Frequency-tidal volume

Opioids are potent respiratory depressants, causing a dose-dependent decrease in respiratory frequency, tidal volume and minute ventilation and increased arterial partial pressure of carbon dioxide (PaC02) (Carvey 1998). Opioids depress chemosensors in the brainstem, decreasing the ventilatory response to carbon dioxide. Opioids also depress rhythmicity in the dorsal respiratory group in the nucleus tractus solitarius, attenuating the respiratory cycle. Opioids, however, do not diminish hypoxic ventilatory drive. Significant elevations in Paco2 can result in increased ICP after opioid administration. 

Change in the functional status of ventilation is determined by measuring respiratory patterns which should include, at a minimum, the endpoints respiratory rate (frequency), tidal volume (depth), and minute volume (or minute ventilation or expired minute volume). By monitoring the frequency and depth of the pumping apparatus, the effects of drugs on total pulmonary ventilation (i.e., respiratory stimulation or depression) can be established. 

TABLE 5.6 Effect of Dead Space Volume, Tidal Volume, and Breathing Frequency on Alveolar >fentllation at a Fixed Minute Ventilation (V = 58.0 Umin). Modified from Chemiack. ... 

Most lung deposition models are based on the influence of particle size on aerosol deposition. Breathing parameters, such as breathing frequency and tidal volume, play a key role in lung deposition [15]. Table 2 shows the breathing parameters for healthy male volunteers subjected to various levels of exercise on a bicycle ergometer [16], There are known differences in these parameters based on gender, age, and disease... 

Total ventilation. The total ventilation (minute volume) is the volume of air that enters the lungs per minute. It is determined by tidal volume and breathing frequency ... 

Total ventilation = tidal volume x breathing frequency = 500 ml/breath x 12 breaths/min = 6000 ml /min... 

With an average tidal volume of 500 ml/breath and breathing frequency of 12 breaths/min, 6000 ml or 61 of air move in and out of the lungs per minute. These values apply to conditions of normal, quiet breathing tidal volume and breathing frequency increase substantially during exercise. 

Frequency of action potential generation and duration of this electrical activity to the motor neurons, and therefore the muscles of inspiration and expiration, which determines the depth of breathing, or the tidal volume (as the frequency and duration of stimulation increase, the tidal volume increases)... 

During exercise, the increase in minute ventilation results from increases in tidal volume and breathing frequency. Initially, the increase in tidal volume is greater than the increase in breathing frequency. As discussed earlier in this chapter, increases in tidal volume increase alveolar ventilation more effectively. Subsequently, however, as metabolic acidosis develops, the increase in breathing frequency predominates. 

In general, slow, deep inhalation followed by a period of breath holding increases the deposition of aerosols in the peripheral parts of the lungs, whereas rapid inhalation increases the deposition in the oropharynx and in the large central airways. Thus, the frequency of respiration (the flow velocity) and the depth of breath (tidal volume) influence the pattern of pulmonary penetration and deposition of inhaled aerosols. Therefore, an aerosol of ideal size will penetrate deeply into the respiratory tract and the lungs only when the aerosols are inhaled in the correct manner (Sackner, 1978 and Sackner et al., 1975). 

Tidal volume and respiratory frequency are used with the anatomic dimensions to model airflow patterns in the respiratory tract. 

Increased lung flow resistance in 2 animals at 0.26 ppm effect in all at 0.5 ppm 30% increase in frequency of breathing 20% decrease in tidal volume... 

Mechanism of Action A central nervous system stimulant that directly stimulates the respiratorycenterinthemedullaorindirectlybyeffectsonthecarotid. TfterflpeMtIc Effect Increases pulmonary ventilation by increasing resting minute ventilation, tidal volume, respiratory frequency, and inspiratory neuromuscular drive, and enhances the ventilatory response to carbon dioxide. 

Breathing maneuver (tidal volume, frequency) and duration... 

Male Fischer 344/N rats were exposed via the nose only for 6 h to concentrations of vinylidene fluoride ranging from 27 to 16 000 ppm [71-42 000 mg/m. Tidal volume (mean, 1.51 mL/brcath) and respiratory frequency (mean, 132 breaths/min) were not influenced by exposure concentration. Steady-state blood levels of vinylidene fluoride increased linearly with increasing exposure concentration up to 16 000 ppm. Vinylidene fluoride tissue/air partition coefficients were determined experimentally to be 0.07, 0.18, 0.8,10, and 0.29 for water, blood, liver, fat and muscle, respectively. Previously published detenninations (Filser Bolt, 1979) for the maximum velocity of metabolism in mg/li/kg) and Michaelis Menten constant (K in mg/L) are 0.07 and 0.13, respectively. Time to reach steady-state blood levels of vinylidene fluoride was less than 15 min for all concentrations. After cessation of exposure, blood levels of vinylidene fluoride decreased to 10% of steady-state levels within 1 h. Simulation of the metabolism of vinylidene fluoride mdicated that although blood levels of vinylidene fluoride increased linearly with increasing exposure concentration, the amount of vinylidene fluoride metabolized per 6-h exposure period approached a maximum at about 2000 ppm [5240 mg/m vinylidene fluoride (Medinsky et al., 1988). 

MDI delivery efficiency depends on the patient s inspiratory flow rate, breathing pattern and hand-mouth coordination. Increases in tidal volume and decreases in respiratory frequency enhance the peripheral deposition in the lung. Most patients need to be trained to use the MDI correctly, as up to 70% of patients fail to do so [26, 30]. 

The animals are intubated via cannulation of the trachea with an 18-gage metal tube and ventilated (Harvard pump ventilator) at a tidal volume of 0.4 mL, frequency 120 breaths/min and positive end-expiratory pressure 2.5-3.0 cm H20. 

Regional deposition is dependent on the aerodynamic properties of the particles, usually described in terms of the aerodynamic particle diameter, airway dimensions, and such respiratory characteristics as flow rate, breathing frequency, and tidal volume. 

See Annexe B (ICRP 1994) for data from which these reference values were derived. Vj = Tidal volume, B = ventilation rate, /r = respiration frequency. 

Pattern Tidal volume (ml) Breathing frequency (1/min) Nebulization... 

Sulfur dioxide is rapidly absorbed in the nasopharynx of humans. Humans exposed to 5 ppm of the gas showed increased respiratory frequency and decreased tidal volume. Similar to observations made with animals, human exposure to S02 alters the mode of respiration, as demonstrated by increased frequency, decreased tidal volume, and lowered respiratory and expiration flow rates. Synergism and elevated airway resistance with S02 and aerosols of water and saline have been demonstrated. 

---