Tachypnoea

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Finding Sources

Reading File

Finding Sources

Reading File

Finding Sources

Here is a structured overview of tachypnoea drawn from authoritative textbook sources:

Tachypnoea

Definition

Tachypnoea is an abnormally increased respiratory rate. Normal adult rates are 12-20 breaths/min; values consistently above 20 breaths/min are considered tachypnoeic. In neonates, a resting rate >60 breaths/min warrants investigation.

Goldman-Cecil Medicine defines it as a normal physiological response to hypoxaemia or acidaemia - Goldman-Cecil Medicine International Edition, p. 2541
Tintinalli's Emergency Medicine notes that neonates with a resting rate >60 breaths/min during quiet breathing require evaluation - Tintinalli's Emergency Medicine, p. 2428

Causes

Tachypnoea is a non-specific sign. Causes are broadly grouped:

Respiratory

Condition	Mechanism
Pneumonia	Infection-driven hypoxia + SIRS
Pulmonary embolism	Dead-space physiology - PE may NOT reduce O2 saturation yet still cause tachypnoea
COPD/Asthma exacerbation	Airflow obstruction, air trapping
Pneumothorax	Reduced lung compliance
Pleural effusion	Restricted ventilation
Pulmonary oedema	Reduced gas exchange

Cardiovascular

Heart failure with pulmonary congestion
Shock (hypovolaemic, cardiogenic, distributive) - effortless tachypnoea is a key sign of shock from any cause

Metabolic

Metabolic acidosis - compensatory respiratory alkalosis (Kussmaul breathing is a subtype: deep, rapid, effortful breathing to blow off CO2)
Salicylate, methanol, ethylene glycol, paraldehyde toxicity
Hepatic disease
Sepsis / SIRS

Neurological

Brainstem lesions (midbrain lesions may cause central neurogenic hyperventilation)
Increased intracranial pressure - however, raised ICP more typically causes bradypnoea and irregular respiration
Hypoxic encephalopathy

Other

Fever / hyperthermia
Anaemia
Pain (one of the most common causes of tachypnoea without hypoxia)
Anxiety / behavioural hyperventilation
Fat embolism (classic triad: tachypnoea + fever + petechial rash in axillae)
Necrotising fasciitis and other systemic infections

Key Clinical Distinctions

Pattern	Description	Significance
Effortless tachypnoea	Fast rate, no increased work	Shock, metabolic acidosis
Deep + rapid (Kussmaul)	Hyperpnoea without ausculatory findings	Metabolic acidosis
Cheyne-Stokes	Crescendo-decrescendo + apnoea	Heart failure, bilateral hemispheric lesion
Apneustic	Prolonged inspiratory pauses	Lower pontine lesion
Biot (cluster)	Irregular bursts + apnoea	Pontine/medullary lesion

From Bradley & Daroff's Neurology: increased respiratory rate can result from hypoxia, hypercapnia, acidosis, hyperthermia, hepatic disease, toxins (especially those causing metabolic acidosis), sepsis, and pulmonary embolism - Bradley and Daroff's Neurology in Clinical Practice, p. 72

SIRS Criteria (including tachypnoea)

Tachypnoea is one of four SIRS criteria. Two or more of the following defines SIRS:

Temperature >38°C or <35°C
Heart rate >90/min
Respiratory rate >20 breaths/min (or PaCO2 <32 mmHg)
WBC >12,000/mm³ or <4,000/mm³ or >10% band forms

Rosen's Emergency Medicine, p. 1169; Schwartz's Principles of Surgery, p. 3233

Management

Management is directed at the underlying cause:

Hypoxaemia - supplemental O2, treat the respiratory cause
Metabolic acidosis - treat the cause (e.g. insulin/fluids for DKA, dialysis for renal failure)
Pain - analgesia is one of the most common fixes for tachypnoea without hypoxia
Pulmonary embolism - anticoagulation; note that normal SpO2 does NOT exclude PE in an unexplained tachypnoeic patient
Anxiety / behavioural hyperventilation - anxiolytics (diazepam 5-10 mg PO/IV, lorazepam 1-2 mg PO/IM/IV) or reassurance; breathing into a paper bag is NOT evidence-based
Shock - treat the type (fluids, vasopressors, inotropes as appropriate)
Goldman-Cecil Medicine International Edition, p. 2541

Special Considerations

Paediatric

Normal respiratory rates fall with age (inversely related to metabolic rate). Small increases in metabolic demand (e.g. fever) easily elevate the rate. Children tachypnoeic despite normal temperature need evaluation for both respiratory and non-respiratory causes.

Neonatal

Transient Tachypnoea of the Newborn (TTN) is a self-limiting condition caused by delayed clearance of fetal lung fluid. It is the most common cause of respiratory distress in term neonates. No risk of recurrence or residual pulmonary dysfunction.

Bottom line: Tachypnoea is a sensitive but non-specific sign. Its character (effortless vs. laboured, associated with hypoxia vs. not) narrows the differential considerably. Pulmonary embolism deserves special mention as it can cause tachypnoea with a normal SpO2 and should always be considered in at-risk patients with unexplained rapid breathing.

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