Critical care Guidelines: Acute Respiratory Failure management

Respiratory Failure includes any condition that affects breathing and ultimately results in failure of the lungs to function properly. The main tasks of the lungs and chest are to get oxygen into the bloodstream from air that is inhaled (breathed in) and, at the same to time, to eliminate carbon dioxide (C02) from the bloodstream through air that is exhaled (breathed out). In respiratory failure, either the level of oxygen in the blood becomes dangerously low, and/or the level of C02 becomes dangerously high.

Ministry of Health and Family Welfare has come out with the Standard Treatment Guidelines for Acute Respiratory Failure. Following are its major recommendations.

Case definition:

Respiratory failure is defined as a failure of gas exchange manifestedeither as hypoxemia (PO2 <60mm Hg on room air) i.e. inadequate blood oxygenation or hypercapnia (PaCO2>45 mm Hg) i.e. excess of circulating carbon dioxide or frequently a combination of both types of gas exchange abnormalities. Practically/ clinically diagnosed as respiratory fatigue.

Incidence of The Condition

The problem in US

1. 360,000 cases per year

2. 137 cases per 100,000 population

3. With 36% failing to survive the hospitalization

The problem in India: not known but respiratory failure is a common occurrence either as a complication of other diseases or as a terminal event

Differential Diagnosis/ Types :

Type 1

Type 1 respiratory failure is defined as hypoxemia without hypercapnia, and indeed the PaCO2 may be normal or low. The basic defect in type 1 respiratory failure is failure of oxygenation characterized by:

PaO2	low (< 60 mmHg (8.0 kPa) on room air
PaCO2	normal or low

This type of respiratory failure is caused by conditions that affect oxygenation such as:

 Parenchymal disease (V/Q mismatch)

 Diseases of vasculature and shunts: right-to-left shunt, pulmonary embolism

 Interstitial lung diseases: ARDS, pneumonia, emphysema.

Type 2

The basic defect in type 2 respiratory failure is characterized by:

PaO2	decreased
PaCO2	increased

Type 2 respiratory failure occurs as a result of alveolar hypoventilation and results in inability to effectively eliminate carbon dioxide.

The commonest cause of type II respiratory failure is COPD.

Other causes are:

1. Impaired central nervous system drive to breathe

• Drug over dose


• Brain stem injury


• Sleep disordered breathing


• Hypothyroidism

2. Impaired strength with failure of neuromuscular function in the respiratory system

• Myasthenia Gravis


• Guillian Barre Syndrome


• Amyotrophic Lateral Sclerosis


• Phrenic nerve injury


• Respiratory muscle weakness secondary to myopathy,electrolyte imbalance, fatigue

3. Increased loads on the respiratory system

• Resistive-bronchospasm (Asthma ,Emphysema, Chronic Obstructive Pulmonary Disease)


• Decreased lung compliance-Alveolar edema, Atelectasis, Auto peep


• Decreased chest wall compliance- Pneumothorax, Pleural effusion, Abdominal distension


• Increased minute ventilation requirement- pulmonary embolism by increase in dead space ventilation, sepsis and in any patient with type I respiratory failure with fatigue.

Type 3 and 4 occur in setting of perioperative period due to atelectasis and muscle hypoperfusion respectively.

Prevention And Counseling

Treatment of underlying disease.

Optimal Diagnostic Criteria, Investigations, Treatment & Referral Criteria

*Situation 1: At Secondary Hospital/ Non-Metro situation: Optimal Standards of Treatment in Situations where technology and resources are limited

Clinical Diagnosis:

Dyspnoea at rest, tachypnoea, tachycardia, hypertension, nasal flaring, pursed lip breathing, using accessory muscle of respiration.Evidence of central / peripheral cyanosis, asterexis or severe drowsiness in case COPD is feature of severe hypercapnia.

Investigations:

Pulse oxymetric assessment of SpO2 to assess blood oxygen content / hypoxia.

Chest x-ray:Details regarding evidence of consolidation, pulmonary edema, COPD and various other pathology

Complete blood count, electrolytes

Electrocardiogram

Treatment:

Oxygen therapy:

In the hypoxic self-ventilating patient, delivery of oxygen to the alveoli is achieved by increasing the environmental oxygen fraction (FiO2), which involves application of supplemental oxygen.

Oxygen therapy will suffice if muscle strength or vital capacity is reasonable and upper airway is not compromised. Pulse oxymetry is used to quickly titrate to the preferred levels of oxygen administration

Various oxygen delivery devices:

1.Variable performance:

Nasal cannula delivers oxygen at low gas flow 1-6lpm with FiO2 from 21-44 %. Best device for patient with high PCO2as no rebreathing.

Face maskdelivers oxygen at low gas flow 6-10lpm with FiO2 upto 50%. Nonrebreathingface maskwith reservoir bag delivers oxygen at flow rates 9-15 lpm with FiO2 from 85-90%.

Delivery of oxygen is dependent on the patient inspiratory flow rates.

2. Fixed performance:

Venture type mask –ensures fixed FiO2 above fixed flow.

• Nebulised bronchodilators to relieve bronchospasm


• Appropriate early antibiotics in case of pneumonia or in case of infective exacerbation of COPD or antimalarials or antivirals as per case requirement.


• IV steroids for acute exacerbation of COPD or bronchial asthma.


• IV diuretics for acute pulmonary edema.

Referral criteria:

• Need for invasive mechanical ventilation in cases of worsening hypoxemia or respiratory muscle fatigue in spontaneous breathing patient or on NIV. (Non-invasive ventilation in secondary care hospitals to be offered only if backed up by invasive mechanical ventilation)


• Need for non-invasive ventilation for worsening hypercapnic respiratory failure in COPD patients.


• Unable to wean the patient off the ventilator in 48-72 hrs in small set up.


• Need for specialized treatment.

*Situation 2: At Super Specialty Facility in Metro location where higher-end technology is available

Clinical Diagnosis:

Dyspnoea at rest, tachypnoea, tachycardia, hypertension, nasal flaring, pursed lip breathing, using accessory muscle of respiration.Evidence of central / peripheral cyanosis, asterexis or severe drowsiness in case COPD is feature of severe hypercapnia.

Investigations:

• Arteial blood gas analysis


• Echocardiogram


• Lung Function test (Spirometry)


• Ventilation Perfusion Scan


• CT scan of Chest


• Other investigations to look for underlying cause of respiratory failure

Treatment:

• Non invasive positive pressure ventilation or CPAP: Using a comfortable reasonably tight nasal or full face mask with ventilators used in cases of hypercapnic/ type II respiratory failure like COPD, sleep apnoea, bronchial asthma and hypoxemic respiratory failure as in acute cardiogenic pulmonary edema.


• Mechanical ventilation with endotracheal intubation:

Indications :

1. Type I /hypoxemic respiratory failure where the patient is unable to meet the oxygen requirements of the body or is able to do so only at a very high cost that results in haemodynamic and metabolic compromise.

2. Type II/ hypercapnic respiratory failure where the ventilarory pump has failed.

• Goals of mechanical ventilation


• Correct hypoxemia-PO2 ~60 mmHg/ SpO2 90%


• Correct hypercapnic-PCO2 ~ 40mmHg


• Reduce work of breathing


• Reversal of respiratory muscle fatigue.

Complication of mechanical ventilation:

1. Related to intubation:

• Loss of protective airway reflexes leading to aspiration


• Autonomic stimulation causing either tachycardia and hypertension or bradycardia


• Hypotension in fluid depleted patients post induction with sedations.

2. Complication secondary to endotracheal tube:blocked ,kinked and misplaced tube,unrecognised esophageal intubation

3. Pneumothorax

4. Ventilator associated pneumonias

5. Ventilator associated lung injury like volutrauma, atelectotrauma and barotrauma.

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.

9. Head end elevation of 35-45°.

10.Bowel bladder care

11.Care of eyes

12.Daily sedation interruption

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

14. Adequate Analgesia for pain

15. Infection control.

Weaning:

Weaning is a gradual process, which involves withdrawal of mechanical ventilation and removal of artificial airway. It represents the period of transition from total ventilatory support to spontaneous breathing.

Indications for weaning and extubation:

1. Resolution of disease and its acute phase

2. Patient is able to breathe spontaneously

3. Patient able to oxygenate

4. Patient able to protect the airway

Criteria for weaning

1. Resolution of disease and its acute phase

2. Patient has adequate cough

3. Adequate oxygenation:

PaO2 >60 mm Hg on

a) FiO2 < 0.5-0.6

b) PEEP < 5-10 cm of H2O

4. Stable haemodynamics without recent increase pressor requirement.

5. Adequate mentation or no recent deterioration in neurological status.

The best way to determine suitability for discontinuation of mechanical ventilation is to perform spontaneous breathing trial, which can be performed in following ways,

1. Check respiratory rate and tidal volume on no pressor- support and calculate Rapid Shallow Breathing Index and extubate. (RSBI=respiratory rate/tidal volume in L)

If RSBI <105 breaths/min/L then patient is suitable for extubation

2. A T-piece trial involves patient to breathing through T piece for a set period of time (30 min to max 180 min) The chances of successful extubation are high if patient passes the T-piece trial.

3. An alternative variant is the use of CPAP(continuous positive airway pressure) via an endotracheal tube, which overcomes the imposed work of breathing through ETT and prevents airway collapse.

During spontaneous breathing trial (SBT) presence of any of the following amounts to failure of SBT :

a. Change in mental status-somnolence, coma, agitation

b. Onset or worsening of discomfort

c. Severe diaphoresis

d. Signs of increased work of breathing- Use of accessory muscles, thoracoabdominal paradox.

e. Increase in heart rate >20 bpm or blood pressure > 20 mm of Hg, or any evidence of haemodynamic instability or new onset arrhythmias.

If a patient fails an SBT, then it is important to look for a reason like occult heart failure, neuromuscular pathology, etc.

Suitability for extubation :

1. All of the above

2. The patient with adequate cough and gag reflexes.

Extubation failure :

The use of post extubation non invasive ventilators has decreased the use need for re-intubation.

Tracheostomy :

Tracheostomies to be considered if mechanical ventilation is expected for more than 7-10 days.

Guidelines by The Ministry of Health and Family Welfare :

Rajesh Chawla, Consultant Physician and Intensivist, Indraprastha Apollo Hospital, Delhi