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what is assessment of ventilatory responses closely related to?
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___________ _________ is usually assessed by measuring the change in ventilation that occurs with elecated CO2 or decreased O2.
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RTT 215 - Ch. 4 (2)
Ch. 4 - Ventilation and Ventilatory Control Tests (PFT)
| Question | Answer |
|---|---|
| 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
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