Skills - Rationale Flashcards
Respiration Process
Respiration
- Pulmonary ventilation (air movement in and out of the lungs)
- External respiration (gas exchange - O2 loading and CO2 unloading)
- Transport of respiratory gases (blood transports gases between lungs and tissue cells)
- Internal respiration (gas exchange between blood and tissue cells at capillary levels)
Tidal volume (Vt)
Tidal volume is the amount of gas expired per breath
Typically 500mL at rest
Dead space Volume (VD)
Dead space volume is the sum of the anatomical dead space (due to volume of airways - ~150mL) and physiological dead space (due to alveoli being ventilated but not perfused - usually insignificant)
Minute Volume (VE)
Minute volume is the amount of gas expired per minute
Alveolar ventilation (VA) - Formula
Alveolar ventilation is the amount of gas that reaches alveoli per minute
Formula VA = (Tidal volume - dead space) x Respiratory rate
Lung volumes
- Measurement
- Average size
- Description
Tidal volume (TV) ~500mL - amount of air inhaled or exhaled with each breath under resting conditions
Inspiratory reserve volume (IRV) ~3100mL - amount of air that can be forcefully inhaled after normal tidal volume inhalation
Expiratory reserve volume (ERV) ~1200mL - amount of air that can be forcefully exhaled after a normal tidal volume exhalation
Residual volume (RV) ~1200mL - amount of air remaining in lungs after a forced exhalation
Total lung capacity (TLC) ~600mL - max amount of air contained in lungs after a maximum inspiratory effort (TLC = TV+IRV+ERV+RV)
Vital capacity (VC) ~4800mL - max amount of air that can be expired after a maximum inspiratory effort (VC+TV+IRV+ERV = should be 80% TLC)
Inspiratory capacity (IC) 3600mL - max amount of air that can be inspired after normal expiration (IC=TV+IRV)
Functional residual capacity (FRC) ~2400mL - volume of air remaining in the lungs after a normal tidal volume expiration (FRC = ERV+RV)
Mechanics of respiration
- Pressures
- Components and functional abilities of lungs
Pressure
- Atmospheric pressure (at sea level) is 760mmHg
- Intrapulmonary pressure - rises and falls with phases of breathing and is the pressure within the alveoli of lungs
- Intrapleural pressure - pressure within the pleural cavity and is negative to intrapulmonary pressure and atmospheric pressure by ~4mmHg
Components and functional abilities of lungs
- Elastic ability of lungs - lungs assume smallest size possible at any given time
- Alveoli - surface tension caused by fluid film in alveoli acts to cause alveoli to fall to smallest size
- Chest wall - thoracic cage is elastic and acts to pull the thorax outwards and enlarge lungs
Atelectasis (lung collapse)
- Natural prevention
- Causes
Body naturally prevents atelectasis due to the difference between the intrapulmonary and inrapleural pressures (negative pressure)
Atelectasis occurs when the pressure equalises
Causes include
- Air entering pleural cavity
- Rupture of visceral pleura
- Air in intrapleural space (pneumothorax)
Boyle’s Law
Boyle’s law states that volume changes lead to pressure changes which lead to the flow of gases to equalize the pressure
The pressure of gases varies inversely with its volume
Inspiration
Active process requiring muscular effort
- High to low pressure
- Thoracic cavity volume increases
- Fall in alveolar pressure
- Gases always flow down their pressure gradient
- Flow ceases when intrapulmonary pressure is 0 and equal to atmospheric pressure
Expiration
Passive process due to lung recoil
- Thoracic cavity volume decreases
- Elastic lungs recoil passively and intrapulmonary volume decreases
- Intrapulmonary pressure rises
- Air gases flow out of lungs
Dalton’s law of partial pressure
Dalton’s law states that the total pressure exerted by a mixture of gases is the sum of the pressures exerted independently by each gas in mixture
Partial Pressure of air at atmospheric level and alveoli
Atmospheric:
- Nitrogen = 78.6% with PP of 597mmHg
- Oxygen = 20.9% with PP of 159mmHg
- Carbon dioxide = 0.04% with PP of 0.3mmHg
- Water vapour = 0.46% with PP of 3.7mmHg
- Total = partial pressure of 760mmHg
Alveoli:
- Nitrogen = 74.9% with PP of 569mmHg
- Oxygen = 13.7% with PP of 104mmHg
- Carbon dioxide = 5.2% with PP of 40mmHg
- Water vapour = 6.2% with PP of 47mmHg
- Total = partial pressure of 760mmHg
Henry’s Law
Henry’s law states that when a mixture of gases is in contact with a liquid, each gas will dissolve in the liquid in proportion to its partial pressure.
The greater the concentration of a particular gas in the gas phase the more that gas will dissolve in the liquid
Transport of CO2 in the body
CO2 is transported in the blood from the tissue cells to lungs in 3 ways
- Dissolved in plasma
- Chemically bound to hemoglobin in RBC
- As bicarbonate ion in plasma
Haldane effect
Haldane effects states that
- Deoxygenated hemoglobin combines more readily with CO2 than oxygenated hemoglobin
- It is the greater ability of reduced hemoglobin to form carbaminohaemoglobin and buffer H+ by combining with it
- As CO2 enters systemic bloodstream it allows more CO2 to combine with hemoglobin and more bicarbonates ions to be formed
- Haldane effect encourages CO2 exchange in both tissues and lungs
Bohr Effect
Bohr effects state that with more CO2 entering bloodstream it causes more oxygen to dissociate from hemoglobin
Capnography
- What it is
- How it works
- What it measures
- Normal limits
Capnography is the measurement of end tidal carbon dioxide levels
How it works
- Uses infrared waves to measure CO2 levels as infrared is absorbed by gases that have 2 or more different atoms
- 5 characteristics of waveform - Height, frequency, rhythm, baseline and shape
What it measures
- Proportion of CO2 in expired air
- End-tidal CO2 represents the gold standard for confirming advanced airway placement
- If return of spontaneous circulation occurs, a spike in end tidal CO2 often appears before pulse detected
- See slides for image of normal wavelength
Normal limits for end tidal CO2 are 35-45 mmHg
Causes of abnormal end tidal carbon dioxide
Elevated ETCO2
- Decreased ventilation secondary to head trauma, overdose, respiratory failure, sedation, stroke
- Increased carbon dioxide production due to fever or shivering
Decreased ETCO2
- Ventilation problem due to esophageal intubation, airway obstruction
- Inadequate blood flow due to cardiac arrest, tension pneumothorax, pericardial tamponade, reduced CO
- Ventilation-perfusion mismatch due to pulmonary embolism
- Decreased production of CO2 due to hypothermia
- Sampling error due to inadequate tidal volume delivery or CO2 sampling tubing blocked
Definition of respiratory failure
- Acute respiratory failure
- Chronic respiratory failure
Respiratory failure is defined as a partial pressure of arterial oxygen that falls below 60mmHg (hypoxia) or pressure of arterial CO2 above 50mmHg (hypercapnia)
Acute respiratory failure
- Characterized by life threatening derangement in PaO2, PaCO2 and acid base balance
Chronic respiratory failure
- Alterations in arterial blood gas valves and can cause very different normal vital signs
Common respiratory conditions
- Chronic obstructive pulmonary disease (COPD)
- Asthma
- Bronchiectasis
- Sarcoidosis
- Lung cancer
- Influenza
- Pneumonia
Gas Exchange as ventilation : perfusion ratio
- Hypercapnia
- Hypoxaemia
Gas exchange is the balance between alveolar ventilation and pulmonary capillary blood flow
Changes expressed as ventilation: perfusion ratio (V/Q)
- High ratio indicates greater than normal ventilation and lower than normal perfusion
Hypercapnia
- Increase in PaCO2 due to increased tidal volume and/or respiration rate which decreases alveolar ventilation and CO2 removal can alter acid base balance
Hypoxaemia
- Oxygenation of arterial blood decreases
- Contributing mechanisms include decreased alveolar oxygenation, decreased diffusion of oxygen from alveoli to pulmonary capillaries and decreased pulmonary capillary perfusion
Respiratory Assessment
- Primary Survey
- Clinical history
- Physical assessment
Primary Survey
- Gross signs of respiratory compromise including airway obstruction, stridor,, increased respiratory effort and marked accessory muscle use, tachypnoea, decreased speech tolerance, pallor or cyanosis, hypoxia, paradoxical chest wall movement, decreased air entry and altered level of consciousness
Clinical History
- Current event
- Underlying illness/disease
- Current symptoms
Physical assessment
- Inspection, palpation, percussion and auscultations
- See textbook for details
Support for respiratory function
- Oxygen therapy (low flow, high flow)
Oxygen therapy
- Low flow - fraction of inspired oxygen varies from breath to breath and depends on patient minute ventilation
- High flow - accommodates patient inspiration demands and maintains fixed FiO2 irrespective of patient respiratory rate and tidal volume
- Note that oxygen administration can elevate the PaCO2 due to changes in ventilation: perfusion ratio in lung therefore causing hypercapnia
Non invasive ventilation
- Benefits
- Evidence needed for respiratory support
- Contraindications
Benefits
- Improved survival, fewer complications, increased comfort and decreased cost
- Can be used in acute, chronic, hypoxaemic or hypercapnic conditions
Evidence needed for respiratory support
- Moderate to severe respiratory distress
- Increased respiratory rate
- Use of accessory muscles
- Arterial blood gas show respiratory acidosis or PaCO2/FiO2 under 200
Contraindications
- Impaired consciousness
- Hemodynamic instability
- Myocardial ischemia, unstable angina
- Unable to protect airway
- Copious respiratory secretions
- Uncooperative, agitated or depressed level of consciousness
- Difficulty fitting mask
- Head trauma with unstable respiratory drive
- Recent upper airway or GI surgery
Invasive mechanical ventilation
- Full ventilation support
- Partial ventilation support
Endotracheal tube or mechanical ventilation
Full ventilation support - maintained effective alveolar ventilation irrespective of patient comfort
Partial ventilation support - patient contributes to breathing and maintaining alveolar ventilation
Principles of mechanical ventilation
- 4 phases to deliver a breath
4 phases:
Change from expiration to inspiration phase
- Time triggered (deliver breath after set time)
- Pressure triggered (patient effort sufficient to decrease circuit pressure)
- Flow triggered (patient effort sufficient to drop flow in circuit)
Inspiration phase
- Pressure limited - pressure rises but does not exceed set limit (poor lung compliance)
- Volume limiting - max volume to deliver
- Flow limiting - patient access to increase flow to accommodate increased demand
Change from inspiration to expiration phase
- Volume & time cycling - not influenced by changes in lung compliance but may contribute to increased airway pressure
- Pressure cycling - influenced by lung compliance and volume delivered dependent on flow, length of inspiration, lung characteristics and set pressure
- Flow cycling - pressure supported breath (exhalation valve open when predetermined flow rate reached)
- Pressure, flow, volume or time can be variable cycling but only one cycle per individual breath
Expiration phase
- Passive - baseline pressure altered and usually positive
- PEEP usually applied and prevents early airway closure and alveolar collapse at end of expiration
Breath delivery strategies in mechanical ventilation
- Continuous mandatory ventilation
- Assist control ventilation
- Synchronized intermittent mandatory ventilation
- Pressure support ventilation
- Continuous positive airway pressure
Routes of drug administration
Enteral - Gastrointestinal tract administration
Parenteral - Any route other than GIT administration
Pulmonary - Endotracheal tube in inhalation
Topical - Applied to skin and mucous membrane
Routes of administration and absorption rate
Endotracheal - rapid Enteral - slow Intramuscular - moderate Intranasal - rapid Intraosseous - immediate Intravenous - immediate Pulmonary - rapid Subcutaneous - slow Sublingual - rapid Topical - moderate
Note - quicker absorption in areas with rich blood supply and absorbent membrane
Factors that influence drug response
- Dietary factors
- Cardiovascular function
- Gastrointestinal function
- Immunological function
- Liver function
- Renal function
- Albumin concentration
- Stress
- Fever
- Starvation
- Behavior
- Alcohol intake
- Tobacco or marijuana smoking
- Age
- Sex
- Pregnancy
- Lactation
- Exercise
- Sunlight
- Barometric pressure
- Disease
- Infection
- Occupational exposures
- Psychological status
- Drugs
- Circadian and seasonal variations
Drug Dosage
- Therapeutic effect
- Therapeutic margin
- Peak level
- Incremental doses
Therapeutic effect
- Desired response/reason drug is prescribed
Therapeutic margin
- Plasma concentration of a drug between therapeutic threshold and toxic levels
Peak level
- Highest plasma concentration of a drug
Incremental doses
- Multiple smaller doses given over time (Titrate to achieve desired response)
- Aim is to achieve peak plasma levels within therapeutic margin within minimum effective dose and reduce potential for toxicity as well as maintain a therapeutic drug plasma level
Drug therapy in different types of people
Paediatric
- Baby liver and kidneys are immature
- All drug doses must be related to body weight (Agex3+7)
Elderly
- Diminished metabolism and excretion can lead to increased drug reaction
Larger doses are required to reach desired concentration in larger people
Factors influencing the drug reaction in different people
Sex differences
- Male and female drug reaction differences due to difference in size and difference in distribution of fat and water
Genetic factors
- Can cause abnormal sensitivity
- Difference in drug metabolism
Psychological factors
- Influenced by way a person feels about a drug and what they believe the drug will achieve
Illness/Disease
- Use consult line
Environmental
- Temperature can effect drug activity
- Elevated temp causes peripheral blood vessels to dilate therefore intensify action of vasdilators
- Cold environment can cause vasoconstriction that can inhibit the action of vasodilators
- Environment can influence a persons hydration status which directly influences the peak plasma levels of drugs
Rights of drug administration to patients (9 - not exhaustive)
Right drug Right dose Right patient Right time (and frequency) Right route of administration Right to refuse (if capable) Right date (drug expiration) Right documentation Right to aseptic drug administration
Safety checks prior to drug administration
- Obtain consent from patient
- Exclude risk of contamination
- Check drug to be given
- Re-check allergy status of patient
- Check packaging is in tact
- Check contents as should be
- Check dose
- Check drug is in date
- Check route of administration
- Ensure drugs identified in packaging is same as in administration device
- Dispose of everything safely
Pain management
- What is pain
Pain is subjective
- Numerical format (0-10)
- Phrases (mild, moderate, severe)
- Descriptive - stabbing, throbbing, sting, sharp, tight etc.
Ethics of pain management
- Always unethical to withhold pain relief
- Never be coercive with regard to pain relief
- Do not treat the pain you think the patient is experiencing, treat the pain the patient is experiencing
Types of pain
Acute - Sudden onset that usually response well to management
Chronic - persistent/recurrent and requires constant pain management
Referred - pain felt that does not arise from point of origin
Somatic - arising from skeletal muscle, ligaments, vessels or joints
Superficial - abrasions, soft tissue injuries
Visceral - often described as dull and aching and difficult to localize
Emotional
Interpreting pain
Protective pain sensations
- Nococeptive pain - has a purpose as it is neurological and reflexive response as a result of damage to tissue
> Can cause increased BP, tachycardia, tachypnoea as it activates SNS
Non-Protective pain sensations
- Neuropathic pain - chronic or persistent and caused by damage to CNS or PNS
Techniques of pain relief
- Rest and reassurance
- Positioning
- Heat/cold
- Therapeutic drug intervention
- Reduction
- Pressure
Assessment of pain
- Intesity
- Onset
- Aggravating factors
- Relieving factors
- Quality
- Location
- Duration
- Associated symptoms
(OPQRST AS-PN)
Goals in pain assessment
- Determine presence and cause of pain
- Identify exacerbating co-morbitdities
- Review beliefs, attitudes and expectations regarding pain
- Gather information that assists and impacts an individualized treatment plan
Out of hospital pain relief options
Fentanyl Ibuprofen Lidocaine 1% Ketamine Paracetamol Morphine Sucrose 24%
Naloxone
Used in opiate overdose
- Can cause pupil constriction
- Half life is considerable shorter than heroin therefore can have rebound
Ondansetron
Antiemetic for nausea and vomiting
When to administer fluid therapy
Inadequate tissue perfusion/shock
What are the 4 types of shock
- Causes
Hypovolaemia (relative/absolute)
- Inadequate circulating volume
- Fluid volume loss, hemorrhage, burn, severe diarrhea and/or vomiting
- Relative hypovolaemia (anaphylaxis, septic, spinal)
Cardiogenic
- Inadequate cardiac pump function
- Dysrhythmia (electrical/mechanical), angina/AMI, poisoning, other cardiac muscle damage
Distributive
- Peripheral vasodilation and maldistribution of blood flow
- Usually caused by acute vasodilation without concomitant increase in intravascular volume or CO
Obstructive
- Extra cardiac obstruction to blood flow
- Caused by obstruction in CV system that reduces CO despite normal heart function and blood volume (cardiac tamponade, embolism, thrombus, tension pneumothorax)
What is the shock triangle?
- Problems
Pump - Pipes - Fluid
Pump problems
- Problems associated with myocardium resulting in decreased pumping efficiency
Pipe problems
- Difficulty relating to loss of vascular tone or capabilities
Fluid problems
- Loss of intravascular fluid volume due to variety of reasons
Classification of blood loss
Class 1 - Hemorrhage
- Loss of up to 750mL, usually no signs or symptoms, equivalent to donating a unit of blood
- Patient presents pink and adequately perfused
Class 2 - Hemorrhage
- Loss of 750-1500mL blood (15-30%)
- Patient presents anxious and restless, mild tachycardia, BP unchanged or mild diastolic elevation, decreased urine output, mildly pale
Class 3 - hemorrhage
- Loss of 1500-2000mL blood (30-40%)
- Patient presents as tachycardia, tachypnoea, decreased BP, CNS status dropping, decreased urine output, pale skin, mild cyanosis
Class 4 - hemorrhage
- Loss of over 40%
- Patient presents as tachycardia, tachypnoea, narrow pulse pressure, severely shocked appearance, CNS severely depressed, ashen grey in color and severe cyanosis
Autonomic responses to shock
- Arteriole vasoconstriction, resulting in redistribution of blood from skin, skeletal muscle, kidney and splanchnic viscera
- Increased HR and contractility that increases CO
- Constriction of venous capacitance vessels, which augments venous return
- Release of vasoactive hormones epinephrine, norepinephrine, dopamine and cortisol to increase arteriolar and venous tone
- Release of antidiuretic hormone and activation of the renin-angiotensin axis to enhance water and sodium conservation to maintain intravascular volume
Fluid therapy and neurotrauma
- Cerebral blood flow
> Vascular tone is regulated by CO2 pressure, O2 pressure and autonomic and neurohumoral control (PCO2 has greatest effect on intra-cerebral vascular diameter and subsequent resistance) - Cerebral perfusion pressure (60-100mmHg)
> CPP = MAP-ICP - Intracranial pressure (0-15mmHg)
> Increased ICP the ability to maintain CPP is compromised and blood flow diminished
> Body compensates by increasing MAP which elevates ICP and CSF is displaced to compensate
> If unresolved brain substances can herniate
> Signs and symptoms include headache, nausea, vomiting, altered level of consciousness, Cushing’s triad (increase systolic pressure, decreased pulse rate and irregular respiratory pattern)
> See slide 86 for flow chart of process - Mean arterial pressure (85-95mmHg)
> Maintained with a systolic BP of 100-120mmHg (maintain MAP to allow blood flow but minimize cerebral edema)
Cerebral vasodilation occurs by increasing ICP and decreasing CPP
Fluid therapy and trauma
Uncontrolled hemorrhage
- Give fluid to maintain perfusion status NOT to replace blood products
- Radial pulse/BP 80-90mmHg
- Risks include Disrupt formation of thrombus, Raise BP, Cool blood, Increase bleeding, Decreased oxygen carrying capacity
Controlled hemorrhage
- Administer IV fluid
- Maintain BP normal for patient
- Conserve body heat
Fluid therapy and burns
- Capillaries lose ability to retain fluid
- Extravasation
- Osmotic gradient between intravascular and extravascular space is detrimentally affected
- Causes edema and accumulation of vascular fluid in tissues
- Physiological issues include compromised CO, systematic vascular resistance and reduced peripheral blood flow
Fluid therapy and septic shock
Septic shock results in - Persistent hypotension, organ hypoperfusion despite adequate fluid intake - Tachypnoea - Tachycardia - Febrile/Frigid - Oliguria - Altered mental status - Peripheral vasodilation -Under 2 sec capillary refill - Mottled skin Fluid therapy is indicated to maintain perfusion
Fluid therapy and Diabetic ketoacidosis
Diabetic ketoacidosis
- Hyperglycaemic
- Diagnosed through blood glucose reading
- Past history include known diabetes, polyuria/polydispsia, kussmaul’s respirations, pear-drop/acetate smell off breath, acidosis, dehydration/dry mucous membranes
Fluid therapy and heat exhaustion
- Treatment
Heat exhaustion - Orthostatic hypotension - Core body temperature - Headache - Nausea and vomiting - Loss of water and salt - Electrolyte imbalance If left untreated can lead to heat stroke
Treatment
- Keep patient cool
- Conservative use of fluids
Fluid therapy and Heat stroke
- Treatment
Heat stroke
- Classical/exertion
- Altered mental status/neurological dysfunction
- Core body temperature over 41 degrees
- Hot, dry skin
- Organ failure
- Electrolyte imbalance
Treatment
- Effective cooling will mitigate continuing fluid loss (remove clothing, gentle fanning, aggressive/conservative fluid therapy, oxygen therapy)
Early goal directed therapy
Based on - Cardiac preload - Cardiac after load - Contractility To achieve a balance between systemic oxygen delivery and oxygen demand
Calculating IV flow rates
Need to know - drops per minute
- Volume to be infused
- Period of time (min)
- Number of drops per millimeter
Formula:
Drops per minute = (Volume to be infused x drop factor) / Duration of infusion (min)
Isotonic Solution
- Osmosis
Cell has same concentration inside and out
If it becomes unbalanced use osmosis to equal out (Osmosis - molecules move from low concentration to high concentration)
Hypotonic Solution
Compare outside and inside of cell
- Hypotonic when low solute extracellularly therefore osmosis occurs to shift fluid inside cell meaning the cell swells
Hypertonic solutions
Compare outside and inside of cell
- Hypertonic when high amount of solute extracellularly therefore osmosis causes water to rush out of cell meaning the cell shrinks
- Fluid use very cautiously
Colloids versus Crystalloids in fluid therapy
Colloids
- Not used by ACP
- Contains protein molecules that often too large to pass through capillary membrane
- Remain in vascular compartment for longer time than crystalloid solutions
Crystalloids
- Quick to equilibriate between vascular and extra vascular spaces
- 3mL of crystalloid solution required to replace 1mL of blood (maintain BP)
Sodium Chloride NaCl 0.9%
Isotonic crystalloid Electrolyte replenishes Precautions - Heart failure - Renal failure - Uncontrolled hemorrhage
