Patterns in Various Diseases

There are patterns of pulmonary function test abnormalities that are typical for most patients with a particular disease. Table 12-1 expands on Table 3-1, adding data on lung volumes, arterial blood gas values, diffusing capacity, lung compliance and resistance, the single-breath nitrogen test, and maximal respiratory pressures. It should be emphasized that a clinical diagnosis is not made from these test results alone. Rather they quantify the lung impairment and are to be interpreted in the context of the total clinical picture. For this discussion, obstructive disease is categorized into four conditions: emphysema, chronic bronchitis, chronic obstructive pulmonary disease, and asthma. Restrictive conditions are divided into those due to pulmonary parenchymal disease and extrapulmonary causes.

12A. Emphysema

Pure emphysema (such as α₁-antitrypsin deficiency) is associated with hyperinflation (increased total lung capacity [TLC]); a significant loss of lung elasticity (decreased recoil pressure at TLC and increased static compliance of the lung [PTLC and Cl_stat]); and often a substantial decrease in the diffusing capacity of the lung (DLCO, reflecting destruction of alveoli). Resting arterial tension of oxygen (PaO₂) and carbon dioxide (PaCO₂) are generally normal until the condition is far advanced. Bullae, predominantly in the lower lung fields, are typical in α₁-antitrypsin deficiency.

12B. Chronic Bronchitis

Pure chronic bronchitis is typically found in heavy cigarette smokers with a chronic productive cough and frequent respiratory infections. In contrast to emphysema, lung recoil is often normal but the PaO₂ may be low and associated with carbon dioxide retention (increased PaCO₂).

12C. Chronic Obstructive Pulmonary Disease

The lungs of most smokers in whom obstructive lung disease develops show a mixture of emphysema and chronic bronchitis. The tests reflect contributions of both disease processes. For example, hyperinflation tends to be greater than in pure chronic bronchitis, but carbon dioxide retention may not be present.

TABLE 12-1. Patterns of Pulmonary Function Tests in Disease

		Disease
Test	Units	Emphysema	Chronic Bronchitis	Chronic Obstructive Pulmonary Disease	Asthma	Restrictive
Test	Units	Emphysema	Chronic Bronchitis	Chronic Obstructive Pulmonary Disease	Asthma	Intrapul-monary	Extrapulmonary	Neuromuscular Disease	Congestive Heart Failure	Obesity
FVC	L	(N)→↓	(N)→↓	(N)→↓	↓	↓	↓	N→↓	↓	N→↓
FEV₁	L	↓	↓	↓	↓	↓	↓	N→↓	↓	N→↓
FEV₁/FVC	%	↓	↓	↓	N→↓	N→↑	N	N	N→↓	N
FEF _25-75	L/s	↓	↓	↓	↓	N→↓	↓	N→↓	↓	N→↓
PEF	L/min	↓	↓	↓	↓	N→↓	↓	N→↓	↓	N
MW	L/min	↓	↓	↓	↓	N→↓	↓	N→↓	↓	N→↓
FEF ₅₀	L/s	↓	↓	↓	↓	N→↓	↓	N→↓	↓	N→↓
Slope of FV curve		↓	↓	↓	N→↓	↑	N→↓	N	N→↓	N
TLC	L	↑	N→↓	↑	N→↓	↓	↓	N→↓	↓	N→↓
RV	L	↑	↑	↑	↑	↓	↓	N→↑	N→↓	↓→N→↑
RV /TLC	%	↑	↑	↑	↑	N	N→↓	N→↓	N→↓	↓→N→↑
DLCO	mL/mm Hg/min	↓	N→↓	N→↓	↑→N→↓	↓	N	N→↓	↓	N→↑
DL/VA	mL/mm Hg/min/L	↓	N→↓	N→↓	↑→N→↓	N→↓	N	N	↓	N→↓
PaO ₂	torr^a	N→↓	↓	N→↓	N→↓	↓	N	N→↓	N→↓	N→↓
SaO₂	%	N→↓	↓	N→↓	N→↓	↓	N	N→↓	N→↓	N→↓
PaCO₂	torr↓^a	N→↑	↑	N→↑	N→↓	N→↓	N	N→↑	N→↓	N
pH	-log[H⁺]	N→↓	N→↓	N→↓	N→↑	N→↑	N	N→↓	N→↑	N
Raw	cm H₂O/L/s	↑	↑	↑	↑	↓→N→↑	N→↑	N→↑	N→↑	N→↑
CL_stat	L/cm H₂O	↑	N	N→↑	N→↑	↓	N	N	N→↓	N
CL_dyn	L/cm H₂O	↑	N→↓	N→↓	N→↓	↓	N	N	N→↓	N→↓
PTLC	cm H₂O	↑	N	N→↓	↓	N→↑	N	N	N→↑	N
Phase III	% N₂/L	↑	↑	↑	↑	N→↑	N	N	N→↑	N
Phase IV	% vital capacity	A	↑→A	↑→A	↑→A	N→↑	N	N	N→↑	N→↑
P Emax	cm H₂O	N→↓	↑	↓→N→↑	N	N→↓	N→↓	N→↓↓	N	N
PImax	cm H₂O	↓	N	N→↓	N	N→↑	N→↑	N→↓↓	N	N→↓
^atorr, equivalent to mm Hg. →, to; ↑, increased; ↓, decreased; A, often absent; CL_dyn, dynamic compliance of the lung; CL_stat, static compliance of the lung; DLCO, diffusing capacity of carbon monoxide; DL/VA, diffusing capacity of the lung/alveolar volume; FEF _25-75, forced expiratory flow rate over the middle 50% of the FVC ; FEF ₅₀, forced expiratory flow after 50% of the FVC has been exhaled; FEV₁, forced expiratory volume in 1 second; FV , flow-volume; FVC , forced expiratory vital capacity; MVV , maximal voluntary ventilation; N, normal; (N), occasionally normal; PaCO₂, arterial carbon dioxide tension; PaO ₂, arterial oxygen tension; PEF , peak expiratory flow; PEmax, maximal expiratory pressure; PImax , maximal inspiratory pressure; PTLC , lung recoil pressure at TLC ; Raw , airway resistance; RV , residual volume; SaO₂, arterial oxygen saturation; TLC , total lung capacity.

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