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# Calculation

### Respiratory calculations

Question | Answer |
---|---|

What is the formula for minute ventilation? | minute volume = respiratory rate x tidal volume |

A 36 year old female with a respiratory rate of 12 and tidal volume of 500mL. What would the minute volume be in Liters? | 6L/minute |

A 78 year old male with a history of COPD has a respiratory rate of 20 and tidal volume of 650mL. What would his minute volume be in Liters? | 13L/minute |

What is the formula for alveolar ventilation per minute? | Alveolar ventilation/min = respiratory rate x alveolar ventilation (tidal volume - dead space volume) |

20 year old male weighing 160 pounds with a respiratory rate of 12, tidal volume of 500 mL. What would his alveolar ventilation/minute be? | 4080mL/min |

A patient with a respiratory rate of 12, tidal volume of 500mL and weight is unknown. What would the alveolar ventilation per minute be? | 4200mL/min |

The ventilatory parameters for 68kg man with a respiratory rate of 20, tidal volume 480 mL, vital capacity 2.7L. What would his alveolar ventilation/min be in Liters? | 6.6L/min |

What is a normal carbon dioxide production? | 200mL/min |

What is the formula for alveolar partial pressure of carbon dioxide (PACO2)? | PACO2 = VCO2 X 0.863 divided by VA(alveolar ventilation per minute) |

If a patient's carbon dioxide production is normal and their PACO2 is 80mmHg, what would their alveolar ventilation be? | 2.15 L |

If a patient's carbon dioxide production is normal and their PACO2 is 60mmHg, what would their alveolar ventilation be? | 2.88 L |

What is the formula for dead space/tidal volume ratio? | VD/VT = PaCO2 - PeCo2/PaCo2 |

What is the patient's VD/VT if their PaCO2 is 40 mm HG with a mixed expired CO2 of 28 mm Hg? | 0.3 |

What is the patient's VD/VT if their PaCO2 is 58 mm HG with a mixed expired CO2 of 32 mm Hg? | 0.45 |

What is the formula for Boyle's law? | P1V1 = P2V2 |

What is the formula for Charles law? | V1/T1 = V2/T2 |

What is the formula for Combined Gas law? | PV = nRT |

An H cylinder is half full (full = 2200) and the patient is receiving oxygen via nasal cannula at 3L/min. How long will the cylinder last in minutes? in hours? | 1151 minutes. 19.18 hours |

An E cylinder is at 1400psi and the flow rate is 2.5L/minute. How many minutes will the tank last? | 156.8 minutes |

If a patient has smoked 2 packs of cigarettes daily for the past 35 years, what would their pack year history be? | 70 pack years |