The transport and exchange systems: respiratory and cardiovascular
Nick Draper, Helen Marshall in Exercise Physiology, 2014
The tidal volume and respiratory frequency can be multiplied to calculate the minute ventilation (V̇ or V̇E), the amount of air inspired or expired each minute (V̇E = VT × Rf). Typically V̇E at rest is around 6 L·min−1 (V̇E = 0.5 L × 12). During exercise, when the demand for oxygen to supply the working muscles increases dramatically, both tidal volume and respiratory frequency can be increased to meet demand. At maximal levels tidal volume can rise to 3.0 L·breath−1, and the respiratory frequency to 60 breaths · min−1 for experienced endurance athletes such as marathon runners and cross-country skiers. Minute ventilation volumes can therefore rise from around 6 L · min−1 at rest, to 180 L · min−1 during maximal exercise. Changes in the depth and frequency of breathing are controlled by the respiratory centre.
Pulmonary Function Testing
Pudupakkam K Vedanthan, Harold S Nelson, Shripad N Agashe, PA Mahesh, Rohit Katial in Textbook of Allergy for the Clinician, 2021
TV is a measure of the amount of air a person inhales during a normal breath. In a healthy, young adult, TV is approximately 7 mL/kg of body mass (Ricard 2003). TV plays a significant role in mechanical ventilation and can be adjusted to ensure adequate ventilation without causing lung injury. Lower tidal volumes on a ventilator are preferred in patients with pre-existing lung disease or acute respiratory distress syndrome (Hallett et al. 2019). TV is also essential in calculating a patient’s minute ventilation or the volume of gas exchanged by a person’s lungs per minute. Minute ventilation is calculated by multiplying the TV and respiratory rate. During exercise, the minute ventilation increases due to physiological demands for increased oxygenation.
Personal Protective Equipment (PPE): Practical and Theoretical Considerations
Brian J. Lukey, James A. Romano, Salem Harry in Chemical Warfare Agents, 2019
Full-faced negative-pressure air-purifying respirators (gas masks) increase inspiratory resistance to a far greater extent than expiratory resistance; see Figure 17.1. With negative-pressure air-purifying respirators, as minute ventilation increases, inspiratory and expiratory resistances increase geometrically; thus, individuals may decrease their peak inspiratory and expiratory flow rates to decrease the resistance to air flow. Moreover, respirator users must increase their respiratory rate (Hodous, 1989) to meet the demands of increased minute ventilation. The need for increased minute ventilation results from an increased metabolic demand for oxygen as a consequence of the increased metabolic work needed to perform any task when wearing PPE. Negative-pressure air-purifying respirators significantly decrease the maximum voluntary ventilation of an individual and are notorious for tasking individuals with reactive airway disease (RAD), thus precipitating bronchospasm (airway narrowing) with a resultant decrease in laminar airflow and a corresponding increase in turbulent (and much less efficient) airflow. Bronchospasm (narrowing of the bronchi) may result in hypoxia (decreased oxygen) and hypercarbia (increased carbon dioxide) in the blood.
Relationship between fitness and arterial stiffness according to hypertensive state
Published in Clinical and Experimental Hypertension, 2019
Jidong Sung, Soo Jin Cho, Kyong Pyo Hong
Cardiopulmonary function test (Quinton Q4500, Cardiac Science Corp., Bothell, WA, USA) involved exercise on a treadmill using the Bruce protocol. Blood pressures were measured manually using a mercury sphygmomanometer before, and at the end of each exercise stage. During the testing, an ECG was performed, and the heart rate and oxygen consumption were recorded. Participants wore a tightly sealed breathing mask, which was connected to an airflow sensor. The respiratory gas analysis was performed with dynamic breath-by-breath measurement using the JAEGER system (VIASYS Healthcare, Hoechberg, Germany). Various respiratory parameters, including minute ventilation, oxygen uptake, and carbon dioxide output, were measured. The sampling interval (for these parameters) was 8 s in order to determine the maximal oxygen uptake. Subjects with positive findings (significant ST changes, BP drops or arrhythmias during the test) were excluded from the study. The test was otherwise terminated according to the usual criteria for exercise stress testing: 1) exhaustion; 2) reaching >90% of maximal heart rate (220 – age); 3) respiratory quotient ≥1.15; 4) plateau of oxygen consumption.
Bridging inhaled aerosol dosimetry to physiologically based pharmacokinetic modeling for toxicological assessment: nicotine delivery systems and beyond
Published in Critical Reviews in Toxicology, 2019
A. R. Kolli, A. K. Kuczaj, F. Martin, A. W. Hayes, M. C. Peitsch, J. Hoeng
A similar PBPK model, but with 4 lung regions, was developed by Sarangapani et al. with special emphasis on characterizing the transitional bronchiolar compartment for inhaled gases (Sarangapani, Teeguarden, et al. 2002). This model assumed that the air flow rate in the upper and conducting airways was equal to the respiratory minute volume and that the flow rate in the transitional and pulmonary airways was equal to the alveolar ventilation. A fraction of inhaled chemical was absorbed in the nasal cavity, conducting airways, and transitional airways. The dominant process that delivered the substance to epithelial tissues in the nose was airflow. By developing a more complete description of the regions of the lungs, it now has become possible to assess the role of airway equilibration in controlling dose-response curves for metabolism in tissues all along the airways of the RT.
Severe, transient pulmonary ventilation-perfusion mismatch in the lung after porcine high velocity projectile behind armor blunt trauma
Published in Experimental Lung Research, 2020
David Rocksén, Ulf P. Arborelius, Jenny Gustavsson, Mattias Günther
Ventilation parameters were obtained and computed by a Hamilton C2 ventilator. Physiological dead space, alveolar ventilation and CO2 slope, indicative of V′A/Q′ mismatch were computed by volumetric capnography, providing a noninvasive and continuous display of the fractional concentration or partial pressure of expired CO2 versus exhaled volume. A volumetric capnogram is divided into three phases. Phase I is the first gas exhaled that comes from the conducting airways and contains no CO2. Phase II represents gas exhaled from conducting airways mixed with gas from fast-emptying alveoli. Phase III represents gas exhaled from the alveoli, and the slope represents the changing time constant of the emptying alveoli; i.e., alveoli with a low V′A/Q′ ratio empty last and contain the highest amount of CO2.15 The physiological dead space calculation is derived from phase III.16 Physiological dead space from volumetric capnography corresponds to the Bohr equation.17 Alveolar ventilation = minute ventilation – physiological dead space.
Related Knowledge Centers
- Exhalation
- Hyperventilation
- Lung
- Inhalation
- Hypoventilation
- Tidal Volume
- Pulmonology
- Pco2
- Ventilator
- Respiratory Rate