RESPIRATORY DISORDERS - MODULE 6

What is dyspnea and what are its types?

• dyspnea: shortness of breath

  • signs include nostril flaring and use of accessory respiratory muscles

• orthopnea: dyspnea when lying down

  • abdomen puts pressure on the diaphragm

• paroxysmal nocturnal dyspnea (PND): waking up at night with dyspnea

What causes coughing in pulmonary disease?

• irritant receptors in the airway start coughing

• few receptors in distal respiratory airways

  • allows significant secretions to build up before the cough reflex

What is abnormal sputum in pulmonary disease?

• changes in sputum

  • amount

  • colour

  • consistency

• may have cellular debris and microorganisms

What is hemoptysis?

coughing up of blood

• bright red

• alkaline pH

• frothy sputum

What are abnormal breathing patterns?

• hypoventilation

• hyperventilation

What is cyanosis?

bluish discoloration of skin and mucous membranes

• caused by increased deoxygenated hemoglobin in the blood

What is clubbing?

• selective bulbous enlargement at the end of a digit

What causes pain in pulmonary disease?

• pain originates from:

  • pleurae

  • airways

  • chest wall

• causes include:

  • infection

  • inflammation

  • stiff muscles from coughing

What is hypercapnia (hypercarbia) and how does it occur?

• increased CO2 in arterial blood

• caused by alveolar hypoventilation

  • CO2 moves from blood to alveoli 20× more than O2

  • CO2 exchange depends on alveolar ventilation

What causes hypercapnia (hypercarbia)?

anything that decreases the drive or ability to breathe, including:

• drugs

• damage to the medulla

• increased physiologic dead space

  • e.g. emphysema

What is hypoxemia and how does it differ from hypoxia?

• hypoxemia: reduced oxygen of artery blood

• hypoxia: reduced oxygen of tissue cells

• O2 diffuses less across the alveolocapillary membrane than CO2

What are the three mechanisms that can cause hypoxemia when impaired?

• decreased oxygen delivery to the alveoli

• decreased oxygen diffusion from alveoli to blood

  • V/Q mismatch

  • decreased diffusion across the alveolocapillary membrane

• anatomical right-to-left shunt

What causes decreased oxygen delivery to the alveoli?

• decreased oxygen in the air

• decreased ventilation

  • unconsciousness

  • diseases restricting chest expansion

What is V/Q mismatch?

• imbalance between:

  • alveolar ventilation (V)

  • perfusion (Q)

• most common cause of hypoxemia

• can involve:

  • high V/Q

  • low V/Q

What causes decreased oxygen diffusion across the alveolocapillary membrane?

• thickening of the alveolocapillary membrane

  • due to edema or fibrosis

What is high V/Q mismatch?

• inadequate perfusion of a well-ventilated area

  • produces alveolar dead space

• mainly caused by pulmonary embolism

What is low V/Q mismatch?

• inadequate ventilation of a well-perfused area

• causes include:

  • atelectasis

  • asthma

  • pulmonary edema

• is also known as a physiological right-to-left shunt

  • blood moves through unventilated parts of the lung

What is anatomical right-to-left shunting?

• structural defect in the heart

  • causing blood to bypass the lungs

• pulmonary circulation is partially bypassed

  • creating a shortcut for blood flow through the heart

  • reducing blood flow to the alveoli

• example: Tetralogy of Fallot

What is chest wall restriction and what causes it?

• decreased tidal volume

  • occurs when the chest wall is deformed, traumatized, or immobilized

• causes include:

  • gross obesity

  • neuromuscular diseases

    • poliomyelitis

    • muscular dystrophy

  • chest wall trauma

    • flail chest

What is flail chest?

paradoxical chest wall movement

• chest wall moves inward during inspiration

• chest wall moves outward during expiration

What is pneumothorax and how is it treated?

• air in the pleural space

  • caused by rupture of the visceral or parietal pleura

  • air pushed on the lung outside leads to collapsed lung

• treatment:

  • needle or chest tube is inserted between ribs to remove excess air

  • can heal naturally if small

What is pleural effusion?

excess fluid in the pleural space

• usually caused by fluid moving through capillary walls bordering the pleura

What is empyema?

• infected pleural effusion

  • pus in pleural space

• complication of:

  • pneumonia

  • surgery

What is atelectasis and what causes it?

collapse of lung tissue caused by:

• external compression

  • fluid in pleural space, tumour, abdominal distension

• obstructed airways

• inhalation of concentrated oxygen

  • increasing gas absorption

• decreased surfactant production

  • such as from anesthesia

What are the clinical manifestations of atelectasis?

• dyspnea

• cough

• fever

• leukocytosis

Why is atelectasis common after surgery and how is it prevented?

• commonly develops after surgery

  • pain causing shallow breathing

  • viscous bronchial secretions

  • narcotics/anesthesia reducing surfactant

• prevention includes:

  • deep breathing

  • becoming ambulatory as soon as possible

  • frequently changing positions when lying down

What is bronchiectasis and what causes it?

• permanent dilation of the bronchi

  • caused by diseases leading to chronic inflammation of bronchial walls

  • e.g. tuberculosis (TB), cystic fibrosis

• chronic inflammation

  • destroys elastic and muscular components of bronchial walls

  • causing permanent dilation

What are the clinical manifestations of bronchiectasis?

• chronic cough

• recurring lower respiratory tract infections

• production of large amounts of purulent sputum (cupfuls)

• hemoptysis

• clubbing of the fingers

What is cystic fibrosis?

• autosomal recessive disorder

• mutation in chloride channels

  • preventing Cl⁻ from moving out of cells into the airways

  • causing thick mucus in the airways

How does cystic fibrosis cause respiratory infections?

• increased absorption of sodium and water

  • from respiratory and pancreatic secretions

• very thick mucus develops

  • preventing cilia from moving mucus

  • causing mucus accumulation

• increased risk of infections

  • especially from Pseudomonas aeruginosa

• recurring infections

  • causing bronchitis and eventually bronchiectasis

How is cystic fibrosis treated?

• antibiotics

  • controlling infections

• possible pancreatic enzyme replacement

What is pulmonary embolism and what causes it?

• occlusion of part of the pulmonary vascular bed by an embolus

• most common embolus

  • blood clot from deep vein thrombosis (DVT) in the lower leg

How does pulmonary embolism affect pulmonary circulation?

• obstruction of blood flow

  • causing pulmonary vessels to constrict

  • impairing gas exchange (V/Q mismatch)

• if the clot is not dissolved rapidly

  • resulting pulmonary hypertension may lead to right heart failure

    • right ventricle pumps blood to the lungs

What are the clinical manifestations of pulmonary embolism?

• depend on the size and location of the obstruction

• small emboli

  • may go unnoticed unless the patient's health is compromised

• moderate emboli

• massive emboli

What complications do moderate emboli cause?

• sudden chest pain

• dyspnea

• tachypnea

• tachycardia

What complications do massive emboli cause?

• sudden collapse

• crushing chest pain

• shock

• often fatal

What is pulmonary hypertension?

• elevated mean pulmonary artery pressure

• commonly develops as a complication of acute or chronic pulmonary disorders

  • e.g. COPD

What causes pulmonary hypertension?

• prolonged hypoxemia

  • causing pulmonary vessels to constrict

  • unlike systemic vessels, which dilate

• mitral valve disorders or left ventricular diastolic dysfunction

  • increasing left atrial pressure

  • associated with LHF

What is cor pulmonale?

• right ventricular enlargement

  • hypertrophy, dilation, or both

  • caused by chronic pulmonary hypertension

• increased systemic venous pressure

  • resulting in peripheral edema

What is pulmonary edema and how does it develop?

• excess fluid in the lungs

• most common cause is LHF

• left ventricular failure

  • increases filling pressure

  • causing blood to back up into the lungs

  • increases pulmonary capillary pressure

• capillary pressure exceeds osmotic pressure

  • causing fluid and RBCs to enter the interstitial space

• excess interstitial fluid

  • overwhelms lymphatic drainage

  • eventually leaking into the alveoli

How does pulmonary edema cause hypoxemia?

• fluid accumulation in the alveoli

  • reducing the number of alveoli available to expand with air

  • decreasing respiratory membrane surface area

• fluid thickens the respiratory membrane

  • increasing diffusion distance

• reduced oxygen diffusion

  • resulting in hypoxemia

What are the clinical manifestations of pulmonary edema?

• dyspnea

• cyanosis

• increased effort in breathing

• blood-tinged frothy sputum

What are obstructive lung diseases?

• airway obstruction that worsens during expiration

  • slowing the emptying of the lungs

• causes include:

  • asthma

  • chronic bronchitis

  • emphysema

• chronic obstructive pulmonary disease (COPD)

  • chronic bronchitis and emphysema often occur together

• common symptom: dyspnea

• common sign: wheezing

What is bronchial asthma?

• chronic inflammation of the bronchial mucosa

  • causing airway hypersensitivity and constriction

• involves genetic and environmental factors

• exposure to an allergen

  • triggers a chain of inflammatory events

  • leading to acute and chronic airway dysfunction

What happens during the early (acute) phase of bronchial asthma?

• type I hypersensitivity response

  • allergen exposure activates B cells (plasma cells) to produce IgE

  • IgE binds to mast cells

• further allergen exposure

  • cross-links IgE, causing mast cells to release chemicals

• released chemicals cause:

  • vasodilation

  • increased capillary permeability

  • mucosal edema

  • bronchial smooth muscle contraction

  • mucus secretion

What are the clinical manifestations of the early phase of bronchial asthma?

• chest constriction

• expiratory wheezing

• dyspnea

• tachycardia

• coughing

What happens during the late phase of bronchial asthma?

• begins 4–8 hours after the early response

  • may be more severe than the initial attack

• chemokines released during the early response

  • attracting neutrophils, eosinophils, and lymphocytes

• inflammatory chemicals released by these cells

  • causing further bronchospasm

  • edema

  • mucus secretion

How does the late phase of bronchial asthma damage the airways?

• inflammatory chemicals damage ciliated epithelial cells

• mucus accumulation and cellular debris

  • forming plugs in the airways

  • impairing alveolar ventilation

• untreated inflammation

  • may cause irreversible long-term airway damage

How does air trapping in bronchial asthma cause respiratory alkalosis?

• airway obstruction makes expiration difficult

  • trapping air in the alveoli

  • increasing alveolar gas pressure

• increased alveolar pressure

  • causing capillaries to collapse

  • decreasing perfusion and causing hypoxemia

• hypoxemia stimulates the respiratory centre

  • causing hyperventilation

• increased CO2 removal from blood

  • causing hypocapnia

  • resulting in respiratory alkalosis

How does respiratory muscle impairment in bronchial asthma cause respiratory acidosis?

• continued airway obstruction

  • increasing air trapping due to incomplete expiration

  • causing hyperexpansion of the lungs and thorax

• lung hyperexpansion

  • decreasing tidal volume

  • worsening hypoxemia

• rising CO2 levels

  • causing hypercapnia

  • resulting in respiratory acidosis

• life-threatening if not reversed quickly

  • mechanical ventilation may be required

How is bronchial asthma treated?

• avoidance of allergens

• inhaled medications

  • anti-inflammatories

  • bronchodilators

• adrenaline

  • during an acute attack

What is chronic obstructive pulmonary disease (COPD)?

• airway obstruction

  • causing difficulty with exhalation

• includes:

  • emphysema

  • chronic bronchitis

What is chronic bronchitis?

• hypersecretion of mucus

• chronic productive cough

  • lasting at least 3 months per year

  • for at least 2 consecutive years

• commonly caused by smoking

How does chronic bronchitis develop?

• inhalation of irritants

  • causing airway inflammation and edema

  • producing thick, tenacious mucus

• continued inflammation

  • increasing the size and number of mucus glands and goblet cells in the airway epithelium

How does chronic bronchitis develop through inflammation and airway obstruction?

• continued inflammation

  • attracting macrophages and neutrophils that release proteases

  • damaging ciliated epithelial cells

• impaired ciliary function

  • preventing mucus clearance

• thickened bronchial walls and mucus accumulation

  • narrowing the airways

  • making expiration more difficult

    • airways are still pulled open during inspiration

• airway obstruction

  • eventually causing hypoxemia

How does chronic bronchitis progress to air trapping and hypercapnia?

• airways collapse early during expiration

  • causing air trapping

• air trapping expands the thorax

  • making expiration more difficult

• results in:

  • decreased tidal volume

  • hypoventilation

  • hypercapnia

What are the long-term effects of chronic bronchitis?

• irreversible pathological changes

• hypoxemia

• eventual right-sided heart failure

  • causing edema

How is chronic bronchitis treated?

• bronchodilators and expectorants

  • controlling cough and reducing dyspnea

• smoking cessation

• chest physical therapy

• eventual treatments may include:

  • antibiotics for infections

  • steroids as a last resort

  • home oxygen therapy

What is emphysema?

• loss of lung elasticity

• abnormal enlargement of airspaces distal to the terminal bronchioles

  • destruction of alveolar walls and capillaries

• airway obstruction

  • mainly caused by loss of elastic recoil

  • unlike chronic bronchitis, which involves mucus production and inflammation

How does emphysema develop through inflammation and alveolar destruction?

• inflammation

  • neutrophils and macrophages release proteases

  • destroying alveolar walls

• alveolar destruction

  • reducing the capillary bed

  • increasing alveolar volume

• large air spaces form

  • bullae within the lungs

  • blebs near the pleura

• impaired gas exchange

  • these air spaces cannot participate in gas exchange

  • worsening hypoxemia

How does emphysema cause air trapping and hypercapnia?

• inflammation damages elastic lung tissue

  • reducing elastic recoil that helps keep airways open

• difficulty with expiration

  • causing air trapping

• air trapping hyperexpands the thorax

  • causing barrel chest

  • making breathing more difficult

• results in:

  • hypoventilation

  • hypercapnia

How does breathing change as emphysema progresses?

• initially mild hypoxemia

  • increased breathing meets oxygen demand

  • until the late stages of the disease

• classic tripod breathing position

  • with pursed-lip breathing

  • increasing lung pressure during exhalation

  • helping keep airways open

How is emphysema treated?

• smoking cessation

  • if the patient smokes

• inhaled medications

  • corticosteroids

  • bronchodilators

• oxygen therapy

  • if required

• possible surgical treatments

  • lung reduction surgery

  • lung transplant

What is acute respiratory distress syndrome (ARDS)?

• acute lung inflammation and injury

  • damaging the alveolocapillary membrane

  • causing severe pulmonary edema and hypoxemia

• injury and edema

  • caused by an inflammatory response to an initial injury

  • or direct injury, such as smoke inhalation

What causes acute respiratory distress syndrome (ARDS)?

• sepsis

• trauma

• pneumonia

• drug overdose

• smoke inhalation

• aspiration of gastric contents (acid)

How does ARDS develop through inflammation and edema?

• response to lung injury

  • neutrophils and platelets release inflammatory chemicals

  • damaging the alveolocapillary membrane

• increased capillary permeability

  • allowing blood to leak into interstitial spaces and alveoli

  • causing pulmonary edema

How does ARDS impair gas exchange and cause lung damage?

• surfactant inactivation

  • causing alveolar collapse

  • reducing gas exchange

• hyaline membrane formation

  • impairing gas exchange

• extensive lung injury

  • tissue repair may produce fibrosis

What are the clinical manifestations of ARDS?

• rapid onset of respiratory distress

  • usually within 12–18 hours of injury

  • marked dyspnea

  • rapid, shallow breathing

  • inspiratory crackles

• severe hypoxemia

  • not corrected by supplemental oxygen alone

• possible systemic inflammatory response

  • inflammatory compounds spreading throughout the body

How is ARDS treated and what is its prognosis?

• assisted ventilation

  • supplying high concentrations of oxygen until the lungs heal

• difficult to diagnose

  • may be fatal if not treated within 48 hours

• mortality rate

  • 50–70% (as stated in your lecture notes)

What is acute respiratory failure (ARF)?

• inadequate gas exchange

  • decreased PaO2

  • increased PaCO2

  • pH < 7.30

• important potential complication of surgery

  • atelectasis

  • pneumonia

  • pulmonary edema

  • pulmonary embolism

What are the two types of acute respiratory failure (ARF)?

• hypercapnic/hypoxemic

  • caused by failure of ventilation

• hypoxemic

  • caused by failure of gas exchange within the lungs

• both types can overlap

What is hypercapnic/hypoxemic respiratory failure?

• failure of ventilation

  • increasing arterial CO2 (hypercapnia)

  • causing hypoxemia

• causes of impaired ventilation

  • diseases of the nervous system

  • disorders of the respiratory muscles

• treatment

  • mechanical ventilation

What causes hypoxemic respiratory failure and how is it treated?

• ventilation/perfusion (V/Q) mismatch

  • common in COPD

  • lung regions may not be perfused or ventilated

• impaired oxygen diffusion

  • common in interstitial lung disease, ARDS, pulmonary edema, and pneumonia

• treatment:

  • high concentrations of oxygen

  • increasing the oxygen diffusion gradient

How does aging affect respiratory function?

• ages 20–25

  • vital capacity and respiratory muscle function peak

  • begin decreasing afterward

• after age 40

  • alveolar surface area decreases

• after age 50

  • alveoli begin losing elasticity

  • chest wall mobility decreases

What is croup (laryngotracheobronchitis)?

• upper respiratory tract obstruction/inflammation

  • causing inspiratory stridor, hoarseness, and barking cough

• causes include:

  • viruses (most common)

  • allergies

  • bacteria

• most common in children aged 6 months–5 years

• severe croup

  • causing retractions around ribs and sternum

  • indicating use of accessory respiratory muscles

• usually self-limiting

What is bronchiolitis?

• viral inflammation of the bronchioles

• common in children aged 2–12 months

• clinical manifestations:

  • wheezing

  • dyspnea

  • cough

What is epiglottitis?

• bacterial infection

  • causing swelling of the larynx and epiglottis

• clinical manifestations:

  • fever

  • sore throat

  • inspiratory stridor

What is infant respiratory distress syndrome (IRDS)?

surfactant deficiency

• occurring in premature infants