TYPES OF RESPIRATORY FAILURE:

·       Type 1- hypoxemic respiratory failure (oxygenation defect)

-      hypoxemia with PaO2 <60 mm Hg on room air

-      eg. ARDS, Atelectasis, Pneumonia, ILD, Pulmonary oedema, Pulmonary embolism

·       Type 2- hypercapnic respiratory failure (ventilatory defect)

-      hypercarbia with PaCO2 > 50 mm Hg on room air

-      eg. COPD, Asthma, CNS depression, Neurological disease, Obesity hypoventilation syndrome

·       Type 3- Postoperative

-      Eg. Thoraco-abdominal surgery, Inadequate analgesia postoperatively, Obesity, Diaphragmatic dysfunction

·       Type 4- Increased metabolic demand

-      Eg. Shock (septic, hypovolemic, cardiogenic)

-      Hypermetabolic states

Approach to respiratory failure:

·       A careful history

·       Detailed examination of

-  the chest and upper airway

-  cardiovascular

-  neurologic

-  abdominal,

-skin and

-musculoskeletal system

·       Pulse oximetry

·       ABG to be done in all patients with respiratory distress

·       Laboratory investigations

-        Complete blood count

-        Serum electrolytes

-        KFT

-        Cardiac enzymes

-        Microbiological evaluation

·       CXR

·       CT Chest

·       Echocardiography

·       Rapid Ultrasound for shock and hypotension (RUSH) recommended in rapid bedside evaluation of patients with ARF

Basic goals in management of Acute Respiratory Failure:

·       To maintain airway, breathing, circulation

·       To ensure adequate alveolar oxygenation and ventilation

·       Treatment of the primary cause

All patients to be assessed for the following:

·       Airway

-        First priority in any patient with poor sensorium is to secure the airways by clearing secretions, maintaining airway patency via oropharyngeal or nasopharyngeal airway, and endotracheal intubation in the worst scenario

·       Breathing

-        Once airway is secured the patient should be assessed for breathing

-        If breathing is inadequate administer oxygen supplementation and assisted ventilation

·       Circulation

-        An intravenous access to be secured

-        Intravenous fluids to be administered with the goal to restore normal volume status

·       Oxygenation

-        Patients with ARF to be monitored closely using pulse oximetry with target SpO2 above 90%

Oxygen supplementation can be done by the following oxygen delivery system: -

1.     Nasal cannula:

o   in patients who are hypoxemic without significant increased work of breathing and

o   require low to moderate FiO2 to achieve oxygenation goals.

2.     Simple face mask:

o   for patients who are hypoxemic without significant increased work of breathing and requiring low to moderate FiO2 to achieve oxygenation goals.

o   May be a better option than nasal cannula in patients with nasal obstruction or epistaxis.

3.     Face mask with reservoir (non-rebreather):

o   for patients who are hypoxemic with high inspiratory flow requirements.

o   The reservoir bag should be at least half distended throughout respiration

4.     Venturi masks:

o   Are high-flow, fixed oxygen concentration devices

o   Can control the amount of air entrained to deliver a fixed FiO2 from 24 to 60%

o   Useful in COPD patients to titrate FiO2 without increasing the PaCO2 concentration

o   Relatively high flows of 100% O2 are required to achieve high FiO2.

5.     High-flow nasal cannula (HFNC):

o   Basic components include a flow generator providing gas flow rates up to 60 liters per minute, an air-oxygen blender that achieves escalation of FIO2 from 21% to 100% irrespective of flow rates, and a humidifier that saturates the gas mixture at a temperature of 31 to 37 C. To minimize condensation, the heated humidified gas is delivered via heated tubings through a wide-bore nasal prong.

o   Indicated in

-        Acute hypoxemic respiratory failure

-        Post-surgical respiratory failure

-        Acute heart failure/pulmonary edema

-        Hypercapnic respiratory failure, COPD

-        Pre and post-extubation oxygenation

-        Obstructive sleep apnea

-        Use in the emergency department

-        Do not intubate the patient

6.     Non-invasive ventilation (NIV):

o   Non-invasive ventilation should be applied simultaneously to a patient in acute respiratory failure in addition to the rest of the treatment based on the clinical criteria, provided there is no contraindication

o   Non-invasive Positive Pressure Ventilation (NIPPV) is indicated in patients with appropriate diagnosis with potential reversibility and if patient any two of the following clinical criteria are fulfilled-

-     Moderate to severe respiratory distress

·   Tachypnoea (RR more than 25 / min)

·   Accessory muscle use or abdominal paradox

·   Blood gas derangement pH < 7.35, PaCO2 > 45 mm Hg

·   PaO2/FiO2<300 or SPO2<92% with FiO2 0.5

Indications for NIV:

·       Acute COPD with exacerbations

·       Acute cardiogenic pulmonary oedema

·       Obesity hypoventilation syndrome

·       Weaning and post-extubation respiratory failure

·       Mild ARDS

Contraindications to NIV:

·       Cardiac or respiratory arrest

·       Haemodynamic instability-patient on high vasopressor support

·       Inability to protect airways or clear secretions

·       Facial deformity, surgery

·       High risk of aspiration-cerebrovascular accident (CVA)

·       Recent oesophageal surgery

·       Unco-operative patient

7.     Invasive Mechanical Ventilation:

·       All patients on NIV support should be closely monitored for sudden deterioration

·       If not much improvement in gas exchange or relief in respiratory distress within a few hours invasive mode of ventilation to be started without delay

·       Indications for endotracheal intubation in patients requiring invasive mechanical ventilation-

§  Impending cardio-respiratory arrest

§  Tachypnoea with signs of respiratory distress, use of accessory muscle

§  NIV failure/noncompliance

§  Severe refractory acidosis

§  Unable to protect airway/clear secretions

§  Hypoventilation with reduced ventilatory rate

§  Poor sensorium with GCS <8

§  Polytrauma

8.     Tracheostomy: Indications for tracheostomy-

 ·       Long term mechanical ventilation

·       Weaning failure

·       Upper airway obstruction

·       Airway protection

Ventilatory management for ARDS/ALI:

·       Patients with ARDS to be ventilated using lung protective mechanism with low Vt (6ml/kg of ideal body weight)

·       Permissive hypercapnia

·       Optimum positive end expiratory pressure (PEEP)

·       Maintenance of plateau pressures <30 cmH2O

·       Neuromuscular blockade, in spite of high level of sedation, may be required in severe ARDS to overcome desynchrony

·       Prone positioning

Intensive Care Unit Ventilator Weaning Protocol: -

No or minimal vasopressor or inotrope (< 5 µg/kg/minute dopamine or dobutamine)

Adequate oxygenation:

·       Tidal volume > 5 mL/kg

·       Vital capacity >10 mL/kg

·       Proper inspiratory effort

·       Respiratory rate ≤ 35/minute

·       PaO2 ≥ 60 and PaCO2 ≤ 60 mmHg

·       Positive end expiratory pressure ≤ 8 cmH2O

·       No significant respiratory acidosis (pH ≥ 7.30)

·       Maximal inspiratory pressure (MIP) ≤ -20 – -25 cmH2O

·       O2 saturation > 90% on FIO2 ≤ 0.4 (or PaO2/FIO2 ≥ 200)

·       Rapid Shallow Breathing Index (respiratory Frequency/Tidal Volume) < 105

Weaning procedure:

A weaning plan starts with assessing the ability of the patient for spontaneous breathing.

SBT Strategies-

·       Continuous positive airway pressure (CPAP) trial using a CPAP level equal to the previous positive end-expiratory pressure (PEEP) level followed by

·       T-piece trial, in which only supplemental oxygen is supplied through a T- piece connected to an endotracheal tube.

Criteria of successful spontaneous breathing trials:

Extubation:

·       If patient tolerates Spontaneous Breathing Trial for 2 h and

·       All the above criteria are fulfilled patient is extubated

·       If any of the criteria mentioned above is not satisfied mechanical ventilation is continued and items in the checklist are re-checked the next day.

Supportive care:

1.      Suctioning:

·       Maintains airway patency

·       Increases oxygenation and decreases work of breathing

·       Stimulates cough and prevents atelectasis.

2.      Nebulisation:

·       Inline jet nebulizer / MDI

·       Delivery of bronchodilator drugs in aerosolised form.

3.      Humidification: Prevents drying of secretions and maintains mucociliary function.

4.      Physiotherapy: Prevents atelectasis, facilitates postural drainage, and prevents complication of mechanical ventilation.

5.      Care of ETT: Proper fixing of the tube, measuring cuff pressure and maintaining it less than 25 mm of Hg.

6.      Nutritional support: early enteral feeding, provide adequate calories, protein, electrolytes, vitamins and fluids, care of feeding tube.

7.      Stress ulcer prevention: Early enteral feeding, H2 blockers or proton pump inhibitors for prophylaxis, minimise use of steroids and NSAIDS

8.      DVT prevention: DVT prevention either by low molecular weight heparin or conventional heparin or by graduated compression stockings or sequential compression device in patient where heparin is contraindicated.

·       Head end elevation of 35-45°.

·       Bowel and bladder care

·       Care of eyes

·       Daily sedation interruption

9.      Prevention of pressure sore: positioning, prevent soiling, use of air mattress, meticulous cleaning and good wound care.

·       Adequate Analgesia for pain

·       Infection control.

·       chest radiographs and arterial blood gas measurement in patients undergoing mechanical ventilation best done when clinically indicated rather than routinely on a daily basis

·       Bedside ultrasound/point of care ultrasound (POCUS) preferred to radiograph.