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RTT 215 - Ch. 4 (2)

Ch. 4 - Ventilation and Ventilatory Control Tests (PFT)

what is assessment of ventilatory responses closely related to? measurement of resting ventilation
___________ _________ is usually assessed by measuring the change in ventilation that occurs with elecated CO2 or decreased O2. ventilatory response
______ ________ is the volume of gas inspired of expired during each respiratory cycle. tidal volume
the total volume of gas expired per minute is ________ __________. minute ventilation (alveolar/dead space ventilation)
where are VT, f, VE performed at? VD and VA? ventilatory response tests for CO2 & O2? bedside/PFT lab; critical care areas/PFT lab; PFT lab
how is VT measured? simple spirometry via vol displacement system or flow-sensing device
VT may also be measured from an ___________ _____ ________. integrated flow signal
what is the exchange difference termed that shows that VI and VT are greater than VE b/c at rest the body produces a slightly lower vol of CO2 than the vol of O2 consumed? what is the normal for resting pts? respiratory exchange ratio; 0.8
VT may also be estimated by means of a ___________ __________ ______________. respiratory inductive plethysmography
what is the most common way to determine respiratory frequency? measuring flow changes while pt breathes through a flow-sensing spirometer
how is the most accurate rate measured? over several minutes and divided by the # (avg)
what is it called when prolonged measurement of VT and rate with a volume-displacement spirometer requires a means of removing CO2? rebreathing system; uses CO2 absorber
what are commonly used to scrub CO2 from rebreathing system? sodasorb or baralyme
how is the VE measured? pt breathes into or out of a vol-displacement or flow-sensing spirometer for a least 1 min
what gives an accurate avg of VE? measuring expired gas vol for several mins and dividing by the time
what is the avg VT for healthy adults at rest? 400-700 ml
when does decreased VT occur? restrictive disorders; pulmonary fibrosis, neuromuscular diseases; changes in CL/RAW
what are decreases in VT and f often associated with? respiratory center depression
low VT and rate usually result in ________ ___________. alveolar hypoventilation
the VT alone is not a good indicator of the adequacy of ________ ____________. alveolar ventilation
from the equipment/noseclip alone, some pts will exhibit _______ VT than normal. larger
what is the normal RR? 10-20 breaths/min
what are indications of a change in the ventilatory status? increases/decreases in the RR
what can cause increased RR? exercise, hypoxia, hypercapnia, metabolic acidosis, decreased CL
what is decreased breathing freq common in? CNS depression and CO2 narcosis
what is the normal VE? 5-10 L/min
what is VE the sum of? VA and VD
what might a large VE (>20 L) result from? enlarged VD
what can cause increases in VE? hypoxia, hypercapnia, metabolic acidosis, anxiety, exercise
what can cause decreases in VE? hypocapnia, metabolic alkalosis, resp center depression, neuromuscular disorders
___________ _____ _____ is the lung volume that is ventilated but not perfused by pulmonary capillary blood flow. what can this be divided into? respiratory dead space (VD); anatomic dead space and alveolar dead space
what is VA? what can VA be expressed as? vol of gas that participates in gas exchange in the lungs; VA = VT - VD
how is VA calculated? VA = f(VT-VD)
what is anatomic dead space (VD) esimated from? individual's body size as 1 ml/lb of IBW
how is VD calculated? VD = PaCO2 - PeCO2/(PaCO2 x VT) (PeCO2 - mixed gas sample)
what is it called if expired volume is not measured, and only a dilution ratio can be determined? VD/VT ratio
when can the VD/VT ratio be calculated? if arterial and mixed-expired PCO2 values are known
____-_____ ____ can be used to estimate PaCO2. what is the main advantage of this method? end-tidal PCO2; no arterial blood sample
how is VD/VT calculated? (PETCO2-PECO2)/PETCO2
anatomic dead space is larger in ______ than in ______ because of differences in body size. men; women
when does VD increase? exercise; certain forms of pulm disease (bronchiectasis)
when is VD decreased? asthma or disease characterized by bronchial obstruction or mucous plugging
of greater clinical significance is the measurement of respiratory dead space, which is accomplished well by applying the _____ ________. bohr equation
what is the normal value of VD/VT in adults and the range? 0.3; 0.2-0.4 (percentage - 30% is normal)
when does VD/VT ratio decrease? exercise
as CO increases, perfusion of the alveoli at the lung apices increases; this is called ___________. recruitment
when is VD/VT increased? pulmonary embolism; pulmonary HTN
what is the VA at rest in healthy adults? what can the adequacy of VA be determind by? 4-5 L/min; ABGs
low VA associated with acute resp acidosis defines ____________. hypoventilation
excessive VA defines _____________. hyperventilation
what is ventilatory response to CO2 a measurement of? increase/decrease in VE caused by breathing concentrations of CO2 under normoxic conditions (PaO2 = 90-100)
what is ventilatory response to O2 a measurement of? increase/decrease in VE caused by breathing concentrations of CO2 under isocapnic conditions (PaCO2 = 40 mmHg)
__________ ________ is the pressure generated at the mouth during the first 100 msec of an inspiratory effort against an occluded airway. occlusion pressure
what are the 2 ways the response to INCREASING levels of CO2 can be measured? 1. open-circuit technique 2. closed-circuit or rebreathing technique
what is the open-circuit technique? (increasing levels of CO2) pt breaths various concentrations of CO2 (1-7%) until a steady state is reached
what parameters can be measured? PECO2, PaCO2, P100, VE
what is the closed-circuit technique? (increasing levels of CO2) pt rebreathes from a circuit (7% CO2 in O2) for 4 mins or until the PetCO2 >9%
what do valves and pressure taps allow the acquisition of? and a pneumotach for measuring ___. P100/PECO2 samples; VE
what is the open-circuit technique? (decreasing levels of O2) pt breaths gas mixture of O2 concentration from 12-20% to which CO2 is added to maintain PCO2 levels
what is the closed circuit technique? (decreasing levels of O2) pt rebreathes from a system similar to closed-circuit CO2, but contains CO2 scrubber
how is response to decreasing FiO2 monitored? via VE or P100 and the PO2/SpO2 via pulse ox
what is a constant level of CO2 called? isocapnia
what is the CO2 response? appropriate conc of CO2 must be used; SpO2 >95%
what is the O2 response? FiO2 appropriate to induce hypoxic response; isocapnia demonstrated by monitoring PetCO2
what is P100? pressure transducer and monitor capable of recording up to 50 cm and 50-100 mm/sec
ventilatory response should be reproducible within ___%. 10
reported P100 should be the avg of ______ or more occlusions at each level. three
the response to an increase in PaCO2 in a normal individual is a ______ increase in VE of approximately __ L/min/mmHg. what is the normal range of response? linear; 3; 1-6 L/min/mmHg PCO2
what type of pts have a blunted response to CO2? COPD
the normal response to a decrease in PO2 appears to be exponential once the PO2 has fallen to the range of ___-___. 40-60
what type of conditions falls in this category? COPD, myxedema, obesity-hypoventilation syndrome, OSA, idiopathic hypoventilation
_____ has been suggested as a measurement of ventilatory drive independent of the mechanical properties of the lungs. P100
what is the range for normal P100 values? 1.5-5 cmH2O
what does P100 increase in? hypercapnia, hypoxia
Created by: christa_2008