Introduction 

Pulmonary Embolism (PE) is the blockage of the vessels of the lungs, particularly the arteries by blood clot or thrombus. Typically, this clot has been transported through the blood in the veins from another part of the body, usually the legs, to this point; this condition is called Deep Vein Thrombosis (DVT).¹

In the circulatory system, the veins carry deoxygenated blood away from organs in the body towards the heart while the arteries carry oxygenated blood from the heart to every organ in the body. The purification of blood and gas exchange takes place in the lungs.

The mechanism of exchange is disrupted when a thrombus blocks the pulmonary arteries, leading to low levels of oxygen in the blood, this is called hypoxemia and manifests as chest pain, lightheadedness or more severely as cardiac arrest.¹  

How is a thrombus formed?

A thrombus is a blood clot that breaks off and blocks tiny blood vessels when it gets stuck. In pulmonary embolism, DVT  is the source of the thrombus.^2,1 

It is, therefore, important to supplement breathing and prevent harmful events that may arise from inadequate supply of oxygen to the blood and other vital organs required for proper functioning of the body. This article aims to enlighten you on the importance of respiratory therapy in ameliorating the effects of pulmonary embolism in breathing. 

Understanding Pulmonary Embolism

DVT is triggered by any condition that disturbs the flow of blood to the heart or causes excessive clotting.³  These conditions are risk factors of PE.

Immobility is an example of such a condition;⁴ mobility causes contraction,  which is required for blood to flow through the veins. When you do not move or walk for a certain period of time, maybe due to surgery or illnesses, contraction is hindered, limiting blood flow. Clotting factors in the blood are then activated and the blood begins to clump together forming clots or thrombus.⁵ Later on, this thrombus travels with blood through the veins towards the heart and gets stuck in arteries in the lungs and clogs it. 

Other risk factors include: obesity, cancer, smoking, hypertension, oral contraceptives, pregnancy, genetic factors, etc.⁴

Impact on pulmonary circulation and right ventricular function

For gas exchange to be successful, both blood and air must adequately reach the alveoli but when the thrombus blocks the arteries, both blood flow and respiration are impaired.⁶ Oxygen O₂ and carbon dioxide CO₂ are exchanged between air in the alveoli of the lungs and blood coming from the heart. This is the mechanism that ensures proper respiration.¹⁵ PE disrupts the balance between the flow of blood and gas, hence, respiration is impaired and the volume of oxygen in the blood is insufficient, a condition called hypoxemia.⁴ 

The right side of the heart pumps blood to the lungs and in order to make up for the increased pressure in the pulmonary arteries caused by the embolism, the right ventricle has to work harder to keep pumping blood. This results in decreased output from the left ventricle and if not properly managed, can cause reduction in total cardiac output, shock and eventually death.⁶

Symptoms and Diagnosis

Common symptoms of PE include:

• Difficulty in breathing
• Shortness of breath
• Increased work of breathing
• Lightheadedness
• Loss of consciousness
• Chest pain around the lungs
• Blood in coughed mucus

Diagnosis 

In order to properly diagnose PE, evaluation should include;

• Chest X-ray
• Electrocardiography (ECG)
• Measurement of arterial blood gas

Role of Respiratory Therapy in PE management

Initial Assessment

First, oxygen saturation monitoring; this measures the amount of hemoglobin, the oxygen-carrying component of blood, that carries oxygen and how much of it does not. The volume of oxygen in the blood of persons with PE is altered when embolism impairs respiration leading to hypoxemia. If PE is not diagnosed early, other complications may arise, such as dysfunction of the right ventricle of the heart, predisposing to hypotension and obstructive shock.⁸ Furthermore, other vital organs like the brain, liver and kidneys are at risk when they do not receive their adequate supply of oxygen- hypoxia and may ultimately lead to death.⁷  

Pulse oximetry is the tool used to measure oxygen saturation, it is placed over a finger and does not require withdrawing blood. It is sensitive to the wavelength of hemoglobin and detects how much oxygen is lacking in the blood.⁷ This gives an insight to how severe the embolism is. 

Respiratory distress is another lung condition that is measured in PE. It also leads to low blood oxygen. Acute Respiratory Distress Syndrome (ARDS), is characterized as first, a buildup of fluid in the alveoli and also, the breakdown of a substance called surfactant, it is produced in the body and ensures that the lung is fully expanded for you to breathe. When fluid fills the alveoli instead of air and the lung cannot fully expand, then, enough oxygen cannot get into the blood.⁹ 

Fluid in the lungs has been identified as a complication of PE but specifically, in patients with right ventricular dysfunction which is caused by right ventricular failure.¹⁰  A  blood test can be performed to measure the amount of oxygen in the blood and pulse oximetry can also be used to diagnose this condition.¹¹             

Supportive Measures

Supplemental Oxygen Therapy for Hypoxemia

Supplemental oxygen is the medical treatment for hypoxemia where embolism does not  block the delivery of oxygen completely but oxygen saturation is less than 90%.¹² 

Oxygen is supplied using equipment that increases pressure in the airways thereby enlarging the lungs and increasing the flow of oxygen.¹³ This treatment is an adjunct to complement the amount of oxygen that reaches the blood.

Non-invasive ventilation strategies

Non-invasive ventilation is a technique in supplemental oxygen therapy that supplies oxygen to the lungs through a ventilator using a mask; it does not require inserting any device directly into the lungs.¹³ 

Two types of non-invasive ventilation exit depending on the condition of the person: Continuous Positive Air Pressure (CPAP) and Bilevel Positive Air Pressure (BiPAP) 

CPAP is used to sustain continuous air pressure in people experiencing partial embolism where respiration is not completely blocked, the person can initiate inspiration. CPAP maintains the level of pressure during both inspiration and expiration, the positive pressure is set the same throughout the cycle of inspiration and expiration, this opens the alveoli up for gas exchange and also maintains the level of residual pressure in the alveoli after expiration, reducing work of breathing.¹⁴

BiPAP, on the other hand, provides two pressures to the patient; Inspiratory Positive Airway Pressure (IPAP), and Expiratory Positive Airway Pressure (EPAP). IPAP is a higher pressure that supplements breathing by overcoming the natural pressure threshold required to initiate inspiration. EPAP on the other hand, like CPAP, is a lower pressure applied throughout expiration, providing support and keeping the alveoli open, thus, improving oxygenation.¹³ 

BiPAP is used in patients who experience difficulty with ventilation; it supplies most of the pressure needed to inflate the lungs, reducing the work of breathing. BiPAP is used as a good option to prevent intubation.¹³

Advanced Respiratory intervention

Indication for invasive technique in severe cases

In mechanical ventilation, an invasive technique commonly called intubation, involves applying pressure to the lungs through a tube which goes directly to the windpipe (trachea); this is to create an artificial passage for air. This endotracheal tube is connected to a ventilator which fills the lungs with air, in order to facilitate respiration and aid oxygenation.¹⁶  

Intubation process requires that the person is sedated. It is usually the last resort when non-invasive techniques do not provide the adequate oxygenation required in the blood and vital organs are at risk of not getting enough oxygen.

Potential complications and consideration of invasive respiratory intervention

• Constant high pressure entering into the lungs can lead to damage to the alveolar
• Alteration of intrathoracic pressure and cardiac output: intubation increases pressure within the thorax, causing a reduction in the volume of blood that fills the heart ventricles hence, impairing cardiac output
• The use of ventilators can predispose to infections and the most common being ventilator-associated pneumonia
• Too much oxygen may become toxic
• Neuromuscular complications may arise from sedation

Positioning technique

The position of the body is important because it enhances the natural effect of gravity on how oxygen is transported and also, the volume of the lungs. Positioning can be therapeutic, prescribed for proper functioning of the heart and lungs, this is because it affects ventilation and perfusion and their balance in respiration.

An example of such positioning is the semi-Fowler’s lying where the head of the bed is elevated to about 30 or 45 degrees. Evidence has shown that this position increases the percentage of oxygen-carrying hemoglobin in the blood, that is known as oxygen saturation.¹⁷

Pharmacological Management Related to Respiratory Therapy

Anticoagulatory therapy

Anticoagulants are the drug of choice and first line in the treatment of PE. It is used both in prevention in individuals who are at high risk and for treatment.¹⁹ 

Anticoagulants, commonly referred to as blood thinners, are medications used to prevent the formation of harmful clots in the blood vessels and to break down already existing clots.¹⁸ 

Oral anticoagulants (such as Apixaban, Rivaroxaban, Dabigatran)²⁰ are used for prevention and in long term treatment of PE whereas unfractionated Heparin (injectable)  is used as prevention in people that are at high risk but for short-term.¹⁹ 

Thrombolytic therapy

Thrombolytic therapy is usually used as a last resort for patients whose PE is clinically serious or extensive. These agents dissolve blood clots more rapidly and have been shown to cause bleeding. Examples include: streptokinase, urokinase, and recombinant tissue‐type plasminogen activator.²¹  

Conclusion

Respiratory therapy is important in the management of pulmonary embolism. It is useful as an adjunct to pharmacological treatment aimed at dissolving the clot in the blood vessels. Respiratory therapy supports breathing, eases the burden of work of breathing, improves the ventilation of the blood and prevents shutdown of vital organs in the body and prevents death.

It is, therefore, essential that respiratory therapy is included in the treatment regimen for pulmonary embolism. Healthcare practitioners should encourage and promote it as an adjunct therapy.