Oxygen Therapy

Question 1

A simple face mask delivers oxygen at a flow rate of:

A. 1–4 L/min
B. 2–6 L/min
C. 5–10 L/min
D. 10–15 L/min

Answer 1

C

Question 2

The minimum flow rate for a simple face mask to avoid CO₂ rebreathing is:

A. 2 L/min
B. 5 L/min
C. 8 L/min
D. 10 L/min

Answer 2

B

Question 3

A high concentration reservoir mask typically delivers:

A. 24–28% oxygen
B. 28–35% oxygen
C. 35–50% oxygen
D. 55–90% oxygen

Answer 3

D

Question 4

The reservoir bag on a high concentration mask must:

A. Be removed during use
B. Be humidified
C. Remain inflated
D. Be half deflated

Answer 4

C

Question 5

A Venturi mask is described as a:

A. Variable performance device
B. Fixed performance device
C. High-flow rebreathing device
D. Low-flow humidified system

Answer 5

B

Question 6

Increasing the oxygen flow rate on a Venturi mask:

A. Increases oxygen concentration
B. Decreases oxygen concentration
C. Does not change oxygen concentration
D. Causes CO₂ retention

Answer 6

C

Question 7

Venturi masks are particularly suitable for patients with:

A. Severe trauma
B. Type I respiratory failure
C. Raised carbon dioxide levels
D. Post-cardiac arrest

Answer 7

C

Question 8

Short term oxygen therapy (STOT) is mainly prescribed for:

A. Stable COPD patients
B. Hypoxaemic patients on hospital discharge
C. Cluster headaches
D. Pulmonary hypertension only

Answer 8

B

Question 9

The most effective humidification system for depositing sterile droplets in the bronchial tree is:

A. Cold bubble humidifier
B. Heated humidifier
C. Nasal cannula humidifier
D. Aerosol system

Answer 9

D

Question 10

In critically ill patients, first responders should initially use:

A. 2 L nasal cannula
B. 28% Venturi mask
C. Reservoir mask at 15 L/min
D. Simple face mask at 5 L/min

Answer 10

C

Question 11

Hypoxaemia is defined as:

A. PaO₂ > 10 kPa
B. PaCO₂ > 6 kPa
C. SaO₂ > 95%
D. PaO₂ < 8 kPa

Answer 11

D

Question 12

Type II respiratory failure is characterised by:

A. Low PaO₂ only
B. High PaCO₂
C. Low bicarbonate
D. Normal blood gases

Answer 12

B

Question 13

Normal PaCO₂ is:

A. 2–4 kPa
B. 4.7–6 kPa
C. 6–8 kPa
D. 8–10 kPa

Answer 13

B

Question 14

Exposure to high oxygen concentrations may cause:

A. Increased cardiac index
B. Bronchodilation
C. Absorption atelectasis
D. Improved coronary blood flow

Answer 14

C

Question 15

In COPD patients with chronic hypercapnia, high oxygen levels may:

A. Increase hypoxic drive
B. Improve ventilation automatically
C. Cause oxygen-induced hypercapnia
D. Reduce PaCO₂ immediately

Answer 15

C

Question 16

Oxygen concentrators for LTOT are generally used for flow rates:

A. Above 10 L/min
B. 6–8 L/min
C. 4 L/min or less
D. Exactly 15 L/min

Answer 16

C

Question 17

Long term oxygen therapy (LTOT) in stable COPD is indicated when resting PaO₂ is:

A. ≤7.3 kPa
B. ≤9 kPa
C. ≤10 kPa
D. ≤12 kPa

Answer 17

A

Question 18

What is the primary goal of oxygen therapy?
A) To reduce carbon dioxide levels
B) To increase alveolar oxygen concentration
C) To treat hyperventilation
D) To prevent bronchospasm

Answer 18

B

Question 19

Hypoxaemia is generally defined as PaO₂ less than:
A) 70 mmHg
B) 90 mmHg
C) 60 mmHg
D) 50 mmHg

Answer 19

C

Question 20

Type 1 respiratory failure is characterized by:
A) PaO₂ > 8 kPa
B) PaCO₂ > 6.1 kPa
C) PaO₂ < 8 kPa, PaCO₂ 4.6–6.1 kPa
D) PaCO₂ < 4.6 kPa

Answer 20

C

Question 21

When a patient using a Venturi mask develops tachypnoea (RR >30/min), what adjustment should be made?
A)Increase oxygen flow by 50%
B)Switch to a non-rebreather mask immediately
C)Decrease oxygen flow by 50% to avoid hypercapnia
D)Make no change — Venturi masks are fixed-dose devices and flow does not affect concentration

Answer 21

A

Question 22

Which humidification system is considered most effective due to its capacity for deposition of sterile water droplets within the bronchial tree?
A)Cold water bubble-through system
B)Aerosol system
C)Heated humidification unit
D)Passive heat-moisture exchanger

Answer 22

B

Question 23

A critically ill COPD patient with known CO₂ retention arrives in A&E. What is the correct initial oxygen therapy before blood gases are available?
A)28% Venturi mask and await blood gases before escalating
B)Withhold oxygen entirely until blood gases are obtained
C)Reservoir mask at 15L/min, same as any critically ill patient
D)Nasal cannulae at 1–2L/min to avoid precipitating hypercapnia

Answer 23

C

Question 24

Which statement about the high concentration (non-rebreather) mask is correct?
A)It can deliver oxygen concentrations of 35–60%
B)Humidification is recommended to prevent mucosal drying during use
C)The reservoir bag does not need to be inflated prior to application
D)Side vents and a one-way valve prevent rebreathing of exhaled CO₂

Answer 24

D

Question 25

Continuous oxygen therapy (COT) is prescribed when a patient requires oxygen: A)For more than 15 hours per day B)Only during sleep (nocturnal use) C)Exclusively during exertional activities D)For more than 8 hours per day

Answer 25

A

Question 26

Which of the following correctly describes Type II respiratory failure? A)PaO₂ < 8kPa with PaCO₂ within the normal range of 4.6–6.1kPa B)PaCO₂ > 6.1kPa, with or without associated hypoxaemia C)PaO₂ < 8kPa with concurrent PaCO₂ < 4.7kPa (hypocapnia) D)SpO₂ < 88% on room air with a normal PaCO₂

Answer 26

B

Question 27

After stopping supplemental oxygen in a stable patient, what criterion confirms successful weaning? A)SpO₂ remains stable for 5 minutes after oxygen is stopped B)SpO₂ remains stable for 30 minutes after oxygen is stopped C)SpO₂ remains stable for 1 hour after oxygen is stopped D)Two consecutive observations with SpO₂ in range while still on low-dose oxygen

Answer 27

C

Question 28

Which is a recognised limitation of the simple/variable performance face mask? A)It cannot be used at flow rates above 10L/min B)It delivers a fixed, predictable oxygen concentration regardless of breathing pattern C)It is approved for long-term domiciliary oxygen therapy D)Flow rates below 5L/min carry a risk of carbon dioxide rebreathing

Answer 28

D

Question 29

Which of the following correctly defines hypoxaemia? A)PaO₂ < 60mmHg (8kPa) or arterial SaO₂ < 90% B)PaO₂ < 80mmHg or SaO₂ < 94% C)PaO₂ < 8kPa and SaO₂ < 88% (both criteria must be met) D)PaCO₂ > 6.1kPa with an associated low SpO₂ on pulse oximetry

Answer 29

A

Question 30

Approximately how much oxygen is carried bound to haemoglobin in 100mL of normal blood? A)0.3mL (the same as in plasma) B)20mL C)4mL (one molecule per haem unit) D)15mL (only at full saturation)

Answer 30

B

Question 31

Regarding enclosure systems for oxygen delivery, which statement is correct? A)Oxygen hoods prevent a fixed FiO₂ by design, making concentration unreliable B)Incubators deliver a precisely fixed FiO₂ making them the most reliable enclosure C)Oxygen tents and incubators have variable FiO₂ delivery as they may leak D)Enclosure systems are appropriate for adolescent patients with severe respiratory failure

Answer 31

C

Question 32

Which of the following is a recognised adverse effect of exposure to high concentrations of oxygen? A)Decreased systemic vascular resistance B)Increased cardiac index C)Bronchodilation reducing work of breathing D)Absorption atelectasis, occurring even at FiO₂ as low as 30–50%

Answer 32

D

Question 33

What is the standard maximum flow rate for nasal cannulae in routine clinical use? A)4L/min (up to 6L/min in some settings) B)6L/min in all clinical settings without restriction C)8L/min before a face mask is required D)2L/min, as higher flows consistently cause mucosal damage

Answer 33

A

Question 34

After any change in oxygen therapy, how long should SpO₂ be continuously monitored to confirm the target saturation has been achieved? A)2 minutes B)5 minutes C)10 minutes D)15 minutes

Answer 34

B

Question 35

Which mechanism best explains oxygen-induced hypercapnia in COPD patients? A)Oxygen directly stimulates central chemoreceptors, causing apnoea B)Increased FiO₂ causes bronchoconstriction, reducing alveolar ventilation C)Reduced hypoxic drive for ventilation and reduced hypoxic pulmonary vasoconstriction, worsening V/Q mismatch D)High-flow oxygen causes absorption atelectasis, the sole cause of CO₂ retention

Answer 35

C

Question 36

How does PaO₂ change with age, and what is the primary physiological explanation? A)PaO₂ increases with age as functional residual capacity rises, improving gas exchange B)PaO₂ remains constant; it is SaO₂ that declines as the O₂-Hb curve shifts C)PaO₂ decreases due to progressive reduction in functional residual capacity D)PaO₂ decreases as closing volume increases with age, reducing the number of alveoli available for gas exchange

Answer 36

D

Question 37

A patient with stable COPD has a resting PaO₂ of 7.6kPa with peripheral oedema and a haematocrit of 57%. According to BTS guidelines, what is the correct management? A)LTOT is not indicated as PaO₂ exceeds the primary threshold of 7.3kPa B)LTOT should be ordered as PaO₂ ≤8kPa with evidence of peripheral oedema and polycythaemia (haematocrit ≥55%) C)Nocturnal oxygen therapy only, as the patient does not meet criteria for full LTOT D)Ambulatory oxygen therapy assessment should be offered as the first step before considering LTOT

Answer 37

B

Question 38

What is the correct initial flow rate when commencing LTOT, and how should it be confirmed as effective? A)Start at 2L/min and titrate until SpO₂ ≥94%; confirm with ABG showing PaO₂ ≥10kPa B)Start at 1L/min and titrate up in 1L/min increments until SpO₂ >90%; confirm with ABG showing PaO₂ ≥8kPa (60mmHg) at rest C)Start at 2L/min fixed rate — no titration is needed as flow is standardised across conditions D)Start at 1L/min; titrate until SpO₂ ≥94%; no ABG required if pulse oximetry confirms target

Answer 38

B

Question 39

Which statement correctly describes the role of short burst oxygen therapy (SBOT) in COPD management according to BTS guidelines? A)SBOT should be offered prior to exercise to prevent exertional desaturation in hypoxaemic COPD patients B)SBOT is recommended on discharge from hospital for non-hypoxaemic patients with severe COPD to reduce readmission C)SBOT should not be ordered prior to or following exercise in hypoxaemic or normoxic COPD patients D)SBOT is an appropriate alternative to LTOT when patients have difficulty complying with 15 hours per day

Answer 39

C

Question 40

Regarding ambulatory oxygen therapy (AOT), which patient group should NOT routinely be offered an AOT assessment? A)LTOT patients who are mobile outdoors and wish to leave their home B)Patients attending a pulmonary rehabilitation programme where formal assessment confirms improved exercise endurance C)Patients not eligible for LTOT who experience desaturation on exertion D)LTOT patients completing a formal exercise programme following assessment demonstrating benefit

Answer 40

C

Question 41

According to the BTS guideline, which scenario requires an immediate clinical assessment rather than routine monitoring? A)SpO₂ remains stable but the flow rate has been increased by 1L/min B)SpO₂ falls by ≥3% or drops below the patient's target saturation range C)SpO₂ is at the upper limit of the prescribed target range on reassessment D)A nurse changes the oxygen delivery device during a drug round

Answer 41

B

Question 42

High flow nasal oxygen (HFN) differs from standard reservoir mask treatment in which key respect? A)HFN can be used in patients with hypercapnic respiratory failure whereas reservoir masks cannot B)HFN delivers a fixed FiO₂ regardless of patient minute volume, unlike the reservoir mask C)HFN may be used as an alternative to reservoir mask in acute respiratory failure without hypercapnia, and is mostly used in ICU/HDU settings D)HFN delivers a lower peak FiO₂ than the reservoir mask and is preferred for mild hypoxaemia

Answer 42

C

Question 43

A patient with cystic fibrosis has a resting PaO₂ of 8.5kPa with no evidence of peripheral oedema, polycythaemia, or pulmonary hypertension. What is the correct course of action regarding LTOT? A)LTOT should be ordered immediately as CF patients have an unconditionally lower threshold B)LTOT is not indicated; the PaO₂ exceeds the 7.3kPa primary threshold and secondary criteria are absent C)Nocturnal oxygen therapy is the correct first-line prescription before considering LTOT D)Ambulatory oxygen assessment should be the initial step in all CF patients with PaO₂ below 10kPa

Answer 43

B

Question 44

Which of the following statements about nasal cannulae is most accurate? A)They deliver a fixed FiO₂ independent of the patient's breathing pattern and minute volume B)They are contraindicated in patients who are mouth-breathers as no oxygen is delivered C)At 1–6L/min they provide approximately 24–50% FiO₂, but actual delivery depends on flow rate, minute volume, and breathing pattern D)They should be replaced by a simple face mask whenever a patient requires more than 2L/min

Answer 44

C

Question 45

Regarding humidified oxygen, which of the following clinical scenarios is a recognised indication? A)All patients receiving nasal cannulae at flows above 2L/min to prevent mucosal drying B)Post-cardiac arrest patients to optimise oxygen delivery to ischaemic myocardium C)Patients with a tracheostomy, bronchiectasis, or cystic fibrosis, and those on high flow whisper CPAP D)Any patient prescribed a simple face mask for more than four hours continuously

Answer 45

C

Question 46

What is the minimum recommended daily duration of LTOT, and what additional benefit may be gained with prolonged use? A)Minimum 10 hours/day; 15 hours may provide additional benefit B)Minimum 12 hours/day; use beyond 16 hours provides no further clinical benefit C)Minimum 15 hours/day; up to 24 hours per day may provide additional benefit D)Minimum 8 hours/day (nocturnal use only); daytime use is optional and patient-led

Answer 46

C

Question 47

Which statement about palliative oxygen therapy (POT) according to BTS guidelines is correct? A)POT should be prescribed for all cancer patients experiencing breathlessness regardless of oxygen saturation B)POT is recommended as first-line treatment for breathlessness in end-stage cardiac disease even if SpO₂ is normal C)Non-hypoxaemic cancer or end-stage cardiorespiratory patients with intractable breathlessness should not receive POT; opiates and non-pharmacological treatments such as fan therapy should be assessed instead D)POT is only indicated when SpO₂ falls below 85% in the palliative setting

Answer 47

C

Question 48

When reading an oxygen flow meter, which instruction ensures an accurate flow rate is set? A)The top of the ball should sit on the line of the desired flow rate B)The bottom of the ball should sit on the line of the desired flow rate C)The centre of the ball should be aligned with the line of the desired flow rate D)Any part of the ball overlapping the line is acceptable, as the range is ±0.5L/min

Answer 48

C

Question 49

According to BTS guidelines on weaning, what should happen to the oxygen delivery device once a patient can maintain saturation within or above the target range? A)The device should be removed immediately and the patient discharged from oxygen monitoring B)Oxygen should be discontinued but the delivery device should be left in place in case of future deterioration and to guide EWS/NEWS scoring C)The flow rate should be halved and the patient reassessed at 24 hours before removing the device D)Oxygen should be replaced with air via the same device for a further 4 hours before full discontinuation

Answer 49

B

Question 50

What adjustment to LTOT flow rate is recommended for non-hypercapnic patients during sleep? A)Flow rate should be decreased by 1L/min during sleep to avoid nocturnal hyperoxia B)Flow rate should be increased by 1L/min during sleep in the absence of contraindications C)No change is required — the daytime flow rate is maintained through the night D)CPAP should replace LTOT during sleep in all non-hypercapnic patients

Answer 50

B

Question 51

A simple face mask must be run at a minimum flow rate of 5L/min. What is the clinical rationale for this minimum? A)Flows below 5L/min deliver an FiO₂ below 28%, making the mask ineffective compared to nasal cannulae B)Below 5L/min the mask cannot maintain a seal against the face, causing significant air entrainment C)Flows below 5L/min are insufficient to flush exhaled CO₂ from the mask, causing CO₂ accumulation and increased resistance to breathing D)Below 5L/min the oxygen supply becomes pulsatile, causing variable FiO₂ delivery on each breath

Answer 51

C

Question 52

Regarding LTOT follow-up, what is the schedule recommended by BTS guidelines after LTOT is initiated? A)Follow-up at 6 weeks, then annually, conducted by the patient's GP B)Follow-up at 3 months (including blood gases and flow rate review), then at 6–12 month intervals, conducted by a specialist home oxygen assessment team C)Follow-up at 1 month, then 6-monthly, with blood gases only required if the patient reports worsening symptoms D)Annual follow-up only, unless the patient is admitted to hospital with an acute exacerbation

Answer 52

B