Comprehensive Notes on Oxygenation: Physiology, Pathology, and Clinical Management

Comprehensive vocabulary flashcards reviewing oxygen supply and demand concepts, chronic obstructive pulmonary disease, pneumonia, obstructive sleep apnea, atrial fibrillation, and arterial blood gas interpretations.

Oxygen Supply and Demand Framework

A clinical model conceptualizing oxygenation as a balance between metabolic oxygen consumption (demand) and delivery through inhaled gases, the respiratory system, blood, and the circulatory system (supply).

Fraction of Inspired Oxygen ($\text{FiO}_2$) of Ambient Air

The concentration of oxygen present in normal ambient room air, which comprises $21\%$ of inspired gases.

Chronic Obstructive Pulmonary Disease (COPD)

A progressive respiratory condition characterized by persistent airflow limitation resulting from obstructive chronic bronchitis and/or emphysema.

Obstructive Chronic Bronchitis

A component of COPD featuring inflammation, swelling, and excessive thick, sticky mucus production that narrows and blocks the bronchial airways.

Emphysema

A component of COPD marked by the destruction of alveolar walls and loss of lung elasticity, resulting in impaired gas exchange and trapped air.

Short-Acting Beta-2 Agonists (SABAs)

Rapid-acting bronchodilators, such as salbutamol, that stimulate sympathetic beta-2 adrenergic receptors to relax airway smooth muscle; used primarily as rescue therapy.

Long-Acting Beta-2 Agonists (LABAs)

Bronchodilator medications, such as salmeterol, that provide sustained relaxation of airway smooth muscle via beta-2 adrenergic receptor stimulation; used for maintenance therapy.

Short-Acting Muscarinic Antagonists (SAMAs)

Anticholinergic medications, such as ipratropium, that inhibit parasympathetic muscarinic receptors to rapidly dilate bronchial airways.

Long-Acting Muscarinic Antagonists (LAMAs)

Maintenance anticholinergic bronchodilators, such as tiotropium, that block parasympathetic bronchoconstriction to maintain airway patency over extended periods.

Inhaled Corticosteroids (ICS)

Topical anti-inflammatory inhalers, such as budesonide and fluticasone, that act locally within the lungs to decrease inflammation and prevent acute exacerbations of COPD.

Roflumilast

An oral phosphodiesterase-4 (PDE-4) inhibitor that reduces airway inflammation and relaxes smooth muscle; prescribed to prevent AECOPD in clients with frequent exacerbations.

Acute Exacerbation of COPD (AECOPD)

An acute worsening of respiratory symptoms—specifically dyspnea, cough, and sputum volume or purulence—that exceeds normal daily variations and requires increased medication.

Target $\text{SpO}_2$ in COPD

A controlled supplemental oxygen saturation goal of $88\text{--}92\%$ designed to treat hypoxemia while avoiding the suppression of the hypoxic drive or carbon dioxide retention.

General Target $\text{SpO}_2$

The standard arterial oxygen saturation titration goal of $94\text{--}98\%$ for non-COPD patients exhibiting signs of hypoxia or hypoxemia.

Community-Acquired Pneumonia (CAP)

Acute infection and inflammation of lung tissue acquired outside of a hospital or extended-care healthcare facility.

Hospital-Acquired Pneumonia (HAP)

Pneumonia that develops $\ge 48\,\text{hours}$ after hospital admission, frequently caused by antibiotic-resistant pathogens.

Aspiration Pneumonia

Pulmonary inflammation and infection resulting from the inhalation of foreign material, such as gastric acid contents or contaminated oral secretions, into the lungs.

Empirical Therapy

Initial medical treatment initiated based on clinical assessment, diagnostic presentation, and experience before the specific causative organism has been identified by lab cultures.

Hypercapnia

An elevation in arterial blood carbon dioxide ($\text{PaCO}_2$), which decreases blood pH and serves as the primary physiological driver stimulating the rate and depth of respiration.

Obstructive Sleep Apnea (OSA)

A sleep disorder caused by recurring physical collapse and obstruction of the upper airway by relaxed tissues (such as the tongue and soft palate), impairing nocturnal gas exchange.

STOP-BANG Questionnaire

An 8-item screening assessment for obstructive sleep apnea evaluating Snoring, Tiredness, Observed apnea, high blood Pressure, BMI ($> 35\,\text{kg/m}^2$), Age ($\ge 50$), Neck circumference ($> 40\text{--}43\,\text{cm}$), and Gender (male).

Mandibular Advancement Device (MAD)

A custom oral appliance used in mild-to-moderate OSA that mechanically moves the lower jaw and tongue forward to maintain airway patency during sleep.

Continuous Positive Airway Pressure (CPAP)

A mechanical device that delivers continuous pressurized airflow through a mask to pneumatically splint open the upper airway in patients with moderate-to-severe OSA.

Aerosol-Generating Medical Procedure (AGMP)

A healthcare intervention (such as CPAP) that generates respiratory aerosols; requires airborne-contact precautions (e.g., N95 respirator) when used on infectious patients.

Uvulopalatopharyngoplasty (UPPP)

A surgical procedure for severe OSA that trims and tightens redundant tissue in the throat, including the tonsils and uvula, to widen the pharyngeal airway.

Atrial Fibrillation (AF)

A supraventricular cardiac dysrhythmia featuring chaotic atrial electrical activity, an irregularly irregular ventricular response, absent P waves, and increased risk of thromboembolism.

Cardiac Output ($\text{CO}$)

The total volume of blood pumped by the heart per minute, determined by multiplying heart rate ($\text{HR}$) by stroke volume ($\text{SV}$): $\text{CO} = \text{HR} \times \text{SV}$.

Arterial Blood Gas (ABG) Reference Ranges

Standard baseline arterial laboratory values consisting of pH $7.35\text{--}7.45$, $\text{PaCO}_2$ $35\text{--}45\,\text{mm\,Hg}$, $\text{HCO}_3^-$ $22\text{--}26\,\text{mmol/L}$, and $\text{PaO}_2$ $80\text{--}100\,\text{mm\,Hg}$.

Oxygen Supply and Demand Framework

A clinical model balancing factors that deliver oxygen (inhaled gases, respiratory gas exchange, blood transport, and the circulatory pump/pipes) against tissue metabolic requirements.

Fraction of Inspired Oxygen ($\text{FiO}_2$) in Ambient Air

The proportion of oxygen in the ambient air we breathe, which is approximately $21\%$.

Hypercapnia

An increased level of carbon dioxide ($\text{CO}_2$) in the arterial blood that forms carbonic acid and lowers pH, serving as the primary stimulus signaling the brain to increase respiratory rate and depth.

Chronic Obstructive Pulmonary Disease (COPD)

A progressive lung condition characterized by chronic airflow limitation resulting from obstructive chronic bronchitis, emphysema, or both.

Obstructive Chronic Bronchitis

A component of COPD characterized by airway inflammation, mucosal swelling, and excessive thick, sticky mucus production that blocks rather than clears the airways.

Emphysema

A component of COPD characterized by destruction of alveolar walls and loss of elasticity, leading to impaired gas exchange and air trapping in damaged alveoli.

Short-Acting Beta2-Adrenergic Agonists (SABAs)

Rescue bronchodilator medications, such as salbutamol, that act rapidly via the sympathetic nervous system to relax bronchial smooth muscle and dilate airways.

Long-Acting Beta2-Adrenergic Agonists (LABAs)

Maintenance bronchodilator medications, such as salmeterol, that provide sustained relaxation and dilation of airway smooth muscle.

Short-Acting Muscarinic Antagonists (SAMAs)

Short-acting anticholinergic bronchodilators, such as ipratropium, that block parasympathetic bronchoconstriction to open airways.

Long-Acting Muscarinic Antagonists (LAMAs)

Long-acting anticholinergic medications, such as tiotropium, used for maintenance bronchodilation by blocking muscarinic receptors in airway smooth muscle.

Inhaled Corticosteroids (ICS)

Anti-inflammatory agents, such as budesonide and fluticasone, administered topically into the lungs to decrease airway inflammation and reduce exacerbation frequency; local adverse effects include oral candidiasis (thrush).

Roflumilast

An oral phosphodiesterase-4 (PDE-4) inhibitor that reduces airway inflammation and relaxes smooth muscle, prescribed to prevent acute exacerbations in clients with a history of frequent COPD exacerbations.

Acute Exacerbation of COPD (AECOPD)

An acute worsening of respiratory symptoms beyond normal day-to-day variations—specifically marked by increased dyspnea, cough, and sputum production—that necessitates escalated therapy.

Target $\text{SpO}_2$ in COPD

The recommended supplemental oxygen titration saturation target of $88\text{--}92\%$ designed to prevent oxygen-induced hypercapnia in patients with COPD.

Standard Target $\text{SpO}_2$

The supplemental oxygen saturation goal of $94\text{--}98\%$ for non-COPD patients exhibiting signs of hypoxia or hypoxemia.

Pneumonia

An acute microbial infection causing inflammation, exudative fluid accumulation, and impaired gas exchange in lung parenchymal tissue.

Hospital-Acquired Pneumonia (HAP)

Pneumonia occurring $\ge 48\,\text{hours}$ after hospital admission, frequently caused by antibiotic-resistant pathogens.

Aspiration Pneumonia

Lung inflammation and infection triggered by the inhalation of foreign substances, oral secretions, or gastric contents into the lower respiratory tract.

Empirical Therapy

The initiation of medical treatment based on clinical experience, presentation, and evidence-informed judgment before definitive laboratory identification of the causative organism.

Obstructive Sleep Apnea (OSA)

A sleep disorder caused by upper airway collapse when tongue and pharyngeal muscles relax during sleep, leading to intermittent airflow cessation and decreased pulmonary gas exchange.

STOP-BANG Questionnaire

An eight-item screening tool for obstructive sleep apnea assessing Snoring, Tiredness, Observed apnea, high blood Pressure, BMI ($> 35$), Age ($\ge 50$), Neck circumference ($> 40\text{--}43\,\text{cm}$), and Gender (male).

Polysomnography

A comprehensive sleep study that records brain waves, oxygen saturation, heart rate, breathing effort, and airflow to definitively diagnose obstructive sleep apnea.

Mandibular Advancement Device

A custom oral appliance worn during sleep that positions the lower jaw forward to maintain patency of the upper airway in mild to moderate OSA.

Continuous Positive Airway Pressure (CPAP)

A pneumatic splint therapy that delivers constant pressurized airflow through a mask to keep the upper airway open during sleep in moderate to severe OSA.

Aerosol-Generating Medical Procedure (AGMP)

A clinical intervention—such as CPAP—that can generate fine airborne droplets; when used on an infected patient, it requires Airborne-Contact precautions continuing for $\frac{1}{2}\,\text{hour}$ after device cessation.

Uvulopalatopharyngoplasty (UPPP)

A surgical procedure for severe OSA that trims and removes excess throat tissue, repositioning and suturing the uvula to widen the pharyngeal airway.

Atrial Fibrillation (AF)

A cardiac dysrhythmia characterized by rapid, uncoordinated electrical impulses originating in the atria, visible on an ECG as a jagged baseline lacking distinct P waves with an irregularly irregular rhythm.

Cardiac Output ($\text{CO}$)

The volume of blood pumped by the heart per minute, calculated using the equation $\text{CO} = \text{HR} \times \text{SV}$ (Heart Rate multiplied by Stroke Volume).

Normal Arterial Blood Gas (ABG) Reference Ranges

Physiological baseline parameters: pH $7.35\text{--}7.45$, $\text{PaCO}_2$ $35\text{--}45\,\text{mm Hg}$, $\text{HCO}_3^-$ $22\text{--}26\,\text{mmol/L}$, and $\text{PaO}_2$ $80\text{--}100\,\text{mm Hg}$.

Uncompensated Respiratory Alkalosis

An acid-base disturbance characterized by an elevated pH ($> 7.45$) and decreased $\text{PaCO}_2$ ($< 35\,\text{mm Hg}$) with a normal bicarbonate level ($\text{HCO}_3^-$ $22\text{--}26\,\text{mmol/L}$), typically precipitated by hyperventilation.

Partially Compensated Metabolic Acidosis

An acid-base disorder characterized by an acidic pH ($< 7.35$), primary low $\text{HCO}_3^-$ ($< 22\,\text{mmol/L}$), and secondary compensatory low $\text{PaCO}_2$ ($< 35\,\text{mm Hg}$) that has not yet restored normal pH.

Uncompensated Respiratory Acidosis

An acid-base imbalance characterized by an acidic pH ($< 7.35$), high $\text{PaCO}_2$ ($> 45\,\text{mm Hg}$), and normal $\text{HCO}_3^-$ ($22\text{--}26\,\text{mmol/L}$), frequently seen in acute hypoventilation or AECOPD.

Fully Compensated Metabolic Alkalosis

An acid-base state wherein high bicarbonate ($\text{HCO}_3^- > 26\,\text{mmol/L}$) is compensated by respiratory carbon dioxide retention ($\text{PaCO}_2 > 45\,\text{mm Hg}$), returning the blood pH back into the normal physiological range ($7.35\text{--}7.45$).