Values in [square brackets] are American
Most values are approximate.

L = litre.
N = normal.
Δ = change.


μ micro-, prefix indicating 10-6, i.e. 0.000001.

μm see micrometer.

ΔV/ΔP change in volume in response to change in pressure, i.e. compliance.

6MD - six-minute distance

A - alveolar, e.g. PAO2.

a - arterial, e.g. PaO2.

AAA - abdominal aortic aneurysm.

ABGs - arterial blood gases.

ABPA - allergic bronchopulmonary aspergillosis.

Absorption atelectasis - alveolar collapse due to either resorption of air distal to a bronchial obstruction or excess administration of O2 which is then absorbed.

ACBT - active cycle of breathing techniques.

ACE inhibitors - angiotensin-converting enzyme inhibitor drugs.

Acidemia - acidosis of blood.

Acidosis - pH < 7.35.
- Respiratory acidosis is caused by malfunctioning respiration.
- Metabolic acidosis is caused by malfunctioning metabolism.

Acinus - portion of lung participating in gas exchange, supplied by a primary respiratory bronchiole.

ACPRC - Association of Chartered Physiotherapists in Respiratory Care.

AD - autogenic drainage.

ADL - activities of daily living.

Adult respiratory distress syndrome - old terminology for acute respiratory distress syndrome.

Adventitious sounds - added sounds on auscultation.

Aerosol - suspension of solid or liquid particles, e.g. pollen, dust, smoke, mist, viruses, therapeutic aerosol for humidification or drug delivery.

AF - atrial fibrillation

Air trapping - retention of inspired gas.

Airway - (1) path that air travels from atmosphere to alveoli, or (2) device to hold natural airway open for relief of obstruction or to allow mechanical ventilation.

Airway closure - closure of small airways, common in dependent lung regions at end-expiration.

Airway (alveolar) pressure - pressure inside the lung.

Airways resistance
- N: 0.5-3.0 cmH2O/L/sec.

Albumin - plasma protein responsible for providing most osmotic pressure in blood.
- N: 40-60 g/L, [4.0-6.0 g/100ml].

Alkalemia - alkalosis of blood.

Alkalosis - pH > 7.45.
- Respiratory alkalosis is caused by malfunctioning respiration.
- Metabolic alkalosis is caused by malfunctioning metabolism.

Alveolar-arterial oxygen gradient - see PAO2−PaO2.

Alveolar ventilation (mL/min) - (tidal volume – physiologic dead space) x respiratory rate.

Anabolism - constructive phase of metabolism when simple substances become complex living matter.

Anaerobic threshold - highest O2 consumption during exercise, above which sustained lactic acidosis occurs.
- Measured by expired gas.
- Exercise training can increase AT by 25-40%.

Anastomosis - surgical union of tubular structures.

Angina - crushing chest pain due to impaired blood supply to the myocardium, worsened with exertion or stress.

Angioplasty - invasive but non-surgical dilation of coronary artery stenosis, using catheter via femoral puncture, or laser.

Anoxia - synonymous with hypoxia, but implying a more complete O2 lack.

Antibody - substance produced by interaction of antigen with body's defences.
- also known as immunoglobulin.

Antigen - allergen, i.e. irritant that elicits an immune response.

APACHE Acute Physiology And Chronic Health Evaluation: scoring system to measure severity of illness, using predictor variables such as diagnosis, age and physiological measures.

APTT - see clotting studies.

Apgar score - scoring system to measure birth asphyxia, using a combination of heart rate, respiratory effort, muscle tone, reflex irritability and colour.

Apneustic breathing - prolonged inspiration, usually due to brain damage.

Apnoea - absence of breathing for > 10 seconds.

ARDS - acute respiratory distress syndrome.

ARF - (1) acute respiratory failure, or (2) acute renal failure

Arnold’s nerve - auricular branch of the vagus nerve, responsible for Arnold’s cough reflex in 4.2% of the population (Gupta 1986), whereby a cough can be facilitated by ear stimulation; also responsible for ear pain being an occasional early presentation of laryngeal cancer.

Arteriovenous oxygen difference - difference between O2 delivered to and returning from tissues.
- Calculated from arterial and mixed venous blood samples.
- Related to metabolic rate.

Ascites - fluid in the abdominal cavity.

Aspiration - (1) inhalation of unwanted substances (e.g. gastric acid or sea water) into lungs, or (2) therapeutic removal of fluid or gas from a cavity such as the pleural space.

Asystole - no heartbeat.

Auscultation - use of stethoscope to hear sounds from a body cavity.

Base deficit - negative base excess.

Base excess - minus 2 to plus 2 mmol/L

Bicarbonate ion concentration (HCO3-)
- normal: 22-26 mmol/L
- metabolic acidosis: < 22 mmol/L
- metabolic alkalosis: > 26 mmol/L.

Biot's respiration - irregular cycles of deep gasps and apnoea.

BiPAP - bilevel positive airways pressure.

BIPAP - biphasic positive airways pressure.

Bleb - collection of extra-alveolar air under visceral pleura (see also bulla).

Bohr effect - reduced availability of O2 from oxyhaemoglobin in regions of low PCO2.

Bohr equation - difference between end-tidal and arterial PCO2.
- Calculates physiological dead space.

BOOP - Bronchiolitis obliterans organising pneumonia.
- Occurs secondary to lung or bone marrow transplant, drug reaction, aspiration or collagen vascular disease.

Bradycardia - slow heart rate

Bradypnoea - slow breathing.

Bronchial breathing - abnormal sound on auscultation that is characterised by long expiration, a pause between inspiration and expiration and a hollow blowing quality on expiration. It indicates loss of functioning lung volume.

Bronchiole - airway unsupported by cartilage.

Bronchitis - acute or chronic inflammation of mucus membranes of tracheobronchial tree.

Bronchomalacia - disorder characterised by degeneration of elastic and connective tissue of trachea and bronchi.

Bronchopleural fistula - communication between lung and pleura, caused by thoracic surgery, trauma, mechanical ventilation or pulmonary disease.

Bronchorrhoea - excess production of watery sputum, > 100mL/day.

Bronchospasm - abnormal contraction of smooth bronchial muscle, causing narrowing of airway.

Buffer - substance that binds or releases hydrogen ions in order to keep pH constant.

Bulla - collection of air in lung tissue which is more than 1 cm in diameter, caused by alveolar destruction.

CABG - coronary artery bypass graft.

Cachexia - severe wasting, i.e. loss of muscle due to increased proteolysis, e.g: cancer, heart failure, rheumatoid arthritis, COPD and renal failure

Calcium - N: 2.2-2.6 mmol/L.

Catabolism - metabolic process releasing energy and CO2.

CaO2 - see oxygen content.

Cardiac enzymes - enzymes released from damaged heart muscle after myocardial infarction.

Cardiac index - cardiac output / body surface area.
- N: 2.5-3.5 L/min/m2.
- Highest at age 10, then decreasing with age.

Cardiac output (CO or Q)- blood ejected by left ventricle per minute, i.e. heart rate x stroke volume.
- N: 4-8 L/min at rest, up to 25 L/min on exercise.

Cardioplegia - cooling of heart to reduce metabolic rate during surgery.

Catabolism - destructive phase of metabolism, when large molecules are converted into small molecules.

Catecholamine - compound having sympathomimetic action, e.g. adrenaline.

CCF - congestive cardiac failure.

CF - cystic fibrosis.

CFA - cryptogenic fibrosing alveolitis.

Chest wall - structures outside lung that are involved in breathing movements, i.e. rib cage, diaphragm and abdominal wall.

Churg-Strauss Syndrome - rare disease in people with severe asthma, comprising multi-organ necrotising arteritis, with 5-year survival of 50%

Chylothorax - effusion of chyle from thoracic duct into pleural space.

CI - see cardiac index.

Closing capacity - lung volume at which airway closure begins, due to narrowing of dependent airways as lung deflates.
- Rises with age as small airways narrow, equalling FRC at an average 44 years in supine and 66 years in standing.

Closing volume - closing capacity minus residual volume. Increases (becomes a greater proportion of FRC) with small airways disease, smoking, obesity and extremes of age.
- N: 10% of VC in young people with normal lungs.
- Age 65: 40% of VC.

Clotting studies:
- ACT (activated clotting time). N: 100-140 sec.
- APTT (activated partial thromboplastin time). N: 30-40 sec.
- Bleeding time. N: 3-9 mins.
- FDPs (fibrinogen degradation products). N: < 10 mg/ml.
- Fibrinogen level. N: >150 mg/dL.
- INR (international normalised ratio). N: 1-1.4. Higher means increased clotting time and risk of bleeding.
- KPTT (kaolin partial thromboplastin time). N: < 7 s above control.
- Platelet count. N: 140,000-400,000 mm-3. Risk of bleeding with suction: < 50,000 mm-3. Spontaneous bleeding: < 20,000 mm-3.
- PT (prothrombin time). N: 12-15 s.
- PTT (partial thromboplastin time). N: 12-30 s.

CMV - (1) controlled mandatory ventilation or conventional mechanical ventilation, or (2) cytomegalovirus (virus in the herpes group).

CO - (1) cardiac output, or (2) carbonmonoxide.

CO2 - carbondioxide.

Coagulation - see clotting studies.

Collateral ventilation - exchange of inspired gas between adjacent lung units.

Colonisation - presence and multiplication of microorganisms without necessarily causing tissue damage.

Colostomy - surgical creation of opening into large bowel.

Coma - unrousable unconsciousness.

Compliance of lung - change in volume in response to change in pressure.
- N static compliance: 200 mL/cmH2O. N dynamic compliance: 180 mL/cmH2O.
- N compliance in patient on IPPV: 35-50 mL/cmH2O.

Compliance of lung measured on IPPV - tidal volume/plateau airway pressure-PEEP.

Consolidation - replacement of alveolar air by substance of greater density.

Contralateral - opposite side.

COPD - chronic obstructive pulmonary disease

Cough syncope - loss of consciousness for a few seconds following cough.
- Sometimes occurs in middle-aged men with COPD.
- Benign unless while driving.

CPAP - continuous positive airways pressure.

CPR - cardiopulmonary resuscitation.

Creatinine - electrolyte in plasma or urine, formed from muscle breakdown and excreted by kidneys.
- N in plasma: 50-100 μmol/L [0.6-1.2 mg/100mL].
↑ in hypovolaemia or kidney failure, ↑↑ in septic shock.

Cryptogenic - of unknown cause.

Cryptogenic organising pneumonia - see BOOP.

CSF - cerebrospinal fluid.

CT - computed tomography.

CVP - central venous pressure.
- N: 1-7 mmHg or 5-12 cmH2O.

CvO2 - see mixed venous oxygen content.

CXR - chest x-ray.

Cytokine - inflammatory product.

DB - deep breathing.

Decubitus - lying down.
- Right decubitus – lying on right side.
- Left decubitus – lying on left side.

Deglutition - swallowing.

Delirium - potentially reversible disorder of cognition and attention, including disorientation, fear, misperception and hallucination.

DIC - disseminated intravascular coagulation.

DNR - do not resuscitate.

DO2 - see oxygen delivery.

Doppler - use of changes in frequency of light and sound waves to monitor relative motion.

Duty cycle (TI/TTOT) - ratio of inspiratory time to total respiratory cycle time. Short TI in relation to TTOT indicates decreased VT and ↑ dead space, suggesting inspiratory muscle fatigue.
- See also tension-time index

DVT - deep vein thrombosis.

Dysphagia - difficulty swallowing.

ECCO2R - extracorporeal CO2 removal.

ECG - electrocardiogram.

ECMO - extracorporeal membrane oxygenation.

-ectomy - removal.

Eisenmenger syndrome - pulmonary vascular disease with cyanosis due to extrapulmonary shunt in which congenital heart disease causes systemic-to-pulmonary circulation connection.

Elastance - opposite of compliance.

EMD - electromechanical dissociation: dissociation of electrical and mechanical activity of the heart, represented by clinical signs of cardiac arrest with normal ECG.
- Causes include tension pneumothorax, cardiac trauma or severe electrolyte or acid-base imbalance.
- Leads to full cardiac arrest.

Endurance - capacity of muscle to sustain contraction.

Enteral - via the gut.

Entrainment - dilution of a gas stream or aerosol with external gas such as room air.

Eosinophilia - excess eosinophils. Indicates allergic state.

Eosinophils - inflammatory cells associated with hypersensitivity reactions.
- ↑ in allergy e.g. extrinsic asthma.

Epiglottis - cartilage which diverts food to oesophagus by closing over trachea.

ERV - expiratory reserve volume

Erythrocytosis - polycythaemia.

ETCO2 - end-tidal CO2.
- N: 4-6%.

ETT - endotracheal tube.

Eucapnia - normal PaCO2.

Extracorporeal - outside the body.

Fatigue - abnormal tiredness after normal activity, or decreased energy that prevents activity which needs sustained effort.

FBC - full blood count.

FDP - see clotting studies.

FEF25-75 - forced expiratory flow in middle half of expiration.

FEF50 - as above.

FET - forced expiration technique.

FEV1 - forced expiratory volume in one second.

FEV1/FVC - FEV1 in relation to vital capacity

FFP - fresh frozen plasma.
- Frozen within six hours of donation.
- Contains all clotting factors at normal concentration.

FH - family history.

First-pass metabolism - metabolism of a drug other than systemically, due to insufficient absorption or metabolism by gut or liver before drug enters systemic circulation.

FIO2
- fraction of inspired oxygen
- examples: FIO2 of 0.6 = 60% inspired oxygen, FIO2 of 0.21 = room air.

Fluid compartments - extracellular space (14L) and intracellular space (28L). Extracellular space is subdivided into vascular (4L) and interstitial (10L) spaces.

Fluid overload - 10% or greater increase in weight due to excess fluid.

FRC - functional residual capacity.

FVC - forced vital capacity.

GCS - Glasgow Coma Scale.

Generation - branches of tracheobronchial tree, numbering between 10 and 23.

Glottis - the vocal folds and the space in between them

Glucose level in blood
- N: 3.0-5.5 mmol/L.
- ↑ in stress, ↑↑ in diabetis mellitus, decreased in liver failure or starvation.

GOR - gastroesophageal reflux.

Gram-negative pathogenic bacteria - virulent organisms which thrive in moist environments, e.g: Haemophilus, Klebsiella, Pseudomonas, Salmonella.

Haematocrit - concentration of red blood cells in blood.
- N in women: 36-46% in women, N in men: 40-50%.
- Anaemia: < 36%. Polycythaemia: > 55%.

Haemoglobin - respiratory pigment in red blood cells which combines reversibly with oxygen.
- N in women: 11.5-15.5 g/100 mL, N in men: 14.0-18.0 g/100 mL.
- Decreased in anaemia, ↑ in polycythaemia.

Hamman's sign - crunching sound synchronous with heart beat, indicating pneumomediastinum.

Harrison's sulcus - permanent indentation of the chest wall along the costal margins where the diaphragm inserts, caused by pull of diaphragm on ribs which are either not yet calcified or weakened by rickets.

Hartmann's solution - fluid and electrolyte replenisher.

Hb - haemoglobin.

HCO3- - see bicarbonate ion concentration.

Hepatomegaly - enlarged liver.

HF - heart failure

Hiccup - involuntary clonic spasm of intercostals and diaphragm followed by abrupt glottic closure, of unknown aetiology.

Hickman line - central venous access line, e.g. for chemotherapy.

HIV - human immunodeficiency virus.

H:L ratio - ratio of power in high and low frequency bands of electromyogram of respiratory muscle.  with respiratory muscle fatigue.

HME - heat-moisture exchanger.

HR - heart rate.
- N: 60-100/min.

HRCT - high resolution computed tomography.

HRQL - health-related quality of life

Humoral - non-cellular.

HVS - hyperventilation syndrome

Hypercapnia/hypercarbia
- reduced CO2 in arterial blood.

Hyperdynamic - status signalling onset of septic shock: galloping pulse, pyrexia, shaking chill, flushing of skin, high cardiac output, unstable BP.

Hyperkalaemia - ↑ potassium.

Hypermetabolism - ↑ basal energy expenditure by > 10%.

Hypernatraemia - ↑ serum sodium.

Hyperosmolar - containing high concentration of osmotically active ingredients.

Hyperoxia - abnormally high oxygen tension in blood.

Hyperreactivity - heightened sensitivity to variety of stimuli. Present in airways with asthma. Sometimes present with COPD, bronchiectasis, CF, sarcoidosis, LVF.

Hyperthermia - core temperature > 40.5oC.

Hyperventilation - CO2 removal in excess of CO2 production, causing PaCO2 < 4.7 kPa (35 mmHg).

Hypocapnia/hypocarbia
- reduced CO2 in arterial blood.

Hypogammaglobulinaemia - reduced gamma globulin in blood, associated with reduced resistance to infection.

Hypokalaemia - reduced potassium.

Hyponatraemia - reduced sodium.

Hypopnoea - shallow slow breathing.

Hypoventilation - CO2 production in excess of CO2 removal, leading to PaCO2 > 6.0 kPa (45 mmHg).

Hypoxaemia
- reduced oxygen in arterial blood
- PaO2 < 8 kPa (60 mmHg) or SaO2 < 90%.

Hypoxia
- reduced oxygen at tissue level so that cells are experiencing anaerobic metabolism (hypoxia is more relevant to body function than hypoxaemia but is more difficult to measure).

Hysteresis - difference in compliance between inspiration and expiration.

IABP - intra-aortic balloon pump.

Iatrogenic - causing or exacerbating harm by medical intervention.

ICP - intracranial pressure.

ICU - intensive care unit.

Idiopathic - of unknown cause.

I:E - see inspiratory:expiratory ratio.

Ileostomy - surgical creation of opening into ileum.

Ileus - gut obstruction, e.g. due to paralytic ileus.

Immotile cilia syndrome - primary ciliary dyskinesia.

Immunoglobulin - antibody. Examples in respiratory secretions: IgA, IgE, IgG, IgM.

Infarct - death of tissue due to lack of blood supply.

Infection - presence of microorganisms or their products in normally sterile tissue (see also sepsis).

Infiltrate - fluid, cells or other substance in fluid or tissue space. E.g. pulmonary interstitial infiltrate = fluid between capillary and alveolus, showing on x-ray as diffuse shadowing.

INR - see clotting studies.

Inspiratory capacity - volume inspired during maximum inspiration from resting end-expiratory position.

Inspiratory:expiratory ratio - duration of inspiration relative to expiration.

Inspiratory force - see MIP.

Inspissated - thick.

Intracranial hypertension ↑ ICP.

Intrapulmonary pressure - alveolar pressure.

Intrathoracic pressure - pleural pressure.

Intrinsic PEEP - trapped gas left in a patient’s lungs at the end of exhalation, unintentionally, due to obstructed airways and breathing through artificial airways (p.)

IPPB - intermittent positive pressure breathing, i.e. a form of noninvasive ventilation that provides pressure support on inspiration only, e.g. the Bird.

IRV - inspiratory reserve volume

IPPV - intermittent positive pressure ventilation, i.e. mechanical ventilation.

Ipsilateral - same side.

IRT - immune reactive trypsin: antibody identified in CF screening.

IRV - inspiratory reserve volume.

IS - incentive spirometry.

Isotonic - exerting same osmotic pressure as body fluids, e.g: isotonic saline contains salt equal to that in body.

Isotonic exercise - active exercise with movement, force of contraction remaining constant.

IV - intravenous.

JVP - jugular venous pressure.

K - potassium.

Kartagena's syndrome - triad of bronchiectasis, sinusitis and situs inversus, associated with primary ciliary dyskinesia.

Kerley B lines - thin 1-2 cm horizontal lines on x-ray that abut the visceral pleural surface, representing engorged lymphatics and thickened interlobular septa, indicative of pulmonary oedema. Become visible when the pulmonary artery wedge pressure exceeds 25 mmHg.

kPa - kilopascal.

KTPP - see clotting studies.

Kussmaul breathing - deep sighing breathing often seen in patients with metabolic acidosis.

Kyphoscoliosis - anteroposterior and lateral curvature of spine.

Lactate (in blood) - serum lactate. N: < 1 mmol/L.
- Severe oxygen debt and poor prognosis: 2.5-3.0.

Lactic acidosis - elevation of blood lactate due to insufficient oxygen in tissues for body's needs, causing metabolic acidosis.
- See also anaerobic threshold.

Laparoscopy - minimal access incision through abdominal wall.

Laparotomy - full surgical incision through abdominal wall.

Laplace's Law - The pressure developed by diaphragmatic contraction is directly proportional to tension developed in its fibres and inversely proportional to its radius of curvature.

Laminar - streamline.

Larynx - cylindrical tube connecting pharynx and trachea, formed by cartilages and containing vocal cords.

Leukocyte - white blood cell.

Leukocytosis - ↑ white blood cells.

LFT - (1) lung function test, or (2) liver function test.

Locked-in syndrome - total paralysis below third cranial nerve, with patient partially or fully aware.

LTOT - long term oxygen therapy.

LVEDP - left ventricular end-diastolic pressure.

LVEDV - left ventricular end-diastolic volume.
- Determinant of preload.
- Depends on venous return to L ventricle, circulating blood volume and efficiency of left atrial contraction.
- Measured, by assumption, from PAWP, which relates to LVEDP.

LVF - left ventricular failure.

Lymphangioleiomyomatosis - overgrowth of smooth muscles around airways, blood vessels and lymph vessels, leading to cysts in the lung

Lymphocyte - small leucocytes comprising 25% total white blood cell count.

-lysis - breakdown.

MAP - see mean arterial pressure.

Mast cells - connective tissue cells involved in hypersensitivity reactions. Release histamine in response to specific stimuli. ↑ in asthma.

MCV - see mean corpuscular volume.

MDI - metered dose inhaler.

Mean arterial pressure - average pressure pushing blood through systemic circulation, i.e: systolic BP + (diastolic BP x 2)/3
- N: 80-100 mmHg. Compromised circulation to vital organs: < 60 mmHg. Compromised circulation to injured brain: < 80 mmHg.

Mean corpuscular haemoglobin - amount of Hb in red blood cells.

Mediastinum - part of thoracic cavity between the pleural sacs containing the lungs. Contains all thoracic viscera except the lungs.

MEF50 - maximum expiratory flow in mid-expiration.

Mendelson's syndrome - aspiration of gastric contents into lungs.

MEP - maximal expiratory pressure. N: 100 cmH2O. Inadequate cough: < 40 cmH2O.

mEq - milliequivalent, i.e. one thousandth of molecular weight of substance.

mEq/L - milliequivalents per L of solution. Electrolyte concentration, also expressed as mmol/L.

MEP - maximum expiratory pressure.

MET - metabolic energy expenditure.
- Metabolic unit representing oxygen consumed at rest.
- Basal metabolism consumes one MET, eating consumes two METs, dressing consumes three METs, vacuuming consumes five METs, brisk 30-60 min walk consumes 9-10 METs. N: 3.5 ml oxygen/kg body weight/min.

Metabolism - chemical processes of body, comprising anabolism and catabolism. Varies with healing, activity level and temperature.

MI - see myocardial infarction.

Micrometer - one millionth of a metre (μm).

Micron - old term for micrometer (see above).

Miliary TB - homogenous TB of lung manifest by mottling on x-ray.

Minute ventilation or minute volume (mL/min) - ventilation per minute, i.e. tidal volume x respiratory rate.

MIP - maximum inspiratory pressure: assessment of respiratory muscle strength.
- N: minus 100-130 cmH20 (men), minus 70-100 (women).
- Typical value for hypercapnic COPD: minus 55 (men), minus 40 (women).
- Poor weaning outcome: minus 20.
- Inadequate cough: minus 0-20.

Mixed venous blood - blood in pulmonary artery.

Mixed venous oxygen content - (Hb x SvO2 x 1.39) + (PvO2 x 0.023).

Mixed venous oxygen saturation - N: 75%. (see SvO2)

MMEF- maximum mid-expiratory flow.

mmHg - millimetres of mercury.

mmol - millimol, i.e. one one-thousandth of molecular weight of substance.

MMV - mandatory minute ventilation.

MRI - magnetic resonance imaging

MRSA - methicillin-resistant staphylococcus aureus

Mucoactive - affects quality or quantity of mucus.

Mucokinetic - accelerates mucus transport.

Mucolytic - destroys mucin in mucus gel.

Mucoviscidosis - cystic fibrosis.

MV - minute ventilation or volume (see VE).

Mycoplasma pneumonia - atypical pneumonia which affects otherwise healthy people rather than the chronically ill or elderly.

Myocardial infarction - death of portion of heart muscle due to myocardial ischaemia.

Na - see sodium.

Neutropenia - reduced neutrophils, i.e. < 1.5 x 109.

Neutrophil - white blood cell used for phagocytosis of bacteria but which in excess releases tissue-damaging enzymes as part of uncontrolled inflammation.

Neutrophilia - ↑ neutrophils.

NFR - not for resuscitation.

NICE - National Institute for Clinical Excellence.

NICU - neonatal intensive care unit.

NIPPV - nasal (or noninvasive) intermittent positive pressure ventilation, i.e. noninvasive ventilation.

NIV - noninvasive ventilation.

NO - nitric oxide.

Nociceptive - painful.

Normocapnia - normal PaCO2.

O2 - oxygen.

Occupational lung disease - disease due to inhalation of dust, particles, fumes or gases while working.

OER - see oxygen extraction ratio.

Oliguria - reduced urine output, i.e. < 20 mL/hour (normal 50-60 mL/hr).

Orthostatic - relating to erect position.

Orthostatic hypotension - drop of more than 20 mmHg in systolic and/or a drop of more than 10 mmHg in diastolic blood pressure on standing.

Orthotopic transplantation - replacement of recipients' organ with that of donor.

-oscopy - visual examination of interior of organ.

Osmolality - number of osmotically active particles per kg of solvent.

Osmolar load - osmolality of solution x volume infused.

Osmolarity - number of osmotically active particles per litre of solution.

-ostomy - formation of artificial opening to skin surface.

-otomy - incision.

Oxygen consumption - amount of oxygen consumed by tissues each minute, i.e. CI x (CaO2-CvO2) x 10 mL/min/m2.
- N at rest: 200-250 mL/min (if contributing values normal, i.e. CO 5 L/min, Hb 15 g/100ml, SaO2 97%, SvO2 75%).
- Critical illness: 600 mL/min.
- Maximum on exercise in unfit male: 3600 ml/min.
- Maximum on exercise in fit male: 5000 mL/min.

Oxygen content (CaO2) - total amount of oxygen in blood, i.e. (Hb x SaO2 x 1.39) + (PaO2 x 0.023).
- N in arterial blood: 17-20 mL/100mL.

Oxygen cost of breathing - energy requirements of respiratory muscles.
- Provides indirect measure of work of breathing.
- N: one mL/L of ventilation.

Oxygen delivery (DO2) volume of oxygen presented to tissues, i.e. CI x CaO2.
- N: 550-650 mL/min/m2.
- May be elevated in hyperdynamic states.

Oxygen demand - oxygen needed by cells for aerobic metabolism, estimated by VO2.

Oxygen extraction - oxygen transferred from blood to tissues, i.e. CaO2 difference between arterial and mixed venous blood, equivalent to VO2/DO2.
- N 22-32%
- 32% indicates ↑ oxygen demand or occasionally reduced DO2
- < 22% indicates damaged tissues unable to extract O2,or a hyperdynamic circulation e.g. early sepsis

Oxygen extraction ratio - ratio of oxygen consumption to oxygen delivery (VO2/DO2), indicating efficiency of tissues in extracting oxygen.
- Calculation: CaO2 - CvO2/CaO2
- N: 25%. High oxygen extraction to meet excess metabolic needs: > 35%. Maximum OER: 60-70% for most tissues.

Oxygen flux - % oxygen that reaches tissues.

Oxygen transport - Transport of oxygen from lungs to mitochondria.

Oxygen uptake - oxygen consumption.

Ozone - gas that provides protective layer to earth's atmosphere, but at ground level causes inflammation in hyperreactive airways.

P50 - PO2 at which 50% of haemoglobin in blood is saturated with oxygen.
- N: 27-28 mmHg.

PA-aO2 - alveolar-arterial oxygen gradient, i.e. difference in oxygen tension across the alveolar membrane, i.e. PAO2 minus PaO2.
- Indicates efficiency of gas transfer.
- Varies with FIO2.
- N on room air: 0.7-2.7 kPa (5-20 mmHg), reflecting normal anatomical shunt.
- ↑ with diffusion impairment, eg. pulmonary oedema, fibrosis, ARDS , ↑ on exercise, ↑ in the elderly, ↑ on supplemental oxygen.
- PA-aO2 > 3.0 kPa suggests impaired gas exchange.

Pack years - average number of packs smoked daily multiplied by years smoked, e.g. smoking one pack/day for 30 years = 30 pack-year history.

Packed cell volume - equivalent to haematocrit.
- N: 0.36 - 0.46 (women), 0.40 - 0.50 (men).
- ↑ in polycythaemia, reduced in anaemia.

PaCO2 - partial pressure of CO2 in arterial blood.
- N: 4.7-6.0 kPa (35-45 mmHg).

Palliation - alleviation of symptoms.

PAO2 - partial pressure of oxygen in alveoli.

PaO2 - partial pressure of oxygen in arterial blood.
- N: 11-14 kPa (80-100 mmHg).

PaO2:FIO2 - ratio of PaO2 to inspired oxygen.
- Estimates shunt, similar to PA-aO2 but easier to use.
- N: 40 kPa (300 mmHg).
- More relevant than FIO2 alone.
- e.g: PaO2:FIO2 of 27 could mean PaO2 of 10.7 kPa at FIO2 of .40 or PaO2 of 16 kPa at FIO2 of .60.

PAOP - pulmonary artery occlusion pressure (= PAWP).

PAP - peak airways pressure (= peak inspiratory pressure).
or:
PAP pulmonary artery pressure.
- N: 10-20 mmHg (systolic 22, diastolic 10, mean 15).
- Pulmonary hypertension: 25 mmHg.

Paralytic ileus - decrease or absence of peristalsis.

Parenchyma - foamlike substance comprising the gas exchanging part of lung, made up of alveoli, small airways, capillaries and supporting tissue.

Parenchymal lung disease - disease affecting parenchyma, e.g. interstitial lung disease, pneumonia, TB, ARDS.

Parenteral - other than through the gut.

Pathogen - bacteria, viruses, etc, which can cause disease.

PAWP - pulmonary artery wedge pressure.
- N: 5-15 mmHg.
- Pulmonary congestion: 20 mmHg.
- Pulmonary oedema: 25 mmHg.

Paw - mean airway pressure.

PC - pressure contolled ventilation.

PCA - patient controlled analgesia.

PCIRV - pressure-controlled inverse-ratio ventilation.

PCP - pneumocystis carinii pneumonia.

PCV - see packed cell volume.

PCWP - pulmonary capillary wedge pressure (= PAWP).

PD - postural drainage.

PE - pulmonary embolus.

PEEP - positive end-expiratory pressure.

PEFR - peak expiratory flow rate, i.e. peak flow.

PEmax - maximum expiratory pressure at mouth.
See MEP.

PEP - positive expiratory pressure.

Percussion - (1) (therapeutic) clapping the chest wall to loosen secretions, or (2) (diagnostic) tapping chest wall to identify density of underlying tissue.

Percutaneous - through the skin.

Petechiae - small skin haemorrhages.

pH - inverse of log of hydrogen ion concentration.
- Measure of hydrogen ions in solution.

Phlebotomy - therapeutic withdrawal of blood.

PICU - paediatric intensive care unit.

PIE - pulmonary interstitial emphysema.

PIF - peak inspiratory flow.
- N: 40-50 L/min.
- Breathlessness or exercise: up to 200 L/min.

PIFR - peak inspiratory flow rate (= peak inspiratory flow).

PImax - maximum inspiratory pressure at the mouth. See MIP.

PIP - peak inspiratory pressure.

Plasma colloid osmotic pressure
- N: 3.4 kPa (26 mmHg).
- Risk of pulmonary oedema: 1.45 kPa (11 mmHg).

Plasma osmolarity - N: 280-300 m osmol/L.

Plasmapheresis - plasma exchange.

-plasty - reconstruction.

Platelet count - see clotting studies.

Platypnoea - difficulty breathing while sitting up.

Plethoric - florid complexion due to excess red blood cells.

Pleural (intrapleural/intrathoracic) pressure - pressure in the pleural space.

PN - percussion note.

Pneumectomy - lung volume reduction surgery (cf.pneumonectomy, see index).

Pneumomediastinum - air in mediastinum.

Pneumonitis - inflammation of lung tissue due to chemical or physical insult.

Pneumopericardium - air in pericardium.

PO2 - partial pressure or tension of oxygen.

Polychondritis - inflammation and destruction of cartilagious structures including tracheobronchial tree.

Polycythaemia - Excess red blood cells due to late-stage lung disease, cyanotic congenital heart disease, high-altitude living or sleep apnoea.

Polysomnography - recording of physiological parameters during sleep.

Polyuria - ↑ urine output, i.e. > 100 mL/hr.

POMR - problem oriented medical record.

Postural hypotension - Drop in BP of > 5 mmHg on moving to upright position

Potassium (K)- electrolyte in plasma or urine.
- N in plasma: 3.5-5.0 mmol/L.

Poudrage - pleurodesis.

PS - pressure support ventilation.

Psittacosis - infectious disease of birds transmitted to humans, causing atypical pneumonia.

PT - see clotting studies.

PTCA - percutaneous transluminal coronary angioplasty.

PtcCO2 - transcutaneous CO2 tension.

PtcO2 - transcutaneous oxygen tension.

PTT - see clotting studies.

Pulmonary hypertension - ↑ pulmonary artery pressure, i.e. > 25 mmHg (mean) at rest or 30 mmHg on exercise in presence of cardiac output < 5 L/min.

Pulmonary osteoarthropathy - pain and swelling of joints associated with lung, liver and congenital heart disease.

Pulmonary vascular resistance
- N: 25-125 dyn.s.cm-5.

Pulse pressure - difference between systolic and diastolic pressures: indicates blood flow.
- N: 40-70 mmHg. ↑ with hypertension, decreased with poor stroke volume.
- Dangerously low tissue perfusion: 20 mmHg.

Pulsus paradoxus - weaker pulse on inspiration than expiration caused by expansion of pulmonary vascular bed on inspiration. i.e. excess negative pressure in chest, e.g. severe acute asthma, hypovolaemic patient on IPPV, cardiac tamponade.
- N: 10 mmHg, higher value indicating laboured breathing.

Pump, ventilatory/respiratory - components of breathing mechanism, comprising respiratory centres, muscles and nerves of respiration, chest wall.

PVD - peripheral vascular disease.

PvCO2 - mixed venous CO2 tension.
- N: 6.1 kPa (46 mmHg).

PvO2 - mixed venous oxygen tension.
- N: 4.7-5.3 kPa.
- Minimum acceptable: 3.7 kPa (28 mmHg).

Pyothorax - large empyema.

Pyrexia - fever

Q - volume of blood.

QALY - quality-adjusted life-year.

QOL - quality of life.

Q - volume of blood per unit time.

QO2 - oxygen delivery (alternative abbreviation: DO2).

Qs - shunted blood.

QT - cardiac output.

Qs/Qt - shunt fraction.

RAP - right atrial pressure.

Raynaud's phenomenon of the lung - vasospasm in the lungs associated with Raynaud's syndrome.

RCV - respiratory syncytial virus.

Relative humidity
- N in ambient air: 25-50%.
- N in upper trachea: 95%.

REM - rapid-eye-movement phase of sleep cycle.

Resection - surgical cutting out.

Resistance to gas flow through airways:
- Spontaneous ventilation: 0.6-2.4 cmH2O/L/sec.
- COPD: 13-18 cmH2O/L/sec.
- During IPPV: 6 cmH2O/L/sec.

Respiration - (a) exchange of gases between the environment and tissue cells (by external respiration at alveolar-capillary level, and internal respiration at capillary-tissue level), or (b) regulation of the acid-base, metabolic and defence functions of the respiratory system

Respiratory inductive plethysmography - spirometry for ventilated patients, including measurement of lung volume to detect intrinsic PEEP.

Respiratory quotient (RQ)- ratio of CO2 produced to O2 consumed.
- Provides a measure of energy consumption.
- Usually < 1.0 because expired minute volume is slightly less than inspired minute volume, less CO2 being excreted than O2 absorbed.
- N: 0.7-1.0, depending on food eaten before test.
- RQ of carbohydrate oxidation: 1.0.
- RQ of fat oxidation: 0.7

Respiratory syncytial virus - responsible for respiratory infections such as bronchiolitis, bronchopneumonia, and the common cold

Rhinitis - inflammation of mucus membrane of nose, either seasonal (hayfever) or perennial.

Rhonchi - low-pitched snoring-like wheeze on ausculation, often related to airway secretions.

RPE - rate of perceived exertion

RR - respiratory rate.
- N: 10-20/min.

RTA - road traffic accident.

RV - residual volume.

SaO2 - saturation of haemoglobin with oxygen in arterial blood.
- N: 95-98%.

SARS - severe acute respiratory syndrome - viral disease that may be contracted by exposure to coronavirus, causing fever and dry cough.

SGAW - specific airways conductance.

Shunt - the proportion of blood that passes through the pulmonary vasculature without picking up oxygen.
- N: 2% of cardiac output.

SIMV - synchronised intermittent mandatory ventilation.

Sinus arrhythmia - acceleration of pulse with respiration, common in children.

Sinusitis - inflammation of sinus cavities of face; if chronic, may cause or exacerbate some pulmonary diseases.

Situs inversus - transposition of organs in chest and abdomen to the opposite side, e.g. heart on right side.

Sjögren’s syndrome - chronic autoimmune systemic disease in which white blood cells attack the moisture-producing glands. Symptoms include dry eyes and dry mouth, bronchial hyperresponsiveness and fatigue.

SLE - see systemic lupus erythematosus.

Small airways - terminal and respiratory bronchioles, i.e. < 1mm diameter; unsupported by cartilage therefore influenced by transmitted pleural pressures.

SOB - shortness of breath.

SOOB - sit out of bed.

Sodium (Na)- electrolyte in plasma or urine.
- N in plasma: 135-147 mmol/L [135-147 mEq/L].

Somatisation - distress expressed as a physical symptom.

Splanchnic - related to viscera.

SpO2 - oxygen saturation by pulse oximetry, equivalent to SaO2.

Standard bicarbonate - the bicarbonate concentration under standard conditions.

Stent - device for maintaining patency of obstructed structure.

Sternotomy - surgical cutting through the sternum.

Strength - ability of muscle to create force.

Stroke volume - volume ejected from ventricle with each beat.
- Dependent on preload, afterload and contractility.
- Normally same for each ventricle.
N: 60-130 ml.

Subcutaneous emphysema - surgical emphysema.

Surfactant- phospholipid protein complex that lines alveoli.

SVR - see systemic vascular resistance.

SvO2 - Mixed venous oxygen saturation, i.e. oxygen saturation of Hb in the pulmonary artery, reflecting gas exchange in lungs, cardiac output, metabolic rate haemoglobin levels and tissue oxygen uptake
- N: 75%.

Syncope - transient loss of consciousness, e.g. faint.

Systemic lupus erythematosus (SLE or lupus) - chronic systemic autoimmune disease leading to fluctuating inflammation of the lungs, joints and other organs

Systemic vascular resistance - (MAP-CVP / cardiac output) x 79.9. N: 800-1400 dyn.s.cm-5.
- Septic shock: < 300.

Tamponade - fluid in the pericardium.

TED - thromboembolic disease.

Tension-time index (TT) - measurement of muscle fatigue.
- Quantifies relationship between load and capacity.
- Indicates proportion of muscle's maximum capacity that can be sustained indefinitely.
- Diaphragmatic TT (TTdi) = (mean Pdi per breath / max Pdi) x TI/TTOT. TT beyond which fatigue occurs: 0.15.

Thoracentesis - thoracocentesis, i.e. withdrawal of fluid from pleural cavity.

Thoracoplasty - surgery used historically for pulmonary TB, involving rib resection and localised lung collapse to allow healing.

Thoracoscopy - minimal access incision through chest wall.

Thoracotomy - full surgical incision through chest wall.

Thrombocytopaenia - reduced platelet count.

Thrombolysis - dissolution of thrombus.

TIA - transient ischaemic attack.

Tidal volume. N: 7 mL/kg for spontaneously-breathing people, 7-10 mL/kg for ventilated patients, up to 12 mL/kg in acute respiratory failure.

TI/TTOT - see duty cycle

TLC - total lung capacity.

TLCO - total lung transfer capacity for carbon monoxide.

TPN - total parenteral nutrition, i.e. food administered intravenously.

Tracheal sounds - sounds heard on auscultation at suprasternal notch or side of neck.

Tracheal tube - endotracheal or tracheostomy tube.

Transpulmonary (transmural) pressure - pressure difference inside and outside lung, i.e. the difference between the above two pressures, representing the driving pressure responsible for inflating the lungs.

Trendelenburg position - head down tilt.

Tonicity - osmotic equivalence of fluids. Isotonic fluids have same osmolality as serum or plasma, hypotonic fluids have less, hypertonic fluids have more.

Torr- measurement of pressure used in USA, equivalent to mmHg.

TTdi - diaphragmatic tension-time index.

TTOT - total respiratory cycle.

Tusk mask - oxygen delivery system in which two 20 cm lengths of corrugated tubing are fitted to exhalation ports of oxygen mask to trap oxygen during exhalation and recycle it to patient during next inhalation.

Tussive - related to cough.

Us & Es - urea and electrolytes.

Upper respiratory tract - nose (or mouth), pharynx and larynx.

Urea - electrolyte in plasma or urine, formed from protein breakdown and excreted by kidneys.
- N in plasma: 3-7 mmol/L.
- Dehydration: > 8.
- Hypovolaemia: > 18.
- Kidney failure: 55.

Urine output
- N: 1 mL/hr/kg, average 50-60 mL/hr.
- Renal failure: < half normal.

V - volume of gas.

v - venous.

Valsalva manoeuvre - forced expiration against closed glottis.

VAP - ventilator-associated pneumonia.

VAS - visual analogue scale.

Vascath - vascular catheter, usually connecting patient to renal support.

Vasopressor - drug that causes vasoconstriction of capillaries and arteries.

VATS - video-assisted thoracoscopic surgery.

VC - (1) vital capacity, or (2) volume controlled ventilation.

VCIRV - volume-controlled inverse-ratio ventilation.

VD - volume of dead space gas.
- N: for anatomical VD: 2 mL/kg body weight.

VD/VT - dead space in relation to tidal volume, calculated by Bohr equation.
- N: 0.3-0.4, i.e. 30-40%, depending on position.
- Critical increase: 0.6.

Venous return - blood returning to heart.

VF - ventricular fibrillation.

VT - see tidal volume.

Venesection - see phlebotomy.

Venous admixture - mixing of shunted venous blood with oxygenated blood, i.e. mixture of 'true' shunt which completely bypasses the pulmonary capillary bed, and 'effective' shunt due to VA/Q mismatch.
- N: 5% of cardiac output.

Venous thromboembolism - combined PE and DVT.

Ventilation - gas movement between the outside of the body and the alveoli, i.e. inspiration and expiration.

VC - vital capacity.

VT - tidal volume.

v (with dot above) - mixed venous.

v (with dot above)- volume of gas per unit time, i.e. flow.

V50 (with dot above 'v')- flowrate half-way through expiration.

VA/Q (with dot above 'v')- ratio of alveolar ventilation to perfusion.
- N: 0.8 (4 L/min for alveolar ventilation, 5 L/min for perfusion).

VCO2 - CO2 production, i.e. mean fraction of expired CO2 x VE (with dot above 'v's).
- N: 200 mL/min at rest, increasing by 7% for each 1oC rise in body temperature.

VE (with dot above 'v')- (expired) minute volume/ventilation. Also abbreviated as MV. Expired gas is usually measured (more CO2 is produced than O2 consumed).

VO2 (with dot above 'v')- oxygen consumption.

VO2/DO2 (with dot above 'v's)- see oxygen extraction ratio.

VO2max (with dot above 'v')- oxygen consumption at maximum exertion, reflecting aerobic capacity. Increases with fitness, declines with advancing age but rate of decline is slower in physically active people.
- N: > 25 mL/kg/min, or 25 times resting level.
See also anaerobic threshold.

WBC - see white blood cell count.

Well-year of life - outcome measure incorporating morbidity and mortality, e.g. if disease halves quality of life for 2 years, patient has lost one full well-year.

White blood cell count - 4-10 109/L [4,000-10,000/mm-3].
- Bacterial infection: > 10,000/mm3.
- Vulnerability to infection: < 4,000/mm3.

WOB - see work of breathing.

Work of breathing - N: 0.3-0.5 kg m/min.

Xenotransplant - cross-species transplant.


Gupta D (1986) Anatomic basis of Arnold’s ear-cough reflex. Surg Radiol Anat, 8, 217-220