tidal volume

Examples of tidal volume in the following topics:

• Breathing Patterns

  • During normal breathing, the volume of air cycled through inhalation and exhalation is called tidal volume (VT), and is the amount of air exchanged in a single breath.
  • Tidal volume multiplied by the respiratory rate is minute ventilation, which is one of the most important indicators of lung function.
  • It describes dramatically decreased tidal volume and sometimes increased respiratory rate, leading to a sensation of breathlessness.
  • These terms all describe an altered breathing pattern through increased or decreased (or stopped) tidal volume or respiratory rate.
  • The normal respiratory rate refers to the cyclical inhalation and exhalation of tidal volume (VT).

• Inspiration

  • Pressure and volume are inversely related to eachother, so the drop in pressure inside the lung increases the volume of air inside the lung by drawing outside air into the lung.
  • As the volume of air inside the lung increases, the lung pushes back against the expanded pleural cavity as a result of the drop in intrapleural pressure (pressure inside the pleural cavity).
  • Eventually, the pressure inside the lung becomes less negative as the volume inside the lung increases, and when pressure and volume stabilize, the air movement stops, inspiration ends, and expiration (exhalation) will begin.
  • Deeper breaths have higher tidal volumes and require a greater drop in intrapleural compared to shallower breaths.
  • Therefore they should not be used as the primary  mechanism of inhalation, because they take in much less air compared to the diaphragm resulting in a much lower tidal volume.

• Neural Mechanisms (Respiratory Center)

  • It increases tidal volume.
  • It decreases tidal volume.

• Pressure Changes During Pulmonary Ventilation

  • The volume of air can refer to tidal volume (the amount inhaled in an average breath) or something more specific, such as the volume of dead space in the airways.
  • It can be defined as $VE=TidalVolume*BreathsPerMinute$
  • It is defined as $VA=(Tidal Volume-Dead Space Volume)* Respiratory Rate$
  • It is defined as $VD=DeadSpaceVolume*Respiratory Rate$.
  • This is most apparent in changes of the dead space volume.

• Lung Capacity and Volume

  • Lung volumes and capacities refer to phases of the respiratory cycle; lung volumes are directly measured while capacities are inferred.
  • It is also the sum of tidal volume and the inspiratory and expiratory reserve volumes, which capture the differences between normal breathing and maximal breathing.
  • Other important lung volumes related to lung capacity are residual volume (RV) and total lung capacity (TLC).
  • FEV1: The volume of air exhaled in one second of forced expiration.
  • Differentiate among tidal volume, inspiratory reserve volume, expiratory reserve volume, and vital capacity of lungs

• Functional Anatomy of the Respiratory System

  • It can be defined as tidal volume (the volume of air inhaled in a single breath) times the amount of breaths in a minute.
  • It is defined as tidal volume minus dead space (the space in the lungs where gas exchange does not occur) times the respiratory rate.
  • It is defined as volume of dead space times the respiratory rate.
  • When the diaphragm contracts, the rib cage expands and the contents of the abdomen are moved downward, resulting in a larger thoracic volume and negative pressure (with respect to atmospheric pressure) inside the thorax.

• Proprioceptor Regulation of Breathing

  • The lungs are a highly elastic organ capable of expanding to a much larger volume during inflation.
  • While the volume of the lungs is proportional to the pressure of the pleural cavity as it expands and contracts during breathing, there is a risk of over-inflation of the lungs if inspiration becomes too deep for too long.
  • When the lungs are inflated to their maximum volume during inspiration, the pulmonary stretch receptors send an action potential signal to the medulla and pons in the brain through the vagus nerve.
  • However, the reflex may determine the breathing rate and depth in newborns and in adult humans when tidal volume is more than 1 L, such as when exercising.

• Physical Characteristics and Volume

  • The average blood volume in adult is five liters.
  • The average adult has a blood volume of roughly five liters (1.3 gal).
  • Blood volume is a regulated variable that is directly proportional to blood pressure through the output of the heart.
  • A healthy adult can lose almost 20% of blood volume (1 L) before the first symptom, restlessness, begins, and 40% of volume (2 L) before hypovolemic shock sets in.
  • Conversely, higher than normal blood volume may cause hypertension, heart failure, and aneurysms.

• Plasma and Blood Volume Expanders

  • A volume expander is a type of intravenous therapy that provides fluid replacement for the circulatory system.
  • A volume expander is a type of intravenous therapy that provides blood volume for the circulatory system.
  • There are two main types of volume expanders: crystalloids and colloids.
  • There are also a few other volume expanders that may be used in certain situations:
  • Saline can be used to increase blood volume when a blood transfusion is not possible.

• Regulation of Urine Concentration and Volume

  • In a way, urine volume regulation is part of homeostasis, in that it directly regulates blood volume, because greater amounts of urine will reduce the volume of waters in blood.
  • An anti-diruetic is a substance that decreases urine volume, and ADH is the primary example of it within the body.
  • ADH is a hormone secreted from the posterior pituitary gland in response to increased plasma osmolarity (i.e., increased ion concentration in the blood), which is generally due to an increased concentration of ions relative to the volume of plasma, or decreased plasma volume.
  • This effect causes increased water reabsorption and retention and decreases the volume of urine produced relative to its ion content.
  • A diuretic is any substance that has the opposite effect of ADH— they increase urine volume, decrease urine osmolarity, lead to an increased plasma osmolarity, and often reduced blood volume.