Alveolar Ventilation, Lung Volumes, and Gas Laws Lecture 3 Flashcards
What are three determinants of volume in the lungs?
- Lung compliance
- Chest wall compliance
- Pathology of lungs or chest wall
Define residual volume and normal values?
- Amount of gas left in the lungs after a maximal forced expiration
- Determined by the force generated by the muscle of expiration and the inward elastic recoil of the lungs
- Prevents lungs from collapsing at low volumes
- RV usually about 1.5 L
Define expiratory reserve volume and normal values
- Expiratory reserve volume is the amount of gas that is expelled during a maximal forced expiration that begins at the end of normal VT
- Determined by the difference between the FRC and RV
- ERV about 1.5L
Define inspiratory reserve volume and normal values
- Inspiratory reserve volume is the amount of gas inhaled during a maximal forced inspiration beginning at the end of a normal VT
- Determined by the strength of contraction of the inspiratory muscles and inward elastic recoil of the lungs
- IRV is usally 2.5 L
Identify lung volumes which comprise the vital capacity
- Amount of air that may be maximally exhaled after a maximal inspiratory effort
- IRV + VT + ERV
Identify lung volumes which comprise the functional residual capacity
- Amount of air remaining in the lung at the end of a normal exhalation
- ERV + RV
Identify lung volumes which comprise the inspiratory capacity
- Amount of air that can be maximally inhaled at the end of a normal exhalation
- IRV + VT
Identify lung volumes which comprise the total lung capacity
- Amount of air in the lungs after a maximal inspiratory effort
- IRV + VT + ERV + RV
List seven factors in our practice that may affect lung volumes
- Height
- Position (supine, trendelenberg)
- Obstructive lung disease (Asthma, COPD)
- Restrictive lung disease (Morbid obesity, kyphoscoliosis)
- Age (Decreased closing volume with age)
- Surgery (decreased FRC, VC)
- Anesthesia (decreased FRC, VC)
Describe the universal gas law
- PV = nRT
- R = 8.3 J/Kelvin/mol
Define Avogadro’s Law and the relationship between gas molecule quality and volume
- One mole of an ideal gas occupies a volume of 22.4 L at 1 atm and 0 cel
- Equal volumes of different gasses at the same temperature and pressure contain the same number of molecules
- If the amount of gas in a container increases, volume increases
Define Boyle’s Law and the relationship of pressure to volume
- The volume of a given mass of gas is inversely proportional to the pressure, provided that the temperature remains constant
- If the pressure doubles the volume will decrease by one-half if the pressure is halved the volume will double
- P1 x V1 = P2 x V2
Define Charle’s Law and the relationship between tempearture and volume
- The volume of a given mass of an ideal gas is proportional to the absolute temperature, provided that the pressure remains constant
- Must convert to Kelvin
- Therefore, as temperature increases, volume increases as long as pressure remains constant
- V1/T1 = V2/T2
Define Gay- Lussac’s Law and the relationship between temperature and pressure
- The pressure of a given mass of an ideal gas is proportional to the absolute temperature, provided taht the volume remains constant
- PV=nRT
- Must convert to Kelvin
- As temperature increases, pressure increases, so that P1/T1 = P2/T2
- Increased temperature of a container makes molecules hit container walls harder, pushing container outward
Shapiro’s Law
- PaO2 = FiO2 x 5
Identify the effect of surgical positions on FRC and IRC

Identify the effect of residual muscle relaxation and thoracic surgery on VC and IC
- VC and IC decrease with residual NDMR and thoracic surgery (Affects ability to cough, deep breath)
Identify the effects of restrictive and obstructive lung disease on TLC, FRC, and IC, and RV
- Restrictive lung capacities are equally lower
- TLC increased in obstructive, decreased in restrictive lung disease.

List 5 methods for measuring lung volumes
- Spirometry
- Nitrogen washout
- Helium Dilution Technique
- Body plethysmography
- Fowlers method for determining anatomic deadspace
Compare and contrast FVC, FEV1, and FVC/FEV1 in obstructive and restrictive lung disease
- COPD have higher volumes
- Restrictive disease limited by expansion and also volume

List four examples of obstructive lung disease (ACCE)
- Asthma
- COPD
- Emphysema
- Chronic Bronchitis
List four examples of restrictive lung disease
- Pulmonary fibrosis
- Morbid obesity
- Chest wall disease (Kyphoscoliosis)
- Neuromuscular disease (ALS, Myasthenics, NDMR)
List five effects of anesthesia on lung volumes
- Decrease in tidal volume
- Increase in respiratory rate
- Increase in closing capacity
- Increase in shunt
- Decrease in FRC
Define anatomic deadspace as it relates to lung anatomy and ventilation/ perfusion
- Anatomic dead space is ventilation without perfusion
- VD
- Conducting zone is the anatomic dead space
- Seen in the first 16 generations, no respiratory exchange occurs here.



