Respiratory

Arterial blood gas

A blood test used to assess oxygenation, carbon dioxide and acid-base status.

Moderate, acute severe, life threatening and near fatal

A memory aid for grading the severity of an acute asthma attack.

Timing and character of the added sound localise the pathology

A memory aid for interpreting crackles, wheeze and rubs.

Gas is fully saturated at body temperature by the time it reaches the isothermic boundary

A memory aid for how inspired gas is conditioned.

Medium-sized bronchi contribute most resistance, not the smallest airways

A memory aid for where airway resistance is greatest and what alters it.

Inspired oxygen minus carbon dioxide divided by the respiratory quotient

A memory aid for calculating alveolar oxygen tension.

Alveolar carbon dioxide is inversely proportional to alveolar ventilation

A memory aid for the relationship between ventilation and carbon dioxide.

A normal gradient points to hypoventilation or low inspired oxygen; a wide gradient points to lung disease

A memory aid for interpreting the A-a gradient.

Bronchial and thebesian veins drain deoxygenated blood into the systemic circulation

A memory aid for the normal physiological shunt.

RIPE: Rifampicin, Isoniazid, Pyrazinamide, Ethambutol

A mnemonic for the first line antituberculous drugs and their toxicity.

Immature respiratory control with a paradoxical response to hypoxia

A memory aid for why premature infants stop breathing.

Diffuse alveolar damage causes non-cardiogenic oedema, shunt and stiff lungs

A memory aid for the physiology of acute respiratory distress syndrome.

Oxygenation first, then pH, then carbon dioxide, then bicarbonate

A memory aid for the order in which to read an arterial blood gas.

Beta-2 agonists, antimuscarinics, corticosteroids and leukotriene antagonists

A memory aid for the classes of inhaled respiratory drug.

Variable airflow obstruction, demonstrated objectively

A memory aid for the objective tests used to diagnose asthma.

Bronchoconstriction, gas trapping and hyperinflation with V/Q mismatch

A memory aid for the physiological changes in acute asthma.

Bohr is carbon dioxide affecting oxygen carriage; Haldane is oxygen affecting carbon dioxide carriage

A mnemonic for distinguishing the Bohr and Haldane effects.

Rising carbon dioxide is the main stimulus, with falling oxygen contributing later

A memory aid for what terminates a breath hold.

Histamine and leukotrienes early, cellular infiltration late

A memory aid for the mediators of the early and late asthmatic response.

Pulmonary vessels carry blood for gas exchange; bronchial vessels nourish the lung tissue

A memory aid for the two separate blood supplies of the lung.

Permanent bronchial dilatation from chronic infection and inflammation

A mnemonic for the causes and management of bronchiectasis.

Bicarbonate about 70 per cent, carbamino about 23 per cent, dissolved about 7 per cent

A memory aid for the three forms in which carbon dioxide is carried.

Respiratory, cardiac, gastrointestinal and endocrine causes

A memory aid for the systemic causes of finger clubbing.

Low inspired oxygen, hypoventilation, diffusion impairment, V/Q mismatch, shunt

A mnemonic for the five mechanisms of arterial hypoxaemia.

Peripheral chemoreceptors sense oxygen; central chemoreceptors sense carbon dioxide

A memory aid for the peripheral and central chemoreceptors.

Percussion note, breath sounds and vocal resonance identify the pathology

A memory aid for the combination of chest signs in each condition.

The volume at which dependent small airways begin to close

A memory aid for closing capacity and its relationship to functional residual capacity.

The lung follows a different path on inflation than on deflation

A memory aid for why the inflation and deflation curves differ.

Chronic obstructive pulmonary disease

A chronic respiratory condition characterised by persistent airflow limitation.

Post-bronchodilator FEV1/FVC below 0.7, staged by FEV1

A memory aid for diagnosing COPD and grading its severity.

Controlled oxygen, bronchodilators, steroids, and antibiotics if infected

A mnemonic for treating an acute exacerbation of COPD.

Loss of elastic recoil, airway collapse, gas trapping and impaired gas exchange

A memory aid for the physiological changes in chronic obstructive pulmonary disease.

Inspiration, glottic closure, compression, then explosive expiration

A memory aid for the stages and pathway of the cough reflex.

Confusion, Urea, Respiratory rate, Blood pressure, age 65

A mnemonic for scoring the severity of community acquired pneumonia.

A defective chloride channel causes thick secretions in every exocrine organ

A memory aid for the molecular defect in cystic fibrosis.

A rule out test only, applied after a clinical probability score

A memory aid for when a D-dimer is useful and when it is not.

Physiological dead space equals anatomical plus alveolar dead space

A memory aid for anatomical, alveolar and physiological dead space.

Measured with carbon monoxide, reflecting surface area, membrane thickness and haemoglobin

A memory aid for the transfer factor and what alters it.

Beyond a certain effort, higher pleural pressure compresses airways and flow cannot increase

A memory aid for why forced expiration is effort independent.

Reduced functional residual capacity, blunted drive, and atelectasis

A memory aid for the respiratory changes under general anaesthesia.

Centriacinar from smoking, panacinar from alpha-1 antitrypsin deficiency

A memory aid for the patterns of emphysema.

Scooped expiratory limb in obstruction; flattening indicates large airway obstruction

A memory aid for interpreting the shape of the flow-volume loop.

A marker of eosinophilic airway inflammation

A memory aid for the use of FeNO in diagnosing asthma.

The balance point where inward lung recoil equals outward chest wall recoil

A memory aid for what raises and lowers functional residual capacity.

Inflation inhibits further inspiration; deflation stimulates it

A memory aid for the pulmonary stretch reflexes.

Uneven hypoxic pulmonary vasoconstriction overperfuses some capillaries

A memory aid for the mechanism of high altitude pulmonary oedema.

Organic dust exposure causing an immune reaction in the alveoli

A memory aid for extrinsic allergic alveolitis and its named causes.

Respiratory alkalosis causes paraesthesiae, tetany and cerebral vasoconstriction

A memory aid for the physiological consequences of acute hyperventilation.

Pulmonary arterioles constrict in hypoxia, diverting blood to better ventilated alveoli

A memory aid for the pulmonary vascular response to alveolar hypoxia.

Peripheral chemoreceptors respond only below about 8 kPa

A memory aid for the ventilatory response to hypoxia.

CHARTS for the upper zones, STAIR for the lower

A mnemonic for the upper and lower zone causes of pulmonary fibrosis.

Upper zone and lower zone causes have distinct differentials

A memory aid for classifying interstitial lung disease by zone.

Local invasion, distant spread and hormone secretion

A memory aid for the local, metastatic and paraneoplastic features of lung cancer.

Small cell is central and rapidly metastasising; non-small cell divides into squamous, adeno and large cell

A memory aid for the histological types of lung cancer and their behaviour.

A capacity is two or more volumes added together

A memory aid for the four lung capacities and the volumes that make them up.

Change in volume per unit change in pressure, determined by elastic tissue and surface tension

A memory aid for the determinants of lung compliance.

Volume, Air, Tidal, Inspiratory, Residual, Expiratory

A mnemonic for the key lung volumes and capacities measured in spirometry.

Four volumes combining into four capacities

A memory aid for the lung volumes and which cannot be measured by spirometry.

Minute ventilation includes dead space; alveolar ventilation does not

A memory aid for the difference between total and effective ventilation.

Cilia beat in a watery sol layer, moving an overlying gel layer of mucus upwards

A memory aid for the airway's mucociliary escalator.

The diaphragm alone at rest, with accessory muscles for forced inspiration and abdominals for forced expiration

A memory aid for which muscles are used in quiet and forced breathing.

Nitrogen splints alveoli open; replacing it with rapidly absorbed oxygen allows collapse

A memory aid for why high inspired oxygen causes collapse.

CPAP for oxygenation, BiPAP for ventilation

A memory aid for when to use CPAP and when to use BiPAP.

STOP-BANG for screening, Epworth for sleepiness, polysomnography to confirm

A mnemonic for screening and assessing obstructive sleep apnoea.

Repeated pharyngeal collapse causes intermittent hypoxia and arousals

A memory aid for the mechanism and consequences of obstructive sleep apnoea.

Obstruction traps gas and raises volumes; restriction reduces all volumes

A memory aid for the physiological differences between obstruction and restriction.

Occupation, travel, animals, hobbies and contacts

A memory aid for the exposures that change a differential diagnosis.

Automatic breathing is brainstem driven; voluntary breathing bypasses it through corticospinal tracts

A memory aid for the distinction between automatic and voluntary breathing.

Target saturations of 94 to 98 per cent, or 88 to 92 per cent if at risk of hypercapnia

A memory aid for prescribing oxygen safely.

Oxygen tension falls stepwise from atmospheric to about 1 kPa in the mitochondrion

A memory aid for the fall in oxygen tension from air to mitochondria.

Tension drives diffusion, saturation describes haemoglobin, content determines delivery

A memory aid for distinguishing oxygen tension, saturation and content.

From nasal cannulae to non-rebreathe and Venturi masks

A memory aid for the oxygen delivery devices and the concentrations they give.

Delivery equals cardiac output multiplied by arterial oxygen content

A memory aid for calculating oxygen delivery to the tissues.

A sigmoid curve with P50 of about 3.5 kPa or 27 mmHg

A memory aid for the shape and key points of the oxyhaemoglobin curve.

Acid, carbon dioxide, temperature and 2,3-DPG all shift it right

A mnemonic for what shifts the oxygen dissociation curve right.

Variable devices depend on the patient's breathing pattern; fixed devices do not

A memory aid for fixed and variable performance oxygen devices.

Costal, mediastinal, diaphragmatic and cervical pleura

A memory aid for the four named regions of the parietal pleura.

Effort dependent, compared with predicted or personal best

A memory aid for using and interpreting peak flow.

Resonant, dull, stony dull and hyperresonant

A memory aid for what each chest percussion note means.

Nitrous oxide is perfusion limited, carbon monoxide is diffusion limited, oxygen is normally perfusion limited

A memory aid for distinguishing perfusion-limited from diffusion-limited gas transfer.

Cheyne-Stokes waxes and wanes; Kussmaul is deep and rapid; Biot's is irregular

A memory aid for the abnormal breathing patterns and their causes.

Transudate is pressure, exudate is permeability

A memory aid for the causes of a pleural effusion by type.

Transudates from altered Starling forces; exudates from increased permeability

A memory aid for the formation and classification of pleural effusions.

Exudate or transudate first, then the specific tests

A memory aid for Light's criteria and the pleural fluid tests.

Parietal pleura is somatically innervated and painful; visceral pleura is autonomic and insensitive

A mnemonic for why parietal pleura hurts and visceral pleura does not.

Pleural pressure is more negative at the apex than at the base

A memory aid for the vertical gradient in pleural pressure.

Costodiaphragmatic and costomediastinal recesses

A memory aid for the pleural recesses and their clinical importance.

Coal, silica and asbestos, each with a characteristic pattern

A memory aid for the occupational dust diseases.

The context predicts the organism

A memory aid for which organism to expect in which patient.

Primary or secondary, with symptoms and size deciding treatment

A memory aid for classifying and treating a pneumothorax.

Loss of negative pleural pressure allows the lung to collapse and the chest wall to spring out

A memory aid for the physiological consequences of air in the pleural space.

It reverses the normal negative intrathoracic pressure, reducing venous return

A memory aid for the physiological consequences of positive pressure ventilation.

It makes ventilation more uniform while perfusion remains relatively unchanged

A memory aid for why proning improves oxygenation.

An indirect measure of left atrial pressure, obtained by occluding a pulmonary artery branch

A memory aid for what the wedge pressure measures.

Low pressure, low resistance, high compliance, and it constricts in hypoxia

A memory aid for how the pulmonary circulation differs from the systemic.

Score first, then D-dimer or CT pulmonary angiogram

A memory aid for the Wells score and the PE diagnostic pathway.

Increased dead space, hypoxaemia from mismatch, and right ventricular strain

A memory aid for the physiological consequences of pulmonary embolism.

Five groups, defined by the cause rather than the pressure

A memory aid for the five groups of pulmonary hypertension.

Two wavelengths distinguish oxyhaemoglobin from deoxyhaemoglobin in pulsatile blood

A memory aid for how pulse oximetry works and when it misleads.

Medullary dorsal and ventral groups, with pontine pneumotaxic and apneustic centres

A memory aid for the brainstem centres controlling breathing.

Hands, face, neck, then chest front and back with the same four steps

A memory aid for the order of a respiratory examination.

Type 1 is hypoxaemia alone; type 2 adds hypercapnia

A memory aid for distinguishing type 1 from type 2 respiratory failure.

Carbohydrate 1.0, protein 0.8, fat 0.7, mixed diet about 0.8

A memory aid for the respiratory quotient of different fuels.

Respiratory rate

The number of breaths per minute.

Lung borders cross ribs 6, 8 and 10; pleural borders cross ribs 8, 10 and 12

A mnemonic for the surface markings of the lung and pleural borders.

Non-caseating granulomas affecting any organ, most often the lung

A memory aid for the multisystem features of sarcoidosis.

Rate, accessory muscles, recession, position and the ability to speak

A memory aid for recognising increased work of breathing.

Ventilation falls, carbon dioxide rises slightly and upper airway tone is reduced

A memory aid for the respiratory changes during sleep.

Impaired clearance, carboxyhaemoglobin, protease imbalance and accelerated decline in FEV1

A memory aid for the physiological effects of cigarette smoking.

Obstructive lowers the ratio; restrictive lowers both values proportionately

A memory aid for distinguishing obstructive from restrictive spirometry.

Peripheral oxygen saturation

An estimate of haemoglobin oxygen saturation measured by pulse oximetry.

Reduces surface tension, increases compliance, stabilises alveoli and keeps them dry

A memory aid for the roles of pulmonary surfactant.

Time constant equals resistance multiplied by compliance

A memory aid for how compliance and resistance determine filling and emptying.

Sixteen to twenty C-shaped cartilages, open posteriorly and bridged by the trachealis muscle

A memory aid for the structure of the trachea and why its cartilages are incomplete.

TLCO measures diffusion; KCO corrects it for the volume available

A memory aid for interpreting the gas transfer factor.

Alveolar pressure minus pleural pressure

A memory aid for the pressure that actually inflates the lung.

Lateral border of pectoralis major, anterior border of latissimus dorsi, and a line above the fifth intercostal space

A memory aid for the boundaries of the safe triangle for chest drain insertion.

Chronic cough, weight loss, night sweats and upper lobe cavitation

A memory aid for the presentation of pulmonary and extrapulmonary tuberculosis.

Smear, culture and NAAT for active disease; Mantoux and IGRA for latent

A memory aid for the tests used in latent and active tuberculosis.

Type 1 is a gas exchange problem, type 2 a ventilation problem

A memory aid for classifying respiratory failure and its causes.

Hypoxic, anaemic, stagnant and histotoxic

A mnemonic for the four classes of tissue hypoxia.

Dependent regions receive more ventilation and more perfusion in the spontaneously breathing patient

A memory aid for how posture changes the distribution of ventilation and perfusion.

A ratio of zero is shunt; a ratio of infinity is dead space

A memory aid for the V/Q ratio and its extremes.

Carbon dioxide is the dominant drive, sensed centrally through cerebrospinal fluid pH

A memory aid for the main stimulus to breathing.

Alveolar pressure dominates at the apex, arterial pressure at the base

A memory aid for the three zones of pulmonary blood flow.

Elastic work plus resistive work, minimised at an optimal respiratory rate

A memory aid for the components of the work of breathing.