Applied Respiratory System

Question 1

Mechanisms of respiration&raquo_space;> inspiration

Answer 1

• active process requiring energy (muscular energy)
• chest expands (intercostal muscles contract causing the rib cage to move up and out)
• diaphragm flattens causes an increase in thoracic space and the lungs begin to expand
• lungs are attached to the chest wall via the parietal pleura so as the chest expands the pressure within the lung drops and becomes a negative pressure (creating a vacuum)
• air rushes in through the nasopharynx and oropharynx to fill the vacuum and the lungs continue to expand until the pressure equalises

Question 2

Mechanisms of respiration&raquo_space;> expiration

Answer 2

• passive process - requires no energy
• elasticity of lung tissue (compliance) and of lung muscles cause increase in resistance until the pressure inside the lungs is equal to the pressure outside the lungs
• the diaphragm collapses and returns to a dome shape. This causes a decrease in thoracic volume and cause the lungs to compress
• lung volume begins to decrease and intrathoracic muscles relax causing chest volume to decrease and an increase in air pressure within the lung. This increase in pressure causes the gas to be forced out of the lung up through the trachea and out of the nasopharynx and oropharynx
• carbon dioxide and water vapour are exhaled through this process

Question 3

Functional residual capacity (FRC)

Answer 3

• FRC is the amount of air present in the lungs at the end of passive exhalation
• this is a measurement of the elasticity of the lung tissue itself
• loss of lung elasticity = increase in lung resistance and decrease in FRC
• this can be observed by measuring the FEV
• this is measured using a spirometer - a decrease in FEV may indicate a loss of FRCand therefore some lung damage

Question 4

Flow

Answer 4

Normally air i able to flow easily in and out of the lungs but certain conditions can inhibit air flow

Question 5

Measuring flow

Answer 5

• we can measure lung flow easily and patients with chronic or acute lug conditions will often have their lung flow tested regularly
• you will undertake these observations as a nurse
• this is called peak flow measurements of peak expiratory flow rate (PEFR)
• we can use peak flow as an indicator of how well or not a patients condition is progressing

Question 6

Bronchoconstriction

Answer 6

• certain conditions can cause constriction of the airways within the lungs
• this is known as bronchoconstriction
• conditions such as asthma, COPD, bronchitis, bronchiectasis, emphysema, pulmonary fibrosis and anaphylaxis can all cause narrowing of the airways for a variety of reasons

Question 7

Pulmonary fibrosis

Answer 7

• this is where you get scarring of the alveoli (due to repeated infection or exposure to hot gas)
• alveoli lose their elasticity and are unable to expand or contract. This increases the resistance within the lung increases the effort required to start a breath
• the scarring also effects the tissue of the alveoli and means that gas exchange can not happen over this membrane (dead space)

Question 8

Emphysema

Answer 8

• a restrictive lung disease
• repeated infection cause significant changes to the elasticity of the alveoli increasing resistance
  The alveoli also lose surface area as they stretch and collapse

Question 9

Surfactant

Answer 9

• surfactant is a substance that is secreted by lung lamellar cells in order to reduce surface tension and reduce the adhesion with alveolar tissue
• it stops the alveoli from sticking together and collapsing at the end of exhalation and reduces work of breathing

Question 10

Oxygen saturations

Answer 10

• oxygen saturation levels is a key observation thats undertaken when respiratory function is measured
• oxygen binds with haemoglobin and is known as oxyhaemoglobin
• once it has discharged all of its oxygen it is known as de deoxyhaemoglobin
• carbon dioxide then binds to the empty haemoglobin cells and these are transported to the lungs and released

Question 11

Pulse oximetry

Answer 11

• pulse oximetry is a non invasive method for determining the oxygen saturations of the capillary blood and pulse rate
• a clip with a sensor is attached to the fingertip for measurement which penetrates the skin. The light receiver records the light intensity and determines how much light of the different light colours was absorbed
• the values measured in this way in this way are usually very precise and correlate within a 4% deviation with the arterially measured oxygen saturation. Pulse oximetry can only detect oxyhaemoglobin
• normal oxygen saturations should be between 95-100%
• in some patients with chronic lung diseases or other conditions may have reduced lung functions and therefore their stats will be lower
• in healthy patients oxygen saturations below 92% should however be investigated

Question 12

Various factors that affect the accuracy of oxygen saturation probes and the results they give

Answer 12

• Venous insufficiency&raquo_space;> such as peripheral vasoconstriction or central hypovalemia
• chronic conditions&raquo_space;> cause peripheral blood flow thats reduced in fingers and toes e.g. reynauds
• nail varnish or acrylic
• ethnicity&raquo_space;> reflection of light in darker skinned patients lead to overestimation of stats
• respiratory distress&raquo_space;> stats may be difficult to obtain if patient is in distress - seek medical intervention