dependent
regions
• ‘ground- glass opacification’ means an ‘increase in lung attenuation, with preservation of bronchial
and vascular margins’
• Ground- glass opacification reflects an active inflammatory process, involving the interstitium, filling
of the alveolar space, and oedema, which corresponds to poorly aerated tissue
• ‘consolidation’ means a ‘homogeneous increase in lung attenuation that obscures bronchovascular
margins in which an air bronchogram may be present’.

15. Potential for lung recruitment
• the severity of the overall lung injury may be expressed as the ratio of non- aerated lung tissue weight to
total lung weight at end- expiration (5 cmH2O PEEP).
• patients with higher amounts of lung oedema have higher percentages of potential recruitment
• Patients with a higher potential for lung recruitment have, however, higher amounts of collapsed tissue
• CT analysis is the only reliable method to measure the potential for lung recruitment at the bedside
• The best results have been obtained on combining PaO2/FiO2have been obtained on combining PaO2/FiO2
<150 mmHg (at 5 cmH2O PEEP), increased lung compliance, and decreased
dead space from 5 to 15 cmH2O PEEP (sensitivity 79%, specificity
81%)

16. CT: stress, strain, and homogeneity
• Strain is defined as the deformation of lung tissue (tidal volume to
FRC ratio) due to the application of transpulmonary pressure.
• The reactive force rising in the tissue is called stress.
• Lung homogeneity is evaluated by measurement of the strain
difference between contiguous structures
• . The amount of voxels in which this phenomenon may occur (called
‘stress risers’) increases with ARDS severity, while higher PEEP levels
may decrease this phenomenon.

17. Mechanical ventilation
• The goal of mechanical ventilation progressively shifted to the
improvement of gas exchange to avoid lung damage.
• Non-invasive support is considered for mild ARDS patients. However, it can
be extended to selected moderate ARDS patients (i.e. cognizant younger
patients, patients with a SAPS II score of <34 and patient with ARDS not
caused by Pneumonia
• Suggested markers for intubation are excessive transpulmonary pressure
swings, a rapid shallow breathing index higher than 105 breaths/min/L, and
monitored tidal volumes persistently >9.5 mL/kg of predicted body weight.
• CPAP delivered via a face mask has been associated with early
improvement of oxygenation, but it was not associated with a reduction of
intubation need or improved outcome

18. • In a recent trial, the intubation rate was significantly lower with high-
flow nasal cannula (HFNC) O2, compared to standard O2 or NIV, in
patients with PaO2/FiO2 ≤200 mmHg at enrolment.
• HFNC can generate low levels of PEEP in the upper airways, decrease
work of breathing, and reduce dead space

19. Invasive ventilation
• The setting of ventilator parameters involves the respiratory rate, VT, I:E ratio, and pressure.
• Studies showed improved arterial oxygenation at the cost of increased mean airway pressure and
intrinsic PEEP and decreased cardiac output
• In ALI/ARDS, extreme forms of manipulating the I:E ratio are not recommended; values between
0.5 and 1.5 are acceptable
• during spontaneous breathing, high respiratory rates increase oedema formation
• High-frequency oscillatory ventilation (HFOV) has been proposed as an alternative technique to
provide mechanical ventilation, using low VT and very high mean airway pressure, thus improving
oxygenation and minimizing inspiratory overdistension and end-expiratory lung collapse
• A recent meta-analysis suggested that HFOV may be of potential advantage in very severe ARDS
patients (PaO2/FiO2 <70 mmHg)
• The scientific community agrees on the use of low VT, as it provides less injury to the lung. The
debate is still open, however, on an adequate PEEP setting

20. Tidal volume and plateau pressure
• In clinical practice, VT is normalized on the patient’s predicted body
weight (PBW) from the patient’s height (VT/PBW) to avoid excessive
strain on the lung parenchyma
• VT values in the 6–12 mL/kg range
• tidal volume should be scaled to compliance using driving pressure
(∆P = Pplat – PEEP

21. Positive end-expiratory pressure
• It is still not clear what the best way is to set an adequate PEEP level
• Several methods have been proposed, according to lung mechanics, pressure–volume curve, and
hysteresis.
• in the ExPress trial, severe patients were defined according to PaO2 of 80% for at least 1 hour.
• the mortality rate in the high PEEP group is lower than that in the low PEEP group
• It sounds reasonable that high PEEP is effective in the most severe patients, characterized by
smaller baby lung and higher potential for lung recruitment
• , in patients with mild and moderate ARDS, higher PEEP seemed harmful.
• in patients with moderate to severe ARDS, high PEEP levels [16.4 cmH2O (16.0–16.7) at 1 hour;
11.6 cmH2O (11.2– 12.1) at 7 days] may carry more negative (barotrauma) than positive effects
• Intermediate levels, as the ones reported in the control groups of this trial [13.0 cmH2O (12.7–
13.3) at 1 hour; 9.6 cmH2O (9.3–10.0) at 7 days], may prevent both barotrauma and atelectasis

22. Prone position
• The prone position is suggested for ALI/ARDS patients in whom mechanical
ventilation has potentially injurious effects.
• the prone position has been proven and other physiological mechanisms have
been postulated: improvement of V/Q mismatch; recruitment of the most
dependent areas; shunt reduction; and less lung compression by the heart.
• prone positioning is able to prevent or delay the development of VILI
• A recent clinical RCT by Guerin et al. tested the effects of prone positioning on
mortality in patients with severe and persistent ARDS
• survival benefit in patients treated with the prone position, with a reduction in
mortality of nearly 50%
• Contraindications to prone positioning include the presence of an open
abdominal wound, unstable pelvic fracture, spinal lesions and instability, and
brain injury without monitoring of ICP. In addition, well-trained staff are required
for its safe implementation.

23. Artificial lungs
• If the aim is to treat life-threatening hypoxaemia, the indication is
high-flow veno-venous ECMO if the patient does not present with
severe car
• According to the Italian ECMOnet experience, intracranial
haemorrhage occurred in one patient out of 49.
• the SUPERNOVA study showed the possibility to reduce the intensity
of mechanical ventilation, but with a high and partially unexpected
risk of coagulation

24. Overall management of acute lung
injury/acute respiratory distress syndrome
• Prophylaxis for PE and venous thrombosis should be applied in all patients,
unless contraindicated
• Enteral nutrition is also important to prevent GI bleeding and to maintain
the normal barrier function of the mucosa
• Tight glycaemic control has been proven to reduce the number of multiple
organ failure in a population of post-operative patients treated with
intensive insulin, thus also improving ICU and hospital outc
• prevention of nosocomial or secondary infections and VAP, which are
responsible for the high mortality rate in ALI/ARDS patients
• the routine use of corticosteroids is not recommended in patients with
persistent ARDS