L9 - Respiratory Physiology 1 Flashcards
describe what the different parts of the respiratory system are for (look at diagrams to label diff parts in lecture slides)
- get O2 in, CO2 out - ventilation + lung mechanics
2+4. Get O2 and CO2 across - gas exchange - Get O2 and CO2 around
describe how ventilation works (Boyle’s law)
Change in lung volume causes a change in pressure
- Inspiration: volume of the lungs decreases - Palv drops driving airflow into the lung
- Expiration: volume of the lungs decreases - Palv rises driving airflow out of the lung
Ventilation: exchange of air between the atmosphere and alveoli
Air flow = pressure difference/resistance
Change in pressure = alveolar pressure - atmospheric pressure
describe the transmural pressures involved in ventilation
No muscles attached to the lung surface - How does a change in lung dimensions occur?
1. pressure difference between inside and outside of lung: transpulmonary pressure: Ptp = Palv - Pip (intramural pressure)
2. how much lungs can expand for a given change in Ptp depends on lung stretchability/lung compliance
Ptp increases lungs expand
Ptp decreases lungs recoil
what actions have to happen for both inspiration an expiration?
Inspiration:
Phrenic nerves and intercostal nerves send AP’s that result in the diaphragm and intercostals contracting
- Thorax expands
- Ptp becomes more subatmospheric
- increase in transpulminory pressire
- lungs expand
- Palv becomes sub atmospheric
- air flows into alveoli
Expiration:
Diaphragm and inspiratory intercostals stop contracting
- chest wall recoils inwards
- Ptp moves back toward pre inspiration value
- transpulminory pressure moves back towards preinspiration value
- lungs - recoild toward pre inspiration size
- air in alveoli becomes compressed
- Palv becomes greater then Pat
- air flows out of lungs
describe lung mechanics of ventilation
Physical properties and interactions of the lungs, diaphragm and chest wall during breathing
1. lung compliance - ability to add air and remove air from inside the lungs
a. mechanic to overcome the surface tension that exists between air and fluid coating the alveoli
b. how much lungs can expand for a given change in Ptp - stretchability of the lung
2. airway resistance (clinical situations, asthma, bronchitis - COPD, OSA)
3. explain the different lung volumes used to clinically assess pulmonary function
describe lung compliance and how that affects ventilation
- lung compliance - determines the ability of a ling to add and remove air
- stretchability of the lung (how stiff/flexible the lung tissue is)
- determines how much the lungs can expand (change in V) for a given change in Ptp (change in Ptp)
- contributing factor -> fluid (water) covers lung surfaces
water molecules on alveoli are more attracted to eachothe than to air creates a force called surface tension, creates tendency for alveoli to collapse
- high surface tension = low compliance
Surfactants:
- produce by type II aleveolar cells
- forms a layer between water and air
- reduces interaction between H2O molecules
- reduces surface tension
Low surface tension = high compliance
Compliance = change in lung volume / change in pressure
what are two diseases/issues that are to do with lung compliance and ventilation
Small increases in compliance
Lungs can expand easier - less stiff
Easier to breathe - less work of breathing
Extensive increase in lung compliance
- Emphysema (smoking or mine workers lung). Destruction of alveoli, creates alveoli with large air spaces. The lungs have little elastic recoil and tend to remain inflated. Expiratory muscle activity is required to deflate the lungs.
Small decrease in compliance
Lung expansion is more difficult - stiffer
More difficult to breathe - more work to breathe
Extensive decrease in lung compliance:
- pulmonary fibrosis (restrictive lung disease). the alveolar wall is stiffer, inspiration is difficult (inspiratory muscles have to work harder). breathing shallowly and at higher frequency to reduce work of breathing.
describe ventilation and airway resistance
Air flow = pressure difference/resistance
- airway resistance - how easy air can move in and out of the lungs. dependence mostly on radius of airway tubes (radii). in normal situation airway resistance is low
- physical factors (Ptp, elastic connective tissue, mucus) and neuroendocrine factors
- parasympathetic nerves to airways smooth muscle causes bronchoconstriction
- sympathetic nerves to away smooth muscle causes bronchodilation
- pathologies that affect airway resistance: asthma, COPD; chronic bronchitis)
how does asthma affect dental practice
Episodes of airway smooth muscle contraction - due to chronic inflammation - increases airway resistance
Causes by: allergies, viral infections, environmental factors
Exacerbation of asthma in dental practice:
- anxiety and stress for dental appointment
- allergies to dental materials
- avoid certain narcotics/barbiurates for sedation
- anti-inflammatory drugs
- bronchodilators (relax airways, via inhalers) - stimulating adrenergic receptors (sympathetic) and blocking muscarinic receptors (parasympathetic)
describe how bronchitis )(COPD) affects dental practice
Excessive mucus production in bronchi with inflammatory changes in smaller airways - increases airway resistance
Caused by: smoking chronic inhalation of environmental dust particles, infections
Characterised by: coughing, excess sputum and phlegm
Relevance: COPD can result in mouth bleeding, which causes further drying of the gingival tissues around the upper anterior teeth and gingivitis
Could consider:
- semi-supine or upright chair postion
- oximeter on finger might be needed to measure O2 saturation
encourage smoking cessation
what are two important measures of pulmonary function? and how will you know whether it is an restrictive or obstructive disease? - also list volumes and capacities from graph or know what they mean
Capacities are sum of two or more volumes
Two important measures of pulmonary function
- VC (volume of air expired with maximum effort, capacity)
- FEV1 (forced expiratory volume in 1 sec, resistance)
Healthy individuals expire 80% of VC in 1 sec
Restrictive lung disease -> VC reduced - but FEV1 nomal
Obstructive lung disease (Asthma, COPD) -> VC normal but FEV1 <80%
what is dead space? and what are the equations for minute ventilation and alevolar ventilation?
Minute ventilation (total air moved) vs. alveolar ventilation (total air used for gas exchange)
Minute ventilation (mL/min) = tidal volume (mL/breath) x respiratory rate (breaths/min)
Alveolar ventilation (mL/min) = (tidal volume (mL/breath) - dead space (ml/breath)) x respiratory rate (breaths/min)
Dead space - volume of inspired air that does not take part in gas exchange
describe obstructive sleep apnoea (what it is, dental issues and how it is caused in children)
Obstructive sleep apnoea - narrowing of airways around nose and throat during sleep - difficulty or pauses in breathing, with a loud gasps or snorts
Increase airway resistance - O2 saturations might be reduced, and sleep can be disrupted
Dental isses: breathing through mouth causes dry mouth (saliva evaporation) - lack of saliva makes it more acidic 0 reduced tooth enamel - increase plaque, mouth sores gum disease
OSA in children is causes mostly by large tonsil and/or adenoids (narrower dent alveolar width, increased overset, reduced overbite). oversight/obese children have higher risk of OSA
- children with OSA associated with a poorer oral-health related quality of life and a greater child oral health impact profile score
what are some treatments in adults for obstructive sleep apnoea, and what are some dental issues with CPAP
Treatment in adults:
- laser surgery, to widen the soft palate and uvula
- weight loss
- CPAP (continuous positive airway pressure). wearing a small mask over the nose during sleep creating increased airway pressure to prevent collapse of upper airways during inspiration, seems obtrusive, enormous improvement to sleep quality, and many associated symptoms resolve
Dental issues with CPAP:
- tooth movements - loose teeth
- jaw shifting
- dry mouth (still mouth breathing, improper use of CPAP - tooth decay)
