L11 Challenges to normal respiration Flashcards
What is the effect of exercise on the respiratory system?
The basal oxygen requirement increases several fold. Maximal oxygen consumption is dependent on how fit the individual is. Arterial blood gases are changed up to an oxygen consumption of 3 L/min at sea level.
In severe exercise, ventilation may be further increased by lactic acid from muscles lowering blood pH and the release of potassium ions from exercising muscles. Thus increased ventilation may lower pCO2 as CO2 is blown off. The difference is made up by anaerobic respiration which produces lactic acid. The point anaerobic starts is known as the anaerobic threshold.
What factors play a role in regulating ventilation during exercise?
- Feedback from joint receptors
- The anticipation of expertise
- Increased venous return and cardiac output
- Raised core temperature
- Increasing sensitivity of peripheral chemoreceptors to oscillations in arterial pH and pCO2.
What is the response to high altitude?
- Increased 2,3-BPG
- Hyperventilation and respiratory alkalosis
- Polycythaemia - this is slow to develop
- Bicarbonate secretion from CSF and kidneys
- Diuresis, hyponatraemia
- Increased cardiac output
- Increased tolerance for physical exercise
What is the partial pressure of oxygen in the alveolus?
At sea level PO2 = 21kPa
Inspired oxygen that reaches alveolus = 0.21* (101 - 6.3) = 19.887
6.3 = SVP of water vapour
In the alveolus = 0.21(101.3-6.3 - 5.3/0.8 )
= 0.2195 - 6.6
= 19.9 - 6.6
= 13.3
At what altitude will you start to experience the effect of hypoxia?
Hypoxia occurs within a few minutes if the cabin pressure altitude rises to between 5,000-6,000 m (about 16,000 - 20,000 ft).
What is the response to hypoxia at altitude?
Peripheral chemoreceptors detect changes in carbon dioxide and so proton concentration. The aortic and carotid bodies are able to detect this hypoxemia. This therefore stimulates hyperventilation to remove carbon dioxide lowering the proton concentration in the blood and CSF. In a few hours the active transport of bicarbonate out of the CSF brings the pH of the CSF under control, however metabolic compensation takes time. Deoxyhaemoglobin is more alkaline and so adds to the alkalosis. Increases bicarbonate secretion leads to diuresis. Dehydration may occur. Water and electrolyte imbalance such as potassium deficiency and sodium retention could accompany altitude sickness. After which The hypocapnia causes hyperventilation to stop and so the carbon dioxide concentration to raise. Altitude sickness therefore is brought about due to the fluctuations between respiratory alkalosis and acidosis.
What are the effects of hypoxia on the body?
- Confusion
- Nausea
- Raised Intercranial pressure
- Cranial oedema - hypocapnia from hyperventilation decreases cerebral blood flow giving rise to cerebral dysfunction and cerebral oedema may occur also.
- Pulmonary oedema - due to pulmonary vasoconstriction
- Right heart failure
- Pulmonary hypertension
What is altitude sickness? What are the symptoms?
Altitude sickness acute illness caused by exposure to low oxygen partial pressures at a high altitude. The symptoms are:
- Nausea
- Headaches
- Confusion
- Loss of appetite
- Difficulty sleeping and performing activities
Acute mountain sickness is common and can be lethal. Acclimatisation to altitudes involves several physiological changes to help reduce hypoxia. Many people who die on summits, die on the way back as they cannot get down fast enough.
What is Cheyne Stroke respiration?
An abnormal pattern ofbreathing characterised by progressively deeper, and sometimes faster,breathingfollowed by a gradual decrease that results in a temporary stop inbreathingcalled an apnoea (it is also seen in elderly patient before they stop breathing and die).
What is the effect of breath holding on the respiratory system?
When holding your breath the partial pressure of carbon dioxide rises to a constant point termed the breaking point. At this point respiratory chemoreceptors force the individual to take a breath. Hyperventilation prior will reduce the partial pressure of carbon dioxide, but not increase that of oxygen, and so will extend the breath holding time. This demonstrates the dominance of the carbon dioxide drive in ventilation. Mental determination is another factor helping to increase the time.
Prolonged breath holding can be achieved by hyperventilating prior as it means that the partial pressure of carbon dioxide will be able to rise further before it sets of the chemoreceptors. This however means the individual is in a state of hypoxia for much longer, reaching dangerous levels. This is a problem in people holding their breath diving as it carriers the risk of fainting underwater.
What is the effect of free diving on pressure in the respiratory system?
The pressure exerted by the water increases rapidly as greater depths are During breath-holding, the volume in the lungs decreases and so the pressure increases. At 1.6m, the pressure is so great the inspiratory muscles cannot overcome the external water pressure, so that for some people it becomes impossible to breath. reached.
Why is helium-oxygen used in deep diving? What percentage of oxygen his used?
Helium is used to progressively wash out the nitrogen. Only 2% oxygen is required due to the high pressures at very low depths. The effects of the nitrogen otherwise include:
- Nitrogen narcosis
- Nitrogen is an anaesthetic at high concentrations leading to a loss of consciousness
- Nitrogen has a very high tissue solubility and so it will move into the tissues and on ascent will leave bubbles in the brain, joints and lungs . This is as on ascent, where the pressure drops, the nitrogen cannot be exhaled fast enough and so accumulates in tissues as bubbles. Oxygen however does not form bubbles as the oxygen not exhaled is used up in respiration. Th bubbles are also known as ‘bends’ or ‘chokes’, which compromise respiration.
What is the diving reflex?
The diving reflex, also known as the diving response and mammalian diving reflex, is a set of physiological responses to immersion that overrides the basic homeostatic reflexes, and is found in all air-breathing vertebrates and neonates.
This reflex involves apnea (loss of drive to breathe), reflex bradycardia, and peripheral vasoconstriction. During the diving reflex, the infant’s heart rate decreases by an average of 20%.
What is retrolental fibroplasia?
Fibrosis tissue behind the eye which causes irreversible blindness. This is a concern in neonates with a low respiratory system and are treated with high oxygen concentrations. A neonate is used to getting oxygen from a relatively hypoxic environment and so even normal levels are potentially dangerous. This is as they get their blood from the placenta which has already been around the mothers circulation and so oxygen concentrations are lower.
What is hyperoxia? What is the effect?
High oxygen concentrations can lead to seizures and the generation of damaging free radicals such as those used by neutrophils kill bacteria and fungi by oxygen free radicals. This punches small holes in membranes.
