Positioning to maximise lung function Flashcards
what do lungs require for respiratory function
lungs require- adequate ventilation of alveoli, adequate blood supply to exchange and transport 02, C02
ventilation perfusion matching
for gas exchange to occur ventilation and perfusion need to be in the same place at the same time- blood and air. this is V/Q matching (V/Q ratio), perfect match 1/1, we require 0.8/1)
how do V/Q change
they increase independently from top to bottom of the lung, this change occurs in the vertical plane regardless of body position Q is increased to a greater extent because gravity exerts a greater effect on blood than inspired air
why is the dependent (lower) region of the lungs are better ventilated
alveoli in the non-depdent region (upper) are already inflated because of the weight of the lung hanging in thorax- already at max- cant open more
in addition, in side-lying the lower hemi-diaphragm is pre stretched by abdominal pressure and therefore has a mechanical advantage over the upper hemi-diaphragm causing twice the excursion
what is ventilation
this is the movement of air in and out of the lung. not evenly distributed. primarily gravity dependent in the spontaneously breathing adult. follows a ventilation gradient, down the lung
what is perfusion
blood flow in the capillary bed. gravity dependent in the spontaneously breathing adult. follows a perfusion gradient down the lung tissue. changes with exercise (increase blood flow) and posture (effects where blood is)
regional difference in ventilation
lower regions ventilate better than upper. intrapleural pressure is less negative at the bottom than the top of the lungs- as pleura are being pulled out. lower lungs have greater potential for increase ventilation. alveoli in lower region have greater ability to expand
factors affecting V/Q- ventilation
pleural pressure, altered lung compliance/ expandability, altered airway resistance, airflow resistance, lung volume, physiologic dead space, shunt
factors affecting V/Q- perfusion
wastes ventilation, circulatory disorders
abnormal VQ
wastes perfusion or shunt where there is adequate blood supply but there is problem getting gas to it (consolidation) or caused by wasted ventilation- gases available but problem with blood supply- blockage
use of body position to:
maximise ventilation, maximise diaphragmatic function, optimise V/Q matching, but also decrease WOB and drain sputum
why does mechanical ventilation reverse ventilation away from the dependent lung
the diaphragm is pushed down passively. airflow takes the path of least resistance. increased perfusion in depend regions compresses lung and accentuates the perfusion gradient. absorption atelectasis at higher oxygen concentrations, cannot get V/Q max
why are dependent regions more prone to collapse- mechanical ventilation
due to lack of nitrogen
if patient on mechanical ventilation and sidelying
perfusion not affected- occurs most in lung that is lower most, ventilation- occurs mainly in upper lung as it hangs in chest wall and is already open,
lung volume- total lung capacity (TLC)
total volume of gas in lungs after maximum inspiration- between 3 and 8 litres- dependent on persons size and sex, sum of- respiratory volume, inspiratory reserve volume, expiratory reserve volume, tidal volume
lung volume- vital capacity
volume of gas exhaled after full inspiration- 3-6 litres- used in pulmonary function test- force VC
lung volume- residual volume
volume of air in lungs after expiration- 1 litre
lung volume- expiratory residual capacity
extra volume of gas that can be exhaled forcefully when you reach end of TV- 1 litre
lung volume- functional residual capacity
volume of gas remaining at end of TV expiration, reflects good resting position, inward and outward elastic recoil are balanced, reduced in restrictive diseases, increased in hyperinflated disease- 2 liters, lowers closes we get to supine
lung volume- inspiratory reserve volume
extra volume of gas inhaled voluntarily at the end of inspiration TC- used in deep breathing exercises/ exercise- 3 litres
lung volume- tidal volume and closing volume
volume of gas exhaled and inhaled during one respiratory cycle- resting volume 300-800ml
closing volume- volume at which alveoli start to collapse
what causes variations in lung volume
body size, age, sex, muscular training, lung pathology
FRC and closing volume
have a close relationship, if FRC decreases you are more likely to get close to closing volume. patients with low FRC- have areas where alveoli are collapsed down
what is dead space
volume of air inhaled but not used in gas exchange
dead space- anatomical dead space
gas left within mouth and trachea when we breath- not involved with gas exchange
dead space- alveolar dead space and physiological dead space
alveolar- air in alveoli that should be involved with gas exchange, but due to low blood supply it isn’t
physiological- sum of both anatomical and alveolar dead space
dead space- treatment
with any treatment/ intervention we want to avoid increasing dead space
ventilators- increases anatomical dead space
breathing re-education-
in patients with chronic diseases the aims are normally to reduce WOB and give patients confidence in their ability to control breathless attacks. minimalist approach is advised, their unnatural breathing pattern may be optimum for them if breathing is irregular, paradoxical or unnecessarily tense, this is useful to improve breathing efficiency
breathing re-education- breathing technique
practice can enable a breathing technique to be used more easily when required, especially when getting their breath back after exertion
breathing re-education- acute problems
in patients with acute problem it is often to help reverse the problem or treat the signs and symptoms manifesting themselves as a consequence
what is diaphragmatic breathing
breathing using abdominal movement reducing the degree of chest wall movement as much as possible
interchangeable with breathing control
what is breathing control
normal tidal breathing encouraging relaxation of the upper chest and shoulders, interchangable with diaphragmatic breathing
abdominal/ diaphragmatic breathing thought to
decrease airway turbulence, decrease dead space, favour dependent regions, relaxes shoulder girdle
abdominal/ diaphragmatic breathing instructions
relaxed position, rest a hand on abdomen, keep shoulders relaxed, breath in slowly so hand rises, sigh out, tru and increase depth of breathing
deep breathing- what does it do
increase lung volume, increase ventilation, decrease airway resistance, increase surfactant secretions, aid V/Q matching, decrease dead space, increase diffusion, increase O2 saturation
deep breathing instructions
breath in deeply via nose, breath out of mouth- relaxed not forced, physiotherapist place hands on thorax (both sides), 3-4 breaths then rest, use breath hold at full inspiration (count of 3), possible sniff
what is therapeutic positioning
the placement of the patient or a body part to promote physiological and/or psychological well being. used to address more than one system. Position patients to optimise arterial oxygenation by placing most compromised area uppermost- avoid slumped position,
therapeutic positioning- problem
reduced arterial oxygen or saturations, SOB, SOBAR, SOBOE, increased work of breathing, reduced lung volume, excess sputum
what effects closing volume
increases with age, smoking, lung disease, and body postion
closing volume- other implications
FRC decreases with obesity, supine position, anaesthetic/ post- surgery which increases the risk
breathlessness/ WOB
High WOB results in breathlessness and distressed breathing pattern. increases energy use and therefore oxygen demand. position to optimise respiratory function without excess energy demand. optimise diaphragm, decrease active fixation of shoulder girdle which uses muscular contractions
therapeutic positions
sitting in chair with elbows on knee- fixing, leaning with back against wall, sitting on chair with cushions on table- sleeping position, standing and fixing on table/side, sleeping position- pillow across chest- opens up airways
