RESPIRATORY THERAPY GUIDE

Respiratory Disease

Respiratory disease is an umbrella term for diseases of the lung, bronchial tubes, trachea and throat . These diseases range from mild and self-limited (coryza -or common cold) to being life-threatening,(bacterial pneumonia, or pulmonary embolism for example).

Respiratory diseases can be classified as either obstructive (i.e. conditions which impede the rate of flow into and out of the lungs, for example asthma) or restrictive (i.e. conditions which cause a reduction in the functional volume of the lungs, for example pulmonary fibrosis).

Respiratory disease can be further classified as either upper or lower respiratory tract (most commonly used in the context of infectious respiratory disease), parenchymal and vascular lung diseases.

Obstructive Lung Disease

Obstructive Lung Diseases (OLD) are characterised by an increase in airway resistance, evidenced by a decrease in Peak Expiratory Flow Rate (PEFR; measured in spirometry by the Forced Expiratory Volume in 1 Second, FEV1). The Residual Volume, the volume of air left in the lungs following full expiration, is greatly increased in OLD, leading to the clinical sign of chest over-inflation in patients with severe disease. Many patients with chronic OLD present with "barrel chest" - a deformity of outward rib displacement due to chronic over-inflation of the lungs. Patients with OLD typically have 'large, floppy lungs'.

In Obstructive Lung Disease, the lung volume (Total Lung Capacity, TLC), Vital Capacity (VC), Tidal Volume (VT) and Expiratory Reserve Volume (ERV) remain relatively unchanged.

In some cases of OLD there is a mismatch in the FEV1/FVC ratio, due to the FEV1 decrease observed in OLD. In normal people, the FEV1/FVC ratio will equal 0.8, meaning that 80% of the total amount of expired air is expelled in the first second (the FEV1). Patients with OLD will typically have a lower FEV1, meaning that their FEV1/FVC ratio will typically be less than 0.8.

Some notable obstructive lung diseases are:

Emphysema
Bronchitis
Asthma
Chronic obstructive pulmonary disease (COPD)
Bronchiectasis
Byssinosis
Bronchiolitis
Asbestosis

Restrictive Lung Disease

Restrictive Lung Diseases (RLD) are characterised by a loss of airway compliance, causing incomplete lung expansion (i.e. via increased lung 'stiffness'). This change manifests itself in a reduced Total Lung Capacity, Inspiratory Capacity and Vital Capacity. In contrast to OLD, RLD values for Tidal Volume, Expiratory Reserve Volume, Functional Residual Capacity and Respiratory Volume are unchanged. The FEV1 for a patient with RLD will either be normal or slightly increased, and thus the FEV1/FVC ratio will also be normal or increased for a RLD patient.

Notable restrictive lung diseases include:

Fibrosis
Sarcoidosis
Pleural effusion
Hypersensitivity pneumonitis
Asbestosis
Pleurisy
Lung Cancer
Infant respiratory distress syndrome (IRDS)
Acute respiratory distress syndrome (ARDS)
Neurologic diseases affecting the ability of the body to alter respiration rate, including spinal cord injury
Mechanical diseases affecting pulmonary musculature, including myasthenia gravis
Severe acute respiratory syndrome (SARS)

Parenchymal Lung Disease

The basic functional units of the lung, the alveoli, are referred to as the lung parenchyma. Diseases such as COPD are characterised by destruction of the alveoli and are therefore referred to as parenchymal lung diseases.

Signs of parenchymal lung disease include, but are not limited to, hypoxemia (low oxygen in the blood) and hypercapnoea (high carbon dioxide in the blood).

Chronic complications of parenchymal lung disease include reduced respiratory drive, right ventricular hypertrophy, and right heart failure (cor pulmonale).
Notable parenchymal diseases include:

COPD
Sarcoidosis
Pulmonary fibrosis
Emphysema

Vascular Lung Disease

Vascular lung disease refers to conditions which affect the pulmonary capillary vasculature. Alterations in the vasculature manifest in a general inability to exchange blood gases such as oxygen and carbon dioxide, in the vicinity of the vascular damage (other areas of the lung may be unaffected).

Signs of vascular lung disease include, but are not limited to, hypoxemia (low oxygen in the blood) and hypercapnoea (high carbon dioxide in the blood).

Chronic complications of vascular lung disease include reduced respiratory drive, right ventricular hypertrophy, and right heart failure (cor pulmonale).
Notable vascular lung diseases include:

Pulmonary oedema
Pulmonary embolism
Pulmonary hypertension

Infectious Lung Disease

Infectious Lung Diseases are, as the name suggests, typically caused by one of many infectious agents able to infect the mammalian respiratory system (for example the bacterium Streptococcus pneumoniae).
The clinical features and treatment options vary greatly between infectious lung disease sub-types as each type may be caused by a different infectious agent, with different pathogenesis and virulence. Features also vary between:

Upper respiratory tract infection, including strep throat and the common cold; and
Lower respiratory tract infection, including pneumonia and pulmonary tuberculosis

Respiratory Tumour

"Respiratory tumour" can refer to either neoplastic (cancerous) or non-neoplastic masses within the lungs or lung parenchyma.

Neoplastic respiratory tumours : Respiratory neoplasms are abnormal masses of tissue within the lungs or parenchyma whose cell of origin may or may not be lung tissue (many other neoplasms commonly metastasize to lung tissue). Respiratory neoplasms are most often malignant, although there are non-malignant neoplasms which can affect lung tissue.

Respiratory neoplasms include the following:

Mesothelioma
Small cell lung cancer
Non-small cell lung cancer