Airway & Breathing Flashcards
Hypoxaemia
Definition
Causes
Effects
Low levels of oxygen in the blood.
Causes:
- impaired O2 intake - e.g. airway obstruction, lack of environmental O2.
-impaired gas exchange - e.g. alveoli collapse, pulmonary oedema.
- decreased Hb - e.g. anaemia, blood loss.
- cellular environment not supportive of O2 utilisation - e.g. metabolic acidosis.
Effects: hypoxia, impaired anaerobic metabolism and cellular dysfunction
Hypoxia
Definition
Signs/Symptoms
Inadequate supply of oxygen to tissues and vital organs.
Signs/symptoms arise first from organs at greatest risk:
- Brain - headache, confusion, decr. LOC.
- Heart - chest pain, tachy-arrhythmia, peripheral vasoconstriction.
-Lungs - tachypnoea, incr. WOB.
Respiratory Acidosis
Definition
ABGs
Causes
Elevated levels of CO2 and resultant decrease in pH (acidic).
ABGs = pH < 7.35 and PaCO2 > 45mmHg.
+/- HCO3 > 26mmol/L = metab. comp
Cause - inadequate alveolar ventilation = CO2 retention - e.g. espiratory depression, asthma, COPD.
Respiratory Alkalosis
Definition
ABGs
Causes
Low levels of CO2 (excess clearance) and resultant increase in pH (alkaline).
ABGs = pH > 7.45 and PaCO2 < 35mmHg.
+/- HCO3 < 22mmol/L = metab. comp
Causes- hyperventilation = excess CO2 clearance - e.g. anxiety/panic, pain, PE, pneumothorax, compensation for hypoxia.
Pulmonary Oedema
Definition
Causes
Patho
Abnormal build-up of fluid in alveoli resulting in impaired gas exchange.
Causes - viral/bacterial infection, PE, CHF, high altitudes, upper-airway obstruction.
Patho - impaired LV function OR build-up of infectious material > impaired lymphatic drainage in distazl lung > accumulation of fluid > impaired capillary diffusion.
Pneumonitis
Definition
Causes
Patho
Inflammation of alveoli resulting in impaired gas exchange.
Causes - airborne irritants, aspiration, infection or secondary to systemic events.
Patho - alveolar irritation > inflammatory response > altered pulmonary capillary permeability > haemorrhage and fluid leakage > neutrophil mediators > pulmonary vasoconstriction.
Metabolic Acidosis
Definition
ABGs
Causes
Elevated concentration of H+ ions in blood and resultant decrease in pH (acidic).
ABGs = pH <7.35, HCO3 < 22mmol/L and BE < -2mmol/L.
+/- CO2 < 35mmg = resp. comp
Causes
- increased H+ production - e.g. lactic acidosis, DKA.
- reduced H+ excretion - e.g. renal failure.
- increased HCO3 clearance - e.g. GIT losses, renal tubular disease, Addisons.
Metabolic Alkalosis
Definition
ABGs (+/- comp.)
Causes
Low concentration of H+ ions in blood and resultant increase in pH (alkaline).
ABGs = pH > 7.45, HCO3 > 26mmol/L and BE > +2mmol/L
+/- CO2> 45mmg = resp. comp
Causes:
- decreased H+ concentration - e.g. hypokalaemia.
- increased H+ excretion - e.g. GIT losses, diuretics
- decreased HCO3 clearance - e.g. liver cirrhosis.
Acidosis/Alkalosis Compensation
Aim - return pH to baseline by altering levels of CO2 or HCO3.
Lungs (rapid) -
Alkalosis - decr. RR > decr. CO2 clearance.
Acidosis - incr. RR > incr. CO2 clearance
Kidney (slow) -
Alkalosis - incr. excretion of HCO3 ions
Acidosis - incr. excretion of H+ ions, decr. excretion of HCO3 ions.
Mixed Respiratory/Metabolic Acidosis
ABGs
Causes
pH < 7.35
PaCO2 > 45
HCO3 < 22
*PaCO2 and HCO3 moving in opposite directions.
- Cardiac arrest
- MODS
Mixed Respiratory/Metabolic Alkalosis
ABGs
Causes
pH > 7.45
CO2 < 35
HCO3 > 26
*PaCO2 and HCO3 moving in opposite directions.
-Hyperventilation in COPD
-Hyperemesis gravidarum
- Liver cirrhosis and diuretic use
Internal Respiration
Exchange of gases between systemic blood capillaries and tissue cells. O2 transported in blood (bound to Hb molecules) from pulmonary capillaries via LV/aorta and systemic arteries. CO2 produced by tissue cells during anaerobic metabolism. O2 and CO2 diffuse via interstitial fluid in opposite directions according to diffusion gradient.
External Respiration
Exchange of gases between alveoli and pulmonary blood capillaries. O2 inhaled from atmospheric air. CO2 transported from tissues (as HCO3) to pulmonary capillaries via systemic veins, RV and pulmonary artery. O2 and CO2 diffuse via respiratory membrane in opposite directions according to diffusion gradient.
Respiratory Membrane
Basement membrane composed of single-cell layer of simple squamous epithelium fused to alveolar epithelial cells and pulmonary capillary endothelial cells. Site of gas exchange.
Inspiration
Movement of air into lungs via negative pressure created by diaphragm contraction and increasing lung volume. Active process involving contraction of diaphragm and external intercostals.
Expiration
Movement of air out of lungs via positive pressure and decrease lung volume . Passive process involving diaphragmatic relaxation, elastic recoil and surface tension (surfactant) of lungs to return to resting state.
Respiratory Centres
Medulla (PRIMARY CENTRE) - sends signals to muscles that stimulate inspiratory and expiratory movements AND controls reflexes for non-respiratory air movements (e.g. coughing, sneezing, swallowing).
Pons (SECONDARY CENTRE) - controls rate, speed and depth of involuntary respiration via two opposing regions.
Chemoreceptors - detect pH levels in blood and send signals to respiratory centres to adjust ventilation.
Tachypnoea
Definition
Causes
Abnormally rapid rate of respiration >20bpm.
Causes - EARLY SIGN OF CLINICAL DETERIORATION, respiratory distress, panic/anxiety, respiratory compensation (metabolic acidosis), hyperthermia.
Bradypnoea
Definition
Causes
Abnormally slow rate of respiration <12bpm.
Causes - EARLY SIGN OF CLINICAL DETERIORATION, respiratory depression (drugs/brain injury), respiratory compensation (metabolic alkalosis), hypothermia.