Case scenario 1

A 30-year-old male patient presented with acute onset of breathlessness, dry cough, fever, myalgia, and malaise for 4 days. On examination, he was found to be febrile and restless, with respiratory rate of 46/min and pulse rate of 124/min. His oxygen saturation was 80% on room air, and chest skiagram showed bilateral parenchymal infiltrate.

Case scenario 2

A 60-year-old male patient with chronic obstructive airway disease presented with increasing shortness of breath, cough, and expectoration for 5 days and drowsiness with confusion for 1 day. On examination, he was found to be drowsy, cyanosed with respiratory rate of 30/min, tachycardia, and flapping tremors. His oxygen saturation was 80% on initial evaluation, and a chest radiograph showed hyperinflated lung fields and right lower zone infiltrates.

Case scenario 3

A 30-year-old female patient with anxiety disorder presented to the emergency department in a comatosed condition with history of ingestion of some unknown tablets. On examination, she was found to be E2M4V1, with pulse rate of 64/ min, respiratory rate of 14/min, and blood pressure of 90/60 mmHg.

R. Guleria, M.D., D.M. (*) • J. Kumar, M.D.

Department of Pulmonary Medicine, All India Institute of Medical Sciences, New Delhi, India

e-mail: randeepg@hotmail.com

Acute respiratory failure results from the failure of respiratory system in one or both of its gas exchange functions—oxygenation and carbon dioxide elimination. It is a major cause of morbidity and mortality in intensive care units (ICUs). There are two types—type 1 hypoxic respiratory failure and type 2 hypercapnic respiratory failure.

Step 1: Initiate cardiopulmonary resuscitation

All patients should be resuscitated as mentioned in Chap. 78.

•Airway: In all patients with altered sensorium, a secure airway should be the first priority. This includes clearing the upper airway and keeping it patent. If the patient cannot maintain an airway, endotracheal intubation should be performed to keep the airway patent.

•Breathing: Once the airway is patent, the breathing has to be assessed. If it does not result in adequate gas exchange, oxygen supplementation and assisted ventilation may be required.

•Circulation: An intravenous access should be established and intravenous fluids should be started.

Step 2: Clinical assessment including history and detailed physical examination

•Take appropriate history and do detailed examination to distinguish whether the etiology is pulmonary or extrapulmonary and to know whether it is type 1 or type 2 respiratory failure (Tables 2.1 and 2.2). Assess the severity and find out the underlying cause and/or precipitating cause. Specific focus should be on the following:

–A detailed respiratory system and neurological assessment.

–Look for clinical features of hypoxia and hypercapnia (Tables 2.1 and 2.2).

–Signs of pulmonary hypertension and right ventricular failure.

–Clinical features of drug overdose.

–Chest wall deformity, obesity.

Step 3: Check pulse oximetry and do arterial blood gas analysis

Pulse oximetry and arterial blood gases are the mainstay of diagnosis and essential to decide on the therapeutic intervention.

•Oximetry is a rapid technique to know if there is significant hypoxia, but it gives no clue about the presence or absence of hypercapnia. Also, the severity of hypoxia on pulse oximetery should be interpreted cautiously if the patient is already on oxygen.

Table 2.3 Causes of hypoxemic respiratory failure

1.Ventilation/perfusion mismatch Airways disease

Chronic obstructive pulmonary disease Asthma

Cystic fibrosis Bronchiolitis obliterans

Alveolar filling

Cardiogenic Pulmonary edema Mitral valve stenosis

Acute respiratory distress syndrome Pneumonia

Alveolar hemorrhage Partial atelectasis Alveolar proteinosis

Transfusion related acute lung injury (TRALI) Acute interstitial pneumonia

Cryptogenic organizing pneumonia Aspiration, near-drowning

Pulmonary vascular disease—thromboembolism, fat embolism

2.Shunt

Alveolar filling—see the above causes Atelectasis

Intrapulmonary shunts—pulmonary AVM (Arterio Venous Malformation) Intracardiac shunt—PFO, ASD, VSD

3. Hypoventilation—refer to type 2 respiratory failure for causes of hypoventilation

4. Low inspired pressure of oxygen—high altitude

•Computed tomography (CT) or magnetic resonance imaging (MRI) if indicated for interstitial lung disease, neoplasm, stroke, and other neurological disorders

•Two-dimensional echocardiography for identification of cor pulmonale, intracardiac shunt, patent ductus arteriosus, and pulmonary embolism

Step 6: Initiate specific treatment

The primary aim is to maintain oxygenation and adequate alveolar ventilation and treatment for the underlying etiology. The key principles in the management of respiratory failure are as follows:

•Optimized oxygen therapy

•Identification of the underlying cause and adequate treatment for the same

•Clinical assessment and arterial blood gases to help decide the severity

•Treatment for any precipitating cause

•Appropriate pharmacological treatment

•Ventilatory support—noninvasive and invasive Oxygen therapy (see Chap. 14)

Table 2.4 Causes of type 2 respiratory failure

Central nervous system depression/decreased ventilatory drive

Respiratory center (medulla) dysfunction

Drug overdose

Hypothyroidism

Sleep apnea

Central nervous system (CNS) causes— stroke, tumor

Neuromuscular diseases

Guillain–Barré syndrome

Poliomyelitis

Myasthenia gravis

Amyotrophic lateral sclerosis

Cervical cord lesions

Polyneuropathies

Muscle diseases like muscular dystrophy, polymyositis

Chest wall/pleural diseases

Kyphoscoliosis

Morbid obesity

Pneumothorax

Hypoxemic respiratory failure

Fig. 2.1 An approach to hypoxemic respiratory failure to know the etiology

•The primary goal is to correct the hypoxemia to maintain adequate tissue oxygenation.

•Oxygen has to be given cautiously with monitoring as uncontrolled high-flow oxygen can lead to respiratory depression and worsening hypercapnia in type 2 respiratory failure. Oxygen saturation around 90% should be maintained.