Functional residual capacity (FRC) is 1.7 to 3.5L/kg

A capacity is the sum of two or more volumes. The total lung capacity (TLC) is total sum of the volume of gas present in all lung compartments upon maximum inspiration. It is represented mathematically as:

Total lung capacity (TLC) = Vital capacity (VC) + Residual volume (RV)

The residual volume (RV) is the volume of gas still present within the lung post maximum exhalation. It cannot be measured by spirometry, but can be using a body plethysmograph and also with the helium dilution technique.

Closing capacity (CC) is the volume of gas within the lungs at which small airways close upon expiration. It increases with age and is especially important when it surpasses the FRC as it causes changes in ventilation/perfusion mismatch and hypoxia.
In the supine position, a patient with a normal body mass index and no history of lung pathology, the CC equals the FRC at approximately 44, and at approximately 66 at standing position.

Cardiopulmonary exercise testing (CPX, CPEX, CPET) is a non-invasive testing method used to determine the performance of the heart, lungs and skeletal muscle. It measures the exercise tolerance of the patient.

The parameters measured include:

ECG and ST-segment analysis and blood pressure
Oxygen consumption (VO2)
Carbon dioxide production (VCO2)
Gas flows and volumes
Respiratory exchange ratio (RER)
Respiratory rate
Anaerobic threshold (AT)

The anaerobic threshold (AT) is an estimate of exercise ability. Any measurement below 11 ml/kg/min is usually related with an increase in mortality, especially when there is a background of myocardial ischaemia occurring during the test.

Peak VO2 <20 mL/kg with a low AT have a correlation with postoperative complications and a 30 day mortality. The CPX test is used for risk-testing patients prior to surgery to determine the appropriate postoperative care facilities. The V slope measured in CPX testing represents VO2 versus VCO2 relationship. During AT, the ramp of V slope increases, but does not provide a picture of postoperative mortality.

Since an arterial pressure transducer, and every other measuring apparatus, is prone to errors due to offset and gradient drifts, regular calibration is required to maintain accuracy of the instrument. The two-point calibration pressure values of 0 mmHg and 200 mmHg are within the physiologic range and can best compensate for the gradient drift.

Pulmonary vascular resistance (PVR) refers to the resistance to blood flow to the left atrium from the pulmonary artery.
It is derived mathematically by:

PVR = MPAP – PCWP
CO
where,
MPAP: Mean pulmonary artery pressure
PCWP: Pulmonary capillary occlusion pressure
CO: Cardiac output

For this patient:
PVR = 10 – 5 = 1mmHg
5

Remember, multiply by correction factor 80 to change units:

PVR = 1mmHg x 80 = 80 dynes·s·cm-5

Normal values range between 20-130 dynes·s·cm-5

There are different types of temperature measurement. These include:

Thermistor – this is a type of semiconductor, meaning they have greater resistance than conducting materials, but lower resistance than insulating materials. There are small beads of semiconductor material (e.g. metal oxide) which are incorporated into a Wheatstone bridge circuit. As the temperature increases, the resistance of the bead decreases exponentially

Thermocouple – Two different metals make up a thermocouple. Generally, in the form of two wires twisted, welded, or crimped together. Temperature is sensed by measuring the voltage. A potential difference is created that is proportional to the temperature at the junction (Seebeck effect)

Platinum resistance thermometers (PTR) – uses platinum for determining the temperature. The principle used is that the resistance of platinum changes with the change of temperature. The thermometer measures the temperature over the range of 200°C to1200°C. Resistance in metals show a linear increase with temperature

Tympanic thermometers – uses infrared radiation which is emitted by all living beings. It analyses the intensity and wavelength and then transduces the heat energy into a measurable electrical output

Gauge/dial thermometers – Uses coils of different metals with different co-efficient of expansion. These either tighten or relax with changes in temperature, moving a lever on a calibrated dial.

Damping is the reduction of energy in a system achieved by reducing the amplitude of oscillations. It is necessary to some degree to prevent wave overshoots.

Critical damping usually causes the system to be slow, so optimal damping is normally applied to provide a balance between speed and distortion.

Damping can cause errors if excessive (overdamping) or inadequate (Underdamping). The amount of damping in a system can be determined using the damping coefficient (D), where:

Undamped: 0
Critically damped: 1
Optimally damped: 0.64

An overdamped system will cause an artificial decrease in the systolic blood pressure, and an artificial increase in the diastolic blood pressure.

An underdamped system will cause an artificial increase in systolic blood pressure and an artificial decrease in diastolic blood pressure.

Damping can be caused by a number of factors affecting different parts of the system, including:

The tubing/cannula: The presence of air bubbles, increased blood viscosity or formation of blood clots.
The diaphragm/tubing: Increased malleability/compliance
The tubing: Presence of kinks, narrowing or too many ports of injection.

The answer here is a damped system will have a low systolic pressure, a high diastolic pressure with a normal mean pressure.

The ASA physical status classification system is a system for assessing the fitness of patients before surgery. It was last updated in October 2014.

ASA I A normal healthy patient
ASA II A patient with mild systemic disease
ASA III A patient with severe systemic disease
ASA IV A patient with severe systemic disease that is a constant threat to life
ASA V A moribund patient who is not expected to survive without the operation
ASA VI A declared brain-dead patient whose organs are being removed for donor purposes

A 20-year old woman who is 39-weeks pregnant with no other medical conditions – ASA II

A 35-year-old man with a BMI of 29 with a good exercise tolerance who smokes-ASA II

A 50-year old man with a BMI of 41 with a reduced exercise tolerance -ASA III

A 65-year old woman with a BMI of 34 with treated hypertension with no functional limitations-ASA II

A 73-year old man who has had a TIA ten-weeks ago but has a good exercise tolerance and is a non-smoker-ASA IV

Spirometry measures the total volume of air that can be forced out in one maximum breath, that is the total lung capacity (TLC), to maximal expiration, that is the residual volume (RV).

It is conducted using a spirometer which is capable of measuring lung volumes using techniques of dilution.

During spirometry, the following measurements can be determined:
Forced vital capacity (FVC)/vital capacity (VC): The maximum volume of air exhaled in one single forced breathe.
Forced expiratory volume in one second (FEV1)
FEV1/FVC ratio
Peak expiratory flow (PEF): the maximum amount of air flow exhaled in one blow.
Forced expiratory flow (mid expiratory flow): the flow at 25%, 50% and 75% of FVC
Inspiratory vital capacity (IVC): The maximum volume of air inhaled after a full total expiration.

Anatomical dead space is measured using a single breath nitrogen washout called the Fowler’s method.

Residual volume and total lung capacity are both measured using the body plethysmograph or helium dilution

The functional residual capacity is usually measured using a nitrogen washout or the helium dilution technique.

Systemic vascular resistance (SVR) is a derived value based on:

SVR = (MAP-CVP)/CO x 80

= (60 -10)/5 x 80 = 800 dynes.s.cm-5

A correction factor of 80 is needed in converting mmHg to dynes.s.cm-5
Normal values is between 700 -1600 dynes.s.cm-5

Pulmonary resistance (PVR) = (MPAP-PCWP)/CO x 80

= (10 – 5)/5 x 80 = 80 dynes.s.cm-5

To account for body size, cardiac index (CI) can be used instead of CO. CI = CO/body surface area (m2) or mL/minute/m2.
N/B: either MAP and CVP, or MPAP and PCWP are used in calculation to get dynes.s.cm-5

Metabolic equivalent (MET) measures the energy expenditure of an individual.

It is calculated mathematically by:

MET = (VO2 max/weight)/3.5 = 21/3.5 = 6 METs

Where 1 MET = 3.5 mL O2/kg/minute is utilized by the body.

Note:

1 MET Eating
Dressing
Use toilet
Walking slowly on level ground at 2-3 mph
2 METs Playing a musical instrument
Walking indoors around house
Light housework
4 METs Climbing a flight of stairs
Walking up hill
Running a short distance
Heavy housework, scrubbing floors, moving heavy furniture
Walking on level ground at 4 mph
Recreational activity, e.g. golf, bowling, dancing, tennis
6 METs Leisurely swimming
Leisurely cycling along the flat (8-10 mph)
8 METs Cycling along the flat (10-14 mph)
Basketball game
10 METs Moderate to hard swimming
Competitive football
Fast cycling (14-16 mph)