Pulmonary Physiology Flashcards
A 23 year old male patient is scheduled for a pulmonary exam. His mass is 70 kg and has a tidal volume of 500 ml. What approximate amount of the tidal volume contributes to gas exchange?
350 cc
A 19 year old patient presents with a midaxillary chest wound to the left side. Their blood pressure is 140/100 while their SaO2 is <90. You suspect a collapsed lung. What change in lung pressure occurs as a consequence of the breaking the airtight seal of the pleural cavity?
The intrapleural pressure (Pip) is zero
The correct answer is C, Pip = zero. A chest would will cause air to enter the intrapleural space and normalize the pressure with the atmosphere which we regard as zero. This will cause the Ptp and Palv to go to zero. The chestwall force expanding the lungs will be lost and the lungs will collapse. Without the negative pressure of Pip the chest wall will pull away from the lungs and the force it exerts on the lungs will decrease below normal.
Ventilation effort (work) ______ when alveolar surface tension increases
Ventilation effort increases - additional muscle action will be required
The compliance of the respiratory system changes with lung volume. Close to which lung volume has the respiratory system it’s greatest compliance?
Functional residual capacity (FRC)
For a person at rest, what supplies the force for expiration?
The elastic recoil of the lung
The elastic recoil of the lungs drives passive expiration. The internal intercostals and abdominal muscles are involved in active expiration. The external intercostals are concerned with inhalation. The patient likely has COPD for which exhalation through pursed lips and a slow RR are adaptations to the increased compliance of the lungs which causes small airway collapse at higher RR.
Which lung volume cannot be measured directly by spirometry?
Residual volume
Residual volume cannot be directly measured by spirometry but the others can. You would want to know what the residual volume is so as to determine functional residual capacity. FRC will increase with COPD as residual volume increases (i.e. the FEV1/FVC will decrease). With asthma RV will not change and return to normal with proper treatment.
You have a 12 year old patient who is having an acute asthma attack. Why is the child struggling to ventilate their lungs?
An increase in airway resistance
A patient explains that breathing slow and deep is easier for them than taking normal breaths and respiration rate. Why does this reduce the work of breathing?
Deep breathing utilizes the ability of radial traction to expand the airways to overcome airway resistance
A 62 year old man with a history of hypertension presents to the emergency department following a laboratory accident where a nitrogen gas cylinder leaked nitrogen gas into a confined space, diluting the oxygen content of the air below 70 mmHg. The man was found unconscious. He is receiving supplemental oxygen and inspiratory crackles are heard in his chest. Regarding the pulmonary circulation which statement is true?
a) Blood flow is highest at lung apex in an upright Pt
b) Hypoxia causes pulmonary vasoconstriction, elevating the pulmonary BP
c) Pulmonary pressures are much lower than systemic, and pulmonary vascular resistance is higher
d) Right ventricular output is normally greater than left ventricular output
b) Hypoxia causes pulmonary vasoconstriction, elevating the pulmonary BP
Hypoxia causes vasoconstriction. Pulmonary resistance is much lower than systemic resistance. Right and left ventricular output have to match. Blood supply is greater at the base than the apex of the lung. The nitrogen gas lead reduced the partial pressure of O2 in the lab causing hypoxic vasoconstriction. Because of an existing compromise in the vascular system (hypertension) the patient also developed pulmonary edema.
D) Decreases pulmonary vascular resistance, improving oxygenation
C. Decreased (more positive) transpulmonary pressure, decreased chest wall compliance
A
B
Extrathoracic obstruction causes a diminished inspiratory curve on the P-V loop
C. Enhanced ventilation-perfusion (V/Q) matching by shifting perfusion to ventilated dorsal lung zones
Mr Haldane, age 68, is admitted to the hospital with dyspnea. He has a history of COPD. ABG results indicate PaO2 = 58 mmHg, PaCO2 = 60 mmHg and pH 7.4. A nurse has just begun to administer supplemental oxygen (FiO2 = 0.4). If a new ABG test was quickly performed after starting supplemental O2, how do you expect the PaCO2 level to have changed?
PaCO2 will be increased
In the Haldane effect O2 will force CO2 off hemoglobin. This will cause and increase in PaCO2 until the CO2 can be expelled from the lungs. This would take several ventilation cycles as each tidal volume represents approximately 13% of the end-inspiration lung volume (0.7TV + ERV + RV)
An emphysema patient with no history of elevated BMI explains to you that since they adopted the carnivore/paleo diet and eat nothing but meat they feel less out of breath. Why might this be the case?
A high fat diet has a decrease Respiratory Quotient, R, and will generate less CO2 and increase PAo2.
The value of R decrease with the proportion of fat consumed. This will reduce PvCO2 which will reduce PACO2. According to the Alveolar Gas Equation a decrease in PACO2 will increase the PAO2 which will increase the PaO2 and cause the patient to feel less dyspneic. O2 demand is linked to body mass, not diet composition. Sudden weight loss will decrease O2 demand but will not change lung volumes unless the patient was morbidly obese.
Kussmaul breathing is caused by metabolic acidosis. This will act on the peripheral receptors.
KUSSMAUL breathing is caused by metabolic acidosis. This will act on the peripheral receptors.
The central chemoreceptors are separated from arterial blood by the BBB
It will reduce pulmonary hypertension
While hiking at an altitude of 10 000 ft a hiker begins to experience dyspnea and light headedness. Which option below do you expect to represent their ABG results?
Pao2 < 60 mmHg
Paco2 < 35 mmHg
pH = 7.45
The hiker will need a Pao2 < 60 mmHg to maintain hyperventilation. The hyperventilation will drive off CO2 to less than normal which will cause blood alkalosis.
A 16 year old, from Los Angeles, California, traveled to Aspen, Colorado (8000 ft above sea level) for a football game. During the game they develop extreme dyspnea and presents at the emergency department with a RR of 25 and SaO2 of 91%. Which is an acute response to high altitude?
Increased activation of peripheral O2 receptors to drive ventilation
It takes approx. 24-48 hours for a significant increase in 2,3-BPG
Which pulmonary reflex limits tidal volume?
The Hering-Breuer reflex
The Hering-Breuer Reflex limits inspiration. This reflex needs to be suppressed to ventilate the lungs beyond regular tidal volumes
In response to hypoxemia the dorsal respiratory group receives nervous system input from which nerves to drive ventilation?
Cranial nerve IX and X
The DRG receives sensory input from CN IX (O2 receptors in carotid bodies) and CN X (O2 receptors in aortic bodies). The phrenic nerve is not involved.
A 19-month baby boy presents at the emergency room with Biot’s breathing. This pattern of breathing indicates a problem with which part of the homeostatic mechanism?
The central nervous system (cardiorespiratory center)
Biot’s breathing is due to damage to the medulla oblongata which is part of the CNS
B. Peripheral CO2 receptors
D. Peripheral O2 receptors
E. Both the dorsal and ventral respiratory groups
The apneustic center in the pons stimulates prolonged inspiration and is also activated in COPD Pt’s but is not the primary controller in response to hypoxemia/hypercapnia
A. A decrease in SaO2
Decreased stimulation of central receptors is overridden by peripheral oxygen receptor drive
Hypoventilation (alveolar)
A.
B. Idiopathic central sleep apnea
C. OSA: ramp signal continues but no airflow
D. Kaussmaul breathing: ramp signal not driven by PO2
A. Amyloidosis
B. Asbestosis
C. Sarcoidosis
C. Sarcoidosis
Hilar adenopathy, hypercalcemia, and elevated ACE levels are suggestive of sarcoidosis, a condition characterized histologically by noncaseating granulomas composed of activated macrophages and T lymphocytes. CD4+ T cells are the predominate cell in a bronchoalveolar lavage fluid in pulmonary sarcoidosis, which is a CD4+ T-cell mediated disease.
A 66-year-old man who has never smoked presents with a 2-year history of worsening dyspnea. He has no pertinent occupational or environmental exposure. A chest x-ray reveals bilateral reticulonodular opacities. Physical examination finds digital clubbing. What is the most likely cause of his signs and symptoms?
A. Organizing pneumonia
B. Pulmonary fibrosis
C. Pulmonary hypertension
B. Pulmonary fibrosis
Pulmonary fibrosis, which is characterized by pulmonary function tests showing a restrictive pattern, presents with gradual-onset progressive dyspnea, nonproductive cough, fatigue, eventual weight loss, and bilateral reticulonodular opacities on chest x-ray. Digital clubbing may be present.
A 65-year-old male long-term smoker presents with severe dyspnea and is found to have a barrel-chest. The man leans forward to breath through pursed-lips, which prolongs expiration. What is the best diagnosis?
Emphysema
Increased anteroposterior chest diameter (barrel chest), prolonged expiratory phase, distant heart sounds, and hyperinflation of the lungs on chest x-ray are signs consistent with severe emphysema. Another sign of emphysema is a patient leaning forward slightly while sitting and breathing quickly through pursed lips, which prolongs expiration.
A 24-year-old man is being evaluated for infertility, recurrent sinusitis and a productive cough. He is found to be sterile, and situs inversus of his organs is noted. What is the best diagnosis?
Kartagener syndrome
A defect involving dynein arms is the cause of Kartagener syndrome, which is a form of primary ciliary dyskinesia that is characterized by the triad of situs inversus, chronic sinusitis, and bronchiectasis.
Spirometry of COPD
- Decreased FEV1/FVC ratio
- Increased total lung capacity
- Increased residual volume
Obstructive lung diseases, such as with chronic obstructive pulmonary disease (COPD), are characterized by elevated residual volume (air trapping), elevated total lung capacity (hyperinflation), and reduced forced vital capacity.
Dx Pt w/ normal CXR, sputum eosinophils, and reduced FEV1
Asthma
Interleukin that increases IgE
IL-4
Interleukin responsible for increasing eosinphil differentiation, recruitment, and survivial.
IL-5
Cause of Karagener syndrome
Defect involving dynein arms - form of primary ciliary dyskinesia
Characteristic triad of Kartagener syndrome
- Situs invertus
- Chronic sinusitis
- Bronchiectasis
Lab findings characteristic of sarcoidosis
- Elevated serum calcium - due to secretion of 1-alpha-hydroxylase
- Elevated angiotensin-converting enzyme - normally produced by lung endothelial cells and can be used to monitor disease activity
- Increased CD4+:CD8+ cell ratio in a bronchoalveolar lavage
Increased CD4+:CD8+ cell ratio can be used to differentiate sarcoidosis from hypersensitivity pneumonitis (low CD4+:CD8+ cell ratio)
Basic clinical association of digital clubbing
Chronic hypoxia
Cyanotic heart or lung disease
Histology of emphysema
Two types of emphysema
Pulmonary fibrosis
