Chapter 5 Normal Values and Formulas

Normal WBC count

4.5-11.5 ×10³/µL

Normal RBC count (Male)

4.60-6.00 ×10⁶/µL

Normal RBC count (Female)

4.00-5.40 ×10⁶/µL

Hemoglobin (Male)

14.0-18.0 g/dL

Hemoglobin (Female)

12.0-15.0 g/dL

Hematocrit (Male)

40-54%

Hematocrit (Female)

35-49%

Segmented neutrophils

40-75%

Bands

0-6%

Eosinophils

0-6%

Basophils

0-1%

Lymphocytes

20-45%

Monocytes

2-10%

Normal Platelet Count

150,000-400,000/mm³

Normal pH

7.35-7.45 (average 7.40)

Normal PaCO₂

35-45 mmHg

Normal PaO₂

85-100 mmHg

Normal SaO₂

≥97%

Normal HCO₃⁻

22-26 mEq/L

Normal Base Excess

-2 to +2 mEq/L

Normal SpO₂

≥97%

Normal SvO₂

75%

Preterm pH (1-5 hrs)

7.29-7.37

Term pH (5 hrs)

7.31-7.37

Preterm PaCO₂ (1-5 hrs)

39-56 mmHg

Term PaO₂ (5 hrs)

62-86 mmHg

Neonatal SaO₂

90-95% depending on hours/days

Normal Adult BP

90-140 / 60-90 mmHg

Normal Heart Rate

60-100 bpm

Normal PR Interval

0.12-0.20 sec

Normal QRS Duration

<0.10 sec

Normal Cardiac Output

4-8 L/min

Normal Cardiac Index

2.5-4.0 L/min/m²

Normal CVP

2-6 mmHg

Normal Pulmonary Artery Pressure

20-35 / 5-15 mmHg

Normal PCWP

5-10 mmHg (abnormal >18)

Normal SVR

900-1400 dyn·sec/cm⁵

Normal PVR

110-250 dyn·sec/cm⁵

Adult PTT

25-39 sec

Adult PT

12-15 sec

Albumin

2.9-5.5 mg/dL

BUN

8-23 mg/dL

Calcium

8.6-10.5 mmol/dL

Ionized Calcium

2.25-2.75 mEq/L

Chloride

98-107 mEq/L

Creatinine

0.7-1.3 mg/dL

Glucose (fasting)

<100 mg/dL

Potassium

3.5-5.0 mEq/L

Sodium

135-145 mEq/L

Tidal Volume (VT)

5-8 mL/kg PBW; critical <4-5 or <300 mL

Respiratory Rate

12-20 breaths/min; critical >30-35

RSBI

>105 indicates poor ventilation (no PS/CPAP)

Dead Space Ratio (VD/VT)

0.25-0.40; critical >0.60

Minute Ventilation (VE)

5-6 L/min; critical >10 L/min

Vital Capacity (VC)

65-75 mL/kg; critical <10-15 mL/kg

Maximum Inspiratory Pressure (MIP)

-80 to -100 cmH₂O; critical 0 to -20 cmH₂O

Infant HR

90-170 bpm

Infant RR

30-60 breaths/min

Toddler HR

80-160 bpm

Preschooler HR

80-120 bpm

School-Age HR

70-110 bpm

Adult HR

60-100 bpm

Adult RR

12-20 breaths/min

Normal Adult BP

<120/80 mmHg

Alveolar Air Equation (full formula)

PAO₂ = (Pb − PH₂O)FiO₂ − (PaCO₂ × 1.25)

Alternate Alveolar Air Equation

PAO₂ = (Pb − PH₂O) − PaCO₂ / RQ

Shortcut Alveolar Air Equation

PAO₂ ≈ 7(FiO₂) − (PaCO₂ + 10)

Normal PAO₂

About 100 mmHg

What is the Alveolar Air Equation used for?

To calculate PAO₂ and determine the A-a gradient.

Alveolar Ventilation equation

V̇A = (VT − VD) × f

Normal V̇A

4-6 L/min

Dead Space Volume formula

VD = VT − VA, or VD = VE − VA (f)

Normal VD

About 1/3 of tidal volume

Alveolar Volume equation

VA = VT − VD

Normal VA fraction

About 2/3 of tidal volume

A-a Gradient formula

A-a Gradient = PAO₂ − PaO₂

What does an elevated A-a gradient indicate?

Increased shunt or diffusion defect

Normal A-a gradient

<10 cmH₂O

Minute Ventilation formula

VE = VT × f. Normal 5-7 L/min

VE calculation for desired PaCO₂

VE(new) = VE(actual) × PaCO₂(actual) / PaCO₂(desired)

New respiratory rate formula

RR(new) = RR(current) × PaCO₂(actual) / PaCO₂(desired)

New VT formula

VT(new) = VT(current) × PaCO₂(actual) / PaCO₂(desired)

Formula for VT using flow

VT = Flow × I-time (convert L/min → L/sec)

Total flow formula (Venturi Mask)

Add parts of air/O₂ ratio × LPM

I:E using VE and flow

I:E = VE : (Flow − VE)

Flow needed using I:E

Flow = (I + E) × VE

Inspiratory time formula

TI = Seconds per breath / (I + E)

I:E when inspiratory & expiratory times known

I:E = I-time / E-time

I:E ratio using % inspiratory time

I:E = I% : (1 − I%)

VD/VT formula

VD/VT = (PaCO₂ − PECO₂) / PaCO₂.

Normal VD/VT

0.3 (30%)

Predicted PaO₂ formula

PaO₂ = 110 − (½ age)

RAW formula

RAW = (PIP − Pplat) / Flow

Static compliance

Cstat = VT / (Pplat − PEEP). Normal 60-100 mL/cmH₂O

Dynamic compliance

Cdyn = VT / (PIP − PEEP)

Cylinder duration formula

PSI × Cylinder factor / Flow (H = 3.14, E = 0.28)

Liquid Oxygen (LOX) conversion

1 lb LOX = 344 L O₂ gas

Liquid Oxygen (LOX) duration formula

(Pounds × 344) / Flow

Relative humidity formula

RH = Absolute humidity / Capacity × 100; At 37°C = 47 mmHg vapor pressure, capacity = 44 mg/L.

Dalton's Law

Total P = P₁ + P₂ + P₃