What Is Tidal Volume?

Tidal volume (TV) refers to the volume of air inhaled or exhaled each time during calm breathing. It is related to age, gender, volume surface, breathing habits, and body metabolism. The set tidal volume usually refers to the inspiratory volume. The tidal volume setting is not constant and should be adjusted based on the patient's blood gas analysis. Under normal circumstances: adults: 8-10ml / kg, children: 6-10ml / kg.

Tidal Volume

Tidal volume (TV) refers to the volume of air inhaled or exhaled each time during calm breathing. It is related to age, gender, volume surface, breathing habits, and body metabolism. The set tidal volume usually refers to the inspiratory volume. The tidal volume setting is not constant and should be based on the patient's

Breathing times = 20 breaths / minute, then one breath every 3 seconds. If the inspiratory time is 1 second, then the exhaling time is 2 seconds, then the inspiratory ratio is 1: 2; .

The number of breaths is not related to the tidal volume, and it is related to the inhalation and exhalation ratio. Tidal volume = inspiratory time * air supply flow rate. The longer the inspiratory time, the greater the tidal volume.

Tidal volume indication

Severe hypoventilation 2. Severe ventilatory disorders 3. Neuromuscular paralysis 4. After cardiac surgery 5. Increased intracranial pressure 6. Neonatal tetanus Use of large doses of sedatives requires respiratory support 7. Asphyxia, CPR 9. Any reason Breathing stops or is about to stop.

Ventilator contraindications

Undrained pneumothorax, massive pleural effusion, bullae

Relative contraindication

Moderate or above active hemoptysis, severe pulmonary edema, bronchopleural fistula, myocardial infarction or severe coronary insufficiency, hypovolemic shock before blood volume is not replenished

Tidal Volume Type Performance

1. Constant volume ventilator: The change from inhaling to exhaling is based on the pre-adjusted tidal volume.

2. Constant pressure ventilator: Inhalation to exhalation is switched according to the preset pressure peak. (Different from the pressure limitation, the pressure limitation is that the airway pressure is not switched after the airway pressure reaches a certain value)

3. Timed ventilator: The conversion from inspiration to expiration is determined by the time parameter (inhalation time). Since the 1980s, there have been timing, pressure-limiting, and constant-current ventilators. This ventilator retains the characteristics of timing type and constant volume type, which can ensure the ventilation when the airway resistance increases and the lung compliance decreases, and has the advantage of not easily causing barotrauma due to the limited pressure peak. Time, expiratory time, inhalation ratio, inhalation platform size, and oxygen concentration can be adjusted. At the same time, IMV (intermittent command ventilation), CPAP (continuous positive airway pressure) and other ventilation methods are available, which are the most suitable Ventilator for infants, newborns, premature infants.

Tidal volume working parameters

Four major parameters: tidal volume, pressure, flow, and time (including breathing frequency and breathing ratio).

Tidal volume: The tidal volume must be greater than a person's physiological tidal volume. The physiological tidal volume is 6 ~ 10 ml / kg, while the ventilator's tidal output can reach 10 ~ 15 ml / kg, which is often 1 ~ 2 times. Further adjustments should be made according to chest undulations, auscultation of both lungs, reference pressure table, and blood gas analysis.